The measurement of milk intake in the neonatal guinea pig

Study of the effects of enteral nutrition on neonatal growth and development has been hindered by lack of a suitable model. An isotope dilution method for the measurement of milk intake in suckling rodents was evaluated in 13 hand-fed neonatal guinea pigs, by comparing milk intakes determined using 3H20 with intakes determined by difference in weight before and after feeding. The effects of two experimental durations (1 or 2-3 days) on the accuracy and precision of the method was assessed. Weighted milk intakes were 18 -26 g/day, and body weight changes were -7% - +12% of initial weight. There was no significant difference between milk intakes determined using the two methods for both 1 and 2-3 day comparisons. However, the coefficients of variation for 1 and 2-3 day measurements were 24.4% and 5.5%, respectively. These values are equivalent to precisions of approximately 10% and 2% for estimates of total milk output in a rodent suckling 8 pups. It is concluded that the 3H20 method is no less accurate or precise than the weighing method for 2-3 day measurements of milk intake in individual pups and milk production of dams. These findings strengthen the use of the precocial guinea pig as a model for the study of the effects of early feeding on growth, development and aging.