The survival feeding of pregnant and lactating beef cows on all-sorghum grain rations: the effects of two levels of grain and early weaning of the calves

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Abstract
SUMMARY Forty-six cows in store condition (mean ± S.E. body weight of 366 ± 8 kg) were fed individually either 3 or 4 kg of coarsely rolled sorghum grain/head/day for the last 100 days of pregnancy and the subsequent 70 days after parturition. Eleven of the cows on each level of feeding had their calves weaned at 3 days of age. For the last 100 days of pregnancy, 3 kg of grain/head/day was an adequate ration for survival, but cows fed this ration lost a mean of 34 kg of body weight over this period compared to 8 kg by cows fed 4 kg of grain/head/day. Only 78% of the cows fed 3 kg grain/day survived to 70 days after parturition, whereas all cows fed 4 kg/day survived. There was a 44% incidence of retained placentae and metritis in cows fed 3 kg grain/day whereas those fed 4 kg/day had only an 18% incidence. Weaning of the calves at 3 days of age reduced the body weight loss of the cows by a mean of 40 kg over the first 70 days of lactation, but the effect was less for cows fed 3 kg grain (27 kg) than for those fed 4 kg grain (53 kg). Birth weight of the calves was not affected by the level of grain fed to the cows, but calves weaned and given 3 kg of milk/day plus a 50/50 creep of lucerne chaff and sorghum grain grew faster than calves not weaned and given only a sorghum grain creep. The omission of a source of calcium in the grain ration resulted in no apparent adverse clinical effects in the cows. The Na:K ratio of the saliva indicated that nine of the cows had been depleted of Na.