This experiment was conducted with the objective to investigate the effects of slow-release urea and rumen-protected (RP) Met and His supplementation of a metabolizable protein (MP)-deficient diet (according to NRC, 2001) on lactation performance of dairy cows. Sixty lactating Holstein cows were used in a 10-wk randomized complete block-design trial. Cows were fed a covariate diet for 2 wk and then assigned to one of the following treatments for an 8-wk experimental period: (1) MP-adequate diet [AMP; 107% of MP requirements, based on the National Research Council (NRC, 2001)]; (2) MP-deficient diet (DMP; 95% of MP requirements); (3) DMP supplemented with slow-release urea (DMPU); (4) DMPU supplemented with RPMet (DMPUM); and (5) DMPUM supplemented with RPHis (DMPUMH). Total-tract apparent digestibility of dry matter, organic matter, neutral detergent fiber, and crude protein, and urinary N and urea-N excretions were decreased by DMP, compared with AMP. Addition of slow-release urea to the DMP diet increased urinary urea-N excretion. Dry matter intake (DMI) and milk yield (on average 44.0±0.9kg/d) were not affected by treatments, except DMPUMH increased DMI and numerically increased milk yield, compared with DMPUM. Milk true protein concentration and yield were increased and milk fat concentration tended to be decreased by DMPUMH, compared with DMPUM. Cows gained less body weight on the DMP diet, compared with AMP. Plasma concentrations of His and Lys were not affected by treatments, whereas supplementation of RPMet increased plasma Met concentration. Plasma concentration of 3-methylhistidine was or tended to be higher for DMP compared with AMP and DMPU, respectively. Addition of RPHis to the DMPUM diet tended to increase plasma glucose and creatinine. In conclusion, feeding a 5% MP-deficient diet (according to NRC, 2001) did not decrease DMI and yields of milk and milk components, despite a reduction in nutrient digestibility. Supplementation of RPHis increased DMI and milk protein concentration and yield. These results are in line with our previous data and suggest that His may have a positive effect on voluntary feed intake and milk production and composition in high-yielding dairy cows fed MP-deficient diets.

Two studies were performed to evaluate the effects of dried distillers grains with solubles (DDGS) on the lactational performance of dairy cows. The intent of experiment 1 was to evaluate the effects of feeding increasing concentrations of DDGS on the feed intake and production of Holstein dairy cows. Twenty multiparous Holstein cows averaging 76 ± 24 d in milk and 638 ± 68 kg of body weight were randomly assigned to one of five 4 × 4 Latin squares. During each of the 28-d periods, cows were offered 1 of 4 diets: 1) control, 0% DDGS, 2) 10% DDGS, 3) 20% DDGS, or 4) 30% DDGS. For the treatment diets, DDGS replaced a portion of both forages and concentrates. Dry matter intake increased linearly with increasing concentrations of DDGS (21.4, 22.4, 23.0, and 24.0 ± 0.98 kg/d). Similarly, milk production increased linearly (27.4, 28.5, 29.3, and 30.6 ± 1.44 kg/d). The intent of experiment 2 was to evaluate the effect of feeding DDGS on feed intake, milk production, and excretion of urinary purine derivatives (PD). Excretion of PD was used to estimate the effects on rumen microbial crude protein production. Twenty-one multiparous and 13 primiparous Holstein cows, averaging 178 ± 36 d in milk and 651 ± 65 kg of body weight were randomly assigned to 1 of 2 diets in a 3-period crossover design. Cows were offered 1 of 2 rations during each 21-d period. Dietary treatments were either a control (0% DDGS) or 30% dietary dry matter of DDGS. Dry matter intake increased when feeding DDGS (22.8 vs. 24.1 ± 0.74 kg/d for 0 and 30% DDGS, respectively) but milk production, percentages of milk fat and protein, and the ratio of PD to creatinine were not significantly different between the control and DDGS diets. Results of this study suggest a dairy ration may be formulated to contain as much as 30% of dietary dry matter as DDGS.

