Effects of different vitamin A supplies on performance and the risk of ketosis in transition cows.

This experiment investigated the effects of feeding low and high supplies of vitamin A (VA) during the transition period on plasma metabolites, prevalence of ketosis, and early milk production. In a randomized complete block design, 42 prefresh Holstein cows and 21 heifers were blocked by parity and calving date and assigned to 1 of 3 dietary treatments (n = 21 per treatment unless noted): CON, a transition diet with supplemental VA (75,000 IU/d) to meet the requirement; LVA, a transition diet with no supplemental VA; or HVA, a transition diet receiving supplemental VA (187,500 IU/d) 2.5 times greater than the requirement. Experimental periods were prepartum (-14 d prepartum), postpartum (1 to 30 d in milk), and carryover period (31 to 58 d in milk; common lactating diet with adequate VA was fed). Differences in dry matter intake in the pre- and postpartum periods and milk yield were not detected among treatment. Milk fat, protein, and lactose yields were similar among treatments and not affected by VA. Somatic cell count increased linearly with increasing VA. Body weight and body condition score decreased postpartum, but no VA effect was observed. Plasma retinol concentrations (n = 10 per treatment) decreased at d 2 postpartum and increased as lactation progressed, but the concentrations were unaffected by treatment. Plasma ß-carotene (n = 10 per treatment) had a treatment by time interaction and its concentration decreased after parturition and remained low for 2 wk. Plasma fatty acids and ß-hydroxybutyrate did not differ among treatments. Milk retinol concentration and yield (n = 10 per treatment) increased as VA supply increased. Segmented neutrophils (%) decreased, and lymphocytes (%) increased in blood with increasing VA supply. In conclusion, providing different supplies of VA did not affect production, mobilization of body fat, and risk of ketosis; however, excessive VA supply may have negatively affected the immune response, in part contributing to increased milk somatic cell counts during early lactation.

Effects of corn distillers grains with yeast bodies and manipulation of dietary cation and anion difference on production, nutrient digestibility, and gas emissions from manure in lactating cows.

In a randomized complete block design, 40 lactating Holstein cows (average 98 d in milk and 41 kg/d of milk yield) were randomly assigned to 1 of 4 diets: (1) containing soybean meal as the major protein supplement (CON diet); (2) CON diet with high-protein dried corn distillers grains at 20% on a dry matter (DM) basis by replacing mainly soybean meal (DG diet); (3) DG diet except that high-protein dried corn distillers grains with yeast bodies (extracted after corn ethanol production) was used (DGY diet); or (4) DG diet supplemented with sodium bicarbonate and potassium carbonate to elevate the dietary cation and anion difference (DCAD; DG-DCAD diet). The DCAD of CON, DG, DGY, and DG-DCAD were 185, 62, 67, and 187 mEq/kg of DM, respectively. The experiment began with a 10-d covariate period and then cows were fed the experimental diets for 5 wk (2-wk diet adaptation and 3-wk data collection periods). Dry matter intake and milk yield were measured daily, and spot urine and fecal samples were collected in the last week of the experiment to measure nutrient digestibility; N, S, and P utilization and excretion; and in vitro NH3 and H2S emissions from manure. All data were analyzed using the MIXED procedure of SAS (random effect: block; fixed effects: diets, repeated week, and interactions). During data collection, DM intake was not different among treatment groups, but milk yield tended to be lower (42.4 vs. 39.9 kg/d) for DG, DGY, and DG-DCAD versus CON, which could have been caused by decreases in organic matter and neutral detergent fiber digestibility. Milk protein yield tended to be lower (1.33 vs. 1.24 kg/d) for DG, DGY, and DG-DCAD versus CON. Milk fat yield was lower (1.26 vs. 1.55 kg/d) for DG and DGY versus CON, but that for DG-DCAD (1.43 kg/d) did not differ from CON. Similarly, energy-corrected milk was lower (38.0 vs. 43.3 kg/d) for cows on DG and DGY versus those on CON, but it did not differ between DG-DCAD (40.7 kg/d) and CON. Urinary and fecal N excretion were greater for DG, DGY, and DG-DCAD compared with CON due to greater dietary crude protein content and N intake. However, NH3 emissions did not differ across treatments. Intakes of dietary P and S were greater for DG, DGY, and DG-DCAD, resulting in greater excretion of those in manure and greater H2S emissions from manure compared with CON. These data suggest that the negative effects of feeding distillers grains on production of lactating cows can be partly explained by a decrease in nutrient digestibility (milk yield) and excessive anion load (milk fat). The milk fat response to DG-DCAD suggests that milk fat depression observed with a diet with high content of distillers grains can be partially alleviated by supplementation of cations. In the current study, we observed no beneficial effects of DG containing yeast bodies.

Effects of prepartum vaccination timing relative to pen change with an acidogenic diet on serum and colostrum immunoglobulins in Holstein dairy cows.

