Rit Landbúnaðardeildar : B-flokkur - 01.09.1961, Blaðsíða 112

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rye also had a high rate of gain. On the other hand, all treatment groups made a slower
rate of gain per day in experiment No. X. Comparison of the average rate of gain in
dressed carcass for unweaned lambs on hill pasture and weaned lambs on marrow-
stem kale in eight experiments where these two treatments were available i.e. in
experiments No. VIII, IX, X, XI, XII, XIII, XIV, aud XV, showed a difference in rate of
gain of 50.4 g per day in favour of the Iambs on marrowstem kale. This difference was equi-
valent to 1.51 kilos dressed carcass per larnb per month. Young grass gave slightly less gain
than marrowstem kale in the two experiments where these two treatments were compared.
Green oats and winter rye gave slightly poorer results than marrowstem kale but better than
young grass in the one experiment where these treatments were compared. Mixture of rape,
turnips and young grass gave better results than marrowstem kale in one experiment.
3. The great difference between treatment groups in dressing percentage at slaughter
,cold weight) shows that the growth in live weight of lambs on different autumn grazings
is ol little value as a mcasure of growth in carcass weight. As a rule lambs on forage crops
gave much higher dressing percentage than on hill pasture.
4. Iit most treatmcnt groups ram lambs made greater gain per day than ewe lambs,
especially in the groups where the rate of gain was greatest. In some treatment groups
especially those on hill pasture where the rate of gain was lower the females made as
great and evcn greater gain tlian the males, indicating tliat males must be on a higher plane
of nutrition at the agc in question to bc ablc to utilize their inherent grcater growth capacity.
5. In most of the experiments the carcasses of lambs in the treatment groups grazed on
ctdtivated land graded more favourably than those on hill pasture prior to slaughter,
whether killed in the beginning or at the end of the experiment.
6. In experimcnts No. VII, VIII. IX, X and XIV, the carcass quality of the lambs was
studied by the carcass measurement method, both „external“ and „internal" or cross section
measurements at the Iast rib were used. These studies showed that the lambs which
gained a considcrable amount in dressed carcass weight did not only put on fat but gained
also considerably in muscle and bone. The lambs increased in size, bones and muscles grew
in length, bones increased in weight, muscles increased in thickness while subcutaneous fat
increased only slightly in thickness. This shows that there is little or no danger of lambs
at this age becoming too fat although grazed from 3 to 6 weeks prior to slaughter on forage
crops, such as marrowstem kale.
In most of the experiments the lambs on the hill pastures lost some subcutaneous fat dur-
ing the experimental period although they gained in carcass weight in all but one of the
expcriments. This shows that bone and even muscles can grow at the expense of fat, the
latest matureing tissue of the body, when available nutrients are not sufficient for growth
of all body tissues.
7. Average gain in saleable products for each treatment in the 11 experiments where a
control group of lambs was killed at the beginning of each experiment are given below: