The effect of a monensin ruminal delivery device on performance of cattle grazing pasture.

A total of 28 trials utilizing 2,262 steers and heifers were conducted to evaluate a sustained monensin2 ruminal delivery device (RDD) on the daily gain of grazing cattle. Five series of trials, with four to eight trials per series within a grazing season, were conducted to evaluate the daily gain response under different environmental conditions and locations. Pastures grazed included both summer (cool- and warm-season grasses and native range) and winter (rye, ryegrass and wheat) growing pastures. The experimental design for all trials in each of five series was a randomized complete block with initial weight or breed as the blocking factor. The treatments compared in series I, III, IV and V (20 trials) were a control and a single RDD, whereas in series II (eight trials), a 2 x 2 factorial was utilized that compared RDD and estradiol 17-beta controlled release implants. In the five series of trials, the monensin RDD increased daily gain .04 (P = .002), .03 (P = .07), .09 (P = .01), .05 (P = .10) and .08 kg (P = .04) compared with the controls. Use of the RDD provided an effective method of achieving consistent monensin delivery and weight gain improvement without requiring the extra labor needed to administer monensin via hand-feeding or self-feeding supplements, blocks or loose mineral.

Isolation-perfusion of ovine hind limbs. IV. Effects of level of activity on amino acid and glucose metabolism.

Twenty-one wether lambs averaging 30.0 kg were utilized in a study to determine the influence of level of muscular activity (via electrical stimulation) on metabolism of amino acids and glucose of isolated-perfused hind limbs. Treatments consisted of: (1) control, (2) low electrical stimulation and (3) high electrical stimulation. Mean perfusion flow rate was unaffected by treatment or time of perfusion. Perfusion pressure and hematocrit were increased (P less than .05) by stimulation. Glucose levels decreased from a pretreatment average of 44.7 to 41.3, 26.8 and 20.0 mg/dl for treatments 1 to 3, respectively. Lactic acid levels increased from the pretreatment mean of 37.7 to 46.7, 63.8 and 69.4 mg/dl, respectively. Plasma-free fatty acids were utilized from the perfusate at .84, .76 and .68 meq X liter-1 X min-1, respectively. Perfusate urea N levels were unaffected by treatment or time of sampling, but perfusate ammonia levels increased in all treatments (ammonia levels for treatments 1 to 3 increased by .50, 1.09 and 1.47 mg/dl, respectively). Perfusate amino acid changes suggested a flux of some amino acids from muscle to perfusate due to electrical stimulation, but perfusate branched chain amino acid concentrations decreased in all treatment groups. Fifty microcuries of 14C-lysine were included in the initial perfusate. Total perfusate radioactivity in all treatments declined with time, reflective of lysine uptake by the muscle. Total perfusate lysine concentration changed less markedly, suggesting that muscle is contributing to maintenance of plasma amino acid levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of monensin, estradiol controlled release implants and supplement on performance in grazing steers.

Five trials in five locations in the United States involving 512 steers were conducted to evaluate the effect of monensin [200 mg/d in .9 kg of supplement (Ru mensin )] and estradiol-controlled release implants ( Compudose ) administered alone and in combination on average daily gain (ADG) in steers on pasture. The effect of energy supplementation on rate of gain was also evaluated in these same trials. The initial weight of steers averaged 250 kg and the average duration of the five trials was 124 d. Estradiol-controlled release implants increased ADG by 15.6% (.095 kg/d; P less than .0001) and monensin increased ADG by 8.1% (.054 kg/d; P less than .05). The combination of estradiol-controlled release implant and monensin increased ADG by 27.4% (.168 kg/d). Treatment responses were additive relative to ADG response, with no interaction observed between the treatments. Nine-tenths kilograms of an energy supplement/d increased ADG by 12.4% (.073 kg/d; P less than .01).

Effects of monensin fed to replacement dairy heifers during the growing and gestation period upon growth, reproduction, and subsequent lactation.

Sixty Holstein heifers initially weighing 196 kg were assigned by weight to treatments of 0, 200, and 600 mg of monensin. These treatments were fed daily until calving to determine effects of monensin on growth rate, feed consumption, feed efficiency, reproductive performance, and subsequent lactation. Throughout the feeding period the control (0 mg) heifers received sufficient feed to allow a calculated growth rate of .68 kg/day. Monensin treatment groups were fed the same amount of the identical ration over the 448-day experiment. Daily gain, feed intake, and feed efficiency for the 0, 200, and 600 mg treatments were .60, .69, .69 kg, 7.47, 7.46, 7.43 kg, and 12.41, 10.81, 10.81. Although days on trial to first estrus were not different among treatment groups, heifers fed monensin at 200 and 600 mg/day conceived 38 and 34 days sooner than 0 mg heifers. Percent conception, number of calves born, calf birth weight, and calving difficulty were not affected by treatment. Milk production was measured for 120 days subsequent to the experimental feeding of monensin. During this period heifers were fed a common ration ad libitum. Milk production of 17.1, 16.9, and 17.0 kg/day for 0, 200, and 600 mg was not affected by prior treatment.