The objective of the present study was to assess the effects of prepartum vaccination timing relative to pen change with an acidogenic diet at 28 or 21 d before expected parturition (dpp) on colostral and serum IgG concentrations at calving in pregnant Holstein dairy cows. Pregnant multiparous Holstein cows (n = 308) from one large dairy herd were randomly allocated into 1 of 3 treatment groups at 35 ± 3 dpp: (1) vaccination at 28 dpp and pen change at 21 dpp (V28PC21; n = 108), (2) vaccination and pen change at 28 dpp (V28PC28; n = 99), and (3) vaccination and pen change at 21 dpp (V21PC21; n = 101). An acidogenic diet was fed when cows changed pens at 28 or 21 dpp. Blood and colostral samples were collected within 1 h following parturition. The total number of clinical mastitis (CM) cases within the first 150 d in milk (DIM) were recorded. The V28PC21 cows had greater colostral IgG concentrations at calving (160.4 ± 7.0 g/L) compared with V21PC21 cows (134.4 ± 7.0 g/L), and V28PC28 cows were intermediate (148.3 ± 7.2 g/L). At calving, V28PC21 cows had lower serum IgG concentrations (29.1 ± 1.2 g/L) compared with V21PC21 cows (32.2 ± 1.2 g/L) or V28PC28 cows (32.6 ± 1.3 g/L). Overall, 41% of V21PC21 cows received the booster vaccinations with at least 21 d before actual calving compared with V28PC21 or V28PC28 cows (88 and 86% respectively). The shorter the interval from prepartum booster vaccination to calving, the lower the colostral IgG at calving, regardless of treatment groups. Vaccinating at 28 dpp and pen change with an acidogenic diet at 21 dpp tended to reduce the rate of CM within the first 150 DIM compared with V21PC21. These findings provide evidence that vaccinating cows at 28 dpp, followed by pen change with an acidogenic diet at 21 dpp, improved the concentrations of colostral IgG at calving and tended to reduce the rate of CM. The interaction of prepartum vaccination timing relative to feeding an acidogenic diet should be considered when implementing an effective vaccination program to enhance overall herd health.

Effects of supplementing rumen-protected lysine and methionine during prepartum and postpartum periods on performance of dairy cows.

An experiment was conducted to examine effects of prepartum, postpartum, or continuous prepartum and postpartum supply of rumen-protected lysine (RPLys) and rumen-protected methionine (RPMet) on performance and blood metabolites of transition cows. The experiment consisted of a prepartum (3 wk), postpartum (3 wk), and carryover (10 wk) period. Eighty-eight prepartum cows (36 primiparous and 52 multiparous cows) were blocked by parity and expected calving date and assigned to 1 of 4 treatments arranged factorially. Treatments were a prepartum diet (12% crude protein on a dry matter basis) without (Pre-) or with supplemental RPLys (10 g of digestible Lys/cow per day) and RPMet (4 g of digestible Met/cow per day; Pre+) followed by postpartum diets (16% crude protein on a dry matter basis) without (Post-) or with supplemental RPLys (26 g of digestible Lys/cow per day) and RPMet (11 g of digestible Met/cow per day; Post+). Prepartum, only 2 treatments were applied, but postpartum cows received treatments of Pre-Post-, Pre-Post+, Pre+Post-, or Pre+Post+. During the prepartum period, treatment did not affect dry matter intake and body weight. During the postpartum period, milk protein content was greater (3.23 vs. 3.11%) for Post+ compared with Post- independent of prepartum treatment. However, dry matter intake, body weight, milk yield, and yields of milk components were not affected by Post+ versus Post-. No effects of prepartum treatment or interactions between pre- and postpartum treatments were observed on postpartum performance of cows. No effects of pre- and postpartum supplementation of RPLys and RPMet on performance during the carryover period were found except prepartum supplementation of RPLys and RPMet decreased somatic cell count (4.60 vs. 4.83; log10 transformed) compared with Pre- in the postpartum period and this effect continued during the carryover period [i.e., 4.42 and 4.55 (log10 transformed) for Pre+ and Pre-, respectively]. Prepartum supplementation of RPLys and RPMet increased or tended to increase plasma concentration of Lys, Met, and branched-chain AA compared with Pre- in prepartum cows. Cows on Post+ tended to have greater plasma Lys concentration compared with Post-, but plasma Met concentration was not affected. Health events of postpartum cows were not affected by treatments. In conclusion, we did not observe positive effects of supplementing with RPLys and RPMet on performance of prepartum and postpartum cows. However, prepartum supply of RPLys and RPMet may have potential to improve udder health and immune status of fresh cows.

Effects of feeding diets composed of corn silage and a corn milling product with and without supplemental lysine and methionine to dairy cows.

Formulating diets with high inclusion rates of a feed that provides necessary nutrients at lower-than-market prices for those nutrients should increase income over feed costs if the feed is not detrimental to yields of milk and milk components. The objective of this study was to determine whether cows fed a diet composed of approximately 53% corn silage, 44% corn milling product (68% dry matter, 21% crude protein, 37% neutral detergent fiber, and 9% starch) and 3% minerals (CMP) would have similar productivity as cows fed a control diet of predominantly corn silage, alfalfa silage, corn grain, and soybean meal. Based on the National Research Council (2001) dairy model, the CMP diet was inadequate in metabolizable methionine and extremely low in metabolizable lysine. A third treatment (CMP+AA) was the same as the CMP diet but was supplemented with rumen-protected lysine and methionine. Twenty-one Holstein cows were used in a replicated Latin square (28-d periods) design to evaluate production responses to the 3 diets. Diets were formulated to contain the same concentration of net energy for lactation and metabolizable protein (MP) based on the National Research Council model, but diets with CMP contained more neutral detergent fiber (38.3 vs. 31.4%) and less starch (21.6 vs. 30.5%) than the control diet. Lysine as a percent of MP was 6.5, 6.0, and 6.8 for the control, CMP, and CMP+AA diets, respectively, and methionine was 1.8, 1.8, and 2.3% of MP, respectively. Dry matter intake was not affected by diet (24.3 kg/d), but milk yield was lower for cows fed either CMP diet than for those fed control (36.0 vs 38.1 kg/d). Milk fat concentrations were normal and not affected by diet (3.7%). Milk protein concentration was greater for cows fed CMP+AA than for cows fed the other 2 treatments (3.19 vs. 3.11%); however, milk protein yield was greatest for cows fed the conventional diet. The concentration of methionine in plasma was significantly greater for cows fed CMP+AA than for cows fed the other diets. Plasma lysine concentrations were greater for cows fed the conventional diet than for those fed the other 2 diets. Plasma concentrations of several essential AA were lower for cows fed either CMP diet. Based on calculated energy balance, diets contained similar concentrations of net energy for lactation, but cows fed CMP diets partitioned more energy toward body energy reserves than did control cows, perhaps because supply of specific AA limited milk synthesis.

