C. C. Whitehead

The control of egg production using a low‐sodium diet

Synopsis Experiments have shown that egg production can be controlled by using a low‐sodium diet. When a diet containing 0.038% sodium was fed to birds prior to point of lay, egg production was severely restricted. When this diet was fed to hens already in lay, production ceased but the subsequent feeding of an adequate diet resulted in rapid re‐attainment of production to a level higher than that of normally‐fed birds. There were also improvements in egg and shell quality. Birds fed on the low‐sodium diet remained in good condition and mortality did not increase.

Effect of dietary fat on mineral retention in the chick

Synopsis Chicks were fed seven experimental diets to determine whether the level or type of dietary fat affected the retention of calcium, iron, magnesium or zinc. It was found that the presence of any type of fat at or above the 5 per cent level decreased the retention of all four. Retention decreased with increasing dietary fat concentration and increased with increasing absorbability of the fat. For fats of similar absorbabilities, minerals were more poorly retained when the fat was present as free fatty acid. Lowest mineral retention occurred with poorly absorbed free fatty acid.

Sodium deprivation, feather pecking and activity in laying hens

Synopsis When a diet containing only 0.038% sodium was fed to two strains of laying hens for four weeks they showed no increase in feather pecking, toe pecking, pecking activity or general activity, although egg production almost completely ceased. This finding is unexpected in view of recent reports to the contrary under field conditions. It is postulated that very low sodium intakes may be less deleterious than intermediate intakes which permit some laying, and therefore sodium loss, to continue. The absence of adverse behavioural effects emphasises the potential value of sodium deprivation as a means of halting egg production.

The subacute toxicity of 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid to chicks

Abstract Chicks were able to tolerate large dietary doses of the herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), the only adverse effects being a reduction in food consumption and growth rate. A level of 5000 mg 2,4,5-T/kg proved fatal to chicks; a similar level of 2,4-D, while not resulting in death, did cause histological changes. Chicks were able to tolerate this level of either herbicides for up to 1 wk, however, and resume a normal growth rate when returned to uncontaminated food. No specific effect of high dietary levels of these herbicides was noted on plasma calcium or magnesium concentrations. The birds were able to discriminate between contaminated and uncontaminated food; when given a choice they rejected contaminated food and grew at a normal rate.

An assessment of the optimal range of dietary sodium for inducing a pause in laying

Laying hens were fed on a diet containing 0-9 g sodium/kg until 34 weeks of age, then groups were fed on diets containing 0-2, 0-3,0-4, 0-5, 0-6 or 0-9 g sodium/kg for 16 weeks before that containing 0-9 g sodium/kg was reintroduced for all birds. 2. Egg production and food consumption were depressed by the low-sodium diets in proportion to the dietary sodium content. 3. Birds receiving 0-3 to 0-6 g sodium/kg diet lost weight initially but subsequently gained weight; birds receiving 0-2 sodium/kg diet lost weight continouosly. 4. In birds receiving 0-2 g sodium/kg diet, the reproductive organs were completely regressed, whereas these organs resembled those of point-of-lay pullets in birds fed on 0-3 or 0-4 g sodium/kg. 5. When the control diet was reintroduced, birds which had received the low-sodium diets resumed normal egg production and food consumption and regained body weight. 6. The optimal range of dietary sodium for inducing a pause in egg laying is 0-3 to 0-4 g/kg.

Sodium supplementation of broiler rations

Synopsis Broiler chickens were fed on diets containing 0.1 to 0.5% sodium from 0 to 8 weeks. During the 0‐ to 4‐week period the best combined growth rate and efficiency of food conversion was obtained when the diet contained 0.2% sodium; for the period 0 to 8 weeks 0.2 and 0.3% were equally good. The treatments had no effect on carcass moisture retention.

Effect of dietary sodium levels on the incidence of testicular cysts in the chick

Synopsis Testicular cysts have been recognised as a new sign of sodium toxicity in chicks. Practical diets containing different sodium levels were fed to chicks of three different strains and the occurrence of testicular lesions was noted. The strains varied in their susceptibilities, but cysts were found in birds fed diets whose sodium contents would have been regarded as satisfactory by all other criteria.

The effects of lindane on laying hens

Synopsis Feeding lindane, in capsule form, to laying hens at a rate equivalent to 100 mg/kg food for 1 or 2 weeks had little effect on egg production. Longer periods of feeding resulted in a 20 to 30% decrease in the rate of egg production. When treatment was stopped after 4 weeks, the birds recovered and egg production returned to its original rate within a month. The production of flocks treated for 6 weeks or longer became permanently depressed since some birds went out of lay and failed to resume production when the treatment was terminated. Egg shell thickness, egg and yolk weight and hatchability were not significantly affected by the treatment.

Morphological changes seen at sexual maturity in experimentally induced cystic testes of broiler fowls.

It has been shown previously that a proportion of chicks fed on a high salt diet from hatching developed a severe diffuse cystic dilation of their seminiferous tubules. In an effort to determine whether such testes could produce spermatozoa, birds with cystic testes were selected by direct inspection of their gonads at laparotomy and then maintained until sexual maturity when they were killed and their testes examined histologically. A variety of pathological features was found in the seminiferous tubules but spermatogenesis could be demonstrated in the majority of gonads, thus indicating that although severely damaged at 4 weeks of age considerable epithelial recovery is possible, even though these birds were maintained on a high salt diet for the entire experimental period of 40 weeks.

Factors affecting the retention of calcium by the chick

Synopsis The addition of 5 or 10% tallow to a broiler diet containing 0.9% calcium reduced the retention of that element, although not sufficiently to cause a deficiency. Supplementation of the diets with vitamin D3 above the minimum requirement level did not improve the retention of calcium in the added fat diets.