Polyphasic growth-weight response in the guinea pig

An assessment of the growth rate pattern based on longitudinal weight data of guinea pigs was conducted over the presumptive preweaning and early postweaning period. The study covered the minimum of 44 and maximum of 53 days with means calculated for 3-day intervals involving 13 litters and a total of 40 young. Initial analysis showed males heavier than females at birth and both sexes being inversely proportional to litter size at birth. At the end of the experimental period the males were still heavier than the females but their weight distribution peaked in litter of three while the females were heaviest in the largest litters of five and lightest in the litter of one. Phasic linear regression line analysis revealed 4 litters with a triphasic growth outline and 6 litters with quadrophasic growth outline. Final assessments indicate that the total period of 53 days manifests a quadrophasic growth outline while, in contrast, the period specifically involved with the process of lactation and weaning displays a definite diphasic growth spectrum and is comparable to the tri- or quadrophasic spectrum occurring in the albino rats, rice rats and hamsters.