Rit Landbúnaðardeildar : B-flokkur - 01.10.1953, Page 79

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frá 16—28 mánaða aldurs um 60% af þroskatapi fallsins, ef þær ganga
með einu Jambi, en aðeins minna ef þær g'anga með tveimur lömbum
tvævetrar, samanborið við þær, sem voru algeldar veturgamlar og komu
upp lambi tvævetrar. Þar sem mismunur sá á lögun fallsins, sem kom
í ljós við 16 mánaða aldur, hjá algeldum og dilkgengnum gimbrum
(kafli I), er næstum því horfinn við 28 mánaða aldur, þótt þær, sem
gengu með lambi veturgamlar, hafi aðeins þrengri brjóstkassa 28
mánaða, og sá þroskamunur á einstökum líkamsvefjum, sem þá er
til staðar, sé næstum enginn nema á fitunni, seinþroskaðasta líkams-
vefnum, sem getur vaxið íangt fram eftir ævi kindarinnar, og afurðir
tvævetlnanna, sem gengu með lambi veturgamlar, í dilltum, voru lítið
sem ekkert minni að vöxtum eða gæðum en afurðir hinna, má draga
þá ályktun, að óhætt só að láta gemlinga eiga lömb án þess að óttast,
að ærnar bíði við það varanlegt þroskatap eða muni gefa lakari afurðir
fullorðnar. Virðist aðeins vera um það að ræða að fullnægja þurfi nær-
ingarþörf ánna á þroskaskeiðinu með nógu góðu eldi.
Abstract and Summary.
The Effects of Pregnancy and Milk Production of Yearling Ewes
on Their Growth and Development.
Material and Methods.
In Iceland as in most other sheep raising countries the gencral practice has been
to mate ewes for the first time in their second year. During the last two decades
good many Iceland sheep farmers have adopted a new practice, viz. to mate their ewes
for the first time a year younger, i. e. when 7 months old. There is, however, dcvided
opinion on wliether this practice will be profitable or not in the long run as some
believc that yearling ewes sucltling lambs will be unable to attain normal growth and
development before reaching the age wlien growth ceases.
To investigate this problem an opportunity was used, when the experimental
flock of sheep at Hestur (The Experimental Farm of the University Research Institute)
had to be slaughtered in autumn 1950 in connection with an eradication of disease
program carried out in the surrounding area. The ewe lambs born in spring (late May
and early June) 1948 and 1949 and kept for the maintenance of the flock were mated
at the age of 7 months. Therefore at the time of slaughter of the flock 24th September
1950 two age-groups of ewes, 1G months and 28 months old, were available for this
study. Only purebred and healthy Iceland ewes were used for this investigation.
The feeding and management of the experimental flock was comparable with
what is considered a good commercial practice in Iceland. During winter the sheep
were lioused at night and grazed on wild pasture in daytime whenever weatlier condi-
tions perinitted. The sheep were handfed indoors when necessary to maintain them in
a predetermined condition and given good quality meadow hay and some concentrates.
The dailj’ ration varied according to weather conditions. During the winter 1948—’49
the wliole flock had to be entirely handfed indoors for months wliereas in 1949—-’50
all the sheep could be grazed throughout the winter. Lambing began on 17th May
each year. In spring 1949 tlie eves had to lamb indoors and were handfed until lOth
June when sufficient green pasture was first available, but in 1950 housing and hand-