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Biomedical subjects

R D Shaver

Publications and source records attributed to R D Shaver.

At least 37 records · Page 2Linked to original sources
PubMed1997

Comparison of in situ and in vitro techniques for measuring ruminal degradation of animal by-product proteins.

Ruminally undegraded protein (RUP) values of blood meal (n = 2), hydrolyzed feather meal (n = 2), fish meal (n = 2), meat and bone meal, and soybean meal were estimated using an in situ method, an inhibitor in vitro method, and an inhibitor in vitro technique applying Michaelis-Menten saturation kinetics. Degradation rates for in situ and inhibitor in vitro methods were calculated by regression of the natural log of the proportion of crude protein (CP) remaining undegraded versus time. Nonlinear regression analysis of the integrated Michaelis-Menten equation was used to determine maximum velocity, the Michaelis constant, and degradation rate (the ratio of maximum velocity to the Michaelis constant). A ruminal passage rate of 0.06/h was assumed in the calculation of RUP. The in situ and inhibitor in vitro techniques yielded similar estimates of ruminal degradation. Mean RUP estimated for soybean meal, blood meal, hydrolyzed feather meal, fish meal, and meat and bone meal were, respectively, 28.6, 86.0, 77.4, 52.9, and 52.6% of CP by the in situ method and 26.4, 86.1, 76.0, 59.6, and 49.5% of CP by the inhibitor in vitro technique. The Michaelis-Menten inhibitor in vitro technique yielded more rapid CP degradation rates and decreased estimates of RUP. The inhibitor in vitro method required less time and labor than did the other two techniques to estimate the RUP values of animal by-product proteins. Results from in vitro incubations with pepsin.HCl suggested that low postruminal digestibility of hydrolyzed feather meal may impair its value as a source of RUP.

Animals↗
PubMed1996

Use of lactation curves for analysis of milk production data.

Nonlinear equations were compared with categorical analysis to account for DIM effects on milk production. Five different models for lactation curves were evaluated. Derived from a multiphasic lactation curve, the selected lactation curve appeared to result in random residuals and performed more consistently than the multiphasic curve. Residuals from the fitting of lactation curves were then used for split-plot analysis (continuous model) to estimate treatment effects. Statistical performance of this model was compared with split-plot analysis based on a discrete model with regularly spaced intervals to account for DIM effects (discrete model). The fitting of lactation curves accounted for herd, lactation number, and interaction effects of herd and lactation number and accounted for 34.1 and 44.3% of variance among cows for primiparous and multiparous cows, respectively. The continuous model detected interactions of genetic and management factors with treatment of multiparous cows that were not detected by the discrete model. No statistically significant differences were detected between the two modeling approaches. The continuous model appeared to violate fewer assumptions regarding data distribution than did the discrete model, which reduced the risk of introducing bias during the estimation of treatment effects. The continuous model seemed to be more sensitive to subtle interactions of treatment and other factors.

Animals↗
PubMed1995

Effects of rumen-inert fat on lactation, reproduction, and health of high producing Holstein herds.

Two hundred twenty of 443 cows freshening between June 1989 and March 1990 in five commercial Holstein herds were fed .45 kg/d of rumen-inert fat from calving until 200 DIM. Control diets were fed as TMR and contained, on average, 3.7 to 4.8% supplemental fat (DM basis). Test herds had rolling herd averages of 9300 to 13,250 kg of milk. Production of 4% FCM and milk increased 1.01 (3.3%) and 1.50 kg/d (4.6%), respectively, for primiparous cows fed additional fat. Multiparous cows from four herds demonstrated no response; multiparous cows in one herd increased production of 4% FCM by 2.88 kg/d (8.2%), milk by 2.45 kg/d (6.4%), and milk fat by .14kg/d (10.6%) in response to additional fat. An explanation of response differences among herd for multiparous cows was not possible. For primiparous and multiparous cows, increased genetic potential increased treatment response. Increased body condition score at calving influenced treatment response of multiparous cows. Thinner cows produced more milk and less milk fat in response to additional dietary fat than did fatter cows. Most reproductive indices were unaffected by treatment. Cows receiving additional fat had lower, but nonsignificantly lower, incidences of most health disorders. Responses to rumen-inert fat by cows receiving high concentrations of dietary fat were marginal and were affected by body condition score at calving and by genetic potential.

