Introduction
In the United States, goat production is characterized as a non-traditional,
alternative agricultural enterprise. The meat goat is an emerging class of
livestock offering U.S. farmers a new option for on-farm income. Major
determinants of profitability in a meat goat enterprise are reproductive and
maternal abilities of the doe herd. Genetic composition of does may affect
the performance of progeny. The improved Boer goat from South Africa (Casey
& Van Niekerk, 1988; Campbell, 2003) is a breed developed for meat
production that evolved from selection pressures placed on common goats of
the region by farmers.
Exportation of Boer goats to the U.S. in the mid-1990s helped to stimulate
interest in meat goat production. No goat breeds in the U.S. had been
developed specifically for meat production; milk, fibre, and brush control
were the primary reasons of raising goat with meat being a by-product. The
Kiko from New Zealand (Batten, 1987) is another goat breed exported to the
U.S. in the mid-1990s that was developed for meat production. The Kiko breed
developed from the systematic breeding of selected New Zealand feral does
with dairy bucks, further crossbreeding and interbreeding at the F2 and F3
generations, and breed establishment at the fourth generation (Batten,
1987). Exportations of Boer and Kiko goats have created an opportunity for
goat producers internationally to introduce the germplasm of new meat breeds
into their breeding programs.
Reproduction and maternal ability are important economic traits to consider
when evaluating the strengths and weaknesses of a new breed. When assessing
new breeds for genetic merit in meat animal production systems, the maternal
side is often overlooked. Breed of dam genetics can influence the
performance of any sire’s progeny. Meat goat dam breeds likely differ for
general production efficiency in a given production environment as
documented in sheep (Bourfia & Touchberry, 1993; Bunge et al., 1995;
Dimsoski et al., 1999). Maternal breed has not received much attention in
the area of meat goat production. Breed of dam has been shown to affect body
weight, growth from birth through the post-weaning period and carcass traits
for the progeny of Boer sires and dairy breed sires (Ruvuna et al., 1992;
Waldron et al., 1996; Goonewardene et al., 1998; Ward et al., 1998).
Percentage Boer does did not outperform Spanish does under range conditions
(Ward et al., 1998). Studies involving Kiko-influenced does have not been
published to date in the scientific literature. The reported breed of dam
effects on kid performance were largely based on absolute weights and not
adjusted for dam weight to measure production efficiency. Reproductive and
maternal merits should be considered when making breed of dam choices. The
semi-arid origin of the Boer and humid origin of the Kiko are distinctions
that may influence the merits of these breeds in a given environment. This
project focused on reproductive and maternal abilities of Boer and Kiko does
under the humid, subtropical climatic conditions of the southeastern United
States.
Materials and Methods
In the autumn, 30 Boer and 27 Kiko does were exposed to three Spanish bucks
in single-sire breeding groups to begin evaluating meat goat breeds of doe
for reproductive rates, pre-weaning kid growth, and production efficiency.
Each breed of doe was represented by at least seven seedstock farms and
eight sires.
Does were nulliparous or primiparous purebreds under two years old with age
and parity balanced across breeds. All goats were managed on the Tennessee
State University research station in Nashville, Tennessee, USA (36°17'N,
86°81'W). Nashville is 183 m above sea level and receives an annual rainfall
of 1222 mm. The 12-month rainfall during the study (September, 2002 to
August, 2003) was 1552 mm.
Does were managed in pastures that provided tall fescue (Festuca arundinacea)
for limited grazing supplemented with orchardgrass hay (Dactylis glomerata;
110 g CP/kg, 50% TDN, estimated as-fed) for ad libitum consumption and 682
g/d of a commercial concentrate (160 g CP/kg, 69% TDN, as-fed) medicated
with monensin. Does kidded on pasture without intervention. The spring-born
kids were not creep-fed and bucks were not castrated before weaning. Dams
and kids were weighed at birth and at weaning (14 wk).
Animal weights, litter size, production efficiencies and hoof care for
lameness were statistically tested by analysis of variance. Kid crop percent
was determined by litter size at weaning divided by number of does exposed.
Individual doe health records were maintained, from which cases of lameness
and subsequent hoof treatments were obtained. Kid attrition was analysed by
chi-square. Kid attrition included pre-weaning kid mortality, excluding
stillborns, and kids orphaned due to dam mortality.
Results and Discussion
At kidding, 25 Boer and 23 Kiko does produced at least one live kid.