Evaluation of creatinine as a urine marker and factors affecting urinary excretion of magnesium by dairy cows.

Nutrient balance studies require measuring urine volume, and urinary excretion can be used to assess Mg bioavailability. A less laborious method than total collection of urine could make balance studies more feasible and expand the utility of using urinary Mg as an index of bioavailability, but the method needs to be accurate and sensitive. Sampling interval can affect accuracy because excretion must be at steady state. Two experiments were conducted to (1) determine whether urinary creatinine could be used to accurately estimate urinary output of nutrients markedly excreted via urine (N, K, Na, S, and Mg; experiment 1) and (2) determine the appropriate sampling schedule to evaluate Mg excretion after abrupt diet changes (experiment 2). Experiment 1 was originally designed to evaluate the interaction of monensin [0 vs. 14 mg of monensin/kg of dry matter (DM)] and Mg source (MgO vs. MgSO4; total diet Mg: 0.36% of DM) under antagonism from increased dietary K (2.11% of DM) on urinary Mg excretion. Experiment 2 evaluated the interaction of Mg concentration (basal vs. supplemental MgO; total diet Mg: 0.20 vs. 0.42% of DM) and K (basal vs. supplemental K2CO3; total diet K: 1.60 vs. 2.57% of DM) on urinary Mg excretion over time. Using 4-d composite samples from total collection of urine (n = 34 cow-periods), the average daily excretion of creatinine was similar to previous estimates (29.0 ± 1.16 mg of creatinine/kg of body weight) but was variable among cows (root mean squared error = 2,980 mg/d; 14% of mean). Treatment-average estimated excretion of urine and urinary N, K, Na, S, and Mg were similar to actual values; however, differences between actual and estimated values could be substantial for individual cows. Using the mean creatinine excretion per kilogram of body weight for all cows to estimate urine eliminates the lack of fit variance resulting in artificially low within-treatment variation for estimated urine volume. The standard error of the mean for estimated urine volume was 23% less (1.93 vs. 2.51) than that for actual urine production. This inflated the type I error rate, and, consequently, statistical inferences on N and K excretion differed when urine output was estimated rather than measured. The standard error of the mean for excretion of Mg calculated with actual or estimated urine production were almost identical (0.92 vs. 0.97); however, similar standard error of the mean was likely caused by differences in the covariance of urinary Mg concentration with estimated or actual urine output. Based on spot sampling (experiment 2), urinary Mg reached steady state by 2 d following an increase in dietary K regardless of Mg level, whereas excretion of urinary Mg following an increase in dietary Mg continued to increase through 7 d. Estimating nutrient excretion with urinary creatinine and body weight on average is accurate, but variance is likely underestimated. Knowing the time course of urinary Mg excretion will improve the value of using urinary Mg concentration to assess diet adequacy or Mg bioavailability.

Effects of magnesium source and monensin on nutrient digestibility and mineral balance in lactating dairy cows.

The interaction of monensin and 2 supplemental Mg sources (MgO and MgSO4) on total-tract digestion of minerals and organic nutrients and milk production was evaluated in lactating dairy cattle. Eighteen multiparous Holstein cows (139 ± 35 DIM) were used in a split-plot experiment with 0 or 14 mg/kg diet DM of monensin as the whole-plot treatments and Mg source as split-plot treatments. During the entire experiment (42 d), cows remained on the same monensin treatment but received a different Mg source in each period (21 d) of the Latin square. Diets were formulated to contain 0.35% Mg with about 40% of that provided by MgO or MgSO4. Diets were formulated to have similar concentrations of major nutrients and K concentrations were elevated (2.1% of DM) with K2CO3 to create antagonism to Mg absorption. Apparent digestibility was measured by total collection of urine and feces. Supplemental MgSO4 decreased DMI (26.9 vs. 25.7 kg/d) and tended to decrease milk yield (40.2 vs. 39.3 kg/d), but increased the digestibility of OM (68.3 vs. 69.2%) and starch (91.9 vs. 94.4%) compared with MgO. Feeding MgSO4 with monensin decreased NDF digestibility compared with other treatments (46.7 vs. 50.2%). That diet also had decreased apparent absorption of Mg compared with diets without monensin (15.6 vs. 19.2%), whereas MgO with monensin had greater apparent absorption of Mg (23.0%) than other treatments. Cows consuming MgSO4 had increased apparent Ca absorption (32.2 vs. 28.1%) and balance. A diet with MgSO4 without monensin increased the concentration of long-chain fatty acids in milk, suggesting increased mobilization of body fat or decreased de novo fatty acid synthesis in the mammary gland. Overall, when dietary Mg was similar, MgO was the superior Mg source for lactating dairy cattle, but inclusion of monensin in diets should be considered when evaluating Mg sources.

