Because the needle that goes in hurts
Most likely the vet was in too much of a hurry or brusque with the needle. I have witnessed a gentle and caring euthanasia of a pet (mine) by a good vet. The dog never made a sound, slowly fell asleep, and went out from there.
A dog may yelp when given insulin because the injection can cause discomfort or pain at the injection site.
The dog can yelp loudly.Many of the wolves yelped as i ran away.
To prevent his sick dog from suffering anymore, he wanted his dog to have euthanasia.
check with local law
Most possibly from fear
Female dogs may vocalize, scream, or yelp during mating due to discomfort or pain caused by the male dog's behavior, the mating process itself, or underlying health issues. It's advised to consult with a veterinarian to ensure your dog's well-being and to discuss potential reasons for her vocalizations during mating.
39 pennies (74 for a rottweiller)
Because he doesnt like it or he is really excited ... you can tell by there faces
The dog might have a tender spot from an injury or, if it had a previous owner who abused it, the dog could be anticipating being hit and not petted.
A dog will usually yelp if you hurt them in some way. A yelp is a sharp high pitched bark. Grunting could mean they are happy. Or it could mean they are unhappy with being picked up, read the rest of your dog's body language to tell the difference.
You wouldn't let your dog suffer. Why would you let your loved ones?