Vaccination against follistatin affects reproductive potential in cycling gilts

Primiparous sows (gilts) were actively vaccinated against follistatin in an attempt to modify litter size. Forty-seven gilts were vaccinated four time s against a recombinant porcine follistatin (FS) or a sham vaccine (CTL) an d were allowed to mature naturally prior to breeding. At breeding, FS antib ody titers ranged from 0 to 1:6400 in the FS vaccinated gilts, and were not detectable in the CTL gilts. Overall, follistatin vaccination did not affe ct the total number of pigs born live (FS = 10.9 +/- 0.5, CTL = 10.3 +/- 0. 4), stillborn (FS = 0.4 +/- 0.1, CTL = 0.4 +/- 0.2) or mummified (FS = 0.1 +/- 0.1, CTL = 0.3 +/- 0.1). However, separation of the FS vaccinated gilts into low (less than or equal to 1:400, n = 16) and high (>1:400, n = 7) ti ter groups revealed significant differences in piglets born alive (FS high titer = 12.9 +/- 0.9, FS low titer = 10.0 +/- 0.5: P = 0.01) and total numb er of piglets born (FS high titer = 13.0 +/- 0.8, FS low titer = 10.8 +/- 0 .6: P = 0.08). This study shows that vaccination of gilts against follistat in increased litter size in those gilts which achieved a high antibody tite r to follistatin.