A 100-Year Review: From ascorbic acid to zinc-Mineral and vitamin nutrition of dairy cows.

Mineral and vitamin nutrition of dairy cows was studied before the first volume of the Journal of Dairy Science was published and is still actively researched today. The initial studies on mineral nutrition of dairy cows were simple balance experiments (although the methods available at the time for measuring minerals were anything but simple). Output of Ca and P in feces, urine, and milk was subtracted from intake of Ca and P, and if values were negative it was often assumed that cows were lacking in the particular mineral. As analytical methods improved, more minerals were found to be required by dairy cows, and blood and tissue concentrations became primary response variables. Those measures often were poorly related to cow health, leading to the use of disease prevalence and immune function as a measure of mineral adequacy. As data were generated, mineral requirements became more accurate and included more sources of variation. In addition to milk yield and body weight inputs, bioavailability coefficients of minerals from different sources are used to formulate diets that can meet the needs of the cow without excessive excretion of minerals in manure, which negatively affects the environment. Milk, or more accurately the lack of milk in human diets, was central to the discovery of vitamins, but research into vitamin nutrition of cows developed slowly. For many decades bioassays were the only available method for measuring vitamin concentrations, which greatly limited research. The history of vitamin nutrition mirrors that of mineral nutrition. Among the first experiments conducted on vitamin nutrition of cows were those examining the factors affecting vitamin concentrations of milk. This was followed by determining the amount of vitamins needed to prevent deficiency diseases, which evolved into research to determine the amount of vitamins required to promote overall good health. The majority of research was conducted on vitamins A, D, and E because these vitamins have a dietary requirement, and clinical and marginal deficiencies became common as diets for cows changed from pasture and full exposure to the sun to stored forage and limited sun exposure. As researchers learned new functions of fat-soluble vitamins, requirements generally increased over time. Diets generally contain substantial amounts of B vitamins, and rumen bacteria can synthesize large quantities of many B vitamins; hence, research on water-soluble vitamins lagged behind. We now know that supplementation of specific water-soluble vitamins can enhance cow health and increase milk production in certain situations. Additional research is needed to define specific requirements for many water-soluble vitamins. Both mineral and vitamin research is hampered by the lack of sensitive biomarkers of status, but advanced molecular techniques may provide measures that respond to altered supply of minerals and vitamins and that are related to health or productive responses of the cow. The overall importance of proper mineral and vitamin nutrition is known, but as we discover new and more diverse functions, better supplementation strategies should lead to even better cow health and higher production.

Effect of source of trace minerals in either forage- or by-product-based diets fed to dairy cows: 2. Apparent absorption and retention of minerals.

Eighteen multiparous cows were used in a split-plot replicated Latin square with two 28-d periods to evaluate the effects of source of supplemental Cu, Zn, and Mn (sulfates or hydroxy) on apparent absorption of minerals when fed in either a forage- or by-product-based diet. The by-product diets were formulated to have greater concentrations of NDF and lesser concentrations of starch, and specific ingredients were chosen because they were good sources of soluble fiber and ß-glucans, which bind trace minerals in nonruminants. We hypothesized that hydroxy trace minerals would interact less with digesta and have greater apparent absorption compared with sulfate minerals, and the difference in apparent absorption would be greater for the by-product diet compared with the forage-based diet. During the 56-d experiment, cows remained on the same fiber treatment but source of supplemental trace mineral was different for each 28-d period; thus, all cows were exposed to both mineral treatments. During each period cows were fed no supplemental Cu, Zn, or Mn for 16 d, followed by 12 d of feeding supplemental minerals from either sulfate or hydroxy sources. Supplemental minerals for each of the mineral sources fed provided approximately 10, 35, and 32 mg/kg of supplemental Cu, Zn, and Mn, respectively, for both fiber treatments. Total Cu, Zn, and Mn dietary concentrations, respectively, were approximately 19, 65, and 70 mg/kg for the forage diets and 21, 85, and 79 for the by-product diets. Treatment had no effect on dry matter intake (24.2 kg/d) or milk production (34.9 kg/d). Cows consuming the by-product diets had greater Zn (1,863 vs. 1,453 mg/d) and Mn (1,790 vs. 1,588 mg/d) intake compared with cows fed forage diets, but apparent Zn absorption was similar between treatments. Manganese apparent absorption was greater for the by-product diets compared with the forage diets (16 vs. 11%). A fiber by mineral interaction was observed for Cu apparent absorption, as cows fed hydroxy minerals with forage diets had greater apparent absorption compared with cows fed sulfate minerals; however, the opposite was observed with the by-product diets. Source of supplemental trace minerals and type of fiber in diets affected availability of Cu and Mn and should be considered in ration formulation.

Effect of source of trace minerals in either forage- or by-product-based diets fed to dairy cows: 1. Production and macronutrient digestibility.

