Effect of dietary treatments on body fat level in broiler chickens
Kabuage, L W
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Three experiments were carried out to evaluate the effect of dietary calorie:protein (C:P) ratio and diammonium citrate (DAC) on abdominal fat content and performance in broiler chickens. In Experiment one, a narrow C:P ratio diet was fed to four groups of day old broiler chicks for the first one, two, four or six weeks of age, fol lowed by feeding a wide C:P ratio diet up to eight weeks of age. In Experiment two, chicks were fed on a pre-experimental commercial starter diet up to four weeks of age. At the start of the fifth week, they were randomly put under four dietary treatments consisting of feeding an experimental narrow C:P ratio diet for 0, 1, 2 or 3 weeks, followed by a commercial wide C:P ratio diet up to the eighth week of age. In Experiment three, a narrow C:P ratio diet was fed to all the chicks up to four weeks of age. From the fifth to the eighth week of age, the chicks were randomly put under four dietary treatments comprising:- i) a narrow C:P ratio diet containing intact protein ii) a similar diet but with an equivalent of 4% protein replaced by DAC iii) a wide C:P ratio diet containing intact protein iv) a similar wide C:P ratio diet but with an equivalent of 4% protein replaced by DAC. xiv Results at eight weeks of age showed that chicks that were fed on narrow C:P ratio diets for the shortest duration gave higher (P)0.05) abdominal fat than where such duration was prolonged. Mean abdominal fat pad weights were 42.52 g, 17.64 g and 41.93 g in Experiments one, two and three respectively. No differences (P)0.05) occurred between the sexes. There were no differences (P)0.05) in body weight and feed efficiency in Experiment one. Chicks that were fed on a wide C:P ratio diet for the longest duration in Experiment two gave a lower (P<0.05) body weight and poorer (P<O.OS) feed conversion efficiency. Chicks that received a narrow C:P ratio diet (without DAC) up to eight weeks of age in Experiment three gave a higher (P<0.05) mean body weight (2043 g), the highest in the study. Mean body weights attained in Experiments one, two and three were 1648 g, 1433 g and 1835 g respectively. No differences (P)0.05) occurred in feed intake in any of the three experiments. Males were on the whole heavier than females. Diammonium citrate (DAC) was close to intact protein in reducing fat level in the narrow C:P ratio diet but inferior in promoting weight gain. A similar comparison in the wide C:P ratio diets showed that DAC failed to reduce abdominal fat but effectively supported growth. High protein intake from prolonged consumption of the narrow C:P ratio diets may have caused a relative shortage of carbohydrate in the body and increased heat increment from metabolism of excess protein, consequently reducing lipogenesis. DAC might have been utilised to form dispensable amino acids whose metabolism effectively decreased lipogenesis in the high protein diet, supported weight gain in the low protein diet and depressed feed intake in both diets.