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.     

Growth pattern and carcase development in male ducks selected for growth rate.

1. Growth patterns of the whole body, eviscerated carcases, breast muscle, leg and thigh muscles and abdominal fat pads were compared in 4 lines (Lines A, B, C, and D) of male ducks selected for market weight (n = 1305) using growth curve analysis, allometric growth analysis and repeated measure analysis. At 49 d of age, Line A was heaviest, followed by Line B, Line C and Line D. 2. Ducks were fed ad libitum under 24-h lighting and 12 or 24 ducks were killed to determine body, carcase, breast-muscle, leg and thigh-muscle, and abdominal fat weights at time points from hatching until 53 d of age. 3. The Weibull function was chosen for growth curve analysis. The asymptote and inflection point from the Weibull growth curves identified 3 lines (Lines B, C, and D) with discrete body and carcase growth patterns but did not distinguish Line A from Line B. In all 4 lines the asymptote ranged from 4437 g to 3008 g for body weight and from 3334 g to 2098 g for carcase weight; the inflection point ranged from 22.5 d to 25.3 d for body weight and from 25.4 d to 29.6 d for carcase weight. 4. The allometric growth coefficient, relative to whole-body growth, was higher than 1.00 for breast muscle and lower than 1.00 for leg and thigh muscles during from 4 d to 53 d of age. 5. Body fat accumulation was estimated by abdominal fat. Line D accumulated more abdominal fat than other lines. The pattern of fat accumulation in Line D was different from Lines A, B and C and there were no differences between Lines A, B and C.     

Effects of food restriction during the finishing period on the performance of broiler chickens

1. Three hundred 4-week-old commercial Hibrow broiler chicks were fed ad libitum , 85% and 70% of ad libitum or ad libitum for 5 d per week with 3rd and 5th days of food withdrawal for 28 d to examine the effects of food restriction on liveweight, growth rate, food conversion efficiency, dressing percentage, abdominal fat and mortality. 2. Quantitative food reduction to 85% and 70% of ad libitum , and reduction in feeding time by 2 d/week significantly reduced final body weight and rate of growth. 3. Food restriction (to 70% ad libitum ) resulted in lower abdominal fat than ad libitum feeding, 15% food restriction or reduction in feeding time by 2 d/week. 4. There were no significant differences between the effects of 15% food restriction and 2-d reduction in feeding time per week on final body weight, growth rate and abdominal fat. 5. Reduction in feeding time by 2 d/week resulted in the same food efficiency as ad libitum feeding and quantitative food restriction by 15% and a significantly better food efficiency than 30% quantitative food reduction. 6. Reducing feeding time by 2 d/week seemed to have less severe effects on the birds than quantitatively reducing food supply by 30%.     

Performance,incidence of metabolic disturbances and endocrine variables of food-restricted male broiler chickens

1. This experiment was carried out to evaluate the productive and physiological consequences of a slight but long term food restriction of male broiler chickens from 2 commercial strains. 2. Cobb-500 and Ross chickens were submitted to a 20% food restriction from 8 to 21 d of age. Strain, food programme and their interactive effects were analysed in terms of consequences upon performance, mortality, incidence of sudden death syndrome (SDS) and ascites syndrome (AS), index of right cardiac hypertrophy and plasma concentrations of hormones related to metabolism and growth (T3, T4, T3:T4 ratio, IGF-I and GH). 3. Although some catch-up growth was observed by refeeding previously restricted birds after 22 d of rearing, food restriction decreased (P ≤ 0.05) body weight at market age (42 d) irrespective of the strain, but improved (P ≤ 0.05) food conversion. 4. The incidence of mortality was not high in non-restricted birds but SDS and AS caused more than 50% of deaths. Hypertrophic cardiac index was observed in chickens of both strains after 4 weeks of age and was higher in ad libitum fed birds. 5. During the period of food restriction, plasma T3 and IGF-I concentrations decreased whereas plasma T4 and GH concentrations increased compared to those of the age-matched ad libitum fed counterparts. During the subsequent ad libitum feeding period, few differences in circulating hormone concentrations were observed, except for the higher mean GH litres in previously food-restricted chickens at 35 d of age. 6. These results indicate that even a non-severe food restriction negatively affects body weight of 42-d-old male broilers but these are benefits with improved food efficiency and diminished mortality from metabolic disturbances. The hormone results suggest that the degree of food restriction applied was not severe because there was a very fast adaptive response with small and transient alterations in T3, T4 and GH plasma concentrations during the period of compensatory growth.     

