Performance of dairy cows fed silage and grain produced from second-generation insect-protected (Bacillus thuringiensis) corn (MON 89034), compared with parental line corn or reference corn

Corn grain and corn silage are major feed components in lactating dairy cow rations. Bacillus thuringiensis (B.t.) is a naturally occurring soil bacterium that produces a protein that is toxic to lepidopteran insects that may damage plant tissues and reduce corn quality and yields. During each of the four 28-d periods, cows were offered 1 of 4 rations in which the corn grain and silage originated from different corn hybrids: a nontransgenic corn control (from hybrid DKC63-78; Monsanto Co., St. Louis, MO), a B.t. test substance corn (MON 89034 in hybrid DKC63-78; Monsanto Co.), and 2 commercial nontransgenic reference (Ref) hybrids: DKC61-42 (Ref 1) and DKC62-30 (Ref 2; Monsanto Co.). Sixteen multiparous Holstein cows averaging 110 ± 21 d in milk and weighing 684 ± 62.3 kg were blocked by days in milk and milk yield and randomly assigned to one of four 4 × 4 Latin squares. Diets were formulated to contain 36.4% corn silage and 16.3% corn grain. Dry matter intake was greater for cows consuming B.t. corn (26.6 ± 0.59 kg/d) compared with the control, Ref 1, and Ref 2 corn diets (25.4, 25.0, and 25.6 ± 0.59 kg/d, respectively). Milk yield, fat yield, and percentage of fat (36.8 ± 0.98 kg/d, 1.22 ± 0.05 kg/d, and 3.3 ± 0.10%), milk protein yield and percentage of protein (1.11 ± 0.03 kg/d and 3.01 ± 0.05%), milk urea nitrogen concentration (14.01 ± 0.49 mg/dL), and 3.5% fat-corrected milk yield (35.7 ± 1.07 kg/d) were not different across treatments. The results from this study show that lactating dairy cows that consume B.t. corn (MON 89034) do not differ from lactating dairy cows that consume nontransgenic corn in milk yield, 3.5% fat-corrected milk per unit of dry matter intake, or milk components.     

Direct-fed microbial supplementation on ruminal digestion, health, and performance of pre- and postpartum dairy cattle

Effects of supplementing direct-fed microbial agents (DFM) to dairy cows during the transition period were evaluated. Forty-four Holstein cows were fed close-up and lactating diets that did or did not contain 2 g of DFM/cow per d. Direct-fed microbial supplementation contained approximately 5 × 10⁹ cfu of yeast and 5 × 10⁹ cfu of bacteria (2 specific Enterococcus faecium strains) incorporated into a cornmeal carrier. Supplemented cows were fed the DFM 21 d prior to expected calving date through 10 wk postpartum. Cows supplemented with DFM had higher estimated ruminally available dry matter (DM) for both corn silage and haylage than did control cows. Supplemented cows consumed more DM during both the pre- and postpartum periods. In addition, those supplemented with DFM produced 2.3 kg more milk/cow per d than did nonsupplemented cows. There was no difference in 3.5% fat-corrected milk. Milk fat percentage was lower, but not depressed (4.76 vs. 4.44%) for cows receiving DFM. There were no differences in milk fat yield or milk protein percentage and yield. Cows consuming DFM had higher blood glucose postpartum, as well as lower β-hydroxybutyrate levels both prepartum and on d 1 postpartum. Plasma nonesterified fatty acid concentration was not statistically affected by DFM, but was numerically lower prepartum and higher postpartum for supplemented cows. This study demonstrated that targeted DFM supplementation enhanced ruminal digestion of forage DM. Early lactation cows receiving supplemental DFM produced more milk and consumed more DM during the pre- and postpartum periods. Cows consuming DFM, however, experienced a lower, but not depressed, fat percentage compared with nonsupplemented cows.     

Capturing urine while maintaining pasture intake, milk production, and animal welfare of dairy cows in early and late lactation

Capturing urine and spreading it evenly across a paddock reduces the risk of nitrogen loss to the environment. This study investigated the effect of 16 h/d removal from pasture on the capture of urination events, milk production, pasture intake, and animal welfare from cows grazing fresh pasture in early and late lactation. Forty-eight Holstein-Friesian cows in early [470 ± 47 kg of body weight (BW); 35 ± 9 days in milk] and late (498 ± 43 kg of BW; 225 ± 23 days in milk) lactation were allocated to 3 treatment groups. Cows had access to pasture for either 4 h after each milking (2 × 4), for 8 h between morning and afternoon milkings (1 × 8), or for 24 h, excluding milking times (control). When not grazing, the 2 × 4 and 1 × 8 groups were confined to a plastic-lined loafing area with a woodchip surface. In early lactation, the proportion of urinations on pasture and laneways was reduced from 89% (control) to 51% (1 × 8) and 54% (2 × 4) of total urinations. The 1 × 8 cows ate less pasture [10.9 kg of dry matter (DM)/cow per day] than the control (13.6 kg of DM/cow per day) and 2 × 4 (13.0 kg of DM/cow per day) cows, which did not differ from each other. The 1 × 8 and 2 × 4 cows produced less milk (21 and 22 kg of milk/cow per day, respectively) compared with control cows (24 kg of milk/cow per day). There were no differences in BW or body condition score (BCS) change across treatment groups, with all groups gaining BW and BCS during the experimental period. In late lactation, there was no difference in pasture intake (mean = 8.8 kg of DM/cow per day), milk production (mean = 10 kg of milk/cow per day), and BW or BCS change (mean = 3.7 kg and −0.2 U/cow per week, respectively) between treatment groups. As in early lactation, urinations on pasture and laneways were reduced from 85% (control) to 56% (1 × 8) and 50% (2 × 4) of total urinations. These findings highlight an opportunity to maintain performance and welfare of grazing cows in early and late lactation while capturing additional urine. This can subsequently be spread evenly across pasture to minimize nitrogen loss to the environment.     

