Effects of alfalfa hay particle size in high-concentrate diets supplemented with unsaturated fat: Chewing behavior,total-tract digestibility,and milk production of dairy cows

This study evaluated the effects of increasing the physically effective neutral detergent fiber (peNDF) intake of lactating dairy cows fed high-concentrate diets supplemented with unsaturated fat on intake, eating behavior, diet sorting, chewing activity, total-tract digestibility, and milk production and composition. Diets contained 24% alfalfa hay (AH), 16% corn silage, 58% concentrate, and 2% yellow grease [dry matter (DM) basis], and dietary peNDF content was increased by varying the particle size (PS) of the AH. Nine multiparous cows averaging 87.8 ± 14.8 d in milk and weighing 653 ± 53 kg were randomly assigned to a triplicate 3 × 3 Latin square. During each 21-d period, cows were offered 1 of 3 total mixed rations that varied in PS of AH: fine, medium, and long, with a geometric mean particle length of 3.00, 3.57 and 3.87 mm, respectively. Increasing PS quadratically affected DM intake (DMI; 24.7, 25.4, and 23.7 kg/d, for fine, medium, and long, respectively), but cumulative DMI at 2, 4, and 6 h after feeding was similar across treatments, averaging 23.4, 35.6 and 46.4% of total DMI for the 3 time points, respectively. Increased peNDF intake did not affect feed sorting, but increased daily eating time, and eating and total chewing time per kilogram of DMI. Daily rumination time exhibited a quadratic response, with highest rumination time for the medium diet. Dietary PS had no effects on digestibility in the total tract, but we observed, for fine, medium, and long diets, quadratic responses in milk production (41.5, 43.3, and 40.4 kg/d), 4% fat-corrected milk production, and milk protein yield. Milk fat content decreased linearly with increasing PS, but milk fat content and fat:protein ratio were low for all treatments, likely due to adding unsaturated fat to a diet containing a high level of nonfiber carbohydrates (42.2% of DM). The composition, degree of saturation, and total conjugated linoleic acid content of fatty acids in milk fat were not affected by the change in peNDF content of the diet. The study indicates that a moderate increase in the PS of AH in diets containing unsaturated fat elevates peNDF intake and increases chewing activity, DMI, milk yield and milk fat production. However, the effects of dietary PS were quadratic, with maximum DMI and milk production observed with diets supplying 24% dietary peNDF (measured as the proportion of the ration retained on sieves >1.18 mm multiplied by dietary neutral detergent fiber content; DM basis).     

Effect of fibrolytic enzyme application to low- and high-concentrate diets on the performance of lactating dairy cattle

The objective of this study was to examine the effect of applying a fibrolytic enzyme preparation to diets with high (48% of diet dry matter, DM) or low (33% of diet DM) proportions of concentrate on production performance of lactating dairy cows. Sixty lactating Holstein cows (589 kg ± 20; 22 ± 3 d in milk) were stratified according to milk production and parity and randomly assigned to 4 treatments with a 2 × 2 factorial arrangement. Dietary treatments included the following: 1) low-concentrate diet (LC); 2) LC plus enzyme (LCE); 3) high-concentrate diet (HC); and 4) HC plus enzyme (HCE). The enzyme was sprayed at a rate of 3.4 mg of enzyme/g of DM on the total mixed ration daily and the trial lasted for 63 d. A second experiment with a 4 × 4 Latin square design used 4 ruminally fistulated cows to measure treatment effects on ruminal fermentation and in situ ruminal dry matter degradation during four 18-d periods. Enzyme application did not affect dry matter intake (DMI; 23.9 vs. 22.3 kg/d) or milk production (32.8 vs. 34.2 kg/d) but decreased estimated CH₄ production, increased total volatile fatty acid concentration (114.5 vs. 125.7 mM), apparent total tract digestibility of DM (69.8 vs. 72.6%), crude protein (CP; 69.2 vs. 73.3%), acid detergent fiber (50.4 vs. 54.8%), neutral detergent fiber (53.7 vs. 55.4%), and the efficiency of milk production (1.44 vs. 1.60 kg of milk/kg of DMI). Feeding more concentrates increased DMI (21.5 vs. 24.8 kg/d), milk yield (32.2 vs. 34.7 kg/d), milk protein yield (0.89 vs. 0.99 kg/d), and DM (69.9 vs. 72.6%), but decreased ruminal pH (6.31 vs. 6.06). Compared with cows fed HC, those fed LCE had lower DMI (20.8 vs. 25.7 kg/d) and CP intake (3.9 vs. 4.8 kg/d), greater ruminal pH (6.36 vs. 6.10), and similar milk yield (33.2 ± 1.1 kg/d). Consequently, the efficiency of milk production was greater in cows fed LCE than those fed HC (1.69 vs. 1.42 kg of milk/kg of DMI). This fibrolytic enzyme increased the digestibility of DM, CP, neutral detergent fiber, and acid detergent fiber and the efficiency of milk production by dairy cows. Enzyme application to the low-concentrate diet resulted in as much milk production as that from cows fed the untreated high-concentrate diet.     

