Farmers in Laos traditionally keep pigs of predominantly indigenous breeds in foraging systems. The number of pigs kept by a household varies between 1.4 and 3.7 animals, depending on the region (Knips 2004). There are several breeds of local pigs called: Moo Chid, Moo Laat, Moo Daeng and Moo Nonghaet. They are slow growing with high fat content in the carcass. Mature body weight in sows ranges from 60 to 90 kg except for the Moo Chid that is smaller. The litter size is usually small (7 to 8) and the farrowing interval about 1.5 litters per year. The native breeds are hardy, well adapted to a free-ranging system and can survive in a hot climate on low quality feed, and with a high resistance to diseases (Vongthilath and Blacksell 1999). A small number of farmers use exotic breeds or crossbreeds, but compared to local breeds they are considered to be less resistant in smallholder farming conditions and do not perform as well. The type of feed given depends on the farming system, the availability of labor and suitable natural vegetation. Feeds include rice bran, broken rice, banana pseudostem, taro, yams, maize, cassava, by-products (especially rice distillers’ waste) and vegetation collected in fallow fields and forests (Stür Werner et al 2002)
Lon Mong Cai (Mong Cai pig) is an indigenous breed that originated from Quang Ninh province, in northern Vietnam. The breed is very well adapted to the harsh conditions in the region and is known for its early puberty, good litter size and maternal ability. The Mong Cai have been shown to perform better than Large White sows when the diet is based on forages (Nguyen Van Lai 1998 and Hoang Nghia Duyet et al 2006).
In Lao villages, where most farmers are growing paddy rice for sale, the feed for pigs is based on rice bran, which is fed together with a small amount of green feed. Thus rice bran is available in most farm households. The main problem is the supply of protein as soybean and fish meals are not available in rural areas. Phengsavanh and Stür (2006) showed that growth rates were increased from 100 to 200 g/day by providing some protein-rich forage in the form of stylosanthes. However, other forages appear to have more potential in pig diets based on rice bran. Thus Bounhong Norachack et al (2004) reported that N retention was two times higher when cassava leaves replaced stylosanthes.
The hypotheses underlying the present study were that: (i) the growth performance of local Moo Laat pigs and Mong Cai pigs imported from Vietnam would be improved when rice distillers’ by-product was added to a basal diet of rice bran and water spinach; (ii) the Mong Cai breed would have superior performance compared with the local Moo Laat breed; and (iii) a supplement of fresh water spinach will lead to improvements in the apparent digestibility of the basal diet of rice bran.