The aims were to compare ewe-lamb behaviours between primiparous (PRI) and multiparous (MUL) undernourished grazing ewes at birth and at 3 months of age, and to determine if mothers’ parity affects milk yield and composition, and lambs’ body weight (BW). Food availability restricted the nutritional requirements from day 30 to day 143 of gestation. The PRI ewes had lower BW than MUL during gestation, and their lambs tended to vocalize less times until their first suckle. PRI ewes displayed a lower frequency of acceptance behaviours toward the alien lamb than toward their own lamb, but MUL did not. Whilst PRI ewes emitted a greater number of high-pitched bleats toward the alien lambs than toward their own lamb, MUL did not. PRI ewes produced less milk than the MUL ewes. The heart rate was greater in lambs reared by MUL ewes than by PRI. Although PRI ewes had a lower BW throughout the gestation, this difference was stable and did not affect the establishment of the ewe-lamb bond at birth or at 3 months postpartum. At least under nutritionally restricted conditions during gestation, inexperienced mothers appeared to have a shorter sensitivity period of maternal responsiveness than experienced mothers.