Effects of clay after an aflatoxin challenge on aflatoxin clearance,milk production,and metabolism of Holstein cows

Oral supplementation of clay to dairy cattle has been reported to reduce toxicity of aflatoxin (AF) in contaminated feed. The objective of this study was to determine the effects of 3 concentrations of dietary clay supplementation in response to an AF challenge. Ten multiparous rumen-cannulated Holstein cows [body weight (mean ± SD) = 669 ± 20 kg and 146 ± 69 d in milk], were assigned to 1 of 5 treatments in a randomized replicated 5 × 5 Latin square design balanced to measure carryover effects. Periods (21 d) were divided in an adaptation phase (d 1 to 14) and a measurement phase (d 15 to 21). From d 15 to 17, cows received an AF challenge. The challenge consisted of 100 μg of aflatoxin B₁ (AFB₁)/kg of dietary dry matter intake (DMI). The material was fitted into 10-mL gelatin capsules and administered into the rumen through a rumen-cannula based on the average DMI obtained on d 12 to 14. Treatments were no clay plus an AF challenge (POS); 3 different concentrations of clay (0.5, 1, or 2% of dietary DMI) plus an AF challenge; and a control consisting of no clay and no AF challenge (C). Statistical analysis was performed using the MIXED procedure of SAS (SAS Institute Inc., Cary, NC). Two contrasts, CONT1 (POS vs. C) and CONT2 (POS vs. the average of 0.5, 1, and 2% clay), were compared along with the linear and quadratic treatment effects (POS, 0.5%, 1%, 2%). Cows supplemented with clay had lower AF excretion in milk as aflatoxin M₁ (AFM₁; 0.5% = 20.83 μg/d, 1% = 22.82 μg/d, and 2% = 16.51 μg/d) and AF transfer from rumen fluid to milk (AFM_1; 0.5% = 1.01%, 1% = 0.98%, and 2% = 0.74%) compared with cows in POS (AFM₁ = 27.81 μg/d and AF transfer = 1.37%, CONT2). Similarly, concentrations of AFM₁ in milk (0.5% = 0.35 μg/kg, 1% = 0.30 μg/kg, 2% = 0.25 μg/kg), AFB₁ in feces (0.5% = 1.79 μg/g, 1% = 1.52 μg/kg, 2% = 1.48 μg/kg), and AFB₁ in rumen fluid (0.5% = 0.05 μg/kg, 1% = 0.02 μg/kg, 2% = 0.02 μg/kg) were reduced in cows fed clay compared with POS (0.43 μg/kg, 2.78 μg/kg, and 0.10 μg/kg, respectively, CONT2). Cows supplemented with clay tended to have lower 3.5% fat-corrected milk [0.5% = 38.2 kg, 1% = 39.3 kg, 2% = 38.4 kg, standard error of the mean (SEM) = 1.8] than cows in POS (41.3 kg; SEM = 1.8; CONT2). Plasma superoxide dismutase (SOD) concentration tended to be lower for cows fed clay in the diet (0.5% = 2.16 U/mL, 1% = 1.90 U/mL, 2% = 2.3 U/mL; SEM = 0.3) than for cows in POS (2.72 U/mL; CONT2). Additionally, when cows were exposed to AF without clay in the diet, plasma concentrations of aspartate aminotransferase (AST) decreased from 84.23 (C) to 79.17 (POS) and glutamate dehydrogenase (GLDH) decreased from 91.02 (C) to 75.81 (POS). In conclusion, oral supplementation of clay reduced the transfer of AF from the rumen to milk and feces.     

Aluminosilicate clay improves production responses and reduces inflammation during an aflatoxin challenge in lactating Holstein cows

Mitigation strategies are vital in minimizing the health and economic risks associated with dairy cattle exposure to aflatoxin (AF). The objective of this study was to determine the effects of a commercially available aluminosilicate clay in a lactation diet on production responses, blood chemistry, and liver inflammatory markers of multiparous lactating Holstein cows during an AF challenge. Sixteen multiparous lactating Holstein cows [body weight (mean ± SD) = 758 ± 76 kg; days in milk = 157 ± 43 d] were assigned to 1 of 4 treatments in a replicated 4 × 4 Latin square design with 21-d periods: no adsorbent and no AF challenge (CON), no adsorbent and an AF challenge (POS), 113 g of aluminosilicate clay top-dressed on the total mixed ration (adsorbent; FloMatrix, PMI Nutritional Additives, Arden Hills, MN) with an AF challenge (F4), or 227 g of adsorbent with an AF challenge (F8). The challenge consisted of 100 μg of AFB₁/kg of dietary dry matter intake administered orally. For each period, milk was sampled 3× daily from d 14 to 21; blood, feces, and urine were sampled on d 14, 18, and 21; and liver samples were taken on d 18. Liver tissue was assessed for gene expression and histological hepatocyte inflammation. Statistical analysis was preformed using the MIXED and GLIMMIX procedures of SAS (SAS Institute Inc., Cary, NC). Fat-corrected milk (POS = 37.2, F4 = 39.2, and F8 = 38.9 kg/d) increased as concentration of adsorbent in the diet increased. There was a decrease in milk AFM₁ concentration at d 18 as concentration of adsorbent in the diet increased (POS = 0.33, F4 = 0.32, and F8 = 0.27 µg/kg). There was a decrease in AFM₁ concentration in urine (POS = 2.10, F4 = 1.89, and F8 = 1.78 µg/kg) and AFB₁ concentration in feces (POS = 4.68, F4 = 3.44, and F8 = 3.17 µg/kg) as concentration of adsorbent in the diet increased. Cows in CON had greater concentrations of serum cholesterol (202 mg/dL) and plasma superoxide dismutase (2.8 U/mL) compared with cows in POS (196 mg/dL and 2.6 U/mL, respectively). Plasma glutamate dehydrogenase increased as concentration of adsorbent in the diet increased (POS = 37.8, F4 = 39.3, and F8 = 39.1 U/L). The expression of NFKB1 was greater in the liver of cows in POS (0.78) compared with cows in CON (0.70). The expression of MTOR was greater in the liver of cows in CON (1.19) compared with cows in POS (0.96). When compared with cows in CON, cows in POS had greater odds ratio for hepatocyte inflammation (odds ratio = 5.14). In conclusion, the adsorbent used in this study had a positive effect on milk production and hepatocyte inflammation and reduced AF transfer.     

