Evaluation of rumen-protected methionine sources and period length on performance of lactating dairy cows within Latin squares

Multiparous Holstein cows (n = 16) were used in a replicated (n = 4) Latin square design with 2-wk periods to determine whether length of the experimental period chosen within Latin square designs would influence experimental outcomes for performance-related variables. Cows were fed a basal TMR formulated to supply Lys in excess of the predicted requirements and either no rumen-protected Met (RP-Met; control), or 6 (M6) or 12 (M12) g/d of RP-Met (Mepron), or 12 (S12) g/d of RP-Met (Smartamine M). Performance outcomes were evaluated separately using data collected at the end of each week of each period, and as overall means for each period. Milk yield was not affected by treatment in any period. Supplementation of RP-Met from all sources tended to increase milk fat percentage when evaluated using wk-1 data, but responses evaluated using wk-2 data only were not significant. Supplementation of M12 and S12 tended to increase milk fat percentage over the entire experimental period. Supplementation of M6 and M12 tended to increase milk true protein percentage when evaluated using wk-1 data only; however, responses to treatments during wk 2 were not significant. All supplemental RP-Met treatments either tended to increase (M6 and S12) or increased (M12) milk true protein content over the entire experimental period relative to the control treatment. Yields of fat and true protein were not affected by treatment. Carryover effects of treatment on production variables were largely not significant. Predictions of nutrient supply with 3 models used in dairy ration formulation and evaluation (CPM-Dairy, AminoCow, and 2001 NRC Dairy) indicated that energy, protein, and Met all were supplied in excess of requirements for all treatments. Overall, results suggest that interpretation of performance outcomes can vary depending on selection of the experimental period in Latin squares, and responses to increased Met supply based on ratio-based formulation may not be independent of the grams of Met supplied.     

Effect of feeding different sources of rumen-protected methionine on milk production and N-utilization in lactating dairy cows

Objectives of this study were to quantify production responses of lactating dairy cows to supplying absorbable Met as isopropyl-2-hydroxy-4-(methylthio)-butanoic acid (HMBi), or rumen-protected Met (RPM, Smartamine M; Adisseo, Alpharetta, GA) fed with or without 2-hydroxy-4-(methylthio)-butanoic acid (HMB), and to determine whether Met supplementation will allow the feeding of reduced dietary crude protein (CP). Seventy cows were blocked by parity and days in milk into 14 blocks and randomly assigned within blocks to 1 of the 5 dietary treatments based on alfalfa and corn silages plus high-moisture corn: 1 diet with 15.6% CP and no Met source (negative control); 3 diets with 15.6% CP plus 0.17% HMBi, 0.06% RPM + 0.10% HMB, or 0.06% RPM alone; and 1 diet with 16.8% CP and no Met supplement (positive control). Assuming that 50% of ingested HMBi was absorbed from the gastrointestinal tract and 80% of the Met in RPM was absorbed at intestine, the HMBi and RPM supplements increased metabolizable Met supply by 9 g/d and improved the Lys:Met ratio from 3.6 to 3.0. After a 2-wk covariate period during which all cows received the same diet, cows were fed test diets continuously for 12 wk. Diet did not affect dry matter intake (mean ± SD, 25.0 ± 0.3 kg/d), body weight gain (0.59 ± 0.2 kg/d), or milk yield (41.7 ± 0.6 kg/d). However, feeding HMBi increased yield of energy-corrected milk and milk content of protein and solids-not-fat. Moreover, trends were observed for increased milk fat content and yield of fat and true protein on all 3 diets containing supplemental Met. Apparent N efficiency (milk N/N intake) was highest on the RPM treatment. Feeding 16.8% CP without a Met source elevated milk urea N and urinary excretion of urea N and total N and reduced apparent N efficiency from 34.5 to 30.2%, without improving production. Overall results suggested that feeding HMBi or RPM would give similar improvements in milk production and N utilization.     

Meta-analysis of lactation performance in dairy cows receiving supplemental dietary methionine sources or postruminal infusion of methionine