Reproductive performance of dwarf broiler breeders given different allowances of food during the rearing and breeding periods and two lighting patterns

1. Dwarf broiler breeders were either fed ad libitum or restricted to allow growth to mean body weights of 1.4 or 1.8 kg at 20 weeks of age. During the breeding period these birds were fed ad libitum, or food was restricted to different degrees and the birds subjected to two different incremental lighting patterns. 2. Egg production of birds fed ad libitum during the breeding period increased with the degree of food restriction during rearing. 3. Food restriction during the breeding period increased the egg production of birds weighing 1.8 kg at 20 weeks but decreased that of birds weighing only 1.4 kg. 4. Fertility was relatively low and inversely related to body fatness of females. 5. The differences in lighting pattern did not influence performance. 6. For optimum reproductive performance during the rearing period dwarfs should not be restricted so severely as conventional breeders. Best chick production was obtained from birds with a bodyweight of 1.8 kg at 20 weeks of age, which were subjected to a 10% restriction of food during the breeding period.     

The effect of increasing photoperiod and food restriction in sexed, broiler-type birds. II. Plasma thyroxine, triiodothyronine, insulin-like growth factor-I and insulin.

1. Sexed broiler-type chicks were raised either under a continuous (CON) 23 h light (L) and 1 h dark (D) schedule or an increasing photoperiod (INC). From 5 to 11 d of age birds were fed either: ad libitum (AL), energy intake (kJ ME) restricted to 9.414 x gBW0.67 (R1) or energy intake (kJ ME) restricted to 6.276 x gBW0.67 (R2). 2. Blood samples were taken at 4, 7, 11, 14 d of age and weekly thereafter to 49 d of age. Plasma thyroxine (T4), triiodothyronine (T3), insulin-like growth factor-I (IGF-I) and insulin were determined. 3. CON birds had elevated plasma T3 concentrations to 21 d of age, and greater plasma T4 concentrations at 11 and 21 d of age concurrent with greater food intake. Elevated plasma T3 concentrations in INC birds at 28 d of age coincided with lower plasma IGF-I concentrations at a time when growth and food intake were greater than CON birds. 4. Food restriction elevated plasma insulin and T4 but depressed plasma T3 and IGF-I. Plasma T3 was greater for food-restricted birds at 21 d of age, but subsequently, was generally lower than ad libitum-fed birds which may account for a lack of complete 'catch-up' in growth. 5. Plasma T3 was higher in females at 11 d of age when growth was equivalent for both sexes. From 28 to 42 d, when sex differences in growth became most apparent, plasma T3 was greater in males.     

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.     

The growth of turkeys 2. Body components and allometric relationships

ABSTRACT

1. The relationships between the main components of the body and body protein among males and females of BUT 6 (BUT) and Hybrid Converter (HYB) turkey strains were examined.

2. The weights of breast meat, breast skin, drumstick meat, drumstick skin, thigh meat, thigh skin and wing-plus-skin as well as the head, neck, feet, blood, heart, liver and gizzard were measured at different stages of growth after which all components of each bird were minced together in order to determine the feather-free body protein weight of each bird sampled. Using the weights of the components and the protein content of each bird the allometric relationships between the components and body protein were determined and then compared for each strain x sex combination.

3. By excluding the breast weights at day-old and at 7 d, the remaining points produced an acceptable allometric relationship (R² = 0.992). Thigh weight could be predicted for all strain x sex combinations using one allometric equation, as could drumstick skin weight. Breast and thigh skin weights differed between males and females. Females of the HYB strain exhibited heavier drumstick and wing-plus-skin weights at a given body protein weight than the other three strain x sex combinations. These differences in both the constant term and regression coefficient in the allometric equations between genotypes are probably due to differences in the amount of lipid that is deposited in these tissues.

4. Sexes differed in the allometric relationships for head, feet, heart and liver, while breeds differed in gizzard weight. A common relationship between the four genotypes could be used to predict the weight of blood in the carcass.

5. The allometric equations fitted to the data in this trial enable the accurate prediction of the weights of the different physical components given the weight of body protein.     

The effect of increasing photoperiod and food restriction in sexed broiler-type birds. I. Growth and abdominal fat cellularity.

