早期数量限饲对肉用仔鸡生产性能、胴体品质的影响

试验研究了早期数量限饲对肉用仔鸡生产性能、胴体品质的影响。以320只1日龄AA+肉用仔鸡为试验动物。设4个处理组,每个处理组4个重复,每个重复20只肉仔鸡。对照组根据AA+商品代肉鸡营养标准配制。各处理肉用仔鸡1～7日龄均为自由采食,8～14日龄对照组、限饲90%组、限饲80%组和限饲70%组分别饲喂自由采食量的100%、90%、80%和70%,15日龄恢复自由采食,以后按常规饲养管理。每周末,以重复为单位全部称重。分别于42、49日龄,每个重复随机抽取4只肉用仔鸡禁食12h、称重、屠宰、测定屠体品质。试验结果表明:在第2周,限饲各组肉仔鸡的体重和日增重分别显著低于对照组(P0.05);在第3周,限饲90%组完成补偿生长,体重与对照组差异不显著(P0.05);在第4周,限饲80%和70%组完成补偿生长,体重与对照组差异不显著(P0.05);5、6、7周及2～6、2～7周各组在体重、日增重、日采食量和饲料转化率等都无显著差异(P0.05)。早期数量限饲对肉仔鸡胴体特性没有显著影响(P0.05),限饲70%～80%,具有改善饲料转化效率、胸肌率、腹脂率的作用。     

早期限饲对肉仔鸡的影响

遗传育种选育和营养水平的改进,在使肉仔鸡生长速度不断提高的同时带来了一系列负面影响,如脂肪沉积、代谢性疾病、骨骼疾病、死亡率增加。早期限饲在改善这些问题上有一定的作用。本文综述了早期限饲对肉仔鸡的生产性能和健康状况等影响,并对早期限饲的进一步研究方向进行了展望。     

Effects of strain and different skip-a-day feed restriction periods on the growth performance of broiler chickens

The effects of 6, 10 and 14 days of skip-a-day feed removal during the starter and grower periods on the growth performance of Ross 308 and Hubbard broiler chickens were studied in a 49-day production period. Ross 308 was superior to Hubbard in weight gain, market weight and feed utilization but consumed more feed, deposited more abdominal fat and had a higher mortality rate. Overall, feed removal improved feed efficiency, had insignificant effects on abdominal fatness and mortality rate and reduced feed intake, weight gain and market weight. On each restricted-feeding regime, the birds gained as much weight as their fully fed counterparts during the period of resumed full feeding but were unable to compensate fully for the weight loss and were lighter at the end of the trial. It is suggested that for profitable broiler production under tropical conditions, Ross 308 and skip-a-day feed removal for less than 6 days from 7 to 17 days of age be considered.     

Effect of early-stage thermal conditioning and food restriction on performance and thermotolerance of male broiler chickens.

1. The effects of early-age thermal conditioning and food restriction on performance and thermotolerance were studied in male broiler chickens, in 2 trials. 2. Chickens were exposed to 36 degrees +/- 1 degree C and 70% to 80% relative humidity (RH) for 24 h at the age of 5 d (thermal conditioning, TC), or to food restriction (FR) at the age of 7 to 14 d, or to both treatments (TC+FR), while a control group was reared under standard conditions. At the age of 42 d, chickens were thermally challenged by a heat stress of 350 degrees +/- 1 degree C and 20% to 30% RH for 6 h. 3. In both experiments, weight gain of the TC chickens between the ages of 7 and 42 d was significantly higher than those of other treatments and was associated with higher food intake. 4. Early-age TC significantly increased body temperature (Tb). Thermal challenge at the age of 42 d markedly increased Tb in all groups but that of the TC groups was the lowest. 5. Mortality during thermal challenge was significantly lower in the treated chickens, except for the FR group in trial 2. 6. Plasma triiodothyronine (T3) concentration was greatly depressed in all treatment groups during the thermal challenge. However, the lowest concentration was observed in the TC group, suggesting that these chickens exhibit the lowest rate of heat production under such conditions. 7. Thermal conditioning reduced the increase of haematocrit with age, whereas food restriction resulted in an increase in haematocrit immediately after FR. Thermal challenge resulted in a haematocrit decline in all groups, with the lowest values in the TC and TC+FR chickens. 8. It can be concluded that, because the TC treatment improved thermotolerance (possibly by reducing heat production) and performance, it has advantages over the FR and TC+FR treatments.     

