Effects of increasing levels of grain supplementation on rumen environment and lactation performance of dairy cows grazing grass-legume pasture

The impact of supplemental energy on nutrient utilization, fiber digestion, rumen fermentation, and lactation performance was evaluated in dairy cows grazing pastures composed of brome, orchardgrass, red clover, and alfalfa. Three amounts [0, 5, and 10 kg dry matter (DM)/d] of ground dry shelled corn-based concentrate were supplemented to nine rumen cannulated Holstein cows in a 3 x 3 Latin square replicated three times. Cows were on average 84+/-13 d in milk and producing 41.6+/-5.9 kg of milk/d at the beginning of the study. An increase in amounts of concentrate in the diets was associated with an increase in milk production, solids-corrected milk, and concentrations of milk protein and SNF. Milk fat percentage and milk urea nitrogen concentration decreased linearly with supplementation. Milk production and protein percentage were 21.8, 26.8, and 30.4 kg/d, and 2.85, 2.95, and 3.05% for the increasing levels of concentrate, respectively. Intake and digestibility of DM and organic matter (OM) increased as grain supplementation increased. Ruminal pH and total volatile fatty acid concentration (VFA) were not affected by supplementation or the amount of concentrate. Ruminal ammonia concentration was reduced by supplementation, presumably due to a decrease in N intake and greater use of ammonia-N for rumen microbial protein synthesis. Rumen fermentation varied throughout the day, with lower mean pH and higher VFA concentrations at night. Supplementation increased total OM intake, decreased forage OM intake, and increased the proportion of OM that was digested in the intestines. Total DM intake by grazing dairy cows can be increased using ground dry shelled corn-based concentrate without causing negative effects on forage digestion.     

Effects of supplemental hay and corn silage versus full-time grazing on ruminal pH and chewing activity of dairy cows

Grazing young, highly digestible swards with and without supplemental hay or corn silage (5.5 kg of DM/d) offered overnight was tested for its effects on ruminal pH and chewing activity. A double 3 x 3 Latin square arrangement with 6 rumen-cannulated Brown Swiss cows (29 kg/d of milk) was applied. Herbage intake was quantified by controlled-release alkane capsules. Chewing activity was determined using an automatic microcomputer-based system for digital recording of the jaw movements. Except during milking, ruminal pH was measured continuously over 7 d by applying a device consisting of an indwelling pH electrode and a data-recording unit integrated in the cannula's cover. The grazing system had no significant effect on body weight, milk yield or composition (except milk urea), or total DM intake (13.5, 13.8, and 15.7 kg/d with full-time grazing, hay, and corn silage supplementation). No differences occurred for ruminating time per day and time per kilogram of DM intake. Full-time grazing cows spent more time eating per day (+26%) and time per kilogram of DM intake (+31%) than the other cows. Ruminal pH and time with pH <5.8 at night did not differ. Throughout the day, hay-supplemented cows had a significantly lower pH (-0.23) than full-time grazing cows, and the period of pH <5.8 was longer compared with corn-silage fed cows (77 vs. 11 min). Nocturnal supplement feeding gave no advantage over full-time grazing, and supplemental hay led to lower daytime pH.     

Supplemental dietary protein for grazing dairy cows: effect on pasture intake and lactation performance

One hundred twenty-four cows (92 multiparous and 32 primiparous) were used to evaluate the effect of grain supplements containing high crude protein [(22.8% CP, 5.3% rumen undegradable protein (RUP), dry matter basis], moderate CP (16.6% CP, 6.1% RUP), and moderate CP with supplemental RUP (16.2% CP, 10.8% RUP) on lactation performance of Holstein cows rotationally grazing annual ryegrass-oat pastures. Supplemental protein was provided by solvent extracted soybean meal in the high CP and moderate CP supplements and as a corn gluten meal-blood meal mixture (2.8:1) in the moderate CP, high RUP supplement. Cows were blocked according to previous mature milk equivalent production and calving date (partum group; 0 d in milk or postpartum group; 21 to 65 d in milk) and randomly assigned to dietary treatments. Grain was individually fed, at approximately a 1:3 grain to milk ratio, before a.m. and p.m milkings. The study was replicated during two grazing seasons that averaged 199 d. Cows had ad libitum access to bermudagrass hay while on pasture (dry matter intake = 1.3 kg/d). Protein supplementation had no effect on study long pasture dry matter (12.7 +/- 1.0 kg/d) or total dry matter (23.9 +/- 1.2 kg/d) consumption. Protein concentration did not affect actual milk yield of either calving group (high CP vs. moderate CP); however, postpartum group cows receiving high CP grain supplements maintained greater milk fat concentrations (3.34 vs. 3.11%), which led to higher fat-corrected milk (FCM) yields than control cows receiving moderate CP grain diets (30.3 vs. 28.9 kg/d). Crude protein concentration in milk of high CP-supplemented, postpartum group cows was also higher than moderate CP cows (3.42 vs. 3.27%). Additional RUP did not increase FCM yield above that generated by moderate CP grain diets for partum (34.3 vs. 32.9 kg/d) or postpartum-group cows (28.9 vs. 28.2 kg/d). Increasing CP concentration of grain supplement did not affect milk yield of Holstein cows grazing immature winter annual pastures. Supplementing additional RUP was without benefit, indicating that in this study energy deprivation may have been the major nutritional constraint for high-producing dairy cows grazing lush pastures.     