1. Sexed broiler-type chicks were raised either under a continuous (CON) 23 h Light (L) and 1 h Dark (D) schedule or an increasing photoperiod (INC) consisting of an initial 6 h L and 18 h D which increased by 4 h L per week from 14 to 35 d of age after which a 23 L:1D was maintained to 49 d of age. 2. From 5 to 11 d of age birds were fed either: ad libitum (AL), energy intake (kJ ME) restricted to 9.414 x gBW0.67 (R1) or energy intake (kJ ME) restricted to 6.276 x gBW0.67 (R2). Food intake was ad libitum at all other times. 3. Food restriction reduced growth to 49 d of age although some compensatory growth did occur. Food efficiency was not significantly affected by restriction. 4. Although abdominal fat pad weight was significantly reduced for R2 compared to AL, this was not significant on a percentage body weight basis. 5. Adipocyte number in the abdominal fat pad was similar for AL, R1 and R2, but concomitant with a smaller fat pad weight, R2 showed reduced adipocyte volume compared to AL. 6. INC birds were lighter at 21 d of age, but body weights were equivalent to CON by 42 d of age. 7. Abdominal fat pad weight was some 10% larger at 49 d of age for INC birds. Adipocyte volume was unaffected, the increase in adipocyte being entirely caused by an increase in adipocyte number in INC birds.     

Effects of low dietary protein and different allocations of food during rearing and restricted feeding after peak rate of lay on egg production,fertility and hatchability in female broiler breeders

1. A 3x2x2 factorial experiment was conducted with boiler breeder females to determine the effects of body weight gain (three levels) and conventional or lower crude protein concentrations in the rations during rearing, and restricted or ad libitum feeding after the peak rate of lay on egg production, fertility, hatchability, mortality and food consumption. 2. Compared with ad libitum feeding, conventional food restriction resulted in a decrease in average daily food consumption of 0.6 during rearing, 0.2 during early lay and an increase of 0.4 after the peak rate of egg production. Mortality was decreased by more than half. 3. Restricted birds had higher total and settable egg production, fewer defective or damaged eggshells and higher fertility and hatchability than those fed ad libitum. The modified (more generous) rearing programme resulted in lower rates of egg production and higher rates of mortality compared with the conventional food restriction programme. 4. Low-protein rearing rations were associated with higher rates of food intake, higher mortalities and lower rates of egg production than the conventional protein rations. There were no differences in the fertility or hatchability of eggs between birds fed on the two concentrations of dietary crude protein. 5. Ad libitum feeding post-peak was associated with higher rates of mortality to 60 weeks of age. Post-peak feeding had little effect on the rate of lay or egg weight in conventionally restricted birds fed high protein rations or in birds fed ad libitum. Restricted feeding post-peak decreased the rate of lay and egg weight in birds on the modified restriction programme and in conventionally restricted birds fed on the low protein rations. There was no effect of post-peak feeding on fertility or hatchability of eggs. 6. The total numbers of saleable chicks per kg food consumed were 1.83, 1.72 and 0.52 for conventional, modified and ad libitum feeding during rearing; 1.56 and 1.15 for restricted and ad libitum feeding post-peak: there were no differences associated with protein concentrations of rations fed during rearing.     

Effects of ambient temperature and restricted feeding on the growth of feathers in growing turkeys

1. Male turkeys were reared to 6 weeks of age at 15 degrees C and 26 degrees C and fed ad libitum or restricted to 0.5 of the body weight of birds fed ad libitum. Basal metabolic rate was determined by indirect calorimetry at an ambient temperature of 20 degrees C. 2. Turkeys at 15 degrees C were lighter than those kept at 26 degrees C. Feather lengths and weight were similar in both groups. Fasting heat production corrected for both metabolic body size and activity was greater in turkeys reared at 15 degrees C than those at 26 degrees C. 3. Cranial breast feathers were significantly longer in restricted birds than in those fed ad libitum in contrast to a proportional decrease in the lengths of other feathers of 0.1 to 0.3. Feather weight as a proportion of body weight was 0.072 in restricted turkeys compared with 0.046 in birds fed ad libitum. There was no difference in basal metabolic rate between ad libitum and restricted turkeys. 4. It was concluded that feather growth was maintained in preference to body and muscle growth and that rearing birds at 15 degrees C did not improve breast feather cover. It is suggested that the growth of breast feathers in turkeys fed ad libitum is impaired.     

