Abstract
An experiment was conducted to evaluate the biometrics of organs (ovary, oviduct, liver, proventriculus and gizzard) of laying hens submitted to different forced-molting methods of molt and maintained at three different temperature. Organs were evaluated after molting and resting period. Six hundred birds were distributed according to a completely randomized experimental design in a 5x3 factorial arrangement (forced-molting methods x environmental temperatures) into 15 treatments with 5 replicates of 8 birds each. The molting methods applied were the dietary inclusion of 90%, 70%, 50% of alfalfa, 2,800 ppm zinc oxide, or total feed restriction. Birds were kept at ±20 ºC, ±27 ºC, or ±35 ºC. Data were submitted to analysis of variance and means were compared by orthogonal and polynomial contrasts. The traditional forced-molting method (feed fasting) resulted in adequate performance. However, as the aim of the present study was to find an alternative method to feed fasting, the highest dietary alfafa inclusion level (90%) was shown to be efficient compared with other methods, particularly when hens were kept at high temperature. Therefore, this alternative forced-molting may be applied, especially when bird welfare is taken into consideration.
Highlights
At the end of the first laying cycle, eggshell thickness and strength are reduced, precisely when egg size is the largest
Ovary weight loss is concomitant with body weight loss, and this process is directly linked to the recovery of the hen’s reproductive tract during the molting period (Braker, 1983)
Ovary and oviduct relative weights linearly increased with temperature (p
Summary
At the end of the first laying cycle, eggshell thickness and strength are reduced, precisely when egg size is the largest. This problem may be solved by an economically feasible management practice, which is forced molting. Forced molting consists of a set of management practices applied to promote stress, inducing birds to stop producing eggs (Roland & Brake, 1982). Several methods to force molting are applied, including feed and water fasting, lighting restriction, and the use of chemical agents. Feed withdrawal from the feeders for 10 to 12 days is the easiest method of inducing molting in layers, resulting in egg production cessation, reproductive tract involution, and feather loss (Brake, 1993). Molting induced by feed fasting causes about 25% weight loss in layers, and 1⁄4 of this effect can be directly attributed to reductions in liver, ovary, and oviduct weights (Brake & Thaxton, 1979)
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