Studies on Carcass Traits, Nutrient Retention and Utilization of Koekoeck Chickens Fed Diets Containing Different Protein Levels with Iso-Caloric Ration

The study was conducted to investigate the effect of different levels of crude protein (CP) on some linear body measurements, carcass characteristics and nutrient retention of Koekoeck chickens. Two hundred chicks were randomly assigned to 4 treatment diets (T) containing 16% CP (T1), 18% CP (T2), 20% CP (T3) and 22% CP (T4). Each of the treatment groups were replicated 4 times with ten chicks per replicate. Linear body measurements (breast angle, keel length, shank length and body length) were taken at the ages of 3, 6, 9, 12 and 15 weeks. At the end of the experiment, a pullet and a cockerel after overnight fasting were slaughtered from each of the replicate to assess the carcass traits and nutrient retention,. Breast angle and keel length were higher for chickens fed T1 and T2 than those on T3 and T4. Positive (P < 0.01) correlations were observed between linear body measurements and body weight. The commercial carcass yield was significantly higher for chicks receiving T3 diet when compared to those reared on T1 diet. Cockerels receiving T3 diet had higher (P < 0.05) values for drumsticks, thighs, wings, breast and back. However, the pullets had higher (P < 0.05) weight for abdominal fat. Protein intake and retention increased linearly with the levels of crude protein and was higher (P < 0.05) among the chickens receiving T3 diet. The feed intakes and energy retention also increased with the levels of crude protein in the diet. The highest protein utilization efficiency was observed in the chickens fed on T3 diet while the lowest was among those reared on T4 diet. The values for energy utilization efficiency was highest among the chickens receiving T2 and T3 diets while the reverse was true for those reared on T1 diet. The intake of calcium was highest among the chickens receiving T2 diet whereas the levels of phosphorous were similar across all the treatments. It can be concluded that the amount of dietary crude protein levels which is most advantageous for Koekoeck chickens under tropical production environments is 18%.