Hair Sheep Production in the Southeastern U.S.
USDA Agricultural Research Station
Dale Bumpers Small Farms Research Center
Numbers of hair sheep in the U.S. have increased in the past few
years because of their ease of management and marketability. These
sheep shed their hair, thus require no shearing, and many are resistant
to parasites, a trait of growing importance, especially in the southeastern
U.S. Because of resistance of gastrointestinal nematodes to chemical
dewormers, use of resistant genotypes represents an important control
measure for these parasites. U.S. hair breeds include American and
Barbados Blackbelly, Dorper, Katahdin, and St. Croix.
Out-of-season breeding is an important characteristic
of sheep in the eastern and southeastern U.S. Marketing potential
increases when more than one breeding season is included in reproductive
management because of the increased supply of lamb at different
times of the year. Because sheep are seasonally polyestrus, traditionally
ewes are bred in the fall to lamb in the spring. Length of the breeding
season is dependent largely on breed, latitude and photoperiod.
There is some evidence that St. Croix ewes are capable
of breeding in the spring in Arkansas, but at a reduced rate compared
with other times of the year. Dorper ewes are capable of year-round
breeding in South Africa, but out-of-season capability in the U.S.
has not been determined. Prolificacy is another important trait
of sheep in this area. Lambing rate of St. Croix ewes can range
from 140 to 212% and lambing rate of Katahdin ewes can reach 168%.
Prolificacy of Dorper ewes in South Africa was 141% and has not
been reported in the U.S.
In the current study, Dorper, Katahdin, and St. Croix ewes were
bred in late summer (August/September), winter (December), or spring
(April/May) in Arkansas to assess ability to breed out-of-season
during a 30-day breeding period to respective ram breed after a
21-day exposure to vasectomized teaser rams.
Dorpers were developed in warm, arid climates. The
climate of Arkansas during summer months is warm and humid. Surprisingly,
pregnancy (more than 20%) and newborn lamb losses (more than one-third)
were greater and lamb birth weights lighter for Dorper ewes bred
in the spring compared with Katahdin and St. Croix ewes (Figure
1). It was noted that body condition was good during this period,
suggesting that heat stress, rather than poor nutrition, contributed
to these losses. This suggests that Dorper ewes were more susceptible
to heat stress than Katahdin and St. Croix ewes which had no changes
in lamb losses or birth weights among seasons. Similarly, the summer
breeding period for Dorper and Katahdin ewes resulted in reduced
pregnancy rates compared with winter breeding with no further losses
in mid to late pregnancy. There may have been an initial heat stress
with increased early embryonic mortality or delayed resumption of
the estrous cycle.
Pregnancy rate was similar between summer and winter breeding for
St. Croix ewes (Figure 2), suggesting a greater tolerance
to heat stress. However, pregnancy rate was reduced during spring
breeding. This was likely attributed to an inability to breed out-of-season
in a greater proportion of ewes for all breeds. There were more
St. Croix than Katahdin ewes pregnant at this time, but lambing
rate was similar among the breeds within a season and was similar
among breeds and seasons when considering only ewes that lambed.
Average birth weights of a litter for Dorper, Katahdin
and St. Croix ewes were similar when breeding occurred in the spring,
but otherwise were greater for Dorper and Katahdin ewes. Total weight
of lambs born per ewe was not affected by season and was greater
for Katahdin ewes. Total weaning weights at 60 days of age were
greatest when breeding occurred in the summer for Dorper and Katahdin
ewes and were similar between these breeds (Figure 3). Average
weaning weights were lighter for St. Croix compared with other breeds
bred in summer and spring, but were similar to Dorper and Katahdin
Forage quality and quantity are often greater during late winter
and early spring in Arkansas, contributing to greater weaning weights.
The St. Croix ewes appeared to be less affected by changes in forage
quality throughout seasons compared with Dorper and Katahdin ewes.
In contrast, a previous study at this location determined that weaning
weights of St. Croix lambs were lighter during fall lambing. Supplemental
feeding was offered throughout late gestation and lactation for
all seasons in the current study, but not between May and September
in the previous study, which likely accounts for differences between
The forage base for this flock included endophyte-infected tall
fescue, which reduced pregnancy and calving rates in beef heifers
and increased body temperature of cattle. We reported decreased
pregnancy rates in yearling, but not mature ewes, grazing tall fescuecompared
with bermudagrass at this station. In addition to reduced ability
for out-of-season breeding, reduced pregnancy rates in summer and
spring breeding in the current study could have been attributed
to fescue toxins. Tropically-adapted breeds of cattle were less
sensitive to fescue toxins than English breeds, likely because of
greater heat tolerance. This could be true of St. Croix compared
with Katahdin ewes, although this was not examined. Rectal temperatures
of St. Croix ewes were lower than that of Targhee at elevated ambient
temperatures, indicating greater heat tolerance of St. Croix.
In conclusion, all hair breeds in this study were capable of out-of-season
breeding and early pregnancy rates were highest during winter breeding.
Pregnancy rates and pregnancy and newborn lamb losses were greater
for Dorper ewes bred in spring compared with late summer or winter,
likely due to heat stress. Lambing rate for ewes lambing was similar
among breeds and seasons. Weaning weights of St. Croix lambs were
not influenced by season, but were greater for Dorper and Katahdin
lambs born in winter.
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