Effect of size and timing of photoperiod increase on age at first egg and subsequent performance of two breeds of laying hen

1. ISA Brown and Shaver 238 pullets were changed from 8 h to 8, 10, 13 or 16 h photoperiods at 42, 63, 84, 105, 126 or 142 d of age.

2. Age at first egg (AFE) was curvilinearly affected by the size and timing of the change in photoperiod. AFE was advanced most by a photoperiod change from 8 to 13 h made at 63 or 84 d. ISA birds were generally more responsive than Shaver to the photoperiod changes.

3. Longer photoperiods significandy increased survivors' egg production, but decreased liveability to 504 d, so that eggs per hen housed were unaffected. Retarding AFE by 10 d reduced survivors' egg numbers by 7.0, but increased mean egg weight by 1.26 g. Egg output by Shaver birds was unaffected by AFE, but that of ISA was curvilinearly affected, with an apogee at an AFE of 135 d. In both breeds, egg weight and egg output were greater following an early or late, rather than a mid‐term photostimulation.

4. Photoperiod significandy increased mean daily food intake during lay by 1.26 g/h. A 10 d retardation in AFE resulted in a reduction in food intake of 1 g/d. Efficiency of food conversion deteriorated according to the square of the photoperiod, and changed curvilinearly according to age at photostimulation. Food conversion efficiency improved by 0.05 g/g for each 10 d delay in AFE.

5. Shell quality was unaffected by AFE, but deteriorated with increasing photoperiod and was curvilinearly affected by age at photostimulation with the smallest shell weights associated with photostimulation at 63 d. The incidence of double‐yolked (DY) egg production increased with photoperiod and decreased with delayed photostimulation. There was an exponential regression of DY eggs on AFE.

6. Body weight at first egg increased by 75 g/d delay in AFE, but body weight at 504 d of age was unaffected by AFE, photoperiod or age at photostimulation. Body weight gain during lay increased by 15 g/h increase in photoperiod, decreased by 6 g per 10 d delay in photostimulation and by 40 g per 10 d delay in AFE. Fat content at 504 d increased by about 10 g/kg and by 23 g/bird for each 10 d delay in AFE.

7. Mortality in lay increased by 0.8%/h increase in photoperiod, but was unaffected by either age at photostimulation or AFE.     

Effect of constant and of changing photoperiods on age at first egg and related traits in pullets

1. The effects of constant photoperiods and of single (5 h) changes in photoperiod applied at 12 or 17 weeks of age upon age at first egg (AFE) were studied using ISA Brown and Shaver 288 pullets.

2. Birds reared from 2 d of age until after maturity on constant 10 h photoperiods matured 8 d earlier than birds reared on constant 8 h and 5 d earlier than the average for 13 or 18 h photoperiods.

3. A single increment in photoperiod from 8 to 13 h advanced AFE by 23 d (compared to 8 h constant day controls) when applied at 84 d, but by only 6 d when given at 119 d. An increase in photoperiod from 13 to 18 h advanced AFE by only 4 d, averaged across breeds and age at increase. A reduction in photoperiod from 13 to 8 h delayed AFE by 22 d when given at 84 d and by 16 d at 119 d. A similar 5 h reduction in photoperiod, but from 18 to 13 h, retarded maturity by 11 d in ISA Brown pullets, but only when given at 84 d, and delayed AFE in Shaver 288 by 12 d, but only when given at 119 d. This interaction may be partly explained by the different physiological stages reached by the two breeds when the photoperiod was changed.

4. Under constant daylengths cumulative food intake before first egg was positively correlated with photoperiod, but the early AFE for birds on 10 h photoperiods resulted in this group having the lowest cumulative food intake to first egg.

5. A 5 h increase in photoperiod at 84 d significantly reduced the food consumed to first egg, but had no effect when given at 119 d. A 5 h decrease in photoperiod generally increased the food consumed to first egg, but the effect was only significant when the daylength was reduced from 13 to 8 h at 119 d. Food intake to first egg in birds subjected to a change in photoperiod was highly correlated with AFE.

6. The data confirm that sexual development in growing pullets responds more to changes in photoperiod than to the absolute daylength, that changes made at different daylengths are not equivalent and that sensitivity changes with age.     

Effects of changes in photoperiod and feeding opportunity on the performance of two breeds of laying hen

1. ISA Brown and Shaver 288 hens, fed ad libitum, were given a 5‐h increase or a 2, 5 or 10‐h decrease in photoperiod at 215 d of age. Hens of both breeds were also maintained on constant 10, 13 or 18 h photoperiods. Other groups had their photoperiod increased from 8 to 13 h, or were held on constant days but had their access to food limited to 8 h per day.

