Feeding pigs specific diets based on potential growth rate as determined by growth rate in the nursery may decrease variability in grow-out and finishing. In our study, however, pigs separated into slow, average or fast potential growth rates by determining growth rate in the nursery had comparable growth rates, feed intake and rates of protein and lipid deposition in late finishing.
Pigs were identified as having either a slow, average or fast protein growth rate (PGR) based on their body weight (BW) per day of age from birth to nursery exit. Previous studies conducted at the Prairie Swine Centre have demonstrated a correlation (r2 ~ 0.35) between BW at nursery exit and growth rate in the grow-finish barn. Interestingly, in this study performance, expressed in terms of ADG, ADFI and FCE was unaffected by PGR . Pigs receiving the high energy diet had reduced ADFIs (P < 0.05); however ADG was similar across treatments.
The efficiencies with which pigs used dietary energy for BW gain and for accretion of protein and lipid in the carcass were unaffected by PGR. Pigs fed the low energy diet were more efficient (g protein deposited/ g Mcal intake) in their accretion of carcass protein than pigs fed the high energy diet (P < 0.05). Although pigs fed at 100% of ad libitum grew faster and took fewer days to reach 120kg than those fed at 85% of ad libitum, the latter were more efficient in their use of dietary energy for BW gain (P < 0.05) and for carcass protein accretion (0.50 < P < 0.10).
Growth performance and the efficiency of energy utilization for growth and for carcass nutrient accretion in finishing (90 to 120kg) pigs was similar among pigs identified at nursery exit as having a slow, average or fast potential growth rate. This suggests that segregating pigs at nursery exit based on PGR is not an effective tool to manage variability in the grow-finish herd.