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In two experiments tall fescue (TF) and orchardgrass (OG) were fertilized in split applications with 0 or 882 kg NH4NO3/ha and 0 or 833 kg K2SO4/ha to determine the effects on TF and OG amino acid composition. Both free (FAA, unprecipitable in 6% trichloroacetic acid) and hydrolyzable (HAA, hydrolyzed in 6 N HCl at 115 C for 22 hr) amino acid compositions were determined. Data were combined for regression analyses using data for herbage nitrogen (N) and sulfur (S) fractions from the same samples but previously reported (12). Ammonium nitrate fertilization changed herbage amino acid concentrations while K2SO4 fertilization had no effect. The relationship (P<.0001) between herbage total FAA and nonprotein N concentration in herbage was total FAA (μmol/g) = 17.24 ± 2.045 (nonprotein N, mg/g) + 17.37, R2 = .477. Furthermore, free cystine and methionine were linearly related (P<.001) to herbage nonprotein nitrogen content. Linear regression of total HAA (μmol/100 mg protein N) on total N content was significant (P<.002). The cubic equation improved the R2 to .338 and was total HAA (protein N basis) = -3778.7 (total N, mg/g) + 118.5 (total N)2 -1.2 (total N)3. Regression of total HAA content (μmol/g) on protein N content explained .490 of the variation and there was a significant (P<.0001) cubic effect (R2 = .580). Regression coefficients were negative for cystine and methionine concentrations (protein N basis) when regressed on total N content. There were no relationships between hydrolyzable S amino acids (μmol/g) and herbage N or S fractions. Ammonium nitrate fertilization increased (P<.0001) total FAA and total HAA concentrations which were nitrogenous components contributing to increased nonprotein N and protein N fractions, respectively.

Six steers were used in a replicated 3x3 latin square metabolism study to observe the effects of restricted water intake on feed intake, nutrient digestibility and nitrogen metabolism. Each steer received a full feed of a ground ear corn-urea ration and water free choice (FC), 80% of FC or 60% of FC throughout the experiment. Restriction of water to 60% of FC resulted in a significant (P<.05) reduction in voluntary feed intake. Fecal water, urine output and unmeasured water were significantly (P<.01) correlated to water intake. As water was restricted, the amount of water lost through each of these excretion pathways was decreased. Urine specific gravity paralleled urine osmolality and was negatively (P<.01) correlated to both water intake and urine output. Apparent digestibility tended to be consistently higher when the water intake was restricted but these values were not significantly different from control digestion coefficients. Nitrogen retention tended to increase when water was restricted and was negatively (P<.01) correlated to total nitrogen excreted in the urine. Infusion with a constant amount of urea solution (20% w/v) intravenously resulted in less total nitrogen and less urea nitrogen being excreted in the urine of water restricted steers. These observations indicate that nitrogen recycling was increased due to water restriction.

Addition of oyster shell to 20% roughage and all-concentrate rations resulted in decreased gain and feed consumption and lower feed efficiency. Steers fed ground ear corn rations gained faster (P<.05) and had a greater (P<.05) feed intake than steers fed shelled corn rations. Feed consumption calculated in 28-day periods was not significantly different among the treatments. Oyster shell greatly increased the incidence of bloat as measured in the last 28 days of the trial. Total VFA concentration tended to be higher in steers fed the ground shelled corn rations. Feeding oyster shell did not significantly alter ruminal fluid pH, VFA concentration, or level of blood calcium or phosphorus. Chronic rumenitis was increased when oyster shell was added to the ground ear corn ration and was also characteristic of steers fed the shelled corn rations. The number of abscessed livers was highest in steers fed the all-concentrate ration followed by rations containing oyster shell. Oyster shell in ear corn and all-concentrate rations reduced performance and increased management problems during the trial. Under the conditions of this experiment, oyster shell was ineffective in improving the performance of steers fed high grain finishing rations.

Four steers were fitted with permanent ruminal cannulae and fed either an all-roughage or an all-concentrate diet. The ruminal concentration of volatile fatty acids and pH were compared from five intraruminal sites. The first sample was collected with a stomach tube, and samples from the four remaining sites were collected through the rumen cannula. Samples were collected 4 hr. and 8 hr. after the morning feeding. In most cases, the pH was highest in the stomach tube sample and was lowest near the surface of the rumen fluid in steers fed the roughage diet and lowest near the ventral floor of the rumen in those fed the concentrate diet. The concentration of volatile fatty acids in the hay-fed steers was highest near the top of the rumen fluid at the 8-hr, time, but no significant differences were observed at the 4-hr, sampling time. The concentration of volatile fatty acids in the grain fed steers was highest in the ventral portion of the rumen at both time periods. Comparison of the individual acids suggested differential fermentation rates for the two diets. Significant differences in volatile fatty acid concentrations among the sampling sites were observed but no general trend was apparent.

