Impact of Body Weight of Rabbit Does at First Mating
A recent study was conducted on the relationship between doe body weight at first mating and future body development and reproductive performance. The researchers wanted to determine if does that are heavier at a fixed age of first breeding have an advantage over smaller does. Rabbit does experience a severe energy deficit during their first lactation. Does tend to lose weight after weaning their first litter until the kindling of their second litter. This is due to the high energy needs of fetal growth combined with the doe's drop in feed intake during the last 10 days of gestation. This weight loss by first litter does accounts for a drop in reproductive performance and a high replacement rate of young does. The percentage of does successfully breeding on first insemination for their first two litters was close to the same for all three weight classes used in this experiment (heavy, medium and small size does). "The percentage of does that kindled after the first insemination at 14.5 weeks of age and after the first inseminations 10 to 12 days after kindling in the first and second parities (kindlings) was 38.1, 38.6, and 37.7% for heavy, medium, and small does respectively".
Does were bred at 14.5 weeks of age and placed in three groups based on their body weight; small (<3500 g), medium (3,500 to 4,000 g) and heavy (4,000g and more). Heavier does at first breeding had 2.5 more kits per litter than the group of small does. After weaning two litters no difference in culling rate of does was observed between the different sized does. Does were culled for several reasons after being bred at 14.5 weeks of age. These included being nonreceptive, nonpregnant, did not nurse their kits, metritis, mastitis, diarrhea, and badly formed teeth. All three sizes of does followed the same cycle for body weight loss and gain during reproduction and lactation during the first two litters. Does remained in the weight class they were first placed in throughout the first two lactations. Heavy does were not heavier because they were laying down more fat. They had the same body composition (proportion of muscle to fat) as the small weight group. Heavier does had 25% higher feed intake and 25% higher growth potential.
At 16 days of age the kits from heavier does tended to be larger. Heavier does produced more milk, but this higher level of milk production did not produce larger kits at weaning. The kits of smaller does consumed more pelleted feed. By weaning, at 30 days, there was no significant difference in the kit's weights from all three doe weight classes.
Researchers were hoping heavier does at first mating could benefit from extra feed intake capacity and store extra amounts of body fat to help them through times of energy deficit. This would lead to a decrease in the culling rate of young does. They concluded doe weight at 14.5 weeks of age was based on differences in voluntary feed intake and growth potential during rearing. Feed intake during reproduction is not improved by doe weight and no differences in body weight development (increase in depositing of fat) occur during reproduction. Heavier does had more kits in the first litter and may pass on to their offspring the genetic potential for faster growth but they have no advantage over smaller does when it comes to reproductive performance. There was no impact made by the body weight of does at first mating since no difference was found between weight groups for does culled during reproduction or does kindling to the second insemination.
Rommers, J.M. R., Meijerhof, J.P.T.M. Noordhuizen, and B. Kemps. 2002. Relationships between body weight at first mating and subsequent body development, feed intake, and reproductive performance of rabbit does.
J. Animal Science 80:2036-2042.
For more information:
Toll Free: 1-877-424-1300