Animal Nutritional Physiological Phenomena↗
PubMed1994

Influence of sugary-Brawn2 or dent corn at two forage levels on intake, digestion, and milk production by dairy cows.

Sugary-Brawn2 (su-Bn2) corn endosperm contains higher concentrations of watersoluble polysaccharides than dent corn. Eight multiparous Holstein cows averaging 48 d in milk and 667 kg BW at trial initiation were in a replicated 4 x 4 Latin square design with 28-d periods. Only cows in one square were ruminally cannulated. Treatments were su-Bn2 or dent corn and 45 or 60% of ration DM as alfalfa silage arranged as a 2 x 2 factorial within each square. Diets, formulated to contain 19% CP, were fed as total mixed rations twice daily. Intake of DM and milk yield averaged 26.8 and 39.9 kg/d, respectively, and were not affected by treatment (P > .10). Sugary-Brawn2 corn decreased milkfat percentage (3.27 vs 3.45%), particularly for the low-forage diet (3.15 vs 3.40%). Milk protein percentage was higher (3.15 vs 3.10%) for low-forage diets but was not affected (P > .10) by corn type. Ruminal pH was lower for low-forage diets. Feeding su-Bn2 corn decreased ruminal pH only at 4 h after feeding. Total VFA in ruminal fluid (millimolar) 6 h after feeding were higher, whereas acetate molar percentage and acetate:propionate ratio were lower for su-Bn2 corn. Ruminal in situ evaluation of su-Bn2 and dent corn revealed a larger soluble fraction, a faster rate of degradation, and higher availabilities of both DM and starch for su-Bn2 corn. Ruminal in situ rate of degradation and availability of alfalfa hay DM were reduced by su-Bn2 corn. Total tract apparent digestibilities of DM, CP, and starch were greater for su-Bn2 diets.(ABSTRACT TRUNCATED AT 250 WORDS)

Alleles↗
PubMed1994

Impact of nonfiber carbohydrate on intake, digestion, and milk production by dairy cows.

Four concentrations of dietary nonfiber carbohydrate (42, 36, 30, and 24%) were evaluated using eight multiparous Holstein cows (662 kg of BW; 63 DIM) in replicated 4 x 4 Latin squares with 28-d periods. Shelled corn and soybean meal were partially replaced with wheat middlings, dried brewers grains, and soy hulls to formulate 36, 30, and 24% nonfiber carbohydrate diets. Decreasing dietary nonfiber carbohydrate decreased DMI, did not affect actual or fat-corrected milk production, increased milk fat percentage, and decreased milk protein percentage and production. Apparent total tract DM and OM digestibilities were highest for 36% and lowest for 24% nonfiber carbohydrate diets. Digestibility of NDF was lowest for the 42% nonfiber carbohydrate diet. Ruminal pH and acetate:propionate increased, and total VFA concentrations decreased, as dietary nonfiber carbohydrate decreased. Ruminal degradation of alfalfa hay DM and NDF were higher for low nonfiber carbohydrate diets. Significant depression of DMI (.9 to 1.8 kg/d) coincided with dietary nonfiber carbohydrate concentration at or below 30%. Results indicate that diets for cows producing 40 kg/d should contain more than 30% nonfiber carbohydrate and suggest little benefit of 42 over 36% nonfiber carbohydrate diets.

Animals↗
PubMed1994

Lactational responses to ruminally undegradable protein by dairy cows fed diets based on alfalfa silage.

