Effect of trace mineral source on lactation performance, claw integrity, and fertility of dairy cattle

Two hundred fifty multiparous and primiparous cows were assigned to a study at approximately 70 d prepartum to determine the effect of trace mineral source on lactation performance, claw integrity, and fertility. Cows received treatments from 3 wk prepartum through wk 35 postpartum. Treatments consisted of 1) all supplemental Zn, Mn, Cu, and Co provided in sulfate form (Sulfate) and 2) 360 mg of Zn, 200 mg of Mn, 125 mg of Cu, and 12 mg of Co supplied daily by Sulfate minerals replaced with similar amounts of minerals supplied by Availa-4 (CTM). Individuals involved with daily animal care or data recording, or both, were blinded to treatment assignments. Cows from all treatments were housed in common pens, and treatments were dispensed to cows via a computerized feeder. All claws of cows were examined before treatment administration and at 16 and 36 wk postpartum by personnel trained in identifying claw lesions. Cows fed the CTM diet tended to produce more milk and energy-corrected milk than cows fed the Sulfate diet. Cows fed the CTM diet also produced more milk protein and solids (fat + protein) than cows fed the Sulfate diet. Replacing Sulfate minerals with those supplied by CTM decreased incidence of sole ulcers at wk 36 postpartum and tended to decrease incidence of interdigital dermatitis at wk 16 and 36 postpartum. Severity of heel erosion tended to be less for cows fed CTM than cows receiving the Sulfate diet. Despite first service conception rates tending to be greater for cows fed the Sulfate diet, there was no effect of treatment on rate of conception. A greater percentage of cows fed the Sulfate diet tended to be culled from the herd before wk 36 postpartum than cows fed the CTM diet. Replacing Sulfate minerals with CTM resulted in improved lactation performance and claw integrity.     

Immune responses in lactating Holstein cows supplemented with Cu, Mn, and Zn as sulfates or methionine hydroxy analogue chelates

The aim of this study was to compare effects of inorganic sulfate versus chelated forms of supplemental Cu, Mn, and Zn on milk production, plasma and milk mineral concentrations, neutrophil activity, and antibody titer response to a model vaccination. Holstein cows (n=25) were assigned in 2 cohorts based on calving date to a 12-wk randomized complete block design study. The first cohort consisted of 17 cows that had greater days in milk (DIM; mean of 77 DIM at the start of the trial) than the second cohort of 8 cows (32 DIM at the start of the trial). Diets were formulated to supplement 100% of National Research Council requirements of Cu, Mn, and Zn by either inorganic trace minerals (ITM) in sulfate forms or chelated trace minerals (CTM) supplied as metal methionine hydroxy analog chelates, without accounting for trace mineral contribution from other dietary ingredients. Intake and milk production were recorded daily. Milk composition was measured weekly, and milk Cu, Mn, and Zn were determined at wk 0 and 8. Plasma Cu and Zn concentrations and neutrophil activity were measured at wk 0, 4, 8, and 12. Neutrophil activity was measured by in vitro assays of chemotaxis, phagocytosis, and reactive oxygen species production. A rabies vaccination was administered at wk 8, and vaccine titer response at wk 12 was measured by both rapid fluorescent focus inhibition test and ELISA. Analyzed dietary Cu was 21 and 23mg/kg, Mn was 42 and 46mg/kg, and Zn was 73 and 94mg/kg for the ITM and CTM diets, respectively. No effect of treatment was observed on milk production, milk composition, or plasma minerals. Dry matter intake was reduced for CTM compared with ITM cows, but this was largely explained by differences in body weight between treatments. Milk Cu concentration was greater for CTM than ITM cows, but this effect was limited to the earlier DIM cohort of cows and was most pronounced for multiparous compared with primiparous cows. Measures of neutrophil function were unaffected by treatment except for an enhancement in neutrophil phagocytosis with the CTM treatment found for the later DIM cohort of cows only. Rabies antibody titer in CTM cows was 2.8 fold that of ITM cows as measured by ELISA, with a trend for the rapid fluorescent focus inhibition test. Supplementation of Cu, Mn, and Zn as chelated sources may enhance immune response of early lactation dairy cows compared with cows supplemented with inorganic sources.     

Effect of additional cobalt, copper, manganese, and zinc on reproduction and milk yield of lactating dairy cows receiving bovine somatotropin.

