Efeito de métodos de muda forçada sobre o desempenho de poedeiras comerciais.

Abstract

The purpose of this experiment was to compare the productive performance of commercial laying hens after being under different methods of induced molting. Ninety-six Hy-Line white laying hens, 85 wk old, were sorted out in random blocks of delineation under four treatments, three repetitions and eight hens per block. The treatments were as follows: T1 - the conventional method consisted of feed withdrawal during the 12 first days of the experiment. Then feeding the hens with growing diet until the 21st day, then feeding them with laying diet until the last day of the experiment; T2 - diet of high-zinc content (10,000 ppm), during the 12 first days, then feeding the hens with growing diet until 21st day, then feeding them with laying diet until the last day of the experiment; T3 - a molt diet (low-energy level) for 27 days, being given in limited daily portions (45g per hen per day); T4 - molt diet (low-energy leveI) provided ad libitum intake for 27 days. For T3 and T4 from the 28th day until the end the lay period, the same laying diet utilized in the other treatments was offered. The production data presented after the molt period were recorded during five 28-day periods. The egg-Iaying percentage (hen/day) and feed conversion (feed weight/egg weight) were significantly (P<0,05) better for hens under treatments T1, T2 and T4 in comparison with T3. However, the egg weight was higher (P<0,05) for hens under treatments T1 and T4 in relalion to the one found in the hens under T2 and T3. The variables: feed consumption, egg-shell thickness and egg-shell weight were not significantly affected by the molting methods utilized. However, the specific density of the eggs of the hens under treatments T3 and T4 was higher than that presented by the hens under treatments T1 and T2. The period effect was observed in all variables but not for the egg weight. The higher egg-production rates as well as the higher feed consumption took place between the fourth and eight weeks after the molt in all treatments. The use of the molt diet with low-energy level when offered ad libitum and a high-zinc diet (10,000 ppm) such as induction of molting methods produced performance resuIts similar to those reached by the use of the conventional method or total feed withdrawal.