S.J. Bertics

Effect of feeding a reduced-starch diet with or without amylase addition on lactation performance in dairy cows.

The objective of this study was to determine lactation performance responses of high-producing dairy cows to a reduced-starch diet compared with a normal-starch diet and to the addition of exogenous amylase to the reduced-starch diet. Thirty-six multiparous Holstein cows (51+/-22 DIM and 643+/-49kg of body weight at trial initiation) were randomly assigned to 1 of 3 treatments in a completely randomized design: a 3-wk covariate adjustment period during which the cows were fed the normal-starch diet, followed by a 12-wk treatment period during which the cows were fed their assigned treatment diets. The normal-starch TMR did not contain exogenous amylase (NS-). The reduced-starch diets, formulated by partially replacing corn grain with soy hulls, were fed without (RS-) and with (RS+) exogenous amylase added to the TMR. Starch and NDF concentrations averaged 27.1 and 30.6%, 21.8 and 36.6%, and 20.7 and 36.6% (dry matter basis) for the NS-, RS-, and RS+ diets, respectively. Dry matter intake for cows fed the RS- diet was 2.4 and 3.2kg/d greater than for cows fed the NS- and RS+ diets, respectively. Intake of NDF ranged from 1.19 to 1.52% of body weight among the treatments, with the RS- diet being 28% greater than the NS- diet and 13% greater than the RS+ diet. Milk yield averaged 50.4kg/d and was unaffected by treatment. Fat-corrected milk yield was 2.9kg/d greater for cows fed the RS- diet than for cows fed the NS- diet. Body weight and body condition score measurements were unaffected by treatment. Fat-, solids-, and energy-corrected milk feed conversions (kilograms/kilogram of DMI) were 12 to 13% greater for cows fed the RS+ diet than for cows fed the RS- diet. Dry matter and nutrient digestibilities were lowest for cows fed the NS- diet and greatest for cows fed the RS+ diet, and were greater for cows fed the RS+ diet than for cows fed the RS- diet, with the exception of starch digestibility, which was similar. Greater conversion of feed to milk for dairy cows fed reduced-starch diets that include exogenous amylase may offer potential for improving economic performance.

Type of corn endosperm influences nutrient digestibility in lactating dairy cows

An experiment was conducted to evaluate the effect of type of corn endosperm on nutrient digestibility in lactating dairy cows. Near-isogenic variants of an Oh43 x W64A normal dent endosperm hybrid carrying floury-2 or opaque-2 alleles were grown in spatial isolation in field plots and harvested as dry shelled corn. Six ruminally cannulated, multiparous Holstein cows (67 +/- 9 d in milk at trial initiation) were randomly assigned to a replicated 3 x 3 Latin square design with 14-d periods; the first 11 d of each period were for diet adaptation followed by 3 d of sampling and data collection. Treatment diets that contained dry rolled vitreous-, floury-, or opaque-endosperm corn [33% of dry matter (DM)], alfalfa silage (55% of DM) and protein-mineral-vitamin supplement (12% of DM) were fed as a total mixed ration. The percentage vitreous endosperm was zero for floury and opaque endosperm corns and 64 +/- 7% for the vitreous corn. Prolamin protein content of floury and opaque endosperm corns was 30% of the content found in vitreous corn. Degree of starch access and in vitro ruminal starch digestibility measurements were 32 and 42% greater on average, respectively, for floury and opaque endosperm corns than for vitreous corn. Dry matter and starch disappearances after 8-h ruminal in situ incubations were, on average, 24 and 32 percentage units greater, respectively, for floury and opaque endosperm corns than for vitreous corn. Ruminal pH and acetate molar percentage were lower, propionate molar percentage was greater, and acetate:propionate ratio was lower for cows fed diets containing floury and opaque endosperm corns than for cows fed vitreous corn. In agreement with laboratory and in situ measurements, total-tract starch digestibility was 6.3 percentage units greater, on average, for cows fed diets containing floury and opaque endosperm corns than vitreous corn. Conversely, apparent total-tract neutral detergent fiber (NDF) digestibility was lower for cows fed diets containing floury and opaque endosperm corns compared with vitreous corn. The type of endosperm in corn fed to dairy cows can have a marked effect on digestion of starch and NDF. Feeding less vitreous corn increased starch digestion but decreased NDF digestion.