Effects of recombinant bovine interleukin-8 (rbIL-8) treatment on health,metabolism, and lactation performance in Holstein cattle IV: Insulin resistance,dry matter intake,and blood parameters

We have shown in 2 independent studies that cows who received recombinant bovine interleukin-8 (rbIL-8) administered intrauterinely shortly after parturition have a significant and long-lasting increase in milk yield. In the present study, we hypothesized that the increased milk production associated with rbIL-8 treatment is a consequence of increased postpartum dry matter intake (DMI) and orchestrated homeorhetic changes that prioritize milk production. Cows were enrolled into 1 of 3 treatment groups: those assigned to the control group (CTR; n = 70) received an intrauterine (IU) administration of 500 mL of Dulbecco's phosphate-buffered saline (DPBS) solution and 1 mL of DPBS solution intravenously (IV; jugular vein), those assigned to the rbIL-8 IV group (rbIL8-IV, n = 70) received an IV injection of 167 μg of rbIL-8 and 500 mL of DPBS solution IU, and cows assigned to the rbIL-8 IU group (rbIL8-IU, n = 70) received an IU administration with 1,195 μg of rbIL-8 diluted in 499.5 mL of DPBS solution and 1 mL of DPBS solution IV. Animals were housed in a tiestall from calving to 30 d in milk (DIM) to measure DMI. Blood samples were collected daily from calving to 7 DIM and weekly until 28 DIM. Insulin resistance was evaluated using an intravenous glucose tolerance test and intravenous insulin challenge test (IVICT) in a subgroup of cows (n = 20/treatment) at 10 and 11 DIM, respectively. Additionally, liver biopsy samples were taken at 14 DIM from the same subgroup of cows to measure triglyceride levels and cell proliferation and apoptosis. Cows treated with rbIL8-IU produced more milk (CTR = 36.9 ± 1.5; rbIL8-IU = 38.5 ± 1.5; rbIL8-IV = 36.6 ± 1.5 kg/d), energy-corrected milk (CTR = 42.9 ± 0.9; rbIL8-IU = 46.1 ± 0.8; rbIL8-IV = 43.7 ± 0.9 kg/d), and fat-corrected milk (CTR = 44.3 ± 0.9; rbIL8-IU = 47.8 ± 0.9; rbIL8-IV = 45.2 ± 0.9 kg/d) yields when compared with CTR cows, and no differences were observed between rbIL8-IV and CTR cows. The administration of rbIL8-IU significantly increased DMI compared with CTR (CTR = 18.8 ± 0.3; rbIL8-IU = 19.9 ± 0.3; rbIL8-IV = 19.3 ± 0.3 kg/d). Recombinant bIL-8 treatment did not affect glucose, insulin, or fatty acids (i.e., IVICT only) concentrations or their area under the curve in response to an intravenous glucose tolerance test and IVICT when compared with CTR. Moreover, rbIL-8 treatment administered IU or IV increased liver triglyceride levels. Additionally, cows treated with rbIL8-IU tended to have lower odds of developing hyperketonemia (odds ratio = 0.46, 95% confidence interval: 0.19 to 1.10), lower odds of clinical ketosis and displaced abomasum combined (odds ratio = 0.17, 95% confidence interval: 0.03 to 0.89), and lower odds of diseases combined (odds ratio = 0.43, 95% confidence interval: 0.21 to 0.86) when compared with CTR. We conclude that the administration of rbIL8-IU increases DMI, milk production, fat-corrected milk, and energy-corrected milk while improving overall health during the postpartum period. This study supports the use of rbIL-8 administered IU shortly after calving to improve health and production responses in lactating cows.     

The effect of calcareous marine algae,with or without marine magnesium oxide,and sodium bicarbonate on rumen pH and milk production in mid-lactation dairy cows

Two experiments were carried out to evaluate different dietary buffers and their influence on (1) rumen pH in dairy cows and (2) milk production in dairy cows. The supplements included were calcareous marine algae (CMA; Lithothamnion calcareum), with or without marine magnesium oxide (MM; precipitated magnesia derived from seawater), and sodium bicarbonate (SB). Dietary treatments in experiment 1 consisted of the control [32.9% starch and sugar, and 19.9% neutral detergent fiber from forage per kg of dry matter (DM)] including no dietary buffer (CON); the control plus 0.45% DM CMA (CMA); the control plus 0.45% DM CMA and 0.11% DM MM (CMA+MM); the control plus 0.9% DM SB (SB). Diets were formulated to a dry matter intake (DMI) of 18 kg per cow/d. Dietary treatments in experiment 2 also consisted of CON (28.3% starch and sugar, and 23% neutral detergent fiber from forage per kg of DM), CMA, CMA+MM, and SB and were formulated to achieve identical intakes of experimental ingredients (80 g of CMA, 80 g of CMA plus 20 g MM, and 160 g of SB per cow/d) with a DMI of 22.6 kg per cow/d. Experiment 1 used 4 rumen-cannulated dairy cows in a 4 × 4 Latin square design. Rumen pH was measured over five 2-h periods, following feeding, using rumen pH probes. In experiment 2, 52 multiparous and 4 primiparous cows (62.7 ± 3.4 d in milk) were assigned to 4 experimental treatments for 80 d. Both CMA treatments maintained a greater mean rumen pH than the CON during 4 of the 5 periods following feeding and the CON had a greater number of hours below rumen pH 5.5 compared with all other treatments. Dry matter intakes tended to be higher on the SB compared with CON. The CMA treatment increased the production of milk fat and protein yield (kg/d) compared with all other treatments. Both CMA and CMA+MM increased milk fat yield compared with CON but were similar to each other and SB. Protein yield was highest in the CMA treatment compared with CON, CMA+MM, and SB. All 3 buffer treatments increased milk fat concentration compared with CON but did not differ from each other. The SB treatment reduced milk protein concentration and milk production efficiency, energy-corrected milk per kilogram of DMI. Results indicate that the addition of CMA can benefit milk fat and protein production when included in diets based on typical feedstuffs of the northern European region. The use of CMA when compared with SB, in such diets, can increase milk protein production and milk production efficiency.     

