Influence of supplemental fat on weights of eggs and yolks during early egg production

An experiment was conducted to determine the influence of dietary fat on weight of eggs and egg yolks of White Leghorn hens from 24 to 38 wk of age. Beginning at 24 wk of age, nine experimental units of eight hens each were fed one of five diet treatments. Treatments consisted of a corn-soybean meal diet containing no added fat, diets containing 3 or 6% animal-vegetable fats (A-V fat) formulated to be isocaloric and equinitrogenous with the no added fat diet, and diets containing 3 or 6% A-V fat in which the metabolizable energy (ME) concentration increased 105 kcal/kg with each 3% increment of A-V fat. Weights of eggs, yolks, and whites were measured biweekly. Supplemental A-V fat did not affect rate of egg production, but feed efficiency was improved significantly as ME increased from diets of increasing ME. No effect of A-V fat on egg or yolk weight was observed until after 4 wk of treatment (28 wk of age). From this time through 12 wk of treatment, a linear increase in yolk weight with increments of A-V fat (P less than .01) occurred, irrespective of diet series (isocaloric or increasing ME). Concurrently, there was a nonsignificant (P less than .10) trend for increased egg weight as A-V fat level increased, but weights of egg whites were not affected significantly. Average increases in yolk and egg weights during the period when hens were 28 through 36 wk of age were approximately .5 and 1 g, respectively, when 6% A-V fat was used, irrespective of diet series.(ABSTRACT TRUNCATED AT 250 WORDS)