Biomedical subjects

W N Garrett

Publications and source records attributed to W N Garrett.

At least 19 recordsLinked to original sources

PubMed1993

Influence of level of urea and method of supplementation on characteristics of digestion of high-fiber diets by sheep.

Effects of level and method of urea supplementation of N utilization and characteristics of digestion of a N-deficient (.85% N), citrus pulp-based diet were evaluated in a 4 x 4 Latin square design experiment, using four ruminally and intestinally cannulated crossbred (D'man x Sardi) rams. Two levels of urea (15.1 and 8.8 g/d, providing total N intakes of 12.0 and 9.1 g/d, respectively) and two methods of supplementation (urea mixed with the diet or continuously infused in the rumen) were compared in a 2 x 2 factorial arrangement of treatments. Ruminal pH varied between 6.2 and 7.0 across treatments and tended (P > .10) to be lower in animals receiving urea infusion. Ruminal ammonia concentrations were lower (P < .01) and more stable with urea infusion than with urea feeding. Ruminal VFA concentrations and profiles were unaffected (P > .10) by treatments. Site and extent of OM and fiber digestion were not influenced (P > .10) by either level of urea in the diet or method of supplementation. Average ruminal OM and ADF digestion were 53.1 and 64.5%, respectively. Total tract digestion values averaged 75.9 and 73.5%, respectively. With the exception of N efficiency (duodenal nonammonia N/total N intake) that was 31% lower (P < .10) for the high- than for the low-urea treatment, there were no treatment responses or interactions (P > .10) on characteristics of N utilization. Microbial N flow to the small intestine averaged (across treatments) 9.0 g/d and constituted 87% of the nonammonia N leaving the abomasum.(ABSTRACT TRUNCATED AT 250 WORDS)

Ammonia↗

PubMed1993

Effect of source of supplemental nitrogen on the utilization of citrus pulp-based diets by sheep.

Two trials were conducted to examine the influence of N enrichment of dried citrus pulp (DCP) through ammoniation vs urea supplementation on digestion and feeding value of a DCP-based diet for sheep. Treatments were 1) ammoniation of DCP with urea (CP-U), 2) ammoniation with ammonium hydroxide (CP-A), 3) supplementation with urea, and 4) supplementation with horse bean (HB). Diets were isonitrogenous (1.8% N). In Trial 1, treatment effects on characteristics of digestion were evaluated in a 4 x 4 Latin square experiment using four rams. Source of supplemental nonprotein N (NPN) did not influence (P > .10) ruminal OM digestion. Net microbial N synthesis, N absorption, N retention, and microbial efficiency were greater (P < .05) for the CP-U than for the CP-A or urea diets. Apparent N digestibility of CP-A was 14 to 25% lower (P < .05) than that of the other diets supplemented with NPN. In Trial 2, treatment effects on lamb growth performance were evaluated in a 105-d growing-finishing trial involving 32 Sardi lambs (19 kg). Intake was similar (P > .10) across treatments (1.13 kg of DM/d). Daily gain of the urea-fed lambs (182 g) was higher (P < .05) than that of CP-U- or CP-A-fed lambs (138 g). Feed efficiency and dietary NE values were similar (P > .10) among diets containing NPN. Growth performance seemed to be more directly affected by intake, rather than N economy. Enrichment of DCP through ammoniation with urea was a superior method of NPN supplementation with respect to efficiency of N utilization. However, the ultimate response to the potential benefits of such treatment may be seen only if N is truly limiting performance.

Ammonia↗

PubMed1991

Effects of alfalfa maturity on energy utilization by cattle and nutrient digestibility by cattle and sheep.

Two comparative slaughter experiments conducted with growing beef steers (300 kg to 480 kg BW) fed alfalfa cubes demonstrated that animal performance diminished as alfalfa matured. In each trial, ADG (empty BW basis) was 10 to 20% greater from pre-bloom than from early-bloom alfalfa. Net energy for maintenance (Mcal/kg) followed a pattern similar to that of ADG, but NEg (Mcal/kg) did not decrease (P greater than .05) as alfalfa maturity increased. Digestion trials with steers and wethers clearly indicated significant reductions in apparent digestibilities of DM, energy, and cell wall fractions as alfalfa matured. Steers fed at 110% of maintenance in digestion Trails 1, 2, and 3 consistently digested cubed alfalfa to a greater extent than wethers fed the same alfalfa ground and pelleted. Digestion coefficients (percentages) for ADF, cellulose, NDF, and crude fiber were 5 to 14% greater for steers fed cubes than for wethers fed pellets. Regression equations calculated from results of three digestion trials indicate that digestible DM % and DE (Mcal/kg) could be predicted from ADF %, but they were 4 to 5% lower for wethers fed pelleted alfalfa than for steers fed cubes.

