Fertility in females of standard nutria (Myocastor coapus) in farm herds

The reproduction potential was studied in young (primiparous) and adult females of standard nutria (Myocastor coypus) in farm herds. Fertility in primiparous females were studied in 12 private farms in western part of Slovak Republic during the years 1995 - 1998. Fertility in adult females in dependence on parity (first to fifth litter) was studied in private herd in a set of 68 adult females within three families. The selected herds were kept traditionally in housing with runs in outdoor climatic conditions. The composition of diet was conditioned by the season - summer diet consisted of green feeds with concentrate supplementation, the winter diet consisted of root crops, hay and concentrate supplement. Family breeding was used in the breeding work, polygamy represented 1 : 6-8. The results were processed mathematically and statistically: - basic variation-statistical characteristics were calculated for individual factors (herds, years), - average fertility was calculated by means of two-way variance analyses crosswise with one observation in subclass with determination of non-additivity of herd and years after the model equation yij = m + hi + rj + (hr)ij + eij, with m- average of the whole population, hi - fixed effect of i-th herd, rj - fixed effect of j-th herd, (hr)ij - non-additivity of herds x years, eij - random errors of experiment - in the case of significance of individual effects found with two-way variance analysis were the arithmetical means tested by Tukey's t-test of multivariate comparison. The average fertility in primiparous females varied from 3.80 to 5.27 youngs, and according to years from 4.41 to 4.87 youngs per litter. The highest number of youngs in the litter of primiparous females were seven youngs. Out of the total number of bearing females most of them (40.8%) had five youngs in a litter and the least of them (0.3%) had two youngs. The highest number of parturition was noticed in April (15.4 %) and in September (15.2%), and the lowest natality was in January (2.9%) and July (4.1%). The average fertility of females in dependence on parity within the studied families varied from 4.0 to 6.3 youngs. The highest natality corresponded to the fertility of live youngs in second litter (64.3%), and with six youngs in the fourth litter (53.8%). The maximum number of youngs were seven animals in a litter, namely in third and fifth litter only. In the fourth litter up to 30.8% bearing females had the same fertility, it means seven youngs in a litter. The average fertility in females was the lowest in the first litter 4.53 youngs. The average fertility rose in next litters to 5.20, 5.70 and it reached the maximum values in the fourth litter with 6.17 youngs. It decreased to 5.20 youngs in the fifth litter. We found statistically highly significant effect of parity in family on average fertility in adult nutrias and highly significant non-additivity of families and litter