جستجوی مقالات مرتبط با کلیدواژه "feed restriction" در نشریات گروه "آب و خاک"

The purpose of this research was to evaluate the effect of early life nutrient restriction and subsequent intermittent lighting schedule on performance in broiler. In a factorial experiment, the effect of three levels of feeding regimes and two levels of lighting schedule were investigated using 480 day-old male Hubbard chicks. The broiler chickens were randomly distributed over two rooms consisting of 4 replicates of 20 birds for each of three treatment groups. From 3 to 12 days of age treatment groups were either allowed ad-libitum access, 90% or 80% to feed. From 12 days of age until 42 days of age all birds were allowed ad-libitum access to feed. The lighting schedule for day 12 onwards in one room was a 23h light (L): 1h dark (D) lighting schedule (CL) and another room with an intermittent lighting schedule (IL, 1L:3D) from 8 AM until 8 PM . The results indicated that feed intake and feed conversion ratio of birds reared in the IL schedule were significantly lower than CL , at growth and total period of experiment (p<0.01). IL schedule did not have any significant effect on mean body weight at the end of experimental period and body weight gain at total period of experiment(p>0.05). Relative growth rate and production (PI( in the IL were higher than CL schedule (p<0.01). Feed intake and feed conversion ratio of birds given 90 and 80% of ad libitum were significantly lower in comparison with control group (p<0.01). Body weight (gain) at the end of the experiment and growth period and body weight gain in birds fed 80% of ad libitum group were significantly lower in comparison with control and 90% of ad libitum groups. At 5,6 weeks and grower period EPI and relative growth rate in birds fed 80 and 90% of ad libitum were significantly higher in comparison with control. These results indicated that feed restriction and lighting program did not have any significant effect on carcass composition (protein, fat, ash and dry matter), carcass fragment percentage (except for drumstick), abdominal fat percentage, lung , heart, right and left ventricle weight and hematocrit percentage (p>0.05), but proportion of heart weight to body weight and drumstick percentage in birds fed 80 % of ad libitum were higher than the other groups (p<0.05). Lighting schedule and feeding regime did not have any interaction effect, except for relative growth rate (p<0.05). Relative growth rate in birds with feed restriction under IL schedule was higher than birds with feed restriction under CL schedule. Intermittent lighting and feed restriction had synergic, activity effect and positive effect on body weight gain and feed convertion ratio.

The effect of dietary protein level and feed restriction on performance, body temperature and hematological values was evaluated, using Ross 308 broiler chicks under heat stress. For this purpose, three dietary treatments were fed to broilers during 21 to 42 days of age. Two treatments consisted of diets with protein levels recommended by NRC, 1994 and 85% of NRC recommendation and were fed ad-lib during the experiment. The third treatment was a feed restriction group that was fed diet with protein level recommended by NRC, but chicks were deprived of feed for 6 hours during heat stress challenge. Birds had free access to water. Results indicated that lowering protein content or feed restriction had no significant effect on body weight gain (P>0.05). Feed restriction resulted in significantly decreased feed intake, improved feed conversion and energy efficiency ratio, and decreased body temperature after heat stress challenge at 24 and 32 days (P<0.05). Lowering protein of diet and feed restriction resulted in significantly decreased protein intake, improved protein efficiency ratio and increased hematocrit and blood uric acid (P<0.05). Sex had no significant effect on body temperature and hematological values (P>0.05). Heat stress significantly increased body temperature, hematocrit and glucose and uric acid values.

An experiment was conducted to determine growth and carcass characteristics of male broilers subjected to early feed restriction. Restricted birds were fed equivalent to 1/5*BW0.67 Kcal/day/bird between days 7 and 14. On days 0 to 7 and 14 to 56, all chickens received feed ad-libitum. Diets of feed-restricted birds were supplemented with 15% higher methionin and cystine recommended by NRC (1994) during refeeding in starter and grower periods. No significant differences were observed for liver, breast, heart, carcass and liver fat between early restricted birds and ad-libitum control at 56 days of age. Body weight for restricted broilers were significantly (P<0.05) lower than that of controls in 56 days. However, restricted broilers had significantly lower total-feed to gain ratio than the unrestricted control. Restricted broilers that received diets high in total sulfur amino acids in starter and grower periods had singnificantly lower abdominal fat pad than control birds.