Stillborns were not included in birthing datasets. Boer dams at kidding were
heavier (P = 0.06) than Kiko dams (48.49 ± 1.25 vs. 45.04 ± 1.32 kg). Litter
size and litter weight at birth did not differ (P > 0.5) between Boer (1.92
± 0.12 kids, 6.05 ± 0.31 kg) and Kiko dams (1.82 ± 0.12 kids, 5.90 ± 0.33
kg). Kid birth weights were similar (P = 0.43) between 46 Boer and 42 Kiko
F1 kids (3.21 ± 0.09 vs. 3.29 ± 0.08 kg). Each litter type differed (P <
0.001) for kid birth weights (singles = 3.84 ± 0.14, twins = 3.23 ± 0.06,
triplets = 2.67 ± 0.13 kg). Bucks at birth were heavier (P < 0.01) than does
(3.40 ± 0.08 vs. 3.10 ± 0.09 kg). Birth traits were generally similar for
the dam breeds.
Pre-weaning growth rates and weaning weights were greater (P = 0.04) for 38
Kiko F1 kids (140.4 ± 4.61 g/d, 16.81 ± 0.51 kg) compared with 32 Boer F1
kids (126.5 ± 5.97 g/d, 15.29 ± 0.65 kg). Bucks had higher (P < 0.01)
pre-weaning growth rate and weaning weights (145.2 ± 4.3 g/d, 17.29 ± 0.47
kg) than does (121.7 ± 6 g/d, 14.81 ± 0.66 kg). Kids orphaned before weaning
were not included in the weaning kid dataset. Kid attrition rates before
weaning were higher (P < 0.01) for Boer than for Kiko (34.8 vs. 9.5%).
These data indicate that pre-weaning performance of the Spanish-sired kids
was enhanced by Kiko dams. Twenty Boer and 21 Kiko dams reared at least one
kid to weaning. Boer and Kiko dam body weights at weaning did not differ (P
= 0.35; 42.42 vs. 40.75 ± 1.25 kg). Weaning litter size was smaller (P =
0.05) and litter weaning weight was lower (P = 0.02) for Boer (1.58 ± 0.09
kids, 26.48 ± 1.51 kg) than for Kiko dams (1.85 ± 0.09 kids, 31.73 ± 1.52
kg). The ratio of litter weight weaned to doe weight at weaning was
greater (P = 0.01) for Kiko compared with Boer dams (78.1 vs. 63.9 ± 4%). In
terms of overall herd efficiency, Kiko does tended (P = 0.10) to wean a
higher kid crop percent and weaned a heavier (P = 0.07) litter weight per
doe exposed (125 ± 19%, 21.55 ± 3.05 kg) compared with Boer does (86 ± 19%,
14.77 ± 2.96 kg). During the 12-month period, Boer does had more (P < 0.001)
episodes of lameness requiring hoof care than Kiko does (3.31 ± 0.31 vs.
1.60 ± 0.33 episodes/doe). Performance comparisons appeared to favour
the Kiko does under these research conditions.
Boer goats have been used extensively in the U.S. over the last 10 years for
crossbreeding with the goal of enhancing growth and conformation of market
kids. In the process, the Boer influence has become pronounced in U.S.
commercial herds as Boer-cross does are retained as replacements. The
substantial numbers of Boer-cross does in commercial herds and purebred Boer
does raised in the seedstock and commercial operations necessitate an
evaluation of this breed for maternal ability under U.S. production
conditions. In simulation work of Blackburn (1995), the production
environment determined if Spanish or Boer does were more productive and
efficient as genetic × environment interactions existed. Unlike the Boer
goat that evolved under semi-arid to arid conditions, the Kiko goat was
developed in a humid environment. Environmental adaptations of the Kiko goat
are speculated as contributing to its fitness and performance at this
research location which is situated in the humid, subtropical climate zone
of the south-eastern United States. Comparatively higher pre-weaning kid
attrition rates and greater hoof care requirements of the Boer further
suggest that the Boer may be less adapted to a humid environment. Poor
environmental adaptation could negatively influence performance. The
evaluation of various doe breeds for performance within unique environmental
settings is warranted.
Conclusions
This project was designed to evaluate Boer and Kiko does for economically
important production traits under the humid, subtropical conditions of the
south-eastern United States. The Kiko exhibited greater performance levels
and efficiencies compared with the Boer for doe-kid performance. These
initial results suggest that Kiko does would be a viable breed option to
enhance doe-kid performance in commercial meat goat production systems of
the humid subtropics. The reader is cautioned, however, that the current
dataset is
based on a rather small sample, thus is preliminary in character at this
stage of the study. Nevertheless, results highlight the need to evaluate new
breeds under unique environmental conditions for doe fitness, reproductive
and maternal traits that are important to commercial meat goat production.
References
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The South African Journal of Animal Science is available online at http://www.sasas.co.za/sajas.html
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