The objective of this study was to determine whether organically complexed Co, Cu, Mn, and Zn would improve the reproductive performance and milk and milk component production in lactating dairy cows that began receiving bovine somatotropin in the ninth week of lactation. Holstein (n = 50) and Jersey (n = 10) cows were blocked by breed, lactation number, and incidence of retained fetal membranes. Two diets assigned within blocks and fed from parturition until 154 d of lactation were control or control supplemented daily with 26 mg of Co as Co glucoheptonate, 125 mg of Cu as Cu-Lys, 199 mg of Mn as Mn-Met, and 359 mg of Zn as Zn-Met. Cows were fitted with electronic pressure-sensing devices in the second week of lactation for detection of estrus. Ovarian structures were determined via transrectal ultrasonography at 7-d intervals from parturition until observation of the first corpus luteum. Blood samples were taken at 7-d intervals and analyzed for plasma concentrations of progesterone, insulin, and urea nitrogen. Onset of luteal activity was identified by progesterone concentrations > or = 1 ng/ml. Retained fetal membranes increased days to first estrus (detected via electronic estrous detection), first luteal activity, and first corpus luteum in control cows but not in supplemented cows. Days to first observed estrus were greater for control cows than for supplemented cows. Days to first service, days open, days from first service to conception, services per conception, milk yield, milk components, and somatic cell counts were similar for control and supplemented cows. Supplementation with complexed trace minerals effectively reduced days to first estrus.     

Outdoor grazing of dairy cows on pasture versus indoor feeding on total mixed ration: Effects on gross composition and mineral content of milk during lactation

The influence of feeding system and lactation period on the gross composition, macroelements (Ca, P, Mg, and Na), and trace elements (Zn, Fe, Cu, Mo, Mn, Se, and Co) of bovine milk was investigated. The feeding systems included outdoor grazing on perennial ryegrass pasture (GRO), outdoor grazing on perennial ryegrass and white clover pasture (GRC), and indoors offered total mixed ration (TMR). Sixty spring-calving Holstein Friesian dairy cows were assigned to 3 herds, each consisting of 20 cows, and balanced with respect to parity, calving date, and pre-experimental milk yield and milk solids yield. The herds were allocated to 1 of the 3 feeding systems from February to November. Milk samples were collected on 10 occasions over the period June 17 to November 26, at 2 or 3 weekly intervals, when cows were on average 119 to 281 d in lactation (DIL). The total lactation period was arbitrarily sub-divided into 2 lactation periods based on DIL, namely mid lactation, June 17 to September 9 when cows were 119 to 203 DIL; and late lactation, September 22 to November 26 when cows were 216 to 281 DIL. With the exception of Mg, Na, Fe, Mo, and Co, all other variables were affected by feeding system. The GRO milk had the highest mean concentrations of total solids, total protein, casein, Ca, and P. The TMR milk had the highest concentrations of lactose, Cu, and Se, and lowest level of total protein. The GRC milk had levels of lactose, Zn, and Cu similar to those of GRO milk, and concentrations of TS, Ca, and P similar to those of TMR milk. Lactation period affected all variables, apart from the concentrations of Fe, Cu, Mn, and Se. On average, the proportion (%) of total Ca, P, Zn, Mn, or Se that sedimented with the casein on high-speed ultracentrifugation at 100,000 × g was ≥60%, whereas that of Na, Mg, or Mo was ≤45% total. The results demonstrate how the gross composition and elemental composition of milk can be affected by different feeding systems.     

Feeding reduced levels of trace minerals in proteinate form and selenium-yeast to transition cows: Performance,trace minerals,and antioxidant status,peripheral neutrophil activity,and oocyte quality

An experiment was conducted to evaluate the effects of inorganic trace minerals (TM) and reduced levels of TM by using proteinate forms of Co, Zn, Mn, and Cu, and Se-yeast in diets of transition cows on performance, TM concentrations in colostrum, plasma, and liver, blood metabolites, antioxidant status, peripheral neutrophil activity, and oocyte quality. Thirty-two Holstein cows (22 multiparous and 10 primiparous cows) were enrolled in this study from 30 d before the expected calving date to 56 DIM. Cows were blocked according to body condition score, parity, and previous milk yield and randomly assigned to one of the following treatments: control (CON), with TM (Zn, Cu, Mn, and Co) supplied in form of sulfate and Se as sodium selenite to meet or exceed requirement estimates of the National Research Council; and proteinate trace minerals (PTM), with TM supplied bound with AA and peptides at 50% of CON levels and inorganic Se replaced with Se-yeast at 100% of CON level. Treatments were supplied until 56 DIM. Eight cows were removed from the study because of early calving (n = 3) or health issues (n = 5); thus, data of 24 cows (16 multiparous and 8 primiparous cows) were used in the statistical analysis. No differences between treatments were detected on nutrient intake or digestibility. Total excretion of purine derivatives was decreased when feeding PTM during the prepartum period. Feeding reduced levels of TM in proteinate form resulted in greater yield of milk (27.7 and 30.9 kg/d for CON and PTM, respectively) and protein (0.890 and 0.976 kg/d) between wk 5 and 8 of lactation. No treatment differences were detected for feed efficiency, milk somatic cell count, and milk urea nitrogen. Cows fed PTM had lower milk fat concentration during the 56 d of evaluation (4.08 and 3.74% for CON and PTM, respectively). Selenium concentration was greater in colostrum of cows fed PTM compared with CON (48.5 and 71.3 µg/L for CON and PTM, respectively), whereas Zn, Cu, and Mn concentrations were not different. Cows fed PTM showed lower liver Cu concentration compared with CON (51.4 and 73.8, respectively). Plasma concentrations of Mn and Zn were lower, but plasma Se concentration tended to be higher with PTM treatment. Feeding PTM resulted in greater blood concentrations of urea-N (16.6 and 18.2 mg/dL for CON and PTM, respectively) and β-hydroxybutyrate (0.739 and 0.940 mmol/L). Counts of lymphocytes were higher with PTM but counts of monocytes were lower in complete blood cell count. No differences were observed in serum concentrations of superoxide dismutase and glutathione peroxidase. No differences were detected in phagocytosis and oxidative burst potential of neutrophils after incubation with bacteria. Cows fed PTM had fewer viable oocytes per ovum pick-up in comparison with CON (8.00 and 11.6). Feeding PTM to transition cows may sustain performance without altering neutrophil activity despite some alterations in blood TM concentrations. More studies should be performed to evaluate production and fertility measurements when reducing TM dietary levels by using proteinate forms and Se-yeast with larger number of animals.     

