Three heifer development trials were conducted with 337 crossbred heifers (125, 105 and 107 heifers in trials 1, 2 and 3, respectively) over a 3-year period. Heifers were fed low quality fescue hay ad libitum plus 0, 1.22 or 2.45 kg of ground ear corn (GEC) daily during the winter feeding phase of all three trials. Winter gains and final winter and summer condition scores increased (P less than .05) in each trial as winter level of GEC increased. In each trial, summer gains followed the reverse order of winter gains (P less than .05). Conception rate, mean number of days pregnant (as determined by rectal palpation) and adjusted weaning weight of progeny increased linearly with winter level of GEC when pooled over trials. Differences between animals fed 0 and 2.45 kg of GEC were significant. Conception rate and adjusted weaning weight of progeny of the heifers retained in the breeding herd increased (P less than .05) as level of GEC increased when data were pooled over trials. Calving date and percentage live progeny were not significantly affected by winter treatment. Summer daily gains and condition scores were increased by additional summer energy (2.45 kg GEC/day) in trial 3. Conception rate and mean number of days pregnant (conception date) favored heifers given the summer supplementary feeding (2.45 kg GEC) treatment. Among heifers retained in the breeding herd, there were no significant differences between the 0- and 2.45-kg GEC summer treatment groups in conception rate, calving date, percentage live progeny or adjusted weaning weight of progeny.

The effects of exogenous histamine and ammonia on hypomagnesemia were determined in a 22 factorial arrangement of treatments with 16 ruminal fistulated lambs fed a semipurified low magnesium (.08%) ration and given intraruminal infusions of histamine, ammonia or histamine + ammonia and compared to a control receiving deionized water. Samples of blood and ruminal fluid were taken at the beginning and end of an 80-day trial and analyzed for histamine, electrolytes and ammonia, and ammonia and pH, respectively. One lamb in the histamine + ammonia group and two lambs in the ammonia group showed signs of hypomagnesemic tetany accompanied by low phosphorus levels. The two groups receiving ammonia had lower serum magnesium levels (P<.05) than the histamine or control groups. There was no treatment effect on serum calcium, potassium, phosphorus or ammonia levels. Blood histamine was higher (P<.05) in the group receiving histamine + ammonia. Ruminal ammonia levels were higher (P<.01) for the two groups receiving ammonia; however, no differences in ruminal pH were observed. These studies suggest that high levels of ammonia may be responsible for depression of serum Mg levels leading to tetany, but histamine has no effect. In the second trial, analysis of serum from range cows indicated no correlation between serum histamine and magnesium levels.

Two experiments were conducted to study the effect of supplemental selenium at levels of 0, .1, .2, or .4 mg/kg to a finishing beef catt le diet containing .08 mg/kg. In one experiment, an increase (P<.05) in gain was obtained from adding .1 mg selenium per kilogram. However, in a second experiment, no benefit was obtained from adding .1 mg/kg and supplemental levels of either .2 or .4 mg/kg resulted in a significant depression in rate of gain, indicating the range between sub-optimal and possible growth-depressing levels of dietary selenium for beef cattle may be quite narrow. Selenium levels in whole blood, serum or hair reflected levels of dietary selenium. (

Grass hay was packaged in large round bales, compressed stacks and small round bales in order to determine the amount of weather deterioration when stored outside. Wastage during feeding was also determined when large bales and compressed stacks were fed on pasture and in racks. Grass hay packaged in large round bales and compressed stacks and stored outside from June until November lost from 8.2 to 12.6% of its total digestible dry matter due to weathering. Small round bales stored outside lost 16.9% of their digestible dry matter due to weather deterioration. Weather damage was confined to the outside 2 to 4 inches (5 to 10 cm) of the large packages. When the large packages were fed to beef cows without a rack, or some other means of keeping the cows from trampling on the hay, dry matter needed per cow-day averaged from 23 to 39% greater than when the hay was fed in a rack.

TWO experiments were conducted to determine the optimum level of dietary urea in a purified diet for lambs. Experiment I consisted of a 62-day growth study and a nitrogen balance study with wether lambs. Experiments 2 consisted of a 62-day growth study and a metabolism study with induced cryptorchid ram (I.C.R.) lambs. Weight gains, feed and water consumptions, terminal plasma urea, plasma free amino acids, N-balance and digestible energy were measured. The diets studied were: (R-14) 31% glucose, 22% corn starch, 25% cellulose, 10.75% isolated soy protein, 1.66% urea, 3% corn oil, 6.59% minerals and vitamins; (U-14) R-14 diet, 5% urea, soy protein deleted; (U-19) U-14 diet, 6.75% urea; and (U-24) U-14 diet, 8.5% urea. Dietary crude protein equivalents (C.P.) were 14, 14, 19 and 24%, respectively. In Experiments 1, as the level of urea increased in the urea treatment diets, weight gains, feed consumptions, water intakes and terminal plasma urea levels increased linearly (P

Four experiments were conducted with fattening beef cattle to study the effect of supplemental zinc to natural rations containing from 18 to 29 mg. of zinc/kg. Levels of zinc compared ranged from 75 to 346 mg./kg. In two of the four experiments, significant (P<.05) increases in daily gain were obtained from supplemental zinc. Increased levels of zinc resulted in significantly (P<.05) increased levels of serum zinc in the presence of either 0.25% or of .50% calcium in the ration. However, doubling the level of supplemental calcium resulted in significantly (P<.05) lower levels of serum zinc. Based on 112 day data, the level of zinc in the hair reflected the level of zinc in their rations. Furthermore, doubling the level of supplemental calcium in the ration resulted in significantly (P<.05) lower levels of hair zinc, based on the 112 day sample. However, the 201 day collection of hair failed to reveal any differences in zinc content, regardless of levels of dietary zinc or calcium, or both, indicating a possible compensatory reaction had been made by the cattle.

Two trials were conducted with fattening calves to determine the comparative efficacy of oral (20,000 I.U. per day) and initially-injected vitamin A (1, 4 or 6 million I.U.). Both feeding trials covered a period of 210 days each. The rations contained a level of 1.5 mg. of carotene per kilogram. Both methods of administering vitamin A resulted in significant (P

Blood tissue and rumen fluid analyses on samples taken from lambs consuming 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5 or 4.0 gm. of supplemental zinc per kg. of diet or receiving 0, 2.0, 4.0 or 6.0 gm. of zinc per head daily via a stomach tube revealed: High levels of zinc intake resulted in large increases in serum and organ zinc; the largest changes occurred in the liver, pancreas and kidney. High levels of zinc altered copper and iron metabolism as evidenced by decreased liver copper and increased liver iron. High levels of zinc in the diet of lambs decreased hemoglobin and packed cell volume values, while dosing with 4.0 or 6.0 gm. of zinc daily caused an increase in hemoglobin and packed cell volume. Some changes occurred in the metabolism of other minerals, as evidenced by changes in the levels occurring in the liver and bone; however, the alterations were not consistent among the experiments. Connective tissue replacement of acinar tissue was observed in the pancreas of lambs fed from 1.0 to 3.5 gm. of zinc per kg. of body weight. High levels of zinc altered rumen metabolism, probably through its toxic effect on rumen organisms.