EFFECTS OF FEEDING LEVEL AND REARING METHOD ON SEXUAL DEVELOPMENT IN YANKASA SHEEP
EFFECTS OF FEEDING LEVEL AND REARING METHOD ON SEXUAL DEVELOPMENT IN YANKASA SHEEP
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Date
1991-06
Authors
AKPA, GERALD NWACHI
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Abstract
The study examined the effects of feeding level and
rearing method on sexual development in Yankasa sheep.
Seventy-two animals with mean age and body weight of 145.3
+17.7 days and 10.1+2.6 kg respectively were used for the 4
months investigation. Animals were randomised in a 3x3
factorial design with feeding rate at 3 levels (low, medium
and high) and rearing method at 3 levels (males alone,
females alone and both males and females). Sixty-six animals
survived to the end of the experiment, made up of 34
females 32 males. Traits investigated included, age,
body weight and scrotal circumference at puberty,
and changes in scrotal circumference in ram lambs;
progesterone concentrations in ewe lambs, sexual activity
and growth performance in both sexes.
Feeding level and rearing method had highly significant
(P<0.001 and P<0.01, respectively) effects on average daily
gain (ADG) on experiment. The overall ADG (+ s.e.m.)
was 77.8+3.0 g/day. Animals on the low, medium and high
levels gained 66.8+5.49, 77.8+5.6 and 89.0+5.6 g/day
respectively. As feeding level increases, there is a
corresponding increase in live weight gain. Generally, males
gained faster in weight than females.
Males were sexually more active (26 out of 32) than
females (3 out of 34). Mixed rearing produced animals that
were sexually more active (13 out of 15) than males alone (13
out of 17). Sex and rearing method had highly significant
(P<0.001 and P<0.01, respectively) effects on sexual
activity.
Progesterone concentrations in the Yankasa ewe lambs
within 264 days of age was 0.57+0.04 ng/ml. Feeding level had
a very highly significant (P<0.001) effect on progesterone
concentrations, with the concentrations for low, medium and
high levels of feeding as 0.43+0.05, 0.73+0.05 and 0.56+0.04
ng/ml, respectively. Although rearing method had no
significant (P>0.05) effect on progesterone concentrations,
mixed rearing showed relatively higher (0.61+0.04 ng/ml)
concentrations than females alone (0.53+0.04 ng/ml).
Generally, progesterone concentrations decreased with
increase in the sampling date; implying probably that season
of the year might have influenced progesterone concentrations
in Yankasa sheep.
For pubertal determination, the results showed that age,
body weight and scrotal circumference at puberty in the ram
lambs were 232.5+12.7 days, 18.3+0.4 kg and 22.7+3.1 cm
respectively. The implication is that these animals are
capable of breeding from this age. In the ewe lambs, serum
progestrone profiles gave no clear indication of pubertal
age. Feeding level and rearing method had no significant
(P>0.05) effect on age and scrotal circumference at puberty
in the ram lambs. However, feeding level showed a very
highly significant (P<0.001) effect on body weight at
puberty.
Description
Thesis
Submitted to
The Postgraduate School,
Ahmadu Bello University, Zaria
In Partial Fulfillment of Requirements
For The Degree Of
MASTER OF SCIENCE IN ANIMAL SCIENCE
DEPARTMENT OF ANIMAL SCIENCE
FACULTY OF AGRICULTURE
AHMADU BELLO UNIVERSITY, ZARIA.
JUNE, 1991
Keywords
REARING METHOD,, SEXUAL,, YANKASA SHEEP