R.D. Shaver

Effect of cereal grain type and corn grain harvesting and processing methods on intake, digestion, and milk production by dairy cows through a meta-analysis.

A meta-analysis was performed to determine the influence of cereal grain type and corn grain harvesting and processing methods, dietary starch, rumen-digestible starch, and forage NDF concentrations on intake, digestion, and lactation performance by dairy cows using a data set comprising 414 treatment means from 102 peer-reviewed journal reports from 2000 to 2011. Categories for corn processing were dry ground, cracked or rolled corn (DRY), high-moisture shelled or ear corn (ENS), and steam-flaked or -rolled corn (STM); categories for kernel mean particle size were 500 to 1,000, 1,000 to 1,500, 1,500 to 2,000, 3,000 to 3,500, and 3,500 to 4,000 µm for dry corn and <2,000 and ≥2,000 µm for ensiled corn. Dietary starch and forage NDF concentrations were used as continuous variables. Data were analyzed using PROC MIXED in SAS (SAS Institute Inc., Cary, NC), with treatment as fixed and trial as random effects. Total-tract starch digestibility was reduced and milk fat content was greater for DRY compared with ENS or STM. Total-tract digestibility of dietary starch was reduced for both DRY and ENS as particle size increased. Increased dietary starch concentrations increased milk yield and protein content, but decreased ruminal and total-tract NDF digestibilities and milk fat content. Dry matter intake, total-tract starch digestibility, and milk protein concentration decreased as forage NDF in the diet increased. Total-tract starch digestibility was positively related to ruminal (percentage of starch intake) and postruminal (percentage of duodenal flow) starch digestibilities.

Influence of ensiling time and inoculation on alteration of the starch-protein matrix in high-moisture corn

The fates of hydrophobic zein proteins, which encapsulate corn starch to create vitreous endosperm, have not been investigated in high-moisture corn (HMC). To assess influences of ensiling time and inoculation on zein proteins in HMC, quadruplicate samples of 2 random corn hybrids (A and B), containing 25.7 and 29.3% moisture, were ground, inoculated with (I) or without 600,000 cfu/g of Lactobacillus buchneri 40788 (Lallemand Animal Nutrition, Milwaukee, WI), and ensiled for 0, 15, 30, 60, 120, and 240 d. Nutrient composition [crude protein (CP), starch, acid detergent fiber, and neutral detergent fiber], fermentation (pH, lactate, and acetate), and protein degradation markers (buffer-soluble CP, isopropanol-soluble CP, and NH(3)-N) were evaluated. At 0 and 240 d, α, γ, δ, and β zein subunits were profiled using HPLC. Data were evaluated as a split-split plot using the PROC MIXED procedures of SAS. Ensiling time and inoculation decreased pH, and altered lactate and acetate contents of HMC. Lactate and acetate contents of A, AI, B, and BI at 240 d were 0.40, 0.32, 1.11, 0.73, and 0, 0.35, 0.30, and 0.87% of DM, respectively. Buffer-soluble CP in HMC increased from 1.5 to 2.0% of DM at 0 d to >4.0% of DM at 240 d. Inoculation had no effect on buffer-soluble CP but increased NH(3)-N content of HMC. Corn A contained more isopropanol-soluble CP than did corn B and peak areas for 6 α, and all γ and δ zein regions were greater for corn A. Ensiling (0 vs. 240 d) decreased all zein subunits with the exception of 2 α and 1 δ subunit. Ensiling decreased (42.2-73.2%) γ zeins, which are primarily responsible for cross-linking in the starch-protein matrix. Despite altering lactate and acetate contents, inoculation had no effect on degrading hydrophobic zein proteins in HMC. Data suggest that hydrophobic zein proteins in the starch-protein matrix of HMC are degraded by proteolytic activity over an extended ensiling time.

