Milk production, blood glucose, insulin and non-esterified fatty acids concentration in ewes fed diet containing crude glycerin

Abstract Text: Crude glycerin is a glucogenic substrate in ruminants and can decrease symptoms of pregnancy toxemia. The objective in this trial was to determine the effects of partial replacement of corn by crude glycerin (CG) on dry matter intake (DMI), milk yield, milk composition and blood metabolites (glucose, insulin and non-esterified fatty acids) in periparturient ewes. One hundred and eighteen, 90 days pregnant, Santa Inês ewes were used. After lambing, 32 ewes (BW 62.8 ± 1.3 kg) were allotted in a randomized complete block design, defined by pre-lambing diet, sex and offspring number. Diets were isonitrogenous (13.0 ± 0.3% CP, DM basis), composed of 70% concentrate and 30% raw sugar cane bagasse and fed daily, “ad libitum”. Crude glycerin (83.6% glycerol, DM basis) levels were zero or 10% (DM basis), corresponding to the experimental diets G0 and G10, respectively. From the second until the eight week of lactation dry matter intake was determined. In the same period, once a week, the ewes were separated from the lambs and mechanically milked after intravenous administration of 10 IU of synthetic oxytocin. Three hours after the first milking, the ewes were milked again and milk production and composition were determined. Glucose and NEFA were measured at -14, -7, 0, 7, 14, 28 and 56 days relative to lambing and insulin at -14, -7, 0 and 7 days. Data were analyzed as repeated measures over time using the MIXED procedure (SAS Inst. Inc.). The LSMEANS option was used to obtain the means. Crude glycerin did not affect (P > 0.05) DMI (2.2; 2.2 kg/d) and milk production (168.6; 164.7 g/3 hours). However, there was a decrease (P = 0.01) in milk fat percentage (8.0 vs 7.0%). Ewes fed diets with glycerin had decreased (P < 0.01) NEFA concentration (0.27 vs 0.18 mEq/L). Glucose (61.8 vs 67.6 mg/dL) and insulin (10.8 vs 15.5 µIU) were not affected by treatments, but there was an interaction between treatment x week (P < 0.05). Crude glycerin increased glucose (101.2 vs 133.7mg/dL) and insulin concentration (10.5 vs 24.5 µIU) at parturition. Crude glycerin can partially replace corn without affecting DMI, milk yield and milk composition. Crude glycerin improves energy balance of periparturient ewes. 

Keywords: Glycerol, free fatty acids, NEFA