Empty body composition of 68 mixed-breed and 50 Angus steers was determined by chemical analysis of the right half-carcass and entire noncarcass fraction of each steer. Chemical composition was used to develop prediction equations for empty body protein (EBPRO) and fat (EBFAT) in steers using urea space (US) and body weight measurements. Previous research showed a significant positive correlation between empty body water (EBH2 O) and urea space in these steers. For all steers studied, the percentage of EBH2 O ranged from 44.8 to 69.2 (mean = 56.0), the percentage of EBPRO ranged from 14.1 to 19.8 (mean = 17.0) and the percentage of EBFAT ranged from 6.1 to 38.1 (mean = 22.1). The best predictions obtained were multiple regression equations with actual weight of body components as dependent variables and US and empty body weight (EB) as independent variables. Urea space alone was a poor predictor of EBFAT, but US improved predictions based on live weight (LW) or EB alone. Coefficients of determination for the best predictions of percentage of composition were not as high as coefficients of determination for the best predictions of actual weight of body components. These data suggest that US measurements can be used to predict empty body composition of live steers, but this may require repeated measurements and an independent estimate of EB from LW for greatest accuracy.
First-growth orchardgrass and alfalfa were harvested at two stages of maturity, treated with formic acid plus formaldehyde, and ensiled as direct-cut silage during 1978 and 1979. The 1978 silages were fed to eight yearling Holstein heifers (average BW 273 kg), and the 1979 silages were fed to eight yearling Holstein steers (average BW 264 kg) in replicated 4 × 4 Latin square experiments to measure total energy and N balance using the Beltsville open-circuit respiration calorimeters. Silage was offered daily at 70 g of DM/kg·75 BW, a rate that was essentially ad libitum for late-maturity orchardgrass, but restricted for the other three silages within each experiment. Cattle fed alfalfa used ME for growth with greater efficiency (55%) than did cattle fed orchardgrass (40%). Cattle fed orchardgrass achieved the same tissue N retention at a lower total N intake than did cattle fed alfalfa. Differences in tissue N retention were accounted for by differences in N intake insoluble in autoclaved ruminal fluid, but soluble in acid detergent, a fraction termed available N. At equal intake of ME and available N, cattle fed alfalfa gained more tissue energy than those fed orchardgrass and gained tissue protein similarly to cattle fed orchardgrass. Fractions composing digestible OM were different between forage types but similar within forage type between maturities at harvest. More efficient use of ME for growth by animals fed alfalfa compared with orchardgrass may be related to differences in digestible OM composition, load of digestive tract content, and composition of absorbed nutrients.
Eight rumen-fistulated cattle (four Angus steers and four nonlactating Holstein cows) were fed a cracked corn-based concentrate (65% of dry matter) and corn silage (35% of dry matter) diet containing: (1) no buffer, (2) 2.5% limestone, (3) 2% sodium bicarbonate (NaHCO3) or (4) 1.25% limestone and 1.25% NaHCO3. Each diet was fed at approximately maintenance and two times maintenance levels of intake, resulting in eight treatments in a Latin square design. Buffer treatments had no effect (P>.10) on rumen fluid pH, rumen ammonia N concentration, total volatile fatty acid (VFA) concentration or rumen buffering capacity between pH 7.0 and 5.5. Rate of disappearance of solid and liquid fractions from the rumen was measured using Cr-labeled dietary fiber and Co-EDTA, respectively. Rate of disappearance was not significantly affected by treatments, although liquid disappearance rate Was 7% faster with buffer treatments than with the control. Fecal pH was increased (P<.01) approximately .5 units by all buffer treatments. Increasing intake to two times maintenance resulted in lower rumen pH (6.03 vs 6.37), increased total VFA concentration (115 vs 99 mmol/liter), increased rate of liquid disappearance from the rumen (6.6 vs 5.8%/h) and decreased concentration of Cr in the dry matter fraction of the rumen contents (all P<.01).
The influence of bovine growth hormone (bGH) on the irreversible loss and oxidation rate of non-esterified fatty acids (NEFA) was evaluated in six Hereford heifers fed at near-maintenance energy intake. Subcutaneous injection of bGH increased both the concentration (P < 0.05) and irreversible loss (P < 0.001) of plasma NEFA. Key words: Growth hormone, nonesterified fatty acids, cattle
Animal acceptance of a protected tallow product (PT) and its effect on performance was evaluated with 180 steers (average weight 350 kg). Animals were assigned by weight and breed stratification to three treatment groups, each replicated twice with 30 animals per pen. Treatments consisted of: (1) a high energy flaked corn and corn silage-based control (C) diet; (2 + 3) partial replacement of flaked corn in the C diet with PT and corn silage to provide (2)5% supplemental fat (medium fat, MF) and (3) 10% supplemental fat (high fat, HF). All diets were formulated to contain equal amounts of metabolizable energy. Live animal performance of steers fed the MF diet was superior (P<.05) to that of the HF-fed steers, as evaluated by the following parameters: feed intake (C, 9.6 kg DM/day; MF, 9.8, and HF, 9.1), live weight gain (C, 1.45 kg/day; MF, 1.50, and HF, 1.38) and feed efficiency (C, 6.61 DM intake/ gain; MF, 6.49, and HF, 6.59). Steers fed the diets containing PT had a lower (P<.05) percentage retail yield based on carcass measurements (C, 50.7% retail yield; MF, 50.0, and HF, 49.9), with dietary fat influencing kidney and pelvic fat percentage the most. The percentage of carcasses that graded Choice or higher did not differ significantly among treatments. Specific gravity measurements indicated that PT-fed steers were fatter (P<.01) than C-fed steers evaluated on a constant carcass weight basis (C, 29.1% empty body fat; MF, 30.7, and HF, 30.4). Animals fed the MF diet ate the most and yielded about 6% more empty body energy (P<.01) than animals given the other treatments (C, 1,759 Meal empty body energy; MF, 1,872, and HF, 1,782). HF-fed steers ate less and were not as heavy at slaughter as C-fed steers but yielded nearly equal amounts of empty body energy.
