External quality of eggs from laying hens fed ground corn during the post-molting recovery period

Introduction

As a general rule, eggs laid during the early production period are smaller, but their external quality is good. As hens age, they produce larger eggs, but eggshell quality problems emerge, since the amount of calcium deposition in the eggshell is not increased while it must be distributed onto a larger surface area, resulting in eggshell fragility issues.

As reported by Garcia (1994), low nutrient density feeds given to hens during the post-molting recovery period does not affect second cycle eggs in terms of production levels or egg quality.

Most eggs produced in this period show some kind of a problem, so that they cannot be marketed. Increased use of eggs produced during forced molt fasting time depends on the same factors that typically affect eggshell quality including bird age, genetic strain, ambient temperature, diseases, and dietary Ca/P/Vit D₃ concentrations. Therefore, a properly managed molting program results in improved egg traits, similar to those laid by 12-month-old, first cycle hens.

The operation allows for improving eggshell and albumin quality, as well as general egg grades when compared with those laid during the late stages of the first production cycle (Silva, 2002).

The objective of this experiment was to evaluate the use of ground maize, administered for two different time lengths, during the recovery phase of layers after forced molting. The external quality of eggs was evaluated.

Materials and Methods

The study was performed in the experimental poultry farm of IFSul, Visconde da Graça campus. Two hundred and twenty four (224) Hisex Brown laying hens were used during 28 experimental days. Birds were housed in a black-out house, randomly distributed in 32 laying cages. The experimental unit was one cage containing 7 birds. Birds were divided into 2 treatment groups with 16 repetitions each.

Treatments included the supply of ground corn after forced molting, as follows: T1, 8 days with ground corn; T2, 4 days with ground corn, after 7 and 10 days of conventional feed-restricted molting, respectively.

The variables analyzed included egg weight (EG), eggshell weight (EW), eggshell thickness (ET, measured using a micron-graded calibrator), and specific gravity (SG, measured by egg immersion in sodium chloride solutions at 1.062 - 1.102 concentrations). Results were subjected to analysis of variance and the means were compared using Tukey´s test (5%.)

Results and Discussion

Table 1. External quality of eggs laid by hens fed ground corn

Treatments	EG (g)	SG	EW (g)	ET (µm)
T1	62.69	1.088	6.3	40.51
T2	64.43	1.086	6.28	40.53
CV, %	6.07	0.74	11.63	10.73
Standard error	3.56	8.15	0.73	4.35
P	0.24	0.63	0.95	0.99

^{EW = egg weight; SG = specific gravity; EW = eggshell weight; ET = eggshell thickness.}

As shown in Table 1, using different corn proportions did not interfere with the variables analyzed. Zamprônio and Moraes (1996), working with two different fasting periods for layer molting, found no alterations in eggshell thickness. Garcia (1994) used fasting and low density diets to induce forced molting and found no differences in eggshell thickness during the post-molting period.

Specific gravity was influenced by molting treatments, where the largest (P<0.05) values SG in eggs from T1 and T2 were observed, matching Biggs et al. (2004), who also obtained similar results.

Oliveira (1992) stated that, given that corn is a high energy feedstuff, it should help hens to recover after forced molting, which should yield benefits in terms of improved eggshell quality.

In his experiments Berry (2003), considering the physiology of induced molting, determined that diets containing in excess of 80% corn do not interfere with eggshell quality or eggshell calcium distribution, but they impact the physiological process of post-molting body condition recovery and maintenance. In agreement with Silva (2002) this can have beneficial effects on eggshell quality by the second laying cycle peak.

Conclusions

It can be concluded that the length of ground corn administration during the post-molting recovery phase does not interfere with external egg quality during the early stages of the second laying cycle.

Bibliography

Berry WD. 2003. The Physiology of Induced Molting. Poutry Science 82:971-980.

Biggs PE, Douglas MW, Koel Kebeck W. 2003. Evolution of none feed removal methods for molting programs. Poultry science 82:749-753.

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. 59f. Tese (Doutorado em Zootecnia) - Faculdade de Medicina Veterinária e Zootecnia da Universidade Estadual Paulista.

Oliveira BL. 1992. Pontos críticos do manejo de poedeiras. In: Conferência APINCO de Ciência e Tecnologia Avícola, FACTA Santos, Brasil. p. 137-142.

Silva VS. 2002. Efeitos da Muda forçada para poedeiras comerciais. Revista Avicultura Industrial. p.12.

Zambrônio EC & Moraes VMB. 1996. Efeitos da muda forçada sobre desempenho produtivo e qualidade dos ovos em codornas In: Conferência APINCO, de Ciência e Tecnologia Avícola, 1996; trabalhos de pesquisa; FACTA. Curitiba, Brasil. p 12.

External quality of eggs from laying hens fed ground corn during the post-molting recovery period

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