The objectives of our study were to evaluate the productive response to methionine supplementation in lactating dairy cows and to define a relationship between metabolizable Met (MP Met) intake and production. A database of 64 papers meeting the selection criteria was developed evaluating postruminally infused dl-methionine (9 papers with 18 control diets and 35 treatment comparisons), 2-hydroxy-4-methylthio butanoic acid (HMTBa) provided as either a liquid or Ca salt form (17 papers with 34 control diets and 46 treatment comparisons), Mepron (Evonik Industries, Essen, Germany; 18 papers with 35 control diets and 42 treatment comparisons), and Smartamine (Adisseo Inc., Antony, France; 20 papers with 30 control diets and 39 treatment comparisons). Dietary ingredients and their accompanying nutritional compositions as described in the reports were entered into the Cornell-Penn-Miner software to model the diets and to predict nutrients that were not reported in the original publication. Data were analyzed using a weighted analysis of response to supplementation compared with the intraexperiment control, as well as through a regression analysis to changing dietary MP Met. Data included in the analysis were from experiments published between 1970 and 2011 with cows supplemented with between 3.5 and 67.9 g of Met or its equivalent from HMTBa. Cows supplemented with Smartamine consumed more, whereas cows supplemented with Mepron consumed less DM compared with controls. Milk yield did not significantly respond to Met supplementation, although it tended to increase for cows supplemented with HMTBa and Mepron. Milk protein yield was increased due to supplementation from all sources or from infusion, and protein concentration was greater for all supplements or infusion of dl-Met, except for cows supplemented with HMTBa. Irrespective of Met source, milk protein yield increased 2.23 g of protein/g of MP Met until reaching the breakpoint. Milk fat yield was increased for Mepron and HMTBa, whereas milk fat concentration was increased for infused dl-Met and for cows supplemented with HMTBa. Based on regression analysis, response of milk fat yield to Met supplementation was not different for infused dl-Met, Mepron, and Smartamine (1.87 g of fat/g of MP Met), whereas the response to HMTBa was significantly greater at 5.38 g of fat/g of MP Met.     

Effects of providing two forms of supplemental methionine to periparturient Holstein dairy cows on feed intake and lactational performance

Eighteen primiparous and 42 multiparous Holstein cows were blocked according to parity and expected calving date and assigned randomly to 1 of 3 dietary treatments: 1) a basal diet (negative control), 2) the basal diet plus 2-hydroxy-4-methylthio butanoic acid isopropyl ester (MetaSmart, Adisseo Inc., Antony, France), or 3) the basal diet plus rumen-protected Met (Smartamine M, Adisseo Inc., Alpharetta, GA). Treatments were initiated 21 d before expected calving and continued through 140 d postpartum. Diets were similar in ingredient and chemical composition, except for the content of Met in metabolizable protein. MetaSmart [0.35% prepartum and 0.54% postpartum in diet dry matter (DM)] and Smartamine M (0.06% prepartum and 0.10% postpartum in diet DM) were added to the basal diet in amounts needed to achieve a 3.0:1 ratio of Lys to Met in metabolizable protein. Prepartum DM intake (DMI; 13.5 kg/d), body weight (687 kg), body condition score (3.81), postpartum milk yield (42.0 kg/d), milk fat yield (1,549 g/d), milk fat content (3.66%), milk true protein yield (1,192 g/d), and milk urea N content (12.9 mg/dL) were not different among treatments. Postpartum DMI and body condition score were greater and the ratios of milk:DMI and milk N:feed N were less for cows fed the MetaSmart diet than for cows fed the control and Smartamine M diets. Milk protein content was greater for the Smartamine M (2.87%) and MetaSmart (2.81%) treatments than for the control treatment (2.72%). Concentrations of Met and Met + Cys in total plasma AA were different among treatments, with values for the Smartamine M treatment being the highest, followed by the MetaSmart and control treatments. The results indicated that both MetaSmart and Smartamine M are effective in providing metabolizable Met, but clarification of their relative contributions to metabolizable Met is still needed.     

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.     

Effect of different forms of methionine on lactational performance of dairy cows

Methionine is one of the first limiting AA in dairy cows. The use of rumen-protected Met to correct deficient diets is limited by the lack of a product that could be incorporated into a pelleted concentrate. The main objective of this trial was to test, at practical doses (approximately 10 g of absorbable Met), the efficacy of 2 forms of pelletable Met hydroxy analogs, d,l-2-hydroxy-4-(methylthio)-butanoic acid (HMB) and the isopropyl ester of HMB (HMBi), to provide Met to cows, especially for milk protein synthesis, compared with a negative control and to Smartamine M (SmM). These treatments were tested according to a 4 × 4 Latin square in 16 Holstein cows. Plasma Met concentrations were increased by 110 and 65% that of the control value after HMBi and SmM treatments, respectively. Milk protein yield increased by 32 and 41 g/d for HMBi and SmM, respectively. d,l-2-Hydroxy-4-(methylthio)-butanoic acid supplementation did not improve Met availability to the cows for milk protein synthesis. The HMBi treatment induced an increase in 15:0 in milk at the expense of a general reduction in even-numbered short-and medium-chain fatty acids. Moreover, HMBi and SmM supplements led to an increase in the saturation level of C₁₈ fatty acids consistent with the improvement of Met supply. It was concluded that HMBi is a new “rumen-protected” form of Met that can be supplied to cows integrated into pellets.     

