Evaluating the impact of weaning weight and growth rate during the first week post weaning on overall nursery performance

Objective: Determine the effects of nursery pig weaning weight (WW) and first week postweaning growth rate (ADG7) on average daily gain (ADG), final weight, removals, and mortality under field conditions. Materials and methods: In this 42-day study, 1602 pigs (mean [SD] weight: 5.42 [0.9] kg) were weaned at 19 to 21 days of age. Four successive batches of weaned pigs were moved into the same nursery room. Within each batch, pigs were allotted by WW to have approximately one-third of each class (LightWW, MediumWW, and HeavyWW) in all pens. On day 7, pigs were individually weighed and designated according to their ADG7 into four classes within their batch: NegativeADG7, LowADG7, MediumADG7, and HighADG7. An equation was developed and validated to quantify the association between WW and ADG7 with ADG. Results: Weaning weight had no effect on ADG7 (P = .42), but increasing WW and ADG7 increased (P < .001) ADG and final weight at 42 days. Pig removal was reduced if pigs had heavy WW or gained weight in the first week after weaning (≤ 3.2%) compared to pigs that lost weight during the first week in the LightWW (20.9%) or MediumWW (10.3%) categories. Overall mortality was 1.1% with no effects of WW, ADG7, or its interaction (P > .54). The equation generated indicated that WW and ADG7 together had moderate accuracy (R² = 0.54; P < .001) to predict ADG. Implication: The WW and ADG7 are not correlated, but they affect and partially predict the overall nursery performance.