Early-life food restriction of broiler chickens. II. Effects of food restrictions on the development of fat tissue.

1. The physiological and metabolic effects of a short term food restriction of broiler chickens at an early age and grown to 49 d of age were examined. 2. Fat accretion was measured by tritium dilution. Adipocyte characteristics of the fat tissue were examined by cell counting after fixation with osmium tetroxide and the metabolic effects of food restrictions were measured by closed-circuit respiration calorimetry. 3. The success of food restrictions in allowing full bodyweight recovery and producing decreases in body fat was associated with a negative energy balance and a positive nitrogen balance achieved during the restriction phase. 4. Food restrictions produced decreases in body fat possibly by causing a delay in adipocyte hyperplasia. Excess dietary energy was then lost as heat until adipocyte hyperplasia re-commenced allowing the bird to store surplus dietary energy as fat. 5. A food restriction that allows full bodyweight recovery and maximum carcase fat reduction in the broiler chicken at 49 d may not be appropriate for birds grown for longer periods.     

Early and temporary quantitative food restriction of broiler chickens. 1. Effects on performance characteristics, mortality and meat quality

1. An experiment was conducted with broiler chickens to determine the effects of different early food restrictions, strain (Ross 508 and Hybro G) and sex on performance, mortality carcase composition and meat characteristics. 2. Birds were restricted to 80% or 90% of ad libitum intake for 4 d (80%-4 d-group and 90%-4 d-group, respectively) or 80% for 8 d (80%-8 d-group). All restrictions started on d 4. After the periods of restriction, all birds were fed ad libitum. 3. Only the 90%-4 d-group reached a final body weight not significantly different from, but lower than, the ad libitum group. The other restrictions were too severe to allow a sufficient 'catch-up'. 4. No significant differences in food conversion and total carcase fat content between groups were observed. Abdominal fat showed a tendency to increase due to the restrictions induced. 5. There was a slight trend towards a reduced mortality and of 'sudden death syndrome' but no clear effect of food restriction on number of chickens removed with leg problems. There was no significant decrease in uniformity of the flocks due to restriction. 6. The group 80%-8 d had a significant lower yield percentage. Cut-up parts and meat quality were not changed by restriction. Ross birds had a significantly higher proportion of breast meat than Hybro chickens. Meat of female chickens seemed to be paler than that of males, possibly because of the higher proportion of carcase fat. 7. Food restriction did not always give good results. However, a mild restriction (90% for 4 d) may offer some economic advantages over an ad libitum feeding regimen, mainly by reducing mortality.     

Response of broiler chickens and turkey poults to food restriction of varied severity during early life

1. Cobb male (7-d-old) and female (6-d-old) chicks and BUT male and female turkeys (7-d-old), were subjected to food restriction of varying severity for 7, 5, 10 and 7d, respectively. 2. The energy allowance was calculated to support from 0% to 75% of the growth rate typical of species, strain and sex. 3. In male and female broilers kept up to 56 and 50 d, respectively, a high rate of weight gain after the restriction period (refeeding period) overcame the growth retardation attributable to restriction, except in the birds which had been subjected to the most severe regimen. In the mildest regiments, body weights reached slightly higher values than those of the ad libitum-fed controls. Overall food conversion efficiency was significantly improved in males and abdominal fat content was reduced in both sexes, regardless of the severity of restriction. 4. Body weights of male and female turkeys, aged 147 and 112 d respectively, of the groups subjected to the milder (75% growth) restriction, significantly exceeded those of the controls. Food conversion efficiency and meat yield were improved by early-age food restriction but carcase fat was not affected. 5. The results for both species of either sex suggest that a mild food restriction applied at an age of about 1 week and allowing for 60 to 75% of normal growth, may offer an economic advantage over a continuous ad libitum feeding regimen.     