Crushed sunflower, flax, or canola seeds in lactating dairy cow diets: Effects on methane production, rumen fermentation, and milk production

The objective of this study was to investigate the potential of reducing enteric methane production from dairy cows by incorporating into the diet various sources of long-chain FA varying in their degree of saturation and ruminal availability. The experiment was conducted as a crossover design with 16 lactating dairy cows maintained in 2 groups and fed 4 dietary treatments in four 28-d periods. Eight ruminally cannulated primiparous cows (96 ± 18 d in milk) were assigned to group 1 and 8 multiparous cows (130 ± 31 d in milk) were assigned to group 2. The dietary treatments were: 1) a commercial source of calcium salts of long-chain fatty acids (CTL), 2) crushed sunflower seeds (SS), 3) crushed flaxseed (FS), and 4) crushed canola seed (CS). The oilseeds added 3.1 to 4.2% fat to the diet (DM basis). All 3 oilseed treatments decreased methane production (g/d) by an average of 13%. When corrected for differences in dry matter intake (DMI), compared with CTL, methane production (g/kg of DM intake) was decreased by feeding FS (−18%) or CS (−16%) and was only numerically decreased (−10%) by feeding SS. However, compared with the CTL, feeding SS or FS lowered digestible DMI by 16 and 9%, respectively, because of lowered digestibility. Thus, only CS lowered methane per unit of digestible DM intake. Feeding SS and CS decreased rumen protozoal counts, but there were no treatment effects on mean ruminal pH or total volatile fatty acid concentration. Milk efficiency (3.5% fat corrected milk/DMI), milk yield, and component yield and concentrations were not affected by oilseed treatments. The study shows that adding sources of long-chain fatty acids to the diet in the form of processed oilseeds can be an effective means of reducing methane emissions. However, for some oilseeds such as SS or FS, the reduction in methane can be at the expense of diet digestibility. The use of crushed CS offers a means of mitigating methane without negatively affecting diet digestibility, and hence, milk production.     

Milk production and composition of mid-lactation cows consuming perennial ryegrass-and chicory-based diets

Dry matter intakes (DMI), nutrient selection, and milk production responses of dairy cows grazing 3 herbage-based diets offered at 2 allowances were measured. The 2 allowances were 20 (low) and 30 (high) kg of dry matter (DM)/cow per day and these were applied to 3 herbage types: perennial ryegrass (PRG) and chicory (CHIC+) monocultures and a mixed sward of chicory and perennial ryegrass (MIX). The CHIC+ diet was supplemented with alfalfa hay (approximately 2 kg of DM/cow per day) to maintain dietary neutral detergent fiber (NDF) concentration and all diets were supplemented with energy-based pellets (6 kg of DM/cow per day). Holstein-Friesian dairy cows averaging 136 ± 30 d in milk were allocated to 4 replicates of the 6 treatments using stratified randomization procedures. Cows were adapted to their experimental diets over a 14-d period, with measurements of DMI, milk yield, and composition conducted over the following 10 d. Herbage DMI was lowest (12.8 vs. 14.0 kg of DM/d) for CHIC+ compared with the MIX and PRG, although total forage intake (grazed herbage plus hay) was similar (14.0 to 15.0 kg of DM/d) across the 3 treatments. Milk production, milk protein, and milk fat concentrations were not different between herbage types. Grazed herbage DMI increased with increasing herbage allowance and this was associated with increased milk protein concentration (3.23 to 3.34%) and total casein production (41.7 to 43.6 mg/g). Concentrations of polyunsaturated fatty acids in milk fat, particularly linoleic acid, were increased in milk from cows offered the CHIC+ or the MIX diets, indicating potential benefits of chicory herbage on milk fatty acid concentrations. Although feeding CHIC+ or MIX did not increase milk yield, these herbage types could be used as an alternative to perennial ryegrass pasture in spring.     

Milk production of dairy cows fed wet corn gluten feed during the dry period and lactation

An experiment was conducted with 36 primiparous and 40 multiparous Holstein cows to examine the effects of feeding wet corn gluten feed (WCGF) on 305-d milk production, dry matter (DM) intake, body condition score (BCS), and health. The experimental treatments included: 1) control—WCGF not fed (n = 27); 2) WCGF-L—cows received diets containing WCGF (38% DM basis) during lactation (n = 23); and 3) WCGF-DL—cows received diets containing WCGF (38% DM basis) during the dry period and lactation (n = 26). During the dry period, cows consuming WCGF were observed to have a significant gain in BCS (0.07 ± 0.06) compared with a loss in BCS in cows fed the control diet (control = −0.11 ± 0.06 and WCGF-L = −0.04 ± 0.06). During lactation, there were no differences by treatment on BCS. Cows consuming WCGF during lactation consumed more feed compared with the control: 25.4, 23.8, and 21.2 ± 0.76 kg/d for WCGF-L, WCGF-DL, and the control, respectively. Milk production was higher for cows consuming WCGF: 35.0, 34.7, and 31.1 ± 2.1 kg/d for WCGF-L, WCGF-DL, and the control, respectively. No differences were found in either DM intake or actual milk yield between the WCGF-L and WCGF-DL treatments, indicating that prepartum diets did not influence lactational performance. The WCGF diets resulted in significant reductions in the concentration of milk fat (3.94, 3.74, and 4.15 ± 0.08% for WCGF-L, WCGF-DL, and the control, respectively), but because total milk yield was increased, there were no differences in total milk fat yield. In addition, 3.5% of fat-corrected milk tended to be affected by diet: 38.9, 36.3, and 34.7 ± 1.93 kg/d for WCGF-L, WCGF-DL, and the control, respectively. The increasing effect of DM intake and milk yield in cows consuming WCGF resulted in a similar efficiency of 3.5% fat-corrected milk production for all treatments, averaging 1.5 ± 0.09. Total protein yields were significantly higher for cows consuming WCGF diets during lactation: 1.15, 1.10, 1.00 ± 0.06 kg/d for WCGF-L, WCGF-DL, and the control, respectively. These results indicate that diets may be formulated to contain as much as 37.5% WCGF (DM basis).     