2. Both breeds on ad libitum feeding exhibited curvilinear rate of lay and egg output, and linear food intake, responses to photoperiod change. Shaver hens reduced their egg output and rate of lay to a greater extent than ISA Brown hens when photoperiod was decreased.

3. In both breeds the beneficial effect on egg production of the 5‐h increase in photoperiod was less than the adverse effect of the 5‐h decrease.

4. The influence of light change per se generally had a greater effect on performance than the influence of feeding opportunity, but significant effects of changing feeding opportunity were demonstrated.

5. The reduction in mean rate of lay and egg output following a reduction in photoperiod was partly caused by some birds ceasing lay, but all birds showed some decrease in both variates     

Photoperiod and seasonal influences on the growth of turkey hens

1. The influence of photoperiod and time of year on the growth of hen turkeys was investigated.

2. Photoperiod treatments consisted of computer simulations of day lengths which occur naturally in the spring and autumn of the year. Both photoperiod treatments were given to hens in the autumn and spring.

3. Data were collected for growth evaluations at 2‐ to 4‐week intervals to 16 weeks of age. No significant season × photoperiod interactions occurred.

4. The spring trial resulted in greater body weights and better food conversions (food/gain) than the autumn trial.

5. Simulated autumn daylengths resulted in greater body weights and improved food efficiency at 16 weeks of age compared with simulated spring daylengths.

6. The pattern of growth (period changes) was influenced by season, but not photoperiod.

7. Season and photoperiod both have important and independent influences on the growth of the turkey hen.     

Responses of immature pullets to repeated cycles of gradual increases and abrupt decreases in photoperiod

1. Growing pullets were reared on constant 8, 11 or 14 h photoperiods or given 12 daily increments of 30 min followed by an abrupt 6 h decrease in photoperiod in 14 d cycles from 2 d of age to sexual maturity.

2. Birds on the experimental lighting programme matured earlier than constant 8‐h controls, later than 11‐h controls but at the same age and body weight as constant 14‐h controls.

3. Weight of the first egg was correlated with age at first egg.

4. It is assumed that potential advances in maturity for the experimental birds from the 30 min increments in photoperiod were cancelled by the retarding influences of 6 h decreases in photoperiod, resulting in their maturity being similar to that of birds reared on a constant daylength equal to the longest photoperiod reached during the cycle.     

Effects of restricting body weight gain or limiting the photoperiod during rearing on sexual maturity,viability and semen production in large white Turkey males

1. Severe restriction of food from 6 to 54 weeks of age resulted in lower body weights and smaller testes weights in male turkeys.

2. As a proportion, mortality was 0.5 in turkeys fed ad libitum and 0.1 in those which were restricted. There were significantly fewer leg problems in the birds undergoing food restriction.

3. Sexual maturity was delayed 4 weeks by food restriction although semen quality was similar to that in ad libitum‐fed birds.

4. Individual semen production was lower after food restriction but, because mortality and food consumption were also lower, semen production per male housed and semen production per kg of food eaten were proportionally 0.30 and 0.32 greater in restricted‐compared with ad libitum‐fed turkeys.

5. Useable quantities of good quality semen were obtained from ad libitum‐fed turkeys at 23 weeks of age.

6. A short photoperiod (7L:17D) from 10 to 18 weeks of age in ad libitum‐fed turkeys produced more rapid development of normal semen production compared with turkeys given a longer photoperiod (14L:10D).     

Effects of timing and size of daylength change on brown egg laying domestic hens: Plasma luteinising hormone concentration and sexual maturity

1. Brown egg laying pullets were transferred from an 8‐h photoperiod to an 8‐, 10‐, 13‐ or 16‐h photoperiod at 6, 9, 12, 15, 18 or 20–3 weeks of age. Plasma luteinising hormone (LH) concentrations were measured at transfer and 7 and 14 d afterwards.

2. Significant increases in plasma LH occurred following light stimulations at 6, 9 and 12 weeks of age.

3. Changes in LH concentration 7 d after a light increase from 8 h to 8, 10, 13, 16 h were highly correlated with photoperiod length at 9 and 12 weeks of age.

4. Changes in LH were generally poorly correlated with age at sexual maturity, although the reduced influence on age at first egg of a light increase given close to sexual maturity was reflected in minimal LH responses at 18 and 20.3 weeks.     

The effect of photoperiod on performance of male Turkeys from 2 to 15 weeks of age

1. Two‐week‐old male turkeys were subjected, for 13 weeks, to four lighting treatments, 23 h/d, 14 h/d, 8 h/d, and a “step‐down” pattern in which light was reduced from 22 h/d by 1 h a week to 14 h/d.