Physiological quantities of 3H-vitamin A and 14C-beta-carotene were intravenously administered to bile-duct cannulated sheep. During 24-hr, collection periods, 21% of the injected dose of vitamin A was recovered in the bile. In the B-carotene trials, an average of 18% of the injected dose was observed in the bile during the collection periods. Secretory patterns of radioactivity in the bile were similar for the vitamin A and B-carotene trials. The major portion of the recovered radioactivity was secreted into the bile during the first 12-hr, of collection (87% for vitamin A vs.83% for B-carotene). Infusion of radioactive bile from the vitamin A trials into the duodenum of an anesthetized sheep showed appreciable absorption of vitamin A metabolites. These data establish biliary secretion of vitamin A and B-carotene metabolites in the bile of sheep and suggest that the enterohepatic circulation plays an important role in the vitamin A metabolism of sheep.

Three experiments were conducted to determine the effect of diet dilution with polyethylene on the voluntary feed intake of steers. For the first 3 wk. in experiments I and II, the 90% ENE groups consumed the amount of feed necessary to bring daily ENE intake up to the control ENE intake. The fill of the reticulo-rumen was believed to be the factor limiting feed intake due to polyethylene accumulation or slow passage from the reticulo-rumen in the 80% ENE group in experiments I and II, and for the 90% ENE group in period 2 of experiment II. The results of experiment III supported the hypothesis that reticulo-rumen fill limited feed intake when steers were fed the 80% ENE diet. Analysis of the reticulo-rumen contents in experiments I and II confirmed the results of long-term studies in which increased fill was due to polyethylene accumulation. Differential feeding of colored and white polyethylene in experiments I and II showed that there was not a stasis of polyethylene particles in the rumen, but rather a continuous turnover. The relative percentages of volatile fatty acids were not significantly altered by total diet dilution, with the exception that isobutyric acid was increased in those steers fed the diluted diets in experiment I. However, a trend of increased acetate and decreased propionate was observed in those steers fed the diluted diets.

Sixty-four yearling steers were used in a completely randomized design to study the effects of corn silage diets supplemented with soybean meal, urea, soybean meal-low-nitrogen and urea-low-nitrogen on growth and plasma and rumen fluid components. The diets were calculated to contain approximately 100% and 85% of the N.R.C. requirements for crude protein. The feeding period was 160 days in length. The steers receiving soybean meal at a higher level gained faster (P<.05) than each of the other treatment groups. Plasma urea nitrogen concentrations were higher (P<.01) on day 23 and on day 125 for steers fed the higher levels of soybean meal and urea. Lysine concentration was higher (P<.05) in plasma of steers fed the soybean meal supplemented diets when compared with the urea supplemented diets on day 23. Plasma concentrations of several of the essential amino acids (valine, isoleucine, histidine, leucine and lysine) were higher (P<.01) during the finishing phase (day 125) than during the growing phase (day 23). Of the nonessential amino acids, glutamic acid and glycine were lower (P<.01) during the finishing phase than during the growing phase. Rumen ammonia nitrogen concentration was higher in steers fed the two higher nitrogen level diets. Propionic acid concentration in rumen fluid was highest in the steers fed soybean meal at the higher nitrogen level.

Four Angus steers weighing 450 kg were used in a 4 × 4 latin square design to study the effects of different protein supplements (corn, soybean, fish and linseed protein) on bulk ammo acid composition and amino acid availability of rumen bacteria. The effects of different protein supplements on plasma amino acids, plasma urea nitrogen, rumen volatile fatty acids and rumen ammonia were also studied. Bulk amino acid composition of rumen bacteria was not significantly (P<.05) altered by protein supplement. Availability of rumen bacterial amino acids was estimated by measuring the concentrations of amino acids released from rumen bacterial protein upon in vitropepsin-pancreatin digestion. The release of threonine, serine, glutamic acid, valine, methionine, phenylalanine, lysine and the total amino acids released varied significantly (P<.05) among treatments. Lysine had a (P<.01) greater release rate from bacteria obtained from steers fed soybean meal than from steers fed fishmeal. Plasma leucine and aspartic acid were significantly (P<.05) affected by protein source. Rumen acetate, propionate and ammonia-nitrogen levels varied significantly (P<.05) among treatments. These data indicate that the availability of certain amino acids to the ruminant animal can vary with the source of dietary protein.