Optimizing the level of wet corn gluten feed in the diet of lactating dairy cows

Twenty-four multiparous Holstein cows averaging 566 +/- 43 kg of body weight and 83 +/- 49 d in lactation were assigned to treatments stratified by age, days in milk, and milk yield to evaluate the effects of feeding increasing levels of wet corn gluten feed (WCGF) on lactational performance and milk composition. Complete diets containing 0, 15, 30, or 45% of the total ration dry matter (DM) as WCGF were formulated to be 17.2% crude protein and 1.72 Mcal of NE(L) per kilogram of DM, and fed twice daily to individual cows in Calan gates for 15 wk. All diets had a positive metabolizable protein balance. WCGF did not alter DM intake, but feed intake variance tended to be more consistent among cows fed 15 and 30% WCGF (DM basis). Weight gain was numerically greatest for those cows receiving 45% WCGF. Efficiency of energy and protein utilization was not different among treatments. Milk components of fat, protein, and casein were not different among treatments. Milk urea nitrogen was greater for cows on WCGF. Serum urea nitrogen was greatest in cows fed diets containing 15 and 45% WCGF. Serum insulin was lowest in the groups receiving 30 and 45% WCGF, but serum glucose and total protein were unaffected. The concentration of the ruminal volatile fatty acid, valerate, was greater in cows on the WCGF diet and highest in cows fed 30% WCGF. Ruminal ammonia was greatest in cows receiving 30% WCGF. It was estimated that 18.6% of the dietary DM fed as WCGF as a replacement for both portions of the concentrate and the forage in similar diets would have maximized milk yield without negatively affecting milk composition or feed efficiency.     

Intake and milk production of cows fed diets that differed in dietary neutral detergent fiber and neutral detergent fiber digestibility

The objectives of this study were to determine how feeding diets that differed in dietary neutral detergent fiber (NDF) concentration and in vitro NDF digestibility affects dry matter (DM) intake, ruminal fermentation, and milk production in early lactation dairy cows. Twelve rumen-cannulated, multiparous Holstein cows averaging 38 ± 15 d (±standard deviation) in milk, and producing 40 ± 9 kg of milk daily, were used in a replicated 4 × 4 Latin square design with 28-d periods. Treatment diets were arranged in a 2 × 2 factorial with 28 or 32% dietary NDF (DM basis) and 2 levels of straw NDF digestibility: 1) LD, untreated wheat straw (77% NDF, 41% NDF digestibility) or 2) HD, anhydrous NH₃-treated wheat straw (76% NDF, 62% NDF digestibility). All 4 diets consisted of wheat straw, alfalfa silage, corn silage, and a concentrate mix of cracked corn grain, corn gluten meal, 48% soybean meal, and vitamins and minerals. Wheat straw comprised 8.5% DM of the 28% NDF diets and 16% DM of the 32% NDF diets. Cows fed 28% NDF and HD diets produced more milk, fat, and protein than those consuming 32% NDF or LD diets. Dry matter intake was greater for cows consuming 28% NDF diets, but intakes of DM and total NDF were not affected by in vitro NDF digestibility. Intake of digestible NDF was greater for cows consuming HD diets. Ruminal fermentation was not affected by feeding diets that differed in NDF digestibility. Ruminal NDF passage rate was slower for cows fed HD than LD. No interactions of dietary NDF concentration and in vitro NDF digestibility were observed for any parameter measured. Regardless of dietary NDF concentration, increased in vitro NDF digestibility improved intake and production in early lactation dairy cows.     