Effects of prepartum dietary protein level and feed intake on postpartum lactation performance and feeding behavior of multiparous Holstein dairy cows

An experiment was conducted to determine the effects of low and high metabolizable protein (MP) diets when fed for ad libitum and controlled intake during the prepartum period on postpartum lactation performance and feeding behavior of dairy cows. Thirty-six multiparous Holstein cows were blocked by parity, expected calving date, and previous lactation milk yield at −21 d relative to expected calving and were randomly assigned to 1 of 4 close-up period dietary treatments providing low MP (LMP) or high MP (HMP) diets with controlled intake (CNI) or ad libitum intake (ALI). The concentrations of MP were 65 and 90 g/kg dry matter for LMP and HMP diets, respectively, whereas intake was controlled to supply 100 and 160% of the NRC (2001) energy requirements for CNI and ALI groups, respectively. The concentration of net energy for lactation (NE_L) in the treatment diets was 1.50 Mcal/kg. All cows were fed a similar lactation diet after calving (1.50 Mcal/kg of NE_L and 83.3 g/kg of MP). The HMP diet increased dry matter intake during the first 3 wk and tended to increase dry matter intake over the 9 wk of lactation. Meal size and eating rate increased in the ALI cows during the prepartum period. Meal frequency increased with the HMP diet during the postpartum period. Milk yield increased by 15.2% with the HMP diet over the 9 wk of lactation. The HMP diet increased energy-corrected milk (ECM) yield in CNI versus ALI cows, whereas the LMP diet increased ECM yield in ALI versus CNI cows over the 9 wk of lactation. The increase in ECM yield of LMP-ALI versus LMP-CNI cows was supported by greater body condition loss and serum β-hydroxybutyrate over the 9 wk of lactation. Taken together, these data indicate that prepartum controlled intake of a high protein diet can provide the benefits of both strategies.     

Short communication: Effects of supplementing diets of Holsteins with copper,zinc, and manganese on blood neutrophil function

The effects of supplementing diets with sulfate or glycinate Cu, Zn, and Mn on blood neutrophil function were examined in 27 late-lactation Holstein cows having a mean (± standard deviation) days in milk at time of neutrophil assays of 216 ± 31 d. Cows were assigned to 9 blocks of 3 and were grouped by parity, milk production, and days in milk. Cows within each block were randomly assigned to 1 of 3 treatments: (1) control diet devoid of supplemental Cu, Zn, and Mn; (2) diet supplemented with Cu, Zn, and Mn via sulfates; and (3) diet supplemented with Cu, Zn, and Mn via glycinate form. All cows were initially fed a control total mixed ration with basal mineral concentrations of 8 mg/kg of Cu, 35 mg/kg of Zn, and 35 mg/kg of Mn for 30 d. During the treatment period, cows fed diets with mineral supplementation via sulfates or glycinate forms had target total dry matter dietary concentrations of 18 mg/kg of Cu, 60 mg/kg of Zn, and 60 mg/kg of Mn for 30 d. Control cows were fed the control diet devoid of supplemental minerals for an additional 30 d. In vitro neutrophil functions were measured after 30 d on experimental or control diets. Percentage of neutrophils phagocytizing, intracellular kill, and phagocytic index did not differ among treatments. Serum concentrations of Cu, Zn, and Mn were also not affected by dietary treatment after 30 d. Results from this study demonstrated that dietary Cu, Zn, and Mn supplemented either as sulfates or glycinate form for 30 d had no effect on either in vitro blood neutrophil function or serum concentrations of Cu, Zn, and Mn in late-lactation Holstein cows.     

