Among the six domestic animals (pig, ox, goat, horse, fowl and dog), cows and dogs are the most useful and harmless animals for human beings.
In the ancient times, Oxen and cows were around to help us transport goods, plowing for farming, their milk as our drinks and their flesh as our foods too. Dogs were around for protection of premises, helping in hunting other animals, as well as our dishes on dining table. They've always been loyal to human beings. They're obedient and hardly complain. To these days, we benefit from their company pretty much the same.
A small change though; dogs have since escalated her status as pet too. Many different breeds of dogs are human beings' favorite pets and some are as close as family members. The same probably can't be said for cows, pigs, goats, deers, chicken; they've all become human's favorite foods.
In order to make them foods for our mouth and stomach we need to make them dead. To make them dead we need to slaughter and kill them. Who would wanna be slaughtered to death? What kind of pains involved in slitting one's throat to death? Do we believe animals have no sensory perceptions? So they don't see, hear, taste, smell, touch and therefore don't feel any pains?
Do we want such pain and torture in slitting our throats and bleeding to death?
Please spare them the pains... especially the ones that have helped us so much.
Let's start by not eating beef... cows... dog meat...
and then pork... pigs...
and then deers, lambs, horses...
and then chicken...
and then all living animals...
and then all living beings...
Note: Comic drawn by 牧谷(Mu Gu). Original wordings translated to English: [Among the domestic animals, those that benefit mankind the most and least harmful to us, are cows and dogs; must not be eaten.]