The effects of dietary protein concentration on the lactational performance of the rabbit

Abstract

ABSTRACTAn experiment was performed to examine the effects of feeding four concentrations of crude protein in the diet to lactating rabbits. Diets A, B, C and D contained 173, 181, 224 and 243 g crude protein per kg dry matter respectively. Each diet was offered at one of two feeding levels: H (330 g/day) or L (280 g/day) with three replicates in each of the eight treatment groups. Milk production and nitrogen balance were measured over a 28-day lactation.Although dry-matter intakes on feeding level H were significantly higher than those on feeding level L the difference diminished as the crude protein concentration decreased. The effect of crude protein intake on doe milk production was estimated therefore by regression analysis with digestible energy intake as a covariate. Both crude protein intake and digestible energy intake alone had significant effects (P < 0·001) on daily milk production and there was also a significant effect (P < 0·05) of crude protein intake after fitting digestible energy intake. Overall the equation was:Milk production (g/day) =17·61 + 0·985 crude protein intake (g/day) + 30·3 digestible energy intake (MJ/day).(±0·448) (±14·8)The relationship between digested nitrogen and nitrogen output as milk was also examined by regression analysis with digestible energy intake as a covariate. This equation was:Nitrogen output in milk (g/day) =0·438 + 0·164 digested nitrogen (g/day) + 0·572 digestible energy intake (MJ/day).(±0·068) (±0·294)The practical implications of feeding high levels of crude protein in the diet to increase milk production and pup weaning weight are discussed.