Lactational responses to protein supplementation of diets containing 60% of DM as alfalfa silage were evaluated. Sixty muliparous Holstein cows were fed a covariant diet for the first 3 wk postpartum, blocked by calving date, and randomly assigned for 14 wk to one of six isonitrogenous (19.4% CP) diets. Diets were formulated with soybean meal, a blend of animal by-products, or both, and contained 5.0, 5.6, 5.6, 6.2, 6.1, and 6.8% ruminally undegradable protein (DM basis). Percentage of ruminally undegradable protein or source of supplemental protein did not affect 3.5% FCM (39.4 kg/d), milk fat yield (1.38 kg/d), milk protein percentage (2.83%), milk urea (7.66 mM), or plasma urea (8.91 mM). However, cows fed diets supplemented with soybean meal had higher DMI (26.2 vs. 24.7 kg/d), milk yields (40.4 vs. 39.1 kg/d), and milk protein (1.15 vs. 1.09 kg/d) yields, but lower milk fat concentration (3.42 vs. 3.53%) and body condition score (2.85 vs. 2.93) than cows fed diets containing a blend of animal by-products. The lack of response to ruminally undegradable protein was partially caused by higher than predicted DMI (5 to 15% above NRC predictions); all diets provided at least 1.3 kg of ruminally undegradable protein, and there was no beneficial effect from ruminally undegradable protein intake increases to 1.6 kg/d.

Ammonia↗
PubMed1993

Effect of nonfiber carbohydrate level and Aspergillus oryzae fermentation extract on intake, digestion, and milk production in lactating dairy cows.

Eight multiparous, ruminally cannulated Holstein cows averaging 40 d in milk and 575 kg BW at the start of trial were in a replicated 4 x 4 Latin square arrangement (28-d periods) to determine the effects of dietary nonfiber carbohydrate (NFC) level and Aspergillus oryzae fermentation extract (AO) on intake, milk production, and nutrient digestibility. Treatments were 42 or 35% NFC and 0 or 3 g of AO per day arranged as a 2 x 2 factorial. Diets formulated to contain 21% NDF from alfalfa silage (48.4% of ration DM) and 18.5% CP were fed as total mixed rations twice daily. Alteration of dietary NFC level was by partial replacement of shelled corn and soybean meal with wheat middlings and brewers dried grains. Intake of NDF was higher (1.49 vs 1.22% of BW) for 35 than for 42% NFC diets, but DMI was lower (24.1 vs 24.9 kg/d). Milkfat percentage, ruminal pH, ammonia, acetate (moles/100 moles), and total tract digestibility of fiber were higher for 35% NFC diets; however, ruminal disappearance of DM, CP, and NDF from Dacron bags containing alfalfa hay was not affected (P > .10) by NFC level. Supplementation with AO did not affect (P > .10) DMI, milk yield, or nutrient digestion. Partial replacement of corn with high-fiber byproducts to lower dietary NFC level and correspondingly increase NDF level increased NDF intake but effected only a small change in DMI. Reducing dietary NFC level improved ruminal fermentation and milkfat percentage without significantly affecting milk yield.

Ammonia↗
PubMed1993

Carbohydrate and Aspergillus oryzae effects on intake, digestion, and milk production by dairy cows.

Six multiparous, ruminally cannulated Holstein cows (46 DIM, 584 kg of BW) and 6 primiparous Holstein cows (35 DIM, 506 kg of BW) were used in two 6 x 6 Latin squares with 21-d periods to examine the effects of level of non-fiber carbohydrate, source of fibrous carbohydrate, and Aspergillus oryzae fermentation extract on intake, digestion, and milk production. Treatments were 42 and 36% non-fiber carbohydrate; shelled corn and soybean meal were replaced partially by beet pulp and dried brewers grains or soy hulls and dried brewers grains in 36% non-fiber carbohydrate diets. These three diets then were supplemented with 0 or 3 g/d of A. oryzae. Milk production and composition and DMI were not significantly affected by level or source of carbohydrate, although intake of NDF was significantly higher for 36% non-fiber carbohydrate diets. Total tract apparent digestibilities of ADF and NDF were higher for 36% non-fiber carbohydrate diets. Supplementation with A. oryzae did not significantly affect DMI, milk production, or total tract apparent digestibilities; however, milk fat content was decreased. Partial replacement of corn with fibrous carbohydrate sources, beet pulp and soy hulls, did not adversely affect intake or milk production in early lactation cows fed alfalfa silage-based diets.

