Comparison of plasma FSH concentration in boars and gilts from lines selected for ovulation rate and embryonal survival, and litter size and estimation of (co)variance components for FSH and ovulation rate

The objective of this research was to determine whether plasma concentratio n of FSH was genetically correlated with ovulation rate and thus was a usef ul trait for indirect selection. Blood samples were collected from 619 anim als from five lines of pigs. Line I was selected for increased index of ovu lation rate and embryonal survival, and Line C was its randomly selected co ntrol. Pigs sampled from Lines I and C were from generations 12 and 13. Pig s from three additional lines that mere derived from eighth-generation pigs of Lines I and C also were used. These lines were Line C2, a randomly sele cted control derived from Line C, Line COL, derived from Line C, and Line I OL, derived from Line I; each of these Lines was selected an additional fiv e generations for increased ovulation rate and increased litter size. A sin gle blood sample was collected from each pig between 46 to 63 (d 58), 86 to 98 (d 90), 110 to 133 (d 124), and 147 to 153 (d 150) d of age. The herita bility of ovulation rate was .28 and heritabilities of plasma concentration of FSK at d 58, 90, 124, and 150 were .41, .25, .12, and 0, respectively. Genetic correlations between ovulation rate and d-58, d-90, and d-124 plasm a concentration of FSH were .31, .23, and 0, respectively. Line I gilts had greater estimated breeding values for plasma concentration of FSH at d 58 and 90 than Line C gilts (P < .01). Line COL gilts had greater estimated br eeding values for plasma concentration of FSH at d 58 than Line C2 gilts (P < .01). Line I boars had greater estimated breeding values for plasma conc entration of FSH at d 90 than Line C boars (P < .05). Even though genetic c orrelations were low, selection for increased plasma concentration of FSH w as estimated to be 93% as effective in changing ovulation rate as direct se lection because selection for FSH can be practiced in bath sexes. Thus, sel ection for increased plasma concentration of FSH seems to be a practical me thod for increasing ovulation rate in pig breeding programs without using l aparoscopy.