Results of five years of selective breeding of New Mexico range sheep

              .--""'NEW MEXICO COLLEGE-OF AGRICULTURE. AND MECHANIC ARTS
AND AGRICULTURAL EXPERIMENT STATION
Press Bulletin 999
. RESULTS OF FIVE YEARS.OF SELECTIVE BREEDING OF KW MEXICO RANGE
SHEEP
A.breeding program based on mating the best wool-producing range'ewes with
the best wool-producing range rams has been followed for five ye^rs. This work
began at shearing time in the spring of 1940 and has been followed each year, including this year, 1944-
The method of selecting the ewes and rams was as follows: at shearing time
the ewes were divided into three groups—the longest-wooled, the medium-length-
wooled ewes, and the shortest. This was done by opening the wool of each sheep
j-ust back of the hip and estimating the length. The longest-wooled were chalk
marked on the head, the medium on the back, and the shortest on the rump. Each
group was then separated and sheared separately. The head-marked ewes, or longest-
wooled ewes when sheared were required to yield a minimum fleece weight. ?o determine the heavy-shearing' ewes in :this group, the fleece from each ewe was weighed
and if she did not shear above 9 pounds, she did not retain the head mark after
shearing. When Completed, this method identified all of the longest-wooled and
heaviest-shearing ewes. These ewes were paint branded with a separate brand. The
rams were worked in the same manner. At breeding time, these best ewes and best
rams were separated from the other ewes and rams and mated together. The first
lambs from this svstem of selective breeding were dropoed in 1941 and were sheared
in 1942.-   -. ..
TABLE 1.—THE EFFECT OF PROPER SS
LECTION OF EWE LAMBS AND OF SELECTED MATING
ON INCREASED CLEAN- TOOL PRODUCTION OF YEARLING
E'ES.
Years
1940
1941
1942
1943 .
1944
lbs.
lbs.
lbs.
lbs.
lbs.
Increased production due to selecting
the largest and longest-wooled ewe
.00*
.40
.40
.40
.40
Inoreased production due to selective
mating of the best ewe's and rams
.00*
.00
.68
.43
.70
Each year's increase above 1940 production
.00*
.40
1,08
.83
1.10
s program started.
of the yearling e
In 1940, the first year 1
out because, of. short wool, Tr
That fall when he selected the
longest-wooled ewe lambs with
he grading work was done, many yearlings were marked
e ranch foreman was much interested in the *ork.>.
replacement ewe lambs, he selected the largest,
results showing that by selection alone he increased
irling. This .40-pound incre-