Limited feeding of commercial layers with diets of different nutrient densities

A study was undertaken to determine the feasibility of restricting the feed intake of hens fed different density diets. Performance traits, interior and exterior egg quality, and egg composition of individually caged commercial layers were studied for twelve 28-day periods. Experimental diets of three densities were used. The control diet was fed ad libitum and the assumption was made that the average daily intake for this diet would be 110 grams per hen per day. Two higher density diets were adjusted to contain the same amounts of protein, energy, vitamins, calcium, phosphorus and salt as the ad libitum diet but in 105 and 100 grams of feed. The daily feed consumption of the experimental groups was limited to these amounts. The higher nutrient density in the restricted diets (105 and 100 grams per hen per day) was obtained mainly by using supplements of vegetable fat, L-lysine and DL-methionine. Body weight was heavier for the ad libitum fed birds than for the restrictively fed groups. The hens fed ad libitum tended to over-consume, gaining extra body weight; this was negatively correlated with most of the other performance traits. Hen-day egg production and feed efficiency were improved by the diet of intermediate density (105 grams). Egg production was approximately equal for the ad libitum and the restricted groups receiving 100 grams per day, but egg size and feed efficiency were higher for the hens restricted to 100 grams per day. Mortality was significantly influenced by dietary density. As dietary fat was increased in the ration, livability was reduced. Production costs per unit of eggs were calculated and were highly influenced by the feed to egg ratios, thus the diet of intermediate density (105 grams) gave the lowest feed cost to produce a kilogram of eggs. Exterior and interior egg quality was also influenced by increasing dietary density. Shell thickness, shell weight and percent shell tended to improve as nutrient density was increased in the ration. The highest density diet (100 grams per hen per day) gave the best shell quality. However, the Haugh unit score was lower for the hens fed the highest density diet. The restrictively fed hens receiving 105 grams; gave the highest Haugh unit score. Both the protein content for the whole egg and the cholesterol content in the yolk increased significantly as nutrient density increased in the ration. Irrespective of dietary factors, cholesterol increased as age of the bird increased. On the contrary, the percent fat in the whole egg decreased as dietary density was increased, but lacked statistical significance