Effect of milking frequency and feeding level before and after dry off on dairy cattle behavior and udder characteristics

The effects of 2 common dry-off management procedures, feed restriction [8 vs. 16 kg of dry matter (DM)/d] and reduced milking frequency (once, 1× vs. twice, 2×/d), on the behavior and udder characteristics of dairy cattle were assessed in late lactation and the early dry period. Milking cows 1× instead of 2× in the week before dry off reduced milk yield (7.0 vs. 8.9 ± 0.95 kg/d for 1× and 2×, respectively), but had little effect on behavior before or after cessation of milking. In comparison, feed restriction reduced milk yield (6.9 vs. 9.1 ± 0.95 kg/d for 8 and 16 kg of DM/d, respectively), udder firmness after dry off (7.3 vs. 8.0 ± 0.24 g force for 8 and 16 kg of DM/d, respectively), milk leakage (2 d after dry off, 14% of cows offered 8 kg of DM/d were leaking milk compared with 42% cows offered 16 kg of DM/d), and the likelihood of Streptococcus uberis intramammary infection (nonclinical mastitis; 12.5 vs. 62.5% of groups with at least 1 cow with a new intramammary infection for 8 and 16 kg of DM/d, respectively). Despite these benefits, cows offered only 8 kg of DM/d spent less time eating (7.3 vs. 8.3 ± 0.28 h/d for 8 and 16 kg DM/d, respectively), more time lying (8.8 vs. 7.3 ± 0.24 h/d), and vocalized more before dry off than cows offered 16 kg of DM/d (0.8 vs. 0.2 ± 0.15 calls/min for 8 and 16 kg of DM/d, respectively). These behavioral changes indicate that this level of feed restriction may cause hunger. Information is needed about alternative dry-off procedures that maintain the health benefits and comfort associated with lower milk yield before dry off but prevent hunger, such as feeding low quality diets ad libitum.     

Holstein-Friesian strain and feed effects on milk production, body weight, and body condition score profiles in grazing dairy cows

Data from 113 lactations across 76 cows between the years 2002 to 2004 were used to determine the effect of strain of Holstein-Friesian (HF) dairy cow and concentrate supplementation on milk production, body weight (BW), and body condition score (BCS; 1 to 5 scale) lactation profiles. New Zealand (NZ) and North American (NA) HF cows were randomly allocated to 1 of 3 levels of concentrate supplementation [0, 3, or 6 kg of dry matter (DM)/cow per d] on a basal pasture diet. The Wilmink exponential model was fitted within lactation (Y_DIM = a + b e(^{−0.05 × DIM)} + c × DIM). The median variation explained by the function for milk yield was 86%, between 62 and 69% for milk composition, and 80 and 70% for BW and BCS, respectively. North American cows and cows supplemented with concentrates had greater peak and 270-d milk yield. Concentrate supplementation tended to accelerate the rate of incline to peak milk yield, but persistency of lactation was not affected by either strain of HF or concentrate supplementation. No significant strain by diet interaction was found for parameters reported. New Zealand cows reached nadir BCS 14 d earlier and lost less BW (22 kg) postcalving than NA cows. Concentrate supplementation reduced the postpartum interval to nadir BW and BCS, and incrementally increased nadir BCS. New Zealand cows gained significantly more BCS (i.e., 0.9 × 10⁻³ units/d more) postnadir than NA cows, and the rate of BCS replenishment increased linearly with concentrate supplementation from 0.5 × 10⁻³ at 0 kg of DM/d to 0.8 × 10⁻³ and 1.6 × 10⁻³ units/d at 3 and 6 kg of DM/d concentrates, respectively. Although there was no significant strain by diet interaction for parameters reported, there was a tendency for a strain by diet interaction in 270-d BCS, suggesting that the effect of concentrate supplementation on BCS gain was, at least partly, strain dependent.     

Reciprocal combinations of barley and corn grains in oil-supplemented diets: Feeding behavior and milk yield of lactating cows

The effect of barley-based (BBD) or corn-based diets (CBD), or their equal blend (BCBD) on dry matter (DM) intake, feeding and chewing behavior, and production performance of lactating dairy cows was evaluated. Nine multiparous Holstein cows (75.6 ± 11.0 d in milk) were used in a triplicate 3 × 3 Latin square design with 21-d periods. Forage-to-concentrate ratio (40:60), forage neutral detergent fiber (20% of DM), total neutral detergent fiber (>29% of DM), and geometric mean particle size (4.3 mm) were similar among treatments. Meal patterns, including meal size and intermeal interval, were not affected by the dietary treatments and DM intake (25.6 kg/d) was not different among treatments. Ether extract intake increased linearly with increasing amount of the corn grain in the diets. Due to similar feed intake, actual milk (48.6 kg/d), 4% fat-corrected milk (36.8 kg/d), and fat- and protein-corrected milk (38.1 kg/d) yields were not affected by treatments. Average milk protein percentage and yield were 2.83% and 1.37 kg/d, respectively, and were not different across treatments. Milk fat percentage increased linearly with increasing amount of corn grain in the diets and was greater in CBD relative to BCBD but not BBD (2.31, 2.28, and 2.57%, for BBD, BCBD, and CBD, respectively). However, milk fat yield tended to show a linear increase as the amount of corn grain included in the diets increased. Results indicated that changing diet fermentability by replacing barley grain for corn grain in oil-supplemented diets did not influence feeding patterns and thereby no changes in feed intake and milk yield occurred.     

