Comparison of post‐hatch holding time and subsequent early performance of broiler chicks and Turkey poults

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Abstract
1. The effect of a holding period, lasting up to 48 h post‐hatch, on early growth and mortality rate was studied in broiler chicks and turkey poults. 2. After 48 h of food and water deprivation, birds of both species lost about a tenth of their initial post‐hatch weight. Weight loss was more marked in poults subjected to heat stress. Thus, duration of the holding period adversely affected early growth. 3. During the 48‐h holding period, the relative weight of residual yolk decreased in both species by approximately half of its weight in the just hatched chicks and poults. Relative yolk size was much higher in poults than in broilers. 4. On day 1 weight loss was attributed to degradation of the yolk sac, whereas on day 2 only about two‐thirds of the loss could be attributed to residual yolk. Body composition of newly‐hatched broiler chicks did not differ from those held for 24 h despite shortages of energy. However, after 48 h body fat content was markedly reduced compared to newly‐hatched or 24‐h‐old birds. 5. Irrespective of access to food, the relative size of the gastrointestinal tract increased with holding time in both species, reflecting its importance. 6. It was concluded that post‐hatch birds deprived of food and water for 48 h face a severe shortage of energy, causing alterations in body composition. This in turn adversely affects early growth and increases mortality rate under heat stress.