Influence of a reduced-starch diet with or without exogenous amylase on lactation performance by dairy cows

The objective of this trial was to determine lactation performance responses in high-producing dairy cows to a reduced-starch versus a normal-starch diet and to the addition of exogenous amylase to the reduced-starch diet. Forty-five multiparous Holstein cows, 68±29 d in milk and 696±62 kg of body weight (BW) at trial initiation, were randomly assigned to 1 of 3 treatments in a completely randomized design; a 2-wk covariate adjustment period with cows fed the normal-starch diet was followed by a 10-wk treatment period with cows fed their assigned treatment diets. The normal-starch total mixed ration did not contain exogenous amylase (NS-). The reduced-starch diets, formulated by partially replacing corn grain and soybean meal with whole cottonseed and wheat middlings, were fed without (RS-) and with (RS+) exogenous amylase addition to the total mixed ration. All diets contained 50% forage and 19.8% forage neutral detergent fiber (dry matter basis). Starch and neutral detergent fiber concentrations averaged 27.0 and 30.9%, 22.1 and 35.0%, and 21.2 and 35.3% (dry matter basis) for the NS-, RS-, and RS+ diets, respectively. Expressed as a percentage of BW, dry matter intake was greater for cows fed RS- than for cows fed NS- or RS+. Intake of neutral detergent fiber ranged from 1.09 to 1.30% of BW among the treatments, with that of RS- being 21% greater than that of NS-. Milk yield tended to be greater for cows fed NS- compared with the RS diets. Milk fat content and yield were unaffected by treatment. Milk protein content and yield were greater for cows fed NS- compared with the RS diets. Concentrations of milk urea nitrogen were greater for cows fed RS diets compared with the NS- diet. Body weight, BW change, and body condition score were unaffected by treatment. Feed conversion (kg of milk/kg of dry matter intake) was 10% greater on average for cows fed NS- than for cows fed the RS diets, and tended to be 6% greater for cows fed RS+ compared with RS-. Feeding a reduced-starch diet formulated by partially replacing corn grain and soybean meal with a wheat middlings and whole cottonseed mixture compared with a normal-starch diet without addition of exogenous amylase to either diet reduced milk and component-corrected feed conversions. Addition of exogenous amylase to a reduced-starch diet was of minimal benefit in this study.

Effect of rumen-protected niacin on lipid metabolism, oxidative stress, and performance of transition dairy cows

The objective of this study was to evaluate the effect of a rumen-protected niacin product (RPN; 65% nicotinic acid; NiaShure, Balchem Corp., New Hampton, NY) on lipid metabolism, oxidative stress, and performance of transition dairy cows. Thirty nonlactating multiparous Holstein cows in late gestation were paired according to expected calving date and randomly assigned to 12 g/cow per day of RPN product or to an unsupplemented control (CON) diet. Treatment diets were fed from 21 d before expected calving through 21 d after parturition. Blood samples were taken on d -21, -14, -7, 1, 7, 14, and 21 relative to calving for plasma nonesterified fatty acid (NEFA), β-hydroxybutyrate (BHBA), glucose, and superoxide dismutase (SOD) analyses. Liver samples were taken by biopsy on d 1 and 21 relative to calving for triglyceride (TG) analysis. Data were analyzed for a randomized complete block design with repeated measures. Pre- and postpartum dry matter intake, milk yield, and protein were unaffected by treatment. Milk fat percentage (5.08 vs. 4.44%) and somatic cell score (3.93 vs. 2.48) were reduced for RPN. Treatment × time interactions were observed for energy-corrected milk (ECM) and fat-corrected milk (FCM) yields; RPN reduced ECM and FCM yields by 8.5 and 8.9 kg/cow per day, respectively, in the first week of lactation. Although body weight and condition score decreased during the experimental period, no differences due to treatment were observed. However, calculated postpartum energy balance tended to be improved for RPN because of the reduction in ECM yield. Time and treatment × time effects were observed for plasma NEFA. On d 1 postpartum, NEFA reached 1,138±80 μEq/L for CON compared with 698±80 μEq/L for RPN. Cows supplemented with RPN tended to have lower plasma NEFA concentrations than CON cows on d 7 and 14 postpartum. Plasma BHBA, glucose, and SOD and liver TG concentrations were unaffected by treatment. In conclusion, supplementation with 12 g/cow per day of the RPN product provided a bioavailable source of niacin that modified lipid metabolism but did not affect milk yield over the first 3 wk of lactation or oxidative stress of transition dairy cows.

