342 EFFECT OF INCREASED SUCKLING STIMULATION ON PIGLET WEIGHT GAIN AND DAILY MILK YIELD OF SOWS TRANSGENIC FOR BOVINE α-LACTALBUMIN

Abstract

The objective of the present study was to determine the effects of over-expression of a mammary-specific transgene, bovine α-lactalbumin, and increased suckling stimulation on milk yield in sows and resultant piglet weight gain. Lactational response to increased suckling stimulation was determined by fostering piglets of either the same age (D1) or seven days older (D7) than sow day of lactation to Yorkshire sows either non-transgenic (C) or transgenic for bovine α-lactalbumin (bALA). Twenty first-parity Yorkshire sows were allocated between four treatments dependent on the combination of sow genotype and age of litter fostered (bALA-D1, bALA-D7, C-D1, C-D7). Litters were standardized to 10 piglets each and fostered to subject sows at approximately 36 hours postpartum. All D1 and D7 litters were not significantly different in mean piglet weight within age groups. Sow milk yield (kg) was determined by the weigh-suckle-weigh method on Days 6, 9, 12, 15, and 18 postpartum. Piglet weight gain (g) was determined by calculating the difference between individual piglet weights on Days 3 and 18 of sow lactation. Least-squares means and standard errors for overall daily milk yield of bALA sows with D1 and D7 foster piglets were 7.1 ± 0.4 and 9.1 ± 0.4 kg, respectively, reflecting a significantly greater milk yield (28% increase, P < 0.05) in response to increased suckling stimulation. Least-squares means and standard errors for overall daily milk yield of control sows with D1 and D7 foster piglets were 6.7 ± 0.4 and 7.0 ± 0.4 kg, respectively, reflecting a non-significant change in milk yield (4% increase, P > 0.05) in response to increased suckling stimulation. The bALA-D7 treatment resulted in a 31% increase in mean daily milk yield as compared to the combined mean daily milk yield of the three remaining treatments. Cumulative weight gain of piglets suckling bALA sows resulted in least-squares means and standard errors of 3411 ± 156 g for D1 and 3458 ± 202 g for D7, and piglets suckling control sows had cumulative weight gains of 2944 ± 143 g for D1 and 3016 ± 175 g for D7. Overall effect of treatment in the model was significant (P < 0.05) through Day 12 of sow lactation. Piglets that suckled bALA sows, regardless of age of litter when fostered, grew significantly faster than piglets that suckled control sows for the entire 15 days of lactation studied (P < 0.05), resulting in a cumulative average of 455 grams of additional gain per piglet. First-parity bALA sows were more able to respond to increased suckling stimulation by a resultant increase in milk yield than control sows under equivalent conditions. Similarly, piglets suckling bALA sows gained weight faster than piglets suckling control sows. Over-expression of the bovine α-lactalbumin transgene in sows enhances mammary response to regulators of milk yield, such as level of suckling stimulation. (Supported by the Illinois Council for Food and Agricultural Research Sentinel Grant).