Short communication: Effects of molasses products on productivity and milk fatty acid profile of cows fed diets high in dried distillers grains with solubles

Previous research has shown that replacing up to 5% [of dietary dry matter (DM)] corn with cane molasses can partially alleviate milk fat depression when cows are fed high-concentrate, low-fiber rations containing dried distillers grains with solubles. The primary objective of this study was to determine whether dietary molasses alters milk fatty acid (FA) profile or improves solids-corrected milk yield in the context of a more typical lactation diet. A secondary objective was to assess production responses to increasing rumen-degradable protein supply when molasses was fed. Twelve primiparous and 28 multiparous Holstein cows (196 ± 39 d in milk) were blocked by parity and assigned to 4 pens. Pens were randomly allocated to treatment sequence in a 4 × 4 Latin square design, balanced for carryover effects. Treatment periods were 21 d, with 17 d for diet adaptation and 4 d for sample and data collection. Treatments were a control diet, providing 20% dried distillers grains with solubles (DM basis), 35% neutral detergent fiber, 30% starch, and 5% ether extract; a diet with 4.4% cane molasses replacing a portion of the corn grain; a diet with 2.9% molasses supplement containing 32% crude protein on a DM basis; and a diet with 5.8% (DM basis) molasses supplement. Animal-level data were analyzed using mixed models, including the fixed effect of treatment and the random effects of period, pen, period × pen interaction, and cow within pen to recognize pen as the experimental unit. Diets did not alter DM intake, milk production, milk component concentration or yield, feed efficiency (DM intake/milk yield), body weight change, or milk somatic cell count. Milk stearic acid content was increased by the diet containing 5.8% molasses supplement compared with the control diet and the diet containing 2.9% molasses supplement, but the magnitude of the effect was small (12.27, 11.75, and 11.69 ± 0.29 g/100 g of FA). Production data revealed a dramatic effect of period on milk fat content and yield. Milk fat content decreased during the course of the experiment (least squares means = 3.16, 2.81, 2.93, and 2.64 ± 0.09% for periods 1 to 4, respectively), as did milk fat yield (1.20, 1.03, 0.98, and 0.79 ± 0.05 kg/d). Exchanging molasses-based products for corn at 2.9 to 5.8% of dietary DM did not influence productivity and had minute effects on milk FA profile. The limited responses in this study may have been influenced by dietary unsaturated FA content or the advancing stage of lactation of cows in the study.     

Effect of the ratio of zinc amino acid complex to zinc sulfate on the performance of Holstein cows

Multiparous (n = 70) and primiparous (n = 66) Holstein cows were balanced by 305-d previous mature-equivalent milk yield and parity and assigned to 1 of 3 dietary treatments to evaluate the ratio of zinc sulfate to zinc amino acid complex (CZ) in pre- and postpartum Holstein cows fed diets containing 75 mg of added zinc/kg. Treatments were (1) 75 mg of supplemental zinc/kg of dry matter (DM) provided entirely as zinc sulfate (0-CZ); (2) 0-CZ diet, except 33.3 mg of zinc sulfate/kg of DM in the prepartum and 15.5 mg of zinc sulfate/kg of DM in the postpartum diet were replaced by CZ from Availa-Zn (16-CZ; Zinpro Corp., Eden Prairie MN); and (3) 0-CZ diet, except 66.6 mg of zinc sulfate/kg of DM in the prepartum and 40.0 mg of zinc sulfate/kg of DM in the postpartum diet was replaced by Availa-Zn (40-CZ). Cows were housed at the Iowa State University Dairy Farm and were individually offered a total mixed ration containing dietary treatments beginning at 28 ± 15 d before expected calving date until 250 d in milk. Relative to 0-CZ, multiparous cows (but not primiparous) fed CZ (16-CZ or 40-CZ) had increased (20%) colostrum IgG concentrations. Prepartum DM intake (DMI) was decreased with CZ supplementation. Postpartum DMI was decreased in cows fed CZ, whereas milk yield (MY) was increased in the 40-CZ-fed cows relative to those fed both 0-CZ and 16-CZ. Feed efficiency increased linearly when measured as MY/DMI, 3.5% fat-corrected MY/DMI, and solids-corrected MY/DMI. Regardless of level, feeding CZ decreased services per conception. Feeding 16-CZ decreased milk fat concentration and feeding CZ linearly increased milk urea nitrogen concentration. In summary, supplementing zinc as a mixture of CZ and zinc sulfate, as opposed to supplementing only zinc sulfate, has beneficial effects on production parameters in dairy cows, with those benefits becoming more apparent as the ratio of CZ to zinc sulfate increases.     

