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.

Abstract

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.

Body fat mobilization during lactation in high-producing sows fed varied omega-6 to omega-3 fatty acid ratios

“…For time-course data (epinephrine and glucose challenges), area under the curves (AUC) were calculated using the before infusion samples as the baseline (Tilton et al 1999) and were analyzed using a completely randomized design. Sow was considered a random effect and diet was considered a fixed effect.…”

“…Conversely, in another study, feeding diets enriched with n-3 FA to rats for 1 wk increased lipolytic responses and decreased lipogenesis (Fickova et al 1998), whereas Awad et al (1990) and Allee et al (1972) were unable to show any effect of dietary FA composition on lipid metabolism in the adipose tissue of mature rats or pigs. In another study, 10% tallow (low PUFA) added to the diet of lactating sows did not alter the rates of lipolysis measured using an exogenous epinephrine challenge (Tilton et al 1999). Papadopoulos et al (2008b) looked at the effects of supplementing a lactation feed with 2% sunflower or fish oil (10:1 and 2:1 n-6:n-3 ratios, respectively) administered 8 d before parturition.…”

“…An epinephrine challenge was conducted on d 5 of lactation as described by Tilton et al (1999) and Mersmann (1986). An epinephrine dose of 1.6 μg kg −1 BW was used (Tilton et al 1999). Blood samples were collected 15 min pre-infusion and at time 0, 2, 4,6,10,15,20,30,45,60, and 120 min after infusion.…”

“…Similarly, a glucose challenge to evaluate the effect of the n-6:n-3 ratio on tissue sensitivity to insulin was performed on d 6 of lactation. Sows were infused with glucose (1 mg kg −1 BW) after a 12-h fast (Tilton et al 1999). Blood samples were collected in the same manner as those from the epinephrine challenge except samples were also taken at 150 and 180 min after infusion.…”

“…In monogastrics, it is well known that the fatty acid (FA) profile of adipocytes reflects the composition of dietary lipids (Eastwood et al 2009;Fickova et al 1998). Altering the FA composition of adipose tissue can affect lipolytic activity and the ability of a sow to mobilize body fat (Tilton et al 1999). Omega-3 (n-3) FA perturb several aspects of lipid metabolism (Chan et al 2003;Harris 1997;Lee et al 2008), which may affect feed intake.…”