Energy and nutrient intake on white striping, wooden breast and carcass composition in broilers from three genetic lineages at different ages

Increased incidence of myopathies and/or changes in broiler carcass composition leads to poor visual appearance and carcass condemnation on the slaughter line, or even subsequent consumer product rejection, consequently, economic losses. This study,was set to assess the incidence of white striping (WS), wooden breast (WB) and the carcass composition of three different genetic lineages of broilers fed with three different dietary nutrient densities. The experiment was con-ducted with a 4320 broilers, in a completely randomized, 3 x 3 factorial design, assessing three genetic lineages (Embrapa 021 - moderate growth, Cobb 500 and Ross 308 - rapid growth) and three dietary nutrient densities (ND): low, medium and high. Pelleted feed and water were consumed ad libitum. Daily digestible lysine intake (DdLysI - g/d), daily apparent metabolizable energy (DAMEI - kcal/d) and average daily weight gain (ADWG -g/d) were recorded for each evaluation period. At the ages of 28, 35, 42 and 49 days, 16 animals per treatment were slaughtered and submitted to WS, WB and carcass composition analysis. Ordinal logistic regression was used to analyse the WS and WB data. DdLysI, DAMEI, ADWG and carcass composition data were subjected to analysis of variance and the means compared by Tukey's test at a 5% significance level. An interaction effect (P < 0.05) showed that broilers from Embrapa 021 presented lower DdLysI and DAMEI from 1 to 35, 42 and 49 days, as well as lower ADWG for every period, regardless of the dietary ND. The lowest incidences of WS and WB were found for Embrapa 021 lineage, regardless of diet, compared to the other lineages (P < 0.05). There was an interaction effect for the carcass composition at 49 days for moisture, protein, fat and collagen (P < 0.05). At 28, 35 and 42 days the animals on the High ND diet had a higher moisture and protein content, and lower fat content. In relation to the genetics, the Embrapa 021 lineage displayed lower moisture and protein content and higher carcass fat content. The rapid growth broilers are more susceptible to developing breast muscle myopathies and present higher moisture and pro-tein content and lower fat content in the carcass. High dietary nutrient density results in a higher moisture and protein content in the carcass.