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Effect of threonine and methionine levels in the diet of laying hens in the second cycle of production

National Center of Disciplinary Research in Animal Physiology, Instituto Nacional de Investigaciones Forestales, Agricolas y Pecuarias, Ajuchitlán, Querétaro, CP 76280, Mexico

¹ Corresponding author: gomez.sergio{at}inifap.gob.mx

An experiment was conducted to evaluate productive variables and egg component yields of laying hens in the second productive cycle that were fed a low-protein diet with increasing levels of Thr and Met. A total of 480 hens were assigned to a factorial arrangement of 3 levels of Thr (0.42, 0.48, and 0.54%) and 4 levels of Met (0.19, 0.32, 0.45, and 0.58%). Feed intake was lower (P < 0.01) and FE was greater (P < 0.05) at a dietary Thr level of 0.48%. The eggshell percentage declined linearly (P < 0.01) as the level of dietary Thr increased. Egg production, egg mass, and FE were greater at a Met level of 0.32%, and egg weight was greater when dietary Met was 0.45% (P < 0.01). The BW loss (P < 0.01) and the egg albumen percentage (P < 0.10) declined linearly, whereas the yolk percentage (P < 0.10) and eggshell percentage (P < 0.01) increased linearly as dietary Met increased. For maximum egg production and FE, the Thr intakes were 411.5 and 455.8 mg and the Thr:Lys ratios were 65 and 74%, respectively. With regard to Met, for maximum production and egg weight, the intakes of Met were 313.4 and 343.2 mg and the Met:Lys ratios were 49 and 69%, respectively. The estimated digestible Met requirement per gram of egg mass produced was 6.2 mg.

Key Words: laying hen • second cycle of production • threonine • methionine