The effect of dietary lipid sources on layer fertility and hatchability
This study was conducted to investigate the effect of dietary fatty acids (FA) on the fertility and hatchability of laying hens at the end-of-lay period (69 - 77 weeks of age). Five isoenergetic (12.4 MJ ME/kg DM) and isonitrogenous (170 g CP/kg DM) diets were formulated using different lipid sources (30 g/kg inclusion) to manipulate the dietary FA profile. The control diet was formulated using a 50 : 50 blend of linseed and fish oil, while fish oil was used in the polyunsaturated n-3 treatment. Sunflower oil was used in the polyunsaturated n-6 treatment, while in the mono-unsaturated n-9 diet high oleic acid (HO) sunflower oil was used. Lastly, tallow was used as a lipid source in the saturated FA diet. One hundred and twenty five hens (n = 25/treatment) and 50 cockerels (n = 10/treatment) of the Hy-Line Silver-Brown genotype were randomly allocated to the five dietary treatments at 20 weeks of age. From 69 weeks of age, hens were inseminated with 0.06 mL undiluted semen from cockerels within the same dietary treatment. Between 71 and 78 weeks of age (49 days) a total of 588 eggs-per-treatment were collected, individually marked (date and hen number) and incubated in a single-stage still-air incubator. Eggs were candled on D7 and D14 to determine embryonic mortalities and a 24 h window for hatching was allowed (D21 + 24 h). Although the fish oil treatment resulted in the lowest egg weights (59.3 g) and fertility (84.6%), it recorded the highest hatchability (76%). In contrast, the sunflower oil treatment recorded the lowest hatchability (58.2%) of all treatments, despite its high egg fertility (89.6%). Results of the study suggest that the dietary fatty acid content, in particular the n-3 and n-6 levels, need critical consideration in terms of concentration and ratio in the formulation of breeder diets to limit embryonic mortalities during incubation.
Keywords: Chicks, embryo, mortality, mono-, polyunsaturated fatty acids