Effect of feeding a reduced-starch diet with or without amylase addition on lactation performance in dairy cows

The objective of this study was to determine lactation performance responses of high-producing dairy cows to a reduced-starch diet compared with a normal-starch diet and to the addition of exogenous amylase to the reduced-starch diet. Thirty-six multiparous Holstein cows (51 ± 22 DIM and 643 ± 49 kg of body weight at trial initiation) were randomly assigned to 1 of 3 treatments in a completely randomized design: a 3-wk covariate adjustment period during which the cows were fed the normal-starch diet, followed by a 12-wk treatment period during which the cows were fed their assigned treatment diets. The normal-starch TMR did not contain exogenous amylase (NS−). The reduced-starch diets, formulated by partially replacing corn grain with soy hulls, were fed without (RS−) and with (RS+) exogenous amylase added to the TMR. Starch and NDF concentrations averaged 27.1 and 30.6%, 21.8 and 36.6%, and 20.7 and 36.6% (dry matter basis) for the NS−, RS−, and RS+ diets, respectively. Dry matter intake for cows fed the RS− diet was 2.4 and 3.2 kg/d greater than for cows fed the NS− and RS+ diets, respectively. Intake of NDF ranged from 1.19 to 1.52% of body weight among the treatments, with the RS− diet being 28% greater than the NS− diet and 13% greater than the RS+ diet. Milk yield averaged 50.4 kg/d and was unaffected by treatment. Fat-corrected milk yield was 2.9 kg/d greater for cows fed the RS− diet than for cows fed the NS− diet. Body weight and body condition score measurements were unaffected by treatment. Fat-, solids-, and energy-corrected milk feed conversions (kilograms/kilogram of DMI) were 12 to 13% greater for cows fed the RS+ diet than for cows fed the RS− diet. Dry matter and nutrient digestibilities were lowest for cows fed the NS− diet and greatest for cows fed the RS+ diet, and were greater for cows fed the RS+ diet than for cows fed the RS− diet, with the exception of starch digestibility, which was similar. Greater conversion of feed to milk for dairy cows fed reduced-starch diets that include exogenous amylase may offer potential for improving economic performance.     

Short communication: Effect of a stable pen management strategy for precalving cows on dry matter intake, plasma nonesterified fatty acid levels, and milk production

During the close-up transition period, dairy cows are at risk for negative energy balance due to increasing energy demands and decreasing feed intake. This can result in postparturient health problems and decreased milk production after calving. Cows are frequently regrouped during this period, which can negatively affect feeding and resting behavior. The hypothesis was that housing in a stable pen during the close-up transition period should result in a more settled environment resulting in fewer displacements from the feed bunk, which would result in improved feed intake, energy balance [lower nonesterified fatty acid (NEFA) concentrations], and lactation performance. This study addresses precalving pen grouping strategies, which have the potential to affect feed intake and energy balance. A randomized complete block design with pen as the experimental unit was used to compare a stable (S) housing strategy (cows with similar calving dates added to a precalving pen at once) to the more traditional dynamic (D) housing strategy (cows added up to 2 times per week to a precalving pen). Twice-weekly blood samples were collected for NEFA analysis and cow interactions within the pen were observed. Dry matter intake (DMI), milk production, and postparturient health problems were recorded. Mean DMI for the duration of the 28 d of the study was not different (S: 25.5 ± 1.6 vs. D: 25.7 ± 1.0 kg/d), and when examined over time relative to calving, no treatment by time interaction was observed. Concentrations of NEFA were not different when cows initially entered the pens (S: 0.21 ± 0.10 vs. D: 0.18 ± 0.04 mEq/L) and remained not different for the time intervals closer to calving (d −9 to −14: S: 0.28 ± 0.09 vs. D: 0.21 ± 0.04; d −3 to −6: S 0.36 ± 0.10, D 0.32 ± 0.05 mEq/L). Pen grouping strategy did not affect DMI, plasma NEFA concentrations, or milk production.     

Effect of prepartum anionic supplementation on periparturient feed intake, health, and milk production

Our objectives were to determine if dietary cation-anion difference (DCAD) and source of anions influence periparturient feed intake and milk production of dairy cattle during the transition period. Diets differed in DCAD (cationic or anionic) and anionic supplement. The 4 diets used prepartum were (1) control [DCAD +20 mEq/100 g of dry matter (DM)], (2) Bio-Chlor (DCAD −12 mEq/100 g of DM; Church & Dwight Co. Inc., Princeton, NJ), (3) Fermenten (DCAD −10 mEq/100 g of DM; Church & Dwight Co. Inc.), and (4) salts (DCAD −10 mEq/100 g of DM). Urine pH was lower for cows that consumed an anionic diet prepartum compared with control. Prepartum diet had no effect on prepartum dry matter intake (DMI) of multiparous or primiparous cows. Postpartum DMI and milk yield for multiparous cows fed anionic diets prepartum were greater compared with those fed the control diet. Postpartum DMI and milk yield of primiparous cows were similar for prepartum diets. Feeding prepartum anionic diets did not affect plasma Ca at or near calving. However, cows fed anionic diets began their decline in plasma Ca later than control cows. Postpartum β-hydroxybutyrate and nonesterified fatty acids were lower for primiparous cows fed prepartum anionic diets compared with those fed the control diet. Prepartum and postpartum plasma glucose concentrations were not affected by prepartum diet for all cows. Liver triglyceride differed for parity by day. Parities were similar at 21 d prepartum, but at 0 d and 21 d postpartum, levels were greater for multiparous cows. Results indicate that decreasing the DCAD of the diet during the prepartum period can increase postpartum DMI and milk production of multiparous cows without negatively affecting performance of primiparous cows.     

