Effect of Fasting and Refeeding on Body Weight, Rectal Temperature, Blood Volume and Various Blood Constituents in Growing Swine

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Abstract
Growing pigs (30-kg) were used to study the effect of fasting and refeeding on body weight, rectal temperature, blood volume and various blood constituents. Nine fasted and 9 control pigs were used for a 167-hour fast and a 216-hour refeeding period. Hematocrit, hemoglobin and serum cholesterol values were significantly greater in fasted pigs after 27 hours. Blood glucose and serum calcium, sodium, urea N, ammonia N, and nonprotein N levels were significantly lower in fasted pigs as compared with control pigs. Fasted pigs had first significantly lower and then significantly higher serum total N and protein levels than control pigs. Blood volume as a percentage of body weight was 53% greater in fasted pigs as compared with control pigs (9.96 and 6.51%, respectively). No significant difference of plasma and total blood volume was observed between control and fasted pigs as determined by the T-1824 dye method. Rectal temperature was significantly decreased when pigs were fasted 27 or more hours. With the exception of hemoglobin, no differences were noted between the fasted and the control pigs at 216 hours after refeeding. Hematocrit and serum total N and protein values from control pigs decreased significantly which suggests that repeated blood sampling may have an effect on these criteria.