Diets during far-off and close-up dry periods affect periparturient metabolism and lactation in multiparous cows

The objectives of this study were to determine the effects of far-off and close-up diets on prepartum metabolism, postpartum metabolism, and postpartum performance of multiparous Holstein cows. From dry-off to −25 d relative to expected parturition (far-off dry period), cows were fed a control diet to meet National Research Council (NRC) recommendations for net energy for lactation (NE_L) at ad libitum intake (100NRC; n = 25) or a higher nutrient density diet, which was fed for either ad libitum intake to provide at least 150% of calculated NE_L requirement (150NRC; n = 25) or at restricted intake to provide 80% of calculated NE_L requirements (80NRC; n = 24). From −24 d relative to expected parturition until parturition (close-up period), cows were fed a diet that met or exceeded NRC nutrient recommendations at either ad libitum intake (n = 38) or restricted intake (n = 36) to provide 80% of the calculated NE_L requirement. After parturition, all cows were fed a lactation diet and measurements were made through 56 d in milk (DIM). Prepartum metabolism was consistent with the plane of nutrition. During the first 10 DIM, far-off treatments had significant carryover effects on dry matter intake, energy balance, serum nonesterified fatty acid (NEFA) concentration, and serum β-hydroxybutyrate concentration. Cows with the lower energy balance during the far-off period (100NRC and 80NRC) had higher dry matter intake and energy balance and lower serum NEFA and β-hydroxybutyrate during the first 10 DIM. There were no effects of close-up diet and no interactions of far-off and close-up treatments. During the first 56 DIM, there were no residual effects of far-off or close-up diets on dry matter intake, milk yield or composition, body weight, body condition score, serum glucose and insulin concentrations, or muscle lipid concentration. Serum NEFA was higher for 150NRC than 80NRC; 100NRC was intermediate. Thus, the effects of far-off and close-up treatments on postpartum variables diminished as lactation progressed. Overfeeding during the far-off period had a greater negative impact on peripartum metabolism than did differences in close-up period nutrition.     

Lactational performance and plasma and muscle amino acid concentrations in dairy cows fed diets supplying 2 levels of digestible histidine and metabolizable protein

The objective of this experiment was to investigate the effect of dietary levels of digestible histidine (dHis) and MP on lactational performance and plasma and muscle concentrations of free AA in dairy cows. A randomized block design experiment was conducted with 48 Holstein cows, including 20 primiparous, averaging (±SD) 103 ± 22 d in milk and 45 ± 9 kg/d milk yield at the beginning of the experiment. A 2-wk covariate period preceded 12 experimental wk, of which 10 wk were for data and sample collection. Experimental treatments were (1) MP-adequate (MPA) diet with 2.1% dHis of MP (MPA2.1), (2) MPA with 3.0% dHis (MPA3.0), (3) MP-deficient (MPD) diet with 2.1% dHis (MPD2.1), and (4) MPD with 3.0% dHis (MPD3.0). Actual dHis supply was estimated at 64, 97, 57, and 88 g/d, respectively. Diets supplied MP at 110% (MPA) and 96% (MPD) of NRC 2001 dairy model requirements calculated based on DMI and production data during the experiment. Dry matter intake and milk yield data were collected daily, milk samples for composition and blood samples for AA analysis were collected every other week, and muscle biopsies at the end of covariate period, and during wk 12 of the experiment. The overall DMI was not affected by dHis or MP level. Milk yield tended to be increased by 3.0% dHis compared with 2.1% dHis. Milk true protein concentration and yield were not affected by treatments, whereas milk urea nitrogen concentration was lower for MPD versus the MPA diet. Milk fat concentration was lower for MPD versus MPA. There was a MP × dHis interaction for milk fat yield and energy-corrected milk; milk fat was lower for MPD3.0 versus MPD2.1, but similar for cows fed the MPA diet regardless of dHis level whereas energy-corrected milk was greater for MPA3.0 versus MPA2.1 but tended to be lower for MPD3.0 versus MPD2.1. Plasma His concentration was greater for cows fed dHis3.0, and concentration of sum of essential AA was greater, whereas carnosine, 1-Methyl-His and 3-Methyl-His concentrations were lower for cows fed MPA versus MPD diet. Muscle concentration of His was greater for cows fed dHis3.0 treatment. The apparent efficiency of His utilization was increased at lower MP and His levels. Overall, cows fed a corn silage-based diet supplying MP at 110% of NRC (2001) requirements tended to have increased ECM yield and similar milk protein yield to cows fed a diet supplying MP at 96% of requirements. Supplying dHis at 3.0% of MP (or 86 and 96 g/d, for MPD3.0 and MPA3.0, respectively) tended to increase milk yield and increased plasma and muscle concentrations of His but had minor or no effects on other production variables in dairy cows.     

