Poultry Articles on Genetics, Breeding & Reproduction
The daily metabolizable energy requirements for broiler breeders are dependent upon maintenance, growth, and egg production. The following guide provides basic formulas for estimation of each. It is reasonable to assume that these numbers are most reliable when birds are receiving feed daily. The original calculations were based on birds receiving relatively unlimited access to feed and the effect of feed restriction is not fully known. Calculation of daily maintenance requirements involves a fractional exponent so the attached table is provided for ease of reference. Daily average temperature fluctuations must also be accounted for and the attached table is so configured. For example purposes the lower end of the thermoneutral zone (65°F/18.3°C) is used as a base temperature to demonstrate a reasonable maximum daily maintenance requirement. Most houses are operated in the thermoneutral zone (65°F to 85°F/18.3°C to 29.4°C) and little adjustment is needed within this range. However, it should be noted that in breeder houses with high speed air movement the "effective temperature" for the bird may be less than the observed dry bulb temperature due to the effect of "wind chill."
Genetics, Nutrition And Reproduction
Poultry breeding remains largely based on classical quantitative genetics. In essence, pedigree broiler candidates are full-fed nutritionally-dense and properly balanced diets to allow individuals that have the greatest potential to utilize crude protein (CP) and metabolizable energy (ME) to grow fast, convert feed efficiently, and yield well to become apparent by their performance. Thus, broiler strains are often selected on high-protein, high-energy diets. Selection on nutrient dense diets apparently necessitates nutrient-dense diets in order for the progeny to fully express their genetic potential. An excellent example of the relationship between genetic progress and appropriate nutritional compensations can be taken from research with quail (Lilburn et al., 1992). Random-bred Japanese quail were placed on a selection program intended to create heavy weight (HW) quail. These quail were full-fed 28% CP diets for 28 days and then the largest birds were selected and mated to produce the next generation. When these birds were reared to sexual maturity on a 24% CP diet, as recommended by the National Research Council (NRC, 1984), there was an obvious delay in sexual maturity (onset of egg production).