Vet on call: Enemy within your goat herd

It was Bob, a manager at a farm in Kiambu. He reported that their goats were doing well for about four years but of late, he had noticed many kids were dying and the goats were gradually becoming smaller in size.

I found Bob’s call rather interesting because Eddy, one of the students, had wanted during the review to know if I had encountered cases of inbreeding in pigs, goats and sheep.

I informed Eddy he was either a prophet or a very lucky fellow. “Your attachment is ending tomorrow, you complain of lack of goat cases and now we have a case that appears genetic,” I told him.

On the way to the farm, I briefed the students on the case report and we discussed the possible causes of the high mortality of kids and reduction in the body size of the goats. The students’ integration of knowledge on the different aspects of veterinary medicine and practice had greatly improved during their attachment period.

They were able to list all the possible causes of the farmer’s observation on his goat herd and then argue why some of the listed causes were unlikely to be the culprits on the farm.

In short, the students had perfected the medical art of differential diagnosis. This is the process by which the doctor is able to come up with the three to five most likely causes of a disease before and after seeing a case to finally make the confirmed diagnosis of the problem before deciding on the treatment or intervention required.

Mike, who was the case team leader among the students, explained that it was most likely the goats were suffering from inbreeding.

I was impressed because the knowledge showed the students could explain complex scientific matters to lay people.
Once on the farm, Bob led us to the enclosure where the goats were gathered. The herd was made up of mainly the Small East African goat crossed with Galla goats and the dairy goat breeds of Saanen and Toggenburg.

NEEDED DEWORMING

The main breed characteristics were, however, the Small East African and Galla goats. I explained to the students the situation was not unusual because the two are the predominant breeds of goats in Kenya.

The students diagnosed the goats needed deworming because some of them were producing dung instead of the individual pellets that are typical of the animal’s droppings. Bob confirmed the goats had not been dewormed for the last four months.

One goat kid was sickly and I treated it for nutritional imbalance and inadequate feeding. I advised the manager to ensure the kid was fed on cattle milk since its mother was not having enough.

Coming to the major complaint, Bob explained, “Doctor, my goats kids have been dying in increasing numbers over the last one year before they stop suckling. This is decreasing the growth of my herd size and if unchecked, the goats may eventually get finished.”

He further said he had noticed that many of the kids that survive were not growing fast like before and their mature size was smaller than both parents.

I tasked the students to examine the goats and give me their herd and individual goat observations. They found that there were three large bucks which had definitely fathered about 25 goats in the herd of 40. The bucks were large, very healthy and obviously of good breeding material.

They weighed 70-80kg. There were 17 does (female goats) of varying ages and sizes and also 12 males of various ages and sizes. The males were all much smaller than their fathers and they did not show the potential to grow to the same or approximate size.

The students were able to predict that from the lengths of the bodies, the lengths of the bones of the legs and the development of long horns and beards. All the males were entire, meaning they were not castrated.

PREVENT INBREEDING

There were only eight large females. The others were smaller than their mothers. Bob confirmed no new goats had been brought from outside the herd in the last three years.

After the full herd examination and taking the complete history from Bob, the students concluded the goat herd was experiencing the early stages of inbreeding depression.

Inbreeding occurs when animals that are closely related are bred deliberately or by chance. Inbreeding depression is the occurrence of undesirable traits in the herd that threaten the performance and survival of the herd. Bob’s goats were initially from three bucks and six does.

The first breeding pairs were unrelated. After the first generation of goats were born, some of the daughters bred with their fathers and the sons with their mothers because all the male off-springs and the original bucks were left entire. Later, brothers and sisters were also breeding.

Inbreeding brings out both desirable and undesirable traits in the off-springs. However, most undesirable traits relate to economically unfavourable outcomes such as poor survival of the young, low growth rate, small body size, poor immunity and poor fertility in both males and females.

These are the factors that then contribute to the diminishing body size and number of the goats in the herd.

To prevent inbreeding, a goat farmer needs to adopt good and simple breeding strategies that ensure that the goats are only bred with others that are not closely related.

The highest level of relationship that is allowed in the goat herd is 6.25 per cent. This translates to breeding a great grandfather buck with its great granddaughter or a great grandmother doe with its great grandson.

In small-scale goat production, the recommended strategy is to breed a buck with does at the rate of 25 to 40 does per buck, then remove the buck when its daughters attain breeding age and bring in new unrelated male.

All males from each buck should be castrated before breeding age or removed from the herd. In large-scale production, bucks can be rotated among herds of unrelated does and breeding bucks can also be selected from the various herds on the farm.

I advised Bob to castrate all the males on the farm including the three dominant bucks and bring in a new unrelated breeding male.