Abstract
Heat stress limits the productivity of laying hens, as reflected by egg production and egg quality. The present study aimed at showing the correlations between egg quality parameters and environmental variables recorded on the day eggs were laid and on the previous days. Birds were housed in battery cages in a commercial poultry house. Main component analyses were used to verify associations between environmental and production variables, and Pearson's linear correlation tests were used to further investigate those associations. Analyses were carried out separately for to layer strains, Dekalb ® White and Hy-Line ® w36, and the variables egg weight (g), eggshell weight (g), specific gravity (g/cm³) and eggshell percentage (%) were compared with the environmental variables of the same day of the production, and one, two, three, and four days before egg production. Sound intensity measured inside the houses was positively associated with the quality parameters of eggs produced on the next day. Thermal environmental variables affected the egg quality differently in each strain, particularly air temperature, internal roof tile temperature, relative humidity, and air velocity. Ammonia concentration measured inside the houses was lower than 1ppm, and did not affect production performance.
Highlights
INTRODUCTIONHeat stress limits layer performance, as the bird diverts feed metabolic energy to maintain its body temperature constant, resulting in lower egg production, and in lower egg quality (Esmay, 1982; Hsu et al, 1998; Teeter & Belay, 1993; Tinôco, 2001)
Heat stress limits layer performance, as the bird diverts feed metabolic energy to maintain its body temperature constant, resulting in lower egg production, and in lower egg quality (Esmay, 1982; Hsu et al, 1998; Teeter & Belay, 1993; Tinôco, 2001).Under high environmental temperatures, layer respiratory rate increases from approximately 29 cycles per minute to more than 100 cycles per minute
The present study aimed at showing the correlations between egg quality parameters and environmental variables recorded on the day eggs were laid and on the previous days
Summary
Heat stress limits layer performance, as the bird diverts feed metabolic energy to maintain its body temperature constant, resulting in lower egg production, and in lower egg quality (Esmay, 1982; Hsu et al, 1998; Teeter & Belay, 1993; Tinôco, 2001). Hsu et al (1998) found that temperature increase significantly decreases feed intake, egg production, mean egg weight, and live weight, and influence some egg quality traits, such as eggshell thickness and egg specific gravity. Muiruri & Harison (1991) studied the performance of layers maintained under thermoneutral (25°C) or hot (35°C) temperatures, and concluded that environmental temperature did not influence egg weight or feed conversion ratio, but egg production. Hy-Line® w36 birds were removed from 16 cages (eight per house), with an approximate distance of 20m from the west wall, which were used to house Dekalb® White layers of the same age.
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