Replacing alfalfa hay with dry corn gluten feed and Chinese wild rye grass: Effects on rumen fermentation,rumen microbial protein synthesis,and lactation performance in lactating dairy cows

This experiment was conducted to investigate nutrient digestibility, rumen microbial protein synthesis, and lactation performance when a portion of alfalfa was replaced with combinations of dry corn gluten feed (DCGF) and Chinese wild rye grass in the diet of lactating cows. Six multiparous and 3 primiparous Chinese Holsteins were arranged in a replicated 3 × 3 Latin square experiment for 21-d periods. The animals were fed 1 of 3 treatment diets during each period: (1) 0% DCGF (0DCGF); (2) 6.5% DCGF (7DCGF); and (3) 11% DCGF (11DCGF). Diets were isonitrogenous, and a portion of alfalfa hay was replaced with DCGF and Chinese wild rye grass, with similar concentrate mixtures and corn silage contents. The dry matter intake was greater for 11DCGF (21.9 kg/d) than for 0DCGF (20.7 kg/d) or 7DCGF (21.2 kg/d). The treatment diets did not result in difference in milk production, fat and lactose concentration, or yield. Compared with 0DCGF, the ration containing 11% DCGF improved the milk protein concentration. Dry matter and neutral detergent fiber digestibility was greater for 7DCGF (62.7% and 45.6%) and 11DCGF (63.1% and 47.2%) than for 0DCGF (59.4% and 42.3%), and the nitrogen digestibility was similar for the 3 treatments. The concentration of rumen volatile fatty acids was higher in cows fed the 11DCGF diet than in those fed the 0DCGF diet, with no difference between the 7DCGF and 11DCGF diets. The estimated microbial crude protein yield was greater for the 11DCGF diet (1985.1 g/d) than for the 0DCGF diet (1745.0 g/d), with no difference between the 0DCGF and 7DCGF diets. Thus, it appears that feeding DCGF and Chinese wild rye grass in combination can effectively replace a portion of alfalfa hay in the rations of lactating dairy cows.     

Short communication: Responses to supplemental Saccharomyces cerevisiae fermentation product and triticale grain in dairy cows grazing high-quality pasture in early lactation

Supplementing cows grazing highly digestible pasture with a Saccharomyces cerevisiae fermentation product (SCFP) was hypothesized to increase dry matter (DM) intake and milk production. Sixty multiparous dairy cows were fed 3 kg of crushed triticale DM/cow per day for 23 ± 4.4 d before calving. Half of the cows received SCFP (60 g/d; Diamond V Original XP; Diamond V Mills, Inc., Cedar Rapids, IA). Cows in both treatment groups were randomly allocated at calving to 1 of 2 amounts (3 or 6 kg of DM/d) of triticale feeding with or without 60 g of SCFP/day (n = 15/treatment) until 84 days in milk. The amount of pasture harvested (kg of DM/cow per day) and milk yield (kg/cow per day) were not affected by SCFP. Milk protein content and yield were greater in cows receiving 6 kg of crushed triticale DM/d. Plasma nonesterified fatty acids and β-hydroxybutyrate concentrations were not affected by SCFP supplementation, but were lower in cows fed 6 kg of crushed triticale DM/d than those fed 3 kg of DM/d. Supplementation with SCFP increased milk lactose content without affecting milk production under the conditions investigated.     

