Changes in ovarian function of female turkeys photostimulated at 18, 24 or 30 weeks of age and fed ad libitum or restricted until point of lay.

1. Females from a medium body weight strain of turkeys were fed ad libitum or restricted to 0.6 of ad libitum-fed body weight at sexual maturity and were photostimulated at 18, 24 or 30 weeks of age. Ovarian follicular structure was assessed in 8 birds from both rearing treatments at photostimulation, after photostimulation for 6 or 12 weeks and at 55 weeks of age. 2. The patterns of small white follicles and of larger yellow follicles were similar in restricted and in ad libitum-fed turkeys for birds in lay at the same age, regardless of the time elapsed since photostimulation. 3. Among birds in lay the number of normal yellow follicles and the proportion of multiple yellow follicles declined with age. A relatively low proportion of restricted birds photostimulated at 18 and 24 weeks were in lay after 12 weeks of photostimulation. 4. For birds in lay the number of white follicles 1.4 to less than 1.8 mm in diameter increased and the number greater than 1.8 mm declined with age. There was a corresponding increase in the rates of atresia in follicles 1.8 to less than 5.0 mm in diameter.     

Effects of photostimulation at 18, 24 and 30 weeks of age on the productivity of female turkeys fed ad libitum or restricted until point of lay.

1. Turkey females were fed ad libitum or restricted from 6 weeks of age to achieve mean body weights of 0.6 of ad libitum fed birds on photostimulation at 18, 24 or 30 weeks of age. Body weight, food intake, egg production and hatchability were recorded to 54 weeks of age. 2. Restricted turkeys were fed ad libitum after first egg or 36 weeks of age. Food intake after 30 weeks of age averaged 170 g/bird/d and was similar for all treatments. At 54 weeks of age, restricted turkeys photostimulated at 24 and 30 weeks were not as heavy as turkeys photostimulated at 18 weeks and ad libitum fed turkeys. 3. A large proportion of restricted turkeys photostimulated at 18 weeks of age did not commence lay until 30 to 40 weeks and a significant number of restricted birds photostimulated at 24 weeks had short laying cycles. Restricted birds photostimulated at 30 weeks came into lay and showed similar persistency of lay to ad libitum fed turkeys. 4. Ad libitum fed turkeys laid 115.0, 122.0 and 101.0 and restricted turkeys 92.4, 99.5 and 103.4 eggs when photostimulated at 18, 24 and 30 weeks, respectively. The number of non-settable eggs was lower in restricted compared with ad libitum fed turkeys and declined with age at photostimulation. 5. Egg size at the end of the experiment was similar for ad libitum fed turkeys and restricted birds photostimulated at 18 weeks but was 2.3 g lower for restricted birds photostimulated at 24 and 30 weeks of age. 6. Hatchability was higher, and the proportion of second quality poults was lower with eggs from restricted turkeys. The mean numbers of poults hatched were 59.9, 75.1 and 66.0 for ad libitum fed and 71.7, 65.7 and 79.4 for restricted turkeys photostimulated at 18, 24 and 30 weeks of age.     

Effects of age and of early lighting on ovarian function in breeding turkeys

1. Yellow follicle numbers and production of defective egg shells were greater in the early part of the laying period in conventionally-reared turkeys photostimulated at 24 rather than 30 weeks of age. 2. The number of yellow follicles declined with age and were similar in both groups at 40 weeks of age. 3. At 55 weeks of age more birds photostimulated at 24 weeks were out of lay and birds in lay had fewer yellow follicles and more atresia compared with turkeys photostimulated at 30 weeks of age. 4. The numbers of white follicles in the 1 to less than 2 mm size were similar in the two groups at each age. The proportion of white follicles which were atretic was negatively related to the number of yellow follicles, particularly in follicles 5 to less than 8 mm diameter.     

Comparative development of the ovary and production,fertility and hatchability of eggs from traditional turkeys and a contemporary male-line fed ad libitum or restricted

1. Ovarian function was assessed at first egg and at 44 and 54 weeks of age in traditional turkeys and in a male-line fed ad libitum or restricted to 0.5 of ad libitum during rearing. Egg production was recorded daily and fertility and hatchability were determined at 2 ages. 2. Age at sexual maturity did not differ between the 3 treatments. 3. The number of follicles at first egg in the male line averaged 16.3 compared with 8.9 in traditional turkeys. Food restriction in the male line decreased the number of yellow follicles to 14.6 at first egg and restricted birds were largely in a non-reproductive state from 44 to 54 weeks of age. 4. The total number of recorded ovipositions to 54 weeks of age in male line fed ad libitum or restricted and traditional turkeys respectively were 40.1, 25.2 and 70.7; comparable productions of normal shelled eggs were 28, 20 and 66.3. 5. There were no differences between treatments in fertility after a single insemination at 2 different ages. Hatch of fertiles after the first inseminations were 71.4, 45.5 and 90.3 respectively for male line fed ad libitum or restricted and traditional turkeys.     