Effect of clinoptilolite on performance of broiler chickens during experimental aflatoxicosis

1. The amelioration of aflatoxicosis in broiler chickens was examined by feeding 2 concentrations of natural zeolite (clinoptilolite). Clinoptilolite (CLI), incorporated into the diet at 15 and 25 g/kg, was evaluated for its ability to reduce the deleterious effects of 2.5 mg total aflatoxin (AF; 76.40% AFB1, 16.12% AFB2, 6.01% AFG1 and 1.47% AFG in diet on growing broiler chicks from 1 to 21 d of age. A total of 360 broiler chicks were divided into 6 treatment groups (6 replicates of 10 broilers each): control, AF, CLI (15 g/kg), AF plus CLI (15 g/kg), CLI (25 g/kg), and AF plus CLI (25 g/kg). 2. Compared to controls, the treatment had significantly decreased body weight gain from week 1 onwards. The adverse effect of AF on food consumption (8.0%) and food conversion ratio (8.3%) was also shown over the entire 21-d feeding period. 3. The addition of CLI (15 g/kg) to an AF-containing diet significantly reduced the deleterious effects of AF on food consumption and body weight gain. Food conversion ratio was also slightly improved by adding CLI (15 g/kg) to AF-containing diets. Food consumption, body weight gain and food conversion ratio values were rendered numerically intermediate between AF and control groups by the addition of CLI (25 g/kg) to the AF-containing diet. 4. The addition of CLI (both 15 and 25 g/kg) to the AF-free diet did not produce any significant changes compared with the controls, except for decreased total food consumption in the CLI (25 g/kg)-alone group. 5. These results suggest that CLI (15 g/kg) addition effectively diminished the detrimental effects of AF on the values investigated. Also, the lower dietary concentration of CLI (15 g/kg) was more effective than the greater concentration against the adverse effects of AF on the variables investigated in this study.     

Early and temporary quantitative food restriction of broiler chickens. 2. Effects on allometric growth and growth hormone secretion

1. An experiment was conducted with male broiler chickens to investigate the effect of different early food restriction programmes on proportional weights and allometric growth coefficients of carcase parts and on pulsatile growth hormone secretion. 2. At 4 d of age the animals were restricted to 80% or 90% of the ad libitum intake for 4 d or 80% for 8 d. When the restriction was finished, all birds received ad libitum food again. 3. On d 1, 8, 11, 14, 21, 28, 35 and 42, from each group 8 birds were weighed, stunned and killed and the weights of the stomachs, liver, heart, sternum, right thigh, right drumstick, breast and abdominal fat pad were determined. On d 29, 30, 31, 32 serial blood samples of 2 birds from each group were taken to determine the plasma growth hormone (GH) content. 4. Only the most severe restriction resulted in a tendency for the stomachs to mature earlier and the thighs to mature later. No other significant effect on the allometric coefficients could be observed. 5. It is concluded that during the restriction the birds give priority to the development of the supply organs such as the stomach, which are more important during early development at the expense of the demand tissues like breast and thigh. 6. No significant differences concerning the GH secretory parameters could be observed.     

Effects of increasing photoperiod length on performance and health of broiler chickens

1. Broiler performance and health were compared from 0 to 42 d for lighting programmes consisting of near-continuous light 23L:1D (23L), a lighting programme where photoperiod gradually increased from 6 to 23 h between days 4 and 35 (INC) or an increasing-lighting programme with 1 h of light mid-way through the scotophase (INC + 1). 2. The increasing lighting programmes reduced growth rate and increased gain:food ratio from 0 to 21 d; INC + 1 growth rate was intermediate to the 23 L and INC treatments. From 0 to 42 d there were no differences in growth rate or gain:food ratio among lighting treatments. Males grew faster, ate more food and converted food more efficiently than females. 3. The increasing-lighting programmes (INC and INC + 1) resulted in less skeletal disease than the 23L control. The incidence of sudden death syndrome (SDS) and mortality other than SDS were numerically lower for the increasing lighting treatments. More males died as a result of SDS and were affected by skeletal defects than females. 4. In terms of health, increasing lighting programmes were superior to near-continuous light for broiler chickens.     

Influence of early quantitative food restriction on long bone growth at different environmental temperatures in broiler chickens

1. This investigation was carried out to study the influence of early quantitative food restriction (40% of ad libitum intake from 7 to 14 d of age) and environmental rearing temperature (thermoneutral, cold and hot) on long bone (tibia, femur and humerus) development in broiler chickens. 2. Tibia, femur and humerus were obtained at the ages of 14, 21, 28, 35 and 42 d, and the variables studied were: length and width (mm, expressed as absolute values), bone breaking strength (kgf) and bone weight/bone length index (BW/BL, mg/mm). 3. All bone variables increased with bird age. Food restriction reduced bone length and width but did not affect bone weight. High environmental rearing temperature reduced bone length and width at 42 d of age. Bone strength was not affected by environmental temperature but the calculated BW/BL index was reduced by heat exposure. 4. The findings suggest that food restriction and high environmental rearing temperature reduce long bone growth; bone breaking strength was affected by bird age but not by food restriction nor rearing ambient temperature.     