Influence of corn silage hybrid type on lactation performance by Holstein dairy cows

The primary objective of this study was to determine lactation performance by dairy cows fed nutridense (ND), dual-purpose (DP), or brown midrib (BM) corn silage hybrids at the same concentration in the diets. A secondary objective was to determine lactation performance by dairy cows fed NutriDense corn silage at a higher concentration in the diet. One hundred twenty-eight Holstein and Holstein × Jersey cows (105 ± 38 d in milk) were stratified by breed and parity and randomly assigned to 16 pens of 8 cows each. Pens were then randomly assigned to 1 of 4 treatments. Three treatment total mixed rations (TMR; DP40, BM40, and ND40) contained 40% of dry matter (DM) from the respective corn silage hybrid and 20% of DM from alfalfa silage. The fourth treatment TMR had ND corn silage as the sole forage at 65% of DM (ND65). A 2-wk covariate adjustment period preceded the treatment period, with all pens receiving a TMR with equal proportions of DP40, BM40, and ND40. Following the covariate period, cows were fed their assigned treatment diets for 11 wk. nutridense corn silage had greater starch and lower neutral detergent fiber (NDF) content than DP or BM, resulting in ND40 having greater energy content (73.2% of total digestible nutrients, TDN) than DP40 or BM40 (71.9 and 71.4% TDN, respectively). Cows fed BM40 had greater milk yield than DP40, whereas ND40 tended to have greater milk yield and had greater protein and lactose yields compared with DP40. No differences in intake, component-corrected milk yields, or feed efficiency were detected between DP40, BM40, and ND40. Milk yield differences may be due to increased starch intake for ND40 and increased digestible NDF intake for BM40 compared with DP40. Intake and milk yield and composition were similar for ND40 compared with BM40, possibly due to counteracting effects of higher starch intake for ND40 and higher digestible NDF intake for BM40. Feeding ND65 reduced intake, and thus milk and component yields, compared with ND40 due to either increased ruminal starch digestibility or increased rumen fill for ND65. Nutridense corn silage was a viable alternative to both DP and BM at 40% of diet DM; however, lactation performance was reduced when nutridense corn silage was fed at 65% of DM.     

Effects of corn particle size and source on performance of lactating cows fed direct-cut grass-legume forage

We conducted two experiments to evaluate the effects of corn supplementation, source of corn, and corn particle size on performance and nutrient utilization of lactating dairy cows. In experiment 1, treatments were 1) direct-cut grass-legume forage without supplement, 2) direct-cut forage plus 10 kg DM of ground dry shelled corn-based concentrate, and 3) direct-cut forage plus 10 kg DM of coarsely ground high moisture ear corn-based concentrate. In experiment 2, treatments were 1) direct-cut grass-legume forage plus 10 kg DM of ground dry shelled corn-based concentrate, 2) direct-cut forage plus 10 kg DM of coarsely ground high moisture ear corn-based concentrate, and 3) direct-cut forage plus 10 kg of DM finely ground high moisture ear corn-based concentrate. Both experiments were designed as 3 x 3 Latin squares replicated three times. In experiment 1, yields of milk and milk protein increased with concentrate supplementation, but were not affected by source of corn. Solids-corrected milk yield tended to increase with grain supplementation. Dry matter intake increased with concentrate supplementation, but was not affected by source of corn or corn particle size. Corn supplements decreased ruminal pH and acetate to propionate ratio and increased ruminal propionate concentration. Grain supplements reduced ruminal ammonia concentration, increased concentration of urine allantoin, and increased the urinary allantoin to creatinine ratio. In the second study, fine grinding of high moisture corn reduced fecal starch plus free glucose levels and tended to increase its apparent digestibility. In both experiments, starch plus free glucose intake was higher on the diets with dry corn, but its utilization was not affected by source of corn.     

Effect of supplemental concentrate type on milk production and metabolic status in early-lactation dairy cows grazing perennial ryegrass-based pasture

Forty-four early-lactation dairy cows of mixed parity were used to examine the effect of 4 supplemental concentrate types (n=11) on milk production and metabolic status. Animals were blocked by parity and calving date, and blocks were balanced for previous milk yield and milk protein yield. Cows received grazed pasture plus 5.17 kg of DM/d of 1 of the following isoenergetic (1.1 units of energy for lactation) concentrates: 1) high crude protein (CP) with rolled barley (HP, 19% CP); b) low CP with rolled barley (LP, 15% CP); c) low CP with barley and a supplemental methionine hydroxy analog (HMBi; LP + HMBi, 15% CP); and d) low CP with ground corn (LP-corn, 15% CP). Milk yield was recorded from d 1 to 100 postpartum, with weekly milk sampling, body weight, and body condition score (BCS) measurements. Blood and rumen sampling were conducted weekly from wk 2 to 6 postpartum. Milk yield was lower for cows in the LP treatment compared with those offered other concentrate types (25.2 vs. 27.5 ± 0.39 kg/d). Animals in the HP group had a higher milk yield than those in the LP + HMBi group (28.2 vs. 26.8 ± 0.39 kg/d). Milk fat yield was lower from animals in the LP-corn group compared with those in the LP + HMBi group (0.94 vs. 1.03 ± 0.03 kg/d). Milk protein yield was lower in the LP group compared with those in the HP group (0.88 vs. 0.97 ± 0.02 kg/d). Animal body weight, BCS, and BCS loss were not affected by concentrate type. However, nonesterified fatty acids were higher from animals in the HP group than for those in the LP + HMBi group (0.41 vs. 0.33 ± 0.03 mmol/L), and β-hydroxy butyric acid was higher from animals in the HP group than for those in the other treatments (0.71 vs. 0.59 ± 0.03 mmol/L). Glucose was higher from animals in the LP-corn group than for those in the HP and LP groups (3.3 vs. 3.2 ± 0.05 mmol/L). Blood urea-N was higher from animals offered HP compared with those offered the other treatments (5.49.6 vs. 4.21 ± 0.44 mmol/L). However, rumen NH(3)-N and volatile fatty acid concentration in the rumen were not affected by supplemental concentrate type. Reducing supplemental concentrate CP reduced milk yield. However, milk fat production and energy-corrected milk were not different, reducing the likelihood of an improved energy balance or a more favorable blood metabolic profile in early-lactation dairy cows grazing perennial ryegrass. Offering HMBi with low-CP concentrates or replacing rolled barley with ground maize improves milk production relative to low-CP concentrates and metabolic status relative to high-CP concentrates.     

