| dc.description.abstract | Thirty small East-African goats, 19 females and 11
males aged between 13 and 36 months and weighing 14 to
30 Kg were divided into two treatments consisting of 15
goats each. They were fed ad-libitum on hay containing
0.02 mg Co/Kg DM and each goat was supplemented with
150 g of a commercial concentrate daily for a weeks
experimental period. Goats in treatment 1 were
supplemented with an oral cobalt chloride drench to
raise the dietary cobalt intake to 0.3 mg/Kg DM while
those in treatment 2 were not supplemented. Goats in
treatment 2 were considered cobalt deficient after 10
weeks on experiment when their serum vitamin 812
concentration fell below 200 pg/ml.
The ~ffects of Cobalt deficiency on feed intake,
digestibility of nutrients? rumen degradability of hay,
liveweight change and body condition scores, blood
parameters, serum levels of vitamin 812 and thyroid
hormones plus the rate of resting metabolism in goats
were studied.
For 23 weeks of the experiment, hay intake was not
significantly (P>0.05) different between cobalt
adequate and deficient goats. Rumen degradability of
dry matter and acid detergent fibre in hay, studied by
incubation of dacron bags over 72 hours in two rumen
fistulated goats from each treatment, were not
significantly (P)0.05) different between the
treatmeMts. Apparent digestibility coefficients of the
dietary nutrients were not significantly (P>0.05)
different between the treatments. However, the
concentratioQ of propionic, butyric, valerie and
isovaleric acids in the rumen liquor were significantly
(P(0.05) lower in cobalt deficient than supplemented
goats while there was no significant (P>O.OS)
difference in the concentration of acetic acid between
the two treatments. Rumen liquor concentration of
ammonia was significantly (P(O.Ol) lower and the liquor
pH significantly (P(O.Ol) higher in cobalt deficient
than adequate goats. Gas production from in vitro
fermentation of rumen contents was significantly
(P(O.Ol) lower in cobalt deficient than supplemented
goats. Cobalt supplementation improved the rumen
fermentation of the soluble components of the diet but
not that of cellulose in the hay.
For the twenty-three weeks of the experiment,
changes in bodyweight were not significantly (P>O.05)
different between the two treatments but body condition
scores were significantly (P(O.Ol) lower in cobalt
deficient than adequate goats.
Although packed cell volume, hemoglobin
concentration and erythrocyte counts were significantly
(P(O.05) lower in deficient than cobalt adequate goats,
these blood values were within the normal range for
goats.
Total serum thyroxine was significantly (P(O.Ol)
higher in deficient than in cobalt adequate goats but
the free tetraiodothyronine, triiodothyronine and the
rate of resting metabolism were not significantly
(P>0.05) different between the two treatments.
A dietary cobalt level of 0.02 mg/Kg DM resulted in a
subclinical vitamin 812 deficiency and a mild thyroid
disorder in goats. The possibility that goats are more
resistant to cobalt deficiency than sheep is discussed | en |
