Environmental enrichment influences on pig behavior, performance and meat quality

The influence of environmental enrichment and genotype were evaluated for effects on performance, behavior and carcass characteristics in 320 pigs from weaning to slaughter at over 110 kg. Ten treatments were evaluated including two genotypes and five levels of enrichment, arranged factorially. Genotypes were PIC C-15 x 405 cross (C-15) which is a commonly employed commercial hybrid in the US swine industry and PIC EXP-94 x 405 cross (EXP-94; one-eighth Meishan). The herd was positive for Porcine Respiratory and Reproductive Syndrome virus which contributed to a high rate of mortality (6-40% death rate within treatments). The five environmental treatments were isolation (NEG), weekly normal handling (NOR), daily normal handling plus the addition of environmental enrichment devices (TOYS), daily normal handling plus 2-min pleasant handling bouts with humans 5 days/week (HUM), and the same as HUM plus TOYS (T + H). Averaged over genotypes, growth and efficiency measures were not effected by the range of environmental treatments performed. Enrichment treatments and genotypes tended to interact (P = 0.07) for average daily gain and Feed:Gain ratio. C-15 pigs showed similar ADG and F:G ratio in the five enrichment treatments. However, EXP-94 pigs exposed to the TOYS had improved ADG and F:G ratio (P < 0.05) compared to the HUM, T + H and NEG treatments. Pigs in the NEG had less backfat opposite the last rib and last lumbar vertebrae (P < 0.05) than pigs in other levels of enrichment. Pork quality measures (pH, Minolta colorimeter, Warner-Bratzler shear force value and taste panel evaluation) were not affected by the range of rearing conditions studied during this experiment. The environmental treatments had no significant effect on the overall duration of the behaviors observed during a 24-h period in finishing (50 to 113 kg body weight), although both treatment and genotype had an effect on behavior patterns in the nursery (weaning at 28 days to 8 weeks of age) stage of production. Animals in NEG took longer to make contact and spent less time in contact with the experimenter during two human-interaction testing periods (P < 0.001). Enrichment treatments did not affect the ability or time required to move or weigh these pigs. Considering a common genotype used in the US swine industry (C-15), we found no improvement in pig performance, ease of handling or meat quality with use of increased environmental enrichment or extensive human handling. Other genotypes may show a positive performance response to environmental enrichment.