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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 P. M. Hocking

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AFRC Institute of Animal Physiology and Genetics Research, Edinburgh Research Station , Roslin, Midlothian, EH25 9PS, Scotland Published online: 08 Nov 2007.

To cite this article: P. M. Hocking (1992) 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, British Poultry Science, 33:2, 253-269, DOI: 10.1080/00071669208417464 To link to this article: http://dx.doi.org/10.1080/00071669208417464

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British Poultry Science (1992) 33: 253-269

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

P. M. HOCKING Downloaded by [Ohio State University Libraries] at 08:47 23 February 2015

AFRC Institute of Animal Physiology and Genetics Research, Edinburgh Research Station, Roslin, Midlothian EH25 9PS, Scotland Received for publication 23rd April 1991

Abstract 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. 253

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INTRODUCTION

Experimental work with turkey breeders has not shown any benefit of food restriction during rearing on subsequent egg or poult production (Whitehead, 1989; Hester and Stevens, 1990) and ad libitum feeding is normal commercial practice. This is in marked contrast to broiler breeder flocks which are subject to a rigorous programme of food restriction throughout their life. Hocking et al. (1987) showed that ad libitum fed broiler breeders exhibited multiple ovulations while restricted birds did not. Multiple ovulations were associated with a decreased rate of lay of normally-shelled eggs and the loss of ovulated ova into the body cavity. To be fully effective in controlling the number of ovulable follicles, food restriction should produce a proportional decrease of about 0-4 of the body weight of ad libitum fed birds (Hocking, 1990; Hocking and Whitehead, 1990) and be continued to sexual maturity (Hocking et al., 1989). The potential for multiple ovulation increases with selection for rapid growth rates (Nestor et al., 1980; Hocking, 1990) and is higher in turkeys photostimulated at 24 rather than 30 weeks of age (Hocking, et al., 1988). The experimental results reviewed by Whitehead (1989), and Hester and Stevens (1990) were obtained from relatively small turkeys photostimulated at 30 weeks of age or later. In general, the extent by which body weight was reduced was not large and food restriction was not continued to sexual maturity (Whitehead, 1989). It was concluded from these reviews that no benefit would be expected from restricted feeding. An experiment was designed to test the possibility that a more substantial reduction in body weight at sexual maturity of turkeys photostimulated at 18 and 24 weeks of age might increase egg output during early lay. A medium body weight, cage-adapted strain, which was previously shown to exhibit a marked excess of ovarian follicles when photostimulated at 24 weeks of age (Hocking et al., 1988) was used. Full egg production records were obtained to assess the effect of body weight control on persistency of lay. Turkeys photostimulated at younger ages lay eggs of relatively poor hatchability (Woodard et al., 1974; Herron and Whitehead, 1985). Multiple ovulation is associated with poor shell quality and it is possible that a decrease in the incidence of multiple ovulation would increase hatchability. All eggs with apparently normal shells were incubated and eggs failing to hatch were opened to determine fertility and approximate age of death of the embryo. MATERIALS AND METHODS

Four-hundred-and-fifty 1-d-old female poults (strain 71, British United Turkeys Ltd, Chester, UK) were brooded on wood shavings in two controlled environment rooms. The birds in one room were fed ad libitum and those in the other were allocated a fixed quantity of food, starting at 6 weeks of age, so that the birds reached 0-5 to 0-6 of the body weight of ad libitum fed birds by 12 weeks of age. Dietary compositions and analyses are presented in Table 1. Diet 1 was fed from 0 to 4 weeks, diet 2 from 5 to 8 weeks, and diet 3 from 9 weeks to photostimulation. Diet 4 was fed when the birds were caged. Restricted

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turkeys were allocated 165 g/d on caging and were fed ad libitum after laying an egg. All birds were fed ad libitum after 36 weeks of age. The diets were pelleted and, during rearing, food for the restricted birds was scattered on the floor. Food for turkeys fed ad libitum was presented in suspended tube feeders and water to both groups was provided by suspended bell drinkers. Water was available 24 h/d for the ad libitum fed turkeys, but for restricted birds access to water was limited to 7 h/d at 7 weeks and 4 h/d at 10 weeks to prevent litter becoming wet. Water was available ad libitum at weekends and daily after the birds were caged. The beaks of all birds were trimmed at 10 d of age.

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TABLE 1

Composition and analysis of diets

Diet Composition (g/kg) Maize Wheat Barley

1

2

3

4

290

368 200

216 209 100 100 57

261 334 46

160-5

Oats Wheatfeed 30 Grassmeal 55 Vegetable oil 104 140 70 80 Herring meal 352 200 180 100 Soya (410 g CP/kg) 49 44 30 Meat and bone meal 5 5 5 48 Lime 20 20 15 22 Dicalcium phosphate 3 2 3 4 Salt (NaCl) 10 15 10 15 Pellet binder 5.5 5 5 5 Vitamin-mineral supplement1 1 1 Choline chloride (500 g/kg) Calculated metabolisable 13 energy (MJ/kg) 11-5 12-1 11-7 Determined analyses (g/kg) 247 205 167 Crude protein (N X 6-25) 274 16 12 28 Calcium 16 9 8 Phosphorus 10 12 37 31 28 Ether extractives 34 1 Supplied per kg diet at an inclusion rate of 5 g/kg: Cu 3-5 mg, I 0-4 mg, Fe 80 mg, Mg 300 mg, Mn 100 mg, Zn 50 mg, retinol 3000 fig, cholecalciferol 37-5 fig, a-tocopherol 30 mg, menaphthone 4 mg, thiamine 4 mg, riboflavin 10 mg, pyridoxine 5 mg, cyanocobalamin 20 /ig, folic acid 2 mg, biotin 100 fig, pantothenic acid 16 mg, nicotinic acid 50 mg.