Excess rumen-soluble Cu and Zn can alter rumen microbial populations and reduce fiber digestibility. Because of differences in particle size and chemical composition, ruminal and total-tract digestibility of fiber from forage- and by-product-based diets can differ. We hypothesized that, because of differences in mineral solubility, diets with hydroxy rather than sulfate trace minerals would have greater fiber digestibility, but the effect may depend on source of fiber. Eighteen multiparous cows were used in a split-plot replicated Latin square with two 28-d periods to evaluate the effects of Cu, Zn, and Mn source (sulfates or hydroxy; Micronutrients USA LLC, Indianapolis, IN) and neutral detergent fiber (NDF) source (forage diet = 26% NDF vs. by-product = 36%) on total-tract nutrient digestibility. During the entire experiment (56 d) cows remained on the same fiber treatment, but source of supplemental trace mineral was different for each 28-d period so that all cows were exposed to both mineral treatments. During each of the two 28-d periods, cows were fed no supplemental Cu, Zn, or Mn for 16 d followed by 12 d of feeding supplemental Cu, Zn, and Mn from either sulfates or hydroxy sources. Supplemental minerals for each of the mineral sources fed provided approximately 10, 35, and 32 mg/kg of supplemental Cu, Zn, and Mn, respectively, for both fiber treatments. Total dietary concentrations of Cu, Zn, and Mn were approximately 19, 65, and 70 mg/kg for the forage diets and 21, 85, and 79 mg/kg for the by-product diets, respectively. Treatment had no effect on dry matter intake (24.2 kg/d) or milk production (34.9 kg/d). Milk fatty acid profiles were altered by fiber source, mineral source, and their interaction. Cows fed the by-product diets had lower dry matter (65.9 vs. 70.2%), organic matter (67.4 vs. 71.7%), and crude protein digestibility (58.8 vs. 62.1%) but greater starch (97.5 vs. 96.3%) and NDF digestibility (50.5 vs. 44.4%) compared with cows fed the forage treatment. Feeding increased concentrations of by-products decreased total digestible nutrients regardless of mineral source. Feeding hydroxy Cu, Zn, and Mn increased NDF digestibility (48.5 vs. 46.4%) but had no effect on total digestible nutrients.

Short- and longer-term effects of feeding increased metabolizable protein with or without an altered amino acid profile to dairy cows immediately postpartum.

The first few weeks after parturition is marked by low, but increasing feed intake and sharply increasing milk production by dairy cows. Because of low intake, the nutrient density of the diet may need to be higher during this period to support increasing milk yields. We hypothesized that feeding higher levels of metabolizable protein (MP) or a protein supplement with rumen-protected lysine and methionine during the immediate postpartum period would increase yields of milk and milk components. Fifty-six Holstein cows (21 primiparous and 35 multiparous) starting at 3 d in milk were used in a randomized block design. In phase 1 (3 through 23 d in milk), cows were fed 1 of 3 diets that differed in supply of MP and AA profile. At 23 d in milk, all cows were moved to a common freestall pen and fed the control diet used in phase 1 for an additional 63 d (phase 2). Diets were formulated using the National Research Council model and were control [16.5% crude protein (CP), 10.9% rumen-degradable protein (RDP), and 5.6% rumen-undegradable protein (RUP)], high MP (HMP; 18.5% CP, 11.6% RDP, 6.9% RUP), and AA (MPAA; 17.5% CP, 10.5% RDP, 7.0% RUP 29.7). The MPAA diet included a proprietary spray-dried blood meal product (Perdue Agribusiness, Salisbury, MD) and contained a model-estimated 7.2 and 2.6% of digestible lysine and methionine (% of MP). The HMP and control diets contained 6.3 and 6.7% digestible lysine and both had 1.8% digestible methionine. In phase 1, diet did not affect milk yield (33.6, 34.7, and 33.2 kg for control, HMP, and MPAA, respectively), dry matter intake (17.8, 18.0, and 18.5 kg/d for control, HMP, and MPAA), or milk protein yield (1.07 kg/d). Feeding additional protein (HMP or MPAA) increased both the concentration and yield of milk fat, and milk protein concentration was greater (3.30 vs. 3.17%) for MPAA compared with the HMP diet. Energy-corrected milk was greater (38.4 and 38.6 vs. 35.3 kg/d, respectively) for MPAA and HP than for the control. Cows fed MPAA had the greatest plasma concentrations of Met and the lowest concentrations of isoleucine, but lysine was not affected by treatment. Feeding additional MP (HMP or MPAA) reduced the concentrations of 3-methylhistidine in plasma, indicating reduced muscle breakdown. Diet effects on milk composition continued after cows were changed to a common diet in that cows fed MPAA the first 3 wk of lactation had greater concentration of milk protein for the entire experiment than cows fed HMP, and cows fed additional MP (HMP and MPAA) during phase 1 had greater concentrations of milk fat for the entire experiment. Increasing dietary protein and AA supply in early lactation had short-term effects on yield of energy-corrected milk and long-term effects on milk composition.

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.

Source of supplemental dietary copper, zinc, and manganese affects fecal microbial relative abundance in lactating dairy cows.