Animal Feed↗
PubMed1993

In situ dry matter, protein, and fiber degradation of perennial forages.

Eight forages (alfalfa, birdsfoot trefoil, red clover, bromegrass, orchardgrass, perennial ryegrass, quackgrass, and timothy) at three maturities were evaluated for ruminal DM, CP, and NDF degradation kinetics. Duplicate dacron bags were incubated for 0, 3, 6, 10, 13, 25, 48, and 72 h in two late lactation Holstein cows fitted with ruminal cannulas over eight experimental periods. Species and maturity effects were observed for soluble, slow, and undegraded fractions; degradation rate; and ruminally degradable DM, CP, and NDF. Significant species by maturity interactions also were evident for fractions and ruminal degradabilities of DM, CP, and NDF. Legumes exhibited more extensive ruminal DM degradation than did grasses. No clear trends were evident in rate of ruminal CP degradation between legumes and grasses. Mature grasses were lowest in ruminally degradable CP. Legumes exhibited a higher undegraded fraction and faster degradation rate of slowly degraded NDF fractions, resulting in similar ruminally degraded NDF for legumes and grasses. Extensive differences in ruminal degradation kinetics existed between perennial legume and grass species and maturities. Species by maturity interactions were diverse, making categorization of degradation characteristics of legumes and grasses difficult.

Animal Feed↗
PubMed1991

Feeding supplemental fat and undegraded intake protein to early lactation dairy cows.

Forty-eight Holstein cows (16 primiparous) were fed alfalfa silage-based TMR containing 18% CP with 33 or 36% of the CP as undegraded intake protein and with 0 or 2.8% supplemental fat (DM basis). Expeller soybean meal replaced solvent soybean meal to vary undegraded intake protein, and sodium alginate-treated tallow was used as the fat source. A standard diet containing solvent soybean meal without fat was fed during the first 21 d postpartum for covariate adjustment of milk production. A continuous lactation design with 2 x 2 factorial arrangement of treatments was used with supplemental fat and undegraded intake protein as main effects. Feeding supplemental fat increased actual milk (32.9 vs. 31.7 kg/d) but decreased milk protein concentration. Cows fed supplemental fat also had higher BW, and weight gain was significant with time. Increasing undegraded intake protein did not affect milk yield, composition, or component yield. There were no significant interactions between supplemental fat and undegraded intake protein on milk yield or composition. Milk fatty acid composition was not altered by addition of undegraded intake protein, but C6 to C14 fatty acids were reduced by adding supplemental fat. Results do not support the strategy of increasing levels of undegraded intake protein when supplemental fat is fed. Variation in undegraded intake protein content of feed-stuffs appears to be of more importance in ration formulation than interactions between supplemental fat and protein.

Animal Feed↗
PubMed1990

Response to recombinant bovine somatotropin in dairy cows with different genetic merit for milk production.

Thirty-nine multiparous cows obtained from two genetic lines were utilized to determine the effect of genetic merit on lactation response to long-term administration of recombinant bST. Cow index ranged from -70 to 456 (mean = 183) and -494 to -88 (mean = -288) kg milk for high and low genetic groups, respectively. Cows were blocked by calving date and randomly assigned to treatment within genetic group. Treatments were 0, 10.3, 20.6, and 30.9 mg somatotropin injected daily from wk 14 through 44 postpartum. Cows were fed one of two total mixed rations. Diet 1 (NE1 = 1.65 Mcal/kg, CP = 18%, and ADF = 22%) was fed from start of lactation to at least 4 wk after initiation of treatment. Cows were switched to diet 2 (NE1 = 1.56 Mcal/kg, CP = 16%, and ADF = 27%) when milk output fell below 25 kg/d. Forty-four week lactation yields were 9800 and 9447 kg milk; 364 and 354 kg fat; and 322 and 309 kg protein for high and low genetic groups, respectively. Milk, milk fat, or protein yield due to somatotropin did not differ between genetic groups. Increasing dosage of bST increased milk, 4% FCM, fat, and protein yields in a linear fashion. Percentages of fat and protein of milk were similar for all treatment groups. Body weight changes were not significantly different among treatments, but condition score changes decreased linearly with increasing dose of bST. Long-term treatment with recombinant bST had no apparent effect on incidence of health problems or reproduction.

