INDUCTION HORMONALE DE NAISSANCES GÉMELLAIRES : PRINCIPALES CONSÉQUENCES SUR LES PERFORMANCES ZOOTECHNIQUES

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Abstract
The possibility of using PMSG [pregnant mare''s serum gonadotropin] to enhance the multiple birth rate was studied on 256 lactating French Frisian Black and White cows in SW France. The calf crop was reduced by the presence of brucellosis (45.7% of the herds) and by the fact that one of the bulls used for the artificial insemination [AI] exhibited fertility disorders. The gestation rates after one AI and for the overall campaign varied from 45.8-66.2% and from 88.3-94.1%, respectively. The rate of calves born varied from 118-188%. In the best group (high PMSG level, bull with normal fertility), 129 calves were obtained from 100 treated cows. The calves from multiple births were lighter and born earlier (reduced gestation length) than those from single births, but these differences could be reduced by the choice of the bull used for the AI and by overfeeding of the cows during late gestation. Growth rates till the age of 300 days were not significantly different from those of the single-born calves. No significant effect was observed either on the fertility of the cows after multiple births or on the milk production during or after multifetal gestations.