Production, composition, fatty acid profile and sensory traits of milk from goats fed crude glycerin from waste frying oils used in biodiesel production

Eight Anglo-Nubian goats with 42.06 ± 3.5 kg body weight (BW) and 51 ± 4.0 d in milk were randomly assigned in a double 4 × 4 Latin square experiment with 20-d periods and four diets with different concentrations of crude glycerin (0, 70, 140 and 210 g/kg on DM basis) to evaluate the effects on intake and on production, composition, fatty acid (FA) profile and sensory traits of milk. The inclusion of crude glycerin from waste frying oils in the goat diets linearly decreased the intake of DM (P=0.001), NDF (P<0.001) and NFC (P=0.007), goat milk production (P=0.006), 4% fat-corrected milk production, (P=0.007), milk composition of total solids, (P=0.006) fat (P=0.005), protein (P=0.03), lactose (P=0.006), total solids (P=0.005), nonfat solids (P=0.005), saturated FA C14:0 (P<0.001) concentrations, short- (P<0.001) and medium-chain (P=0.002) FA proportions and atherogenicity index of fat milk. There was a quadratic increase of EE intake (P=0.002), fat and lactose (P=0.03) milk composition and linear increases in unsaturated FA (P<0.001), monounsaturated (MUFA; P<0.001), UFA:ΣSFA (P=0.002), MUFA:ΣPUFA (P=0.001), all long-chain FA (P<0.001), Σcis C18:1 (P<0.001), and the activity levels of Δ⁹desaturase 18 (P=0.008) and elongase (P<0.001) with crude glycerin inclusion in the diets of milk goats. The water intake, milk concentration (g/kg) of CP and SNF, C16:0, C18:0 and C18:2 cis-9, trans-11 FAs, polyunsaturated (PUFA), n-3, n-6, and n-6:n-3 ratio, Trans:C18:0, activity of Δ⁹desaturase 14 and 16, and sensory attributes (odor and flavor) of milk were not affected by crude glycerin intake (P>0.05). Crude glycerin from waste frying oils (36% glycerol and 26% EE) inclusion up to 210 g/kg in total DM replacing corn ground in diets of lactating goats improves milk solids composition and fatty acid profile, which it is desirable for the industry of dairy products, however, it reduce DMI, production and total solids milk, without effects on sensory attributes.