Appropriate trace mineral supplementation can improve immune response and hoof health in cattle and at much higher rates of supplementation to swine and poultry can alter microbial colonization of the gut, resulting in improved gut health. Diet can influence fecal microbial excretion in cattle, and the fecal microbiome may serve as a means for assessing gastrointestinal microbial changes. We hypothesized that feeding diets that differed in source of supplemental Cu, Zn, or Mn would alter the relative abundance of fecal microbes in lactating dairy cattle and that organic Zn would have the greatest effect. Twenty-four cows were fed diets devoid of supplemental Cu, Zn, and Mn for a 16-d preliminary phase (basal diet provided 9, 29, and 32 mg/kg of Cu, Zn, and Mn, respectively), and then were randomly assigned to 1 of 3 treatment diets (n = 8 cows/treatment): one group of cows was fed supplemental Cu, Zn, and Mn from sulfate minerals; the second group was fed glycinate minerals; and the third group was fed Cu and Mn sulfate with glycinate Zn. Assayed total dietary concentrations were approximately 21, 73, and 72 mg/kg for Cu, Zn, and Mn, respectively. Milk production (averaged 38.8 kg/d), DMI (averaged 25.8 kg/d), and milk components were not affected by treatment. Fecal DNA was extracted, amplified using a universal primer targeting the V4-V5 hypervariable region of the 16S rRNA gene, and sequenced to compare microbial community composition between treatments. Relative abundances of Treponema species-level operational taxonomic units (OTU) were less for animals fed Cu and Mn sulfate with glycinate Zn compared with sulfates alone, but were similar to animals fed glycinate mineral sources. Relative abundances for exclusive glycinate mineral and sulfate mineral treatments were similar. Treponema OTU and cultured representatives are often associated with bovine digital dermatitis. These data may provide an additional link between organic Zn supplementation and improved hoof health. To our knowledge this is the first report of a dietary treatment decreasing the relative abundance of Treponema OTU in cattle feces; however, the potential benefits of this response on overall animal health and the mechanism for the observed responses are unknown and warrant further investigation.

Effect of feeding 25-hydroxyvitamin D3 with a negative cation-anion difference diet on calcium and vitamin D status of periparturient cows and their calves.

Holstein cows (>1 gestation) were fed 1 of 3 diets during the last 13 d of gestation (ranged from 22 to 7 d). The control diet (16 cows) was formulated to provide 18,000 IU/d of vitamin D3 and had a dietary cation-anion difference (DCAD) of 165mEq/kg (DCAD=Na + K - Cl - S). The second diet (DCAD + D) provided the same amount of vitamin D3 but had a DCAD of -139mEq/kg (17 cows). The third diet (DCAD + 25D) had no supplemental vitamin D3 but provided 6mg/d of 25-(OH) vitamin D3 [25-(OH)D3] with a DCAD of -138mEq/kg (20 cows). Diets were fed until parturition and then all cows were fed a common lactation diet that contained vitamin D3. Negative DCAD diets reduced urine pH, with the greatest decrease occurring with the DCAD + D treatment. Urinary Ca excretion was greatest for cows fed DCAD + 25D followed by cows fed DCAD + D. Urinary pH was negatively correlated with urinary excretion of Ca for cows fed DCAD + D. No such correlation was observed with the DCAD + 25D treatment because substantial excretion of urinary Ca occurred at moderate urinary pH values for that treatment. Cows fed DCAD + 25D had greater serum concentrations of 25-(OH)D3 than other treatments from 5 d after supplementation started through 7 d in milk. Concentrations of 1,25-(OH)2D3 in serum were greatest in DCAD + 25D cows starting at 2 d before calving and continued through 7 d in milk. Serum Ca concentrations 5 d before calving were greatest for cows fed DCAD + 25D, but at other time points before and after parturition treatment did not affect serum Ca. Incidence of clinical hypocalcemia was not statistically different between treatments, but cows fed DCAD + 25 had the highest incidence rate (12.5, 0, and 20% for control, DCAD + D, and DCAD + 25D). Calves born from cows fed DCAD + 25D had greater concentrations of 25-(OH)D3 in serum at birth than calves from other treatments (before colostrum consumption), but concentrations were similar by 3 d of age. Concentrations of 25-(OH)D3 in colostrum and transition milk were increased by feeding DCAD + 25D, but by 28 d in milk treatment effects no longer existed. Overall, feeding 25-OH vitamin D with a negative DCAD diet increased vitamin D status of the cow and her newborn calf but had minimal effects on calcium status and did not have positive effects on the incidence of hypocalcemia.

Effect of including canola meal and supplemental iodine in diets of dairy cows on short-term changes in iodine concentrations in milk.

The dietary requirement for iodine is based on thyroxine production, but data are becoming available showing potential improvements in hoof health when substantially greater amounts of I are fed. Feeding high amounts of I, however, can result in the milk having excessive concentrations of I. Canola meal contains goitrogenic compounds that reduce the transfer of I into milk. We hypothesized that including canola meal in diets would allow high supplementation rates of I without producing milk with unacceptable concentrations of I. Thirty midlactation Holstein cows were fed a diet with all supplemental protein from soybean meal (0% of diet dry matter as canola meal) or with all supplemental protein from canola meal (13.9% canola meal). A third treatment has a mix of soybean meal and canola meal (3.9% canola meal). Within canola-meal treatment, cows were fed 0.5 or 2.0mg of supplemental I per kilogram of diet dry matter from ethylenediamine dihydroiodide. Cows were maintained on the canola treatment for the duration of the experiment but were changed from one I treatment to the other after 13d of receiving the treatment. Milk I concentration before the treatments started (cows fed 0.5mg/kg of I) averaged 272µg/L and increased within 22h after cows were first fed diets with 2mg/kg of I. As inclusion rate of canola meal increased, the concentration of I in milk decreased linearly. After 12d of supplementation, milk from cows fed 0.5mg/kg of I had 358, 289, and 169µg of I/L for the 0, 3.9%, and 13.9% canola-meal treatments. For cows fed 2.0mg/kg of I, milk I concentrations were 733, 524, and 408µg/L, respectively. Concentrations of I in serum increased with increased I supplementation, but the effect of canola meal was opposite of what was observed for milk I. Cows fed the highest canola-meal diets had the highest serum I whether cows were fed 0.5 or 2.0mg/kg of I. Feeding dairy cows diets with 13.9% canola meal maintained milk I concentrations below 500µg/L when diets were supplemented with 2mg/kg of I.

