Artificial induction of lactation in heifers aged from 6 to 7 months

The rates of successful gene's manipulations are very low in domestic mammals. In addition the period between generations in cows is long. Artificial induction of lactation in young animals could improve manipulation yield for genes what are expressed in the udder, by anticipating the control of transgen expression in milk, a long time before the beginning of the milk production in normal condition. Using this method, the early selection of real transgenic animals would be possible. Between November 1999 and April 2000, lactation was induced in non-transgenic heifers aged from 6 to 7 months, in 2 trials based on short time hormonal treatment, with the goal of verifying the efficiency of the technique on immature heifers, and setting up a simple and reliable treatment scheme applicable on young animals. Interesting lactations (35 to 974 ml/day) were obtained, but the milk yield was low compared to adult performances. Results of the 2 trials were different, in relation with the galenical form of progesterone used and the frequency of drugs administration. So, these trials provide an efficient treatment scheme for induction of lactation in young heifers