Effect of feeding restricted amounts of a medium‐ and high‐protein diet on growth and body composition of ducklings

Abstract

AbstractA total of 216 ducklings of mixed sex were fed diets containing either 19.5 or 24.7% crude protein, either to appetite or to 85% of appetite, from 1 to 21 or 24 days of age.There were no significant interactions between dietary protein content and level of feeding. At 21 days ducklings fed the high‐protein diet were 28% heavier than those fed the medium‐protein diet and birds fed the higher level of intake were 17% heavier than restricted groups. At 24 days the body weight of restricted ducklings was similar to that of those fed the higher level of intake at 21 days. From 1 to 21 days efficiency of food utilisation was better for ducks fed the high rather than the medium protein diet, but similar for the two levels of food intake. Efficiency of the restricted groups in the 1 to 24 days period was slightly worse than that of groups of similar body weight fed the higher level of intake from 1 to 21 days.At 21 days carcasses of ducklings fed the high protein diet contained 31% dry matter, of which 34% was fat and 53% was protein, compared with 34% dry matter in the carcasses from the medium protein groups, of which 41% was fat and 48% was protein. Feed restriction had no effect on carcass dry matter and the reduction in percentage ether extract was only about half the magnitude of the reduction due to dietary protein level. Dietary treatments had no significant effect on percentage protein in fat‐free dry matter. At 24 days carcasses of restricted ducklings contained more dry matter but the proportions of ether extract and crude protein were similar to those in younger (21 days) ducklings of similar body weight fed at the higher level of food intake.