Addition of fat to the diets of lactating sows: II. Effects on hormone-sensitive lipase activity, energy mobilization in response to epinephrine, and plasma insulin and glucose concentrations

Four experiments were conducted to determine the effects of dietary fat on lipolysis in lactating sows. In Exp. 1, a 6 x 6 Latin square was used to determine the optimal dosage of epinephrine for use in a subsequent epinephrine challenge. Peak concentrations of plasma glucose and response area increased linearly (P < .10) with epinephrine dosage. However, plasma NEFA peak and response area were quadratically affected (P < .05 and .06, respectively) by epinephrine dosage, with a minimum NEFA peak concentration observed at .4 microg/kg and a maximum at 1.6 microg/kg. In Exp. 2, the effect of dietary tallow on the response to epinephrine infusion (1.6 microg/kg BW) was examined. No differences (P > .10) between treatments were observed in NEFA, glycerol, or peak concentrations of plasma glucose following epinephrine administration. In Exp. 3, the effect of dietary fat on hormone-sensitive lipase activity was examined. Sows (n = 36) were fed diets containing either 0 or 10% added tallow. Hormone-sensitive lipase activity on d 28 of lactation was increased by the addition of tallow to the diet (P = .06). No effect of dietary tallow was observed on hormone-sensitive lipase activity of adipose tissue on d 21 of lactation (P > .10) in Exp. 3 (n = 16 sows) and Exp. 4 (n = 30 sows). In summary, diets containing 10% added tallow did not alter the rate of lipolysis, as measured by exogenous epinephrine challenge, in adipose tissue of lactating sows.