Bos indicus and Bos taurus crossbred dairy cattle in Australia. II. Effect of calf removal and prolactin treatment

Abstract

Some 70 % of filial generation Red Sindhi x Jersey and Sahiwal x Jersey crossbred animals were discarded from the dairy herd on the F. D. McMaster Field Station, CSIRO, because of failure to continue in lactation when separated from their calves. This well-known characteristic of Bos indicus cattle, generally referred to as 'maternal instinct,' has been assumed to emanate from the dam's sense of loss on separation from her offspring. Observations on animals in the Field Station herd suggested that this separation causes the dam to cease producing secretory hormones with consequent cessation of lactation. Two systems of management, in one of which the calf was separated from its dam within 24 hr of birth while in the other the dam and offspring were allowed to run together for 10 days, both failed to overcome the problem. Injections of oxytocin after separation were also unsuccessful. Some success was obtained by daily injections of 250 i.u. of prolactin for the 10 days immediately following the separation of dam and offspring, and it was concluded that the presence of the calf stimulated prolactin secretion by the pituitary. Continuation of injections over a period of 7-10 days enabled some animals to continue their lactation without the stimulation afforded by the calf.