Invited review: Enteric methane in dairy cattle production: quantifying the opportunities and impact of reducing emissions.

Many opportunities exist to reduce enteric methane (CH4) and other greenhouse gas (GHG) emissions per unit of product from ruminant livestock. Research over the past century in genetics, animal health, microbiology, nutrition, and physiology has led to improvements in dairy production where intensively managed farms have GHG emissions as low as 1 kg of CO2 equivalents (CO2e)/kg of energy-corrected milk (ECM), compared with >7 kg of CO2 e/kg of ECM in extensive systems. The objectives of this review are to evaluate options that have been demonstrated to mitigate enteric CH4 emissions per unit of ECM (CH4/ECM) from dairy cattle on a quantitative basis and in a sustained manner and to integrate approaches in genetics, feeding and nutrition, physiology, and health to emphasize why herd productivity, not individual animal productivity, is important to environmental sustainability. A nutrition model based on carbohydrate digestion was used to evaluate the effect of feeding and nutrition strategies on CH4/ECM, and a meta-analysis was conducted to quantify the effects of lipid supplementation on CH4/ECM. A second model combining herd structure dynamics and production level was used to estimate the effect of genetic and management strategies that increase milk yield and reduce culling on CH4/ECM. Some of these approaches discussed require further research, but many could be implemented now. Past efforts in CH4 mitigation have largely focused on identifying and evaluating CH4 mitigation approaches based on nutrition, feeding, and modifications of rumen function. Nutrition and feeding approaches may be able to reduce CH4/ECM by 2.5 to 15%, whereas rumen modifiers have had very little success in terms of sustained CH4 reductions without compromising milk production. More significant reductions of 15 to 30% CH4/ECM can be achieved by combinations of genetic and management approaches, including improvements in heat abatement, disease and fertility management, performance-enhancing technologies, and facility design to increase feed efficiency and life-time productivity of individual animals and herds. Many of the approaches discussed are only partially additive, and all approaches to reducing enteric CH4 emissions should consider the economic impacts on farm profitability and the relationships between enteric CH4 and other GHG.

Effects on lactating dairy cows of oscillating dietary concentrations of unsaturated and total long-chain fatty acids.

The nutrient composition of diets can vary from batch to batch because of variation in the nutrient composition of ingredients. The concentration of fat in distillers grains can be highly variable and, coupled with a high dietary inclusion rate, can result in substantial variation in the fat concentration of the total diet. Our hypothesis was that variation in dietary fat concentrations over short periods would have negative effects on production measures of dairy cattle. Twenty-four Holstein cows were used in 8 truncated Latin squares (3 cows × 2 periods). Periods were 16 d long, with a 12-d washout period separating the 2 periods. The 3 treatments were 1) control, 2) moderate variation, and 3) high variation. The control treatment was a consistent diet over the 16 d and contained 5.8% (dry basis) total long-chain fatty acids (LCFA), 23.7% distillers grains, and 1.1% of dry matter as corn oil. The average concentration of LCFA over the 16-d period for the moderate variation and high variation treatments was also 5.9%, but concentrations of LCFA varied over time by the addition or removal of corn oil. The moderate variation treatment had a 4-d phase of 5.4% LCFA, followed by a 4-d phase with 6.4% LCFA to complete the cycle, and then the cycle was repeated. The high variation treatment followed the same cycle pattern, but concentration of LCFA was either 4.8 or 7.0%. Over the 16 d, dry matter intake and milk yield were significantly decreased by the high variation treatment (intake = 21.7, 21.8, and 20.7 kg/d; milk = 36.4, 37.6, and 35.4 kg/d for the control, moderate variation, and high variation treatments). The effect of variation appeared to be cumulative; differences were not significant in the first 8-d cycle but were in the second 8-d cycle. Milk fat concentration was low (2.4%) and was not affected by treatment or cycle × treatment. The concentration of trans-10 C18:1 in milk fat was very high (4.2% of total milk fatty acids) but was not affected by treatment. However, cows on the high variation treatment had higher concentrations of trans-10, cis-12 C18:2 in milk fat (0.036, 0.042, and 0.047% of milk fatty acids for the control, moderate variation, and high variation treatments). Overall, an extreme short-term fluctuation in dietary fat concentration was needed before negative effects were observed.

Effect of linoleic acid and dietary vitamin E supplementation on sustained conjugated linoleic acid production in milk fat from dairy cows.