Partial replacement of corn grain by hydrogenated oil in grazing dairy cows in early lactation

Thirty-six grazing dairy cows were used to determine milk production and composition, and dry matter and energy intake when corn grain was partially replaced by hydrogenated oil in the concentrate. Four additional cows, each fitted with a ruminal cannula, were used in a crossover design to evaluate effects of supplemental fat on rumen environment and pasture digestion. All cows grazed mixed pastures with an herbage allowance of 30 kg dry matter/cow per day. The control group was fed a concentrate containing corn grain (4.49 kg dry matter/cow per day) and fishmeal (0.37 kg dry matter/cow per day), whereas the other group (fat) received a concentrate containing corn grain (2.87 kg dry matter/cow per day), fishmeal (0.37 kg dry matter/cow per day) and fat (0.7 kg dry matter/cow per day). The fat was obtained by hydrogenation of vegetable oils (melting point 58 to 60 degrees C, 30.3% C16:0, 34.9% C18:0, 21.8% C18:1, 3.3% C18:2). Supplemental fat increased milk production (control = 23.7 vs. fat = 25.0 kg/cow per day), fat-corrected milk (control = 22.5 vs. fat = 24.5 kg/cow per day), milk fat content (control = 3.64% vs. fat = 3.86%) and yields of milk fat (control = 0.86 vs. fat = 0.97 kg/cow per day) and protein (control = 0.74 vs. fat = 0.78 kg/cow per day). Milk percentages of protein, lactose, casein, cholesterol, and urea nitrogen were not affected. Pasture DMI and total DMI of pasture and concentrate and estimated energy intake were unchanged. No differences in loss of body weight or body condition score were detected. Plasma concentrations of nonesterified fatty acids, somatotropin, insulin, and insulin-like growth factor were not affected by supplemental fat. Concentrations of plasma triglyceride and total cholesterol were increased by supplemented fat, and no changes in plasma glucose and urea nitrogen were observed. The acetate-to-propionate ratio was higher in rumen fluid of cows that consumed fat (fat = 3.39 vs. control = 3.27). In situ pasture NDF degradation was not affected. The partial replacement of corn grain with fat improved the productive performance of early-lactation cows grazing spring pastures. No negative effects of supplemental fat on ruminal fiber digestion were detected.     

Effect of pregrazing herbage mass and pasture allowance on the lactation performance of Holstein-Friesian dairy cows

The objective of this study was to investigate the effect of pregrazing herbage mass (HM) and pasture allowance (PA) on the grazing management and lactation performance of spring-calving dairy cows. Sixty-eight Holstein-Friesian dairy cows (mean calving date, February 6) were randomly assigned across 4 treatments (n = 17) in a 2 × 2 factorial arrangement. The 4 treatments consisted of 2 pregrazing HM (>4 cm) and 2 PA (>4 cm): 1,700 kg of dry matter (DM)/ha (medium, M) or 2,200 kg of DM/ha (high, H), and 16 or 20 kg of pasture DM/cow per day. The experimental period lasted 30 wk. The experimental area was divided into 4 farmlets, with 1 farmlet per treatment. Mean HM throughout the experimental period was 1,767 kg of DM/ha (M HM) compared with 2,358 kg of DM/ha (H HM). Offering an M HM sward resulted in significantly greater milk protein yield (+31.7 g/d) and lower mean body weight (−12.8 kg). The body condition score change was significantly smaller (−0.21) with the M HM treatments compared with the H HM treatment (−0.34). Milk solids output per hectare was 6% greater on the M HM treatments compared with the H HM treatments. Increasing PA significantly increased milk (+0.9 kg/d), solids-corrected milk (+0.7 kg/d), protein (+43.9 g/d), and lactose (+52.7 g/d) yields. Mean body weight was also significantly greater for cows offered 20 kg of PA (+11.4 kg/cow). It was concluded that in rotational grazing systems, adapting the concept of grazing M HM pastures (1,700 kg of DM/ha) will result in increased sward quality and increased milk solids output per hectare. At medium levels of pregrazing HM, offering animals 20 kg of DM PA will result in increased milk yield per cow.     