Histopathology of antitrochanteric degeneration in adult female turkeys of four strains of different mature size

The left and right antitrochanters of 80 female turkeys of four strains were examined for histopathological changes at sexual maturity. Ten birds of each strain were fed ad libitum and 10 restricted to achieve 0.6 of the bodyweight of the ad libitum fed birds at 24 weeks old when the birds were photostimulated. Bodyweights at sexual maturity (28 to 31 weeks) for the four strains were 5.4, 6.5, 7.6 and 13.2 kg for restricted and 7.5, 9.0, 11.1 and 17.1 kg for ad libitum fed birds. The prevalence and severity of cartilage change increased with mature size and was lower in restricted turkeys then in turkeys fed ad libitum. The results showed that abnormal cartilage changes forming the basis of clinical disease occur in females. The prevalence and severity of lesions were directly related to bodyweight and were not limited to particular genotypes. Lesions were more severe in the centre of the antitrochanter, possibly because of forces exerted by the trochanter. Concentrations of basophilic cells in the hyaline cartilage were associated with the increased prevalence and severity of lesions in large turkeys and may be of significance in the development of osteochondrotic lesions in the antitrochanter.     

Interaction of age,strain, sex and food restriction on plasma creatine kinase activity in turkeys

1. Plasma creatine kinase activity was determined at 4, 8, 12, 16, 20, 24, 28, 38 and 48 weeks of age in male and female traditional turkeys fed ad libitum , in male and female turkeys of a sire-line fed ad libitum or restricted to 0.5 during rearing and subsequently to 0.8 of sex-specific ad libitum -fed body weight, and in sire-line males fed ad libitum to 18 weeks and 0.8 of ad libitum body weight thereafter. 2. Plasma creatine kinase activity was low in traditional turkeys and increased rapidly after 12 weeks of age in males and females of the sire-line of turkeys. 3. Food restriction decreased the activity of plasma creatine kinase. 4. There was no difference in plasma creatine kinase activity between the sexes during rearing. After the onset of lay, the activity in plasma from females decreased at 38 weeks of age and rose dramatically in restricted females at 48 weeks when the birds had ceased laying. 5. The changes in plasma creatine kinase activity in females were associated with concomitant changes in ovarian activity as reflected in altered plasma triglyceride concentrations.     

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.     

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.     

Observations on the size of the follicular hierarchy in the turkey hen and a case of arrested follicular growth

1. The phase of rapid development of ovarian follicles in turkeys fed ad libitum or given a restricted allocation of food from 6 to 30 weeks of age was determined by feeding a fat soluble dye and counting the number of rings of dye in the yolks of laid eggs. 2. The duration of rapid growth was similar in ad libitum and restricted birds and averaged 11.6 d. The maximum number of yellow follicles greater than 8 mm expected in the hierarchy of the turkey hen is 9 to 10 compared with 6 to 7 in the chicken. 3. Discontinuous growth was observed in a series of follicles from one bird. This is believed to be the first report of arrested follicular growth in the turkey.     

Limited effect of intense genetic selection for broiler traits on ovarian function and follicular sensitivity in broiler breeders at the onset of lay

Female chicks from 6 pure lines of broiler breeders were obtained from international broiler breeder companies. The lines were from three female and two male lines and a relaxed selection line derived from one of the male lines (M2) and maintained without selection for 25 years (generations). Replicate groups from each line were reared in floor pens and fed ad libitum. An additional group of the M2 male line was feed restricted and housed in similar pens. Twenty birds from each group were photostimulated after housing them in individual cages at 14 weeks of age. Ovarian follicular dynamics and follicular sensitivity were determined after the onset of lay. Female lines had a greater proportion of atretic follicles and more groups of multiple follicles than male lines. Body weights, fatness and age at puberty were similar in male and female lines. The relaxed selection line had more abdominal fat than any of the selected lines and the ovary contained a similar number of normal yellow follicles as the selected male line. Feed restriction decreased body weight, the numbers of yellow follicles, multiple yellow follicles and the proportion of atretic yellow follicles, and increased the age at onset of lay. The response of ovarian follicles of three different sizes to exogenous gonadotrophin stimulation with PMSG was similar in small yellow follicles, 5 to 6 and 2 to 3 mm white follicles in a female line, a male line and its relaxed line fed ad libitum. The results suggest that the original lines from which modern male-line broiler stocks are derived had a relatively large number of yellow follicles and a high propensity for multiple ovulation at the onset of lay. Separate selection for different traits in male and female lines has not had a dramatic effect on ovarian function or sensitivity to gonadotrophin stimulation.     