2. Within each lighting treatment half the groups were offered food ad libitum and half received restricted amounts of food which were similar for all lighting treatments.

3. There were no statistically significant differences in final body weights or food conversion ratios between photoperiod treatments, although within groups fed ad libitum food conversion ratio was slightly superior for turkeys which had received 23 h light/d throughout.     

Day‐length during rearing and the subsequent egg production of meat‐strain pullets

1. The effects of lighting pattern on production to 399 d in caged, female, meat‐strain chickens was investigated. Energy intake was controlled from 56 to 399 d.

2. Four different rearing treatments with a subsequent constant 16‐h photoperiod during laying were used.

3. A 15‐h rearing photoperiod resulted in delayed sexual maturity, increased mature body weight and decreases in both total egg numbers and the proportion of smaller eggs, compared with a 6‐h photoperiod.

4. Continuous light to 56 d, although associated with a high incidence of subsequent blindness, resulted in satisfactory egg production.

5. Abrupt reduction in the photoperiod from 15 to 6 h for the 112 to 167 d period resulted in unsatisfactory subsequent performance, especially when the day‐length was only slowly increased to 16 h during laying.

6. In the two laying treatments, in which the photoperiod was increased gradually from 6 to 16 h during the 168 to 238‐d period, a decrease in the number of smaller eggs occurred, compared with the treatments in which a single abrupt increase in photoperiod was used.     

Effects of different lighting regimes on diurnal feeding patterns of the domestic fowl

1. Male hybrid chicks were, from hatching, subjected to either a 12‐h photoperiod with uniform light intensity or a 12‐h photoperiod with a simulated “dawn” and “dusk” or to continuous light.

2. At 10 weeks of age the birds exposed to “dawn” and “dusk” were significantly heavier than those exposed to 12 h uniform illumination and these were heavier than those in continuous light.

3. From 15 to 25 weeks of age the birds in continuous light showed a marked diurnal rhythm in food intake, eating most in the period corresponding to normal daytime, while all birds subjected to 12‐h photo‐periods ate most at the end of the day, apparently having learnt to anticipate when their day would end.

4. When the birds subjected to continuous light were given one of the two 12‐h photoperiods, those given 12 h of uniform light intensity started by eating most food in the mornings, but later ate more towards the end of the day, while those with the “dawn” and “dusk”, ate more food at the end of the day during most of the 20‐d experimental period.

5. It is concluded that the birds preferred to eat most at the end of the day, probably to ensure adequate stores of food in the crop during the night. However, it was necessary for them to learn when their day would end, and this they did much sooner with the presence of a “dusk” than without it.

6. It is suggested that the difference in growth rate among the three treatments can be accounted for by differences in the efficiency of food conversion and also by differences in food intake.     

The effect of photoperiod on performance of female turkeys from two to 16 weeks of age

1. Female turkeys were subjected, from 2 to 16 weeks of age, to four lighting treatments, 23 h/d, 14 h/d, 8 h/d and a “step‐down” pattern in which light was reduced from 22 h/d by 1 h per week to 14 h/d.

2. Within each lighting treatment half the groups were offered food ad libitum and half received the same restricted amounts of food on all lighting treatments.

3. There were no significant differences in final body weight or food conversion efficiency (FCE) between photoperiod treatments. FCE was superior in restricted groups (P<0.05).     

Effects of lighting regimen and grower diet energy concentration on energy expenditure,fat deposition and body weight gain of laying hens

1. Mean metabolisable energy (ME) intakes and heat productions over a laying year were calculated for laying hens which had been submitted to one of various lighting regimens and given either a normal or a high energy ration during the rearing period.

2. Daily ME intake and heat production per hen in the laying period were unaffected by either lighting regimen or grower diet. ME intake per kg W ^0.75 and heat production per kg W ^0.75 during lay increased significantly with laying photoperiod, was non‐significantly higher following an 8‐h rather than an 11‐h rearing photoperiod, but was unaffected by dietary energy concentration. The increase in heat production (/kgW°‘⁷⁵) associated with a 1‐h increment in photoperiod was similar to predictions made from calorimetric measurements of diurnal variation.

3. Efficiency of conversion of food to egg was unaffected by either lighting regimen or dietary energy concentration.

4. Fat weight gain in lay was not influenced by lighting regimen, but was significantly lower in birds reared on the high, compared to the normal, energy grower ration. Fat‐free weight gain in lay was unaffected by grower diet, but was significantly increased by photoperiods longer than 8 h.

