Numerous investigations throughout Asia have documented the severe cruelty inherent in all stages of the dog meat trade- sourcing, transport, sale and slaughter:
Sourcing
Dogs are often sourced from the streets either through catching roaming dogs or by stealing pets. The dogs are caught using iron pincers, which are clamped around the neck or leg, and then used to drag and lift the dogs into trucks. “Dog napping” (i.e. stealing pet dogs) has become a growing issue in many countries, including Vietnam.
Transport
Dogs are often transported long distances, sometimes on journeys lasting for days. They are usually tightly packed into cages without food, water or rest, and often suffering from diseases and injuries from rough handling. Many dogs die from suffocation, dehydration or heatstroke long before they reach their destination.
http://acpagroup.org/the-dog-meat-trade/the-dog-meat-trade-a-severe-and-prevalent-animal-welfare-concern.html#sigProId6f1844f1c6
Sale and slaughter
The dogs’ journey ends at a slaughterhouse, market or restaurant. Slaughtering methods vary between countries, provinces, slaughterhouses and restaurants, but include bludgeoning with a heavy metal pipe, having their throats slit, or being stabbed in the chest with a large knife. This often happens in full view of other dogs.
http://acpagroup.org/the-dog-meat-trade/the-dog-meat-trade-a-severe-and-prevalent-animal-welfare-concern.html#sigProIdd5b261d00d