Improving intestinal amino acid supply of pre- and postpartum dairy cows with rumen-protected methionine and lysine

Eighty-four Holstein cows were assigned to a randomized block experiment to determine effects of supplementing pre- and postpartum diets containing highLys protein supplements with rumen-protected Met and Lys. Before parturition, cows received a basal diet with 1) no rumen-protected amino acids (AA), 2) 10.5 g/d of Met from rumen-protected Met, or 3) 10.2 g/d of Met and 16.0 g/d of Lys from rumen-protected Met plus Lys. After parturition, cows continued to receive AA treatments but switched to diets balanced for 16.0 or 18.5% crude protein (CP). Diets were corn-based; supplemental protein was provided by soybean products and blood meal. Cows received treatments through d 105 of lactation. Compared with basal and Met-supplemented diets, Met + Lys supplementation increased yield of energy-corrected milk, fat, and protein, and tended to increase production of 3.5% fat-corrected milk. Significant CP x AA interactions were observed only for milk protein and fat content. Supplementation of the 16% CP diet with Met and Met + Lys had no effect on milk true protein and fat content. However, Met and Met + Lys supplementation of the 18.5% CP diet increased milk protein content by 0.21 and 0.14 percentage units, respectively, and Met supplementation increased fat content by 0.26 percentage units. Results of this study indicate that early-lactation cows fed corn-based diets are responsive to increased intestinal supplies of Lys and Met and that the responses depend on dietary CP concentration, supply of metabolizable protein, and intestinal digestibility of the rumen-undegradable fraction of supplemental proteins.     

Extent of methionine limitation in peak-, early-, and mid-lactation dairy cows

Five multiparous, ruminally and duodenally cannulated Holstein cows were assigned to 5 × 5 Latin squares at wk 2 (experiment 1), wk 11 to 13 (experiment 2), and wk 17 to 19 postpartum (experiment 3) to determine extent of Met limitation. Treatments were duodenally infused and consisted of 10 g/d of l-Lys plus 0, 3.5, 7.0, 10.5, or 16.0 g/d of dl-Met in experiments 1 and 2 and 8 g/d of l-Lys plus 0, 5, 10, 15, or 20 g/d of dl-Met in experiment 3. Calculated Lys contributions to total AA (TAA) in duodenal digesta for control treatments were 8.6, 7.5, and 9.0% for experiments 1, 2, and 3, respectively. Methionine contributions to TAA for the 5 infusion treatments were 1.9, 2.1, 2.2, 2.4, and 2.7% for experiment 1; 2.1, 2.3, 2.4, 2.5, and 2.7% for experiment 2; and 1.8, 2.0, 2.2, 2.4, and 2.5% for experiment 3, respectively. Milk protein yield increased linearly in experiments 1 and 2, indicating that Met contribution to TAA in duodenal digesta for maximal milk protein synthesis exceeded 2.7 for early-lactation cows. In experiment 2, a quadratic relationship was found between level of infused Met and milk protein content, with the response reaching a plateau when 12.2 g of Met was infused, corresponding with a Met contribution to TAA in duodenal digesta of 2.4%. In experiment 3, milk protein content increased quadratically, but milk yield declined linearly with increasing levels of infused Met; hence, milk protein yield was unaffected by treatment. The calculated plateau point of the milk protein content response curve was determined to be 12.4 g of infused Met, which corresponds to a Met contribution to TAA in duodenal digesta of 2.3%. Experiment 3 results indicate that the required level of Met in duodenal digesta for maximizing milk protein yield is lower than that required for maximizing milk protein content.     

A method to quantify changes in supply of metabolizable methionine to dairy cows using concentrations of selenium in milk