5. ME intake and heat production per kgW^⁰⁷⁵ were negatively correlated with age at first egg, but ME intake and heat production per bird d were not related to age at sexual maturity.     

Effect of photoperiod on the mean oviposition time of two breeds of laying hen

1. Oviposition times were recorded for brown and white egg‐laying hybrids under 8, 10, 13 and 18 h photoperiods.

2. Mean oviposition time for both breeds was advanced relative to dusk by approximately 0.5 h for each 1 h extension of photoperiod.

3. Mean oviposition time for the brown egg hybrid was 1.2 to 1.4 h earlier than that of the white egg hybrid under each lighting regimen.

4. A genetic difference in phase setting of the Open Period for Luteinising Hormone (LH) release is the likely reason for the difference in mean time of lay of the two breeds. The difference is possibly one between brown and white hybrids generally, rather than between the particular varieties of hen used in this trial.

5. The proportion of the day in which eggs are laid is shorter under long photoperiods presumably because light at the end of the photoperiod inhibits the pre‐ovulatory surge of LH.     

Relationship between body fatness,ovarian structure and reproduction in mature females from lines of genetically lean or fat broilers given different food allowances

1. Reproductive and other characteristics were measured at 34 and 60 weeks of age in broiler breeder hens on 6 different feeding regimes. The hens came from genetically lean and fat lines selected on the basis of low or high 7‐week plasma very low density lipoprotein (VLDL) concentration.

2. Plasma VLDL concentrations were consistently higher at all ages in fat line hens but were not affected by dietary treatment.

3. Mature body weight did not differ between the lines in birds fed ad libitum but with food restriction throughout life, fat line birds were lighter at 34 weeks.

4. There was little difference between the lines in abdominal fatness of birds fed ad libitum up to 60 weeks. Fat line birds were always fatter than lean line counterparts under food restriction.

5. Egg production was higher in lean line birds fed ad libitum but food restriction improved egg production in both lines. Peak egg productions were similar in both lines but there was evidence that the optimal food allowances for egg production was higher in the lean compared with the fat line.

6. Ovarian yellow follicle numbers were highest at 34 weeks in ad libitum fed lean line birds and declined linearly with decreasing body weight caused by food restriction but there was no such relationship in fat line birds.

7. White follicle numbers were higher and follicular atresia was lower in the lean line.

8. It is concluded that poor reproduction in fat line birds was associated with inhibition of follicular development and atresia rather than by high plasma VLDL concentrations promoting excessive yolk formation.     

Comparison of food intake,rate of consumption,pecking activity and behaviour in layer and broiler breeder males

1. The food intake, rate of food consumption (g/min) and behavioural time budgets of individually caged broiler and layer (white egg) males were compared in the early morning (1.5 to 3.5 h after onset of photoperiod) and afternoon (5.5 to 7.5 h after photostimulation) on 4 different days at 11 to 12 weeks of age. Correlations among rate of consumption, the proportions of time on different activities and previously estimated scores for fearfulness were calculated.

2. Food intake and rate of consumption were two‐fold greater in broilers than in layers. The proportion of time spent feeding in the morning was lower in layers compared with broilers and was similar in the afternoon. Rate of consumption was higher in the morning than in the afternoon in both lines.

3. Overall, a similar proportion of time was spent feeding, standing and sitting in bodi lines. The birds were more likely to be sleeping (eyes closed) in the afternoon than in the morning.

4. The proportions of time spent on preening, pecking and stereotypic pacing were greater in layers than in broiler breeders. The proportion of time spent drinking tended to be higher in broiler breeders than layers.

5. Two measures of fearfulness, aversion to a looming human and a novel rod were respectively positively and negatively correlated to time drinking and stereotypic pacing.

6. The time spent in stereotypic pacing was negatively related to rate of consumption and time spent preening.

7. The results suggest that low food intake is associated with increased arousal, fear and frequent feeding and drinking. There was no evidence that beak related activity was related to fearfulness.     

Evidence for hepatic glucostatic regulation of food intake in the domestic chicken and its interaction with gastro‐intestinal control

1. Male birds of a laying strain had permanent catheters introduced into the hepatic portal vein via the coccygeo‐mesenteric vein.

2. Infusions of 5 ml of 40, 100 or 150 g glucose/1 solution over 2 min caused a non‐significant depression of food intake compared with a 9 g NaCl/1 control solution.

3. Infusions of a range of isotonic glucose solutions (0 to 60 g glucose/1, 300 mosm) at 1.4 ml/min over 3 h caused food intake depression within the 3‐h period (P<0.01) proportional to the logarithm of the dose.

