Rit Landbúnaðardeildar : B-flokkur - 01.10.1953, Side 84

82
12. The fat measurements were all much better developed in the lots wliich were
barren in their second year (A and E) than in the olher lots. All these measurements
were significantly greater in lot A than in lots B, C and D except there was not a signi-
ficant difference in the C-measurement betweeu lots A and B. These measurements
were also greater in lot A than in lot E thougli not significantly so. Tliough the dif-
ferences in the fat measurements betwcen lots B, C and D were not significant all these
measurements were however higher in lot B than in lots C and D, and lowest in lot D.
13. As two tooths the ewes in lot B gave on the average lamhs with 0.5 kilos
greater dressed carcass weight than those in lot C. This difference, however, is not
significant and is considered due to a slight age difference of the lambs rather than
to different productive capacity of tlie ewes in these lots.
14. Part II of this investigation leads to the conclusions that ewes, whose growth
and dcvelopment has been retarded up to 16 months of age as described in Part I by
suckling lambs as yearlings, can make up from 16 to 28 months about 60% of the retarda-
tion in carcass weight whether they are rearing singles or twins, when two years old,
compared with ewes which were barren as yearlings and reared singles as two tooths.
As the difference in carcass conformation observed between these treatment groups
at 16 months has nearly disappeared at 28 months, the former at that age having only
slightly narrower chest than the latter and the remaining differences in development
of the major tissues of the body being neligible except in the fat, the latest maturing
tissue, which can continue to grow after the animal has passed the age of active
growth of all other tissues, and as the production in lambs from both groups as two
tooths was practically equal in quantity and quality one can draw the conclusion that
Iceland ewes can safely be mated in their first year of life without thereby running
the risk of seriously and permanently checking their normal growth and develop-
ment, provided their nutritional requirements are satisfied to the same extent or
better than was done in the case of the ewes used l'or this investigation.
Heimildarrit.
Bonsma, F. N., (1939). University of Pretoria Publ. Series I, Agriculture No. 48.
Fisher, R. A., (1950). Statistical Methods for Besearch Workers, London.
Hammond, J., (1932). Growth and Development of Mutton Qualities in the
Sheep, Edinburgh.
Hirzel, R., (1939). Onderstepoort J. Vet. Sci. 12, 379.
Jónsson, Ólafur, (1951). Gróðurtilraunir, Akureyri.
McMeekan, C. P., (1940). Journal of Agricultural Science, 30, 276.
Pálsson, H., (1939). Journal of Agricultural Science, 29, 544.
Pálsson, H., (1940). Journal of Agricultural Science, 30, 1.
Pálsson, H., & Vergés, J. B., (1952). Journal of Agricultural Science, 42, 1.
Underwood, E. J., & Shier, T. L., (1942). Journal Dept. Agriculture Western
Australia, 19, 37.
Walker, D. E., & McMeekan, C. P., (1944). New Zealand Journal of Science and
Technology, 26, 51, 61, 99 A.
Wallace, L. R., (1948). Journal of Agricultural Science, 38, 93, 368.