Effect of lactation number, year, and season of initiation of lactation on milk yield of cows hormonally induced into lactation and treated with recombinant bovine somatotropin

Records representing data from 1,500 barren Holstein cows over an 8-yr period from a large commercial dairy farm in northern Mexico were analyzed to determine the effects of lactation number and season and year of initiation of lactation on milk production of cows induced hormonally into lactation and treated with recombinant bovine somatotropin (rbST) throughout lactation. Peak and 305-d milk yields were also assessed as predictors of total milk yield in cows induced into lactation. A significant quadratic relationship was found between 305-d milk yield and number of lactation [7,607 ± 145 and 9,548 ± 181 kg for first- and ≥6-lactation cows, respectively; mean ± standard error of the mean (SEM)] with the highest production occurring in the fifth lactation. Total milk yields of cows with ≤2 lactations were approximately 4,500 kg less than milk yields of adult cows (the overall average ± standard milk yield was 13,544 ± 5,491 kg per lactation and the average lactation length was 454 ± 154 d). Moreover, 305-d milk production was depressed in cows induced into lactation in spring (8,804 ± 153 kg; mean ± SEM) and summer (8,724 ± 163 kg) than in fall (9,079 ± 151 kg) and winter (9,085 ± 143 kg). Partial regression coefficients for 305-d milk yield and peak milk yield indicated an increment of 157 kg of milk per lactation per 1-kg increase in peak milk yield (r² = 0.69). Neither peak milk yield (r² = 0.18) nor 305-d milk yield (r² = 0.29) was accurate for predicting total milk yield per lactation. Year, parity, and season effects had significant influence on milk yield of cows induced into lactation and treated with rbST throughout lactation, and peak milk yield can assist in the prediction of 305-d milk yield but not total milk yield. This study also showed that hormonal induction of lactation in barren high-yielding cows is a reliable, practical, and affordable technique in countries where rbST treatment and prolonged steroid administration of dairy cows are legally permitted.     

Administration of bovine somatotropin in early lactation: a meta-analysis of production responses by multiparous Holstein cows

A meta-analysis was conducted to assess production responses before 90 d in milk (DIM) when bovine somatotropin (bST) administration was initiated between 5 and 35 DIM. The database was developed from 13 studies of multiparous cows that were published between 1985 and 2006 and from an unpublished study that complied with the study selection criteria. The database included results from 842 cows and provided 50 treatment means for the effect of bST on 3.5% fat-corrected milk (FCM) in early lactation. Effects of bST were investigated using mixed model procedures that included fixed (intercept and slope) and random (intercept and slope) effects for independent variables. Yields of milk (38.6 ± 1.3 kg/d) and FCM (37.6 ± 1.6 kg/d) by control cows before 90 DIM were increased by 2.6 ± 0.8 and 3.2 ± 0.6 kg/d by bST administration. Fat content in milk from bST-treated cows was 0.31 ± 0.10 percentage units greater than that from control cows (3.46 ± 0.13%) but milk protein content (2.95 ± 0.03%) was not altered by bST. Milk fat (1.39 ± 0.10 kg/d) and protein (1.15 ± 0.04 kg/d) yields by controls were increased 0.16 ± 0.03 and 0.07 ± 0.03 kg/d by bST, respectively. Dry matter intake and body weight loss were not altered by bST before 90 DIM, but duration of negative energy balance was prolonged and overall energy balance during this interval reduced when cows were treated with bST. Results are consistent with the premise that bST-treated cows partition nutrients and energy toward milk synthesis for a longer duration and thus likely need a longer interval to replenish their body reserves than cows not treated with bST. Production responses to bST were not altered when cows consumed typical early-lactation diets supplemented with fat except that supplemental fat tended to decrease the magnitude of the effect of bST on milk fat content and decreased the effect of bST on fat and protein yield. Yield of FCM increased curvilinearly with the amount of bST administered. Results indicate that initiation of bST administration to cows before 35 DIM increased FCM yield but the response was at the low end of that typically observed when bST administration is initiated in wk 9 of lactation.     

Effects of feeding Fermenten on ruminal fermentation in lactating Holstein cows fed two dietary sugar concentrations

This study was conducted to determine the effects of feeding Fermenten (Church and Dwight Co., Princeton, NJ) with or without dietary sucrose on ruminal fermentation, apparent total-tract nutrient digestibility, and nutrient utilization. Eight ruminally cannulated Holstein cows (163 ± 55 d in milk; mean ± standard deviation) were used in a replicated 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments. Experimental diets were formulated with and without Fermenten (0 vs. 3.3% of dietary DM) at 2 dietary sugar concentrations (2.8 vs. 5.7%). Dietary treatment did not affect dry matter intake or apparent total-tract nutrient digestibility. Feeding Fermenten did not affect ruminal pH, but high-sugar diets tended to increase the daily minimum pH (5.61 vs. 5.42) and mean pH (6.17 vs. 6.30) compared with low-sugar diets. Ruminal ammonia concentration tended to be greater for cows fed Fermenten compared with control (18.1 vs. 15.9 mg/dL), but was not affected by dietary sugar concentration. Significant interactions between Fermenten and dietary sugar concentration were detected for some milk production responses. Fermenten treatment numerically increased milk fat yield (0.92 vs. 0.82 kg/d), 4% fat-corrected milk yield (24.3 vs. 21.9 kg/d), and milk energy output (18.2 vs. 16.4 Mcal/d) compared with control for cows fed low-sugar diets, but not for cows fed high-sugar diets. Increasing dietary sugar concentration did not enhance the effects of Fermenten, providing no support for the theory that synchronizing the availability of N and fermentable energy in the rumen improves nutrient utilization in lactating dairy cows.     

