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Published online by Cambridge University Press: 24 November 2017
The daily rate of lean deposition achieved by growing pigs is a function of a wide range of factors including genotype, gender, liveweight and intake of energy/protein. The review of ARC (1981) highlighted the controversy surrounding the effects of liveweight and energy intake on lean deposition. Recent publications suggest that there are interactions between these factors and also with genotype. In contrast to the linear/plateau relationship between energy intake and protein deposition proposed by Whittemore and Fawcett (1976), Campbell and Taverner (1988) observed a linear response in protein deposition up to the highest energy intake achieved, with pigs of improved genotype. The slope of the relationship was much greater than that observed in previous studies (ARC 1981). In a recent experiment, McCracken and Rao (1989) have shown that high-lean pedigree boars can achieve protein deposition rates as high as 200 g/d over the liveweight range of 33 to 88 kg. At present there is no published information on the response of such pigs to energy intake though the low rates of fat deposition observed suggest that energy intake could be limiting protein deposition. The experiment described below was designed to measure the response of protein deposition to energy intake at a series of liveweights between 33 and 88 kg. The diet and the treatments were chosen to obtain a wide range of energy intakes above and below those observed with dry, pelleted diets.