Effects of an acute feed restriction at the onset of the seasonal breeding period on reproductive performance and milk production in pasture-grazed dairy cows

Reproduction and milk production responses were compared between dairy cows offered a high (HPA; n = 453 in 4 replicates) or low (LPA; n = 317 in 3 replicates) pasture allowance for the first 14 d after the planned start of mating (d 0 of experiment) in 2 seasonal, pasture-based dairy herds. Estimated pasture dry matter intake (DMI) between d −1 and 13 were 14.3 ± 2.8 and 8.0 ± 1.7 kg of DM/cow per day for HPA and LPA cows, respectively. The LPA cows produced 22% less energy-corrected milk during the 14-d feeding treatment period, and milk yield remained less in LPA cows at d 53 despite all cows receiving pasture allowances to support DMI of 16 kg of dry matter/cow per day from d 14 onwards. The 3-wk submission rate (percentage of cows inseminated at least once from d 0 to 20) and the 3- and 6-wk pregnancy rates of LPA cows (88, 45, and 71%, respectively) were lower than those of HPA cows (94, 53, and 78%, respectively), but conception rates to first (50%) or second (47%) service and final pregnancy rates (93%) did not differ between treatments. These results quantify the immediate and subsequent responses in reproductive performance and milk production to a severe restriction in DMI at the onset of a seasonal breeding period in pasture-grazed dairy cows.     

Effects of feeding three types of corn-milling coproducts on milk production and ruminal fermentation of lactating Holstein cattle

Two experiments were conducted to determine the effects of feeding 3 corn-milling coproducts on intake, milk production, ruminal fermentation, and digestibility of lactating Holstein cows. In experiment 1, three corn-milling coproducts were fed at 15% of the diet dry matter (DM) to 28 Holstein cows averaging (±SD) 625 ± 81 kg of body weight and 116 ± 33 d in milk to determine effects on DM intake and milk production. In experiment 2, the same rations were fed to 4 ruminally fistulated, multiparous Holstein cows averaging 677 ± 41 kg of body weight and 144 ± 5 d in milk to determine the effects on ruminal fermentation and digestibility. In both experiments, cows and treatments were assigned randomly in 4 × 4 Latin squares over four 21-d periods. Treatments were formulated by replacing portions of forage and concentrate feeds with 15% coproduct and included 1) 0% coproduct (control), 2) dried distillers grains plus solubles (DDGS), 3) dehydrated corn germ meal (germ), and 4) high-protein dried distillers grains (HPDDG). Feed intake was recorded daily, and milk samples were collected on d 19 to 21 of each period for analysis of major components. Rumen fluid was collected at 10 time points over 24 h post feeding on d 21 of experiment 2. In experiment 1, DM intake was greater for the germ (24.3 kg/d) and DDGS treatments (23.8 kg/d), but DDGS was not different from the control (22.9 kg/d) and HPDDG treatments (22.4 kg/d). Milk production paralleled DM intake and tended to be greater for the germ (32.1 kg/d) and DDGS treatments (30.9 kg/d), but the DDGS treatment was not different from the control (30.6 kg/d) and HPDDG treatments (30.3 kg/d). However, yields of milk fat, milk protein, and 3.5% FCM were similar and averaged (±SEM) 1.1 ± 0.1, 0.9 ± 0.03, and 31.7 ± 1.3 kg/d. Milk urea nitrogen was greater for the HPDDG (15.9 mg/dL) and germ treatments (15.5 mg/dL) than for the control (15.0 mg/dL) and DDGS treatments (14.9 mg/dL). In experiment 2, DM intake and milk production were not different across treatments and averaged 26.1 ± 2.3 and 28.3 ± 3.9 kg/d. Ruminal pH (6.26 ± 0.08) and total concentration of volatile fatty acids (125.3 ± 4.2 mM) were similar. Acetate concentration was higher for the control treatment than the DDGS, germ, and HPDDG treatments (81.7 vs. 75.8, 75.0, and 78.4 mM). Concentrations of propionate and butyrate were not different and averaged 27.8 ± 1.2 and 14.3 ± 0.9 mM across treatments. The acetate:propionate ratios for the control, germ, and HPDDG treatments were greater than for the DDGS treatment (3.02, 2.88, and 2.91 vs. 2.62). Dry matter, organic matter, and neutral detergent fiber digestibilities were similar across treatments and averaged 63.5 ± 2.7, 67.3 ± 2.2, and 43.5 ± 4.2%. Milk production followed DM intake in experiment 1, and yield of major milk components was not affected. Results of these experiments indicate that dairy rations can be successfully formulated to include 15% of diet DM as corn-milling coproducts while maintaining or increasing DM intakes and yields of milk and milk components.     