Stage of maturity, processing, and hybrid effects on ruminal in situ disappearance of whole-plant corn silage

Five in situ trials with whole-plant corn silage (WPCS) were conducted in two ruminally-cannulated Holstein cows to determine 24-h ruminal disappearance of dry matter (DM), starch, and neutral detergent fiber (NDF). In Trial 1, the effect of maturity of WPCS on ruminal nutrient disappearance was evaluated. Treatments were early dent (ED), 1/4 milk-line (1/4 ML), 2/3 milk-line (2/3 ML), and black-layer (BL) stage of maturity. Ruminal disappearance of DM was lower (p<0.01) for BL (474 g/kg) than ED (547 g/kg), 1/4 ML (579 g/kg), or 2/3 ML (530 g/kg). Ruminal starch disappearance was lower (p<0.01) for BL (862 g/kg) than ED, 1/4 ML, or 2/3 ML which averaged 950 g/kg. In Trial 2, the effect of mechanical processing of mature and immature WPCS and stover silage at harvest was evaluated. Processing increased (p<0.01) ruminal starch disappearance for both immature (844 vs. 664 g/kg) and mature (790 vs. 525 g/kg) WPCS. In Trial 3, two WPCS hybrids (grain vs. leafy) at two plant populations (low=59,000 or high=79,000 plants/ha) were evaluated. Type of hybrid or plant population did not affect DM or NDF disappearance. However, starch disappearance was higher (p<0.01) for the leafy hybrid (872 vs. 731 g/kg). In Trial 4, brown-midrib (BMR) corn harvested as WPCS was evaluated for ruminal nutrient disappearance versus a conventional grain hybrid. Ruminal DM (602 vs. 561 g/kg) and NDF (326 vs. 220 g/kg) disappearance were higher (p<0.01) for BMR. In Trial 5, ruminal nutrient disappearance of high- and low-NDF corn silage hybrids were compared. Ruminal DM (662 vs. 620 g/kg) and starch (987 vs. 950 g/kg) disappearance were higher, but NDF disappearance was lower (176 vs. 225 g/kg) for the low-NDF hybrid (p<0.001). In summary, delaying silage harvest to BL reduced ruminal nutrient disappearance. Mechanical processing increased ruminal disappearance of WPCS, primarily through greater ruminal starch disappearance. Ruminal starch and NDF disappearance were higher for leafy and BMR hybrids, respectively, relative to a conventional grain hybrid. Ruminal DM disappearance was increased for a low-NDF hybrid, but effects were positive for starch and negative for NDF disappearance.

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.

In situ dry matter, crude protein, and starch degradabilities of selected grains and by-product feeds

In situ degradabilities were determined for some commonly used grains and by-product feeds in dairy cattle rations. Ingredients evaluated were barley, shelled corn, soybean meal, brewers dried grains, corn gluten feed, distillers dried grains, soybean hulls, and wheat middlings. In situ studies were conducted in three rumen-fistulated Holstein cows. Cows were fed a total mixed rations containing 55% alfalfa silage and 45% shelled corn-based concentrate (dry matter basis). Dacron bags containing 6 g (as fed basis) of each feed were immersed in duplicate at each time point in the ventral rumen of each cow for 2, 4, 6, 12, 24, 48, and 72 h. Ruminal availabilities of dry matter, crude protein, and starch calculated as a percentage of nutrient were ranked from high to low: dry matter: barley (67.3%), soybean meal (63.9%), distillers dried grains (58.3%), corn gluten feed (56.9%), wheat middlings (54.6%), shelled corn (51.1%), soybean hulls (48.8%), and brewers dried grains (38.3%); crude protein: wheat middlings (71.9%), corn gluten feed (70.3%), soybean meal (62.9%), barley (60.0%), soybean hulls (58.2%), brewers dried grains (48.9%), shelled corn (40.0%), and distillers dried grains (39.6%); starch: wheat middlings (88%), distillers dried grains (85.5%), soybean meal (81.8%), barley (80.5%), brewers dried grains (76.0%), corn gluten feed (70.6%), soybean hulls (66.4%), and shelled corn (56.5%). Grains and by-product feeds vary widely in their ruminal availability. This study provides estimates of kinetics of ruminal degradation of feeds for use in dynamic models of protein and carbohydrate digestion.

