Addition of fat to the diets of lactating sows

Abstract

Four experiments were conducted to evaluate the effects of dietary fat on energy metabolism in the lactating sow, and carcass composition of pigs at weaning. Sows had ad libitum access to a 1% lysine corn-soybean meal diet during lactation. Diets contained either 0% (Control, C) or 10% tallow (T) in all experiments except Exp. 2, which used only the C diet. Experiment 1 used two groups of 18 sows to evaluate the effects of dietary fat on milk production, milk composition, and hormone-sensitive lipase (HSL) activity. Experiment 2 used 6 sows in a repeated 6 x 6 Latin square experiment to determine the optimal dosage of epinephrine for use in an epinephrine challenge. Experiment 3 used 17 sows to evaluate the effect of diet on HSL activity, and energy mobilization in response to epinephrine. Experiment 4 (Manuscript 1, Experiment 2) used 30 sows to determine the effect of T on body composition of pigs at weaning, and HSL activity on d 21 of lactation. No differences were observed in sow ADFI (P $>$.10) in Exp. 1, 3, and 4. Daily ME intake was increased (P $<$.05) in Exp. 4 for sows consuming the T diet, but did not differ in Exp. 1 and 3 (P $>$.10). Litter weaning weight was increased for T sows in Exp. 4 (P $<$.05), but did not differ in Exp. 1 and 3 (P $>$.10). Dietary differences in milk yield were not detected in Exp. 1 (P $>$.10). However, the percentage solids, fat and ash were increased in milk of T fed sows (P $<$.05). This increase in milk fat percentage altered carcass composition of pigs at weaning in Exp. 4. Carcasses of pigs from sows fed T were higher in DM and fat (P $<$.05), and lower in percentages water and protein (P $<$.05) than pigs from C sows. The 1.6 $\mu$g/kg BW dosage of epinephrine (dose determined in Exp. 2) was used in the epinephrine challenges in Exp. 3. No diet effects were observed for peak concentrations of NEFA, glycerol or glucose (P $>$.10) after epinephrine infusion. Hormone sensitive lipase activity increased in T sows on d 28 of lactation(Exp. 1; P $<$.06). However, no difference was observed in HSL activity on d 21 of lactation (P $>$.10) in Exp. 3 or 4. Diets containing 10% tallow do not alter the rate of lipolysis in adipose tissue of the sow during lactation. Milk from sows fed T is higher in fat than milk from C sows, resulting in an increase in body fat percentage of pigs nursing T fed sows. It is unclear how the changes in carcass composition affect future performance of these pigs. Further research is also necessary to better understand the effects of diet and stage of lactation on sow adipose tissue metabolism.