Laying hen productivity as affected by energy, supplemental fat, and linoleic acid concentration of the diet

A trial using 720 Isabrown hens was conducted to determine the influence of energy (AME(n)), supplemental fat (SFAT), and linolenic acid (LIN) concentration of the diet on performance and weight of eggs and egg components throughout the laying cycle (22 to 65 wk of age). There were six treatments whose calculated AME(n), SFAT, and LIN content were, respectively: 1) 2,810 kcal/kg, 0%, 1.15%; 2) 2,810 kcal/kg, 4%, 1.15%; 3) 2,810 kcal/kg, 4%, 1.65%; 4) 2,680 kcal/kg, 0%, 1.15%; 5) 2,680 kcal/kg, 4%, 1.15%; and 6) 2,680 kcal/kg, 4%, and 1.65%. All diets were formulated to have the same crude protein, lysine, TSAA, calcium, and nonphytin phosphorus levels per kilocalorie of AME(n). The data were analyzed with SFAT constant (4%) and AME(n) and LIN variables (Diets 2, 3, 5, and 6) and with LIN constant (1.15%) and AME(n) and SFAT variables (Diets 1, 2, 4, and 5). When LIN was maintained at a constant of 1.15%, an increase in the AME(n) of the diets from 2,680 to 2,810 kcal/kg decreased feed intake by 4% (P < 0.001). Increasing AME(n) also improved feed conversion per dozen eggs and per kilogram of eggs by 4.9 and 4.7% (P < 0.05), respectively, and increased BW gain by 55.7% (P < 0.05). Egg production rate, egg weight, egg mass output, and energy intake were not modified by treatments. An increase in SFAT within both energy levels from 0 to 4% improved all of the traits studied except feed conversion. Supplemental fat increased both yolk and albumen weight, but the effect was more pronounced on the later. When SFAT was maintained constant at 4%, an increase in AME(n) of the diets decreased feed intake and improved feed conversion per dozen and per kilogram of eggs by 5.7, 5.5, and 5.2%, respectively (P < 0.001). An increase in LIN content from 1.15 to 1.65% did not modify any of the parameters studied. The results indicate that SFAT consistently improves productivity of hens and egg weight and that the LIN requirement for maximal productivity is 1.15% or less. The beneficial effects of adding SFAT to diets containing more than 1.15% LIN are due to the fat itself rather than to an increase in LIN or AME(n) of the diet.