Genetic Analysis of Feed Intake in Lactating Sows

Records for daily feed intake during lactation were available for 774 sows with 2,234 litters farrowing from May 2002 to November 2006. Genetic parameters were estimated for whole-oflactation feed intake and feed intake averaged over 5-day periods during lactation. Estimates of heritabilities and the permanent environment of the sow were 0.16±0.05 and 0.18±0.04 for total lactation feed intake and 0.19±0.05 and 0.17±0.05 for average lactation feed intake. Both traits were adjusted for lactation length. Heritability estimates for lactation feed intake defined as separate traits for each of the first 3 parities ranged from 0.17 to 0.28. Genetic correlations between lactation feed intake recorded in different parities were 0.45±0.33 and lower suggesting that lactation feed intake of first parity gilts is genetically a different trait than lactation feed intake of sows recorded in later parities. Heritabilities for feed intake averaged over 5-day periods from day 6 to 20 of lactation were similar to total lactation feed intake. These 5-day period measures of average feed intake were genetically the same trait and had high genetic correlations with total lactation feed intake. The use of a 5-day measure of feed intake during the second or third week of lactation reduces costs of recording and should be explored further by evaluating genetic relationships with other performance traits.