Growth and Carcass Responses in the NE Index Line Estimated in Pure-line and Crossbred Litters
2002 University of Nebraska-Lincoln Extension Swine Report. The objective was to estimate responses in growth and carcass traits in the NE Index line (I) that was selected 19 generations for increased litter size. Responses in pure-line, F1 and 3-way cross litters were compared. In Exp 1, 694 gilts that were retained for breeding, including 448 I and control (C) and 246 F1 I and C by DanbredTM Landrace (L), were evaluated. Direct genetic effects of I and C did not differ for backfat or days to 230 lb; however, I had 0.24 in2 smaller longissimus muscle area (LMA) than C (P < 0.05). F1 gilts had -0.13 in less backfat, 0.67 in2 greater LMA and 31 d less to 230 lb than pure-line gilts (P < 0.05). Exp 2 used individuallypenned barrows and gilts including 43 I and C, 77 F1 produced from pure-line females mated to (L) or Danbred USA DH boars (T), and 76 3-way crosses produced from F1 females mated to T boars. Direct genetic effects of I did not differ from C for average daily feed intake (ADFI), average daily gain (ADG), feed conversion (FC), days to 250 lb, backfat (BF), LMA, ultimate pH of the longissimus, longissimus Minolta l* score, and % lean estimated by TOBEC. Responses (I minus C) in growth and carcass merit did not differ when measured in pure-line and crossbred pigs. Interactions between responses in F1 and pure lines were not significant except for pH. F1 and 3-way cross pigs averaged 0.51 lb/d greater ADFI, -0.53 less feed/gain and 0.44 lb/d more ADG than pure-line pigs (P < 0.01). F1 and 3-way crosses had -0.35 in less BF, 0.89 in2 greater LMA, 6.2 % greater lean, and 5.3 higher Minolta l* score than pure lines (P < 0.05). No correlated responses to selection for increased litter size in overall growth or carcass traits occurred. Mating Line I to leaner, faster growing sires will increase ADFI, ADG, LMA, and percentage lean , decrease feed/gain ratio, decrease backfat, and lighten meat color.