Production response of multiparous Holstein cows treated with bovine somatotropin and fed diets enriched with n-3 or n-6 fatty acids

Multiparous cows (n = 59) were blocked by expected calving date and previous milk yield and assigned randomly to treatments to determine the effects of bovine somatotropin (bST; Posilac, Monsanto Animal Agricultural Group, St. Louis, MO) and source of dietary fat on production responses. Diets were provided from calving and included whole, high-oil sunflower seeds [SS; 10% of dietary dry matter (DM); n-6:n-3 ratio of 4.6] as a source of linoleic acid (18:2) or a mixture of Alifet-High Energy and Alifet-Repro (AF; Alifet USA, Cincinnati, OH; 3.5 and 1.5% of dietary DM, respectively; n-6/n-3 ratio of 2.6) as a source of protected n-3 fatty acids. Diets contained 181 versus 188 g of crude protein and 183 versus 186 g of acid detergent fiber/kg of DM and 1.54 versus 1.66 Mcal of net energy for lactation at the actual DM intake for SS versus AF, respectively. Cows received 0 or 500 mg of bST every 10 d from 12 to 70 d in milk (DIM) and at 14-d intervals through 280 DIM. The 2 × 2 factorial combination of diet (SS or AF) with or without bST administration resulted in treatments designated as SSY, SSN, AFY, and AFN, respectively. Data were analyzed as repeated measures using mixed model procedures to determine the effects of diet, bST, and their interactions. Yield of 3.5% fat-corrected milk was not altered by diet, but was increased by 4.0 ± 1.9 kg/d from 12 to 70 DIM and by 5.1 ± 1.2 kg/d from 12 to 280 DIM by bST. Treatment did not affect DM intake or energy balance (EB) nadir. There was an interaction of bST and diet on EB because AF decreased the impact of bST on overall EB and allowed AFY cows to reach a positive EB earlier than SSY cows. Gross feed efficiency adjusted for body weight change was greater for bST-treated cows (1.03 vs. 1.15 ± 0.03 kg of fat-corrected milk/Mcal of net energy for lactation). Circulating insulin-like growth factor-I concentrations were increased by bST (85 vs. 125 ± 8 ng/mL). Body weight, body condition score, and backfat thickness were reduced by bST, but differences between treated and nontreated cows did not differ by 280 DIM. Results indicate cows responded to bST administration in early lactation, but the magnitude of the response was greater after 70 DIM. Source of dietary fat had a minimal effect on most production measurements, but relative to SS, AF decreased the impact of bST on overall EB. Results support the premise that bST administration prolongs the delay in postpartum tissue replenishment.     

Prepartum dietary management of energy intake affects postpartum intake and lactation performance by primiparous and multiparous Holstein cows

An experiment was conducted to determine the effect of plane of energy intake prepartum on postpartum performance. Primiparous (n = 24) and multiparous (n = 23) Holsteins were randomly assigned by expected date of parturition to 1 of 3 prepartum energy intakes. A moderate energy diet [1.63 Mcal of net energy for lactation (NE_L)/kg; 15% crude protein (CP)] was fed for either ad libitum intake (OVR) or restricted intake (RES) to supply 150 or 80% of National Research Council (2001) energy requirement, respectively, for dry cows in late gestation. To limit energy intake to 100% of NRC requirement at ad libitum dry matter intake (DMI), chopped wheat straw was included as 31.8% of dry matter (DM) in a control diet (CON; 1.21 Mcal of NE_L/kg of DM; 14% CP). Multiparous and primiparous cows assigned to OVR gained body condition during the dry period [initial body condition score (BCS) = 3.3], but were not overconditioned by parturition (BCS = 3.5). Multiparous cows in the OVR group lost more BCS postpartum than multiparous RES or CON cows. Primiparous cows lost similar amounts of BCS among dietary treatment groups postpartum. Addition of chopped wheat straw to CON diets prevented a large decrease in DMI prepartum in both primiparous and multiparous cows. During the first 3 wk postpartum, DMI as a percentage of BW was lower for multiparous OVR cows than for multiparous RES cows. Prepartum diet effects did not carry over through the entire 8-wk lactation period. Because of greater mobilization of body stores, OVR cows had greater milk fat percentage and greater 3.5% fat-corrected milk yield during the first 3 wk postpartum. Multiparous cows assigned to OVR experienced a 55% decrease in energy balance and primiparous cows a 40% decrease in energy balance during the last 3 wk before parturition, compared with CON or RES cows that had little change. Multiparous cows fed OVR had a greater contribution of energy from body energy reserves to milk energy output than either CON or RES cows. Overfeeding energy prepartum resulted in large changes in periparturient energy balance. Even in the absence of overconditioning, a large change in DMI and energy balance prepartum influenced postpartum DMI and BCS loss, especially for multiparous cows. Chopped wheat straw was effective at controlling energy intake prepartum, although primiparous cows did not achieve predicted DMI. Even so, controlling or restricting energy intake in primiparous cows was not detrimental to lactational performance over the first 8 wk of lactation.     