Production responses of layer strain hens to food restriction during rearing

Production responses of laying hens to food restriction during rearing were measured in two trials. Food was restricted by two methods: time restriction (TR, food continuously available for 24 to 30 h each 72 h) and proportion restriction (PR, daily allocations of about 60 to 70% of that consumed by ad libitum fed birds (F]. The rearing treatments were applied from 42 to 162 d and from 56 to 168 d of age in experiments 1 and 2 respectively. All birds were fed ad libitum in the laying period to 437 d and 476 d of age in experiments 1 and 2 respectively. Body weight was reduced significantly in both experiments by both methods of restriction, but more so by TR. Marked compensatory growth accompanied the high food intake following the end of food restriction. There was a significant increase in average egg weight concommitant with a change in the relationship between egg weight and age. Possibly this is due to an altered pattern of food intake at onset of lay.     

Welfare assessment of modified rearing programmes for broiler breeders

1. Female broiler breeders were fed ad libitum or a restricted quantity of food to achieve either a recommended body weight curve or a modified (linear) growth curve that allowed more generous feeding between 6 and 15 weeks of age. The birds were fed a ration containing either a normal or low concentration of crude protein. The welfare of the birds was assessed using a profile of indices of welfare at 6, 12, 18 and 24 weeks of age. 2. The low-protein ration decreased the body weight of birds fed ad libitum and restricted birds were fed substantially more of the low-protein ration to meet target body weights from 3 to 14 weeks of age. 3. The modified restricted rearing programme did not have an effect on indices of welfare. 4. Water intakes and plasma corticosterone concentrations were lower in restricted birds fed the low-protein ration and they spent more time resting, and less time spot-pecking, than birds fed the high-protein ration. 5. Birds fed ad libitum on both rations spent more time resting and less time foraging, drinking and spot-pecking than food restricted birds and were more fearful than restricted birds at 6, 12 and 18 weeks of age. 6. The heterophil:lymphocyte ratio in restricted birds was higher at 6 weeks and lower at 24 weeks compared with birds fed ad libitum. Humoral immunity was lower at 6 weeks of age in birds fed ad libitum and was similar at other ages. Cell-mediated immunity was similar among all treatments. 7. Plasma corticosterone concentrations were higher in restricted birds compared with birds fed ad libitum. Plasma creatine kinase activity was higher in birds fed ad libitum at 6, 12 and 18 weeks of age. Alkaline phosphatase and lactate dehydrogenase activity were higher whereas AST was lower in restricted birds compared with those fed ad libitum. 8. There was no evidence to support the use of low protein rations or linear growth curves to improve welfare in restricted broiler breeder females.     

Relationship between aging and nutritionally controlled growth rate on heat production of heifers

The first objective of this study was to test how well a function that was developed to describe heat production (HP) in growing ewes fit HP data in growing heifers. The second objective was to determine the pattern of adaptation of HP to feed restriction and subsequent realimentation of nutrients. At 234.5 +/- 0.5 d of age, HP was determined by indirect calorimetry on 32 Meat Animal Research Center III heifers. Following the first calorimetry measurement, heifers on the High-High (HH) treatment continued to receive ad libitum access to feed, and daily feed offered to the Low-High (LH) heifers was set at 157 Mcal of ME/kg of BW0.75. Feed restriction of LH heifers continued for 84 d. After 84 d of restriction, LH heifers were allowed ad libitum access to feed. Heat production was determined 4 and 11 wk following feed restriction and 2, 5, 12, and 18 wk following realimentation. There was no residual bias when HP in ad libitum-fed heifers was estimated with an equation form developed in growing ewes: [(kcal/d) = f(BW, matBW) = BW (Ae[k(BW/mature BW)])], nor was there a residual bias when HP was predicted with an allometric equation: [(kcal/d) = f(BW) = A(BWk)]. However, there were residual biases when HP was estimated with an allometric equation that set the exponent to 0.75. Heat production per unit of BW of LH heifers was lower than that of HH heifers at 4 wk of feed restriction (P < 0.001), but HP did not differ between treatments at 11 wk of feed restriction (P = 0.87). At 2 (P = 0.002) and 5 wk (P < 0.001) following the increase in feed offered, HP per unit of BW of the LH heifers was greater than that of the HH heifers. Heat production did not differ between treatments at 12 and 18 wk following refeeding (P < 0.17). Our findings demonstrate that the relationship between HP and BW is described equally well by a logistic and allometric function, but applying a generalized interspecies exponent in an allometric equation to growing heifers results in a bias in estimating HP. The equation form developed in ewes can be used to develop a single equation for the prediction of HP across ages in heifers.     