Effects of corn silage processing and amino acid supplementation on the performance of lactating dairy cows

This experiment was conducted to determine the effect of crop processing and amino acid supplementation on dairy cow performance. Corn silage processed (PCS) or unprocessed (UCS) was used as the main forage (45% of dry matter, DM) in a total mixed ration (TMR). Each TMR was either supplemented (AA) or not (AAO) with ruminally protected amino acids (lysine, 3 g/d and methionine, 14 g/d). Thirty-two (551 kg) Holstein cows were randomly assigned to four treatments: PCS-AA, PCS-AA0, UCS-AA, and UCS-AA0 in a 2 x 2 factorial structure. Between wk 7 and 17 of lactation, cows were fed ad libitum TMR comprising 45% of corn silage plus 1 kg of grass hay once a day. The UCS presented better fermentation characteristics than PCS. Dry matter intake (DMI) of the TMR was not affected by treatment and averaged 22.7 kg/d. Energy-corrected milk (ECM) production was 9% higher with UCS than with PCS (33.1 vs. 30.1 kg/d). Milk efficiency was therefore 6% higher with UCS than with PCS (1.43 vs. 1.35 kg ECM/kg of DMI). The concentration of major milk constituents (fat, protein, lactose, urea) was not affected by treatments. Apparent digestibility of DM, organic matter, N, starch, acid detergent fiber, and neutral detergent fiber were similar among treatments. The effective ruminal degradability of DM, starch, and protein, however, was greater with PCS than with UCS. Amino acid supplementation had no effect on milk production nor on milk constituents, whether it was used with processed corn silage or with unprocessed corn silage. These data indicate that feeding UCS resulted in a greater milk production compared with PCS. The numerically higher DMI, a potentially greater intestinal digestion of starch or the better conservation of UCS could have contributed to the greater milk production.     

Effects of feeding supplemental organic iron to late gestation and early lactation dairy cows

The objectives of this experiment were to determine the Fe status of cows in late gestation and early lactation and determine whether measures of Fe status and milk production were affected by feeding supplemental organic Fe. Starting 60 d before anticipated calving, cows and heifers were fed diets with 0 or 30 mg/kg of supplemental Fe (Availa-Fe, Zinpro Corp., Eden Prairie, MN). All animals changed to prefresh diets at 14 d before anticipated calving and then to lactation diets following calving; the Fe supplementation rates (0 or 30 mg/kg) remained constant. The experiment ended at 63 d in milk. Hematocrit, hemoglobin, serum Fe, unsaturated Fe binding capacity, and percentage Fe binding saturation were measured at the start of the experiment, 7 d before calving, 7 d after calving, and at 60 d in milk. Treatment did not affect any measure of Fe status and values did not change greatly over time. Milk production (averaged 41 kg/d), milk composition, and dry matter intake during early lactation (averaged 20.4 kg/d) were not affected by treatment. The somatic cell count of milk was reduced when cows were fed supplemental Fe (114,000 vs. 94,000 cells/mL). The limited response to supplemental Fe may have been because basal diets were adequate in Fe (ranged from 282 to 336 mg of Fe/kg of DM) even though most of the basal dietary Fe was provided by forages, which are generally considered poor sources of available Fe.     

Effects of feeding time on nitrogen capture by lactating dairy cows grazing rye pasture