Effect of dietary supplementation with live-cell yeast at two dosages on lactation performance, ruminal fermentation, and total-tract nutrient digestibility in dairy cows

The experimental objective was to determine the effect of dietary supplementation with live-cell yeast (LCY; Procreatin-7, Lesaffre Feed Additives, Milwaukee, WI) at 2 dosages in high-starch (HS) diets [30% starch in dry matter (DM)] on lactation performance, ruminal fermentation, and total-tract nutrient digestibility in dairy cows compared with HS or low-starch (LS; 20% starch in DM) non-LCY diets. Sixty-four multiparous Holstein cows (114 ± 37 d in milk and 726 ± 74 kg of body weight at trial initiation) were randomly assigned to 32 electronic gate feeders (2 cows per feeder), which were randomly assigned to 1 of 4 treatments in a completely randomized design. A 2-wk covariate adjustment period with cows fed a 50:50 mixture of the HS and LS diets was followed by a 12-wk treatment period with cows fed their assigned treatment diets. The HS diets were fed without (HS0) and with 2 (HS2) or 4 (HS4) g/cow per day of LCY. The LS diet did not contain LCY (LS0) and was formulated by partially replacing dry ground shelled corn with soy hulls. Cows fed LS0 consumed more DM than cows fed HS diets during wk 3, 10, 11, and 12. Yields of actual (44.5 kg/d, on average), fat-, energy-, and solids-corrected milk were unaffected by treatment. Milk fat content tended to be greater for LS0 than for HS0 and HS2 but not different from HS4. Milk urea nitrogen contents were greater for cows fed LS0 than for cows fed the HS diets. Feed conversion (kg of milk/kg of DM intake) was numerically greater for HS diets than for LS0. Ruminal pH was unaffected by treatment. Ruminal molar proportion of acetate was greater, whereas that of propionate was lower, for LS0 compared with HS diets. Dry matter and organic matter digestibilities were greater for HS2 and HS4 than for HS0. Digestibility of neutral detergent fiber was greater for HS4 than for HS0 and HS2. Dry matter, organic matter, and neutral detergent fiber digestibilities were greater for LS0 than for HS diets; starch digestibility was greater for LS0 than for HS0 and HS4. Feeding LS0 increased DM intake and milk fat content, but reduced feed conversions. The addition of 4 g/cow per day of LCY to HS diets tended to increase milk fat content and increased total-tract fiber digestibility in dairy cows.

Effects of cobalt supplementation and vitamin B12 injections on lactation performance and metabolism of Holstein dairy cows

The objective of this study was to determine lactation performance and metabolism of primiparous and multiparous dairy cows fed different levels and sources (inorganic and organic) of Co or given weekly vitamin B(12) injections. Forty-five primi- and multiparous cows at 60 d prepartum were blocked by expected calving date, and randomly assigned to 1 of 5 treatments in a randomized complete block design with treatments starting at 60 d prepartum. The 5 treatments were (1) no supplemental dietary Co (control, CON), (2) 25mg/d of supplemental dietary Co from Co carbonate (CoCarb), (3) 25mg/d of supplemental dietary Co from Co glucoheptonate (LCoGH), (4) 75 mg/d of supplemental dietary Co from Co glucoheptonate (HCoGH), and (5) CON diet plus weekly 10mg i.m. of vitamin B(12) injections (IB12). Cows remained on their respective treatment until 150 d after calving. Cobalt concentrations (mg/kg of dry matter) in the lactating diets were 1.0, 1.9, 2.3, and 5.1 for CON/IB12, CoCarb, LCoGH, and HCoGH, respectively. Dry matter intake, body weight, and body condition score were not affected by treatment. The LCoGH treatment tended to have greater milk yield than CoCarb, and CON had similar milk yields to the mean of LCoGH and HCoGH. Cobalt supplementation or the use of vitamin B(12) injections did not influence plasma or liver measures of energy metabolism. Injections of vitamin B(12) increased plasma, liver, and milk vitamin B(12) contents. Dietary Co addition did not affect plasma vitamin B(12) concentrations; however, it did increase milk vitamin B(12) concentrations throughout lactation and liver vitamin B(12) at calving with no effect of source or level of Co. Folate status of cows in the study was low and possibly limited the effect of improved vitamin B(12) status on lactation performance. Overall, Co supplementation (inorganic and organic) or vitamin B(12) injections improved measures of vitamin B(12) status, but not lactation performance compared with CON possibly due to Co being above requirements in the CON diet.

