Immature pullets and roosters must be managed so as to achieve the desired uniform weight at the time of photostimulation, which is usually around 22 – 24 weeks of age. Growth and uniformity are influenced by feeding program and, to a lesser extent, by feed formulation. Within reason, it is possible to achieve the desired weight at any age when using diets with a vast range of nutrient specifications.
Nutrient intake is largely controlled by the degree of feed restriction. For example, it is theoretically possible to grow pullets on diets with energy levels ranging from 2,600 – 3,100 kcal ME/kg. In practice, diet energy level is usually within the range of 2,750 – 2,950 kcal ME/kg, although for diets necessarily formulated outside of this range, energy intake can be controlled by adjusting feed intake. It is usually more difficult to maintain uniformity with high-energy diets, since this necessarily implies much smaller quantities of feed being distributed at any one time.
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April 21 2008 | Poultry | No Comments »
Today, most poultry feeds also contain supplementary gelatin- or starch-coated synthetic vitamin A, which is quite stable. The inclusion of antioxidants in the feed helps retain the potency of vitamins A and E in mixed feed.
Vitamin D3 is the only form of the product to be used in poultry diets, since birds cannot metabolize vitamin D2. Vitamin D3 supplements are available in a dry, stabilized form. These products are reported to be stable when mixed with minerals. Hy-D, a commercial form of 24 (OH)D3, is also very stable within premixes and mixed feed.
Calcium pantathenate may be destroyed in the presence of supplements containing acid ingredients such as niacin arsenilic acid and 3-nitro. The calcium chloride complex of calcium pantathenate is more stable than is conventional calcium pantothenate under acidic conditions.
Thiamin, folic acid, pyridoxine and some vitamin K supplements can be relatively unstable in the presence of trace mineral supplements. This is especially true where the minerals are supplied as sulfate salts, hence special consideration must be given to the abovementioned vitamins when premixes contain both vitamins and minerals and storage is for four to six weeks.
Most of the other vitamins are fairly stable. However, care should be taken in storing vitamins to ensure their potency. While vitamin supplements are an extremely important part of a well-balanced diet, poultry usually have sufficient body stores to meet their requirements for several days.
Commercial poultry farms receive feed deliveries on a weekly or even more frequent basis. Failure to incorporate the vitamin premix in a delivery of feed will likely have little effect on the performance of most classes of poultry, assuming the “next delivery” contains the vitamin supplement. For breeding birds, this may not be true, especially for riboflavin, which could well affect hatchability if hens are fed a deficient diet for five to seven days.
April 18 2008 | Poultry | 1 Comment »
It is unfortunate that we do not have a rapid system for determining the metabolizable energy content of feeds or ingredients. In all situations, energy is the most expensive nutrient in a diet, and so it is somewhat surprising that we do not have a measure or guarantee of energy content of feeds or energy content of ingredients as a component of trade. Metabolizable energy can only be determined with precision and accuracy by use of a bioassay involving live birds. Even the so-called rapid TME system takes at least a week to complete under ideal circumstances. Energy is contributed by all organic components within an ingredient and values do not correlate well with simple chemical analyses since digestibility per se is unpredictable.
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April 16 2008 | Poultry | 1 Comment »