The use of oestrous cows for the pre-collection preparation of mature bulls standing at an artificial breeding centre : a thesis presented to the Victoria University of Wellington in partial fulfilment of the requirements of the degree of Master of Agricultural Science, Massey College, New Zealand
Since 1949, a marked expansion in the commercial operation of artificial breeding has taken place in New Zealand. This expansion represents an increase from 1,400 inseminated cows in 1949, to 556,000 inseminated cows in 1961. (New Zealand Dairy Prod, and Marketing Board Ann, Rept. (1962)). The principle objective of the Artificial Breeding Service is to offer farmers the use of top sires from each of the main dairy breeds in New Zealand. These sires are selected on the basis of progeny test records. The rating which each proven sire receives is calculated from the butterfat production records of a sire's daughters. The butterfat records of each daughter are corrected for are differences and compared with the age-corrected average production of the herd-mates. Bulls selected for use as A.B. sires are placed at one of the two Artificial Breeding Centres which provide a Dominion-wide coverage. Because of the seasonal nature of daily farming in New Zealand, the bulk of the demand for semen occurs during the spring mating period, and since chilled semen is the principle form of service offered, the bulls experience a peak working period of eight to twelve weeks at this tise of the year. Ths objective in development at the Centres has been to obtain maximum coverage from top sires compatible with satisfactory conception rates. In 1961, the 49-day non-return rate to first inseminations with chilled semen was 63/3% (New Zealand Dairy Production and Marketing Board Ann. Rept. (1962)).