Recent MLC survey data (Pig Year Book, 1995) reports that approximately 0.5 of annual first parity gilt cullings are due to reproductive failure. This high culling rate may be attributed to recent genetic selection for increased lean tissue accretion rates, and as a result a greater mature body weight. However, the gilt attains puberty and is thus mated at a lower age and as a consequence has not reached the target threshold of 35kg body protein mass at farrowing, suggested by Everts (1994),to be necessary for optimal reproductive performance. This, confounded with excessive tissue catabolism over lactation results in the attenuation of the gilt's potential protein accretion curve and hence reproductive failure (Foxcroft et al. 1995). The aim of this experiment was to study the effect of two protein accretion rates (maximum and 0.8 of maximum) on reproductive function in the gilt from 50kg liveweight to 3rd oestrus.