The effect of early-age food restriction on heat shock protein 70 response in heat-stressed female broiler chickens

1. This study was conducted to determine the effect of early-age food restriction on heat shock protein (hsp) 70 synthesis in the brains of female broiler chickens exposed to high ambient temperatures. 2. Chicks were brooded for 3 weeks and then maintained at 24+/-1 degrees C. 3. On d 0, chicks were assigned to one of 4 feeding regimens; each regimen was applied to 4 cages of chicks. The regimens were: (1) ad libitum feeding (AL); (2) 80% food restriction at 4, 5 and 6 d of age (F80); (3) 60% food restriction at 4, 5, and 6 d of age (F60); and (4) 40% food restriction at 4, 5 and 6 d of age (F40). From d 35 to d 41, all chicks were subjected to 38+/-1 degrees C for 2 h/d. 4. One day following food restriction (d 7), hsp 70 expression in the brain samples of F60 and F40 chicks was augmented but not those fed AL and F80. 5. Prior to the heat challenge (d 35), all chicks had similar hsp 70 response. Irrespective of feeding regimen, there was a marked increase in hsp 70 expression after 4 d of heat treatment (d 38). Following 7 d of heat exposure (d 41), except for the F60 chicks, the augmented hsp 70 expression in the brains of AL, F80 and F40 birds was not maintained. 6. Enhancement of hsp 70 expression was noted in birds subjected to F60, but not AL, F80 or F40, throughout the period of heat exposure.     

不同抗氧化剂和添加水平对肉仔鸡生产性能和抗氧化性影响的研究

为了研究不同抗氧化剂产品和添加水平对肉仔鸡生产性能和抗氧化性能的影响,本研究选用1日龄爱拔益加(AA)肉仔鸡96只,随机分为3个处理,每个处理4个重复,每个重复8只鸡。对照组(CTR)饲喂不添加任何抗氧化剂的基础日粮;SQM6组饲喂基础日粮+48mg/kgSQM6;SQMax组饲喂基础日粮+80mg/kgSQMax。记录肉仔鸡的日均采食量和平均日增重,并于28日龄时,随机在每个重复中选取1只鸡进行翅静脉采血,测定血清抗氧化指标。研究结果表明:与CTR相比,肉仔鸡日粮中添加抗氧化剂有改善饲料转化率的趋势(P>0.05);添加SQM6显著提高了血清中超氧化物歧化酶(SOD)的活性(P<0.05),并显著降低了丙二醛(MDA)的含量(P<0.05);日粮中添加SQMax显著提高了肉仔鸡血清超氧化物歧化酶(SOD)和谷胱甘肽过氧化物酶(GSH-Px)活性(P<0.05)。以上结果表明,肉仔鸡日粮中添加抗氧化剂SQM6和SQMax能够提高血清中超氧化物歧化酶和谷胱甘肽过氧化物酶活性,降低丙二醛含量,改善肉仔鸡机体抗氧化功能。     

Effects of supplemental vitamin E during the laying period on the reproductive performance of Taiwan native chickens

1. One-day-old Taiwan Native Breeder female chicks were fed on maize/soybean growing diets without supplemental vitamin E from hatch to 17 weeks of age. After 17 weeks the birds (n = 300) were randomly assigned to 5 dietary treatments and fed on maize/soybean laying diets supplemented with 0, 40, 80, 120 and 160 mg/kg of vitamin E (dl-alpha-tocopherol acetate), respectively, until 46 weeks of age. The variates measured included: age at first egg, feed consumption (FC), feed efficiency (FE), egg production (EP), egg weight (EW), egg specific gravity (ESG), eggshell strength (ESS), fertility and hatchability. 2. The addition of 120mg/kg of vitamin E lowered the first EW (P<0.05); however, there was no significant difference in the age or body weight (BW) of pullets at first egg or mortality rate to 46 weeks of age among the treatments. FE and egg mass were improved (P<0.05) in pullets fed 80 mg/kg of supplemental vitamin E. A significant increase in EP was observed after peak EP in pullets given 80 mg/kg of supplemental vitamin E. However, this favourable effect decreased as supplemental vitamin E exceeded 80 mg/kg. 3. From 17 to 46 weeks of age, egg quality (ESG and ESS) decreased with age. However, there was no correlation between age and fertility or hatchability during the experimental period, suggesting that egg quality is more age-sensitive than reproductive performance for breeder pullets. 4. Compared with the control, fertility and hatchability of all eggs set for the treatment with 80 mg/kg supplemental vitamin E increased by 7.7 and 13.4%, respectively. There was no difference in the hatchability of fertile eggs. 5. These results suggest that using supplemental vitamin E during the laying period can improve the reproductive performance of breeder pullets. The addition of 80 mg/kg of vitamin E obtained the best performance in EP, egg mass, FE (feed/egg), hatchability and fertility.     