Estimating silage energy value and milk yield to rank corn hybrids

This paper provides a revised summative energy equation and applies it to estimate the energy value of corn (Zea mays) silage. Estimating the energy value of corn silage is important, because energy is the primary nutrient contributed by corn silage to dairy cattle rations. Estimated energy intake from corn silage was used to estimate milk yield from corn silage by dairy cows. The milk yield estimate was used to rank corn hybrids in silage evaluation and breeding programs. The revised (MILK2000) forage quality (milk Mg −1 ) and yield (milk ha −1 ) indices were evaluated relative to MILK1995 indices in corn silage hybrid performance trials. A previously published summative energy equation (Weiss, 1996), with crude protein, fat, non-fiber carbohydrate (NFC), and neutral detergent fiber (NDF) fractions and corresponding digestibility coefficients, was adapted for corn silage as follows: the crude protein and fat fractions were not altered, the NFC fraction with constant digestibility was replaced with starch and non-starch NFC fractions, the starch digestibility coefficient was varied in relationship to whole-plant dry matter (DM) concentration and kernel processing, and the NDF digestibility coefficient based on lignin concentration was replaced by a 48 h or maintenance intake in vitro measurement of NDF digestibility (NDFD). Our summative approach integrates known differences in starch digestibility, as affected by whole-plant DM concentration and kernel processing, and NDFD into estimates of the energy value of corn silage. It also provides a framework for the future incorporation of laboratory measures of starch digestibility into estimates of the energy value of corn silage. For the MILK2000 model, we used our net energy for lactation estimates along with DM intake estimated from NDF concentration and NDFD to Abbreviations:ADF, acid detergent fiber; BW, body weight; CP, crude protein; DM, dry matter; DMI, dry matter intake; FA, fatty acids; IVTD, in vitro true digestibility; MILK2000, revised milk Mg −1 and milk ha −1 indices; MILK1995, original milk Mg −1 and milk ha −1 indices; N, nitrogen; NDF, neutral detergent fiber; NDFD, in vitro NDF digestibility; NEL, net energy of lactation; NFC, non-fiber carbohydrate; NIRS, near infra-red reflectance spectroscopy ∗

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.

Effect of a mixture of supplemental dietary plant essential oils on performance of periparturient and early lactation dairy cows

Plant essential plant oils (EO) are volatile aromatic compounds with antimicrobial activity that can alter ruminal fermentation when used as dietary supplements. A feeding trial was conducted to determine the effects of dietary supplementation of periparturient and early lactation dairy cows with a specific mixture of EO. Forty multiparous Holstein cows were randomly assigned to either control (C) or EO-supplemented (1.2 g/cow per day) total mixed rations (TMR). Feeding of treatment diets commenced 3 wk before the expected calving date and continued through 15 wk in lactation. The prepartum TMR contained 70% forage [70% corn silage, 15% alfalfa silage, and 15% wheat straw; dry matter (DM) basis]. The lactation TMR contained 50% forage (60% corn silage, 33% alfalfa silage, 7% alfalfa hay; DM basis). Prepartum and lactation TMR were formulated to contain 12 and 17% CP (DM basis), respectively. There were no differences between treatments for prepartum DM intake (DMI), but DMI was 1.8 kg/d less for EO than C on average across the 15-wk lactation trial. Plasma concentrations of glucose, nonesterified fatty acids, beta-hydroxybutyrate, and urea-N on samples collected -21, -14, -7, -1, 1, 8, 15, 22, and 29 d relative to calving were unaffected by treatment. There were no differences between treatments for actual or fat-corrected milk yields on average across the 15-wk lactation trial. Milk protein content was 0.15% units less for EO than C. Feed efficiency (kg of milk per kg of DMI) tended to be greater for EO than C on average and was greater during wk 8 to 14 of lactation. Prepartum and lactation body weight and condition score measurements were unaffected by treatment. There was no benefit to EO in prepartum dairy cows. Dietary supplementation with EO reduced DMI in early lactation dairy cows with no effect on milk yield.