Animals↗
PubMed1990

Lactational evaluation of recombinant bovine somatotropin with corn and barley diets.

Forty-eight Holstein cows were randomly assigned to receive diets containing corn or barley as the primary energy concentrate from wk 4 through 44 postpartum. During wk 14, cows from each grain source group were randomly assigned to receive 0 (control), 10.3, 20.6, and 30.9 mg/cow per d of recombinant bST injected wk 15 through 44 postpartum. Grain source exerted no significant effect on production parameters and efficacy of bST, although milk production tended to be higher with corn diets. Milk production (24.2, 29.2, 31.7, and 29.5 kg/d) and 4% FCM (21.9, 26.2, 28.1, and 28.0 kg/d) were higher for cows injected with bST, and DM intakes (20.9, 22.8, 22.0, and 23.3 kg/d) increased slightly. Percentages of milk fat (3.47, 3.28, 3.39, and 3.52) and protein (3.48, 3.44, 3.44, and 3.38) varied. Lactose, SCC, and body weights were similar for bST and dietary treatments. Diet or bST had no detectable affect on health or reproduction. Injection of bST wk 15 through 44 increased milk production 21 to 31% relative to control animals. Limiting bST use to the latter two-thirds of lactation resulted in an 8 to 17% increase in total yield with only a 0 to 5% increase in lactational DM intake.

Animals↗
PubMed1990

Dose response to recombinant bovine somatotropin from weeks 15 to 44 postpartum in lactating dairy cows.

Forty Holstein cows were used in an experiment to determine the response of cows to daily subcutaneous injections of 0, 10.3, 20.6, and 30.9 mg of recombinant bST. Injections began between 98 and 104 d postpartum and continued for 29 wk, up to 70 d prepartum, or a maximum of 400 d postpartum. Increasing recombinant bST increased milk yield and 3.5% FCM yield in a linear fashion and by 5.2 and 5.7 kg/d, respectively. Milk composition was not changed, and DM intake as a percentage of BW increased from 3.39 to 3.80% with increasing (30.9 mg/d) bST. Feed efficiency (3.5% FCM/DM intake) was increased from 1.35 to 1.64 with increasing dose, suggesting improved efficiency of use of DM intake, primarily by dilution of maintenance. Increasing bST reduced BW gain linearly from .46 kg/d for the control to .22 kg/d for the 30.9 mg/d bST. Calf birth weight, weight of cows at calving, and incidence of metabolic diseases during subsequent calving were not affected by bST. Somatotropin treatment resulted in somewhat smaller increased in milk yield than that reported in previous studies. Long-term health effects and effects on reproduction could not be determined from the relatively few cows used in this study.

Animals↗
PubMed1988

Impact of forage fiber content on digestion and digesta passage in lactating dairy cows.

Five Holstein cows (5 wk postpartum) were used in a Latin square design (15-d periods) to determine rumen fill and fractional rates of ruminal digestion and passage. Treatments consisted of prebloom, midbloom, and full bloom alfalfa hay, mature bromegrass hay, and corn silage fed in diets containing forage: concentrate in a 60:40 ratio (DM basis) formulated to be isonitrogenous. Intake of DM averaged 4.0% of body weight for prebloom alfalfa and corn silage. Milk yield and DM intake were lower for full bloom alfalfa and bromegrass than for prebloom alfalfa. Digestibility of organic matter was 7.5 percentage units lower for full bloom than for prebloom alfalfa. Weight of DM in the rumen was higher for midbloom and full bloom alfalfa and bromegrass than with prebloom alfalfa. Ruminal retention time of Yb applied to forage was longer for bromegrass than for prebloom alfalfa. Fractional rates of in situ NDF digestion were slower for full bloom alfalfa and bromegrass than for prebloom alfalfa. Results suggest that the point of limitation of feed intake due to gut fill is dependent on forage quality as well as energy demand of the animal. Dry matter fill of the rumen was more closely related to rates of ruminal digestion and passage than to total tract digestibility or maximum digestibility after lengthy in situ fermentation.