A method that accurately quantifies changes in the supply of metabolizable Met following a dietary change will allow accurate economic comparisons of various Met sources. This paper describes a novel method of estimating the relative supply of metabolizable Met based on changes in the concentration of Se in milk. Selenized yeast (Se-yeast) contains selenomethionine (Se-met) and because Se-met and Met are indistinguishable by cells, Se-met can be used as a tracer of Met. We hypothesized that if the size of the Met pool was increased but intake of Se-met was constant, the concentration of Se in milk relative to milk Met would decrease. To test this hypothesis, 6 Holstein cows were fed a diet that contained 0.3 mg of Se from Se-yeast/kg of diet DM and then in a 2-period crossover experiment, were abomasally infused with water (control) or an aqueous solution that provided 9 g of Met/d. Milk was sampled during the infusion and the specific activity (SA) of milk (Se concentration divided by Met concentration) was calculated for each treatment. The SA in milk from Met-infused cows was divided by SA in milk from control cows to calculate the change in supply of metabolizable Met. As hypothesized, infusing Met reduced the SA of milk (84.7 vs. 72.5 μg of Se/mg of Met). The calculated flow of metabolizable Met was 17% greater when cows were infused with 9 g of Met/d compared with cows infused with water (essentially the same difference was measured using SA calculated with N concentrations of milk). Assuming the infused Met was 100% absorbed, the flow of metabolizable Met for control cows was 9/0.17 = 53 g of Met/d, which agreed well with literature data and estimates derived from common nutritional models.     

Milk composition, milk fatty acid profile, digestion, and ruminal fermentation in dairy cows fed whole flaxseed and calcium salts of flaxseed oil

Four ruminally lactating Holstein cows averaging 602 ± 25 kg of body weight and 64 ± 6 d in milk at the beginning of the experiment were randomly assigned to a 4 × 4 Latin square design to determine the effects of feeding whole flaxseed and calcium salts of flaxseed oil on dry matter intake, digestibility, ruminal fermentation, milk production and composition, and milk fatty acid profile. The treatments were a control with no flaxseed products (CON) or a diet (on a dry matter basis) of 4.2% whole flaxseed (FLA), 1.9% calcium salts of flaxseed oil (SAL), or 2.3% whole flaxseed and 0.8% calcium salts of flaxseed oil (MIX). The 4 isonitrogenous and isoenergetic diets were fed for ad libitum intake. Experimental periods consisted of 21 d of diet adaptation and 7 d of data collection and sampling. Dry matter intake, digestibility, milk production, and milk concentrations of protein, lactose, urea N, and total solids did not differ among treatments. Ruminal pH was reduced for cows fed the CON diet compared with those fed the SAL diet. Propionate proportion was higher in ruminal fluid of cows fed CON than in that of those fed SAL, and cows fed the SAL and CON diets had ruminal propionate concentrations similar to those of cows fed the FLA and MIX diets. Butyrate concentration was numerically higher for cows fed the SAL diet compared with those fed the FLA diet. Milk fat concentration was lower for cows fed SAL than for those fed CON, and there was no difference between cows fed CON and those fed FLA and MIX. Milk yields of protein, fat, lactose, and total solids were similar among treatments. Concentrations of cis-9 18:1 and of intermediates of ruminal biohydrogenation of fatty acids such as trans-9 18:1 were higher in milk fat of cows fed SAL and MIX than for those fed the CON diet. Concentration of rumenic acid (cis-9, trans-11 18:2) in milk fat was increased by 63% when feeding SAL compared with FLA. Concentration of α-linolenic acid was higher in milk fat of cows fed SAL and MIX than in milk of cows fed CON (75 and 61%, respectively), whereas there was no difference between FLA and CON. Flaxseed products (FLA, SAL, and MIX diets) decreased the n-6 to n-3 fatty acid ratio in milk fat. Results confirm that flax products supplying 0.7 to 1.4% supplemental fat in the diet can slightly improve the nutritive value of milk fat for better human health.     

Effect of rumen-protected methionine on feed intake, milk production, true milk protein concentration, and true milk protein yield, and the factors that influence these effects: A meta-analysis

