Components of energetic efficiency associated with broiler and layer performance

Scope and method of study. The purpose of the study was to examine the performance and energetic improvement in broiler reared within five year intervals, the effect of complex isocaloric diets having nearly equal nutrients but coming from several and different ingredients on broiler performance and energetic efficiency, the impact of feed restriction and heat stress on pullet heat response and its partition, and the effects of lighting pattern and feed restriction on fasting heat production in laying hens. The birds were fed adequate diet for each experiment, and they were reared in the floor pens until they reached the age of monitoring different variables investigated. Statistical analysis technique was used to interpret the data.; Findings and conclusions. The result showed that within the five years that separated the two broilers (1994 vs 1999), broilers raised in 1999 showed better improvements of 8.2% in maintenance energy requirement, 6.7% feed efficiency, and 5.8% metabolizable energy (ME) than the 1994, and this highlights the big impact of genetic selection on broiler performance. Complex diets that have equal ME, crude protein and several nutrients that fed broilers didn't not show difference in feed efficiency, heat production, maintenance energy requirement, retained energy. However, all these values were significant different with the bird age (2 vs 4 vs 6 wks). The study with feed restricted pullets in heat distress showed that heat production increased with both feeding level and heat distress exposure, and that evaporative heat loss plays an important role in heat dissipation. Lastly, the effect of lighting pattern on fasting heat production in laying hens has shown that a dark environment (no activity) reduced significantly fasting heat production (P < 0.05) when compared to the light, and this enable the bird to save energy for production purposes.