Animal Feed↗
PubMed1988

Influence of feed intake, forage physical form, and forage fiber content on particle size of masticated forage, ruminal digesta, and feces of dairy cows.

Two trials were conducted to determine particle size of masticates, ruminal digesta, and feces of dairy cows. In Trial 1, three Holstein cows with ruminal cannulae were fed prebloom alfalfa hay in long, chopped, or pelleted form in a Latin square design (21-d periods) conducted in early lactation (wk 3 to 11) and again during the dry period to attain high (3.75) and low (1.95% of BW) feed consumption. In trial 2, prebloom, midbloom, and full bloom alfalfa hay, mature bromegrass hay, and corn silage were fed to early lactation (wk 5 to 15) Holsteins in a 5 X 5 Latin square design (15-d periods). All diets (Trials 1 and 2) were formulated to 17% CP and contained forage:grain in a 60:40 ratio (DM basis). Similar particle distributions of digesta from long and chopped hay diets suggest little influence of chopping forage on particle size reduction when high quality forage is fed. The large proportion of DM in the small particle (less than .6 mm) pool in the rumen in both trials suggests that rate of escape of small particles from the rumen is an important factor influencing ruminal retention time. Increased proportion of coarse (greater than or equal to 2.36-mm screen) fecal particles at high intake and with fine grinding appears related to a reduction in chewing per unit feed consumed. Soluble DM and particulate matter passing a .063-mm screen made up a significant portion (30 to 50%) of the total DM sieved from all sampling sites in both trials.

Animal Feed↗
PubMed1984

Dietary choline for the lactating cow: possible effects on milk fat synthesis.

Two experiments with low forage diets tested effects of added dietary choline on milk fat synthesis. In Experiment 1, 18 Holstein cows were in a 12-wk trial. Choline (0, 1.5, and 3 g/kg) was added to the concentrate portion of a 70% concentrate, 30% corn silage diet (dry matter). Treatments were applied in a switchback design with 4-wk experimental periods. Highest choline increased milk fat by .34 percentage units and fat-corrected milk by 2 kg per day over controls. Rumen pH and volatile fatty acids were similar among treatments. Free fatty acids of blood serum were reduced 3.0 mg/100 ml by 3 g/kg choline. In Experiment 2 with four mature Holsteins, choline was added (0, 2, 4, and 6 g/kg concentrate) in 25% corn silage and 75% concentrate diets. Treatments were applied in a 4 x 4 Latin square design. Addition of 4 g/kg choline resulted in 3.7 kg/day and .77 percentage unit increases of fat-corrected milk and milk fat percent, respectively, whereas fat-corrected milk and milk fat percent at 6 g/kg were only slightly higher than controls. We hypothesized that choline aided transport of mobilized free fatty acids from adipose tissue through the liver to the mammary gland.

Animals↗
PubMed1984

Effects of silage pH on voluntary intake of corn silage.

We evaluated effects of silage pH on corn silage intake. Sixteen Holstein heifers (292 kg) were fed control corn silage during a 2-wk preliminary period. This was followed by an 8-wk experimental period in which animals were fed silage neutralized with 0, 2, 4, or 6% sodium bicarbonate (dry matter) added prior to feeding with corresponding pH's 3.72, 4.46, 5.62, and 8.05. Organic matter intake was increased 1.0 and 1.2 kg/day by addition of 2 and 4% sodium bicarbonate versus controls whereas 6% sodium bicarbonate reduced intake .7 kg/day. An equation developed to predict organic matter intake from silage pH was: Y = 3.20 + 3.92 (pH) -.35 (pH)2 with coefficient of determination .66. This equation predicted maximum organic matter intake at pH 5.6. It appears that silage pH is a factor that affects voluntary consumption of corn silage and that pH 5 to 6 is optimum, whereas silage pH above and below may reduce intake.

Animal Feed↗