Effects of energy and protein allowances during lay on the reproductive performance of broiler breeder hens

1. Broiler parent stock were fed daily allowances of 1.88, 1.73 or 1.52 MJ apparent metabolisable energy (AME) per bird at two different daily protein intakes (27, 21.3 g crude protein (CP) per bird) or daily protein intakes of 24.6 and 19.4 g CP per bird at a daily energy intake of 1.88 MJ AME per bird from 21 to 64 weeks of age.

2. Body‐weight gain and carcass fat and water content increased and fertility decreased with increasing energy allowance. Maximum egg production occurred at an energy intake of 1.73 MJ AME/bird d.

3. Differences in egg weight and hatchability were related to differences in both energy and protein intake. The highest egg weight occurred at the highest allowance of energy and protein. Hatchability was depressed where the daily allowances of protein and energy were in a ratio of more than 15 g protein: 1 MJ AME.

4. Apart from egg size no significant effects on reproductive performance were observed when dietary protein intake was varied from 27 to 19.5 g/bird d.

5. Requirements of broiler breeder hens for protein during lay may be lower than previously thought. For the strain used a protein intake of 19.5 g/bird d appeared adequate provided essential amino acid concentrations were maintained.

6. The close relationships between body weight and energy allowance and the latter and egg production make body‐weight gain a useful guide to management. A body‐weight gain of about 1.1 kg from 21 to 36 weeks of age was associated with optimum performance in this study.     

The effects of vitamin a deficiency on oral gustatory behaviour in chicks

1. Two groups of chicks (Gallus domesticus) were fed on a vitamin A‐deficient diet for 24 d. Birds in one group, which acted as a control, were dosed orally with retinyl palmitate in corn oil, whereas the other group (experimental) was given corn oil only throughout the experiment.

2. At regular intervals birds in both groups were stimulated orally with solutions of acetic acid, quinine hydrochloride and sodium chloride and the number of beak and tongue movements counted.

3. By the end of the experiment the vitamin A‐deficient birds showed a significant decrease in their response to the oral stimulants compared with the control birds.     

The effects of restricted feeding on adrenal cortical activity in the immature domestic fowl

1. The effect of reducing food intake to 75% of the ad libitum intake was determined from hatching to 8 weeks in young Light Sussex chickens.

2. Restricted birds were lighter throughout the experiment.

3. Relative adrenal weight tended to be greater in restricted birds but the difference decreased with time.

4. There was no depletion of adrenal cholesterol: from week 5 there was a significantly greater amount in the adrenals of restricted birds.

5. After 1 week of restriction plasma corticosterone concentration was 73% greater than in controls. It decreased progressively, falling within the normal range at 5 weeks.

6. Restricted birds were hypoglycaemic from weeks 2 to 7 and hyper‐lipacidaemic throughout. A negative correlation between plasma glucose and free fatty acids was found.