Hair samples from beef cattle were examined to determine their response to feeding varying levels of protein and energy. Blood urea nitrogen (BUN) and nitrogen balance tests were also performed to provide a reference for comparison. Twenty-four weanling calves each weighing approximately 200 kg were equally divided into four groups and were fed the following percentages of the N.R.C. recommendations for crude protein with energy to give the indicated predicted gain: high protein-high energy (HP-HE) group — 111%, 1.0 kg/day; high protein-low energy (HP-LE) group — 102%, .2 kg/day; low protein-high energy (LP-HE) group — 65%, .8 kg/day; low protein-low energy (LP-LE) group — 45%, .2 kg/day, respectively. After 60 days all groups received the HP-HE ration for a 30-day repletion period. Hair samples were taken from the back and stomach regions on day 1 and every 15 days thereafter until the conclusion of the experiment on day 90. Several parts of the root and shaft were measured and evaluated, including percent of the hairs in the anagen (active) phase, percent of the bulbs in atrophy, shaft diameter, bulb diameter and bulb length. Of all the hair parameters evaluated in this study, percent of the bulbs in atrophy was the only one effective in diagnosing a protein or energy deficiency. Differences among groups (P<.01) found on day 15 remained through day 60. As energy and/or nitrogen intake decreased, percent of the bulbs in atrophy increased (P<.001). Average daily gain, nitrogen balance and BUN results reflected the level of protein and energy intake.
Rumen pH, ammonia-N (NH3-H), buffering capacity and volatile fatty acid (VFA) concentration were measured with four rumen-fistulated cows fed a corn silage and corn meal-based diet with (WL; 2.5% of dry matter) or without limestone (WOL) at maintenance or two times maintenance levels of intake. Three crude protein (CP) levels (11, 14 or 17%) also were fed, resulting in 12 treatments. Each animal was fed all treatments. Limestone increased (P<.01) rumen pH at 11% CP (6.30 WOL vs 6.53 WL), while increasing protein increased (P<.01) rumen pH only in diets without limestone (6.30 at 11% CP vs 6.44 at 14% CP vs 6.49 at 17% CP). Fecal pH values, determined with another set of animals subjected to the same treatments, were increased (P<.01) by increased protein (5.98 at 11% CP vs 6.20 at 14% CP vs 6.36 at 17% CP) and by limestone (5.75 WOL vs 6.61 WL). Rumen ammonia values reflected dietary N intake (10.5 mg NH3-N/dl at 11% CP vs 17.8 at 14% CP vs 29.9 at 17% CP). The concentration of VFA increased with each increase in protein, but was not affected by limestone. Rumen fluid buffering capacity evaluated between pH 7.0 and 5.5 followed a pattern of significant differences similar to that observed for rumen pH values. Rumen fluid buffering capacity of limestone treatments evaluated from pH 7.0 to 3.0 by units of .5 (data collected only at 14 and 17% CP levels) was increased (P<.01) between pH 5.0 and 4.5. Increasing CP from 14 to 17% increased (P<.01) the buffering capacity of rumen fluid between pH 6.0 and 4.5. Neither factor slowed rate of pH decline below pH 4.0. Level of intake had a significant effect on nearly all traits measured, but there were no significant level of intake × diet interaction effects.
A respiration calorimetry and metabolism study was conducted to evaluate the effects of adding a commercially produced protected tallow product (PT) containing approximately 40% ether extract to a beef cattle roughate diet. Twelve yearling steers (average weight 300 kg) were fed three dietary treatments: (1) control (C), 69% alfalfa hay and 31% corn; (2) medium fat (MF), 75% alfalfa hay and 25% PT, and (3) high fat (HF), 62.5% alfalfa hay and 37.5% PT. Dry matter digestibilities for the fat-treated diets were lower (P<.05) than that for the C diet (69.6, 65.0 and 66.8 for C, MF and HF, respectively) because of an apparent decrease in the digestibility of the neutral detergent solubles fraction. Apparent ether extract digestibilities were high (85% or higher) for the fat-supplemented diets, while digestibilities of other nutrients, including neutral detergent fiber, were not influenced significantly by dietary fat. Methane energy as a percentage of gross energy was reduced by fat treatment (P<.01), probably because of a decrease in fermentable substrate rather than an inhibition of fermentation. The amount of energy retained as body fat was not increased as a result of either fat treatment. The lack of response in composition of gain may have been associated with the size and age of the animals used in the experiment. Experimentally derived net energy values for the PT were 3.4 Meal NEm/kg and 2.2 Meal NEg/kg.
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