The objective of this experiment was to determine whether varying times at which a partial mixed ration was fed, either before or after grazing, affected N utilization from rye pasture and thus affected milk yield and components. Sixteen Holstein cows were fed a partial mixed ration (PMR) either at 0700, 0830, or 1100 h. Cows were milked at 0900 h and turned out to graze at 0930 h. Treatments represented feeding times 2.5 h and 1 h before grazing and immediately after grazing. The study was conducted as a 3 x 3 Latin square with three 17-d periods. There were no significant differences among treatments for pasture intake or yield of milk or milk components. Milk yield, fat %, and protein % were 29.4, 29.6, and 29.3 kg, 3.5, 3.5, and 3.4%, and 3.4, 3.5, and 3.4% for treatments, respectively. The milk urea levels were 15.6, 15.1, and 15.5 mg/dl, and were not different among treatments. Blood samples were collected on the last day of each period at 0645, 0845, 1045, 1200, and 1400 h. Blood urea nitrogen (BUN) was measured as an indicator of ruminal N capture. Concentrations were not significantly different among diets before grazing; however, they were significantly different among all treatments approximately 1 h after cows were removed from pasture. Cows fed at 0700 h, 2 h before grazing, maintained lower BUN levels across the 7 h during which the blood samples were collected. Cows that ate the PMR immediately after grazing maintained the highest BUN. Feeding a PMR to cows that graze at different times before and after grazing affected the capture of ruminal N, as indicated by differences in the levels of BUN, but there was no effect on yield of milk or milk components.     

Effects of supplemental dietary biotin on performance of Holstein cows during early lactation

This study determined the effects of supplemental dietary biotin (0, 10, or 20 mg/d) on performance of Holstein cows (n = 45; 18 primiparous and 27 multiparous). Treatments started at 14 d prepartum and continued until 100 d in milk (DIM). Blood samples were taken at 14 d prepartum, and blood and milk samples were taken at calving, and 30, 60, and 100 DIM. Dry matter intake during lactation was not different across treatments (19.7 kg/d). Milk production linearly increased with biotin supplementation (36.9, 37.8, and 39.7 kg/d for 0, 10, and 20 mg/d of supplemental biotin, respectively). Biotin supplementation did not affect milk fat and true protein percentages or fat yield but linearly increased true protein yield. Supplemental biotin increased concentrations of biotin in plasma and milk at all time points. Concentrations of biotin in plasma and milk (colostrum) at calving were higher than at other time points for cows fed supplemental biotin. In an ancillary experiment, plasma biotin concentrations were not as high when cows were fed 20 mg/d of supplemental biotin for 14 d during the middle of their dry period as when cows were fed 20 mg/d of biotin for the last 14 d of gestation. This suggests that events associated with parturition altered plasma biotin concentrations. Plasma concentrations of glucose, insulin, nonesterified fatty acids, and molar proportions of ruminal volatile fatty acids were not affected by biotin supplementation. Biotin supplementation had no effect on change in body weight or condition score. Supplemental biotin linearly increased milk and protein yields, however, the mode of action that caused these increases was not determined.     

Effects of supplementation and stage of lactation on performance of grazing dairy ewes

The majority of dairy sheep in the world are fed pasture and supplemental grain during lactation; however, no trials have reported the effects of supplementation of dairy ewes grazing improved pastures in North America. In trial 1, 56 three-year-old grazing dairy ewes in early [21 ± 10 d in milk (DIM)] or late (136 ± 9 DIM) lactation were fed 0 or 0.82 kg of dry matter/d per ewe of supplement (16.5% crude protein mixture of corn and a soybean meal-based high-protein pellet) in a 2 × 2 factorial arrangement of treatments. There were no significant interactions between stage of lactation and supplementation treatments. Average test-day milk production was higher in early-lactation ewes than in late-lactation ewes (1.74 vs. 1.21 kg/d, respectively). Although test-day milk protein percentage was higher in late-lactation ewes than in early-lactation ewes (5.02 vs. 4.86%, respectively), there was no difference in milk fat percentage between stages of lactation. Supplemented ewes had higher milk production (1.59 vs. 1.36 kg/d, respectively), lower milk fat percentage (5.75 vs. 6.00%, respectively), and lower milk protein percentage (4.84 vs. 5.04%, respectively) than unsupplemented ewes. Milk urea N levels were similar between the 2 stages of lactation and between the 2 supplementation treatments and were above recommended levels for dairy sheep, indicating an excess intake or inefficient utilization of protein for both supplementation treatments. In trial 2, 96 two-, three-, and four-year-old grazing dairy ewes in midlactation (112 ± 21 DIM) were randomly assigned to 4 treatments of 0, 0.41, 0.82, or 1.24 kg of dry matter/d per ewe of whole corn. Average test-day milk production increased linearly and milk fat percentage decreased quadratically with increasing amounts of corn supplementation. Milk protein yield increased linearly, and milk urea N levels decreased quadratically with increasing amounts of corn supplementation, suggesting an improvement in the utilization of pasture protein with increasing dietary energy intake.     