Effects on rumen pH and feed intake of a dietary concentrate challenge in cows fed rations containing pH modulators with different neutralizing capacity

Forty-five Holstein lactating cows (41 ± 8.8 kg/d of milk yield, 96 ± 35.6 days in milk, and 607 ± 80.4 kg of body weight) were enrolled in this study to assess the effects of diets supplemented with sodium bicarbonate or a magnesium-based product and their corresponding differences in dietary cation-anion difference (DCAD) on rumen pH, rumen microbial population, and milk performance of dairy cattle exposed to an induced decrease in rumen pH through a dietary challenge. Cows were randomly allocated to 3 total mixed rations (TMR) differing in the type of supplement to modulate rumen pH: (1) control, no supplementation; (2) SB, supplemented with 0.82% of sodium bicarbonate with a neutralizing capacity (NC) of 12 mEq/g; and (3) MG, supplemented with 0.25% of magnesium oxide (pHix-Up, Timab Magnesium) with a NC of 39 mEq/g. Thus, SB and MG rations had, in theory, the same NC. The 3 TMR differed for control, SB, and MG in their DCAD-S (calculated considering Na, K, Cl, and S), which was on average 13.2, 21.2, and 13.7 mEq/100 g, respectively, or DCAD-Mg (calculated accounting for Mg, Ca, and P), which was 31.4, 41.2, and 35.2 mEq/100 g, respectively. The study lasted 63 d, with the first 7 d serving as a baseline, followed by a fortnightly progressive decrease of dietary forage-to-concentrate ratio (FCR) starting at 48:52, then 44:56, then 40:60, and finishing at 36:64. Individual dry matter intake (DMI) was recorded daily. Seven cows per treatment were equipped with electronic rumen boluses to monitor rumen pH. Control and SB cows consumed less dry matter (DM; 23.5 ± 0.31 kg/d) than MG cows (25.1 ± 0.31 kg/d) when fed dietary FCR of 44:56 and 40:60. Energy-corrected milk decreased from 40.8 ± 1.21 to 39.5 ± 1.21 kg/d as dietary FCR decreased, independently of dietary treatments. Rumen pH decreased and the proportion of the day with rumen pH <5.8 increased as dietary FCR decreased, and at low dietary FCR (i.e., 36:64) rumen pH was greater in MG cows than in control and SB cows. Reducing the DCAD-S from 28 to 18 mEq/100 g or the DCAD-Mg from 45 to 39 mEq/kg had no effects on DMI or milk yield. Cows supplemented with ∼62 g/d of magnesium oxide (pHix-Up) maintained a greater rumen pH and consumed more DM than cows supplemented with ∼200 g/d of sodium bicarbonate when fed a diet with low FCR.     

Effects on feed intake,milk production,and methane emission in dairy cows fed silage or fresh grass with concentrate or fresh grass harvested at early or late maturity stage without concentrate

The objective of the study was to quantify the effects on dry matter intake (DMI), nutrient digestibility, gas exchange, milk production, and milk quality in dairy cows fed fresh grass harvested at different maturity stages. Sixteen Danish Holstein cows in mid-lactation were divided into 4 blocks and used in 4 incomplete 4 × 2 Latin squares with 2 periods of 21 d. The cows received 1 of 4 treatments in each period, resulting in 8 cows per treatment, as follows: grass-clover silage supplemented with 6 kg/d concentrate pellets (SILc), fresh grass harvested at late maturity stage supplemented with 6 kg/d concentrate pellets (LATc), fresh grass harvested at late maturity stage (LAT), and fresh grass harvested at early maturity stage (ERL). The cows were housed in tiestalls and milked twice daily. The cows had ad libitum access to the forage, and concentrate pellets were divided into equal amounts and fed separately in the morning and afternoon. Fecal samples were collected to determine apparent total-tract digestibility, and samples of rumen fluid were collected for determination of short chain fatty acid composition. Halters were used for measuring eating and rumination time. Gas exchange was measured in open-circuit respiration chambers. Total DMI was higher in LATc and ERL (16.9 ± 0.45 and 15.5 ± 0.39 kg/d, respectively) compared with LAT (14.1 ± 0.42 kg/d). Relative to SILc, cows fed fresh grass experienced a convex pattern in DMI during the experiment. The changes in DMI were related to changes in leaf to stem ratio, fiber concentration, and organic matter digestibility determined in vitro in samples of the fresh grass harvested throughout the experiment. The apparent total-tract digestibility of organic matter was higher in SILc and LAT compared with LATc. Methane yield was lower for LATc compared with LAT (19.5 ± 0.61 vs. 22.6 ± 0.55 g of CH₄/kg of DMI), and was not different between LAT and ERL. Compared with LAT, milk yield was higher for ERL (21.1 ± 1.14 vs. 23.4 ± 1.11 kg/d) and energy-corrected milk (ECM) yield was higher for LATc (21.5 ± 0.99 vs. 25.3 ± 1.03 kg/d). We detected no differences in milk or ECM yield between SILc and LATc. Milk protein yield was higher and milk fat concentration was lower in LATc compared with LAT. The fatty acid percentages of ∑C4-C14:1 and ∑C16 in milk were higher for SILc compared with LATc, signifying pronounced de novo synthesis. The n-6:n-3 ratio in milk fatty acids was lower for SILc and LAT compared with LATc, indicating improved nutritional quality for SILc and LAT. However, retinol concentration in milk was lower in SILc compared with all other treatments. The study implies that feeding silage instead of fresh grass has no effect on DMI, ECM yield, or CH₄ yield, and that concentrate supplementation can increase milk production, affects milk quality, and reduces the effect on climate, whereas feeding less mature grass increases DMI and milk yield, but has no effect on CH₄ yield.     

Changes in plasma electrolytes,minerals, and hepatic markers of health across the transition period in dairy cows divergent in genetic merit for fertility traits and postpartum anovulatory intervals

Peripartum metabolism and subsequent reproductive performance of dairy cows are linked, with maladaptation over the transition period associated with poor reproductive success. A herd of seasonal calving, grazing dairy cows was established that differed in their genetic merit for fertility traits. The heifers were produced by a customized mating program to achieve a 10-percentage point divergence in the New Zealand fertility breeding value (FertBV) as follows: +5 FertBV (POS) versus ?5% FertBV (NEG), while also limiting divergence in other breeding values, including body weight, body condition score, and milk production. In this study, we aimed to characterize differences in metabolic, mineral, and metabolic stress marker profiles during their first postpartum transition period as primiparous heifers and to examine if animals with longer postpartum anestrous intervals (PPAI; more than 66 d compared with less than 35 d) had greater metabolic dysfunction. Blood was sampled at ?21, ?14, ?7, 0, 4, 7, 10, 14, 17, 21, 28, and 35 d relative to calving in 455 primiparous cows and plasma analyzed. The NEG cows had lower concentrations of both plasma nonesterified fatty acids and β-hydroxybutyrate at d 7 compared with POS cows. Detailed temporal profiling of various metabolic, mineral, and metabolic stress markers was undertaken in a subset of cows (n = 70). Cows were selected retrospectively to create 4 groups in a 2 × 2 factorial design with either a POS or NEG FertBV and either a short (19–35 d) or long (66–131 d) PPAI. The NEG cows tended, on average, to have lower nonesterified fatty acids and β-hydroxybutyrate concentrations compared with POS cows across the transition period. Mean body weight and body condition score was greatest in NEG cows when compared with the POS cows and an interaction with day demonstrated this only occurred precalving. They also had indications of improved liver health precalving, with higher albumin-to-globulin ratios and lower bilirubin concentrations. Concentrations of aspartate aminotransferase were lower, and the Na-to-Cl ratio was greater in cows with a long versus a short PPAI at d 28 and d 35 after calving, potentially because of cows with a short PPAI (19–35 d) returning to estrous during this time. Magnesium concentrations were lower in NEG cows with a short PPAI from d 21 onwards, indicating NEG cows may metabolically respond to estrous differently than POS cows. The NEG-long PPAI cows had greater gamma-glutamyl transferase concentrations from calving until d 28 and lower bilirubin concentrations throughout the transition period. Together, the results demonstrate significant effects of FertBV on peripartum metabolic status. However, most of the markers tested returned to reference intervals within 4 d after calving or remained within those intervals for the whole transition period, indicating relatively minor biological effects of FertBV on transition period adaptation. The profound differences in reproductive performance among the groups was not explained by underlying differences in metabolic responses during the transition period.     