Effect of replacing a portion of inorganic chloride trace minerals with trace mineral amino acid complexes

The objective was to determine whether replacing a portion of inorganic chloride trace minerals and cobalt carbonate in the diet with AA complexes of trace minerals and cobalt glucoheptonate will improve lactating cow performance, feed efficiency, and calf performance. In a clinical trial, 69 Holstein cows entering second lactation and greater were randomly assigned to 1 of 2 treatments, with the total dietary trace mineral concentration the same between treatments, starting 1 wk after dry off (50 to 57 d before expected parturition) until 154 d in milk (DIM): (1) an inorganic chloride trace mineral (ITM) blend consisting of Zn (75 mg/kg), Mn (65 mg/kg), and Cu (10 mg/kg) as hydroxychlorides and Co (1 mg/kg) as carbonate (n = 37) or (2) partial replacement of ITM with AA complexes of Zn (40 mg/kg), Mn (20 mg/kg), and Cu (3.5 mg/kg) and Co glucoheptonate (1 mg/kg; AATM; Availa-Dairy, Zinpro Corp.; n = 32). Dry matter intake (DMI) was recorded daily from enrollment through wk 8, and milk yields were recorded daily from calving through wk 22. Milk composition and body weights (BW) were collected weekly. Serum samples were analyzed for albumin (Alb), cholesterol (Chol), total bilirubin (Bili), aspartate aminotransferase (AST), haptoglobin, β-hydroxybutyrate (BHB), and Ca. A liver health index (LHI) was calculated based on Bili, Chol, and Alb concentrations. A liver functionality index (LFI) was calculated to standardize changes in Alb, Chol, and Bili from 4 to 29 DIM. Greater LHI and LFI indicate better health status. Colostrum was analyzed for IgG and Brix, and calf serum was analyzed for IgG. Calf growth was monitored through 9 wk of age (AATM: n = 12, ITM: n = 10). Data were analyzed using SAS software with mixed effects models and repeated-measures analysis, when applicable. Survival analysis for pregnancy by 154 DIM was analyzed by Cox proportional and Kaplan-Meier hazards models. Disorder incidence was tested with Fisher's exact test. Prepartum DMI as a percent of BW was lower in cows fed AATM and not significant postpartum. Cows fed AATM produced more milk from wk 1 to 8 and from wk 1 to 22. Energy-corrected milk yield and colostrum measures did not significantly differ between treatments. A treatment by time interaction was seen for AST and BHB; cows fed AATM tended to have lower AST concentrations at 28 DIM and lower concentrations in BHB through 29 DIM, though not statistically significant. Cows fed AATM had greater LHI at 4 DIM. Haptoglobin, Ca, LFI, hazard of pregnancy, risk to first service, survival curves, or services per pregnancy did not significantly differ. Calf serum IgG and birth weight did not significantly differ between treatments. Calves from dams fed AATM had greater average daily gain than calves from dams fed ITM. Overall, cows fed AATM during the dry period and early lactation had improved postpartum performance and potential health improvements.     

Effects of replacing inorganic salts of trace minerals with organic trace minerals in pre- and postpartum diets on feeding behavior,rumen fermentation,and performance of dairy cows

Our objectives were to evaluate the effects of complete replacement of supplementary inorganic salts of trace minerals (STM) by organic trace minerals (OTM) in both pre- and postpartum diets on feeding behavior, ruminal fermentation, rumination activity, energy metabolism, and lactation performance in dairy cows. Pregnant cows and heifers (n = 273) were blocked by parity and body condition score and randomly assigned to either STM or OTM diets at 45 ± 3 d before their expected calving date. Both groups received the same diet, except for the source of trace minerals (TM). The STM group was supplemented with Co, Cu, Mn, and Zn sulfates and Na selenite, whereas the OTM group was supplemented with Co, Cu, Mn, and Zn proteinates and selenized yeast. Treatments continued until 156 days in milk and pre- and postpartum diets were formulated to meet 100% of recommended levels of each TM in both treatments, taking into consideration both basal and supplemental levels. Automatic feed bins were used to assign treatments to individual cows and to measure feed intake and feeding behavior. Rumination activity was monitored by sensors attached to a collar from wk ?3 to 3 relative to calving. Blood metabolites were evaluated on d ?21, ?10, ?3, 0, 3, 7, 10, 14, 23, and 65 relative to calving. Ruminal fluid samples were collected using an ororuminal sampling device on d ?21, 23, and 65 relative to calving, for measurement of ruminal pH and concentration of volatile fatty acids. Cows were milked twice a day and milk components were measured monthly. Cows supplemented with OTM tended to have longer daily feeding time (188 vs. 197 min/d), and greater dry matter intake (DMI; 12.9 vs. 13.3 kg), and had a more positive energy balance (3.6 vs. 4.2 Mcal/d) and shorter rumination time per kg of dry matter (DM; 40.1 vs. 37.5 min/kg of DM) than cows supplemented with STM during the prepartum period. In the postpartum period, OTM increased DMI in multiparous cows (24.1 vs. 24.7 kg/d) but not in primiparous cows (19.1 vs. 18.7 kg/d). The difference in DMI of multiparous cows was more evident in the first 5 wk of lactation, when it averaged 1 kg/d. Milk yield was not affected by treatment in multiparous cows (44.1 vs. 44.2 kg/d); however, primiparous cows supplemented with OTM had lesser yields than primiparous cows supplemented with STM (31.9 vs. 29.8 kg/d). Cows supplemented with OTM had a greater percentage of protein in milk (3.11 vs. 3.17%), reduced concentration of nonesterified fatty acids in serum (0.45 vs. 0.40 mmol/L), and rumination activity (30.1 vs. 27.8 min/kg of DM) than cows supplemented with STM. At the end of the transition period, cows supplemented with OTM had reduced molar proportion of acetate, reduced pH, and tended to have a greater concentration of total volatile fatty acids in ruminal fluid. In conclusion, complete replacement of STM by OTM caused modest changes in rumen fermentation, feeding behavior, energy metabolism, and performance of dairy cows, improving postpartum DMI in multiparous cows and reducing circulating levels of nonesterified fatty acids. The pre-absorptive effects of TM source and the parity specific responses on performance warrant further research.     