Relationships between fertility and postpartum changes in body condition and body weight in lactating dairy cows

The relationship between energy status and fertility in dairy cattle was retrospectively analyzed by comparing fertility with body condition score (BCS) near artificial insemination (AI; experiment 1), early postpartum changes in BCS (experiment 2), and postpartum changes in body weight (BW; experiment 3). To reduce the effect of cyclicity status, all cows were synchronized with Double-Ovsynch protocol before timed AI. In experiment 1, BCS of lactating dairy cows (n = 1,103) was evaluated near AI. Most cows (93%) were cycling at initiation of the breeding Ovsynch protocol (first GnRH injection). A lower percentage pregnant to AI (P/AI) was found in cows with lower (≤ 2.50) versus higher (≥ 2.75) BCS (40.4 vs. 49.2%). In experiment 2, lactating dairy cows on 2 commercial dairies (n = 1,887) were divided by BCS change from calving until the third week postpartum. Overall, P/AI at 70-d pregnancy diagnosis differed dramatically by BCS change and was least for cows that lost BCS, intermediate for cows that maintained BCS, and greatest for cows that gained BCS [22.8% (180/789), 36.0% (243/675), and 78.3% (331/423), respectively]. Surprisingly, a difference existed between farms with BCS change dramatically affecting P/AI on one farm and no effect on the other farm. In experiment 3, lactating dairy cows (n = 71) had BW measured weekly from the first to ninth week postpartum and then had superovulation induced using a modified Double-Ovsynch protocol. Cows were divided into quartiles (Q) by percentage of BW change (Q1 = least change; Q4 = most change) from calving until the third week postpartum. No effect was detected of quartile on number of ovulations, total embryos collected, or percentage of oocytes that were fertilized; however, the percentage of fertilized oocytes that were transferable embryos was greater for cows in Q1, Q2, and Q3 than Q4 (83.8, 75.2, 82.6, and 53.2%, respectively). In addition, percentage of degenerated embryos was least for cows in Q1, Q2, and Q3 and greatest for Q4 (9.6, 14.5, 12.6, and 35.2% respectively). In conclusion, for cows synchronized with a Double-Ovsynch protocol, an effect of low BCS (≤ 2.50) near AI on fertility was detected, but change in BCS during the first 3 wk postpartum had a more profound effect on P/AI to first timed AI. This effect could be partially explained by the reduction in embryo quality and increase in degenerate embryos byd 7 after AI in cows that lost more BW from the first to third week postpartum.

Effect of dietary organic zinc, manganese, copper, and cobalt supplementation on milk production, follicular growth, embryo quality, and tissue mineral concentrations in dairy cows

This study evaluated potential effects of organic trace mineral supplementation on reproductive measures in lactating dairy cows. Cows were blocked by breed and randomly assigned at dry-off to receive inorganic trace mineral supplementation (control; n = 32) or to have a portion of supplemental inorganic Zn, Cu, Mn, and Co replaced with an equivalent amount of the organic forms of these minerals (treatment; n = 31). Trace minerals were provided through control or treatment premixes fed at 100 g·cow(-1)·d(-1). Premixes were fed to dry cows (range = 40 to 72 d before calving) in 1.8 kg·cow(-1)·d(-1) concentrate pellets through a computer feeder to provide 40, 26, 70, and 100% of supplemented Zn, Mn, Cu, and Co, respectively, and to lactating cows (range = 69 to 116 d after calving) in a total mixed ration to provide 22, 14, 40, and 100% of supplemented Zn, Mn, Cu, and Co, respectively. Treatment increased milk production at wk 14 (P = 0.047) postcalving, milk urea N content (P = 0.039), and BW loss from calving to 1 mo postcalving (P = 0.040), and decreased milk fat percentage (P = 0.045) and BCS (P = 0.048). Treatment tended to increase milk production at wk 13 (P = 0.089) postcalving and endometrial tissue concentrations of Fe (P = 0.070), BW at mo 1 (P = 0.056), and milk protein percentage (P = 0.064). Treatment did not affect (P > 0.1) DMI, health events, first-wave follicular dynamics, first cycle luteal measures, embryo quality, liver trace mineral concentrations, or luteal trace mineral concentrations. Cows with a rectal temperature ≥39°C at the time of AI had a smaller percentage of fertilized entities (P < 0.001). However, of the entities that were fertilized, the percentage of viable embryos, embryo quality, accessory sperm number, and embryo cell number were not affected (P > 0.1) by treatment. We conclude that replacing a portion of inorganic supplemental trace minerals with an equivalent amount of these organic trace minerals (Zn, Mn, Cu, and Co) increased milk production in mid-lactation, but did not affect postpartum follicular dynamics, embryo quality, or liver and luteal trace mineral concentrations.