Feeding behaviour of layer hens supplemented with snail or oyster shells in the last laying phase: effects on egg quality

Abstract

The experiment aimed to evaluate the effects of additional biological sources of calcium to hens between 60 to 72 weeks-old, on egg production and egg quality. A total of 72 ISA Brown hens having an average laying rate of 86.6 ± 4.14 % were divided into 4 dietary treatments groups in which oyster shells (O and O+) and snail shells (S and S+) were used. In dietary treatments O+ and S+, hens were fed with a balanced diet and supplemented with oyster and snail shells, respectively, through free choice-feeding system. Completely Randomized Design was used. Hens were housed in Californian cages and each diet was delivered to nine cages (replications) of two hens each. The supplementation of shells significantly increased the daily intake of calcium per hen and per egg. Compared to the control diets S and O, the intake of balanced feed significantly decreased in S+ and O+, respectively. The intake of crude protein and metabolisable energy significantly decreased in oyster shell dietary treatments; but not in snail shell ones. Irrespective of the type of shell, no significant effect of shell supplementation was recorded on feed conversion ratio and laying rate. The laying rate improved significantly in O+ compared to S+. Snail shell supplementation, significantly improved the egg weight (60.8 g versus 63.4 g in S and S+, respectively); but, that of oyster shell did not. No significant effect of shell supplementation was noticed on thickness, weight, percentage and index of eggshell. The Haugh unit and albumen height of egg were similar. Economically, the supplementation of snail shell significantly, reduced the efficiency of diet. It can be concluded that, despite the increase of calcium intake, the supplementation of snail or oyster shells to ISA brown aged layer hens did not significantly improve eggshell characteristics; but, that practice increase the egg weight in hens fed with snail shell.