Progressive bradycardia,a possible factor in the pathogenesis of ascites in fast growing broiler chickens raised at low altitude

1. The first objective was to evaluate baseline heart rate (HR) responses in fast growing broilers fed ad libitum from 1 to 45d or subjected to a food restriction (85%, 70% and 55% of ad libitum from 7 to 21d) and a refeeding (22 to 45d) regimen in a normal thermal environment. The second was to evaluate HR and haematocrit responses in fast growing broilers reared at a low environmental temperature and fed ad libitum (A-L) from 1 to 42d, subjected to food restriction (70% ad libitum ) between 7 to 21d and refed thereafter (R-R), or subjected to food restriction between 7 to 42d (R), and to follow the changes in normal birds and those prone to ascites. 2. The baseline HR in the normal thermal environment at 21 and 45d in birds fed ad libitum was lower (P < 0.001) than at 7d. The food-restricted groups had higher HRs at 21d than at 7d, with the differences significant (P < 0.01) for the 70% and 55% treatments. At 21d the HRs in restricted groups were significantly higher (P < 0.01) than in ad libitum -fed birds. After returning to ad libitum feeding the HRs in these birds tended to decline, with the differences significant (P < 0.05) for the 70% and 55% treatments. 3. In the birds exposed to cold, each feeding regimen produced distinct patterns of change in HR and haematocrit. Both feeding regimen and age had significant (P < 0.001) effects on the changes of both variables. Relative to 7d, on 14d and 21d the HRs decreased and haematocrits increased in all groups, but the rates of change were highest in the A-L and R-R birds. The first fulminant cases of ascites were observed during the third week in the A-L group and during the fourth week in the R-R group. None of the chickens from the R group developed ascites. Altogether, the incidence of ascites was 48% in the A-L group and 28% in the R-R group. 4. Among the birds exposed to cold, the ascitic birds had significantly (P < 0.001) lower HRs and higher haematocrits than normal birds from the same feeding regimen group. The time trends in the rates of change in HR and haematocrit were distinctly different (P < 0.001) for ascitic and normal birds. The change in feeding regimen from restricted to ad libitum in the R-R group resulted in a significant (P < 0.001) decrease in HR and increase in haematocrit. 5. In view of the evidence presented, it appears that hypoxaemia and tissue hypoxia in broiler chickens may be a result of circulatory insufficiency associated with progressive bradycardia rather than, as commonly believed, pulmonary insufficiency. In this situation the pulmonary hypertension may be a secondary symptom.     

Food deprivation and feeding of broiler chickens is associated with rapid and interdependent changes in the somatotrophic and thyrotrophic axes

1. In several experiments, hormonal changes in the somatotrophic axis, growth hormone (GH) sensitivity to a GH-secretagogue, thyroid hormones and their metabolising enzymes and plasma glucose levels were measured in relation to food deprivation and reinitiation after a single daily meal in 4- to 5-week-old male broiler chickens. 2. Floor-reared male broiler chickens were fed ad libitum or were restricted to a daily food intake of 40 or 45 g per d from the age of 2 weeks onwards. The daily food allowance was consumed in 0.5 h. 3. Food deprivation increased plasma GH concentrations but decreased GH-dependent variables such as plasma insulin-like growth factor-I and 3,3',5-triiodothyronine (T3) concentrations. Hepatic inner ring deiodinating type III activity was markedly elevated, presumably as a consequence of low hepatic GH receptor numbers, and is thought to be the causal mechanism for the low plasma T3 concentrations. Food intake reversed these variables in a time-related manner. 4. GH pulsatility characteristics, as calculated by deconvolution analysis, revealed profound changes between food restricted and ad libitum fed animals. Chickens deprived of food for about 23.5 h were characterised by an enhanced pulsatile GH release as reflected in the higher GH secretory burst amplitude, GH mass per burst, GH production rate and GH pulse frequency. These variables returned very quickly to normal values after refeeding. 5. In summary these experiments taken together demonstrate very clearly the interdependent and time-related changes of the somatotrophic and thyroid axes upon a single meal in previously food-deprived broiler chickens.     