Effects of level and form of dietary zinc on dairy cow performance and health

A basal mixed ration supplying 36 mg of Zn/kg of dry matter (DM) was supplemented with 1 of 4 concentrates differing in level and form of dietary Zn. The concentrates were fed at 2 kg/cow per day and contained 300 mg of Zn/kg (to supply the total recommended level, according to NRC (2001); R) or 60 mg of Zn/kg (to supply 0.66 of the total recommended level; L), either supplemented as ZnO (I) or organically chelated Zn (O). Forty-four Holstein-Friesian dairy cows (12 primiparous and 32 multiparous), on average 31 d (SD ± 11.4) into lactation, were allocated to 1 of the 4 treatments. All cows remained on the treatment for 14 wk. The data was analyzed by ANOVA as a 2 × 2 factorial design. Dry matter intake averaged 23.5 kg/d and did not differ between treatments. Cows supplemented with organically chelated Zn at the recommended level of inclusion (RO) had a higher milk yield (37.6 kg/d) than those fed inorganic Zn at the recommended level (RI; 35.2 kg/d) or organically chelated Zn at the low level (LO; 35.2 kg/d), but was not different from those fed inorganic Zn at the low level (LI; 36.0 kg/d). Milk composition was unaffected by dietary treatment. Animals that received the low level of Zn (LI and LO) had higher somatic cell counts [3.97 and 3.93 versus 4.35 and 4.55 (log_e) for RI, RO, LI, and LO, respectively] and milk amyloid A levels than those receiving the recommended levels (RO and RI). There was no effect of treatment on body condition score, body weight, or locomotion score. Hoof hardness improved over the duration of the study but there were no differences between treatments. Similarly, blood plasma mineral levels for Zn, Cu, Mo, and Fe were not affected by treatment, whereas there was a trend for increased ceruloplasmin levels in cows receiving the recommended compared with the low level of Zn, but there was no effect of mineral form. There was also no effect of treatment on superoxide dismutase activity or blood hematology. It is concluded that supplementing Zn at the recommended level reduced somatic cell counts and milk amyloid A levels, whereas supplementation in an organic form at the recommended level also increased milk yield.     

Prepartum nutrient intake alters palmitate metabolism by liver slices from peripartal dairy cows

We determined the effects of day relative to parturition and prepartum plane of nutrition on hepatic partitioning of palmitate metabolism to CO₂, acid-soluble products (ASP), and esterified products (EP). Multiparous Holsteins (n = 74) were fed different amounts of nutrients during the dry period in a 3 (far-off period diet) × 2 (close-up period diet) factorial arrangement. During the far-off period (d −60 to −25) cows received a low-energy control diet fed ad libitum (100NRC) to meet National Research Council (NRC) requirements, a moderate-energy diet fed ad libitum to exceed NRC recommendations for net energy of lactation (NE_L) by >50% (150NRC), or the same diet fed at restricted intake to provide 80% of NE_L requirements (80NRC). During the close-up period (d −24 until parturition), cows were fed a diet for ad libitum intake to meet NRC recommendations or in restricted amounts to provide 80% of calculated NE_L requirements. After parturition, all cows had ad libitum access to a lactation diet. Liver slices from biopsies on d −30, −14, 1, 14, and 28 relative to parturition were used to determine conversion of [1-¹⁴C] palmitate to CO₂, ASP, and EP. Across diets, oxidation of palmitate to CO₂ was decreased postpartum, whereas oxidation to ASP was increased at d 1 postpartum compared with other times. Conversion of palmitate to EP increased markedly postpartum, with the greatest rates at d 1 postpartum. Conversion of palmitate to CO₂ and ASP on d 1 postpartum was lower and the proportion of palmitate metabolism as EP was greater for cows fed 150NRC than for those fed 100NRC or 80NRC. Hepatic triacylglycerol concentration at d 1 postpartum was greatest for cows fed 150NRC. Palmitate metabolism did not differ between close-up diets. Hepatic triacylglycerol was negatively correlated with tissue metabolism of palmitate to CO₂ and ASP but positively correlated with metabolism to EP. Hepatic triacylglycerol was highly correlated with NEFA concentrations on the day of calving and d 1 postpartum but not with NEFA prepartum. In contrast, plasma BHBA postpartum was not correlated with hepatic palmitate metabolism by liver slices but was highly correlated with NEFA concentration prepartum. Excessive energy intake during the far-off dry period decreased hepatic palmitate oxidation and shifted palmitate metabolism toward greater esterification, consistent with greater hepatic triacylglycerol accumulation postpartum.     