Rumen and milk odd- and branched-chain fatty acid proportions are minimally influenced by ruminal volatile fatty acid infusions

The objective of this study was to determine if ruminally infusing volatile fatty acid (VFA) increased concentration of their homologous odd- and branched-chain fatty acid (OBCFA) in rumen contents and milk. The influence of VFA on dry matter intake (DMI), blood metabolites, and blood insulin was also evaluated. Four mid-lactation cows were assigned to a 4×4 Latin square design with 48-h periods. Infusion treatments were acetate (AC), propionate (PR), isovalerate (IV), and anteisovalerate (AIV). Infusions began (time = 0) 5.5 h before feeding at 17.4 mmol of VFA/min and were terminated at 18 h. Infusions rates were well above physiological levels for IV and AIV. Surprisingly, the greatest differences in rumen OBCFA were increases in rumen liquid iso C15:0 and nonbranched C17:0 for AIV. In addition, infusing AIV increased anteiso C15:0 and anteiso C17:0 in rumen solid contents. Infusing IV increased iso C15:0 in both rumen solids and milk. Propionate increased milk C15:0 and C17:0. Both gluconeogenic compounds, PR and AIV, had similar proportions of milk C15:0, which was greater than that obtained with AC and IV. Rumen and blood VFA were as expected, with increased concentrations of the VFA present in the infusate. At 23 h, and consistently throughout infusions, DMI was similar for AC compared with PR and for AIV compared with IV. Both IV and AIV decreased DMI and energy balance; however, only IV increased plasma nonesterified fatty acids (121, 78, 172, and 102 mM for AC, AIV, IV, and PR), increased β-hydroxybutyrate (10.8, 5.9, 51.9, 5.4 mg/dL for AC, AIV, IV, and PR), and reduced plasma glucose (56.3, 59.1, 31.9, and 64.3 mg/dL for AC, AIV, IV, and PR). Rumen and milk OBCFA responses were minimal following infusion of large amounts of IV and AIV, suggesting limited use of IV, and AIV for de novo OBCFA synthesis, either pre- or postabsorption. Minor increases in milk odd-chain fatty acids following large doses of ruminal PR support the presence of postabsorptive synthesis of these milk odd-chain fatty acids.

Effect of monensin in lactating dairy cow diets at 2 starch concentrations

The objective of this study was to determine the effects of monensin (M) supplementation on lactation performance of dairy cows fed diets of either reduced (RS) or normal (NS) starch concentrations as total mixed rations. One hundred twenty-eight Holstein and Holstein × Jersey cows (90 ± 33 d in milk) were stratified by breed and parity and randomly assigned to 16 pens of 8 cows each in a randomized controlled trial. Pens were then randomly assigned to 1 of 4 treatments in a 2 × 2 factorial arrangement of treatments. A 4-wk covariate adjustment period preceded the treatment period, with all pens receiving NS supplemented with 18 g of monensin/t of dry matter (DM). Following the 4-wk covariate adjustment period, cows were fed their assigned treatment diets of NS with M (18 g of monensin/t), NS with 0 g of monensin/t (C), RS with M, or RS with C for 12 wk. Actual starch concentrations for the RS and NS diets were 20.4 and 26.9% (DM basis), respectively. Mean dry matter intake (DMI; 27.0 kg/d) was unaffected by the treatments. Feeding M compared with C and NS compared with RS increased milk yield by 1.3 and 1.5 kg/d per cow, respectively. Milk protein percentage and yield and lactose yield were increased and milk urea nitrogen was decreased for NS compared with RS. Feeding M increased actual and component-corrected milk feed efficiencies (component-corrected milk yield/DMI) and lactose yield and tended to increase milk urea nitrogen compared with C. Milk protein percentage was decreased for M compared with C, but milk fat percentage and yield, protein yield, and lactose percentage were unaffected by M. We observed a tendency for a starch × monensin interaction for milk feed efficiency (actual milk yield/DMI); M tended to increase efficiency more for NS than for RS. Starch and monensin had minimal effects on milk fatty acid composition and yields. Feeding RS decreased milk and protein yields, but component-corrected milk yields and feed efficiencies were similar for RS and NS. Monensin increased feed efficiency and lactation performance for both dietary starch concentrations.

