The effect of alternative nutritional programs to induce molting on the performance of semi-heavy layers

Molt is a naturally-occurring physiological process of birds, characterized by a time period in which feeding habits are altered, reproductive functions are decreased or cease, and feathers are renewed, aiming to restore bird's reproductive system followed by the initiation of a new egg-laying cycle (Webster, 2003).

Due to the fact that in nature this process is rather slow, lasting for approximately 4 months, and occurs at different times among birds, techniques have been developed to accelerate the process in a synchronized manner, affecting all birds at a time thus improving flock uniformity. This concept is called forced (or induced) molting. The majority of forced molting programs involve an 8-14-day fasting or until a maximum of 25% body weight loss occurs (Rodrigues et al., 1995). Long periods are considered favorable to obtain optimum results after molting. Nevertheless, these methods cause severe hunger stress resulting in bird aggressiveness, mainly when birds are caged at high stocking densities, and potentially causing high mortality.

Even though forced molting can be economically feasible, it works against animal welfare principles. Given that the main objective of forced molting is accelerating the natural process and halting egg production within a short time period, new methods have been proposed whether using drugs, causing nutritional imbalances, or using low energy/high fiber feeds, aiming to replace fasting and assure animal welfare while improving flock performance after a time interval, in order to increase post-molting flock livability.

With the above concepts in mind, the objective of this research was to evaluate the effects of different molting feeds on the performance and livability of commercial layers.

The experiment was carried out in the Special Poultry Unit, Visconde da Graça Agri-Technical Cluster, Federal University of Pelotas (UFPel), Brazil, during August 2009, for a total of 28 days, equivalent to the molting period. Four hundred and forty eight (448) 100-week-old, Hisex Brown layers were housed in a black-out house, distributed in 64 7-hen cages, each of which was the experimental unit. The experimental design was one of random blocks as per birds' initial body weight, with 16 repetitions per treatment. Treatments included four alternative forced molting protocols with or without feed restriction. Water was provided ad libitum throughout the experimental period. Treatments were as follows: T1, controls, feed restriction for 10 days followed by 8 days with ground corn and 10 days with prelay feed; T2, 14 days with a feed containing 97% soy hulls + vitamin premix followed by 4 days with ground corn and 10 days with prelay feed; T3, 14 days with a feed containing 85% wheat bran + vitamin premix followed by 4 days with ground corn and 10 days with prelay feed; and T4, 14 days with a feed containing 85% high tannin sorghum + vitamin premix followed by 4 days with ground corn and 10 days with prelay feed. The following variables were analyzed in order to study the efficiency of these alternative molting methods: starting body weight (g), weight loss (g), feed intake (g), egg production (%) and flock livability (%). Body weights were determined every 5 days, and all other variables were recorded daily. For molting to be considered efficient,  a maximum value of 15% egg production at the end of the period was required.

Results were subjected to both analysis of variance (ANOVA) and Tukey´s test to compare the means at a 5% level of significance, using the GLM procedure in the SAS statistical software.

Table 1 shows the results obtained with the different feeds used as alternative forced molting methods on layer performance and livability.

Table 1. Effects of various induced molting methods on semi-heavy layer performance

Birds in the control group had lower feed intake, higher weight loss, and lower livability (<88%), as a result of the conventional method used (10-day-fasting), as explained by Koelkebeck and Anderson (2007) who showed that during fasting poultry tend to use all nutrients (lipids, proteins, etc.) for body maintenance so that these nutrients are not deviated for production. Given that the main purpose of forced molting is the rapid decrease in egg production and the restoration of the reproductive system, T1 (10-day fasting) and T2 (soy hulls), where most efficient in this parameter, which is justified by the lowest feed intake and, in addition, the use of soy hulls as a fibrous ingredient reduces digestibility then decreases feed intake, resulting in weight losses. In addition, soy hulls have a low energy value and are an extremely-reduced nutrient source, forcing the bird to reduce egg production with no high mortality, opposite to fasting. Garcia (1994) reported similar results when inducing forced molting in birds using low energy diets and maintaining good livability indexes. T4 (high tannin sorghum) resulted in the best flock performance and the highest egg production in this period. This data corroborate the results published by Capela and Creger (1978), who showed that the longer the period of sorghum feeding the slower the resting period during molting, which explains the limited egg (lay remained around 19%) in this period. Birds fed diets such as wheat bran (T3), showed similar results to those obtained with sorghum, with the exception that egg production was more efficient, since it remained at 15%. Results obtained by Koelkebeck and Anderson (2007) match this data, since low energy diets can fulfill birds' requirements for molting to occur.

Soy hulls were most efficient in decreasing egg production during molting. The use of alternative feedstuffs such as soy hulls, wheat bran, and sorghum, showed to be viable alternatives to conventional (fasting) methods, thus easing the forced molting process and assuring flock livability.

Garcia EA. 1994. Avaliação dos parâmetros físicos e produtivos de poedeiras semi-pesadas submetidas a muda forçada e alimentadas com ração de baixa densidade por diferentes períodos. 1994. 59f. Tese (Doutorado em Zootecnia) - Faculdade de Medicina Veterinária e Zootecnia da Universidade Estadual Paulista.

Koelkebeck KW & Anderson KE. 2007. Molting Layers - Alternative Methods and Their Effectiveness. Poultry Science 86:1260-1264.

Rodrigues PB Bertechini AG, Oliveira BL. 1995. Fatores nutricionais que influenciam o desempenho e a qualidade do ovo de poedeiras comerciais no segundo ciclo de produção. In: Reunião da Sociedade Brasileira de Zootecnia, 32. Brasília - Brasil. p. 478-479.

Webster AB. 2003. Physiology and behavior of the hen during induced molt. Poultry Science 82(6):992-1002.