10 Years of the Western Maryland Pasture-Based Meat Goat Performance Test
The Western Maryland Pasture-Based Meat Goat Performance Test was initiated in 2006 at the University of Maryland's Western Maryland Research & Education Center in Keedysville. The purpose of the test is to evaluate the post-weaning performance of meat goat bucklings consuming a pasture-based diet, with natural exposure to gastro-intestinal nematodes, primarily the barber pole worm.
Since 2006, 639 mostly Kiko bucks have been evaluated. While on test, they were evaluated for growth performance (ADG), parasite resistance (fecal egg counts), and parasite resilience (FAMACHA scores and the need for deworming). They were also evaluated for carcass muscling, structural correctness,and reproductive soundness. Additional data was collected on larvae ID, forage quality, and diet quality. Top-performing bucks were identified and sold or returned to the farm for breeding.
Ten years of the Western Maryland Pasture-Based Meat Goat Performance Test are summarized in the graphs below. You can click on a graph to expand it. Click on the > symbol to advance to the next graph in the series.
The graphs are for informational purposes only and do not offer a scientific or statistical analysis of the data. Their purpose is to show general trends and make general observations about the data collected in the ten years of the test. The graphs are also not for comparing goats in different years of the test. Each test year is different. The only comparisons of goats that can be made are between goats in the same test year. Nor can you compare the data to another test or to your own farm, because the environmental conditions are different. The purpose of a centralized performance test is to evaluate animals in the same production environment.
The Western Maryland Pasture-Based Meat Goat Performance Test has always maintained its focus on three primary production traits: growth performance (ADG), parasite resistance, and parasite resilience.
Average daily gain
Average daily gain (ADG) is determined by dividing weight gain by days in the weigh period. In most years, the test goats were weighed bi-weekly. In later years, the were weighed twice at the beginning and end of the test and starting and ending weights were determined by averaging the two weights. The test was always proceeded by an adjustment period of 6 to 13 days. The goats generally gained weight during the adjustment period, but this weight gain was not factored into the test results. The length of the test was either 84 or 96 days.
During the ten years of the test, there has been a general decline in ADG. Trend lines have been added to the graph, which shows the average ADG, along with the ADG of the top-gaining goat in the test year. The reasons for the decline in ADG will be discussed and explored in some of the other graphs.
Fecal egg counts
Fecal egg counts (FECs) are a measure of parasite resistance. They estimate the worm load that a goat is carrying, as it is presumed that more worms lay more eggs. A more resistant goat will limit establishment of infection, reduce egg laying capacity of worms, and expell worms -- all of which will result in lower fecal egg counts.
Since 2008, fecal samples have been collected bi-weekly from goats in the test. In the first two years of test, fecal samples were either not collected (2006) or collected less often (2007). The modified McMaster technique was used to determine individual fecal egg counts of goats.
During the ten years of the test, there has been a trend towards increasing FECs. A trend line has been added to the graph. The reasons for the increase in FECs will be discussed and explored in other graphs.
FAMACHA© scores
FAMACHA© scores are a measure of parasite resistance, as they estimate packed cell volumes (PCV) in the animal. PCV is a measure of anemia(blood and loss). Anemia is the primary sympton of Haemonchosis (barber pole worm infection). The barber pole worm is the primary parasite affecting the goats in the test. Since 2007, FAMACHA© scores have been determined bi-weekly. They have been used as the primary criteria for determining the need to deworm individual goats. Goats with FAMACHA© scores of 1 or 2 are not dewormed, whereas goats with FAMACHA© scores of 4 or 5 are always dewormed. Goats with FAMACHA© scores of 3 were sometimes dewormed, depending upon the criteria of the Five Point Check©, and other factors such as weight gain/loss, changes in scores, fecal egg counts, and scores of other goats.
In contrast with ADG and FECs, FAMACHA© scores have remained relatively flat during the ten years of the test. A trend line has been added to the graph. If anything, there has been a (very) slight improvement in FAMACHA© scores over the years.
