2002 ASAS meeting

Environmental effects on pig performance, meat quality, and muscle characteristics

J. G. Gentry, M. F. Miller, J. R. Blanton, Jr. and J. J. McGlone

Texas Tech University, Lubbock

ABSTRACT: The objective of this experiment was to determine the effect of diverse production systems (that caused increased exercise) on pig performance, muscle characteristics, and their relation to pork quality measures. Birth and rearing conditions were evaluated (n = 48 barrows) and pigs were farrowed either in indoor crates or outdoor huts. At weaning, indoor-born and outdoor-born pigs were randomly allotted to indoor (concrete-slatted flooring, 1.2 m²/pig) or outdoor (alfalfa pasture 212 m²/pig) pens for finishing. Pigs were slaughtered using commercial practices at the Texas Tech University Meat Laboratory. Muscle samples were removed within 1 h postmortem from the longissimus lumborum (LL) and the semimembranosus (SM) and stained histochemically to identify type I, IIA, and IIB/X muscle fiber types. Boneless loins were collected from each carcass, aged for 14 d, and evaluated for color at the 10th rib, sensory panel attributes, and shear force. Pigs born outdoors were heavier and had a greater ADG at d 28, 56, and 112 after weaning (P < 0.05) than pigs born indoors. Pigs reared outdoors had a higher ADG (2.2 vs 1.9 ± 0.11 kg/d, P = 0.01), but also a higher G:F (0.41 vs 0.37 ± 0.04; P = 0.01) than pigs reared indoors. Pigs reared outdoors were fatter (P = 0.01) at the last rib and had loins with a higher (P = 0.02) a* value than pigs reared indoors. No differences were detected in sensory or shear force values and birth by rearing environment interactions were not significant for most measures. Pigs reared outdoors had a higher (P < 0.01) percentage of IIA fibers and a lower (P < 0.05) percentage of IIB/X fibers than pigs reared indoors in both the LL and SM muscles. Cross sectional area (CSA) values of SM from pigs reared outdoors had a smaller CSA for type I (P = 0.003) and IIA (P = 0.02) fibers than SM from pigs reared indoors. Production systems that include increased exercise levels or other features of an outdoor system may alter the size and type of individual muscle fibers which impact pork quality measures such as color.

Keywords: Pigs, Environment, Meat quality