Growth, Carcass, and Meat Quality in Lines Divergently Selected for Testosterone Production and their Crossbred Progeny.

Abstract

The objective of this study was to characterize growth, carcass composition, and meat quality in two Duroc lines of pigs divergently selected 10 generations for testosterone production and then maintained by random within line selection. In generation 21 endogenous testosterone production in the high (HTL) and low (LTL) testosterone lines averaged 49.0 ng/ml and 27.8 ng/ml (P < 0.01), respectively. Eight LTL and 10 HTL boars were used to create 29 LTL and 33 HTL litters. These same boars were mated to a line of white composite (WC) females to generate 11 WC by LTL litters (WLT) and 23 WC by HTL litters (WHT). Barrows and gilts were then selected LTL (n = 53), HTL (n = 61), WLT (n = 102), and WHT (n = 101) for testing. Pigs were weighed and scanned using real-time ultrasound 48 h prior to one of two slaughter dates. Data were analyzed with a mixed model including fixed effects of line, mating type, sex, and random effect of sire nested within line. All possible interactions among fixed effects were tested. Growth and carcass traits analyzed included days to 114 kg (D114), average daily gain (ADG), back fat adjusted to 114 kg (BF), loin muscle area adjusted to 114 kg (LMA), and predicted percent lean (PPL). Fat-O-Meater data collected included hot carcass weight (HCW), adjusted fat depth (FDEPTH), adjusted loin depth (LDEPTH) and percent lean (%LEAN). Meat quality traits characterized included marbling score at 24 h post-mortem (MAR), percent lipid (%LIPID), pH, water-holding capacity (DRIP), color score (CS) and Minolta L*, a*, and b*. The HTL had fewer D114 (P < 0.05), greater ADG (P < 0.01), greater BF (P < 0.01) and lower PPL (P < 0.01) than LTL. For crossbred progeny, WHT and WLT did not differ for D114, ADG, or BF. The WLT had larger LEA (P < 0.05) and higher PPL (P < 0.01) than WHT. The WLT had lower LDEPTH (P < 0.05) than LTL and HTL. The LTL and HTL had higher subjective scores for MAR (P < 0.05). Least square means for %LIPID for HTL and LTL were 4.00 and 3.95, respectively. The WHT had higher means for DRIP (P < 0.01), L*, a* and b* (P < 0.05) than WLT, but did not differ for pH or CS measurements. Pigs selected for increased testosterone production grew faster and produced fatter carcasses than pigs selected for decreased testosterone. Because of their high intramuscular fat content and acceptable meat quality, these lines may be useful in developing premium products.