Breed for resistance

Buffalo fly numbers:

There are well documented differences among breeds of cattle in resistance to buffalo flies, with Bos indicus (Zebu type) cattle generally more resistant than Bos taurus (British breed type) cattle. In addition, there are well documented and repeatable differences amongst animals within breeds, and herds, and frequently there are a few animals in a mob that carry a major portion of the flies. Often it is the largest cattle in the herd, or the ones with dark coats that carry most flies. Bulls generally carry more flies than steers or cows, although there are some bulls that have relatively few flies. In addition, there is evidence that susceptibility to high fly numbers is moderately to highly heritable, suggesting that it should be possible to increase resistance to flies by selection if the more resistant animals can be accurately identified. However, the effects of the potential positive association between body size and fly counts needs to be taken into account in any program to breed for lower fly numbers.

Breed to minimise lesions:

It may also be possible to select for resistance to buffalo fly lesions. It seems that susceptibility to lesions, and susceptibility to high numbers of buffalo flies are not strongly related. Instead the tendency to develop lesions is more of an animal-specific trait, possibly as a result of an allergic response to buffalo fly feeding, or to the presence of Stephanofilaria nematodes transmitted by buffalo fly. Once a lesion has developed on an animal, the likelihood of it reoccurring in subsequent years is high, and typically the severity of the lesion gets worse over time.

Although estimated breeding values (EBVs) are not yet available in BREEDPLAN, a scoring system for lesions has been developed and a trial EBV for lesions will be developed once sufficient data has been collected. Scoring should be done late in summer through to autumn when lesions are at their maximum. The scoring system is:

BREEDPLAN

Score

Description

1

No visible lesions.

2

One or two lesions less than or equal to 7 cm in diameter.

3

Three to six lesions.

4

Seven to ten lesions, or at least three sites such as neck, belly and withers.

5

Multiple lesions more extensive than score 4.