Rit Landbúnaðardeildar : B-flokkur - 01.10.1953, Page 82

80
weight (3.9 kilos) than tliose which reared lamhs (lot C), while the former had only
1.32 kilos or 5.4% lighter carcass than the barren ones. this difference not being
significant.
6. Proportionately mnch greater differences were between the lots in the weight
of loose fat than in the weight of dressed carcass, the kidney- and caul fat being 26.2%
lighter in lot B and 45% lighter in lot C than in lot A, tlie differences between any
two lots being highly significant.
7. Lots A and B did not differ significantly in any of the external carcass
measurements. Neithcr wcre there significant differences between lot C and the other
two lots in thc T and F measurements which are primarily indicative of length growth
of skeletal parts, while all the other extcrnal carcass measurements, G, Th, W and U
whicli are influenced by muscle and fat as well as skeletal development were signi-
ficantly shorter in lot C than in lots A and B.
8. There were no significant differences between lots A and B in any of the
cannon bone measurements or between lot A, B and C in the length of this bone. The
weight and minimum circumference of the left fore cannon bone was somewhat lower
in lot C than in lots A and B, though not significantly so, whereas the ratios minimum
circumference over length and weight over length of this bone were significantly
lower at the 5% point in lot C than in lots A and B.
9. Proportionately greater differences were found hetween the lots in the in-
ternal than the external carcass measurements. These differences were greatest in the
fat measurements, less pronounced in the muscle measurements and negligible in the
only internal bone measurement, the length of the spinous process (S).
10. There was no significant difference hetween the lots in the “length” of the
“eye-muscle” (A). The depth of the “eye-musele” (B) was significantly greater in
lots A and B than in lot C and slightly greater in lot A than in lot B though not signi-
ficantly so. Corresponding differences were between the lots in the X-measurement as
in the B-measurement, though somewhat greater in the former.
11. All the fat measurements C, D, J, and Y were from 14.7 to 31.0% lower in
lot B and 35.3 to 62.5% lower in lot C than in lot A. The differences in all these
measurements between lots A and C were highly significant aud also the difference
between lots A and B in the C- and J-measurements and between lots B and C in the
D- and J-measurements.
12. This investigation leads to the general conclusion that pregnancy of ewes
from 7 to 12 months of age and/or the strain of parturation has significant retarding
effects on the growth and development of fat, the latest maturing tissue of the body
up to the age of 16 months, while it has no effects on carcass conformation or the
growth and development of the earlier maturing tissues, muscle and hone. On the
other hand milk production (suckling of lambs) for 4 montlis following pregnancy
from 7 to 12 months results in a lighter carcass, narrower in botli the hind quarters
and the chest at 16 months than if the ewes were barreu. It has however no effects
on growih in length of the earlier maturing bones of the skeleton, wliile it retards
tlieir growth in thiclcness to some extent. It has greater retarding effccts on muscular
development, a later maturing tissue, and by far the greatest rctarding effects on the
growth and development of the latest maturing tissue of the body, the fat, both the
fat of the carcass and the loose fat.
Part II.
1. To study to what extent ewes which have been retarded in development up
to 16 montlis of age hy suckling lambs as yearlings, can make up for this loss from
16 to 28 montlis of age, 64 ewes 28 months old were used, 25 of which were barren
and 39 rearcd lambs as yearlings.
2. When ldlled at 28 months of age these ewes were divided into 5 lots, A, B, C,
D and E. Lot A consisted of 10 ewes whieh liad never reared lamhs. Lot B comprised