Animal Feed↗

PubMed1990

Feedlot performance of beef heifers implanted with Synovex-H: effect of melengestrol acetate, ovariectomy or active immunization against GnRH.

The effects on anabolic steroid implantation on feedlot performance and carcass composition and quality were examined in control (CNTRL), ovariectomized (OVX) or melengestrol acetate-fed (MGA) beef heifers or heifers actively immunized against GnRH (Anti-GnRH). Heifers (n = 112) were assigned randomly to a 2 x 4 factorial experiment. The two classes were made up of heifers not implanted and those implanted with Synovex-H. The four treatments were 1) CNTRL, 2) MGA, 3) OVX and 4) Anti-GnRH. Heifers were housed in individual pens and fed a high-energy diet for the 4-mo study. Synovex-H increased final live weight (P less than .005), carcass weight (P less than .005), ADG (P less than .0001) and feed efficiency (P less than .005) but did not alter carcass quality and yield grade (P greater than .05). Synovex-H increased deposition of protein (P less than .0001) and reduced deposition of fat (P less than .0001). Oral administration of MGA had no significant effect on feedlot performance or carcass quality. For heifers not implanted, active immunization against GnRH, but not ovariectomy, depressed ADG (P less than .05) and increased fat deposition (P less than .05) while reducing protein deposition (P less than .05). These effects of active immunization were reversed by concurrent administration of Synovex-H. Feedlot performance and carcass composition of heifers were improved by administration of anabolic steroids. When heifers were housed singly, neither ovariectomy, active immunization against GnRH nor oral administration of MGA improved feedlot performance of heifers implanted with Synovex-H.

Animals↗

PubMed1989

Effects of cimaterol on nitrogen retention and energy utilization in lambs.

Fifty-two weaned lambs were used in a comparative slaughter feeding trial and six lambs in a concurrent digestibility trial to investigate the effects of cimaterol on nitrogen retention and energy utilization. Cimaterol (CIM) was administered in the feed at 10 ppm for 90 and 14 d, respectively, in a comparative slaughter feeding trial and in a digestibility trial. No difference was found in dry matter digestibility. Nitrogen retention in the CIM group (739 mg/Wkg.75/d) was greater (P less than .01) than that of the control group (321 mg/Wkg.75/d). This difference was accounted for primarily by reduced nitrogen loss in urine of the CIM group. Cimaterol improved growth rate and feed/gain ratio, although these improvements were only evident during the first 42 d of the 90-d feeding trial. The improvement in growth performance of the CIM group was associated with increased protein gain in the empty body (40.2 g/d, P less than .01) as well as in carcass (26.9 g/d, P less than .01), compared with 30.1 and 14.5 g/d of the control group. Cimaterol decreased (P less than .01) fat gain (91.4 vs 109.9 g/d), total daily energy gain (1.08 vs 1.22 Mcal) and energy gain/kg gain (4.17 vs 5.11 Mcal) compared with the control. Feeding CIM increased (P less than .01) estimated fasting heat production (73 vs 64 Kcal/Wkg.75) and metabolizable energy requirement for maintenance (110.2 vs 92.7 Kcal/Wkg.75) over the control.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Agonists↗

PubMed1988

Effects of body weight, frame size and rate of gain on the composition of gain of beef steers.

Energy concentration of gain (EG) is an inherent component in beef cattle feeding systems. The National Research Council (NRC) uses equations based on body weight, rate of gain and cattle type to predict EG and, in turn, to calculate dietary energy requirements. From EG, fat and protein deposition can be calculated directly. A dynamic computer growth model also can be used to estimate EG. In both the NRC and the computer model, EG increases from about 3 to 6 Mcal/kg as body weight increases from 200 to 500 kg if daily gain is 1 kg. Both NRC and the model predict EG of calves to be about .3 Mcal/kg greater than a previous NRC system. In contrast to the NRC, model-predicted EG of yearlings is lower at lighter and greater at heavier body weights. Rate of gain affects estimates of EG more for the dynamic model than for the NRC systems. When predicted EG was compared with observed EG for 46 pens of feedlot steers in comparative slaughter trials, NRC estimates exhibited a narrow range compared with observed values with correlation coefficients of r = .38 and r = .71 (previous NRC). Model estimates of EG were closer (r = .85). The NRC predictions of EG systematically erred with initial body composition, diet metabolizable energy and length of feeding period (P less than .01) and with initial body weight and rate of gain (P less than .05). No systematic errors in model-predicted EG were detected. Enhanced model sensitivity to compensatory growth and rate of gain should reduce both EG and body weight gain prediction errors.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Nutritional Physiological Phenomena↗

PubMed1987

Effects of energy intake on energetic efficiency and body composition of beef steers differing in size at maturity.

