Wednesday, October 21, 2015

Ten Most Worm Resistant Bucks

Despite the record high fecal egg counts, several bucks demonstrated resistance to parasites during this year's Western Maryland Pasture-Based Meat Goat Performance Test. In fact, several consignors had more than one buck with demonstrated resistance to internal parasites (worms -- primarily the barber pole worm).

The previous standards (Gold, Silver, and Bronze) for parasite resistance required average fecal egg counts of less than 500, 750, and 1000 epg, respectively, and high egg counts not to exceed 1000, 1500, and 2000 epg, respectively. While these standards are still being considered, the overall goal of this year's test is to pick the 10 top-performing bucks, given the conditions of this year's test.

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Fecal samples were collected from the rectum of each buck every two weeks. Occasionally, an individual fecal sample could be obtained without having to probe the rectum. The first fecal samples collected on June 26 do not factor into the test results, since they are the result of previous management and environmental conditions.

The purpose of the initial sequential deworming with albendazole, moxidecin, and levamisole was to reduce fecal egg counts to (near) zero and to ensure that all the goats started the test equally and "free" from parasites. This way, the differences observed in parasite resistance (and other traits) could be attributed to genetics and not environmental differences. While the sequential deworming was not effective in all goats, the median fecal egg count reduction was 96 percent.

For the test to be valid, all bucks must be treated the same. They must comprise a single contemporary group. Test bucks are not a "perfect" contemporary group, but the test offers the best opportunity to make buck-to-buck comparisons for the traits being measured.

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In the test, each buck has seven potential data points for parasite resistance. Unfortunately, it is not always possible to obtain a fecal sample (2-4 g) from a goat, despite multiple attempts. Missing samples (data points) are a dilemma. Every sample that is collected has the potential to yield a high (disqualifying) fecal egg count).  No sample = no high egg count.

Only bucks with at least FIVE fecal egg counts (data points) will be considered for top-10 selection. Missing egg counts during the last four weeks of the test may also preclude a buck from top-10 consideration, since these were the sampling days when egg counts were most likely to be high. Missing samples in the early part of the test, when egg counts were low due to the initial sequential deworming, are less problematic.