Conjugated linoleic acid (CLA; cis-9,trans-11 18:2), a bioactive fatty acid (FA) found in milk and dairy products, has potential human health benefits due to its anticarcinogenic and antiatherogenic properties. Conjugated linoleic acid concentrations in milk fat can be markedly increased by dietary manipulation; however, high levels of CLA are difficult to sustain as rumen biohydrogenation shifts and milk fat depression (MFD) is often induced. Our objective was to feed a typical Northeastern corn-based diet and investigate whether vitamin E and soybean oil supplementation would sustain an enhanced milk fat CLA content while avoiding MFD. Holstein cows (n=48) were assigned to a completely randomized block design with repeated measures for 28 d and received 1 of 4 dietary treatments: (1) control (CON), (2) 10,000 IU of vitamin E/d (VE), (3) 2.5% soybean oil (SO), and (4) 2.5% soybean oil plus 10,000 IU of vitamin E/d (SO-VE). A 2-wk pretreatment control diet served as the covariate. Milk fat percentage was reduced by both high-oil diets (3.53, 3.56, 2.94, and 2.92% for CON, VE, SO, and SO-VE), whereas milk yield increased significantly for the SO-VE diet only, thus partially mitigating MFD by oil feeding. Milk protein percentage was higher for cows fed the SO diet (3.04, 3.05, 3.28, and 3.03% for CON, VE, SO, and SO-VE), implying that nutrient partitioning or ruminal supply of microbial protein was altered in response to the reduction in milk fat. Milk fat concentration of CLA more than doubled in cows fed the diets supplemented with soybean oil, with concurrent increases in trans-10 18:1 and trans-11 18:1 FA. Moreover, milk fat from cows fed the 2 soybean oil diets had 39.1% less de novo synthesized FA and 33.8% more long-chain preformed FA, and vitamin E had no effect on milk fat composition. Overall, dietary supplements of soybean oil caused a reduction in milk fat percentage and a shift in FA composition characteristic of MFD. Supplementing diets with vitamin E did not overcome the oil-induced reduction in milk fat percentage or changes in FA profile, but partially mitigated the reduction in fat yield by increasing milk yield.

Effects of copper supplementation on feedlot performance, carcass characteristics, and rumen sulfur metabolism of growing cattle fed diets containing 60% dried distillers grains.

The effects of 3 supplemental Cu concentrations on feedlot performance, mineral absorption, carcass characteristics, and ruminal S metabolism of cattle fed diets containing 60% dried distillers grains with solubles (DDGS) were evaluated in 2 experiments. Experiment 1 was conducted with 84 Angus-cross yearling steers and heifers (initial BW = 238 ± 36 kg), which were blocked by gender and allocated to 12 pens. Supplemental dietary Cu (tribasic copper chloride) treatments were: 1) 0 mg Cu/kg diet DM, 2) 100 mg Cu/kg diet DM, 3) 200 mg Cu/kg diet DM. The remainder of the diet was DDGS (60%), grass hay (10%), pelleted soy hulls (15%), and a vitamin-mineral supplement (15%). Diets were offered ad libitum throughout the finishing phase (168 d). Three cattle from each pen (n = 36) were harvested on d 168 and carcass data and liver samples were collected. Copper supplementation did not affect ADG (P = 0.22). However, the nonsignificant trend for increased ADG and decreased DMI led to a linear increase (P = 0.02) feed efficiency (G:F = 0.167, 0.177, and 0.177 for 0, 100, and 200 mg Cu/kg diet DM, respectively). The apparent absorption of Cu decreased quadratically (P = 0.07) and the apparent absorption of Mn and Zn were decreased linearly (P = 0.03 and P = 0.05, respectively) with increased Cu supplementation. Cattle supplemented with 100 or 200 mg Cu/kg diet DM had greater liver Cu concentrations (P < 0.01) than cattle that were not supplemented with Cu. There were no treatment effects (P > 0.10) on HCW, LM area, USDA yield grade, backfat, or marbling score. Experiment 2 was conducted with 6 ruminally fistulated steers that were fed the same diets as in Exp 1 in a replicated 3 × 3 Latin Square design. Copper supplementation did not affect (P > 0.10) ruminal pH or liquid S(2-) concentrations in steers consuming 60% DDGS diets (total dietary S = 0.55%). From 3 to 9 h after feeding, H(2)S gas concentration was decreased in those cattle supplemented with 100 mg Cu/kg diet. Concentration of H(2)S gas did not differ among cattle supplemented with 0 or 200 mg Cu/kg diet DM on 60% DDGS diets. Supplemental Cu improved feed efficiency in cattle consuming diets containing 60% DDGS; however, effects of Cu on rumen S metabolism were minimal even when supplemented at twice the maximum tolerable limit for beef cattle (NRC, 2000).

The value of different fat supplements as sources of digestible energy for lactating dairy cows.

The effects of fat supplements that differed in fatty acid composition (chain length and degree of saturation) and chemical form (free fatty acids, Ca salts of fatty acids, and triacylglyceride) on digestible energy (DE) concentration of the diet and DE intake by lactating cows were measured. Holstein cows were fed a control diet [2.9% of dry matter (DM) as long-chain fatty acids] or 1 of 3 diets with 3% added fatty acids (that mainly replaced starch). The 3 fat supplements were (1) mostly saturated (C18:0) free fatty acids (SFA), (2) Ca-salts of fatty acids (CaFA), and (3) triacylglyceride high in C16:0 fatty acids (TAG). Cows fed CaFA (22.8 kg/d) consumed less DM than cows fed the control (23.6 kg/d) and TAG (23.8 kg/d) diets but similar to cows fed SFA (23.2 kg/d). Cows fed fat produced more fat-corrected milk than cows fed the control diet (38.2 vs. 41.1 kg/d), mostly because of increased milk fat percentage. No differences in yields of milk or milk components were observed among the fat-supplemented diets. Digestibility of DM, energy, carbohydrate fractions, and protein did not differ between diets. Digestibility of long-chain fatty acids was greatest for the CaFA diet (76.3%), intermediate for the control and SFA diets (70.3%), and least for the TAG diet (63.3%). Fat-supplemented diets had more DE (2.93 Mcal/kg) than the control diet (2.83 Mcal/kg), and DE intake by cows fed supplemented diets was 1.6 Mcal/d greater than by cows fed the control, but no differences were observed among the supplements. Because the inclusion rate of supplemental fats is typically low, large differences in fatty acid digestibility may not translate into altered DE intake because of small differences in DM intake or digestibility of other nutrients.