David L. Morris: Vet Column 3-21-11
March 21, 2011
From 1987 to 2007, global meat goat production increased by 92 percent with an estimated 386.5 million head in production. In the United States during this time period, meat goat inventory increased by 527 percent to an estimated 2.6 million heat. Expanded inventories have included a variety of indigenous, naturalized, improved, and imported breeds.
Reproductive output is the production trait with the greatest impact on profitability in a commercial meat goat operation. When new breeds are considered for incorporation into a breeding system, survivability as a fitness measurement to indicate a level of adaptation or hardiness is often overlooked. Investigators from Tennessee State University recently published data involving the three main meat goat breeds used in the United States, Boer, Kiko, and Spanish breeds.
Boer goats were developed in the semi-arid region of South Africa through selection from within the local goat population. Kiko goats are a composite breed developed in humid New Zealand by crossing Saanen, Toggenburg, and Nubian bucks with feral does. Boer and Kiko goats were imported by the United States in the early 1990s. The Spanish goat is a nondescript naturalized genotype that evolved in the semi-arid region of Texas from stock brought by Spanish explorers, with sporadic infusion of Angora and dairy breed germplasm. Historically, Spanish goats were used for vegetation control, cashmere production, and meat production.
From September 2003 to August 2009, 132 Boer, 92 Kiko, and 79 Spanish straightbred does were mated to 23 Boer, 18 Kiko, and 14 Spanish straightbred bucks. All does were 2 to 8-years-of-age. Boer does were from 45 source herds and 86 sires; Kiko does were from 18 source herds and 28 sires; and Spanish does were from six source herds and 17 sires. Data evaluation included 1,041 doe-years. All goats were evaluated from the same location near Nashville, Tenn., and is classified as humid, subtropical.
On the basis of at least one live kid delivered at birth, Kiko and Spanish does performed better than Boer does, 96 percent, 94 percent, and 80 percent, respectively. Breed of dam did not affect litter size and litter weight at birth. Weaning at three months, the proportion of available does weaning at least one kid was less for Boer does (53 percent) than for Kiko (84 percent) and Spanish does (82 percent). Litter size at weaning was greater for Spanish does (1.74 kids) than for Kiko (1.59 kids) and Boer does (1.47 kids).
Litter weaning weight was lighter for Boer dams (50.7 lbs.) than for Kiko (60.0 lbs.) and Spanish dams (58.4 lbs.). The efficiency ratio of litter weight to dam weight at weaning favored Spanish does (68 percent) over Kiko does (62 percent) and Boer dams (51 percent). Annual rates of lameness, endoparasitism, and attrition, respectively, were greater for Boer does than for Kiko and Spanish does. Fecal egg counts post-kidding were less for Spanish dams than for Kiko and Boer does.
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In this study representative of the southeastern United States, Boer does expressed substantially decreased levels of fitness compared with Kiko and Spanish does when semi-intensively managed on humid, subtropical pasture. Matching the animal to the environment is an important consideration when choosing breeds for mating systems.