We evaluated the potential for gossypol intoxication and resulting effects of feeding large amounts of cottonseed meal to dairy cows in early lactation. Twenty-four Holstein cows were grouped by age, prior production, and days postpartum and randomly assigned to one of three diets. After 14-day standardization cows individually were fed a blended corn-corn silage ration supplemented with screw-pressed cottonseed meal, direct solvent extracted cottonseed meal, or soybean meal during a 14-wk comparison. Packed cell volume, copper in plasma, activities of transaminases, and gross composition of milk were not affected by ration. Hemoglobin was depressed, and total protein of plasma was elevated by the 9th wk in cows fed the solvent meal. Erythrocyte fragility was detected in those cows by the 7th wk and appeared later in cows fed the pressed meal. Gossypol was identified and quantitated in plasma and liver but was not detected in erythrocytes or milk from cows fed cottonseed meal. Elevated ambient temperatures precipitated increased respiration rates in the cows fed solvent meal. Physiological changes and gossypol in tissues of cows suggest that intoxication is possible in mature ruminants consuming cottonseed meal containing high free gossypol.

Two digestion and metabolism experiments were conducted to determine effects of monensin in low-protein diets. Monensin supplementation (27 mg/kg of diet dry matter) of steers (303 kg) fed 8.7% crude protein increased (P less than .01) apparent N digestibility and N retention and decreased (P less than .01) percentage of N apparently absorbed lost in urine. Apparent digestibilities of dry matter, gross energy and acid detergent lignin were increased (P less than .05). Digestibilities of neutral detergent and acid detergent fibers were not affected by monensin. In growing wether goats (15 kg) fed 8.5% crude protein, monensin (23 mg/kg of diet dry matter) improved (P less than .01) apparent N digestibility and apparent N absorption. However, urinary N excretion also increased (P less than .05), resulting in no difference in N retention. Monensin did not affect digestibilities of dry matter or gross energy. Efficiency of feed conversion and average daily gain were improved with monensin supplementation of growing goats fed a low-protein, high-roughage diet. Monensin resulted in typical shift of acetate-to-propionate ratio in both experiments. Results suggest that improved N utilization may account for some benefits of feeding monensin.

Four experiments were conducted to evaluate the effect of diet and the administration of H2-antagonists in feed on gastric ulcer formation and performance of growing-finishing swine. Pigs receiving a finely ground diet (less than lmm) grew faster (.73 vs .68 kg/d, P less than .01) and had better feed utilization (3.47 vs 3.76, P less than .01) than pigs receiving a cracked corn-based diet. Incidence of ulcers in the esophageal region of the stomach of pigs fed the finely ground diet was greater (P less than .01) than in pigs fed cracked corn. The average daily gain of pigs receiving the finely ground diet was inversely related to ulcer incidence (r = .403, P less than .01, df = 59). The addition of 5, 10, 20 or 100 ppm of the H2-antagonist, metiamide, or 6, 18 or 54 ppm of SK&F 93479 to the finely ground diet did not improve pig performance or affect the incidence of gastric ulceration. The addition of 2, 6 and 18 ppm of SK&F 93479 to a corn-soy diet containing 4.5% alfalfa meal caused a reduction in gastric ulceration (P less than .05) and improved feed utilization by 3.2% (P less than .05). These data suggest that finely ground diets improve the performance of growing-finishing swine, but increase the incidence of ulcers in the esophageal region of the stomach. Severe gastric ulceration adversely affects swine performance. Feeding H2-antagonists does not reduce the ulcerogenic properties of finely ground diets, suggesting factors other than gastric acid secretion are involved in ulcerogenesis. The use of H2-antagonists in corn-soy diets improves feed utilization and reduces ulceration.

The level of protein in the diet both before and during treatment with beta-adrenergic agonist (BAA) was investigated with regard to its effect on growth performance and carcass characteristics of pigs. A total of 76 pigs were divided into two groups and given ad libitum access to diets containing either 12 or 18% crude protein (CP) during growth from 15 to 60 kg. At 60 kg, six pigs from each group were slaughtered and carcass composition was determined. For the test period (growth from 60 to 90 kg) the remainder of the pigs were divided into eight groups of eight pigs each. Half of the pigs from each of the two dietary pretreatment groups were switched to the other diet and half remained on the same diet. Of the four dietary groups, half were fed 0 mg/kg (controls) or 1 mg/kg of BRL 47672. During the test period, all pigs were fed at 90% of their calculated ad libitum DE intake. All pigs were slaughtered at 90 kg and carcass composition was determined. Addition of BRL 47672 to the diet resulted in an overall improvement (P < .05) in daily gain (.72 vs .64 kg) and gain/feed (.28 vs .26); the greatest improvement occurred with pigs fed the 18% CP diet (24 and 14% for daily gain and gain/feed, respectively). Pigs that had received BRL 47672 also had 12% less backfat, 10% less carcass lipid, 16% larger longissimus muscle area, and 5% more carcass protein (P < .05 for each), and the greatest changes occurred in pigs fed the 18% CP diet (-26, -16, +21, and +10%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

A feedlot growth-performance trial and a metabolism trial were conducted to evaluate a dose response to ardacin (a glycopeptide antibiotic). Treatments consisted of an 88% concentrate finishing diet supplemented to contain (DM basis) 0, 8.25, 16.5., or 33 mg ardacin/kg. The growth-performance trial (129 d) involved 120 heifers and 120 steers in a randomized complete block design. There were no interactions (P less than .10) between sex and response to ardacin. Average daily gain increased (P less than .05) and DM conversion decreased (P less than .01) with increasing levels of ardacin supplementation. At the 33 mg/kg level of supplementation, ADG and DM conversion were improved 10.6 and 5.6%, respectively. Four Holstein steers (344 kg) with cannulas in the rumen and proximal duodenum were used to evaluate treatment effects on characteristics of digestion. There were cubic effects of ardacin on ruminal starch digestion (P less than .05), microbial N synthesis (MNS, P less than .10), and microbial efficiency (MNEFF, grams of MNS/kilogram of OM fermented). For the 16.5 and 33 mg/kg levels of supplementation, ruminal starch digestion was increased 4.9%, and MNS and MNEFF were decreased 12.9 and 15.6%, respectively. Postruminal and total tract digestion of N increased linearly (P less than .10) with ardacin supplementation. Total tract digestion of OM, ADF, and starch were not affected (P greater than .10). Ardacin did not influence (P greater than .10) ruminal pH or molar VFA proportions. It is concluded that supplementation of a finishing diet with 33 mg ardacin/kg will enhance ADG and DM conversion of feedlot steers and heifers.