Breed, heterotic and diet effects on postweaning litter growth and mortality in rabbits

The effects of sire breed, dam genetic group and diet on postweaning litter growth and mortality were evaluated in 208 litters of rabbits. Sire breeds were New Zealand White (NN), California (CC) and Flemish Giant (FG). Dam genetic groups were NN and CC straightbred and California 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 less than .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 (less than 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 less than .05) in litters reared by NN vs CC straightbred dams.(ABSTRACT TRUNCATED AT 250 WORDS)