A meta-analysis of published studies was used to investigate the effect of rumen-protected methionine (RPM) added to the diets of lactating dairy cattle on dry matter intake, milk production, true milk protein (TMP) production, and milk fat yield. Differences in responses between 2 commonly used RPM products, Mepron (Evonik Industries, Hanau, Germany) and Smartamine (Adisseo, Antony, France), were investigated as well as dietary and animal factors that could influence responses. Diets were coded with respect to the amino acid (AA) deficiency of the control diet as predicted by the AminoCow model (version 3.5.2, http://www.makemilknotmanure.com/aminocow.php; 0 = no AA deficiency, 1 = Met deficiency, 2 = Met and Lys deficiency, 3 = Met and Lys plus at least 1 other AA deficiency) to test the effect of AA deficiencies on RPM response. Thirty-five studies were identified, 17 studies evaluating Mepron, 18 studies evaluating Smartamine, and 1 study evaluating both. This permitted 75 dietary comparisons between control and RPM-added diets. Diets were entered into the AminoCow and the 2001 National Research Council models to compare predictions of Met, Lys, and metabolizable protein (MP) flow. Mean Met and Lys in diets where RPM was fed were estimated to be 2.35 and 6.33% of MP, respectively. Predictions of flows between models were similar. Overall, RPM addition to diets increased production of TMP, both as percentage (0.07%) and yield (27 g/d). Dry matter intake and milk fat percentage were slightly decreased, whereas milk production was slightly increased. Differences between products were detected for all production variables, with Mepron-fed cows producing less TMP percentage but greater milk production, resulting in twice as much TMP yield. Milk protein response to RPM was not related to predicted AA deficiency, calculated Met deficiency, or Met as a percentage of MP. Other dietary factors, including Lys flow (g/d), Lys as percentage of MP, neutral detergent fiber percentage, crude protein percentage, or energy balance, had no detectable effects on TMP response. When cows with a predicted positive AA balance were fed RPM, milk production increased, but when AA balance was negative, milk production decreased. Amount of RPM added to the diet was not correlated to TMP response. This study does not support the necessity of a high Lys level as a prerequisite to obtaining a TMP response to feeding RPM or the MP requirement suggested by the National Research Council model (2001). However, more dose-response studies over a wide range of milk production and dietary regimens will be required to more clearly establish AA requirements and to predict responses to RPM supplementation.     

Effects of dietary conjugated linoleic acid on production and metabolic parameters in transition dairy cows grazing fresh pasture

Supplementation with a high dose (600 g/d) of rumen inert conjugated linoleic acids (RI-CLA) inhibits milk fat synthesis in total mixed ration (TMR)-fed dairy cows immediately post partum. However, effects of RI-CLA on milk fat and bioenergetic parameters during the transition period in grazing cows have not been investigated. Multiparous Holstein cows (n=39) grazing pasture were randomly assigned to one of three treatments: (1) pasture (PAS), (2) PAS+540 g/d Hyprofat (palm oil; HYPRO) and (3) PAS+600 g/d RI-CLA. HYPRO and RI-CLA supplements were isoenergetic, fed twice daily at 7.00 and 16.00 and provided 0 and 125 g CLA/d, respectively. Treatments began 27+/-10 d prepartum and continued until 36+/-1 days in milk (DIM). There was little or no overall effect of RI-CLA on content or yield of milk protein and lactose. RI-CLA supplementation decreased overall milk fat content and yield with RI-CLA-induced milk fat depression (MFD) becoming significant by day 3 when compared with PAS and by day 6 when compared with HYPRO. MFD continued to increase in severity during the first 24 d post partum after which MFD reached a plateau (approximately 40%; RI-CLA v. HYPRO). Pasture-fed cows produced less milk (19.4 kg/d) than the lipid-supplemented groups and although there were no overall differences in milk yield between RI-CLA and HYPRO (22.3 kg/d) a curvilinear relationship (R2=0.57) existed between the RI-CLA-induced milk yield response and extent of MFD. RI-CLA tended to increase milk yield (1.8 kg/d) compared with HYPRO until MFD exceeded 35% (approximately day 21), after which point the positive milk yield response was eliminated. Milk fat trans-10, cis-12 CLA content averaged 0.25 g/100 g in the RI-CLA treatment, was temporally independent, and was undetectable in PAS and HYPRO treatments. Based on the milk fat 14ratio1/14ratio0 ratio, RI-CLA decreased the overall Delta9-desaturase system compared with PAS and HYPRO. Compared with HYPRO, RI-CLA had no effect on plasma glucose, insulin, leptin, or NEFA concentrations. Results indicate that a high RI-CLA dose decreases milk fat synthesis and tends to increase milk yield immediately post partum in pasture-fed cows; however, excessive MFD (>35%) appears to be associated with a diminished milk yield response.     

Milk fatty acid composition of cows fed a total mixed ration or pasture plus concentrates replacing corn with fat

