Browsing by Author "Petersen, P.H."

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Analysis of genetic Diversity and relationships of Tanzania local goat populations using microsatellite DNA markers
(2002) Chenyambuga, S.W.; Watts, P.C.; Hirbo, J.; Kemp, S.J.; Hanotte, O.; Kifaro, G.C.; Gwakisa, P.S.; Rege, J.E.O.; Petersen, P.H.
Genetic diversity among seven Tanzanian goat populations (Ujiji, Sukuma, Ugogo, Maasai, Mbeya, Newala and Coastal goats) was investigated by determining polymorphisms at 19 microsatellite DNA loci, West African Dwarf Tswana, Landim and Toggenburg were included to serve as reference breeds. Among the Tanzanian populations, mean number of alleles per locus was highest (6.26 ± 0.670) in Sukuma and lowest (5.74 ± 0.545) in Newala. Gene diversity ranged from 0.553 ± 0.036 (Newala goats) to 0.646 ± 0.028 (Mbeya goats). The coefficient of gene differentiation (Gsr) indicated that 13% of the genetic diversity in all populations was due to difference between the populations. The genetic distance values ranged from 0. 068 (between Sukuma and Ugogo goats) to 0.2178 (between Ujiji and Coastal goats). The neighbour-joining dendrogram constructed to show population relationships indicated that the Tanzanian populations were separated from the populations, used as reference, breeds. The dendrogram revealed three, sub-clusters of the Tanzanian populations. Coastal and Maasai goats Ugogo and Ujiji goats and Sukuma Mbeya and Newala goats. The principal component analysis separated the Newala goats from the other Tanzanian goat populations. It is concluded that the level of genetic variation within, the goat populatiions was reasonably high and there was no significant difference between the population with respect to the number of alleles and the level of heterozygosity.
Genetic and phenotypic parameters of reproduction and lactation traits of Friesian X Boran crossbred cattle in Kagera region, Tanzania
(2002) Mwatawala, H.W.; Kifaro, G.C.; Petersen, P.H.
This study was done to estimate genetic and phenotypic parameters for Friesian x Boran crossbred dairy cattle of Kagera region. Parameters estimated were heritability, repeatability and phenotypic correlations of various lactation and reproductive traits. Variance component (VARCOMP) procedure and general linear models (GIM) Procedure of SAS were employed in data analyses. Heritability estimates for 100-day milk yield, 305-day miik yield lactation milk yield (LMY) lactation length (LL). dry period (DP) age at first calving and calving interval (CI), were 0.27, 0.40. 0.40. 0.00. 0.04. 0. 05 and 0.06, respectively. Heritabilities first, second and third CI were 0.02, 0.06 and 0.11 re.spectively. Coefficients soil repeatability for 100-day. 305-day. LMY, LL, DP and CI were 0.34, 0.40, 0.38, 0.15, 0.12 and 0. 16, respectively. Correlation coefficients between mean dairy milk yield (DMY) in a month with 100-day and 305-day milk yield and LMY ranged from 0.11 to 0.90, 0.35 to 0.78 and 0.42 to 0. 63, respectively. Correlation coefficient between -100day miik yield and 305-day milk yield (rc=0.87) was higher than correlation coefficient between, 100-day and total lactation yield (rc=0.70). The correlation coefficient between 305-day milk yield and LMY was 0.85. All correlations were highly significant (P < 0.001). Heritability estimates were moderate for milk yields and l0w for LL, DP, AFC, and CI. Selection for genetic improvement in milk yield is possible while low estimates for LL, DP, CI and AFC, suggest that environment plays a major role in affecting these traits.
Reproductive and lactation performance of crossbred dairy cattle in Kagera region, Tanzania
(2002) Mwatawala, H.W.; Kifaro, G.C.; Petersen, P.H.
This study was done to evaluate reproductive and lactation performance of crossbred dairy cattle in Kagera region, Tanzania. Traits studied were age at first calving (AFC), calving internal (Cl), lactation milk yield (LMY) and lactation length (LL). Records for the various traits were compiled covering the period between 1979 and 1999. The General Linear Models procedure of SAS was used in data analyses. The mean AFC and CI were 39.0 months and 464. 7 days, respectively. The mean IMY and LL were 2332.5 kg and 367.2 days respectively. The influences of year of birth and genetic group on AFC were highly significant (P<0.001). Heifers having 5/8 Friesian blood tended to calve 3. 4.6 and 5 months earlier than 5/8 Friesian crosses FI and F2 respectively. Genetic group parity, district and the interaction between season and year of calving highly significantly (P<0.001) influenced CI. Cows in fourth parity out yielded those in first parity by 276 kg of milk. Year of calving and genetic group x district interaction were highly significant (P< 0.001) sources of variation in LMY. LL was significantly (P < 0.00l) influenced by genetic group, parity and year of calving. LL in Bukoba rural district was 28 days longer (P<0.05) than in Biharamulo district. It is concluded that both genetic and non-genetic factors considerably influenced reproduction and lactation performance of crossbred dairy cattle in Kagera region. Increased level of exotic blobd has led to having animals with shorter AFC and CI and higher LMY up to 5/8 Friesian blood. Genetic group by district interactions revealed that some genetic groups performed differently among districts reflecting differences in environmental effects between.
Reproductive and lactation performance of crossbred dairy cattle in Kagera region, Tanzania
(2002) Mwatawala, H.W.; Kifaro, G.C.; Petersen, P.H.
This study was done to evaluate reproductive and lactation performance of crossbred dairy cattle in Kagera region, Tanzania. Traits studied were age at first calving (AFC), calving internal (Cl), lactation milk yield (LMY) and lactation length (LL). Records for the various traits were compiled covering the period between 1979 and 1999. The General Linear Models procedure of SAS was used in data analyses. The mean AFC and CI were 39.0 months and 464. 7 days, respectively. The mean IMY and LL were 2332.5 kg and 367.2 days respectively. The influences of year of birth and genetic group on AFC were highly significant (P<0.001). Heifers having 5/8 Friesian blood tended to calve 3. 4.6 and 5 months earlier than 5/8 Friesian crosses FI and F2 respectively. Genetic group parity, district and the interaction between season and year of calving highly significantly (P<0.001) influenced CI. Cows in fourth parity out yielded those in first parity by 276 kg of milk. Year of calving and genetic group x district interaction were highly significant (P< 0.001) sources of variation in LMY. LL was significantly (P < 0.00l) influenced by genetic group, parity and year of calving. LL in Bukoba rural district was 28 days longer (P<0.05) than in Biharamulo district. It is concluded that both genetic and non-genetic factors considerably influenced reproduction and lactation performance of crossbred dairy cattle in Kagera region. Increased level of exotic blobd has led to having animals with shorter AFC and CI and higher LMY up to 5/8 Friesian blood. Genetic group by district interactions revealed that some genetic groups performed differently among districts reflecting differences in environmental effects between.