Liveweight, Protein Deposition and Digestibility Responses in Growing Pigs Exposed to Low Temperature

Two groups of eight individually caged female pigs, averaging 45 kg liveweight, were exposed alternately for 15-day periods to 21 and 6 °C for four consecutive periods. Four pigs in each group were restricted to 100 g of feed per unit of metabolic body weight and four were fed ad libitum. From regressions of liveweight vs. time for the last 10 days of each period, low temperature (6 °C) was found to reduce average daily gain by 2.3% per degree Centigrade below the rate of 792 g/day measured at 21 °C. Also, transitory liveweight changes were measured during the 5 days after each temperature changeover. With each temperature decrease (21 – 6 °C), there was a mean temporary loss in liveweight of 4% and with each temperature increase (6 – 21 °C), this temporary loss of 4% of liveweight was regained, at a constant level of feeding. While exposed to 6 °C, the digestibility of ration dry matter, energy and nitrogen (78.2%, 77.0% and 74.7%, respectively) was significantly lower than when pigs were exposed to 21 °C (80.8%, 79.9% and 79.4%, respectively). As a result of these findings, estimated changes in weight of gutfill were calculated from fecal output records. Regression analysis indicated that changes in gutfill could be responsible for about 55% of the observed temporary liveweight changes. Nitrogen balance data indicated that protein energy retention rates decreased by 1.0% per Celsius unit below the rate of 150 kJ/(day∙kg 0.75 ) measured at 21 °C. The ratio of protein gain to total weight gain was, on average, 25% larger at 6 °C, compared to that measured at 21 °C, indicating leaner growth at low temperature. The effects of feeding level were small compared to the effects of temperature.