INTERACTIONS BETWEEN NUTRITION AND REPRODUCTION IN THE PIG

Nutrition impacts upon reproduction in all species. This is particular ly so in mammals, due to the female's commitment to the metabolically expensive requirements of a prolonged gestation and lactation. Interac tions between nutrition and reproduction in the pig are discussed in l ight of current and recent studies using two distinct scientific model s. The seven day ''feed-restricted prepubertal model'' has enabled inv estigation of metabolic modulation of the entire hypothalamo-hypophysi al-gonadal axis without alterations in gross body weight and compositi on. Modulation of gonadotrophin secretion (''central effects'') and ov arian sensitivity by ''indicators'' of metabolic state e.g. plasma and follicular glucose, insulin and IGF-1 concentrations are discussed, i ncluding potential interactions between feeding patterns and circulati ng steroid concentrations. Hypotheses arising from these studies have recently been further developed utilising a ''feed-restricted sow mode l''. Data from this paradigm are also presented and suggest that short -term interruption of nutrient availability to the primiparous sow thr oughout lactation may substantially impact upon subsequent embryo surv ival and fecundity. In both the prepubertal and breeding female pig, n utrition modulates reproductive status via a complex array of ''cues'' acting along the hypothalamo-hypophysial-ovarian axis.