Abstract
An experiment was conducted to study ileal digestibility of nutrients and to verify the ability of broilers to select feed in order to meet their requirements for protein and energy. The treatments consisted of six diets: R+S: free-choice feeding with rice bran (energy) and soybean meal (protein); C+G: free-choice feeding with corn (energy) and corn gluten meal (protein); R+G: free-choice feeding with rice bran (energy) and corn gluten meal (protein); C+S: free-choice feeding with corn (energy) and soybean meal (protein); R+C+G+S: free-choice feeding with rice bran and corn (energy) and corn gluten meal and soybean meal (protein); and BD: basal diet represented by a complete diet composed of 63% corn and 33% soybean meal. The results indicated that the adjustment to nutritional requirements does not depend only on the ability of birds to select feed. It might also depend on intake and ingredient quality, since some ingredients did not provide a balanced amount of nutrients. The birds were able to fulfill their requirements for maintenance, that is, they consumed the minimum amount of amino acids (g per day) for maximum growth. The free-choice group with corn gluten meal as the protein source had the worst performance, which indicated that this feed is not recommended as a primary source of amino acids for broilers. The C+G diet presented the highest digestibility coefficient of dry matter and crude protein, whereas the C+S diet resulted in the highest digestibility coefficient of ether extract and nitrogen-free extract, indicating that diet digestibility was affected by the type of feed used as energy and protein sources. In general, the high digestibility values indicate that broilers are able to efficiently digest and absorb the supplied feed.
Highlights
It is known that poultry, as well as other animals, adjust their voluntary intake of feed to maintain appropriate daily intake when offered diets with different energy and protein densities
The treatments consisted of six diets: R+S: free-choice feeding with rice bran and soybean meal; C+G: free-choice feeding with corn and corn gluten meal; R+G: free-choice feeding with rice bran and corn gluten meal; C+S: free-choice feeding with corn and soybean meal; R+C+G+S: free-choice feeding with rice bran and corn and corn gluten meal and soybean meal; and BD: basal diet represented by a complete diet composed of 63% corn and 33% soybean meal
The results indicated that the adjustment to nutritional requirements does not depend only on the ability of birds to select feed
Summary
It is known that poultry, as well as other animals, adjust their voluntary intake of feed to maintain appropriate daily intake when offered diets with different energy and protein densities. Under natural or experimental conditions, chickens eat different feedstuffs that are individually incomplete, so that the challenge consists in evaluating all the available feedstuffs and selecting an adequate diet from them. The cafeteria method, or free-choice feeding, allows the animal to formulate its own diet, selecting the feeds based on the requirements for maintenance and production, which may increase efficiency when compared to complete diets. Producers with little experience adapt well to this system, which is labor-saving and offers good results in breeding programs for high production (Oliveira, 1999). It is necessary to know which factors might influence the selection of the diet by the bird under a free-choice situation.
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