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Breed, Heterotic and Diet Effects on Postweaning Litter Growth and Morality in Rabbits¹

Oregon State University, Corvallis 97331

⁴ To whom reprint requests should be addressed.

Abstract

The effects of sire breed, dam genetic group and diet on postweanmg litter growth and mortality were evaluated in 208 litters of rabbits. Sire breeds were New Zealand White (NN), Californian (CC) and Flemish Giant (FG). Dam genetic groups were NN and CC straightbred and Californian x New Zealand White (CN) and New Zealand White x Californian (NC) reciprocal crossbreds. Litters were fed either a commercial diet or a 74% alfalfa diet. Litter size and weight at 56 d and litter gain (the difference between 56- and 28-d litter weights) tended to be lower in NN- compared with CC-sired litters; while feed intake was significantly lower and mortality was higher in progeny of NN sires. Litter 56-d weight, litter gain and litter feed efficiency (gain/feed intake) were improved (P<.05) in litters sired by FG vs NN or CC bucks. Direct heterosis (CN and NC compared with NN and CC litters) for litter size, growth and feed-related traits was generally low (< 11% in absolute value), while moderate heterosis levels (–21 and –22%) were observed for diarrhea-related and total mortality. Differences between NN and CC straightbred dams for litter size and weight at 56 d and litter gain were small, but in favor of NN dams. Diarrhea-related and total mortality were higher (P<.05) in litters reared by NN vs CC straightbred dams. Significant maternal heterosis was found for litter feed intake and efficiency (feed intake was increased and feed efficiency was poorer) and total mortality (difference of 5.5% and in favor of litters from straightbred dams) in litters. Litter size at 56 d was 1.29 rabbits larger in litters reared by CN vs NC crossbred dams; hence, litter 56-d weight, litter gain and feed efficiency were improved (P<.05). In addition, total mortality was reduced by 6.1% in litters of CN vs NC maternity. Litters fed the 74% alfalfa diet had larger litter size at 56 d and feed intake was increased compared with litters fed the commercial diet (P<.05). Mortality from diarrhea was higher on the 74% alfalfa diet (P<.05). Residual correlations revealed that in larger litters (more rabbits per litter), weight at 56 d, gain, feed intake and feed efficiency were improved. Weak relationships were observed between within-litter uniformity (coefficient of variation among litter mates for 56 d weight) and all other traits. Experimental results suggest the utilization of FG bucks and CN crossbred does to improve postweaning litter growth and feeding performance in meat rabbits.

¹ Tech. Paper No. 6611, Oregon Agr. Exp. Sta. and USDA Small Farms Project.

² Current address: Small Livestock Advisor, Heifer Project, Int., Bamenda Station, NW Province, Cameroon, W. Africa.

³ Dept. of Anim. Sci.

⁵ Lab. Anim. Resources.