Meta-analysis of the effects of high ambient temperature on growth performance of growing-finishing pigs

Abstract

High ambient temperature (T) is oneof the most important climatic factors influencing pigperformance. Increased T occurs sporadically duringsummer heat waves in temperate climates and yearround in tropical climates. Results of published experimentsassessing the effects of high T on pig performanceare surprisingly variable. Thus, a meta-analysiswas performed to aggregate our knowledge and attemptto explain differences in the results across studies onthe effect of increased T on ADFI and ADG in growingfinishingpigs. Data for ADFI and ADG were extractedfrom 86 and 80 trials, respectively, from articles publishedin scientific journals indexed in PubMed, ScienceDirect, and from proceedings of scientific meetingsthrough November 2009. Data on ADFI and ADG wereanalyzed using a linear mixed model that included thelinear and the quadratic effects of T and BW, and theirinteractions as continuous, fixed effects variables, andthe trial as a random effect factor (i.e., block). In addition,the effects of housing type (2 levels: individualand group housing) and the year of publication (3 levels:1970 to 1989, 1990 to 1999, and 2000 to 2009) onthe intercept and the linear regression term for T (i.e.,the slope) were also tested. Results showed that highT had a curvilinear effect on ADFI and ADG and thatthis effect was more pronounced in heavier pigs. AcrossT, ADFI was less when pigs were group-housed. Theintercept and the regression coefficient (slope) for Twere significantly affected by the year of publication.The effect of increased T was greater in more contemporaryworks, suggesting that modern genotypes couldbe more sensitive to heat stress than older genotypes oflesser growth potential. In conclusion, pig performancedecreases at an accelerating rate as T is increased. Thelarge between-study variability on the effects of high Ton pig performance is partially explained by differencesin pig BW and to a lesser extent by the year the studywas published. © 2011 American Society of Animal Science. All rights reserved.