An evaluation of exogenous enzymes with amylolytic activity for dairy cows

An experimental (7B) and a commercial (AMA) formulation of enzymes, both primarily with α-amylase activity, were evaluated for activity at various pH values, stability in ruminal fluid, the potential to improve in vitro ruminal fermentations, and the potential to improve production performance of lactating cows. When incubated (40°C) in buffer with a pH between 5.4 and 6.0, 7B had about 10 to 25 times greater amylase activity than AMA, and enzyme activity in this range increased by 100% for 7B, whereas activity decreased by about 26% for AMA. Both formulations maintained enzyme activity when they were incubated in in vitro ruminal fermentations for 24 h. After 6 h of ruminal in vitro fermentation, additions of 7B resulted in linear increases in apparent total volatile fatty acid production for flint and dent corn but had no effect on floury corn. In a lactation trial, 28 Holstein cows (68 ± 31 d in milk, 46.9 ± 9.1 kg of milk/d) were fed a total mixed ration (TMR) supplemented with nothing (CON), a low dose of 7B [7BL, 0.88 mL/kg of TMR dry matter (DM)], a high dose of 7B (7BH, 4.4 mL/kg of TMR DM), or AMA (0.4 g/kg of TMR DM). The experiment was conducted as a 4. 4 Latin square design with 21-d periods. Cows fed 7BL, 7BH, and AMA ate similar amounts of DM, and cows fed the latter 2 diets consumed more DM than did cows fed CON. Cows fed 7BL produced more milk than cows fed CON and 7BH, but produced similar amounts to cows fed AMA. The production of 3.5% fat-corrected milk was greater from cows fed 7BL and AMA compared with cows fed CON. The percentages of milk fat and milk protein were unaffected by treatment. Total-tract digestion of DM and organic matter were greater for cows fed 7BL compared with those fed CON. The addition of exogenous amylase enzymes to the diets of lactating dairy cows has the potential to improve animal productivity.     

Effect of saturated fatty acid supplementation on production and metabolism indices in heat-stressed mid-lactation dairy cows

Experimental objectives were to determine the effects of supplemental saturated fatty acids on production, body temperature indices, and some aspects of metabolism in mid-lactation dairy cows experiencing heat stress. Forty-eight heat-stressed Holstein cows were allocated into 3 groups (n = 16/group) according to a completely randomized block design. Three treatment diets consisted of supplemental saturated fatty acids (SFA) at 0 (SFA0), 1.5 (SFA1.5), or 3.0% (SFA3) of dry matter (DM) for 10 wk. Diets were isonitrogenous (crude protein = 16.8%) and contained 1.42, 1.46, and 1.49 Mcal of net energy for lactation/kg of DM for the SFA0, SFA1.5 and SFA3 diets, respectively. The average temperature-humidity index at 0700, 1400 and 2200 h was 72.2, 84.3, and 76.6, respectively. Rectal temperatures at 1400 h were decreased with fat supplementation. Treatment did not affect dry matter intake (20.1 ± 0.02 kg/d), body condition score (2.72 ± 0.04), body weight (627 ± 16.1 kg), or calculated energy balance (1.32 ± 0.83 Mcal/d). Saturated fatty acid supplementation increased milk yield, milk fat content, and total milk solids. Increasing fat supplementation decreased plasma nonesterified fatty acids (8%) but had no effect on other energetic metabolites or hormones. In summary, supplemental SFA improved milk yield and milk fat content and yield and reduced peak rectal temperatures in mid-lactation heat-stressed dairy cows. This demonstrates the remarkable amount of metabolic heat that is “saved” by energetically replacing fermentable carbohydrates with supplemental SFA.     

Dried distillers grains plus solubles with corn silage or alfalfa hay as the primary forage source in dairy cow diets