Thirty-one Holstein cows (six ruminally cannulated) were used to evaluate milk fatty acids (FA) composition and conjugated linoleic acid (CLA) content on three dietary treatments: 1) total mixed rations (TMR), 2) pasture (Avena sativa L.) plus 6.7 kg DM/d of corn-based concentrate (PCorn), and 3) pasture plus PCorn with 0.8 kg DM/d of Ca salts of unsaturated FA replacing 1.9 kg DM/d of corn (PFat). No differences were found in total (22.4 kg/d) or pasture (18.5 kg/d) dry matter intake, ruminal pH, or total volatile fatty acids concentrations. Fat supplementation did not affect pasture neutral detergent fiber digestion. Milk production did not differ among treatments (19.9 kg/d) but 4% fat-corrected milk was lower for cows fed the PFat compared to cows fed the TMR (16.1 vs. 19.5 kg/d) primarily because of the lower milk fat percentage (2.56 vs. 3.91%). Milk protein concentration was higher for cows fed the TMR than those on both pasture treatments (3.70 vs. 3.45%). Milk from the cows fed the PCorn had a lower content of short- (11.9 vs. 10.4 g/100 g) and medium-chain (56.5 vs. 47.6 g/100 g) FA, and a higher C18:3 percentage (0.07 vs. 0.57 g/100 g) compared with TMR-fed. Cows fed the PFat had the lowest content of short- (8.85 g/100 g) and medium-chain (41.0 g/100 g) FA, and the highest of long-chain FA (51.4 g/100 g). The CLA content was higher for cows in PCorn treatment (1.12 g/100 g FA) compared with cows fed the TMR (0.41 g/100 g FA), whereas the cows fed the PFat had the highest content (1.91 g/100 g FA). Pasture-based diets increased the concentrations of long-chain unsaturated FA and CLA in milk fat. The partial replacement of corn grain by Ca salts of unsaturated FA in grazing cows accentuated these changes. However, those changes in milk FA composition were related to a depression in milk fat.     

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.     

Long-term effects of feeding monensin on methane production in lactating dairy cows

The objective of this study was to determine the long-term effects of feeding monensin on methane (CH₄) production in lactating dairy cows. Twenty-four lactating Holstein dairy cows (1.46 ± 0.17 parity; 620 ± 5.9 kg of live weight; 92.5 ± 2.62 d in milk) housed in a tie-stall facility were used in the study. The study was conducted as paired comparisons in a completely randomized design with repeated measurements in a color-coded, double-blind experiment. The cows were paired by parity and days in milk and allocated to 1 of 2 treatments: 1) the regular milking cow total mixed ration (TMR) with a forage-to-concentrate ratio of 60:40 (control TMR; placebo premix) vs. a medicated TMR (monensin TMR; regular TMR + 24 mg of Rumensin Premix/kg of dry matter) fed ad libitum. The animals were fed and milked twice daily (feeding at 0830 and 1300 h; milking at 0500 and 1500 h) and CH₄ production was measured prior to introducing the treatments and monthly thereafter for 6 mo using an open-circuit indirect calorimetry system. Monensin reduced CH₄ production by 7% (expressed as grams per day) and by 9% (expressed as grams per kilogram of body weight), which were sustained for 6 mo (mean, 458.7 vs. 428.7 ± 7.75 g/d and 0.738 vs. 0.675 ± 0.0141, control vs. monensin, respectively). Monensin reduced milk fat percentage by 9% (3.90 vs. 3.53 ± 0.098%, control vs. monensin, respectively) and reduced milk protein by 4% (3.37 vs. 3.23 ± 0.031%, control vs. monensin, respectively). Monensin did not affect the dry matter intake or milk yield of the cows. These results suggest that medicating a 60:40 forage-to-concentrate TMR with 24 mg of Rumensin Premix/kg of dry matter is a viable strategy for reducing CH₄ production in lactating Holstein dairy cows.     

The feeding value of extruded corn grain in a corn silage-based ration for high-producing Holstein cows and heifers during mid lactation

The objective of this study was to investigate the feeding value of extruded corn in a corn silage-based ration for high-producing Holstein cows during mid lactation. Sixteen multiparous and 8 primiparous Holstein cows (106 ± 49.7 d in milk; 43.7 ± 5.27 kg of milk/d) were paired based on parity, days in milk, milk production, and body condition score and assigned to 1 of 2 dietary treatments in a randomized block design for 10 wk including a 2-wk adaptation period. Cows were fed a total mixed ration and milked 3 times per day. Diets contained 44% forage (3:1; corn silage:grass silage), 44.7% grain, and either extruded corn (EXC) or finely ground corn (FGC) at 11.3% of ration dry matter. No significant differences were detected in dry matter intake, milk protein yields, fat-corrected milk yields, or body condition score between cows fed FGC and cows fed EXC. Multiparous cows fed EXC produced more milk during wk 3 through 8 with a reduced milk fat content compared with multiparous cows fed FGC. Milk protein content was greater for primiparous cows fed EXC during wk 5 through 8 compared with primiparous cows fed the FGC ration. The major effect of feeding 2.7 kg/d of EXC compared with FGC was an increase in milk production and a reduction in milk fat content for multiparous cows, and an increase in milk protein content for primiparous cows.     

