Abstract
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 m 2 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 (p<0.05). Back fat thickness in MC (33.1 mm), F1 (23.0 mm) and F2 (20.5 mm) pigs was different and within genotypes was the lowest at intermediate CP levels. In conclusion, increasing the dietary crude protein contents in practical diets for pigs in Vietnam can increase production on small holder farms. Optimal performance for MC, F1 and F2 pigs is achieved at different dietary crude protein contents.
Highlights
In recent years, pig production in Vietnam has seen the use of more lean genotypes of pigs for meat production and as a result fattening performance and carcass value have increased (Pham et al, 2010)
ADG, Average daily feed intake (ADFI) and Feed conversion ratio (FCR) after 150 days of fattening were significantly different between the different genotypes of pigs and across the four crude protein concentrations
There was a significant interaction between genotype and crude protein concentration for the final weight, ADG, ADFI and FCR
Summary
Pig production in Vietnam has seen the use of more lean genotypes of pigs for meat production and as a result fattening performance and carcass value have increased (Pham et al, 2010). Pure lean type pigs and local breeds are very different in terms of lean meat percentage. There is evidence (Pham et al, 2010) that conditions in Central Vietnam may not be well suited for the production of pure lean types of pigs. Growth rate and carcass traits are influenced by genotype and environment and by nutrition, especially by dietary protein (i.c. amino acid) content. Cromwell et al (1993) found that increasing the dietary protein or lysine level resulted in improved rates of gain and in increased carcass leanness in gilts
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