Effect of energy source ,protein level and seasons on broiler performance

Abstract

Four experiments were conducted at the Animal Production Department of the College of Agriculture and Natural Resources, Kassala University (New Halfa) to determine the effect of dietary protein level, cereal grain type and season of the year on the general performance and broiler carcass characteristics during the whole experimental period (7 – 42 days). The experiment was designed on factorial arrangement of three protein feed levels 20, 22 and 24%, three cereal grain types (sorghum, yellow corn (Shamia) and Millet) for two Summers and two Winters combinations. Summer trials were conducted during the monthes April – May 2008 and 2009 and the Winter trials during the monthes January – February 2009 and 2010. All the feed rations were iso-caloric of 3200 Kcal/ Kg feed in all the four feed rations. During the period 1 – 7 days and for all the trials only one commercial feed was offered (Pre-starter) which contained crude protein 23% and ME 3100 Kcal/ Kg. After that the birds were distributed randomly into nine groups of thirty chicks each and in three replicates for each of the four experiments giving a total of 1080 unsexed Hubbard chicks. By the end of the experiments at 42 days 12 birds were slaughtered from each trial to examine carcass characteristics and some commercial cuts. The results, at the termination of the trials showed that the final body weight and weight gain were better for the Winter raised birds at (P< 0.05) than those raised in summer. The statistical analyses for the final weight and weight gain showed statistical significance for the birds fed rations that contained 22% and 24% CP as they gave higher weights than those fed on the lower protein 20%. The analyses also, showed statistically significant difference for the final weight and weight gain for the birds fed different cereal types. Sorghum recorded the least final weight and weight gain while both millet and yellow corn gave the better results without any significant difference between them. The study indicated the effect of season on feed consumption during the experimental period, as the birds reared in winter consumed more feed than in summer at a significance level of (P< 0.01). For the effect of feed protein levels the study indicated that birds fed on 20% CP ration consumed significantly less feed than the 22% and 24% levels. The type of cereal grain used had significant effect on feed consumed as sorghum registered the least consumed feed ration compared with millet and yellow corn which both did not show any significant difference between them. The trials showed that feed efficiency and feed conversion were affected by season as birds raised in winter showed significantly better conversion than birds raised in summer. Feed protein level showed statistically significant effect on feed conversion as it indicated improvement with increasing protein ratio in the feed as 24% increased total feed conversion in respective of cereal grain type. It also showed the best weekly feed conversion which was best in the third week in respective of season or protein level or the cereal type under study. For feed conversion and energy source there was no significant difference between millet and yellow corn but sorghum showed lower effect at (P< 0.01) level comparatively which indicates that the cereal grain types or energy source in the feed rations has significant effect on feed conversion. The study of carcass characteristics indicated dressing percentage and some cuts which contained the breast, thigh and drum stick and also the abdominal fat and liver weight at the end of the experimental trials (42 days). The dressing percentage showed statistically significance differences due to season, protein level and cereal type effects. For cuts the results indicated that the thigh was affected by season and protein level, the drum stick was statistically affected by the protein level and cereal type. Liver relative weight was affected by cereal type only. The abdominal fat was not affected by season or protein level in the diet but cereal type showed statistically significant effect when the sorghum ration showed the highest weight for abdominal fat among the feed ration. The economic analysis indicated differences in total income and net returns due to season of the year, protein level and used cereal types. Sorghum rations had the least total cost but the net return out of it was not the best. The study showed that the best profitability was from the yellow corn and protein ratios of 22 and 24% compared with the other feed rations.