Effect of dietary protein concentration and degradability on response to rumen-protected methionine in lactating dairy cows

An incomplete 8 × 8 Latin square trial (4-wk periods; 12 wk total) using 32 multiparous and 16 primiparous Holstein cows was conducted to assess the production response to crude protein (CP), digestible rumen-undegraded protein (RUP), and rumen-protected Met (RPM; fed as Mepron; Degussa Corp., Kennesaw, GA). Diets contained [dry matter (DM) basis] 21% alfalfa silage, 34% corn silage, 22 to 26% high-moisture corn, 10 to 14% soybean meal, 4% soyhulls, 2% added fat, 1.3% minerals and vitamins, and 27 to 28% neutral detergent fiber. Treatments were a 2 × 2 × 2 factorial arrangement of the following main effects: 15.8 or 17.1% dietary CP, with or without supplemental rumen-undegraded protein (RUP) from expeller soybean meal, and 0 or 9 g of RPM/d. None of the 2- or 3-way interactions was significant. Higher dietary CP increased DM intake 1.1 kg/d and yield of milk 1.7 kg/d, 3.5% fat-corrected milk (FCM) 2.2 kg/d, fat 0.10 kg/d, and true protein 0.05 kg/d, and improved apparent N balance and DM and fiber digestibility. However, milk urea N and estimated urinary excretion of urea-N and total-N also increased, and apparent N efficiency (milk-N/N-intake) fell from 33 to 30% when cows consumed higher dietary CP. Positive effects of feeding more RUP were increased feed efficiency and milk fat content plus 1.8 kg/d greater FCM and 0.08 kg/d greater fat, but milk protein content was lower and milk urea N and urinary urea excretion were elevated. Supplementation with RPM increased DM intake 0.7 kg/d and FCM and fat yield by 1.4 and 0.06 kg/d, and tended to increase milk fat content and yield of milk and protein.     

Effects of feeding rumen-protected methionine pre- and postpartum in multiparous Holstein cows: Health disorders and interactions with production and reproduction

Study objectives were to evaluate the effects of feeding rumen-protected Met (RPM) in pre- and postpartum total mixed rations (TMR) on health disorders and the interactions of health disorders with lactation and reproductive performance. Multiparous Holstein cows [470; 235 cows at University of Wisconsin (UW) and 235 cows at Cornell University (CU)] were enrolled at approximately 4 wk before parturition and housed in close-up dry cow (n = 6) and replicated lactation pens (n = 16). Pens were randomly assigned to treatment diets (pre- and postpartum, respectively): (1) control (CON): basal diet = 2.30% and 2.09% Met as % of metabolizable protein (MP) (UW) or 2.22% and 2.19% Met as % of MP (CU); (2) RPM: basal diet fed with RPM with 2.83% and 2.58% Met (Smartamine M, Adisseo Inc.; 12 g prepartum and 27 g postpartum), as % of MP (UW) or 2.85% and 2.65% Met (Smartamine M; 13 g prepartum and 28 g postpartum), as % of MP (CU). Total serum Ca was evaluated at the time of parturition and on d 3 ± 1 postpartum. Daily rumination was monitored from 7 d before parturition until 28 d postpartum. Health disorders were recorded during the experimental period until the time of first pregnancy diagnosis (32 d after timed artificial insemination; 112 ± 3 d in milk). Uterine health was evaluated on d 35 ± 3 postpartum. Time to pregnancy and herd exit were evaluated up to 350 d in milk. Treatment had no effect on the incidence of most health disorders and did not alter daily rumination. Cows fed RPM had reduced subclinical hypocalcemia (13.6 vs. 22%; UW only) on day of parturition relative to CON. Percentage of cows culled (13.1 vs. 19.3%) and hazard of herd exit due to culling [hazard ratio = 0.65, 95% confidence interval (CI): 0.42–1.02] tended to be reduced for cows fed RPM compared with CON. Moreover, cows fed RPM had greater milk protein concentration and protein yield overall, although retrospective analysis indicated that RPM only significantly increased protein yield in the group of cows with one or more health disorders (1.47 vs. 1.40 kg/d), not in cows without health disorders (1.49 vs. 1.46 kg/d) compared with CON. Overall, treatment had no effect on pregnancy per timed artificial insemination; however, among cows with health disorders, those fed RPM had reduced time to pregnancy compared with CON (hazard ratio = 0.71, 95% CI: 0.53–0.96). Thus, except for subclinical hypocalcemia on the day of parturition, feeding RPM in pre- and postpartum TMR did not reduce the incidence of health disorders, but our retrospective analysis indicated that it lessened the negative effects of health disorders on milk protein production and time to pregnancy.     