Concurrent and carryover effects of feeding blends of protein and amino acids in high-protein diets with different concentrations of forage fiber to fresh cows. 1. Production and blood metabolites

Because of low feed intake during the first weeks of lactation, dietary concentration of metabolizable protein (MP) must be elevated. We evaluated effects of providing additional rumen-undegradable protein (RUP) from a single source or a blend of protein and AA sources during the first 3 wk of lactation. We also evaluated whether replacing forage fiber (fNDF) or nonforage fiber with the blend affected responses. In a randomized block design, at approximately 2 wk prepartum, 40 primigravid (664 ± 44 kg of body weight) and 40 multigravid (797 ± 81 kg of body weight) Holsteins were blocked by calving date and fed a common diet (11.5% crude protein, CP). After calving to 25 d in milk (DIM), cows were fed 1 of 4 diets formulated to be (1) 20% deficient in metabolizable protein (MP) based on predicted milk production (17% CP, 24% fNDF), (2) adequate in MP using primarily RUP from soy to increase MP concentration (AMP; 20% CP, 24% fNDF), (3) adequate in MP using a blend of RUP and rumen-protected AA sources to increase MP concentration (Blend; 20% CP, 24% fNDF), or (4) similar to Blend but substituting fNDF with added RUP rather than nonforage neutral detergent fiber (Blend-fNDF; 20% CP, 19% fNDF). The blend was formulated to have a RUP supply with an AA profile similar to that of casein. A common diet (17% CP) was fed from 26 to 92 DIM, and milk production and composition were measured from 26 to 92 DIM, but individual dry matter intake (DMI) was measured only until 50 DIM. During the treatment period for both parities, AMP and Blend increased energy-corrected milk (ECM) yields compared with the diet deficient in MP based on predicted milk production (40.7 vs. 37.8 kg/d) and reduced concentrations of plasma 3-methyl-His (4.1 vs. 5.3 µmol/L) and growth hormone (9.0 vs. 11.9 ng/mL). Blend had greater DMI than AMP (17.4 vs. 16.1 kg/d), but ECM yields were similar. Blend had greater plasma Met (42.0 vs. 26.4 µmol/L) and altered metabolites associated with antioxidant production and methyl donation compared with AMP. Conversely, the concentration of total essential AA in plasma was less in Blend versus AMP (837 vs. 935 µmol/L). In multiparous cows, Blend-fNDF decreased DMI and ECM yield compared with Blend (19.2 vs. 20.1 kg/d of DMI, 45.3 vs. 51.1 kg/d of ECM), whereas primiparous cows showed the opposite response (15.3 vs. 14.6 kg/d of DMI, 32.9 vs. 31.4 kg/d of ECM). Greater DMI for multiparous cows fed Blend carried over from 26 to 50 DIM and was greater compared with AMP (23.1 vs. 21.2 kg /d) and Blend-fNDF (21.3 kg/d). Blend also increased ECM yield compared with AMP (49.2 vs. 43.5 kg/d) and Blend-fNDF (45.4 kg/d) from 26 to 92 DIM. Few carryover effects of fresh cow treatments on production were found in primiparous cows. Overall, feeding blends of RUP and AA may improve the balance of AA for fresh cows fed high MP diets and improve concurrent and longer-term milk production in multiparous cows. However, with high MP diets, multiparous fresh cows require greater concentrations of fNDF than primiparous cows.     

Effects of an exogenous enzyme preparation extracted from a mixed culture of Aspergillus spp. on lactational performance,metabolism, and digestibility in primiparous and multiparous cows

The objective of this study was to investigate the effects of an exogenous enzyme preparation from Aspergillus oryzae and Aspergillus niger on lactational performance of dairy cows. Forty-eight Holstein cows (32 primiparous and 16 multiparous) averaging (± SD) 36.3 ± 8.7 kg/d milk yield and 141 ± 52 d in milk were enrolled in a 10-wk randomized complete block design experiment (total of 24 blocks) and assigned to 1 of 2 treatments: basal diet, no enzyme supplementation (CON) or the basal diet supplemented with 4.2 g/kg dry matter intake (DMI) of an exogenous enzyme preparation containing amylolytic and fibrolytic activities (ENZ). After a 2-wk covariate period, premixes with the enzyme preparation or control were top-dressed daily by mixing with approximately 500 g of total mixed ration. Production data were collected daily and averaged by week. Milk samples were collected every other week, and milk composition was averaged by week. Blood, fecal, and urine samples were collected over 2 consecutive days at 0, 4, 8, 12, and 36 h after feeding during the last week of the experiment. Compared with CON, cows fed ENZ tended to increase DMI and had increased milk concentrations of true protein, lactose, and other solids. Milk fat content tended to be higher in CON cows. A treatment × parity interaction was found for some of the production variables. Primiparous cows receiving ENZ had greater yields of milk, energy-corrected milk, milk true protein, and lactose compared with CON primiparous cows; these production variables did not differ between treatments for multiparous cows. Intake and total-tract digestibility of nutrients did not differ between treatments. Concentrations of blood glucose and total fatty acids were not affected by ENZ supplementation, but β-hydroxybutyrate concentration tended to be greater in ENZ cows. Overall, the exogenous enzyme preparation used in this study increased milk protein and lactose concentrations in all cows, and milk production in primiparous but not multiparous cows. The differential production response between primiparous and multiparous cows was likely a result of a greater increase in DMI with ENZ supplementation in the younger animals.     

