Development of the salivary secretion and the metabolic activity of the parotid gland in young calves

Abstract

Six calves were reared on milk (M) and another 6 on milk, hay and grain (MHG). Two calves were taken from each group at 1, 4 and 13 weeks of age, one parotid duct was cannulated under local anaesthesia and the rate of secretion was measured. The calves were then killed, the parotid glands were removed and weighed, and slices of gland were incubated with acetate, propionate, butyrate or glucose as substrate. The parotids of the MHG calves were heavier than those of the M calves at 13 weeks. The rate of secretion per g dry tissue developed rapidly in the MHG calves, increasing sevenfold between 1 and 13 weeks of age, but scarcely increased at all in the M calves. The rate of acetate utilization per g dry tissue increased rapidly in the MHG calves and less rapidly in the M groups. Changes in propionate and butyrate utilization were less clear. Glucose utilization showed no sustained change with age in either group. Oxygen uptake increased sharply between 1 and 4 weeks of age in gland tissue of the MHG calves but showed only a slight increase in that of the M calves. The development of parotid function in the MHG calves was related to the onset of rumen function and acetate absorption.-R. N. B. K.