Diethylstilbestrol (DES) has been used to improve weight gain and feed efficiency of growing and finishing steers. Research at various experiment stations has shown that weight gains are generally improved about 15% and feed efficiency improved about 12% by feeding DES (Burroughs et al., 1955; Burroughs and Zmolek, 1963; Clegg and Carroll, 1957; Perry et al., 1955; Riggs, 1958). Diethylstilbestrol exists in two stereochemical configurations, cisor trans. Raun, Cooley and Smith (1970) reported that by increasing or decreasing the transor cisisomer content of DES, its biological activity is altered depending on the transto cisratio present. This study was initiated to compare the effects of feeding high cisDES or high transDES on growth, carcass characteristics and certain blood pa- rameters of finishing steers.Ninety-six Angus steers averaging 298 kg were fed in a 140-day growth trial to study the comparative efficacy of the cisand transisomers of diethylstilbestrol.

Charolais-Hereford steers were fed 80 g of tapazole per ton of corn-soybean meal ration. Plasma and liver samples and feed efficiency were obtained at eight 14-day periods for 112 days. Vital organ weights and carcass data were collected upon termination of the experiment. Tapazole administration resulted in increased ADG, G/F, PUN, rib eye muscle water and conformation score and a decrease in FI, plasma FAN, plasma PBI, bone weight, heart weight, liver weight, GH/g pituitary and quality grade. No significant differences in other carcass parameters were observed. No significant differences were observed in plasma GH, glucose, pituitary weight or protein synthesis in cell-free liver homogenates. The response of most serial parameters measured was dependent upon time on treatment.

Sixty Angus steers were fed in a completely randomized design with a 2 × 2 factorial arrangement of supplemental nitrogen, soybean meal or urea and physical forms of supplemental corn, cracked or ground. Average daily gains and the carcass traits measured were not affected by form of supplemental corn or nitrogen sources. Plasma protein was not influenced by treatment. Plasma urea nitrogen was higher (P<.01) in the urea-supplemented steers. Plasma free amino nitrogen was higher (P<.05) in the soybean meal supplemented steers. The concentrations of glutamic acid, alanine and tryosine were higher (P<.10) in the plasma of the urea-supplemented steers.

In a 2-year study, 225 steers were wintered on standing Kentucky bluegrass and fed limited energy and protein supplements and a combination of these two supplements. In the first experiment the steers were offered: (1) no supplement, (2) protein blocks free choice, (3) 0.45 kg soybean meal per steer daily, (4) 1.36 kg ground shelled corn per steer daily and (5) 0.45 kg soybean meal plus 1.36 kg ground shelled corn in a 140-day wintering study. The treatments in the second experiment were the same as in experiment 1, with the exception that the protein block group was eliminated and the length of the trial was 126 days. These data indicated that steers can be wintered on standing Kentucky bluegrass and no supplement with a small amount of gain. This wintering system required a minimum expenditure of labor, since the steers were supplementally fed hay only when the ground was covered with snow.

Forty-eight heifers averaging 4 months of age were divided randomly into three groups. Sixteen heifers served as controls (group 1) and groups 2 and 3 were injected with 125 mg chlormadinone acetate at 4 and 6 months of age. At 8 months of age, the heifers were weaned and moved to drylot. Group 2 was injected with 250 mg Estrostat at 0, 70 and 140 days and group 3 with 250 mg at 0 and 98 days of the 196-day growing phase. The heifers were then turned to pasture for the breeding phase of the study. The average daily gains of heifers during the preweaning phase were not influenced by Estrostat treatment. The overall gains in drylot were not affected by treatment, but differential rates of gain were observed. Estrostat injection in group 2 (250 mg Estrostat at 0, 70 and 140 days) effectively suppressed estrus throughout the 196-day growing phase. Of those heifers injected at 0 and 98 days, five of 15 heifers exhibited estrus once. The carcass traits measured at slaughter were not significantly influenced by Estrostat treatment. All heifers in group 3 were pregnant at slaughter. The heifers in group 2 exhibited estrus later in the breeding period which possibly resulted in a lower conception rate. These data suggested that growth and development of the reproductive organs were not impaired by repeated Estrostat injections.

Seventy-eight steers were randomly assigned to various feeding regimens to determine the effects of the addition of nondigestible material (polyethylene) to the diets. The data indicated that energy concentration of the diet is of importance in the regulation of food intake. A trend toward compensatory food intake to meet energy requirements was observed when increased fill and dietary density, palatability or quality were not factors decreasing feed intake. Compensatory intake was observed in two instances even though fill was significantly increased. The adjusted average daily gain as compared to unadjusted showed the importance of an adjustment for fill when diets of varying physical nature are fed. Efficiency of gain was significantly decreased on only two of the diets containing polyethylene.