Extended negative dietary cation-anion difference feeding does not negatively affect postpartum performance of multiparous dairy cows

Low postpartum blood calcium remains one of the largest constraints to postpartum feed intake, milk yield, and energy balance in transitioning dairy cows. Supplemental dietary anions decrease the dietary cation-anion difference (DCAD) and reduce the risk for postpartum hypocalcemia. Prepartum management strategies aiming to minimize social stress and diet changes have resulted in a need to explore the effects of extended exposure to a negative DCAD (>21 d) diet. Holstein and Holstein-cross dairy cows (n = 60) were assigned to 1 of 3 treatments 42 d before expected calving to evaluate effects of supplying anions for 21 or 42 d during the dry period on energy status, postpartum production, and Ca homeostasis. Treatments included (1) a control diet (CON; DCAD = 12 mEq/100 g of DM), (2) a 21-d negative DCAD diet (21-ND; DCAD = 12 and −16 mEq/100 g of DM), and (3) a 42-d negative DCAD diet (42-ND; DCAD = −16 mEq/100 g of DM). Cows fed CON were fed positive DCAD prepartum for 42 d. Cows fed 21-ND received the positive DCAD (12 mEq/100 g of DM) diet for the first 21 d of the dry period and the anionic diet (−16 mEq/100 g of DM) from d 22 until calving. Cows fed 42-ND received the anionic diet for the entire dry period. Control and anionic diets were formulated by using 2 isonitrogenous protein mixes: (1) 97.5% soybean meal and (2) 52.8% BioChlor (Church & Dwight Co. Inc.), 45.8% soybean meal. Supplementing anions induced a mild metabolic acidosis, reducing urine pH for 21-ND and 42-ND compared with CON. Prepartum DMI was not different among treatments. Postpartum DMI was higher for 21-ND compared with CON (20.8 vs. 18.1 ± 1.1 kg/d), and 42-ND had similar DMI compared with 21-ND. During the first 56 d of lactation 21-ND had greater average milk production compared with CON (44.8 vs. 39.2 ± 2.1 kg/d). Average milk production by 42-ND was similar to 21-ND. Postpartum total blood Ca concentration was greater for 42-ND. Cows fed anionic diets prepartum tended to have lower lipid accumulation in the liver after calving compared with CON. These data suggest low-DCAD diets fed for 21 or 42 d during the dry period can have positive effects on postpartum DMI, Ca homeostasis, and milk production.     

Effects of a supplemental yeast culture on heat-stressed lactating Holstein cows

Multiparous, lactating Holstein cows (n = 23; 120 ± 30 d in milk, 690 ± 67 kg of body weight) housed in climatic chambers were randomly assigned to 1 of 2 dietary treatments: a diet containing a novel yeast culture formulation (YC) for heat stress (n = 12, 10 g/d) or a control diet (n = 11). The trial length was 28 d and consisted of a 7-d thermal neutral period (TN; 18°C, 20% humidity) followed by 21 d of heat stress (HS; cyclical daily temperatures ranging from 29.4 to 37.8°C and 20% humidity). Cows were individually fed a total mixed ration consisting primarily of alfalfa hay and steam-flaked corn. During TN, the YC feeding had no effect on production variables or most body temperature indices. During HS, all body temperature indices increased and YC had no effect on rump surface temperature, respiration rate, or sweating rates. Cows fed YC had lower rectal temperatures at 1200 and 1800 h (40.29 vs. 40.02°C and 40.35 vs. 40.12 ± 0.07°C, respectively) compared with control-fed cows. Cows fed both diets lost body weight (42 kg) during HS, but there were no differences between diets. Control-fed cows had increased dry matter intake (DMI) and milk yield (19.1 vs. 17.9 ± 0.5 kg/d and 32.15 vs. 29.15 ± 0.02 kg/d, respectively) compared with YC-fed cows, but intake and milk production were similar between diets when evaluated on a body weight basis. Heat stress progressively decreased DMI (29%) and milk yield, with milk production reaching a nadir (33%) in the third week. Heat stress decreased milk protein (7%) and lactose (5%) levels, but did not alter milk fat content. Heat-stressed cows were in calculated negative energy balance (−1.91 ± 0.70 Mcal/d) and this was unaffected by diet. Independent of diet, HS decreased plasma glucose (11%), but neither diet nor HS altered basal nonesterified fatty acid levels. Heat stress increased plasma urea N concentrations (11.5 vs. 14.8 ± 0.4 mg/dL). Despite YC-fed cows having slightly reduced body temperatures indices, feeding YC did not prevent the negative effects of HS.     

Influence of a reduced-starch diet with or without exogenous amylase on lactation performance by dairy cows

The objective of this trial was to determine lactation performance responses in high-producing dairy cows to a reduced-starch versus a normal-starch diet and to the addition of exogenous amylase to the reduced-starch diet. Forty-five multiparous Holstein cows, 68 ± 29 d in milk and 696 ± 62 kg of body weight (BW) at trial initiation, were randomly assigned to 1 of 3 treatments in a completely randomized design; a 2-wk covariate adjustment period with cows fed the normal-starch diet was followed by a 10-wk treatment period with cows fed their assigned treatment diets. The normal-starch total mixed ration did not contain exogenous amylase (NS−). The reduced-starch diets, formulated by partially replacing corn grain and soybean meal with whole cottonseed and wheat middlings, were fed without (RS−) and with (RS+) exogenous amylase addition to the total mixed ration. All diets contained 50% forage and 19.8% forage neutral detergent fiber (dry matter basis). Starch and neutral detergent fiber concentrations averaged 27.0 and 30.9%, 22.1 and 35.0%, and 21.2 and 35.3% (dry matter basis) for the NS−, RS−, and RS+ diets, respectively. Expressed as a percentage of BW, dry matter intake was greater for cows fed RS− than for cows fed NS− or RS+. Intake of neutral detergent fiber ranged from 1.09 to 1.30% of BW among the treatments, with that of RS− being 21% greater than that of NS−. Milk yield tended to be greater for cows fed NS− compared with the RS diets. Milk fat content and yield were unaffected by treatment. Milk protein content and yield were greater for cows fed NS− compared with the RS diets. Concentrations of milk urea nitrogen were greater for cows fed RS diets compared with the NS− diet. Body weight, BW change, and body condition score were unaffected by treatment. Feed conversion (kg of milk/kg of dry matter intake) was 10% greater on average for cows fed NS− than for cows fed the RS diets, and tended to be 6% greater for cows fed RS+ compared with RS−. Feeding a reduced-starch diet formulated by partially replacing corn grain and soybean meal with a wheat middlings and whole cottonseed mixture compared with a normal-starch diet without addition of exogenous amylase to either diet reduced milk and component-corrected feed conversions. Addition of exogenous amylase to a reduced-starch diet was of minimal benefit in this study.     