禽胰多肽对肉鸡增重及内分泌影响的研究

选取1日龄艾维茵鸡160只,随机分为4组,每组40只。基础日粮含ME12.91、12.90MJ/kg,CP23%、21%。1￣21日龄期间,分别按体重在Ⅰ～Ⅳ组鸡基础日粮中添加0、1.16、3.48和10.44mg/kg禽胰多肽(APP)制品。鸡只自由采食及饮水,24h光照,试验期44d。试验结果表明:禽胰多肽能促进鸡甲状腺的发育,显著提高血浆甲状腺素(T4)浓度(P<0.05);促进鸡只的生长发育,显著提高肉鸡的增重(P<0.05),并改善饲料报酬。本试验中APP适宜添加量为每天每千克体重1.16mg。     

Welfare assessment of broiler breeders that are food restricted after peak rate of lay

1. Broiler breeder females were reared on one of three growth curves (ad libitum, conventional or modified restriction) and given rations containing a high or low concentration of crude protein. After the peak rate of lay they were fed ad libitum or a decreasing quantity of food in response to declining egg production. The welfare of the birds was assessed by determining the changes in indices of welfare at 36, 48 and 60 weeks of age. 2. Body weight increased rapidly in restricted birds fed ad libitum post-peak and water intake declined. 3. Post-peak food restriction was associated with a decrease in resting and increased drinking and spot-pecking activities. Birds that were food restricted during rearing spent more time foraging and spot-pecking at 36 and 48 but not 60 weeks of age. 4. Immune function increased with age but was not affected by the experimental treatments. The heterophil-lymphocyte ratio in birds fed ad libitum during rearing was numerically lower at 36 and higher at 48 and 60 weeks of age compared with restricted birds. 5. There was no effect of treatment on plasma corticosterone concentration. Creatine kinase activity was high at 60 weeks in treatments that were characterised by poor reproductive status and the activities of other enzymes reflected differences in reproductive status and mortality. 6. There was no long-term welfare or production advantage from feeding low protein rations or more generous feeding during the rearing period compared with conventional food restriction programmes.     

Welfare of food restricted male and female turkeys.

1. The welfare of male and female male-line turkeys fed ad libitum or food-restricted was determined at 4, 8, 12, 16, 20, 24, 28, 36(38) and 46(48) weeks of age using behavioural and physiological indices of well-being. Traditional turkeys fed ad libitum were kept as a control treatment. Restricted male and female male-line turkeys were fed to 0-5 during rearing and subsequently to 0-8 of sex-specific ad libitum-fed body weight. In another treatment, male-line males were fed ad libitum to 18 weeks and 0.8 of ad libitum thereafter. 2. Traditional turkeys and restricted male-line turkeys were more active than ad libitum-fed birds of both sexes. Restricted turkeys showed a high incidence of wall pecking. In the breeding period, about 0.4 of the observations of male-line males were of strutting behaviour whereas traditional male turkeys showed no strutting behaviour at the end of the breeding period. 3. The heterophil lymphocyte ratio (HLR) and the proportion of basophils were not increased in food-restricted turkeys. The HLR was relatively low in traditional birds, compared with male-line turkeys during the rearing period. 4. Plasma corticosterone concentrations were increased by food restriction during the rearing period. Corticosterone concentrations were relatively high in traditional turkeys at 4 and 8 weeks of age only. 5. Plasma lactate dehydrogenase (LIDH) activity was higher from 12 to 24 weeks of age in ad libitum-fed male-line turkeys and was consistent with mortality from cardiovascular disease in this group of turkeys. The pattern of activity of aspartate transaminase was similar, and alkaline phosphatase was inversely related to that of LDH. 6. It was concluded that turkeys may be better able to adjust physiologically to the demands of food restriction than broiler breeders and that there were few deleterious consequences of restricting male turkeys after 18 weeks of age. Male-line turkeys were less active than traditional turkeys.     

Influence of food restriction during rearing on the body composition of layer-strain pullets and hens

The influence of two methods of food restriction during rearing on the body and liver composition of layer-type birds was investigated during and after restriction. In each of two experiments groups of birds were reared on one of three treatments: ad libitum food intake (A), time-limited food restriction (TR) or proportional food restriction (PR). All birds were fed ad libitum during the laying phase. In experiment 1, six birds from each treatment were selected at random for estimation of body and liver composition and killed at 70, 101, 162, 218 and 337 d of age. In experiment 2 four birds were selected from each treatment at 280 and 467 d of age. Body composition was predicted in experiment 2 at various times such as sexual maturity, using equations based on deuterium oxide dilution techniques. Body composition changes caused by food restriction were related to the length of restriction. Towards its end the major changes were: decreased body fat, increased total body water and increased water content of the fat-free mass for TR and PR birds compared to A birds. Some changes were not due to a reduced liveweight. Food restriction during rearing did not change body composition permanently, although predicted body fat at sexual maturity (experiment 2) was lower and protein content higher for TR and PR than for A birds. There was no demonstrable relationship between the body fat content predicted at sexual maturity and subsequent rate of lay (experiment 2).