Effects of feedborne Fusarium mycotoxins on the performance, metabolism, and immunity of dairy cows

Little is known about the effects of feedborne Fusarium mycotoxins on the performance, metabolism, and immunity of dairy cattle. A total mixed ration (TMR) containing a blend of feedstuffs naturally contaminated with Fusarium mycotoxins was fed for 56 d to 18 midlactation Holstein cows (average milk production, 33 kg/d) in a completely randomized design with repeated measures that included 3 treatments: 1) a control diet, 2) a contaminated diet, and 3) a contaminated diet + 0.2% polymeric glucomannan mycotoxin adsorbent (GMA). Wheat, corn, and hay were the contaminated feedstuffs used in the study. Deoxynivalenol was the major contaminant and was found in the TMR at levels of up to 3.6 μg/g of dry matter. Body weight, body condition score, dry matter intake, net energy balance, milk production, milk composition, somatic cell count, blood serum chemistry, hematology, serum Ig concentrations, and coagulation profile were measured. Dry matter intake and body weight, as well as milk production, milk composition, and SCC, were not affected by diet. Total serum protein and globulin levels increased significantly in cows fed the contaminated TMR compared with cows fed the control diet at 42 d, whereas the albumin:globulin ratio decreased. Serum urea concentrations were significantly elevated throughout the experiment in cows fed the contaminated diet compared with those fed the control diet. Serum IgA concentrations decreased significantly in cows fed the contaminated TMR at 36 d of feeding. Feeding GMA prevented these effects. Serum sodium concentration and osmolality levels were increased throughout the experiment in all cows fed the contaminated diets. We concluded that feed naturally contaminated with Fusarium mycotoxins can affect the metabolic parameters and immunity of dairy cows and that GMA can prevent some of these effects.     

Supplemental Smartamine M or MetaSmart during the transition period benefits postpartal cow performance and blood neutrophil function

The onset of lactation in dairy cows is characterized by severe negative energy and protein balance. Methionine availability during this time for milk production, hepatic lipid metabolism, and immune function may be limiting. Supplementing Met to peripartal diets with adequate Lys in metabolizable protein (MP) to fine-tune the Lys:Met ratio may be beneficial. Fifty-six multiparous Holstein cows were fed the same basal diet from 50 d before expected calving to 30 d in milk. From −50 to −21 d before expected calving, all cows received the same diet [1.24 Mcal/kg of dry matter (DM), 10.3% rumen-degradable protein, and 4% rumen-undegradable protein] with no Met supplementation. From −21 d to expected calving, the cows received diets (1.54 Mcal/kg of DM, 10% rumen-degradable protein, and 5.1% rumen-undegradable protein) with no added Met (control, CON; n = 14), CON plus MetaSmart (MS; Adisseo Inc., Antony, France; n = 12), or CON plus Smartamine M (SM; Adisseo Inc.; n = 12). From calving through 30 d in milk, the cows received the same postpartum diet (1.75 Mcal/kg of DM and 17.5% CP; CON), or the CON plus MS or CON plus SM. The Met supplements were adjusted daily and top-dressed over the total mixed ration at a rate of 0.19 or 0.07% (DM) of feed for MS or SM. Liver tissue was collected on −10, 7, and 21 d, and blood samples more frequently, from −21 through 21 d. Data were analyzed using the MIXED procedure of SAS (SAS Institute Inc., Cary, NC) with the preplanned contrasts CON versus SM + MS and SM versus MS. No differences in prepartal DM intake (DMI) or body condition score were observed. After calving, body condition score was lower (2.6 vs. 2.8), whereas DMI was greater (15.4 vs. 13.3 kg/d) for Met-supplemented cows. Postpartal diet × time interactions were observed for milk fat percentage, milk fat yield, energy-corrected milk:DMI ratio, and energy balance. These were mainly due to changes among time points across all treatments. Cows supplemented with either Met source increased milk yield, milk protein percentage, energy-corrected milk, and milk fat yield by 3.4 kg/d, 0.18% units, 3.9 kg/d, and 0.18 kg/d, respectively. Those responses were associated with greater postpartum concentration of growth hormone but not insulin-like growth factor 1. There was a diet × time effect for nonesterified fatty acid concentration due to greater values on d 7 for MS; however, liver concentration of triacylglycerol was not affected by diet or diet × time but increased postpartum. Blood neutrophil phagocytosis at 21 d was greater with Met supplementation, suggesting better immune function. Supplemental MS or SM resulted in a tendency for lower incidence of ketosis postpartum. Although supplemental MS or SM did not decrease liver triacylglycerol, it improved milk production-related traits by enhancing voluntary DMI.