Short communication: Effect of increasing levels of corn bran on milk yield and composition

Thirty-nine lactating Holstein cows (23 multiparous and 16 primiparous) were randomly assigned to 1 of 3 dietary treatments in a crossover design. Dietary treatments differed by the proportion of corn bran [10, 17.5, and 25% dry matter (DM); designated as low, medium, and high] replacing corn silage and alfalfa. The corn bran coproduct contained 8.2% moisture and 12.9% crude protein, 30.4% neutral detergent fiber (NDF), and 45.0% nonfiber carbohydrate, 9.9% ether extract, and 0.70% P (DM basis). The low treatment consisted of 15.8% NDF from forage (fNDF) and 33.1% total NDF; the medium treatment consisted of 12.9% fNDF and 32.5% total NDF; and the high diet contained 9.9% fNDF and 31.8% total NDF. Dry matter intake was not affected by treatment. The percent milk fat decreased by 0.26% with the inclusion of corn bran from 10 to 25% of the diet DM, but total milk fat yield was not affected. In comparison, corn bran increased yield of milk protein 0.12 kg/d when bran increased from 10 to 25% of the diet DM. Total milk yield tended to increase when bran increased from 10 to 25% of the diet DM, but no differences were observed on 3.5% fat-corrected milk. Lastly, feed conversion significantly improved with increasing inclusion: 1.39, 1.39, and 1.55 ± 0.05 kg of milk/kg of DMI for low, medium, and high, respectively. Observed effects were likely due to the increase in energy intake associated with increasing levels of corn bran.     

Effect of monensin in lactating dairy cow diets at 2 starch concentrations

The objective of this study was to determine the effects of monensin (M) supplementation on lactation performance of dairy cows fed diets of either reduced (RS) or normal (NS) starch concentrations as total mixed rations. One hundred twenty-eight Holstein and Holstein × Jersey cows (90 ± 33 d in milk) were stratified by breed and parity and randomly assigned to 16 pens of 8 cows each in a randomized controlled trial. Pens were then randomly assigned to 1 of 4 treatments in a 2 × 2 factorial arrangement of treatments. A 4-wk covariate adjustment period preceded the treatment period, with all pens receiving NS supplemented with 18 g of monensin/t of dry matter (DM). Following the 4-wk covariate adjustment period, cows were fed their assigned treatment diets of NS with M (18 g of monensin/t), NS with 0 g of monensin/t (C), RS with M, or RS with C for 12 wk. Actual starch concentrations for the RS and NS diets were 20.4 and 26.9% (DM basis), respectively. Mean dry matter intake (DMI; 27.0 kg/d) was unaffected by the treatments. Feeding M compared with C and NS compared with RS increased milk yield by 1.3 and 1.5 kg/d per cow, respectively. Milk protein percentage and yield and lactose yield were increased and milk urea nitrogen was decreased for NS compared with RS. Feeding M increased actual and component-corrected milk feed efficiencies (component-corrected milk yield/DMI) and lactose yield and tended to increase milk urea nitrogen compared with C. Milk protein percentage was decreased for M compared with C, but milk fat percentage and yield, protein yield, and lactose percentage were unaffected by M. We observed a tendency for a starch × monensin interaction for milk feed efficiency (actual milk yield/DMI); M tended to increase efficiency more for NS than for RS. Starch and monensin had minimal effects on milk fatty acid composition and yields. Feeding RS decreased milk and protein yields, but component-corrected milk yields and feed efficiencies were similar for RS and NS. Monensin increased feed efficiency and lactation performance for both dietary starch concentrations.     

Evaluation of potential carryover effects associated with limit feeding of gravid Holstein heifers