Hereford and Charolais steers were fed at three levels of feed intake (low, medium or ad libitum) to similar weights within breed groups to evaluate effects of energy intake on energetic efficiency and body composition. Two methods were employed to partition metabolizable energy intake into use for maintenance and gain. Method one used an assumed daily fasting heat production of 77 kcal/weight (W).75; method two estimated fasting heat production from the regression of log daily heat production against metabolizable energy intake (kcal/W.75). Net energy for gain (NEg) was determined in method one by regressing retained energy (kcal/W.75) against feed intake (g/W.75). For method two, the estimated maintenance requirement of feed was subtracted from total feed intake and retained energy was regressed against feed intake above maintenance to estimate NEg. Conclusions regarding feed energy utilization for maintenance and gain were the same by either method of energy partitioning. Charolais steers used feed energy less efficiently for gain than Hereford steers, and ad libitum steers used feed energy less efficiently for gain than steers at lower intakes (P less than .05). Charolais steers made leaner (P less than .05) gains than Hereford steers. Although steers consuming the lowest level of feed made gains containing a lower percentage of fat and a higher percentage of protein (P less than .05) than steers at higher intakes, body composition within a breed was not altered by level of energy intake when animals, within breeds, were slaughtered at similar end weights.

Animals↗

PubMed1986

Feedlot performance and tissue residues of cattle consuming diets containing aflatoxins.

A comparative slaughter feeding trial was conducted using crossbred Hereford-Angus steers. Cottonseed meal known to be contaminated with aflatoxins was fortified with long-grain rice cultures of Aspergillus flavus to produce complete rations that contained 0, 60, 300 and 600 ppb aflatoxin B1 (AFB1). Forty steers, weighing approximately 250 kg were randomly assigned to four equal treatment groups. Animals were housed in individual pens and fed the assigned contaminated ration ad libitum for 155 d. On d 156 all animals were placed on the control ration for 14 d. Animals were weighed and blood samples collected every month for clinical chemistry analysis. Liver, muscle and fat biopsies were collected at 6-wk intervals. These samples were stored in liquid N2 prior to analysis for aflatoxin M1 and B1 content. Separate liver samples were taken for histopathological examination. Aflatoxin was withdrawn from the diet 2 wk prior to slaughter. After 1 wk of withdrawal liver, muscle and fat samples were collected and assayed for AFB1 and aflatoxin M1 (AFM1). Liver samples also were taken for histopathological examination. Growth rates and feed intakes in the 60 and 300 ppb aflatoxin treatments were not significantly different from controls. The 600-ppb treatment group had a decrease in feed intake and rate of gain. Rations containing 60 and 300 ppb of aflatoxin had no significant influence on blood components and enzyme patterns. The 600-ppb treatment caused a slight, but consistent, increase in serum glutamic oxaloacetic transaminase and alkaline phosphatase.(ABSTRACT TRUNCATED AT 250 WORDS)

Aflatoxins↗

PubMed1985

Efficiency of feed energy utilization for protein and fat gain in Hereford and Charolais steers.

Two multiple regression models were used to estimate energetic efficiency of protein and fat gain for 84 grade British steers, predominantly Hereford, and 84 Charolais steers using data obtained from a comparative slaughter feeding trial. In Model One, metabolizable energy intake was regressed on energy gain as fat and protein; the intercept was an estimate of maintenance. For Model Two, maintenance requirements were estimated by regression of log heat production (kcal/kg.75) on metabolizable energy intake (kcal/kg.75) and iterating to the point at which heat production was equal to metabolizable energy intake. Energy intake above maintenance was then regressed on energy gained as fat and protein. Results from Model One showed the efficiencies of protein and fat gain to be 10 and 49%, while Model Two indicated these efficiencies were 11 and 58%. Breeds did not appear to differ significantly in the efficiency with which they used metabolizable energy for protein or fat deposition.

Animal Feed↗

PubMed1982

Maternal energy status of beef cattle during single and twin pregnancy.

A study was undertaken to determine the metabolizable energy (ME) intake and ME requirement for beef heifers and cows during twin pregnancy. Weekly feed consumption and body weights were recorded during the last trimester of twin pregnancy for 19 Hereford cows and 16 Hereford heifers. The same data were recorded for six Hereford cows and eight Hereford heifers that calved singles. ME intake per unit of metabolic body size was higher for heifers than cows (P less than .05), but was not affected by whether the dam was pregnant with a single or with twins. In general, ME intake decreased during the last trimester of pregnancy. During this time, heifers and cows with singles gained weight (pregnant weight minus weight of the conceptus), while dams with twins lost weight (P less than .01). The greatest weight loss for dams with twins was observed late in pregnancy. The ME requirement of pregnancy was greater for dams with twins than singles (P less than 0.01), and the difference in maintenance ME requirement approached significance (P less than .10). The high ME requirement for the twin pregnancy and the weight loss experienced by dams during the last trimester may have implications for management decisions pertaining to the prevention of complications that often occur with twin pregnancy in cattle.

Animals↗

PubMed1979