Effect of replacing soybean protein with protein from ensiled stylo (Stylosanthes guianensis (Aubl.) Sw. var. guianensis) on growth performance, carcass traits and organ weights of exotic (Landrace × Yorkshire) and native (Moo Lath) Lao pigs
The present study examined the impact of replacing crude protein (CP) from soybean with CP from ensiled stylo (ES) on growth performance, carcass traits and organ weights in Landrace × Yorkshire (LY) and Moo Lath (ML) native Lao pigs. Twenty-four castrated male pigs, 12 of each breed, were allocated to the diet treatments according to a completely randomised 3 × 2 factorial (three ES levels × two breeds) arrangement, with four pigs per diet treatment. Pigs were kept in individual pens and fed at 4 % dry matter of body weight for 98 days. The control diet was formulated with soybean meal as the main CP source, and in the other two experimental diets, CP from soybean was replaced at 25 % (ES25) and 50 % (ES50) by CP from ES. Calculated metabolisable energy intake decreased with ES50 diet, while dry matter intake (DMI) and CP intake (CPI) were the highest in ES25 diet (P < 0.001). Overall, average daily gain (ADG) and feed conversion ratio (FCR) were unaffected by diet treatments. Carcass weight, backfat thickness and dressing percentage were unaffected by soybean CP replacement, while the weights of lung, large intestine and stomach were higher (P < 0.001) when 25 % of soybean CP was replaced by CP from ES. LY pigs had higher (P < 0.001) DMI, CPI and ADG and poorer (P < 0.001) FCR than ML pigs. LY pigs had higher carcass weight (P < 0.001), lower backfat thickness (P < 0.001) and higher organ weight (P < 0.001) than ML pigs, except for small intestine weight, where there was no difference between the LY and ML pigs (P > 0.05). In conclusion, ES can replace up to 50 % of soybean CP in the diet of growing Lao LY and ML pigs without negative effects on performance and carcass traits.