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.     

Assessment of pain during locomotion and the welfare of adult male turkeys with destructive cartilege loss of the hip joint.

1. An assessment was made of the potential pain and stress from musculo-skeletal disease at 54 weeks of age in large male-line turkeys fed ad libitum or on restricted amounts of food. Males from traditional turkey lines were used as a negative control. 2. Traditional turkeys were fed ad libitum and male-line turkeys were fed ad libitum or restricted to 0.5 during rearing and subsequently to 0.8 of sex-specific ad libitum-fed body weight or fed ad libitum to 18 weeks and 0.8 of ad libitum thereafter. 3. Pain was assessed at 54 weeks of age by the change in number of steps taken by turkeys with or without musculo-skeletal disease after a course of betamethasone, a steroid anti-inflammatory agent with analgesic properties. 4. The numbers of steps over 24 h were recorded using a pedometer and were similar in all 4 treatments before and after treatment with the analgesic. It was concluded that there was no evidence for pain associated with musculo-skeletal disease among the turkeys in this experiment. 5. Musculo-skeletal disease was not associated with raised heterophil-lymphocyte ratio, a recognised index of stress.     

Role of body weight and food intake after photostimulation on ovarian function at first egg in broiler breeder females

1. The role of body weight during rearing and food allocation after photostimulation on ovarian function in broiler breeder females was examined in two experiments. In experiment 1 birds were fed ad libitum, or to grow to 0.7 or 0.4 of ad libitum‐fed body weight at 20 weeks of age. After photostimulation at 16, 19 and 22 weeks respectively they were fed ad libitum, 145 g/d or 115 g/d in a factorial design. The ovary of each bird was examined after it had laid an egg. In experiment 2, restricted birds (0.4 of ad libitum‐fed body weight) were fed 125 g/d after laying an egg or ad libitum and a third group were given 125 g/d for 3 to 4 weeks and then fed ad libitum. The ovaries of these birds were examined 6 to 7 weeks after their first egg.

2. Food restriction after photostimulation had little effect on ovarian function in birds fed ad libitum during rearing. These birds had 2 to 3 hierarchies of yellow follicles of similar size. Restricted birds fed ad libitum after photostimulation had a large increase in the numbers of yellow follicles (1.7 to 2.0 hierarchies) compared with birds fed 145 g/d or 115 g/d which had 1.2 to 1.6 hierarchies of yellow follicles.

3. Age at first egg was largely a function of rearing treatment but feeding 115 g/d to the 0.4 treatment birds delayed the onset of lay compared with the other treatments.

4. Ad libitum feeding in restricted birds after the onset of lay resulted in a similar increase in the number of yellow follicles as the response to ad libitum feeding after photostimulation.

5. The prevalence of birds with atretic follicles was relatively high in birds fed ad libitum during rearing and in restricted birds fed ad libitum after photostimulation.

6. Yolk weight increased with age at photostimulation and food restriction decreased yolk weight by about 1 g compared with ad libitum feeding after photostimulation.     

Ovarian follicular dynamics in selected and control (relaxed selection) male- and female-lines of broiler breeders fed ad libitum or on restricted allocations of food

