Use of farrowing rate as a measure of fertility of boars
Clark, L.K.; Schinckel, A.P.; Singleton, W.L.; Einstein, M.E.; Teclaw, R.F.
Journal of the American Veterinary Medical Association 194(2): 239-243
1989
ISSN/ISBN: 0003-1488 PMID: 2917890 Document Number: 333397
The first 100 single-boar services of 140 boars were analyzed to determine whether the farrowing rate resulting from initial services predicted the farrowing rate of subsequent services. The data were analyzed for the influence of parity, number of matings per estrus, season of service, and interaction of these variables on farrowing rate. Sow parity influenced farrowing rate. Sows with parity > 8 and gilts had the lowest farrowing rates (P < 0.01). Sows with parity 2 through 5 had the highest farrowing rates (P < 0.01). One and 2 matings/estrus resulted in reduced farrowing rates (P < 0.01), compared with farrowing rates of > 2 matings/estrus. Farrowing rate for services during the summer was lower than that for other seaons of the year (P < 0.01). Evidence of interaction among these variables was not found. Therefore, the results of each service recorded was adjusted to the mean farrowing rate of sows with parity 2 through 5, sows mated .gtoreq. 3 times/service, and sows serviced in the spring. After these adjustments, the farrowing rates for the first 10, 20, 30, 40, and 50 services were analyzed to determine associations with farrowing rates for subsequent services through 100 farrowings. These data also were analyzed to determine whether the associations were strengthened by removal of the first 10 services from the data. The best farrowing rate association indicated that for each 1% increase in farrowing rate subsequent to the first 50 services, the farrowing rate for the second 50 services increased 0.33% (P < 0.01). The maximal R2 value in these regressions was only 11% and was a measure of the proportion of the variability of the later farrowing rates predicted by the variability of the initial farrowing rates. Thus, farrowing rate of initial services of boars (< 50) cannot be used as a reliable estimate of farrowing rate for subsequent services through 100 farrowings and, therefore, cannot be used as a management tool for culling subfertile boars to improve herd reproductive performance.