Patterns of Fourier-transform infrared estimated milk constituents in early lactation Holstein cows on a single New York State dairy

Cows undergo immense physiological stress to produce milk during early lactation. Monitoring early lactation milk through Fourier-transform infrared (FTIR) spectroscopy might offer an understanding of which cows transition successfully. Daily patterns of milk constituents in early lactation have yet to be reported continuously, and the study objective was to initially describe these patterns for cows of varying parity groups from 3 through 10 d postpartum, piloted on a single dairy. We enrolled 1,024 Holstein cows from a commercial dairy farm in Cayuga County, New York, in an observational study, with a total of 306 parity 1 cows, 274 parity 2 cows, and 444 parity ≥3 cows. Cows were sampled once daily, Monday through Friday, via proportional milk samplers, and milk was stored at 4°C until analysis using FTIR. Estimated constituents included anhydrous lactose, true protein, and fat (g/100 g of milk); relative % (rel%) of total fatty acids (FA) and concentration (g/100 g of milk) of de novo, mixed, and preformed FA; individual fatty acids C16:0, C18:0, and C18:1 cis-9 (g/100 g of milk); milk urea nitrogen (MUN; mg/100 g of milk); and milk acetone (mACE), milk β-hydroxybutyrate (mBHB), and milk-predicted blood nonesterified fatty acids (mpbNEFA) (all expressed in mmol/L). Differences between parity groups were assessed using repeated-measures ANOVA. Milk yield per milking differed over time between 3 and 10 DIM and averaged 8.7, 13.3, and 13.3 kg for parity 1, 2, and ≥3 cows, respectively. Parity differences were found for % anhydrous lactose, % fat, and preformed FA (g/100 g of milk). Parity differed across DIM for % true protein, de novo FA (rel% and g/100 g of milk), mixed FA (rel% and g/100 g of milk), preformed FA rel%, C16:0, C18:0, C18:1 cis-9, MUN, mACE, mBHB, and mpbNEFA. Parity 1 cows had less true protein and greater fat percentages than parity 2 and ≥3 cows (% true protein: 3.52, 3.76, 3.81; % fat: 5.55, 4.69, 4.95, for parity 1, 2, ≥3, respectively). De novo and mixed FA rel% were reduced and preformed FA rel% were increased in primiparous compared with parity 2 and ≥3 cows. The increase in preformed FA rel% in primiparous cows agreed with milk markers of energy deficit, such that mpbNEFA, mBHB, and mACE were greatest in parity 1 cows followed by parity ≥3 cows, with parity 2 cows having the lowest concentrations. When measuring milk constituents with FTIR, these results suggest it is critical to account for parity for the majority of estimated milk constituents. We acknowledge the limitation that this study was conducted on a single farm; however, if FTIR technology is to be used as a method of identifying cows maladapted to lactation, understanding variations in early lactation milk constituents is a crucial first step in the practical adoption of this technology.     

Impact of follicular aspiration on folliculogenesis as influenced by dietary energy and stage of lactation

Prolonged dietary energy restriction has been shown to influence the secretion of ovarian hormones and follicular development. Energy balance affects the ability of the cow to support a functional reproductive system during early lactation. Follicular aspiration is a tool that can be used to assess the impact of dietary energy and stage of lactation on follicle development in dairy cattle. Follicular aspiration was conducted twice weekly from d 30 to 100 postpartum in cows fed either 104 or 80% of NRC energy requirements. Oocyte numbers recovered increased linearly from d 30 to 100 postpartum. Cows on high energy diets produced more high quality oocytes, but also produced more poor quality oocytes than cows fed the lower energy diet. Follicles < 5 mm predominated throughout. Cows in early (d 28) and mid (d 117) lactation were used to assess stage of lactation effects on serum and follicular fluid hormones, and quality of oocytes recovered by follicular aspiration procedures for 10 wk. Serum IGF-1 decreased in early lactation cows, but increased in midlactation cows. Follicular fluid progesterone in early lactation cows decreased from 275 to 235 ng/ml, whereas in midlactation cows it increased from 65 to 550 ng/ml at aspiration wk 10. The percentage of high quality ova was higher in early lactation cows (11%) than midlactation cows (6%), but fell to 1% by aspiration wk 7 and increased to 10% by wk 10, whereas percentage of high quality ova in midlactation cows steadily declined to 2% by wk 10. Milk yield and energy balance affect patterns of folliculogenesis in lactating dairy cows.     