Ninety-six Holstein heifers (400 ± 6 kg, 15.2 ± 0.1 mo), including 9 with ruminal cannulas, were offered 1 of 3 diets for 180 ± 8 d in a randomized replicated pen design. Dietary treatments included a control diet (C100) and 2 independent limit-fed (LF) diets. The LF diets included one offered at 85% of C100 intake (L85) without an ionophore, and a second containing an ionophore (325 mg/head per day of lasalocid) that was offered at 80% of C100 intake (L80+I). Heifers were evaluated for growth, rumen digesta volume, nutrient excretion, and subsequent lactation performance. Limit-fed heifers consumed less dry matter and neutral detergent fiber, and had greater respective average daily gains (0.96 or 0.89 vs. 0.81 kg/d), and lower feed:gain ratios (9.1 or 9.3 vs. 13.0 kg/kg) compared with heifers offered the C100 diet. No differences in rumen pH, NH₃-N, or volatile fatty acid concentrations were observed between C100 and LF heifers. Rumen digesta volume, density, and weight were unaffected by LF, and feeding L85 or L80+I did not result in carryover effects for rumen digesta volume when these heifers were offered a common high-fiber diet immediately after the 180-d growth trial. At parturition, no differences were observed for dystocia index, calf body weight, or 7-d postpartum body weight between cows offered LF or C100 diets as heifers. Lactation body weight, dry matter intake, and feed efficiency of cows did not differ between treatments at 45 or 90 d in milk. Milk yield and milk components also were not different between cows that were offered C100 or LF diets as gravid heifers. At 45 d in milk, rumen digesta volume was greater (99.1 vs. 66.1 L) for cows offered L85 compared with cows offered L80+I as gravid heifers, but this effect was not observed at 90 d in milk. Limit feeding of gravid Holstein heifers for 180 d did not result in any carryover effects during their first lactation for rumen digesta volume, dry matter intake, or milk yield.     

Nutrient demand interacts with forage family to affect intake and digestion responses in dairy cows

The effect of feed intake in the preliminary period on responses to diets containing alfalfa silage or orchardgrass silage was evaluated using 8 ruminally and duodenally cannulated Holstein cows in a crossover design experiment with a 14-d preliminary period and two 15-d treatment periods. Responses measured were DMI, rates of fiber digestion and passage, and milk production. Cows were 139 ± 83 (mean ± SD) d in milk at the beginning of the preliminary period. During the preliminary period, 3.5% fat-corrected milk yield ranged from 23.9 to 47.6 kg/d (mean = 36.9 kg/d) and preliminary voluntary DMI (pVDMI) ranged from 14.2 to 21.3 kg/d (mean = 18.6 kg/d). The 2 treatments were a diet containing alfalfa silage as the sole forage (AL) and a diet containing orchardgrass silage as the sole forage (OG). Alfalfa silage contained 43% neutral detergent fiber (NDF; dry-matter basis) and orchardgrass silage contained 48% NDF; diets contained ∼23% forage NDF and 27% total NDF, so forage-to-concentrate ratio was 53:47 for AL and 48:52 for OG. Digestibility of NDF was lower for AL in the rumen and whole tract compared with OG, and milk fat concentration tended to be greater for OG than for AL. Mean 3.5% fat-corrected milk yield and DMI were not different between AL and OG. Response of DMI to forage family depended on pVDMI, as indicated by a significant interaction between treatment and pVDMI in predicting DMI. As pVDMI increased, DMI increased when cows were fed AL but not when they were fed OG. That is, as appetite increased, intake was more restricted for the more physically filling OG than for the less physically filling AL. This more positive DMI response to AL over OG among high-pVDMI cows is corroborated by interactions between treatments and pVDMI for both ruminal NDF turnover rate and indigestible NDF passage rate response. Therefore, the effects of alfalfa and orchardgrass forages on intake and fiber digestion depended on the extent to which fill limited feed intake of an individual cow.     

Effects of supplemental chromium propionate and rumen-protected amino acids on productivity,diet digestibility,and energy balance of peak-lactation dairy cattle

Chromium (Cr) feeding in early lactation increased milk production in some studies, but responses to dietary Cr during peak lactation have not been evaluated. Furthermore, interactions of essential amino acids (AA) and Cr have not been explored. Our objective was to evaluate responses to CrPr (KemTRACE chromium propionate 0.04%, Kemin Industries Inc., Des Moines, IA) and rumen-protected Lys (LysiPEARL, Kemin Industries Inc.) and Met (MetiPEARL, Kemin Industries Inc.) and their interaction in peak-lactation cows. Forty-eight individually fed Holstein cows (21 primiparous, 27 multiparous, 38 ± 15 d in milk) were stratified by calving date in 12 blocks and randomly assigned to 1 of 4 treatments within block. Treatments were control, CrPr (8 mg/d of Cr), RPLM (10 g/d of Lys and 5 g/d of Met, intestinally available), or CrPr plus RPLM. Treatments were premixed with ground corn and top-dressed at 200 g/d for 35 d. Diets consisted of corn silage, alfalfa hay, and concentrates, providing approximately 17% crude protein, 31% neutral detergent fiber, and 40% nonfiber carbohydrates. Dry matter intake (DMI) significantly increased with the inclusion of CrPr (22.2 vs. 20.8 ± 0.67 kg/d), and energy-corrected milk (ECM) yield tended to increase. In addition, CrPr increased milk protein yield and tended to increase DMI in primiparous cows but not in multiparous cows. A CrPr × week interaction was detected for milk lactose content, which was increased by CrPr during wk 1 only (4.99 vs. 4.88 ± 0.036%). As a proportion of plasma AA, lysine increased and methionine tended to increase in response to RPLM, but the inclusion of RPLM decreased N efficiency (milk protein N:N intake). Digestible energy intake, gross energy digestibility, and energy balance were not affected by treatments. We observed no treatment effects on feed efficiency or changes in body weight or body condition score. In summary, feeding CrPr increased DMI and tended to increase ECM in cows fed for 5 wk near peak lactation, with primiparous cows showing greater responses in DMI and milk protein yield than multiparous cows.