Nine multiparous (250 ± 6 d in milk) and 3 primiparous (204 ± 6 d in milk) Holstein cows were utilized in a 3 × 3 Latin square design to evaluate the lactation performance of cows fed a diet containing dried distillers grains plus solubles (DDGS) with either corn silage or alfalfa hay as forage. Cows were fed total mixed diets containing corn silage (CS), 50% corn silage and 50% alfalfa hay (CSAH), or alfalfa hay (AH) as the forage source. All diets had a 50:50 forage-to-concentrate ratio, contained 15% DDGS, and were formulated to be equal in metabolizable protein. Dry matter intake increased when cows were fed CSAH (24.9 kg/d) compared with CS (21.9 kg/d) and AH (20.9 kg/d). Yields of milk (26.5, 28.4, 29.0 kg/d for CS, CSAH, and AH, respectively) increased linearly as proportions of alfalfa fed increased but 4% fat-corrected milk and energy-corrected milk were not affected by treatment. Feed efficiency (1.28, 1.23, and 1.45 kg of energy-corrected milk/kg of intake) improved when AH was fed compared with CS or CSAH. Milk fat concentration (3.67, 3.55, and 3.49%) decreased linearly when alfalfa replaced corn silage, but was observed only in primiparous cows, not multiparous cows. Milk protein concentration (3.32, 3.29, and 3.29%) was not affected by diet although yield (0.90, 0.96, and 0.98 kg/d) tended to increase linearly when alfalfa was added to the diet. This may have been due to an increase in essential amino acid (AA) availability and uptake by the mammary gland or to greater crude protein intake in cows fed AH. In addition, replacing corn silage with alfalfa increased the uptake of Lys by the mammary gland. Methionine was the first-limiting AA based on the transfer efficiency of AA in arterial plasma to milk protein. However, Lys was the first-limiting AA in CS and CSAH and Met was first limiting in AH for mammary gland extraction efficiency of AA from plasma. In conclusion, replacing corn silage with alfalfa hay in diets containing 15% DDGS increased milk yield and tended to increase milk protein yield linearly in cows during late lactation. Feeding alfalfa hay as the sole forage source improved feed efficiency compared with diets containing corn silage.     

Effects of feeding increasing levels of wet corn gluten feed on production and ruminal fermentation in lactating dairy cows

An experiment was conducted to evaluate the effects of increasing dietary inclusion rates of wet corn gluten feed (WCGF; Sweet Bran; Cargill Inc., Blair, NE) on milk production and rumen parameters. Four primiparous and 4 multiparous ruminally cannulated Holstein cows averaging 90 ± 13 d in milk (mean ± SD) were randomly assigned to 1 of 4 sequences in a replicated 4 × 4 Latin square experiment with 28-d periods. Treatments were diets containing 0, 11, 23, and 34% WCGF on a dry matter basis; alfalfa hay, corn silage, corn grain, soybean meal, expeller soybean meal, and mineral supplements were varied to maintain similar nutrient concentrations across diets. Performance and measures of ruminal fermentation were monitored. Linear and quadratic effects of increasing WCGF inclusion rate were assessed using mixed-model analysis. Increasing dietary WCGF linearly increased dry matter intake (26.7, 25.9, 29.3, and 29.7 kg/d for 0, 11, 23, and 34% WCGF, respectively) and milk production (36.8, 37.0, 40.1, and 38.9 kg/d). Concentrations of milk components did not differ among treatments; however, protein and lactose yields increased linearly and fat yield tended to increase linearly when more WCGF was fed. This led to greater production of energy-corrected milk (38.2, 38.8, 41.7, and 40.4 kg/d) and solids-corrected milk (35.2, 35.7, 38.5, and 37.2 kg/d), but efficiency of production linearly decreased. Increased WCGF in the diet tended to linearly decrease ruminal pH (6.18, 6.12, 6.14, and 5.91), possibly because mean particle size was below typical recommendations for all diets, and diets with greater proportions of WCGF had a smaller mean particle size. Ruminal acetate concentration decreased linearly and propionate increased linearly as WCGF inclusion rate increased. Treatments had a quadratic effect on ammonia concentration, with greater concentrations for the 0 and 34% WCGF diets. In situ digestibility of soybean hulls showed a significant diet-by-time interaction, and increasing dietary levels of WCGF linearly decreased in situ neutral detergent fiber disappearance at 24 h. Change in body condition score increased linearly with increasing WCGF inclusion rate. Results indicate that adding WCGF to dairy rations can increase energy-corrected milk yield, and this increase appears to be driven, at least in part, by an increase in dry matter intake.     

Effects of rumen-protected γ-aminobutyric acid on performance and nutrient digestibility in heat-stressed dairy cows

This experiment was conducted to investigate the effects of rumen-protected γ-aminobutyric acid (GABA) on performance and nutrient digestibility in heat-stressed dairy cows. Sixty Holstein dairy cows (141 ± 15 d in milk, 35.9 ± 4.3 kg of milk/d, and parity 2.0 ± 1.1) were randomly assigned to 1 of 4 treatments according to a completely randomized block design. Treatments consisted of 0 (control), 40, 80, or 120 mg of true GABA/kg of dry matter (DM). The trial lasted 10 wk. The average temperature-humidity indices at 0700, 1400, and 2200 h were 78.4, 80.2, and 78.7, respectively. Rectal temperatures decreased linearly at 0700, 1400, and 2200 h with increasing GABA concentration. Supplementation of GABA had no effect on respiration rates at any time point. Dry matter intake, energy-corrected milk, 4% fat-corrected milk, and milk fat yield tended to increase linearly with increasing GABA concentration. Supplementation of GABA affected, in a quadratic manner, milk protein and lactose concentrations, and milk protein yield, and the peak values were reached at a dose of 40 mg of GABA/kg. Milk urea nitrogen concentration responded quadratically. Total solids content increased linearly with increasing GABA concentration. Supplementation of GABA had no effect on milk yield, lactose production, total solids, milk fat concentration, somatic cell score, or feed efficiency. Apparent total-tract digestibilities of DM, organic matter, crude protein, neutral detergent fiber, and acid detergent fiber were similar among treatments. These results indicate that rumen-protected GABA supplementation to dairy cows can alleviate heat stress by reducing rectal temperature, increase DM intake and milk production, and improve milk composition. The appropriate supplemental GABA level for heat-stressed dairy cows is 40 mg/kg of DM.     

