Factor Analysis of Growing Pigs’ Responses to High Cyclic and Constant Temperatures

A multivariate factor analysis was used to explore associations among five measured energetic responses for growing pigs as an improved analysis method to an analysis of predictions from an energetic mathematical model. The response variables were feed consumption, water vapor production, heat production, water consumption, and respiratory quotient. In one treatment, groups of four 36 kg pigs were housed in a calorimeter at temperatures cycling between a minimum of 26°C to a maximum of 40°C. In another treatment, groups of four 36 kg pigs were housed in a calorimeter at a constant temperature of 33°C. Three factors were extracted from the energetic data in each of the environmental treatments. These common factors described homeothermy, energy intake, energy retained and more clearly reflected the differences between the environments than any of the individual variables. Homeothermy was described by heat and water vapor production in the constant temperature treatment; while it was predominately described by water vapor production and water consumption in the cyclic temperature treatment. This factor represents heat loss as both sensible and latent heat in the constant temperature treatment but, primarily as latent heat in the cyclic temperature treatment. Cyclic temperatures caused higher than average homeothermy scores during the time of low energy retention and low energy intake scores (during peak temperatures), whereas constant temperatures caused high homeothermy scores during the time of high energy retention and high energy intake scores.