Abstract:
HORMONAL INDUCTION OF LACTOGENESIS IN BULL CALVES GOLDA L. MUNRO* The major milk proteins, 9(5-casein,@-casein, k-casein and (g-lactoglobulin are all subject to genetic variation detectable by starch gel electrophoresis, These genetic variants can influence the amount of milk protein produced and the processing properties of the Thus there may be advantages in breeding . milk (Feagan et al, 1972). for particular milk protein genotypes. The ability to-breed a cow with known milk protein genetic variants ' is hampered by the fact that the milk protein genes transmitted by a sire can only be inferred by the genotypes of his daughters. Milk secretion in small quantities has been induced ifi bull calves of three and six months of age after six'weeks of treatment of alternating four day courses of oestrogenand progesterone (Table '1). A shorter treatme.nt of two weeks with daily doses of oestrogen and progesterone failed to produce milk, TABLE ? All milk obtained tias typed forp -1actoglobulin genetic variants. Only milk from bull 69 was successfully typed for the major casein variants. All casein gels showed unidentifiable protein bands which hampered typing. Microscopic examination of semen from bulls 2 and 38 at 15 months old revealed motile sperm. Further work needs to be done on hormone induction of lactogenesis in bulls to establish the optimum cond.itions for milk secretion, and on their subsequent fertility before recommendations on the use of typed bulls can be made. FEAGAN, J.T., BAILEY, L.F., HEHIR, A.F., MC LEAN, D.M. AND ELLIS, 27: N.J.S. (1972). The Australian Journal.of Dairy Technology= 129 *Northfield Research Centre, South Australian Department of Agriculture, Box 1671 G.P.O. Adelaide, South Australia, 5001. _ 33P