The Country Land and Business Association wants dog owners to keep their animals either under strict control or on leads while on walks in the countryside.
The call comes in the midst of the lambing season, when pregnant ewes can abort if they become stressed by loose dogs.
Birds that nest on the ground and other wildlife are also at risk, with their young vulnerable if parents are scared away.
CLA members in the eastern region have recently reported dogs being off leads and out of control on their land, disturbing farm animals and wildlife.
Stories include horses and foals being injured after being hounded inside and outside their paddocks, and damage being caused to areas where conservation work is taking place.
CLA East Regional Surveyor Tim Woodward said: “The CLA’s members go out of their way to welcome walkers who adhere to the Countryside Code. Most people are very understanding and walk with their dogs on leads near livestock – but there are some who do not even consider doing this.
“Dogs should always be under close control when walked on farmland and unless the dog stays closely to heel, this normally means that it should be on a lead. A lead should always be used when in the vicinity of livestock, however well-trained your dog is. It is a criminal offence under the Dogs (Protection of Livestock) Act 1953 if they chase or attack livestock.
“Dog owners should also respect land and property at all times. They should not allow their dog to trespass off a footpath or bridleway, and should also clean up and remove dog mess.”
Mr Woodward also said that people should check whether the land on which they are walking in the countryside is open to public access and if the landowner allows permissive access, being careful to check if dogs are allowed, whether on leads or not.
The CLA is campaigning for the Government to provide clear guidance to dog owners setting out their responsibilities and enable better understanding of the impact their animals can have on livestock and farming practices.
The Association also wants the myriad of rules relating to dogs on different types of access land to be simplified.