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A comparative slaughter technique was used to determine the effect of dietary protein levels on body composition and protein and fat accretion in various body components in Yorkshire gilts. Diets were formulated to contain similar levels of idea protein. Eight gilts were slaughtered at 20 kg BW to determine initial body composition. Twenty-four gilts were assigned to each of three dietary treatments (16.6, 15.0 and 13.0% CP) during the growing period (20 to 55 kg BW). During the finishing period (55 to 100 kg BW), dietary CP levels were reduced by approximately two percentage units. Eight gilts per treatment were slaughtered at 55 kg BW, and the remaining pigs were slaughtered at 100 kg BW. At slaughter, the pits were divided into three components: carcass, empty gastrointestinal tract, and other non-carcass parts. Half of the carcass was further dissected into retail cuts. None of the carcass retail cuts was affected (P > .10) by the dietary CP levels, except trimmed ham was smaller (P < .05) in gilts fed the 13% CP growing and 11% CP finishing diets. Far content in the empty body (P = .12) and in the carcass (P = .06) was highest and the empty body water accretion rate was lowest (P = .05) in gilts fed the 13% CP growing and 11% CP finishing diets. Other aspects of chemical body composition, protein and fat accretion rates, and estimated lean yields were not affected by dietary CP level (P > .10).

A study was conducted to investigate the growth response of growing indigenous chickens between 14 and 21 weeks of age to diet protein level. The chickens were offered diets ad libitum with 100, 120, 140, 160 and 180 g crude protein (CP)/kg diet. Body weight and feed intake of the birds were recorded weekly. Feed intake and weight gain increased significantly between the 100 and 160 g CP/kg diets where-after they plateau. Feed efficiency measured by feed conversion ratio improved with increasing dietary protein level up to 160 g CP/kg after which there was no further improvement. It is concluded that the CP requirements for these chickens between 14 and 21 weeks of age is 160 g /kg.

Thirty six young New Zealand white rabbits were used in a randomised complete block (RCB) design with a 3×2 factorial treatment experiment to study the suitability of sorghum as substitute for maize in the diet of growing rabbits in Kenya. Six different diets were formulated to contain 35% of one of the three different types of grain (maize, white sorghum or brown sorghum) and one of the two different levels of crude protein (CP) 16 or 18.5% and fed to growing rabbits for a period of six weeks. The tannin content of the grains was 0.05, 0.52 and 5.6% chatechin equivalents for maize, white and brown sorghum respectively. Weaning weight at 35 days of age was used as the blocking criterion at the beginning of the experiment. Results of feed intake, weight gain, feed conversion efficiency, feed digestibility, as well as the blood parameters, indicated that white sorghum was not significantly different from maize. Animals fed on diets containing brown sorghum had a lower average daily gain (ADG) and a poorer feed conversion efficiency (FCE) (p<0.01) in comparison with those fed on diets containing maize or white sorghum. The 18.5% CP level gave a better FCE (p<0.05) compared with the 16% CP level. However, increasing the level of CP did not improve the utilisation of any of the grains. It was concluded that white sorghum could effectively substitute maize in the diet of growing rabbits. On the other hand, the use of brown sorghum in the diets of growing rabbits may compromise their growth rate. This may be due to the high concentration of tannins in the brown sorghum.

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