Effect of dietary inclusion of winter brassica crops on milk production,feeding behavior,rumen fermentation,and plasma fatty acid profile in dairy cows

This study determined feeding behavior, dry matter (DM) intake (DMI), rumen fermentation, and milk production responses of lactating dairy cows fed with kale (Brassica oleracea) or swede (Brassica napus ssp. napobrassica). Twelve multiparous lactating dairy cows (560 ± 22 kg of body weight, 30 ± 4 kg of milk/d, and 60 ± 11 d in milk at the beginning of the experiment; mean ± standard deviation) were randomly allocated to 3 dietary treatments in a replicated 3 × 3 Latin square design. The control diet comprised 10 kg of grass silage DM/d, 4 kg of ryegrass herbage DM/d, and 8.8 kg of concentrate DM/d. Then, 25% of herbage, silage, and concentrate (DM basis) was replaced with either kale or swede. Cows offered kale had decreased total DMI compared with cows fed the control and swede diets, whereas inclusion of swede increased eating time. Milk production, composition, and energy-corrected milk:DMI ratio were not affected. Cows fed with kale had a greater rumen acetate:propionate ratio, whereas swede inclusion increased the relative percentage of butyrate. Estimated microbial N was not affected by dietary treatments, but N excretion was reduced with inclusion of kale, improving N utilization. Cows fed kale tended to have increased nonesterified fatty acids and showed presence of Heinz-Ehrlich bodies, whereas hepatic enzymes such as aspartate aminotransferase, γ-glutamyl transferase, and glutamate dehydrogenase were not affected by dietary treatments. In plasma, compared with the control, swede and kale reduced total saturated fatty acids and increased total polyunsaturated fatty acids and total n-3 fatty acids. Overall, feeding cows with winter brassicas had no negative effect on production responses. However, mechanisms to maintain milk production were different. Inclusion of swede increased the time spent eating and maintained DMI with a greater relative rumen percentage of butyrate and propionate, whereas kale reduced DMI but increased triacylglycerides mobilization, which can negatively affect reproductive performance. Thus, the inclusion of swede may be more suitable for feeding early-lactating dairy cows during winter.     

Feed additives containing sequestrant clay minerals and inactivated yeast reduce aflatoxin excretion in milk of dairy cows

The objective was to evaluate the efficacy of 2 dietary mycotoxin sequestrants, Toxy-Nil (TN) or Unike Plus (UP), in reducing aflatoxin (AF) M₁ concentrations in milk of dairy cows challenged with dietary AF. Thirty-two mid-lactation Holstein cows were blocked by parity, days in milk, and milk yield and were randomly assigned within block to receive one of the following treatments: (1) 2.8 mg of AF/cow per d (positive control, PC), (2) 2.8 mg of AF + 100 g of TN/cow per d, (3) 2.8 mg of AF + 100 g of UP/cow per d, or (4) no AF and no additives (negative control, NC). For 7 d, treatments, dispersed in 150 g of sweet feed carrier, were top-dressed twice daily by mixing into the top portion of the TMR at each feeding. After the experimental period, cows were fed the NC diet and clearance of AFM₁ via milk was monitored for 7 d. Feed and water were available ad libitum throughout the trial. Treatments had no effect on feed intake, milk yield, milk composition, or milk somatic cell count. Relative intake of AF was similar among PC, TN, and UP, averaging 106.5, 107.6, and 102.5 ± 2.9 μg/kg of diet dry matter, respectively. Relative intake of mycotoxin sequestrants was similar between TN and UP, averaging 0.4 and 0.4 ± 0.1% of diet dry matter, respectively. Concentration and mass of AFM₁ secreted in milk and in urine were similar between TN and UP, but were lower than PC; concentrations in milk averaged 0.2, 0.3, and 0.6 ± 0.1 μg/kg, respectively, and mass secreted in milk averaged 8.1, 9.8, and 20.5 ± 1.7 μg/d. Concentrations in urine averaged 6.9, 7.4, and 14.2 ± 1.5 μg/L, respectively, and mass secreted in urine averaged 225.7, 250.8, and 521.6 ± 53.1 μg/d. Likewise, concentration and mass of free AF excreted in feces were similar between TN and UP, but were lower than PC; concentrations averaged 7.7, 8.9, and 12.4 ± 0.6 μg/kg, respectively, and mass excreted averaged 57.8, 69.6, and 95.6 ± 4.8 μg/d. Transfer of AF from feed to AFM₁ in milk was reduced by 63 and 52%, and in urine, by 57 and 52% for TN and UP, respectively. Transfer of AF from feed to free AF in feces was reduced by 38 and 26% for TN and UP, respectively. The clearance rate of AFM₁ in milk did not differ among PC, TN, and UP (46.1, 66.5, and 50.0 ± 6.7%/d, respectively). Results indicate that dietary inclusion of 100 g of TN or UP significantly reduced AFM₁ in milk of cows consuming TMR containing approximately 105 μg of AF/kg of diet dry matter. Results also suggest that both TN and UP reduced absorption of AF.     

Effect of nutritional immunomodulation and heat stress during the dry period on subsequent performance of cows

Heat stress in dairy cows during the dry period impairs milk yield in the next lactation. Feeding OmniGen-AF (OG; Phibro Animal Health Corp., Teaneck, NJ) to lactating cows during heat stress may increase dry matter intake (DMI) and lowers respiration rate (RR) and rectal temperature (RT), but the effects in dry cows are not known. We hypothesized that OG supplementation before, during, and after the dry period (approximately 160 d total) would overcome the effects of heat stress and improve cow performance in the next lactation. Cows were randomly assigned to OG or control (placebo) treatments for the last 60 d in milk (DIM), based on mature-equivalent milk yield in the previous lactation. Cows were dried off 45 d before expected calving and randomly assigned to heat stress (HT) or cooling (CL) treatments. Thus, cows received dietary supplementation during late lactation before they were exposed to either CL or HT. After dry-off, treatment groups included heat stress with placebo (HT, only shade, 56 g/d of placebo, n = 17), HT with OG supplementation (HTOG, 56 g/d of OG, n = 19), cooling with placebo (CL, shade, fans, and soakers, 56 g/d of placebo, n = 16), and CL with OG supplementation (CLOG, 56 g/d of OG, n = 11). After parturition, all cows were kept under the same CL system and management, and all cows continued to receive OG or control treatment until 60 DIM. Cooling cows during the dry period reduced afternoon RT (CL vs. HT; 38.9 ± 0.05 vs. 39.3 ± 0.05°C) and RR (CL vs. HT; 45 ± 1.6 vs. 77 ± 1.6 breaths/min). Respiration rate was also decreased by OG supplementation under HT conditions (HTOG vs. HT; 69.7 ± 1.6 vs. 77.2 ± 1.6 breaths/min). An interaction was observed between OG supplementation and HT; HTOG cows tended to have lower morning RT compared with HT cows. During the dry period, OG reduced DMI relative to control cows. Birth weight was greater in calves from CL cows (CL vs. HT; 40.6 ± 1.09 vs. 38.7 ± 1.09 kg). No differences were detected among treatments in hematocrit, total protein, and body condition score. Cows offered CLOG, CL, and HTOG treatments had greater body weight during the dry period (794.9 ± 17.9, 746.8 ± 16.7, and 762.9 ± 14.9 kg, respectively) than HT cows (720 ± 16.2 kg). Gestation length was approximately 4 d longer for CL cows compared with HT cows. Cows offered CLOG, CL, and HTOG treatments produced more milk (41.3 ± 1.6, 40.7 ± 1.6, and 40.5 ± 1.6 kg/d, respectively) than HT treatment (35.9 ± 1.6 kg/d). Body weight after parturition and DMI were evaluated up to 60 DIM and averaged 661.5 ± 15.8 and 19.4 ± 0.7 kg/d, respectively, with no differences observed among treatments. These results confirm that exposure of dry cows to heat stress negatively affects milk yield in the subsequent lactation. Active cooling of dry cows and OG supplementation can reduce the negative effects of heat stress in the dry period on subsequent performance.     

