SummaryEnergy balances have been determined, using the comparative slaughter procedure, over 3-week periods on groups of laying hens kept at ambient temperatures of 7·2, 15·6, 23·9, 29·4 and 35 °C.Energy intake declined as the environment became warmer (kcal ME/kg¾/day = 203· 1·13°C); heat production, as measured by the difference between energy intake and energy retention, also declined with increasing ambient temperature (kcal/kg¾/day = 151 – 1·11°C). There was a linear relationship between heat production and ambient temperature with no thermoneutral zone or critical temperature.The energy available for egg production remained almost constant at 50 kcal/kg¾/day equivalent to a rate of egg production of 82% at each ambient temperature.

Two experiments have been performed to study the acclimatization of laying hens to cool or warm environmental temperature, using the comparative slaughter procedure to measure energy utilization. In the first experiment the energy balances over a 3-week period at either 10 or 35 °C were compared; in the second experiment a comparison was made of the energy balances over six consecutive weekly periods at similar cool and warm temperatures.The first experiment confirmed that production could be maintained (88 %) in the warm environment even though food intake was markedly reduced (95 and 63 g/day at 10 and 35 °C respectively). In both environments a loss of body weight indicated, that energy intake was insufficient to meet demands for at least part of the period.During the first week of the second experiment there was a small loss of body weight in the cool environment and food consumption was slightly depressed. The results for energy intake, egg production and heat production suggest that acclimatization was complete after 1 week. In the warm environment egg production fell initially (62 %) but returned to a high level (86 %) during the second week. However, energy intake, body weight and heat production did not reach steady levels until the fourth week. Comparing the first 3 weeks with the subsequent 3 weeks the daily ME consumption was 137 and 161 kcal/kg^ and the daily heat production was 126 and 116 kcal/kgJ. Similar, although less marked differences were observed in the cool environment. These results therefore emphasize the need to allow adequate time for acclimatization to the environment in studies of energy metabolism.heat production decreases throughout the temperature range from -10 to 40 C. Shannon & A number of reports (Bray & Gessell, 1961;Brown (1969) investigated the time required for Payne, 1966a, 6;Mowbray & Sykes, 1971) have hens to adjust their fasting catabolic rate when the shown that high levels of egg production can be temperature was increased from 22 to 28 °C and achieved in warm climates, up to 30 C C constant found that there was no further decline after 12 temperature, provided that attention is given to days. There appears to be no information on the nutrient intake, adjusting dietary levels to com-fully fed, light weight, modern hybrid hen during pensate for the reduced food intake. However, periods of high egg production, there is little quantitative information on the The work reported in this paper was therefore effects of environmental temperature on energy undertaken to provide information on the effect metabolism and the efficiency of energy utilization, of temperature on energy metabolism and to study found that heat production the time required for acclimatization to a new of fasted birds or birds fed at approximately environment. Hens at peak production were maintenance energy intakes was lower at 29 °C exposed to both cool and warm environments; the than at 22 °C. Using white leghorn hens in their temperature in the former was slightly below the second laying period Romij...

Sixteen hundred commercial broiler chicks (Cobbs) were used to investigate the food value of blood meal in broiler production under Sudanese conditions. Seven experimental diets, containing various levels of blood meal, were fed to groups of chicks from 0 to 9 weeks of age and the performance was compared with those on a control diet containing 15 per cent meat meaL The results indicated that 6 per cent blood meal can be used in broiler diets without growth rate being adversely affected.

No abstract