Twenty midlactation Holstein cows (4 ruminally fistulated) averaging 101 ± 34 d in milk and weighing 674 ± 77 kg were used to compare rations with brown midrib corn silage (bm3) to rations with dual-purpose control silage (DP) on N utilization and milk production. The effect of monensin in these rations was also examined. Animals were assigned to one of five 4 × 4 Latin squares with treatments arranged in a 2 × 2 factorial. Cows were fed 1 of 4 treatments during each of the four 28-d periods. Treatments were 1) 0 mg/d monensin and bm3 corn silage, 2) 0 mg/d monensin and DP corn silage, 3) 300 mg/d monensin and bm3 corn silage, and 4) 300 mg/d monensin and DP corn silage. In vitro 30-h neutral detergent fiber (NDF) digestibility was greater for bm3 corn silage (61.0 vs. 49.1 ± 0.62). Dry matter intake (DMI) tended to be greater for cows consuming bm3 corn silage (21.3 vs. 20.2 kg/d). Neither hybrid nor monensin affected milk production, fat, or protein (37.7 kg, 3.60%, or 3.04%). Monensin tended to increase rumen pH (5.89 vs. 5.79 ± 0.07) compared with the control treatment. In addition, bm3 corn silage resulted in a significant decrease in rumen pH (5.72 vs. 5.98 ± 0.07). Supplementing monensin had no effect on molar proportions of acetate, propionate, or butyrate. In contrast, an increase was observed in branched-chain volatile fatty acids. No treatment interactions were observed for rumen pH or molar proportion of propionate but monensin decreased the molar proportion of acetate and increased the molar proportion of butyrate when cattle consumed bm3 silage. Dry matter, N, and acid detergent fiber digestibility were lower for the bm3 ration, whereas NDF digestibility was not different between treatments. There was no effect of hybrid on Corresponding author: pkononoff2@unl.edu 288 microbial protein synthesis (1,140 g/d) as estimated by urinary concentration of purine derivatives. Cows consuming bm3 excreted more fecal N than cows consuming DP (38.2 vs. 34.4% N intake); however, based on spot sampling, estimated urinary and manure N were not different between treatments (35.8 and 71.9% N intake). Monensin had no effect on DMI, digestibility of any nutrients, or N metabolism, and there were no hybrid by monensin interactions. Rations including bm3 corn silage tended to increase DMI but did not affect production. The reduction in the digestibility of some nutrients when cows consumed bm3 may have been caused by increased DMI and possible increased digestion in the lower gut. This increase in DMI appeared to also have negatively affected N digestibility but not NDF digestibility. This resulted in a greater amount of N excreted in feces but did not affect total mass of manure N.

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

The objective of this study was to determine if feeding carbohydrate supplements with faster degradation rates than corn to dairy cows grazing ryegrass would improve nitrogen capture, milk production, and components. Treatments were grain supplements based on: 1) corn (CORN), 2) barley and molasses (BM), or 3) citrus pulp and molasses (CM). For BM and CM, the diet composition was the same as that of CORN except that a portion of the corn was replaced with barley and molasses or citrus pulp and molasses, respectively, on a dry matter basis. Cows grazed ryegrass (Lolium multiflorum Lam.) pasture. Yield of milk, 3.5% fat-corrected milk, energy-corrected milk, and milk fat, as well as milk fat percentage, were not different among treatments. True milk protein percentage was higher for CORN (2.81%) compared with CM (2.70%), but was not different for BM (2.77%). However, true milk protein yield was not different among treatments. Milk urea N was higher for BM (11.43 mg/dL) compared with both CORN and CM (average: 9.95 mg/dL). There were no differences among CORN, BM, and CM treatments for overall BUN (average: 10.60 mg/dL). At 0400 h, however, cows on CORN had higher BUN than cows on CM (11.43 vs. 9.96 mg/dL), but there were no differences between CORN and BM (average: 11.21 mg/dL) or BM and CM (average: 10.48 mg/dL), and there were no differences among treatments at other time points. The CM diet might have shown more advantage if the pasture crude protein content was higher. Partial replacement of corn with citrus pulp for grazing cows should be further studied using pasture with higher crude protein content. Although cows receiving CM and BM did not produce more milk than cows on CORN, if barley or citrus pulp is less expensive than corn, they may be

