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By Dr. Roos Molenaar, senior researcher HatchTech and Dr. Henry van den Brand, Associate Professor, Wageningen University, the Netherlands
The production cycle of the broiler chicken has been decreased over the years and will probably decrease even more in the future. The period immediately after hatch, when major developmental and physiological changes occur, becomes more and more important. A broiler chicken seems anatomically complete after hatch, but the digestive, immune, and thermoregulatory system needs further development and maturation. Early feed is essential for the development of the gastrointestinal tract and the growth of the bird, but it is largely unknown what the effect of early feed is on the development of the thermoregulatory system.Thermoregulatory development
In practice, birds are often delivered at the broiler farm up to 72 hours after emergence from the eggshell, because of the time needed for hatching, chick handling and transport. This delays the start of feed consumption and negatively affects body weight by a decrease in intestinal development and muscle growth. A delay in feed consumption may also affect the development of thermoregulation. In the early post hatch period, chickens act as poikilotherm and become fully homeotherm during the first 5 to 10 days after hatch.
In practice, birds are often delivered at the broiler farm up to 72 hours after emergence from the eggshell, because of the time needed for hatching, chick handling and transport. This delays the start of feed consumption and negatively affects body weight by a decrease in intestinal development and muscle growth. A delay in feed consumption may also affect the development of thermoregulation. In the early post hatch period, chickens act as poikilotherm and become fully homeotherm during the first 5 to 10 days after hatch.
The optimal body temperature of post hatch chickens is between 40.0°C and 40.6°C. When birds are within this narrow body temperature range, they are in their thermal neutral zone and show normal eating, drinking, and sleeping behaviour. Early feed may positively affect the development and maturation of the thermoregulatory system and specific nutrient components may play an important role in this development and maturation. To investigate the effect of different diet compositions on thermoregulatory development of early fed chickens, a study was performed at Wageningen University, the Netherlands. Rectal temperature and the decrease in rectal temperature during cold exposure were used as variables to express thermoregulatory development.
Diet composition variation
Newly hatched chickens from a Hybro grandparent broiler breeder flock of 40 weeks of age were taken from the hatcher at day 20 of incubation and were immediately assigned to one of five treatments.
Newly hatched chickens from a Hybro grandparent broiler breeder flock of 40 weeks of age were taken from the hatcher at day 20 of incubation and were immediately assigned to one of five treatments.
The treatment groups were: 1) no feed, 2) crushed dextrose pellets, 3) boiled albumen, 4) a commercial prestarter (12.0 MJ of ME/kg, 232 g/kg of crude protein, 65 g/kg of crude fat) and 5) a commercial prestarter plus extra fat (13.7 MJ of ME/kg, 232 g/kg of crude protein, 149 g/kg of crude fat). Water was available ad libitum. Room temperature was set at 35°C at arrival and decreased by 0.5°C until three days post hatch. At day 2 and 3 post hatch, half of the chickens were housed individually in wired cages and exposed to a cold temperature (20°C) for 30 minutes. Their rectal temperature was measured before, immediately after, and 30 minutes after the cold exposure.
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Source: World Poultry, Vol. 27, No. 8, 2011
