The energetics of physical activity in growing-finishing swine
Abstract
Dynamic response of an indirect calorimeter to a change in input gas concentration was modeled as a linear, first order, constant coefficient system. The model was experimentally verified as being an accurate description of the response of the calorimeter to a step change in input CO$\sb2$ concentration. It was assumed that the model was appropriate for any other time varying input concentration. The model was used to recover the true activity related heat production response of swine from measurements made from indirect calorimetry. Results of applying the input recovery techniques to the heat production of growing swine showed that the treated data exhibited a clear relationship between activity and its associated increase in heat production. The relationship was consistent in exhibiting a rapid increase just after initiation of activity, then reaching a fairly stable value while the activity occurred, and finally decreasing again after activity ceased. Resting heat production was generally uniform, but specific actions, such as stretching motions while lying down, were detectable. Resting heat production was also found to vary diurnally, reaching a maximum around 7:00 PM in the evening. Average resting heat production also increased by 18% as the animal's weight increased by 89%. Increases in heat production due to activity were found to be dependent on the type of activity observed. Short duration standing (less than four minutes) produced the highest increase (110% above resting), although part of the response could have been due to residual effects of the filtering of the data. Standing greater than four minutes produced increases of 90% while sitting increased heat production by an average of 63% above the resting level. The increase was also found to vary due to the age of the pigs, but this variation was small and not consistent over time. It was concluded that age or size played relatively little role in determining the increase in heat production associated with activity. Measured heat production associated with activity was compared to simulated versions modeled as a rectangular pulse increase of the same duration as the activity. This model was concluded to be an adequate representation of the increase in heat production associated with activity.
Degree
Ph.D.
Advisors
Jones, Purdue University.
Subject Area
Agricultural engineering
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