Impact of Birth and Body Weight at Twenty Days on thePostweaning Growth of Pigs with Different Weaning Management

Pigs from 112 litters were assigned to 3 different treatments and their BW growth to 125 kg was determined. The 3 treatments were as follows: sow-reared, weaning at 14 d of age, and weaning at 2 d of age. Piglets from litters weaned at 14 d of age were fed a milk replacer after weaning until the day the sowreared litters were weaned. Piglets from litters weaned 2 d after birth were fed the milk replacer for 19 d after weaning. Pigs were individually weighed at birth at about 20 d of age, at 32 kg BW, and every 2 wk thereafter. The grow-finish BW data were fitted to a generalized Michaelis-Menten equation. The relationships of 20-d BW to birth BW were different for each treatment. Postweaning BW and days to attain 125 kg had nonlinear relationships with birth and 20-d BW. A 0.1 kg increase in birth BW reduced predicted days to reach 125 kg BW by 3.48, 0.92, and 0.18 d at 1.0, 1.5, and 2.0 kg birth BW, respectively. A 0.1 kg increase in 20-d BW decreased predicted days to reach 125 kg by 0.57, 0.38, and 0.26 d at 5.0, 6.5, and 8.0 kg 20-d BW, respectively. Increasing the BW of the lightest birth BW and 20-d BW pigs had a greater impact on subsequent BW than increasing the BW of pigs with average to above average birth and 20-d BW.