Heifers with positive genetic merit for fertility traits reach puberty earlier and have a greater pregnancy rate than heifers with negative genetic merit for fertility traits

This study investigated the hypothesis that dairy heifers divergent in genetic merit for fertility traits differ in the age of puberty and reproductive performance. New Zealand's fertility breeding value (FertBV) is the proportion of a sire's daughters expected to calve in the first 42 d of the seasonal calving period. We used the New Zealand national dairy database to identify and select Holstein-Friesian dams with either positive (POS, +5 FertBV, n = 1,334) or negative FertBV (NEG, ?5% FertBV, n = 1,662) for insemination with semen from POS or NEG FertBV sires, respectively. The resulting POS and NEG heifers were predicted to have a difference in average FertBV of 10 percentage points. We enrolled 640 heifer calves (POS, n = 324; NEG, n = 316) at 9 d ± 5.4 d (± standard deviation; SD) for the POS calves and 8 d ± 4.4 d old for the NEG calves. Of these, 275 POS and 248 NEG heifers were DNA parent verified and retained for further study. The average FertBV was +5.0% (SD = 0.74) and ?5.1% (SD = 1.36) for POS and NEG groups, respectively. Heifers were reared at 2 successive facilities as follows: (1) calf rearing (enrollment to ～13 wk of age) and (2) grazier, after 13 wk until 22 mo of age. All heifers wore a collar with an activity sensor to monitor estrus events starting at 8 mo of age, and we collected weekly blood samples when individual heifers reached 190 kg of body weight (BW) to measure plasma progesterone concentrations. Puberty was characterized by plasma progesterone concentrations >1 ng/mL in at least 2 of 3 successive weeks. Date of puberty was defined when the first of these samples was >1 ng/mL. Heifers were seasonally bred for 98 d starting at ～14 mo of age. Transrectal ultrasound was used to confirm pregnancy and combined with activity data to estimate breeding and pregnancy dates. We measured BW every 2 wk, and body condition and stature at 6, 9, 12, and 15 mo of age. The significant FertBV by day interaction for BW was such that the NEG heifers had increasingly greater BW with age. This difference was mirrored with the significant FertBV by month interaction for average daily gain, with the NEG heifers having a greater average daily gain between 9 and 18 mo of age. There was no difference in heifer stature between the POS and NEG heifers. The POS heifers were younger and lighter at puberty, and were at a lesser mature BW, compared with the NEG heifers. As a result, 94 ± 1.6% of the POS and 82 ± 3.2% of the NEG heifers had reached puberty at the start of breeding. The POS heifers were 20% and 11% more likely to be pregnant after 21 d and 42 d of breeding than NEG heifers (relative risk = 1.20, 95% confidence interval of 1.03–1.34; relative risk = 1.11, 95% confidence interval of 1.01–1.16). Results from this experiment support an association between extremes in genetic merit for fertility base on cow traits and heifer reproduction. Our results indicate that heifer puberty and pregnancy rates are affected by genetic merit for fertility traits, and these may be useful phenotypes for genetic selection.     

Effects of rumen-degradable protein:rumen-undegradable protein ratio and corn processing on production performance,nitrogen efficiency,and feeding behavior of Holstein dairy cows

This study was conducted to investigate the effects of the ratio of rumen-degradable protein (RDP) to rumen-undegradable protein (RUP) and corn processing method on production performance, nitrogen (N) efficiency, and feeding behavior of high-producing Holstein dairy cows. Twelve multiparous Holstein cows (second parity; milk yield = 48 ± 3 kg/d) were assigned to a replicated 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments. Factor 1 was corn processing method [ground corn (GC) or steam flaked corn (SFC) with a flake density of about 390 g/L], and factor 2 was RDP:RUP ratio [low ratio (LR) = 60:40; high ratio (HR) = 65:35] based on crude protein (%). The crude protein concentrations were kept constant across the treatments (16.7% of DM). No significant interactions of main treatment effects occurred for lactation performance data. Cows fed 2 different RDP:RUP ratios exhibited similar dry matter intake (DMI), but those fed SFC showed decreased feed intake compared with those receiving GC (25.1 ± 0.48 vs. 26.2 ± 0.47 kg/d, respectively). Cows fed HR diets produced more milk than did those fed LR diets (44.4 ± 1.05 vs. 43.2 ± 1.05 kg/d, respectively). Milk fat content decreased but milk protein content increased in cows fed SFC compared with those fed GC. Feed efficiency (i.e., milk yield/DMI) was enhanced with increasing ratio of RDP:RUP (1.68 ± 0.04 vs. 1.74 ± 0.04 for LR and HR, respectively). Apparent N efficiency was higher in cows fed HR than in those fed LR (30.4 ± 0.61 vs. 29.2 ± 0.62, respectively). Compared with cows fed the GC-based diet, those receiving SFC exhibited lower values of N intake, N-NH₃ concentration, and fecal N excretion. Cows receiving SFC-based diets spent more time ruminating (min/kg of DMI) than did those fed GC. Although these results showed no interaction effects of RDP:RUP ratio and corn processing method on performance, higher RDP:RUP ratios and ground corn can be effective feeding strategies for feed to lactating cows receiving high-concentrate diets.     