The photoperiod was decreased to 14 h light/24 h (14 L:10 D) at 14 d and to 7 L-.17 D at 10 weeks of age. At 18, 24 and 30 weeks of age, 48 ad libitum fed and 48 restricted turkeys were transferred to individual cages where the photoperiod was photostimulatory (14 L:10 D). The cages were 45 cm wide, 60 cm deep, 73 cm high in the front and 66 cm at the back. The droppings fell on to a moveable belt which was cleaned regularly. There were two rooms each containing two banks of 64 cages arranged in two tiers. The birds in the 4 end cages of each block were utilised for the carcase analysis of turkeys photostimu-

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lated for 6 and 12 weeks. Some of these end cages were reused and several spare hens were also caged to replace those which had to be removed because of foot problems during the first few weeks in the cages. Inseminations using semen from contemporary males housed in floor pens commenced after caging. The males were also fed ad libitum or restricted and further details have been presented elsewhere (Hocking, 1988). Inseminations were performed weekly with 50 /A of semen. Turkeys were weighed at 6-week intervals throughout the experiment and shank length was measured on a sample of 30 poults during rearing and on birds killed for carcase assessment after caging. Food consumption was assessed on a room (treatment) basis until caging when individual weekly records were obtained. Production data were obtained from turkeys in the first 12 cages in each block (two birds per treatment). Sexual maturity was defined as the age at first egg. Daily egg records were maintained for each bird and every egg was weighed. Soft, misshapen, cracked or deformed shells were recorded separately. The eggs were stored at 13°C after fumigation with paraformaldehyde. All apparently normally-shelled eggs greater than 45 g were incubated at intervals of two weeks beginning at 28 weeks of age. Eggs failing to hatch were opened to determine apparent fertility and approximate age of death (weeks 1 and 2, week 3 and week 4). Poults were graded and the number of poults (seconds) in 4 categories (splayed legs, unhealed navels, small and the remainder) were recorded. At 18, 24 and 30 weeks 8 non-photostimulated turkeys were selected for carcase analysis. Eight birds were sampled for carcase analysis after 6 and 12 weeks of photostimulation in the end cages of each block, and at 55 weeks a further 8 turkeys were sampled from the production experiment. Each carcase was opened and the abdominal fat pad plus fat surrounding the proventriculus and gizzard was removed and weighed (abdominal fat). The abdominal fat was returned to the carcase which was stored at — 20°C. At a later date the whole bodies were cut into pieces and minced. Duplicate samples were frozen for chemical analysis. Dry matter, ash and protein content were determined by standard laboratory methods and carcase fat was determined after petroleum ether extraction. The production experiment was arranged as a randomised block design with a factorial arrangement of rearing treatment (ad libitum or restricted feeding) and age at photostimulation (18, 24 and 30 weeks) as main effects. Pairs of contiguous cages were allocated at random to each rearing-age treatment within each block of 12 cages and the mean of each pair of turkeys was analysed. Variables with normally distributed errors (body weight, log food intake, total egg and poult production, and average weekly egg weight) were analysed by conventional analysis of variance methods. Rates of egg production and hatchability data were analysed as proportions on the logistic scale with extra binomial variation modelled by the method of Williams (1982). The influence of age (weeks from hatch) on these variables was examined using a split-plot model. Egg production data were averaged over three consecutive weeks (12 three-week periods). The model for hatchability of fertile eggs included an effect for hatch (n=13) and two periods of storage (1 to 7 d and 8 to 14 d).

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The turkeys killed after 6 and 12 weeks of photostimulation were placed at random in the two tiers of cages in each room to form 4 blocks. The means of pairs of turkeys were analysed. The same 4 blocks were used in selecting the birds at 55 weeks for carcase analysis. A separate statistical analysis of single bird values was conducted on these data. Carcase data for. the non-photostimulated turkeys were analysed for the effect of age within three rearing treatment only because of confounding between room and rearing treatment. However, compared to food restriction, the effects of rearing environment were considered to be negligible after the turkeys had been caged (see Discussion). RESULTS

Rearing period

Body weights for turkeys fed ad libitum were 1-22, 3-97, 6-12, 7-24 and 7-95 kg at 6, 12, 18, 24 and 30 weeks of age respectively. The body weights of restricted birds were 0-55, 0-55, 0-61 and 0-61 of the turkeys fed ad libitum at 12, 18, 24 and 30 weeks of age respectively. In contrast to the large reduction in body weight, the shank length of restricted turkeys was more than 0-9 that of birds fed ad libitum at 12 weeks of age (115 compared to 125 mm) and did not increase thereafter. At 54 weeks of age, the body weight to shank length ratio was lower (P

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 photostimulatio...
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