Efffects Of Lighting Regime And Nutrient Density On Performance, Sexual Maturation And Welfare Of Yellow-feathered Chickens

This experiment was conducted to investigate the effect of lighting regime and nutrient density ongrowth performance, carcass traits, meat quality, serum hormones and sexual maturation ofyellow-feathered broilers. One day old yellow-feathered broilers A4×3factorial arrangement of fourlighting regimes and three diets was used. Hatching (N=1440) were allocated to four rooms, eachcontaining12pens of30birds (male: female=1:1). All rooms were illuminated using20lx from d1tod7; thereafter, lighting regimes of16h (16L:8D), intermittent (3L:1D), variable (decrease-increase) and23h (23L:1D), were used, all at5lx. The three rations had the same ratio of CP/ME but differentnutrient densities were provided, ad libitum. until d90.1. There was no significant interaction effect between lighting scheme and nutrient levels.2. There were no differences among the four lighting groups for average daily gain (ADG) andaverage daily feed intake (ADFI). Broilers exposed to variable lighting group had the best F/G ratio(P>0.05). In addition, percent abdominal fat in females with variable lighting was significantly lowerthan in the intermittent lighting groups (P<0.01). Among the three nutrient densities, there was nodifference observed for ADG. The ADFI and F/G of low nutrient density group were significantly higherthan middle and high density group (P<0.01). Broilers fed the diet with high nutrient density hadsignificant higher dressing percentage than those in low levels (P<0.01).The variable lighting regimeimproved growth performance and carcass traits of broilers; increased nutrient density reduced F/G ratioand increased carcass quality.3. Testosterone levels of males were highest in the variable lighting group (P<0.05). There were nodifferences in growth hormone (GH) and melatonin (MEL) among the four regimes. In addition, theweight of comb and testis of males in the variable group were significant heavier than those in theintermittent and23h lighting groups (P<0.05). FSH concentrations in females fed the intermediate andhigh nutrient densities were significantly higher than in the low nutrient density group (P<0.05), whileno differences were found for GH and MEL. The comb and ovary weights of females in the highnutrient density group were significantly lower than those in the low nutrient density group (P<0.01).This indicated that the compensatory effect of variable lighting could promote the hormone secretionand sexual maturity of males; the intermediate nutrient density was sufficient for the growth anddevelopment of females.4、The a*values of males’ breast muscle from variable lighting was higher than the other threelighting groups (P<0.05), the opposite of which occurred in the L*values of female’s breast muscle anda*value of males’ breast decreased with the increase in of nutrient density (P<0.01). The shear force offemales’ breast increased with nutrient density (P<0.05). The results suggested that the variable lightingregime affected meat color and enhanced meat quality; high nutrient density led to dark redness anddecreased tenderness of meat, maybe ultimately affecting its taste.5、Eye weight tended to increase with hours of light. Broilers in the23h lighting group had theheaviest eyes and the most time spent resting, but they spent least time feeding, moving and comfortable behaviors; they had the highest gait score (P<0.05). This indicated that long day length could result in ahigher risk for broilers to get eye and leg diseases, which was detrimental for broiler welfare.In conclusion, the variable lighting regime, initially decreasing followed by increasing day length,was optimal for F/G, abdominal fat rate and sexual maturity. Increased nutrient density led to decreasedfeed consumption and F/G, increased dressing percentage, and promoted sexual maturation of females.On the basis of behaviors, gait scoring and eye weight, the23h lighting regime was detrimental foranimal welfare.