Positive genetic merit for fertility traits is associated with superior reproductive performance in pasture-based dairy cows with seasonal calving

New Zealand's Fertility Breeding Value (FertBV) is reported as the percentage of a sire's daughters that calve in the first 42 d of the seasonal calving period and is an estimate of genetic merit for fertility for dairy cattle. Reproductive physiology, milk production, and changes in body weight and body condition score of 2 groups of cows divergent in FertBV (+5.0%: POS; −5.1%: NEG) were characterized during their first 2 lactations. Cows grazed fresh pasture and were managed in a seasonal calving system; they were bred by artificial insemination on observed estrus for the entire breeding period (98 d in lactation 1 and 76 d in lactation 2). During lactation 1, all animals were primiparous and were randomly allocated to 1 of 2 herds, ensuring each herd was balanced for FertBV and expected calving date. During lactation 2, cows that became pregnant during lactation 1 were managed as 1 herd. Cows not inseminated in the first 42 d of the breeding season were examined for the presence of a corpus luteum and treated with an anestrus program. On average, the interval from calving to ovulation was 19 d longer in lactation 1 and 10 d longer in lactation 2 for NEG FertBV cows. The percent of cows submitted for artificial insemination after 21 d (i.e., submission rate) was 38 and 25 percentage points greater in the POS FertBV cows during lactations 1 and 2, respectively. Pregnancy rate from 42 d of breeding was 33 and 30 percentage points greater, respectively. There was no effect of FertBV on vaginal discharge score postcalving; however, POS FertBV cows had a 50% lower risk of having subclinical endometritis (polymorphonuclear leukocytes >7%) 42 d postcalving. Interactions between FertBV and month relative to calving identified that NEG FertBV cows were fatter (greater body condition score) in the month before calving, but thinner between 3 and 5 mo postcalving. There was no effect of FertBV on lactation length, estimated 270-d milk yields, or daily milk, fat, or protein yields, and only small effects on milk fat and protein percentage across the lactations. In summary, the POS FertBV cows had superior uterine health, a shorter calving to ovulation interval, a greater submission rate, and a greater pregnancy rate earlier in the breeding season when compared with the NEG FertBV cohort. Based on these results, these may be useful phenotypes to include in genetic selection indices.     

Short communication: Increased somatic cell count is associated with milk loss and reduced feed efficiency in lactating dairy cows

The objective was to evaluate the relationship of somatic cell count (SCC; cells/mL) with milk yield, energy-corrected milk yield (ECM; kg/d), dry matter intake (DMI; kg/d), feed efficiency for milk (FE_MY; kg of milk/kg of DMI), and feed efficiency for ECM (FE_ECM; kg of ECM/kg of DMI) in lactating dairy cows. We analyzed an SCC database consisting of 7 experiments, which were conducted at The Pennsylvania State University's Dairy Teaching and Research Center between 2009 and 2015. The experiments included in the SCC database were randomized block designs and investigated dietary effects on cow performance over 6 to 11 wk. Each experiment took repeated measurements of SCC, milk yield, milk composition, and DMI. After exclusion of records from cows without lactation number, days in milk, and only 1 measurement, the database comprised 1,094 observations of 254 cows for estimating the effect of SCC on milk yield, DMI, and FE_MY and 1,079 observations of 250 cows for estimating the effect of SCC on ECM and FE_ECM. Data were analyzed in R using a linear mixed model with natural logarithm of SCC, lactation number (1, 2, and ≥3), days in milk, and the interactions of the linear predictors as fixed effects and cow within block and experiment as random effect. Natural logarithm of SCC was negatively correlated with milk yield, ECM, DMI, FE_MY, and FE_ECM. Our results suggest that a cow with relatively high SCC (250,000 cells/mL) compared with a cow with a relatively low SCC (50,000 cells/mL) produces, on average, 1.6 kg/d less milk, consumes 0.3 kg/d less DMI, produces 0.04 kg less milk per kg of DMI, and produces 0.03 less ECM per kg of DMI. The observed decrease of feed efficiency with increased SCC adds to previously known economic losses and environmental impacts associated with mastitis, which should provide a further incentive to control mastitis in dairy cows.     

Effects of corn grain endosperm type and fineness of grind on feed intake,feeding behavior,and productive performance of lactating dairy cows

Our objective was to evaluate effects of corn grain endosperm type and fineness of grind on feed intake, feeding behavior, ruminal fermentation, and productive performance of lactating cows. Eight ruminally and duodenally cannulated Holstein cows in mid lactation (130 ± 42 d in milk; mean ± standard deviation) were used in a duplicated 4 × 4 Latin square design with 21-d periods. A 2 × 2 factorial arrangement of treatments was used with main effects of corn grain endosperm type (floury or vitreous) and fineness of grind of corn grain (fine or medium). Rations were formulated to contain 29% starch, 27% neutral detergent fiber, 18.2% forage neutral detergent fiber, and 18% crude protein. Corn grain treatments supplied 86.2% of dietary starch. Endosperm was 25% vitreous for floury corn and 66% vitreous for vitreous corn. Fineness of grind did not affect dry matter intake (DMI), but floury corn tended to reduce DMI (23.8 vs. 25.1 kg/d) compared with vitreous corn. Floury corn increased meal frequency more for fine grind size (9.57 vs. 9.41 meals/d) than medium grind size (9.78 vs. 9.75 meals/d). However, there were no effects of treatment on any other measure of feeding behavior. Endosperm type did not affect yields of milk or milk components or milk composition except that vitreous corn tended to decrease milk lactose concentration compared with floury corn. Finely ground corn decreased yields of milk (31.1 vs. 33.1 kg/d), 3.5% fat-corrected milk (33.1 vs. 35.1 kg/d), milk fat (1.22 vs. 1.32 kg/d), milk lactose (1.48 vs. 1.59 kg/d), and solids not fat (2.46 vs. 2.63 kg/d) compared with medium grind size. However, fineness of grind did not affect milk composition. Treatments had no effect on change in body weight or body condition score or efficiency of milk production (kg of 3.5% fat-corrected milk/kg of DMI). Mean ruminal pH was not affected by treatment, but pH variance was decreased by vitreous compared with floury corn. Total volatile fatty acids and propionate concentrations in the rumen were increased by floury compared with vitreous corn but were not affected by fineness of grind. Effects of fineness of grind on yield of milk and milk components were greater than the effects of corn grain vitreousness.     

Association of peripartum plasma insulin concentration with milk production,colostrum insulin levels,and plasma metabolites of Holstein cows

