Crude glycerin decreases nonesterified fatty acid concentration in ewes during late gestation and early lactation

Crude glycerin is a gluconeogenic substrate in ruminants and may help to decrease the occurrence of pregnancy toxemia. The objective in this trial was to determine the effects of feeding a diet containing crude glycerin on DMI, milk yield, milk composition, and blood metabolites in periparturient ewes and lamb performance. One hundred eighteen 90 (+/- 1.1)-d pregnant Santa Ins ewes were used. After lambing, 32 ewes (62.8 +/- 1.3 kg BW) were allotted in a randomized complete block design defined by prelambing diet, BW, BCS, lambing date, type of birth (single or twin), and sex of offspring. Diets were isonitrogenous (13.0 +/- 0.3% CP, DM basis), composed of concentrate and raw sugarcane bagasse (70: 30 ratio, DM basis), and fed ad libitum daily. Crude glycerin (83.6% glycerol) levels were 0 or 10% (DM basis), corresponding to the experimental diets G0 and G10, respectively. From 8 until 56 d of lactation, DMI was determined. In the same period, once a week at 1000 h, 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, ewes were milked again and milk yield and composition were determined. Glucose, NEFA, and a-hydroxybutyrate (BHBA) were determined at -14, -7, 0, 7, 14, 28, and 56 d relative to lambing and insulin was determined at -14, -7, 0, and 7 d. Crude glycerin did not affect DMI (2.2 kg/d for G0 vs. 2.2 kg/d for G10; P = 0.93) or milk production (171 g/3 h for G0 vs. 164 g/3 h for G10; P = 0.66). However, there was a decrease (P = 0.01) in milk fat percentage (8.1% for G0 vs. 7.0% for G10) for ewes fed glycerin. Ewes fed the G10 diet had decreased (P < 0.01) NEFA concentration (0.27 mmol/L for G0 vs. 0.18 mmol/L for G10). There was an interaction between diet x time for glucose (P = 0.04), insulin (P = 0.05), and BHBA (P = 0.01); feeding glycerin increased glucose (5.61 mmol/L for G0 vs. 7.42 mmol/L for G10; P < 0.01) and insulin concentrations (10.5 mu IU for G0 vs. 24.5 mu IU for G10; P < 0.01) at parturition compared with G0. The BHBA was less (P = 0.02) on the day of lambing (0.40 mmol/L for G0 vs. 0.29 mmol/L for G10) and it was greater (P < 0.01) on d 56 for ewes fed the G10 diet (0.46 mmol/L for G0 vs. 0.61 mmol/L for G10). There was no effect of diets fed to ewes on lamb growth from birth to weaning. Crude glycerin improved energy balance of periparturient ewes, suggesting a reduced risk of developing clinical metabolic-related disorders. Crude glycerin can be added at 10% of ewes' diets without affecting DMI and milk yield.