The objective of this study was to examine the effects substituting soybean meal with a yeast-derived microbial protein (YMP) on rumen and blood metabolites, dry matter intake, and milk production of high-producing dairy cows. Sixteen Holstein cows (12 multiparous and 4 primiparous), 93 ± 37 DIM (mean ± SD) at the beginning of the experiment, were used in a 4×4 Latin square design with four 28-d periods. Cows were blocked by parity and production, with 1 square consisting of 4 animals fitted with rumen cannulas. Basal diets, formulated for 16.1% crude protein and 1.56 Mcal/kg of net energy for lactation, contained 40% corn silage, 20% alfalfa hay, and 40% concentrate mix. During each period, cows were fed 1 of 4 treatment diets corresponding to YMP (DEMP; Alltech Inc., Nicholasville, KY) concentrations of 0, 1.14, 2.28, and 3.41% DM. Soybean meal (44% CP) was replaced by YMP to attain isonitrogenous and isoenergetic diets. Dietary treatments had no effect on pH and on most ruminal volatile fatty acid concentrations, with the exception of isovalerate, which decreased linearly with the addition of YMP. Rumen ammonia concentration decreased linearly, whereas free amino acids, total amino acid nitrogen, and soluble proteins weighing more than 10 kDa showed a cubic response on rumen N fractionation. A quadratic response was observed in oligopeptides that weighed between 3 and 10 kDa and peptides under 3kDa when expressed as percentages of total amino acids and total nitrogen. Although nonesterified fatty acid concentration in blood did not differ between treatments, β-hydroxybutyrate and plasma glucose increased linearly as YMP increased. Dry matter intake showed a cubic effect, where cows fed 1.14, and 3.41% YMP had the highest intake. Milk production was not affected by YMP, whereas a trend was observed for a quadratic increase for 4% fat-corrected milk and energy-corrected milk. Medium- and long-chain fatty acid concentrations in milk increased quadratically, which elicited similar effects on milk fat concentration and yield. Total solids percentage and yield, and milk urea nitrogen also showed quadratic effects as YMP increased in the diet. No effects were observed on feed efficiency, milk protein, and lactose percentage or yield. A complementary in vitro study demonstrated a quadratic tendency for apparent and true dry matter digestibility as YMP was added to the diet. It was concluded that the substitution of soybean meal with YMP increased the percentage of total solids in milk and tended to improve energy-corrected and fat-corrected milk production in high-producing dairy cows consuming high-forage diets.

Concern over the carbon footprint of the dairy industry has led to various dietary approaches to mitigate enteric CH 4 production. One approach is feeding the electron acceptor NO 3 − yield. Based on the fact that few interactions were detected, LYC had a minimal role in attenuating negative cow responses to NO 3 − supplementation.

Nitrates have been fed to ruminants, including dairy cows, as an electron sink to mitigate CH 4 emissions. In the NO 3 − reduction process, NO 2 − can accumulate, which could directly inhibit methanogens and possibly other microbes in the rumen. Saccharomyces cerevisiae yeast was hypothesized to decrease NO 2 − through direct reduction or indirectly by stimulating the bacterium Selenomonas ruminantium, which is among the ruminal bacteria most well characterized to reduce both NO 3 − and NO 2 −. Ruminal fluid was incubated in continuous cultures fed diets without or with NaNO 3 (1.5% of diet dry matter; i.e., 1.09% NO 3 −) and without or with live yeast culture (LYC) fed at a recommended 0.010 g/d (scaled from cattle to fermentor intakes) in a 2 × 2 factorial arrangement of treatments. Treatments with LYC had increased NDF digestibility and acetate: propionate by increasing acetate molar proportion but tended to decrease total VFA production. The main effect of NO 3 − increased acetate: propionate by increasing acetate molar proportion; NO 3 − also decreased molar proportions of isobutyrate and butyrate. Both NO 3 − and LYC shifted bacterial community composition (based on relative sequence abundance of 16S rRNA genes). An interaction occurred such that NO 3 − decreased valerate molar proportion only when no LYC was added. Nitrate decreased daily CH 4 emissions by 29%. However, treatment × time interactions were present for both CH 4 and H 2 emission from the headspace; CH 4 was decreased by the main effect of NO 3 − until 6 h postfeeding, but NO 3 − and LYC decreased H 2 emission up to 4 h postfeeding. As expected, NO 3 − decreased methane emissions in continuous cultures; however, contrary to expectations, LYC did not attenuate NO 2 − accumulation.