Dietary protein quality and quantity affect lactational responses to corn distillers grains: a meta-analysis

Diet fermentability influences lactational responses to feeding corn distillers grains (CDG) to dairy cows. However, some measures of diet fermentability are inherently related to the concentration and characteristics of corn-based ingredients in the ration. Corn-based feeds have poor protein quality, unable to meet the essential AA requirements of lactating cows. We conducted a meta-analysis of treatment means (n = 44) from the scientific literature to evaluate responses in milk yield (MY) and milk true protein concentration and yield to dietary CDG. The test variable was the difference in response between the CDG diet mean and the control diet mean (0% CDG) within experiment. Fixed variables were CDG concentration of the diet [% of dietary dry matter (DM)] and crude protein (CP) concentration and fractions of CP based on origin (corn-based versus non-corn-based feeds) of control and CDG diets. Diets with CDG ranged from 4 to 42% CDG, DM basis. Non-corn-based dietary CP averaged 6.3 ± 3.32% of total DM. Milk yield and milk true protein yield responses to added CDG were maximized when approximately 8.5% of the total dietary DM was non-corn-based CP. Milk yield response peaked for higher-producing cows (>30.0 kg MY/cow per day) at 4.3% dietary corn-based CP, but decreased linearly for lower-producing cows (<30.0 kg MY/cow per day) as corn-based dietary CP increased. Milk true protein yield response decreased as corn-based dietary CP concentration increased but milk true protein concentration response was not decreased when CDG diets had more than 6.5% dietary non-corn-based CP. Overall, 8.5% dietary non-corn-based CP was necessary in lactation diets to maximize lactational responses to dietary CDG. The necessity of dietary non-corn-based CP to maximize milk and milk protein yields limits the amount of dietary corn-based CP, including that from CDG, which can be included in rations without overfeeding N.     

Comparative evaluation of alternative forages to grass silage in the diet of early lactation dairy cows

Fifty-six autumn-calving Holstein-Friesian cows, blocked on the basis of days in milk (27.6 ± 10.65 d), lactation number (3.1 ± 2.21), and preexperimental milk yield (28.4 ± 6.69 kg) were used to examine the effects of replacing 330 g/kg of dry matter (DM) of first-cut perennial ryegrass silage with either fermented whole-crop wheat (WCW), urea-treated processed WCW, or corn silage on subsequent feed intake, milk production, and efficiency of nitrogen utilization. The DM (g/kg), crude protein (CP, g/kg of DM) and in vitro DM digestibility (g/kg) of the forages were 204, 179, and 762 for grass silage; 389, 90, and 711 for fermented WCW; 795, 141, and 768 for urea-treated processed WCW; and 346, 93, and 783 for corn silage, respectively. Four forage treatments were evaluated as follows: 1) grass silage as the sole forage (GS); 2) a mixture of grass silage and fermented WCW silage, (F-WCW); 3) a mixture of grass silage and urea-treated processed WCW, (UP-WCW); and 4) a mixture of grass silage and corn silage (CS). In all cases, the alternative forages comprised 67% of the forage mix on a DM basis. Isonitrogenous diets were formulated by offering all cows 8 kg of concentrate as fed, formulated to different CP concentrations. Cows were offered these diets from 28 to 104 d in milk. Total DM intake and milk yield were greater on UP-WCW (20.0 and 30.2 kg/d) and CS (18.3 and 33.2 kg/d) than on GS (13.5 and 26.5 kg/d). Although DM intake was greater on F-WCW (17.1 kg/d) than on GS, milk yield was not significantly greater (+2.7 kg/d). Milk protein concentration was greater on F-WCW (30.5 g/kg), UP-WCW (31.3 g/kg), and CS (30.7 g/kg) than on GS (28.5 g/kg). However, there was no difference between treatments in milk fat or lactose concentrations. Body weight change was greater for cows offered GS (−0.27 kg/d) than for those offered UP-WCW (−0.01 kg/d) and CS (+0.05 kg/d) but not compared with those offered F-WCW (−0.06 kg/d). There was no effect of treatment on plasma glucose, nonesterified fatty acids, β-hydroxybutyrate, urea, or total protein at d 64 ± 17.4 and d 92 ± 17.4 postpartum. Efficiency of N utilization was greatest for CS with 0.36 of N intake being recovered in milk compared with 0.28, 0.32, and 0.26 for GS, F-WCW, and UP-WCW, respectively. There was no effect of treatment on milk urea N concentration or the urinary allantoin N to creatinine N ratio. The results of this experiment indicate that corn silage is a more suitable supplementary forage to grass silage than fermented or urea-treated processed WCW, with advantages realized in milk production and more efficient N utilization.