4. This effect was not observed when 60 g glucose/1 was infused at the above rates into the jugular vein.

5. Starvation of the bird for 21 h accentuated the depressive effect of glucose load on food intake, especially when birds were not given food until after the 3‐h infusion.

6. The infusion of solutions of sodium chloride (1.0 to 13.0 g/1, 33 to 433 mosmoles/kg) at. 1.4 ml/min over 3 h stimulated food intake within the range of 3 to 7 g NaCl/1 (100 to 233 mosm) but suppressed intake outside this range. This can be interpreted as a possible interaction with water intake control.

7. Infusion of 20 ml of glucose solution (0, 18 or 54 g/l) over 5 min into the crop and 0, 3.75 or 60 g glucose/1 at 1.4 ml/min over 3 h into the hepatic portal vein, caused an additive, linear depression of food intake.     

The photoperiodic effect of ahemeral light‐dark cycles which entrain circadian rhythms

1. A 27‐h cycle of light and dark provides a greater gonadotrophic stimulus to the laying fowl, as judged by sexual maturity and rate of lay, than a 24‐h cycle incorporating the same photoperiod.

2. An hypothesis put forward to account for these effects states that Effective Photoperiod equals p + c – b, where p = actual photoperiod, c = cycle length and b = the period of the endogenous biological clock.

3. Two experiments designed to test this hypothesis have yielded results which are consistent with it.

4. A poultryman who uses an ahemeral cycle to alter egg weight or shell thickness and then wishes to transfer his flock back to a 24‐h cycle should calculate the difference between the two cycle lengths and then add this quantity to the prevailing photoperiod to find the appropriate amount of light to be used in the 24‐h cycle.     

Effect of access time to food on broilers fed on diets of differing nutrient concentration

1. In the two experiments on restricted feeding of broilers there were no interactions between dietary nutrient concentration and access time to food on either performance or carcass characteristics.

2. In the first experiment (winter), food denial for 8 h/d improved food conversion efficiency and increased dressing percentage. Increasing nutrient concentration increased growth rate; decreased food intake; and improved conversion efficiency.

3. In the second experiment (summer), food denial for 8 h/d tended to increase growth rate and to improve conversion efficiency, but not significantly. Increasing nutrient concentration had the same effect as in experiment 1.

4. It is concluded that restricted access to food generally improves food efficiency.     

The performance of cross‐bred hens given free choice feeding of whole grains and a concentrate mixture and the influence of source of xanthophylls on yolk colour

1. Cross‐bred hens were offered, from 25 to 73 weeks of age, diets based on either wheat or barley in the form of either a mash or as whole grains plus a concentrate mixture; four sources of xanthophylls were also compared.

2. Wheat reduced food intake by 8%, increased efficiency of food conversion and live‐weight gain while barley increased litter moisture content, and, during the first half of the laying year decreased egg production by 3.3% and yolk colour by 4%.

3. Hens offered whole grains ate 11% less food, converted food into eggs more efficiently, were heavier and laid larger eggs than those given the mash diets.

4. With whole grains yolk colour was less than with mash diets during the first 24 weeks of lay but this was reversed during the last 24 weeks of lay.

5. Either canthaxanthin or citranaxanthin or β‐apo‐8'‐carotenoic acid ethyl ester plus canthaxanthin in diets containing lucerne meal produced eggs with acceptable yolk colours.     

Effects of short intermittent lighting on food consumption and performance of dwarf broiler breeders and progeny

1. Two hundred and sixty four dwarf broiler breeder hens were subjected to ad libitum or restricted feeding and to four lighting patterns: 15L (bright light):9D (dark), 15L:9d (dim light), 2L:10d: 1L:11d, (0.5L:3.5d) × 6.

2. Breeder hens fed ad libitum and subjected to either conventional or intermittent lighting ingested respectively, 25 g and 14 to 17 g more than hens restricted to 115 g/d.

3. Body weight was greater in hens fed ad libitum irrespective of the lighting pattern and of the amount of food intake.

4. Persistency of egg production was impaired by intermittent lighting.

5. Ad libitum feeding reduced egg fertility. The decrease was larger in breeder hens on intermittent lighting.

6. Hatchability was increased in hens submitted to the symmetrical lighting pattern (0.5L:3.5d).

7. Egg and chick weights were higher in hens fed ad libitum.

8. Shell index and shell breaking strength increased in restricted hens on the intermittent lighting pattern (0.5L:3.5d) × 6.

9. The best performance was obtained in restricted hens on the conventional lighting pattern.