1. The reproductive structures of 4 broiler breeder lines fed ad libitum or restricted were compared at 1st egg. The lines were contemporary male- and female-lines and their respective progenitor lines maintained without selection for 20 years. 2. The selected lines were larger and had more hierarchical yellow follicles than the relaxed lines. The numbers of positions in the hierarchy were greater in the selected lines. The number of atretic follicles and the proportion of multiple follicles were relatively high in the selected male-line. 3. There were more white follicles in the range 1.8 to 5.0 mm diameter in the selected male-line than in the relaxed line, whereas selection did not change white follicle numbers in the female-line. 4. Food restriction decreased the numbers of normal and atretic yellow follicles and the proportion of multiples but had no effect on the number of positions in the hierarchy. Restricted feeding decreased the number of white follicles 1.4 to 2.4 mm and increased follicles 2.4 to 5.0 mm diameter. 5. There was little change in age at 1st egg among lines fed ad libitum. Restricted feeding increased age at 1st egg and the difference was greater in female- than in male-lines and in relaxed compared with selected birds. 6. Abdominal fatness was similar among the lines fed ad libitum and was decreased by restricted feeding. 7. Oviduct weights were greater in selected than in relaxed lines and were decreased by restricted feeding only in the selected male-line. 8. The weight of the largest follicle was higher in the selected lines and in restricted compared with ad libitum-fed birds. Plasma triglyceride concentrations were lower in restricted birds from the selected and relaxed female-lines compared with the other groups. Differences in plasma oestrogen concentrations could not be detected.     

Plasma oestrogen and triglyceride concentrations and reproductive characteristics of broiler chickens after ten generations of selection at seven weeks of age for high or low plasma very low density lipoprotein concentration.

1. Day old female chicks from two lines of broilers, selected for high or low plasma concentrations of very low density lipoproteins, were fed ad libitum or restricted until point of lay. All birds were fed ad libitum after laying an egg, and aspects of growth and reproduction were measured to 40 weeks of age. 2. Compared with lean line birds the growth rate of fat line females fed ad libitum declined from 16 weeks of age. 3. Mortality from apparently stress-related causes in ad libitum fed fat line females increased from 16 weeks of age and was 71% overall, compared with 26% in ad libitum fed lean line females. Mortality in the corresponding restricted birds was 20% and 7%, respectively. 4. Few fat line females fed ad libitum commenced lay and those which were restricted during rearing stopped laying after the initiation of ad libitum feeding. Egg productions in lean line birds fed ad libitum or restricted were similar. 5. Fat line females fed ad libitum had few yellow follicles and a high rate of atresia at first egg and between 37 and 39 weeks, as did restricted fat line birds between 37 and 39 weeks of age after being fed ad libitum. 6. Plasma concentrations of oestradiol-17 beta were 5-fold higher in fat compared with lean line females at 35 weeks of age. There was a similar large difference in concentrations of plasma triglyceride which reached 59 mg/ml in fat line females fed ad libitum.     

Control of the development of the ovarian follicular hierarchy in broiler breeder pullets by food restriction during rearing

1. The increase in the numbers of yellow and of white ovarian follicles was studied from 10 weeks of age to sexual maturity in broiler breeder pullets fed ad libitum and on a restricted intake. The growth of follicles greater than 1 mm diameter commenced at 14 to 16 weeks of age in ad libitum birds and at 22 to 24 weeks in those which were restricted. 2. In a second experiment, groups of birds restricted from 4 d of age were transferred to ad libitum feeding at 2-week intervals and examined at first egg. The numbers of yellow follicles at first egg were not affected by restriction to 14 weeks of age but, thereafter, declined linearly with time on restriction. 3. In the second experiment there were no comparable responses in the numbers of white follicles or in the rates of atresia. 4. Food restriction to 22 weeks of age produced about half the response in numbers of yellow follicles as restriction continued to point of lay (27 to 32 weeks of age). In practical situations, the results suggest that food intake should be restricted up to the onset of lay and then increased in relation to the rise in egg production. 5. Atresia was greatest in white follicles 3.15 to 6.30 mm diameter and was less outside this range.     

Effects of ad libitum feeding on performance of different strains of broiler breeders

(1) Tolerance to ad libitum feeding was compared in three genotypes of broiler breeder hens: a standard broiler breeder fed ad libitum (SA) or restricted (SR), a slow growing 'label' broiler breeder (L) and an experimental dwarf heavy broiler breeder (E). Two similar experiments were conducted in two distinct research centres. (2) Feed intake and body weight were measured every 3 weeks from hatch to 40 to 49 weeks of age. Egg production and egg abnormalities were recorded. The number of yellow follicles in ovaries was counted at the age of 32 weeks. (3) Body weight was stabilised at 2.2, 3.7 and 5.4 kg after 24 weeks of age in L, E and SA hens, respectively. Growth of the SR hens was similar to that of L up to 20 weeks and stabilised at a similar level to that of E hens after 30 weeks of age. (4) Sexual maturity was delayed by 6 weeks in restricted breeders compared to ad libitum fed hens that started to lay at 20 weeks. SA hens had low egg production and a high proportion of defective eggs, which was largely compensated for by feed restriction. However, productivity of SR hens remained lower than that of L breeders. (5) Compared to the low viability and reproductive fitness observed with SA hens, the E dwarf broiler breeder tolerated ad libitum feeding and had better egg production, fewer egg abnormalities and yellow follicles per ovary and a higher egg production. However, laying rate was still lower than that of the SR and L groups. Energy conversion (kJ/g egg) from 32 to 40 weeks of age was much higher in the SA group than in the other three groups. 6. The feasibility of feeding a dwarf broiler breeder ad libitum calls for further research on implications of specific IGF and GH-receptor expression at the level of the ovary in dw chickens.     