Effects of NutriDense and waxy corn hybrids on the rumen fermentation, digestibility and lactational performance of dairy cows

The objectives of this study were to determine the effects of NutriDense and waxy corn hybrids as silage and grain sources on milk yield, milk composition, digestibility of dietary components, and rumen characteristics. Six multiparous (intact) and six primiparous (ruminally cannulated) Holstein cows were assigned at 72 to 90 d of lactation to a 3 x 6 Latin rectangle design experiment to treatment of: 1) control diet, 2) NutriDense corn diet, and 3) waxy corn diet. Diets consisted of 10.9% alfalfa silage, 32.8% corn silage, 27.9% cracked corn grain, and 28.4% other ingredients (DM basis). Milk, FCM, and milk fat and protein yields were higher for cows fed the waxy diet than those fed the control diet. Milk protein percentage tended to be higher for cows fed the control and waxy diets than those fed the NutriDense diet. Dry matter intake tended to be higher for cows fed the waxy diet than the NutriDense diet. Apparent DM, OM, CP, ADF, NDF, and gross energy digestibilities were similar among dietary treatments, while apparent starch digestibility was higher for the waxy corn than for the NutriDense corn. Rumen NH3-N concentration was higher for cows fed the NutriDense diet than for those fed the control and waxy diets. The proportion of ruminal propionate was higher for the waxy diet than the control diet. NutriDense and waxy corn hybrids can be effective substitutes for conventional yellow dent corn hybrids in lactating dairy cow rations.     

Effects of peripartal yeast culture supplementation on lactation performance,blood biomarkers,rumen fermentation,and rumen bacteria species in dairy cows

Feeding yeast culture fermentation products has been associated with improved feed intake and milk yield in transition dairy cows. These improvements in performance have been further described in terms of rumen characteristics, metabolic profile, and immune response. The objective of this study was to evaluate the effects of a commercial yeast culture product (YC; Culture Classic HD, Phibro Animal Health) on performance, blood biomarkers, rumen fermentation, and rumen bacterial population in dairy cows from −30 to 50 d in milk (DIM). Forty Holstein dairy cows were enrolled in a randomized complete block design from −30 to 50 DIM and blocked according to expected calving day, parity, previous milk yield, and genetic merit. At −30 DIM, cows were assigned to either a basal diet plus 114 g/d of ground corn (control; n = 20) or a basal diet plus 100 g/d of ground corn and 14 g/d of YC (n = 20), fed as a top-dress. Cows received the same close-up diet from 30 d prepartum until calving [1.39 Mcal/kg of dry matter (DM) and 12.3% crude protein (CP)] and lactation diet from calving to 50 DIM (1.60 Mcal/kg of DM and 15.6% CP). Blood samples and rumen fluid were collected at various time points from −30 to 50 d relative to calving. Cows fed YC compared with control showed a trend for increased energy-corrected milk (+3.2 kg/d). Lower somatic cell counts were observed in YC cows than in control. We detected a treatment × time interaction in nonesterified fatty acids (NEFA) that could be attributed to a trend for greater NEFA in YC cows than control at 7 DIM, followed by lower NEFA in YC cows than control at 14 and 30 DIM. In the rumen, YC contributed to mild changes in rumen fermentation, mainly increasing postpartal valerate while decreasing prepartal isovalerate. This was accompanied by alterations in rumen microbiota, including a greater abundance of cellulolytic (Fibrobacter succinogenes) and lactate-utilizing bacteria (Megasphaera elsdenii). These results describe the potential benefits of supplementing yeast culture during the late pregnancy through early lactation, at least in terms of rumen environment and performance.     

Chromium supplementation and substitution of barley grain with corn: Effects on performance and lactation in periparturient dairy cows

Thirty-two multiparous Holstein cows were used to investigate the effects of chromium-l-methionine (Cr-Met) supplementation and dietary grain source on performance and lactation during the periparturient period. Cows were fed a total mixed ration consisting of either a barley-based diet (BBD) or a corn-based diet (CBD) from 21 d before anticipated calving through 28 d after calving. The Cr-Met was supplemented at dosages of 0 or 0.08 mg of Cr/kg of metabolic body weight. The study was designed as a randomized complete block design with 2 (Cr-Met levels) × 2 (grain sources) factorial arrangement. There was no Cr effect on prepartum dry matter intake (DMI) or postpartum DMI, body weight (BW), net energy balance, and whole tract apparent digestibility of nutrients. Prepartum DMI as a percentage of BW tended to increase with Cr-Met. Supplemental Cr-Met tended to increase milk yield whereas milk protein percentage decreased. Pre- and postpartum DMI, BW, net energy balance, milk yield, and milk composition were not affected by substituting ground barley with ground corn. The addition of Cr-Met increased prepartum DMI and tended to increase postpartum DMI of the BBD but not the CBD. The change in prepartum DMI was smaller when the BBD was supplemented with Cr-Met but remained unchanged when the CBD was supplemented with Cr-Met. Yields of crude protein and total solids in milk and prepartum digestibility of DM and organic matter tended to increase when Cr-Met was added to the BBD but remained unchanged when added to the CBD. Periparturient cows failed to respond to the grain source of the diet, whereas they showed greater response in milk yield to diets supplemented with Cr-Met. In conclusion, the present results demonstrate that the beneficial effect of Cr-Met supplementation during the periparturient period to improve feed intake may depend on the grain source of the diet.     

