Studies on growth rate, carcass quality and helminth resistance of three strains of Tanzania local Goats
Loading...
Date
2002
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Sokoine University of Agriculture
Abstract
This study was conducted on three strains (Kigoma, Dodoma and Mtwara) of
Tanzanian local goats with the aim of estimating heritability for pre weaning (birth-4
months), post weaning (4-8 months) and yearling (8-12 months) growth rates. Other
heritability parameters estimated were for weight at birth, 4, 8, and 12 months of age
and helminth resistance traits i.e. Faecal egg count (FEC) and packed cell volume
(PCV). Data accumulated between 1997 and 2000 was used to estimate heritability.
The same data set was used to evaluate the effect of sex, birth type, strain, year of
birth on growth rate at four, eight and twelve months of age. This formed part I of the
study. In part II of the study, the effect of worm burden on growth rate was done only
on goats that had available information on PCV and FEC at six and twelve months of
age. This study also evaluated the effect of strain on killing out characteristics,
carcass quality and
composition
as well
as development of prediction
equations/models for carcass weight and carcass tissues. Most of the traits considered
were observed to have (0.32-0.39) moderate heritability, with exception of weight at
weaning, 8 months, one year of age and PCV, which had high (0.4-0.44) heritability.
Strain had a significant influence (P<0.05) on growth rate at four, eight and twelve
months of age. The Dodoma strain had highest daily gain at four months (40.0g),
eight months (37.6g) and twelve months (32.6g) of age compared to that of Kigoma
(34.6g, 35.2g, 31.4g) and Mtwara (32.3g, 29.4g, 26.1g), respectively. Sex had a
significant influence on growth rate only at four months of age. Male kids had higher
daily gain than females. There was a significant effect of worm burden on growth
rate at six and twelve months of age. Dodoma strain showed lowest FEC and highest
PCV and growth rate. Mtwara strain showed highest level of FEC and the lowestiii
PCV and growth rate. Kigoma strain was in between the other two strains.
Susceptibility to helminth infection measured by FEC and PCV indicated that
Dodoma strain did not differ significantly (P>0.05) from that of Kigoma strain, and
that both of them were more resistant than Mtwara strain. Further more, results
indicated a negative correlation between FEC and PCV at both ages. FEC also had a
negative relationship with growth rate at six and twelve months of age, whereas PCV
showed a positive relationship with growth rate. There were significant differences
between strains in dressing percentage (DP), slaughter weight, empty body weight and
carcass weight. Dodoma strain had the highest weights followed by Mtwara and
Kigoma. Dressing percentage was 49.3% in Dodoma strain, 45.5% in Mtwara strain
and 44.8% in Kigoma strain. Strain effects were also observed for edible non-carcass
components when expressed as percentage of slaughter weight. Dodoma strain had the
highest weight of kidney, head, feet, and gut fat compared to Mtwara and Kigoma.
Other edible non-carcass components such as pluck, spleen, liver, and gut were heavier
for Dodoma strain than those of others trains albeit the differences were not significant.
Carcass composition consisted of 70.3, 69.8, and 68.4% for lean; 17.8, 18.8 and 19.7%
for bone; 12.5, 15.5, and 15.5% for fat in Dodoma, Mtwara and Kigoma strains,
respectively. Strain effect was also evident in carcass tissue ratios, with Dodoma goats
showing better proportions than Mtwara and Kigoma. Strain also had significant effect
(P<0.05) on carcass joint weights. The Dodoma strain exhibited heaviest weights of
ribs, breasts, loin and feet than the other two strains. Heart girth was the best
independent variable in predicting carcass weight (P<0.002, R2 = 82.4%). Foreleg joint
was the best predictor of lean (P<0.001, R2 = 92%), while rib joint was the best
predictor of both carcass bone (P<0.001, R2= 87%) and fat (P<0.001, R2= 80%). Of theiv
the three independent variables namely slaughter weight, carcass weight and empty
body weight, carcass weight was the best predictor of lean (P<0.001, R2= 98%) and fat
(P<0.001, R2 =87%), whereas slaughter weight was the best predictor of bone
(P<0.001, R2 = 89%). It was generally concluded that of the threes trains, the Dodoma
strain was superior to the rest in terms of growth rate, helminth resistance and carcass
quality. Selection, bio-molecular techniques and cross breeding could be employed to
improve these traits because they have moderate heritability.
Description
Dissertation
Keywords
Carcass quality, Helminth, Local Goats