Garlic oil granules coated with enteric polymer: Effects on performance, egg quality, yolk antioxidants, yolk cholesterol, blood biochemistry and hepatic lipid metabolism in laying hens

Abstract

The effects of dietary garlic oil coated granules (GOCG) on egg production, egg quality, yolk antioxidant capacity, yolk cholesterol, yolk fatty acids, blood biochemistry and hepatic enzyme activities were investigated. Forty 36-week-old Hisex brown laying hens were randomly assigned to one of the five dietary treatment groups including: (1) basal diet+0 g GOCG/kg diet (GOCG0, control), (2) basal diet+7.5 g GOCG/kg diet (GOCG7.5), (3) basal diet+15 g GOCG/kg diet (GOCG15), (4) basal diet+30 g GOCG/kg diet (GOCG30) and (5) basal diet+60 g GOCG/kg diet (GOCG60), for four weeks. It was found that egg production, egg mass and feed conversion ratio (FCR) improved linearly (P < 0.05) with increasing dietary GOCG levels. Egg weight, albumen weight, yolk color intensity and Haugh units increased linearly (P < 0.05) and there were quadratic effects (P < 0.05) on yolk weight, shell weight, shell thickness and albumen pH. Dietary GOCG increased yolk antioxidant capacity measured by the phosphomolybdenum method and lowered thiobarbituric acid reactive substances (TBARS) (linearly, P < 0.05). Significant decreases were especially noted in terms of mg/100 g yolk of yolk cholesterol at 7, 14, and 28 days, and overall (quadratic P < 0.05, linearly P < 0.05, linear and quadratic P < 0.05 and linear and quadratic P < 0.05, respectively). Yolk fatty acid compositions, however, did not differ by treatment. Serum total cholesterol (Total-C) and triglyceride decreased linearly (P < 0.05) at 28 days. Hepatic 3-hydroxy-3-methylglutaryl-CoA reductase (HMGRC) activity due to treatment decreased (linear and quadratic, P < 0.05), but fatty acid synthase (FAS) activity increased linearly (P < 0.05). Pearson's correlations with mg/100 g yolk of yolk cholesterol at 28 days were statistically significant (P < 0.01) for the reduction of HMGCR activity. Hence, based on the minimum content of yolk cholesterol (mg/100 g yolk) and dietary GOCG levels tested, a dietary GOCG30 is recommended, as this had no negative impacts on other important parameters of egg production for consumption.