Effects of yeast culture supplementation on lactation performance and rumen fermentation profile and microbial abundance in mid-lactation Holstein dairy cows

The continuous trend for a narrowing margin between feed cost and milk prices across dairy farms in the United States highlights the need to improve and maintain feed efficiency. Yeast culture products are alternative supplements that have been evaluated in terms of milk performance and feed efficiency; however, less is known about their potential effects on altering rumen microbial populations and consequently rumen fermentation. Therefore, the objective of this study was to evaluate the effect of yeast culture supplementation on lactation performance, rumen fermentation profile, and abundance of major species of ruminal bacteria in lactating dairy cows. Forty mid-lactation Holstein dairy cows (121 ± 43 days in milk; mean ± standard deviation; 32 multiparous and 8 primiparous) were used in a randomized complete block design with a 7-d adaptation period followed by a 60-d treatment period. Cows were blocked by parity, days in milk, and previous lactation milk yield and assigned to a basal total mixed ration (TMR; 1.6 Mcal/kg of dry matter, 14.6% crude protein, 21.5% starch, and 38.4% neutral detergent fiber) plus 114 g/d of ground corn (CON; n = 20) or basal TMR plus 100 g/d of ground corn and 14 g/d of yeast culture (YC; n = 20; Culture Classic HD, Cellerate Yeast Solutions, Phibro Animal Health Corp.). Treatments were top-dressed over the TMR once a day. Cows were individually fed 1 × /d throughout the trial. Blood and rumen fluid samples were collected in a subset of cows (n = 10/treatment) at 0, 30, and 60 d of the treatment period. Rumen fluid sampled via esophageal tubing was analyzed for ammonia-N, volatile fatty acids (VFA), and ruminal bacteria populations via quantitative PCR amplification of 16S ribosomal DNA genes. Milk yield was not affected by treatment effects. Energy balance was lower in YC cows than CON, which was partially explain by the trend for lower dry matter intake as % body weight in YC cows than CON. Cows fed YC had greater overall ruminal pH and greater total VFA (mM) at 60 d of treatment period. There was a contrasting greater molar proportion of isovalerate and lower acetate proportion in YC-fed cows compared with CON cows. Although the ruminal abundance of specific fiber-digesting bacteria, including Eubacterium ruminantium and Ruminococcus flavefaciens, was increased in YC cows, others such as Fibrobacter succinogenes were decreased. The abundance of amylolytic bacteria such as Ruminobacter amylophilus and Succinimonas amylolytica were decreased in YC cows than CON. Our results indicate that the yeast culture supplementation seems to promote some specific fiber-digesting bacteria while decreasing amylolytic bacteria, which might have partially promoted more neutral rumen pH, greater total VFA, and isovalerate.     

Influence of corn silage particle length on the performance of lactating dairy cows fed supplemental tallow

The objective of this study was to determine if the length of chop of processed corn silage influences the impact of supplemental fat on rumen fermentation and performance of dairy cows. We hypothesized that increasing forage particle length may alleviate the interference of fat on rumen fermentation. Sixteen Holstein cows averaging 120 d in milk were used in a replicated 4 x 4 Latin square design with 21-d periods. Treatments were arranged as a 2 x 2 factorial with 0 or 2% tallow (dry matter basis), and corn silage harvested at either 19 or 32 mm theoretical length of cut. The forage:concentrate ratio was 50:50, and diets were formulated to contain 18% crude protein and 32% neutral detergent fiber (dry matter basis). Cows were allowed ad libitum consumption of diets that were fed twice daily as a total mixed ration. Fat supplemented cows had lower dry matter intake and produced less milk fat relative to nonsupplemented cows. No effect of corn silage particle length was observed for dry matter intake and milk fat production. Proportion of trans-10 C18:1 and of trans-10, cis-12 conjugated linoleic acid was highest in milk fat of cows fed 2% supplemental tallow. Rumen pH was not affected by feeding tallow, and tended to be highest for cows eating the 32-mm theoretical length of chop corn silage diets. No effect of treatments was observed for rumen acetate-to-propionate ratio or rumen ammonia concentration. In this study, tallow supplementation had a negative impact on performance of dairy cows regardless of the corn silage particle length. Feeding tallow increased formation of trans-fatty acids in the rumen in the absence of significant changes in the rumen environment.