Nutritional evaluation of meat meals for poultry. II. Effect of increasing protein concentration, removal of bone, and folic acid, pyridoxine, and pantothenic acid supplementation of diets based on high and low quality meals

Abstract

The effect of increasing the protein and B vitamin concentrations in chicken diets based on wheat, milk powder, and high and low quality meat meals, and of removing bone from such meals, has been studied. Meat meal protein provided approximately 50% of the total protein of 20% protein diets, and up to 85% of the protein of higher protein diets. Without additional pyridoxine and folic acid, increased growth was obtained by increasing the proportion of high quality meat meal in diets providing up to 35% protein (metabolizable energy calorie/protein ratios of 32–33). With low quality meat meals, increased growth was observed on diets containing up to 25 or 30% protein. Severe growth depression and high mortality rate was observed on low quality meat meal diets containing 30–35% protein. Addition of 5 p.p.m. pyridoxine and 8.8 p.p.m. folic acid to low quality meat meal diets containing 30–35% protein significantly improved growth and decreased mortality. This improvement was mainly due to folic acid, and in one case to folic acid and pyridoxine. The available evidence did not indicate whether the response was due to an increased need for or decreased intake of these vitamins, or both. Although growth was significantly improved by the removal of bone from both a high quality–low ash and a low quality–high ash meat meal, the removal did not significantly affect the (calculated) proportion of the total collagen protein in the diet. From this and other evidence, it is concluded that growth depression on high bone content diets is mainly due to excessive calcium content, and not because high bone content is associated with a high proportion of collagen provided by bone protein. Even after removal of bone, however, growth on the low quality meat meal diet did not approach that on a high quality meal diet, which indicated that higher bone content was not the main cause of the low growth-promoting ability of the low quality meal. Addition of meat meal ash to diets depressed growth, but not sufficiently to account for most of the variability in growth-promoting ability of meat meals when they supplied 50% or more of the total protein in the diet. It is tentatively concluded that the growth-promoting ability of meat meals in chick diets is mainly a resultant of: (i) Any effect of excess ash (particularly the calcium component) contributed. (ii) The quality (digestibility or biological value, or both) of their protein, which is not related to the proportion of collagen; and of course the proportion of meat meal protein in the diet, and the extent to which it is complemented by other proteins in the diet. (iii) At high levels of meat meal protein, the folic acid and/or pyridoxine contents of the diets and/or the requirements of the chicks.