Effects of corn-based diet starch content and corn particle size on lactation performance, digestibility, and bacterial protein flow in dairy cows

An experiment was conducted to determine the effects of dietary starch content in corn-based diets and corn particle size on lactation performance, nutrient digestibility, and bacterial protein flow in dairy cows using the omasal and reticular sampling technique. Eight ruminally cannulated lactating multiparous Holstein cows were used in a replicated 4×4 Latin square design with a 2×2 factorial arrangement of treatments. Treatments were fine (FG; mean particle size=552µm) and coarse (CG; 1,270µm) ground dry shelled corn in normal- (NS) and reduced- (RS) starch diets fed as total mixed rations. The NS and RS rations contained 27 and 18% starch (dry matter basis), respectively, and were formulated by partially replacing corn with soy hull pellets. Mean dry matter intake was unaffected by treatment (23.2kg/d). Cows fed NS diets produced 1.9kg/d more milk and 0.06kg/d more milk protein compared with cows fed RS diets. Cows fed NSFG and RSCG diets produced more fat-corrected milk than did cows fed NSCG and RSFG diets. Milk urea concentration was decreased for cows fed NS diets (12.4mg/dL) compared with RS diets (13.5mg/dL). Ruminal digestibility of neutral detergent fiber (NDF; % of NDF intake) determined by the omasal sampling technique was increased in cows fed RS diets compared with NS diets (43.4 vs. 34.9%), and total-tract digestibility of NDF (% of NDF intake) was increased in cows fed RS diets compared with those fed NS diets (50.1 vs. 43.1%). Ruminal digestibility of starch (% of starch intake) determined by the omasal sampling technique was greater in cows fed NS diets compared with those fed RS diets (85.6 vs. 81.6%). Total-tract starch digestion was increased in cows fed RS diets compared with those fed NS diets (96.9 vs. 94.6%) and in cows fed FG diets compared with those fed CG diets (98.0 vs. 93.5%). Bacterial protein flow was unaffected by treatment. The omasal and reticular sampling techniques resulted in similar treatment effects for nutrient flow and digestibility, although nutrient flow was lower and nutrient digestibility was greater in cows when sampled by the omasal technique compared with the reticular technique. Cows fed FG diets had greater ruminal propionate, lower acetate:propionate ratio, and lower pH. Feeding NS diets increased milk and protein yields and feeding finely ground corn increased ruminal propionate concentration.

Differences in activity of hepatic microsomal triglyceride transfer protein among species

Five sows, five cows, five hens, six guinea pigs, six rabbits, and six rats were used in a study to determine if hepatic microsomal triglyceride transfer protein activity differed among species that varied in site of fatty acid synthesis and rate of hepatic triglyceride export. No differences in plasma nonesterified fatty acids were seen among species. Plasma concentrations of glucose were highest in the hen, intermediate in the rat, guinea pig, and rabbit and lowest in the sow and cow. Liver triglyceride was low in all species with the only significant difference being between the hen and the guinea pig (4.7 and 1.1%, DM basis, respectively). No microsomal triglyceride transfer protein activity was found in muscle. The cow, rat, and guinea pig had the lowest levels and the hen and rabbit the highest levels of duodenal microsomal triglyceride transfer protein activity. Hepatic microsomal triglyceride transfer protein activity was significantly higher in the sow than the other species. Hepatic microsomal triglyceride transfer protein activity was 1.51, 1.63, 2.36, 2.72, 2.95, and 6.70 nmole triolein transferred/h/mg microsomal protein for the guinea pig, rabbit, cow, rat, hen, and sow, respectively. Microsomal triglyceride transfer protein activity in duodenal tissue was 18.0, 18.6, 19.2, 33.4, 113, and 161% of hepatic microsomal triglyceride transfer protein activity for the sow, cow, rat, guinea pig, hen, and rabbit, respectively. Hepatic microsomal triglyceride transfer protein activity scaled to liver weight and metabolic body size was 2.69, 3.36, 4.58, 5.83, 7.49, and 22.3 nmole triolein transferred in the liver/min/kg body weight0.75 for the rabbit, guinea pig, rat, hen, cow, and sow, respectively. There was little relationship between previously published rates for triglyceride export and hepatic microsomal triglyceride transfer protein activity measured in this experiment.