The main objective of this study was to assess associations between plasma insulin concentration around parturition and production in Holstein cows. Primiparous and multiparous cows (n = 267) were enrolled. Blood samples were collected within 12 h after parturition (d 0), and on d 3 and 10 after calving. In addition, blood samples were collected 7 d before (?7 d) the expected date of parturition and colostrum samples were collected within 8 h after parturition from a subset of cows to measure insulin concentration (n = 47). All samples were harvested from 0630 to 1100 h and were used to quantify insulin, nonesterified fatty acids (NEFA), and β-hydroxybutyrate. The plasma concentrations of insulin on d ?7 and 0 were not correlated with insulin levels in colostrum. Cows were grouped according to plasma insulin concentration based on the median as low insulin (L-INS) or high insulin (H-INS) on d 0 (median = 0.35 ng/mL; range 0.2 to 1.2), 3 (median = 0.32 ng/mL; range 0.2 to 1.6), and 10 (median = 0.30 ng/mL; range 0.2 to 0.8). We detected that cows in the L-INS group on d 0 (L-INS = 0.57 ± 0.02; H-INS = 0.49 ± 0.02 mmol/L), d 3 (L-INS = 0.56 ± 0.02; H-INS = 0.49 ± 0.02 mmol/L), and d 10 (L-INS = 0.61 ± 0.03; H-INS = 0.55 ± 0.03 mmol/L) had higher NEFA concentrations compared with cows in the H-INS group. Compared with H-INS cows, milk yield was higher for cows classified as L-INS on d 0 (L-INS = 40.75 ± 0.69; H-INS = 38.41 ± 0.64 kg) and d 10 (L-INS = 40.95 ± 0.74; H-INS = 38.66 ± 0.64 kg). Moreover, fat-corrected milk was higher for cows classified as L-INS on d 0 (L-INS = 40.59 ± 2.36; H-INS = 37.73 ± 2.31 kg) and d 10 (L-INS = 41.00 ± 2.42; H-INS = 38.65 ± 2.28 kg) compared with H-INS cows, and energy-corrected milk was higher for L-INS cows compared with H-INS cows regardless of the day (d 0, L-INS = 44.50 ± 0.70 vs. H-INS = 41.67 ± 0.64 kg; d 3, L-INS = 43.65 ± 0.74 vs. H-INS = 40.88 ± 0.72 kg; d 10, L-INS = 44.09 ± 0.73 vs. H-INS = 40.55 ± 0.68 kg). We conclude that low plasma insulin concentration during early lactation is associated with higher milk yield in the long term.     

Effect of chromium on bioenergetics and leukocyte dynamics following immunoactivation in lactating Holstein cows

Activated immune cells are insulin sensitive and utilize copious amounts of glucose. Because chromium (Cr) increases insulin sensitivity and may be immunomodulatory, our objective was to evaluate the effect of supplemental Cr (KemTrace Cr propionate, 20 g/d; Kemin Industries Inc., Des Moines, IA) on immune system glucose utilization and immune system dynamics following an intravenous endotoxin challenge in lactating Holstein cows. Twenty cows (320 ± 18 d in milk) were randomly assigned to 1 of 4 treatments: (1) pair-fed (PF) control (PF-CON; 5 mL of saline; n = 5), (2) PF and Cr supplemented (PF-Cr; 5 mL of saline; n = 5), (3) lipopolysaccharide (LPS)-euglycemic clamp and control supplemented (LPS-CON; 0.375 µg/kg of body weight LPS; n = 5), and (4) LPS-euglycemic clamp and Cr supplemented (LPS-Cr; 0.375 µg/kg of body weight LPS; n = 5). The experiment was conducted serially in 3 periods (P). During P1 (3 d), cows received their respective dietary treatments and baseline values were obtained. At the initiation of P2 (2 d), either a 12-h LPS-euglycemic clamp was conducted or cows were PF to their respective dietary counterparts. During P3 (3 d), cows consumed feed ad libitum and continued to receive their respective dietary treatment. During P2, LPS administration decreased dry matter intake (DMI; 40%) similarly among diets, and by experimental design the pattern and magnitude of reduced DMI were similar in the PF cohorts. During P3, LPS-Cr cows tended to have decreased DMI (6%) relative to LPS-CON cows. Relative to controls, milk yield from LPS-challenged cows decreased (58%) during P2 and LPS-Cr cows produced less (16%) milk than LPS-CON cows. During P3, milk yield progressively increased similarly in LPS-administered cows, but overall milk yield remained decreased (24%) compared with PF controls. There were no dietary treatment differences in milk yield during P3. Circulating insulin increased 9- and 15-fold in LPS-administered cows at 6 and 12 h postbolus, respectively, compared with PF controls. Compared with LPS-CON cows, circulating insulin in LPS-Cr cows was decreased (48%) at 6 h postbolus. Relative to PF cows, circulating LPS binding protein and serum amyloid A from LPS-administered cows increased 2- and 5-fold, respectively. Compared with PF cows, blood neutrophil counts in LPS-infused cows initially decreased, then gradually increased 163%. Between 18 and 48 h postbolus, the number of neutrophils was increased (12%) in LPS-Cr versus LPS-CON cows. The 12-h total glucose deficit was 220 and 1,777 g for the PF and LPS treatments, respectively, but glucose utilization following immune activation was not influenced by Cr. In summary, supplemental Cr reduced the insulin response and increased circulating neutrophils following an LPS challenge but did not appear to alter the immune system's glucose requirement following acute and intense activation.     

Effects of corn grain endosperm type and conservation method on feed intake,feeding behavior,and productive performance of lactating dairy cows

Our objective was to evaluate the effects of corn grain varying in endosperm type and conserved as high-moisture or dry ground corn on dry matter intake (DMI), feeding behavior, ruminal fermentation, and yields of milk and milk components of cows in early to mid-lactation. Seven ruminally and duodenally cannulated Holstein cows (73 ± 39 d in milk; mean ± SD) were used in a duplicated 4 × 4 Latin square design with 21-d periods. A 2 × 2 factorial arrangement of treatments was used with main effects of corn grain endosperm type (floury or vitreous) conserved as high-moisture corn (HMC) or dry ground corn (DGC). Rations were formulated to contain 27.0% starch, 26.6% neutral detergent fiber (NDF), 19.1% forage NDF, and 16.5% crude protein. Corn grain treatments supplied 86.6% of dietary starch and contained alfalfa silage as the sole forage. Dry matter intake was increased 1.3 kg/d by DGC compared with HMC. The increase in DMI by DGC was related to a shorter intermeal interval (104.4 vs. 118.2 min/d), and meal size was not affected by treatment. Dry ground corn decreased rumination bout length and number of chews per bout compared with HMC. No differences were detected between endosperm treatments for DMI, yields of milk, 3.5% fat-corrected milk (FCM), milk fat, protein, lactose, or solids-not-fat (SNF). Mean yield of 3.5% FCM across treatments was 47.5 kg/d. However, a tendency for an interaction was observed for feed efficiency; floury endosperm increased efficiency 0.05 kg 3.5% FCM per kg of DMI for DGC but decreased it by 0.14 kg 3.5% FCM per kg of DMI for HMC relative to vitreous endosperm. Vitreous compared with floury corn tended to increase true protein concentration in milk when conserved as DGC (2.68% vs. 2.62%) but not as HMC. Concentration of SNF was increased by DGC compared with HMC (8.45 vs. 8.37%) due, in part, to the effect of treatment on milk protein concentration. Body weight was not affected by treatment, but vitreous endosperm tended to increase loss of body condition compared with floury endosperm. Corn endosperm type and conservation method had little effect on productive performance of high-producing cows.