178
Physiological characteristics of lactating sows with high milk production
The objective of this study was to investigate if physiological characteristics of lactating sows could be used as indicators of high litter growth. The data for the current evaluation was obtained from a nutritional study of the effects of increasing dietary valine-to-lysine ratio on the performance of litters and sows during lactation. There were no effects (P=0.30) of the dietary treatments; therefore the data were pooled for this evaluation. In total data from 565 sows where litters had been standardized to 14 piglets at d 2 postpartum were used. Piglets were weaned at d 26. Sow BW and backfat thickness (BF) and litter weight were registered for all sows at d 2 and at weaning. On a subsample of 72 sows blood samples were taken and litter weight measured weekly. Additionally a milk sample was obtained and sows BW and BF registered at d 17. Blood samples were analyzed for glucose, lactate, NEFA, creatinine and urea nitrogen (Advia 1800 Chemistry System, Siemens). The sow milk samples were analyzed for DM, lactose, fat and protein using a MilkoScan FT2 (Foss Electric, Denmark). Pearson’s correlations were calculated to test for correlations between the measured variables. Total feed intake of sows were negatively correlated with BW (r=-0.23, P<0.001) and BF (r=-0.24, P<0.001) loss. The ADG of the litter was positively correlated with BW (r=0.46, P<0.001), BF (r=0.50, P<0.001) loss and total feed intake (r=0.20, P<0.05) during lactation. Loss of BW from d 2 to d 17 was associated with decreased plasma urea nitrogen concentrations (r=-0.29, P<0.05) at d 2, increased plasma creatinine concentrations at d 2 (r=0.25, P<0.05) and d 10 (r=0.39, P<0.05) and NEFA (r=0.37, P<0.05) concentrations at d 10. The BW loss from d 17 to d 26 was positively correlated with plasma NEFA (r=0.27, P<0.05) concentrations at d 26. Mobilization of BF in early lactation was negatively correlated with milk protein content (r=-0.33, P<0.05), but in late lactation it was positively correlated with milk fat content (r=0.36, P<0.05). Sows with high BF loss in late lactation had lower plasma lactate (r=-30, P<0.05) and greater plasma creatinine (r=0.30, P<0.05) concentrations. In conclusion, sows with a high ADG of the litter was characterized by greater loss of BW and BF and this was associated with higher plasma concentrations of NEFA and creatinine as measures of fat and protein mobilization, respectively.
Keywords: Sow metabolism, lactation, litter growth