The effect of dietary protein on breast meat yield of broilers reared on different daylengths
The objective of the trial reported here was to determine whether breast meat yield would improve in broilers reared on short daylengths if higher levels of dietary protein were fed. To that end, 3200 Ross 308 International broilers were reared to 35 d in eight light-tight rooms, each room being divided into four pens which were populated with 100 feather-sexed male or female chicks. The lighting treatments used were 12, 16, 20 and 24 h light/d, and four balanced protein levels, being 0.85, 1.00, 1.15 and 1.30 of the Aviagen amino acid recommendations, were fed. At 35 d, three birds from each pen were sacrificed for measurement, individually, of physical and chemical characteristics. Body weight gain to 35 d was unaffected by both dietary protein content and light. FCE increased with dietary protein content to day 21. Feed intake to day 35 was not influenced by light or by dietary protein content. Birds on 24 h had a higher mortality compared with those on the three other lighting programmes, which did not differ from one another. Body protein content increased with both daylength and dietary protein content whereas body lipid content was influenced (decreased) only by dietary protein. Breast meat yield from birds reared on 12 h was not improved when these birds were fed high protein feeds whereas yields were increased in birds on the three longer daylengths used when feed protein was increased. The decreased breast meat yield in broilers given short daylengths is therefore not the consequence of a shortage of dietary protein.
Keywords: Thigh, drum, wing, carcass yield