Interaction between ADG and FEC
The lack of growth (ADG) is of concern to the consignors and test organizers. Parasites (worms) are usually blamed. The following four graphs compare the ADG trend with trends in FEC. The first graph shows that while ADG had trended downward, average FECs have trended upward. Similar relationships can be observed with ending FECs and highest FECs. The ending FEC is the FEC on the last day of the test. It is often the highest egg count observed, as the goats become more infected as the test progresses and the pastures become more contaminated. The highest FEC is the highest average FEC recorded during the test. Depending upon weather, the highest egg counts may be observed earlier in the test.
The incoming FEC is the egg count of the goat on the day it arrived to the test site. It is the result of the parasite challenge the goat faced on its birth farm. Incoming FECs varied considerably by year. They don't seem to have impacted ADG, which makes sense, since the goats are dewormed upon arrival to the test site with anthelmintics from all three anthelmintic clases (albendazole + moxidectin + levamisole).
Overall, the graphs are not surprising, nor alarming (to the test organizers), as the goal of the test is (and has always been) to identify goats that are resistant to internal parasites. To do so, the goats MUST be exposed to an adequate level of infective worm larvae. There must be some goats with very high fecal egg counts. In fact, over the years, efforts have been made to increase the level of infective worm larvae to which the goats are exposed. Since 2013, sheep have grazed the test site, before and after the test. In one year (2012), the goats were dosed with 1000 infective (L3) worm larvae. Pasture rotation has sometimes been delayed to increase exposure to worms.
Selecting for parasite resistance is not "pretty." It has likely come at the expense of ADG. However, the test will continue to emphasize selection for resistant goats, as internal parasites are one of the primary obstacles to profitable goat production. Parasite resistance needs to be established in a herd before other traits can be emphasized. The best way to establish parasite resistance is to use a buck with proven resistance, as can be documented in this test.
As expected, FAMACHA© scores following the same pattern as treatment (TX) frequency. FAMACHA scores and average FEC also show a similar pattern. While ADG has declined over duration of the test, there has been no corresponding decrease in FAMACHA© scores. A trend line has been added to the graph. There has been a slight decline in the number of anthelmintic treatments administered. A trend line has been added. Failure to treat all goats with FAMACHA© scores of 3 is likely contributing to the incidence of sub-clinical parasitism.
Sub-clinical parsitism would be expected to reduce weight gain. Treating a goat prevents it from developing immunity; for this reason, not all FAMACHA© 3s are dewormed. Sub-clinical parasitism will be addressed in the future by deworming any FAMACHA© 3 that loseses weight during the previous 14-day weigh period. In countries in which the barber pole worm is not the primary worm parasites, performance (e.g. ADG) is being used as the criteria for making deworming decisions. This decision-making system has been dubbed the "Happy Factor."
Other effects on ADG
The effects of other factors on ADG are examined in the next several graphs. According to the trend line, there has been a gradual increase in the number of goats in the test (or utilizing the pasture). This trend is opposite of the observed downward trend in ADG. Although, there is almost always adequate forage, higher stocking rates would be expeced to negatively impact weight gain. For several years, a companion study (pen vs. pasture study) resulted in extra goats (10-15) being added to the test herd. The test organizer feel that the higher stocking rates are not problematic, as there is always adequate forage (except in the case of extreme drought), and they contribute to the higher parasite load, which is necessary to identify resistant goats.
Upon arrival, the goats were supposed to weigh between 30 and 70 lbs. In 2015, the minimum weight was increased to 40 lbs. Since 2006, initial weights have trended lower. A trend line had been added the the graph. Lower starting weights may have had an effect on ADG. The final two graphs show the amount of rainfall the test site has received, from June through September. A trend line has been added to the first graph. There has been a general decline in rainfall.
Written by Susan Schoenian in 2016.