Effects of light regimen and nutrient density on growth performance, carcass traits, meat quality, and health of slow-growing broiler chickens

Abstract

The present study was conducted to examine the main and interactive effects of 4 light regimens [16h light (L):8h darkness (D), 23L:1D, decreasing-increasing (Dec-Inc), and intermittent lighting (3L:1D)], and 3 dietary nutrient densities (low-, medium-, and high-density) on the growth performance, carcass characteristics, meat quality, and health of slow-growing broiler chickens (Beijing-You). A total of 14401-d-old broiler chickens were assigned to light regimens and nutrient densities in a 4×3 factorial arrangement of treatments with 4 pens per treatment and 15 males and 15 females per pen. Body weight and accumulated feed intake were determined on d 28, 56, and 91. The gait score (GS) was recorded to assess leg health on d 91. Two males and 2 females from each pen were randomly selected and processed to determine the weight of eviscerated carcass, breast muscle, thigh muscle, and abdominal fat. Meat quality was determined using the breast fillet. The ovary, testis, and comb were weighed, and the serum follicle stimulating hormone (FSH) and testosterone concerntration were determined for females and males, respectively. There was no interaction for any of the response criteria except for feed conversion ratio (FCR) from d 0 to 28 (P=0.014). The ADFI from d 56 to 91 of broiler chickens under 16L:8D regimen were greater than other 3 regimens (P<0.05), and they had larger testis and comb percentage and greater testosterone concentration than those under 23L:1D regimen (P<0.05). The broiler chickens under Dec-Inc regimen deposited less abdominal fat than those under 3L:1D and 23L:1D regimens (P<0.05), and they had larger testis and comb percentage and greater testosterone concentration than those under 23L:1D regimen (P<0.05). The ADFI and FCR from d 0 to 91 were affected by diet nutrient density, with medium- and high-density resulted in lower ADFI and FCR (P<0.05). The females fed the medium- and high-density diets also had greater ovary percentage and FSH concerntration (P<0.05). These results indicated that medium-density diet is the most appropriate for slow-growing broiler chickens. The 23L:1D regimen did not show any superiority on the improvement of feed conversion or meat quality. The Dec-Inc regimen improved feed conversion and carcass traits and enhanced the development of sex characteristics. Therefore, the medium-density diet and Dec-Inc regimen are suggested for the slow-growing broiler chickens.