Effect of age and body weight at photostimulation on the sexual maturation of broiler breeder pullets transferred from 8L:16D to 16L:8D

1. In two trials, broiler breeders were grown to a mean body weight of 2.0 to 2.2 kg at 20 weeks on 8L:16D and transferred to 16L:8D at various ages between 69 and 175 d of age at mean body weights varying between 1.0 and 2.7 kg. Other groups were grown to have a mean 20-week body weight 0.87, 1.15, 1.25 or 1.37 of the normal birds and photostimulated simultaneously with the normal weight birds. Controls were held on 8L:16D in each weight group. In a third trial, broiler breeders were transferred from 8L:16D to 16L:8D at 45 (ad libitum fed), 75 or 90 d (mild feed control), when the mean body weight of each group had reached 2.1 kg. Controls weighing 2.0 kg at 20 weeks were held on 8L:16D or 16L:8D. 2. In trial 1, photostimulating normal weight birds at 69, 76, 83 or 97 d delayed maturity and widened the spread of individual maturities, whilst transferring to 16L:8D at 111 or 125 d advanced maturity. Increasing the mean 20-week body weight to 2.8 kg advanced maturity in birds transferred to 16L:8D at 97, 111 or 125 d. Birds photostimulated at 69, 76 and 83 d matured at a similar age to controls held on 8L:16D. 3. In trial 2, transferring normal weight birds to 16L:8D at 91, 112, 133, 147, 161 or 175 d advanced maturity. Reducing the 20-week mean body weight to 1.91 kg delayed maturity in birds photostimulated at 91 or 112 d, but advanced it in birds photostimulated at 112, 133, 147, 161 or 175 d. Sexual maturity was similar for birds with a 20-week mean body weight of 2.54 or 2.74 kg, with advances for all groups photostimulated between 91 and 175 d. 4. In trial 3, birds maintained on 16L:8D matured later than birds held on 8L:16D, but maturity was advanced when birds were transferred to 16L:8D at 45, 75 or 90 d at a common body weight of 2.1 kg.     

Comparison of the effects of the degree of food restriction during rearing on ovarian function at the onset of lay in unselected ducks (anas platyrhynchos) and in a line selected for improved food efficiency

1. Ovarian structure and function at sexual maturity in two lines of ducks (selected or not selected for juvenile food efficiency), fed ad libitum or restricted to achieve 0.50, 0.65 or 0.80 of unrestricted body weight at 24 weeks, were compared in a randomised block factorial experiment.

2. Selected ducks were larger but not fatter or older at sexual maturity, had more yellow follicles, giving a greater potential for multiple ovulation, and a higher proportion of atretic yellow follicles, compared with unselected ducks.

3. There was a linear relationship between the number of normal yellow follicles and body weight at the onset of lay which was similar in the two lines.

4. Several birds on the most severe regimen failed to lay and it was concluded that ducks should be at least 0–6 of unrestricted body weight for the onset of lay.

5. Weight of the ovary with follicles less than 8 mm diameter was greater in selected compared with unselected ducks and in birds fed ad libitum compared with restricted ones.     

Effects of food restriction or delayed photostimulation on ovarian follicle number, plasma oestradiol concentration and vaginal collagen content in male-line turkeys

1. An experiment was conducted to test the hypothesis that severe food restriction throughout the onset of lay or delaying photostimulation by 5 weeks would decrease the number of ovarian hierarchical follicles in male-line turkeys. It was proposed that a decrease in the number of hierarchical follicles would lower plasma oestradiol concentration and be associated with higher vaginal collagen content and a lower propensity to prolapse of the oviduct. 2. Five weeks after photostimulation, neither restriction to 63% of ad libitum body weight nor delayed onset of photostimulation had any significant effect on follicle number, plasma oestradiol concentration or vaginal collagen content. 3. It was concluded that neither food restriction nor delayed photostimulation can be used to control the over-development of the ovarian hierarchy in male-line turkeys.