Variations of vitamin and mineral contents in raw goat milk of the indigenous Greek breed during lactation

Raw goat milk samples from the indigenous Greek breed in the area of Ioannina, northwestern Greece, were collected during one lactation and analyzed for vitamins A, E, B₁, B₂, and C and for minerals Ca, Mg, P, Na, K, Cu, Fe and Zn. Also, the major constituents of goat milk, namely fat, protein, lactose and solids-non-fat, were determined. The average composition (%) of milk was: fat 4.10, protein 3.36, lactose 4.48 and solids-non-fat 8.54. The mean concentration of the fat-soluble vitamins retinol (A) and α-tocopherol (E) were 0.013 and 0.121 mg/100 ml, respectively. The mean concentration of the water-soluble vitamins, thiamin (B₁), riboflavin (B₂) and ascorbic acid (C) were 0.260, 0.112 and 5.48 mg/100 ml, respectively. Seasonal variations were observed for all vitamins studied. Thiamin had significantly (P < 0.05) higher concentrations during summer than in winter and early spring. The observed variations of the studied vitamins might be attributed to the differences in the feeding of goats during lactation. The mean mineral contents (mg/100 g) of goat milk were Ca 132, P 97.7, Na 59.4, K 152, Mg 15.87, Cu 0.08, Fe 0.06, Zn 0.37 and Mn 6.53 μg/100 g. Seasonal variations were observed for the major minerals Ca, P, K, and the trace elements Cu and Zn.     

Decreased plasma retinol, alpha-tocopherol, and zinc concentration during the periparturient period: effect of milk fever

Retinol (vitamin A), alpha-tocopherol (vitamin E), and Zn are micronutrients essential for health and performance. We determined the effects of parturition, lactation, and periparturient Ca status on plasma retinol, alpha-tocopherol, and Zn in 18 Jersey cows during the 2 wk before and after parturition. Six cows developed clinical milk fever. Prepartum plasma concentrations of retinol, alpha-tocopherol, and Zn decreased progressively in all animals. A nadir was reached at 1 d postpartum when concentrations declined to 38, 47, and 67%, respectively, of prepartal baseline concentrations. Plasma Zn returned to baseline concentrations within 3 d of calving, and plasma alpha-tocopherol returned toward baseline about 10 d after calving. Plasma retinol remained below baseline concentrations throughout the first 2 wk of lactation. The decline in plasma Zn observed at calving was more severe in cows with milk fever (parturient paresis) than in cows without milk fever. The decrease in plasma retinol and alpha-tocopherol observed at parturition was similar in cows with or without milk fever. These data document an acute decline in plasma retinol, alpha-tocopherol, and Zn in the immediate periparturient period and indicate that the decline in plasma Zn is more severe in cows with milk fever.     

Mineral content of some Spanish cheese varieties. Differentiation by source of milk and by variety from their content of main and trace elements

The content in nine mineral elements (P. Ca, Na, K, Mg, Zn, Fe, Cu and Mn) was determined in 153 units of cheese belonging to nine Spanish varieties: two unripe cows milk varieties (Cebreiro and Pasiego), three ripened cows milk varieties (Ahumado de Aliva, Leon and Quesucos), three ripened goats milk varieties (Armada-Sobado, Babia-Laciana and Valdeteja), and one blue-veined cows milk variety (Picón). Using a Kruskal-Wallis one-way analysis of variance, only significant differences were observed in P. K, Mg. Zn, Fe and Mn contents associated to animal milk species used in the manufacture. When the two varieties of unripened cheeses were compared, significant differences in all the elements were observed. The same happened when the three varieties of ripened cows milk cheeses were compared. On comparing the three varieties of ripened goats milk cheeses, only significant differences were observed in P, Ca, Na, K, Mg, Zn and Mn contents. Using stepwise discriminant analysis 76–31% of cases were correctly classified when the cheeses were differentiated according to milk species used in their manufacture. When we differentiated the cheeses according to the variety, 91–66% of cases were correctly classified in the unripe cows milk cheeses, 85% of cases were correctly classified in the ripened cows milk cheeses, and 92–59% of cases were correctly classified in the ripened goats milk cheeses.     

A meta-analysis examining the relationship among dietary factors, dry matter intake, and milk and milk protein yield in dairy cows

This meta-analysis was undertaken to determine the impact of dietary components on dry matter intake (DMI), milk yield (MY), and milk protein yield (MPY) in Holstein dairy cows. Diets (n=846) from 256 feeding trials published in Volumes 73 through 83 of the Journal of Dairy Science were evaluated for nutrient composition using 2 diet evaluation models: CPM Dairy (a computer program based on the principles of the Cornell Net Carbohydrate and Protein System) and NRC (2001). Data were analyzed with and without the effect of stage of lactation as a dummy variable (<100 d in milk or > or =100 d in milk). A mixed model regression analysis was used to completely investigate the potential relationships among composition variables and DMI, MY, and MPY. Protein and carbohydrate fractions were the main components within the DMI models, and DMI played a dominant role in estimating MY and MPY. Inclusion of stage of lactation substantially improved the MY models but did not affect model fits or residual structure for DMI and MPY.