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It is well accepted that there is an optimal dietary protein-to-energy ratio for young pigs. However, there is not a final recommendation and doubts may arise about how to reach this ratio through changes on the dietary levels. The aim of the present study was to determine how a difference in the dietary protein or energy content and their corresponding protein-to-energy ratio affect growth performance in post-weaned piglets. A total of 480 weanling piglets (28d-old, initial BW 7.17 ± 0.01 kg) were distributed according to their BW into 48 pens (10 pigs/pen), and were randomly allotted to 1 of 4 experimental diets formulated to have different protein-to-energy ratios: a high protein (HP, 204 g CP/kg as-fed) and a low protein diet (LP, 142 g CP/kg) with similar DE content (3.60 Mcal/kg), and a low energy (LE, 3.35 Mcal DE/kg) and high energy diet (HE, 3.90 Mcal DE/kg) with similar CP content (190 g/kg). The protein-to-energy ratios were 56.6 and 56.7 g CP/Mcal DE for HP and LE, and 39.4 and 48.7 g CP/Mcal DE for LP and HE. Performance was measured on d 8 and 18 post-weaning.
Up to d 8, HP diet promoted a higher ADFI than LP and HE diets (P < 0.05), and a higher ADG and BW than LP, HE and LE diets (P < 0.01). Feed:gain ratio also was more efficient for HP piglets in this period. On d 18, LE diet promoted the highest ADFI and ADG during period 8–18d (P < 0.001). Piglets fed the LE diet had a statistical approach to the highest piglet BW in comparison with piglets fed the HP diet (11.89 vs. 11.42 kg; P = 0.09), however, both treatments were higher than piglets fed the HE diet (10.84 ± 0.13 kg) and piglets fed the LP diet (9.16 ± 0.13 kg), that were the lightest (P < 0.05). Feed:gain ratio of latter piglets was higher than the rest of the experimental diets for this period. Growth results are in accordance with dietary protein-to-energy ratio offered.
It is concluded that independently of the nature of the nutrient promoting imbalance, dietary protein-to-energy ratio may determine post-weaning piglet performance.
SA Guzmán-Pino, D Solà-Oriol, J Figueroa, JF Pérez. 2012. The protein-to-energy ratio is a main driver of growth performance in piglets. Journal of Animal Science, 90 E-Suppl. 3: page 69.