POSSIBLE RELATIONSHIPS OF SOME PARAMETERS OF REPRODUCTIVE SUCCESS IN SOWS TO SERUM CONCENTRATIONS OF THYROID-HORMONES, INSULIN, IGF-1, CORTISOL AND PROGESTERONE

In order to explore the possibility of predicting reproductive perform ance in sows and eventually altering the outcome, preprandial serum ho rmone concentrations and insulin-like growth factor-I (IGF-I) were det ermined in twenty crossbred females at mid and late gestation, several days after parturition and I day after weaning the litter. Mean triio dothyronine (T3) declined slightly from 1.31 to 1.12 nmol/l, while thy roxine (T4) decreased markedly during pregnancy from 55.2 to 34.8 nmol /l followed by recovery to 43.2 nmol/l. Basal insulin increased gradua lly but significantly from 3.0 to 6.9 mlU/l, while cortisol showed an increase during pregnancy (66 to 167 nmol/l) followed by a drop (110 n mol/l) and a second surge (148 nmol/l). Progesterone declined during p regnancy (41 to 26 nmol/l) and then dropped markedly post partum (1.1 nmol/l) in all except one sow. IGF-I increased more than four-fold aft er parturition (48 to 228 mu g/l) and then decreased (132 mu g/l). The data obtained were analysed statistically in relation to measures of reproductive success such as lifter size and weight, as well as change s in maternal body weight. It was found that midpregnancy preprandial insulin concentrations were correlated significantly with the subseque nt numbers of farrowed (r=0.530) and liveborn (r=-0.667) piglets. More over, one third of the variance (R(2)=0.33) in weight of liveborn pigl ets was predicted by basal insulin negatively (P=0.025) and progestero ne positively (P=0.044) obtained at midgestation. A multiregression in cluding T4 (P=0.027), cortisol (P=0.05) and progresterone (P=0.1) leve ls determined in late gestation described 45% of the variance associat ed with a measure of overall performance by the sows (net body weight gain+litter weight at weaning). Such an approach may help to elucidate the influence of changes in nutrition and management practice which a ffect reproductive success through changes in metabolic hormone concen trations.