Effect of genotype and dietary protein level on growth performance and carcass characteristics of fattening pigs in central Vietnam

This study aimed to determine the optimum dietary crude protein level in a typical diet for fattening pigs fed ad libitum under normal climate conditions in Central Vietnam. One hundred and ninety two gilts of Mong Cai local breed (MC), F1 Large White??Mong Cai and F2 crossbreds of (Landrace??Mong Cai)??Large White were used. At the start of the experiment, Mong Cai pigs weighed 12 kg at 11 weeks of age, F1 pigs 12.1 kg at 8 weeks of age and F2 pigs 12.2 kg at 8 weeks of age. Four diets differing in crude protein (CP) content (10.1, 13.1, 16.1 and 18.9% in DM) were formulated from rice bran, corn meal, cassava meal and fish meal. Calculated digestible energy content of the diets ranged from 13.5 to 13.8 MJ per kg DM. Pigs were housed individually in pens of 2.5 m2 each and had ad libitum access to feed in a trough as well as water in bowls. The final weights after a growing period of 150 days were 66, 86 and 96 kg for MC, F1 and F2, respectively. Feed intake of MC pigs was highest at 13.1% CP while F1 and F2 had the highest feed intake at 16.1% CP. The results showed that for MC the maximum gain was obtained at levels between 13 to 16% CP. For the F1 the maximum gain was at dietary protein levels of 16-17%. For F2 the max gain was obtained at CP levels of 16 to 18%. Feed conversion was highest in MC pigs (~4.0) followed by F1 (~3.3) and F2 (~3.1), and within genotypes was lowest at the optimum CP level (