Effects of the addition of roller mill ground corn to pelleted feed during a fifty-six-day production period on growth performance and processing yields of broiler chickens

Poor pelleting production rates can raise the milling cost and increase the frequency of feed outages for broiler integrated operations. The number of broilers marketed to heavy BW has been increasing, and meeting feed delivery schedules can be problematic with “big bird” complexes. Adding rolled corn post pellet is a management strategy to increase feed production rate while concurrently decreasing energy use of the grinding and pelleting processes. This study evaluated the addition of screened rolled corn to pelleted feed on live performance and meat yield of broiler chickens during a 56-d grow-out. Four dietary treatments were provided: A) a control, no added corn post pellet from 18 to 56 d of age; B) addition of 25% of the formulated corn post pellet from 18 to 56 d of age; C) addition of 10, 20, and 30% of the formulated corn post pellet from 18 to 35, 36 to 46, and 47 to 56 d of age, respectively; and D) addition of 20, 30, and 40% of the formulated corn post pellet from 18 to 35, 36 to 46, and 47 to 56 d of age, respectively. Final BW, cumulative feed conversion, 38-d BW uniformity, and 57-d breast meat weight and yield were similar among the dietary treatments. These results indicate screened rolled corn can be added post pellet without adversely affecting broiler performance and meat yield.     

Effects of early and late feed restriction or feed withdrawal on growth performance,ascites and blood constituents of broiler chickens

A study was conducted with male broilers to determine the effects of early and late feed restriction or feed withdrawal. In the experiment five treatments were represented by three replicate floor pens, each containing 20 broilers. The experimental procedure was a completely randomized design. The treatments were ad libitum (AL), 25% (FR-25) and 50% (FR-50) feed-restricted or 8 h (FW-8) and 16 h (FW-16) feed withdrawal regimes, respectively. FW-16 regime significantly reduced weight gain to 21 days of age compared to AL or FR-25 regimes (P<0.05). However, the overall weight gains between 9 days and 42 days of age were not significantly affected by the treatments. FW-8 and FW-16 broilers consumed significantly less feed than either AL or FR broilers between 9 and 21 days (P<0.05), however FW-8 and FW-16 broilers had similar feed intake to AL or FR-25 and FR-50 broilers between 9 and 42 days of age. Feed: gain, abdominal fat pad and heart weights, mortality, death due to ascites, and the incidence of leg disorders were unchanged by feeding regimes, although the incidence of ascites in FW-16 was significantly (P<0.05) lower than AL fed broilers. Blood constituents, such as albumin, total cholesterol, ketone bodies, glucose, chlorine, lactate dehydrogenase, alanine aminotransferase and creatine were also significantly affected by feeding regimes (P<0.05).     

Effect of quantitative feed restriction on broiler performance

The objective of the current study was to determine the effect of quantitative feed restriction on the performance of broilers. A total of 270 unsexed broilers were randomly allocated to three treatments: with no feed restriction (T1), one week (T2) and two (T3) weeks of feed restriction from 22 days of age and then fed ad libitum until the age of 42 days. Treatments were replicated three times with 30 birds per replicate. Birds were fed with starter, grower and finisher diets. The feed consumed and body weights were recorded every week from the third to the sixth week. The average daily gain (ADG), average daily feed intake (ADFI) and the feed conversion ratio (FCR) were computed for each week. At Week 6, body weights of T3 birds were similar (P > 0.05) to those of T1 and T2 birds. There were also no treatment effects on the ADG at Week 6. In addition, no treatment effects (P > 0.05) were observed on ADFI at each stage of growth. Since ADFI and FCR were similar among the three groups, it was concluded that feed restriction by limiting the time to eat was not successful. There was also no evidence of compensatory growth in the restricted groups.