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Abstract

We evaluated ewe conception and prolicacy in six ocks on three
sheep farms with similar commercial management conditions in the
Australian State of Tasmania. The aim was to investigate the effects of
BW and BCS at mating, age group, and breed on reproductive traits.
1759 Merino, Composite Merino/Coopworth (M/Coop), Composite
East Friesian/Romney (EF/Rom), and Composite Coopworth/East
Friesian/Texel (Coop/EF/Tex) ewes of maiden (7 mo) and mature
(18 to 30 mo) age groups were evaluated. Body weight and BCS of
ewes were recorded before rams were introduced to the breeding mob.
Ultrasound scanning 90 d after ram removal was carried out. Results
demonstrated that ewes that conceived were consistently of greater BW
and BCS than barren ewes. The average BW of non-pregnant, single,
and multiple-bearing ewes were 41.3, 43.7, and 54.6 kg respectively,
while their corresponding BCS were 2.77, 2.80, and 2.85. However,
highly signicant (P <0.0001) breed, age group, and ock variations
were observed: 7 mo-old maiden ewes had a significantly lower
conception rate than 18 mo-old ewes at the same BW at breeding.
Within the 18-mo age groups, percentages of non-pregnant ewes were
16.7, 3.0, and 2.4% and percentages of multiple fetus-bearing ewes
were 1.4, 53.6, and 74.2% for Merino, Coop/EF/Tex, and M/Coop,
respectively. The Coop/EF/Tex ocks were consistently more prolic
than other breeds with 74.2, and 77.5% of ewes scanned as multiple
fetus-carrying at ages 18 and 30 mo, respectively. Above BW of
approximately 55 kg, the probability of multiple conceptions began to
increase at a greater rate at the expense of single conceptions. The study
shows that nutritional management prior to joining in commercial
Tasmanian sheep ocks has the potential to increase reproductive
performance in ewes. This is of particular importance when ewes
are bred as lambs or from breeds with characteristically low fertility
levels

Item Type:	Article
Authors/Creators:	Malau-Aduli, AEO and Bond, GH and Dunbabin, M
Keywords:	Conception, Prolicacy, Sheep, Bodyweight
Journal or Publication Title:	Journal of Animal Science
ISSN:	1525-3163
DOI / ID Number:	928
Item Statistics:	View statistics for this item

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