Steers fed 800 mg tapazole per day had a significantly greater ADG and weighed more after a 112-day feeding experiment than control steers. However, the control cattle had slightly less subcutaneous fat and more marbling than the treated steers, resulting in a higher quality grade for the control steers. The rib eye area was significantly larger, the conformation grade higher, and muscle color lighter in the treated steers than in control animals.Muscles from the control steers contained slightly more aerobic (type I) type muscle fibers as measured by DPNH-TR and Sudan Black B stains. However, the type I fibers were larger in the treated animals and the type II fibers larger in the control animals. As a result, the area occupied by type I and type II fibers was essentially the same between the two groups of animals.The adipose tissue of the control steers contained significantly more C18:1, C18:2, sat. 8 (an unidentified saturated fatty acid eluted just before C18:0) and total unsaturated fatty acids than did tapazole-treated cattle. Muscle lipids contained significantly less C14:0, sat. 2 and sat. 3 and more sat. 4 (unidentified saturated fatty acids eluted between C14:0 and C16:0) and C18:2 fatty acids than the depot fats. The external fats contained significantly more sat. 2 and C16:1 and less sat. 7 (unidentified saturated fatty acid eluted just after C16:1) fatty acids than internal fats. There was no significant differences in tenderness between tapazole fed and control steers.

Forty yearling Angus steers were used in an experiment to observe the effects of feeding thyroprotein (Protamone) throughout a 180-day feeding period or for only the first 84 days of the trial. The treatment groups were: Control (C)—a basal ground ear corn diet supplemented with soybean meal to contain approximately 11% crude protein, thyroprotein (T)—basal diet containing 0.367 g thyroprotein per kilogram of feed and fed for the 180-day feeding period, and thyroprotein-control (TC)—fed the thyroprotein (T) diet for the first 84 days and the control diet (C) for the remainder of the trial. Average daily gains for the 180-day trial were (C) 1.01 kg, (T) 0.90 kg, and (TC) 1.13 kilogram. The gains made by the thyroprotein group were (P<.01) lower than that of the TC group. Daily feed intake was increased (P<.05) in both the thyroprotein and TC groups. Feed required per unit of gain was higher (P<.05) for the thyroprotein group than for the other two groups. The increased gain by the TC group during the second period (85 to 180 days) resulted in an improvement (P<.05) in feed utilization as compared with that of both the control and the continuously fed thyroprotein group. Thyroprotein intake averaged 4.1 g/day for the thyroprotein group and 4.0 g/day for the TC group during the 84 days they were fed the thyroprotein diet. The longissimusarea was significantly (P<.05) lower in the thyroprotein group than in the control group. The thyroprotein group contained less body fat, as indicated by the fat over the rib and kidney fat. The effects of treatment on serum free fatty acid, cholesterol and urea nitrogen levels were discussed.

Twelve yearling Aberdeen Angus steers were assigned to two periods and two treatments in a factorial experiment designed to study the effect of water restriction on the excretion of chromic oxide and crude protein. Each steer was confined to a metabolism crate and received 4 kg of a ration plus water free choice or 60% free choice daily. During each period, fecal grab samples were taken at 2-hr, intervals for 48 consecutive hr. followed by a 7-day total collection of feces. The percent recovery of chromic oxide averaged 103.1 and 102.3 for the steers offered water free choice or 60% of free choice, respectively. There was no difference (P>.05) in the apparent digestion of crude protein between treatments as calculated by a 7-day total collection of feces or by the chromic oxide indicator method. There was also no difference (P>.05) attributable to the method used for determination of apparent digestion of crude protein or dry matter. There was an increase in dry matter digestibility and chromic oxide concentration in fecal dry matter (P<.05) when water was restricted. Water restriction did not affect (P>.05) crude protein concentration of fecal dry matter. These data suggest that water restriction has little effect on the excretion of chromic oxide and crude protein. The lack of constancy in the ratio of nutrient to indicator excretion with time indicates the need for a sampling procedure which includes each 2-hr, interval throughout the day.

Yearling steers receiving soybean meal supplementation to ear corn finishing rations (11.0% CP) gained (P<.05) more than those fed the basal ear corn ration (7.0% CP). Gains made by steers fed the soybean meal ration were similar regardless of whether supplement was provided the entire finishing phase (112 days) or during only the first 56 days. Replacing soybean meal with urea and corn on an isonitrogenous, isocaloric basis resulted in a 11.0% reduction in gains. Daily gains made by steers fed the urea supplemented ration were only 0.04 kg greater than for those fed no supplemental nitrogen.Supplementation, as well as source of supplemental nitrogen, significantly (P<.05) influenced the plasma amino acid concentrations. The amino acids generally most responsive were valine, isoleucine, leucine and lysine. However, in some instances the phase of the trial during which the samples were collected influenced the results. Correlations between growth response and plasma amino acid were discussed in relation to protein adequacies of the ration fed.Postprandial plasma urea levels were significantly higher for steers fed either soybean meal or urea supplements (P<.05).From the growth measures and various blood parameters discussed it appears that (1) yearling steers (332 kg) need a preformed protein supplement during the early phase of the feeding period and (2) such requirements cannot be met entirely by microbial protein synthesis from urea.