Breeding of young females

This paper describes strategies for rearing of young rabbit does with the objective to improve reproductive performance and prolong lifespan. Body development during rearing was considered the main factor to influence subsequent reproduction. Body development was manipulated by feeding level during rearing (ad libitum or restrictive) and age of first insemination (14.5 and 17.4 weeks) and was determined at the end of rearing by body weight and body composition. Does fed restrictively and inseminated at 14.5 weeks of age were too immature for reproduction. In these does, body weight was low (3.2 kg), protein development was not completed, and puberty characteristics were poor. An optimum body weight at first insemination was found (around 4 kg) to optimize litter size. At 14.5 weeks of age and ad libitum feeding during rearing, over 70% of the does did not reach optimum body weight of 4 kg. Litter size of these does was reduced by 1.4 kit. At 17.5 week of age and ad libitum feeding during rearing, more than 75% of the does weighed at least 4 kg. However, heavy does were fatter, had a lower feed intake in the first gestation period, and the number of does with stillborn kits was increased. In restrictive fed does inseminated at 17.5 week of age, 60 to 80% of the does weighed around 4 kg, and the number of kits born alive was increased compared to does fed ad libitum during rearing and inseminated at 14.5 or 17.5 weeks of age. Milk production was influenced by the feeding strategy during rearing. Restrictive fed does inseminated at 17.5 week of age produced more milk than ad libitum fed does inseminated at the same age. This could be explained by the fact that restrictive fed does had not formed excessive fat depots at 17.5 week of age and had a higher feed intake as ad libitum fed does at the same age. Ad libitum fed does inseminated at 14.5 week of age, gained weight in the first gestation and first lactation period. Competition for nutrients between body growth and production must have occurred, and resulted in smaller litters and lower milk production than restrictive fed does inseminated at 17.5 week of age. It was concluded that young does should have a body weight around 4 kg at first insemination to optimize litter size. Feed restriction during rearing increased uniformity in body weight among does and stimulated feed intake in the first gestation period. The best reproductive performance in the first parity was obtained in does restrictively fed and inseminated at 17.5 week of age. Rearing strategies only affected body weight development, feed intake in the first parity. Long-term effects over three parities were absent and culling rate of does was not affected.