In order to assess the applicability of bovine microsatellite markers for population genetic studies in Swiss yak, 131 bovine microsatellite markers were tested on a panel of 10 animals. Efficient amplification was observed for 124 markers (94.6%) with a total of 476 alleles, of which 117 markers (94.3%) were polymorphic. The number of alleles per locus among the polymorphic markers ranged from two to nine. Seven loci (ILSTS005, BMS424B, BMS1825, BMS672, BM1314, ETH123 and BM6017) failed to amplify yak genomic DNA. Two cattle Y-chromosome specific microsatellite markers (INRA126 and BM861) amplified genomic DNA from both male and female yaks. However, two additional markers on cattle Y-chromosome (INRA124 and INRA189) amplified DNA from only males. Of the polymorphic markers, 24 microsatellites proposed by CaDBase for within- and cross-species comparisons and two additional highly polymorphic markers (MHCII and TGLA73) were used to investigate the genetic variability and the population structure of a Swiss yak herd that included 51 additional animals. The polymorphic information content ranged from 0.355 to 0.752, while observed heterozygosity (HO) ranged from 0.348 to 0.823. Furthermore, a set of 13 markers, organized into three multiplex polymerase chain reactions, was evaluated for routine parentage testing. This set provided an exclusion probability in a family of four yaks (both parents and two offspring) of 0.995. These microsatellites serve as useful tools for genetic characterization of the yak, which continues to be an important domestic livestock species.

Few studies have been conducted in sub-Saharan Africa where multiple recordings of heart girth and body weight were made for the same cattle population. In this study, monthly measurements were taken of working oxen on 24 smallholder farms in the Ethiopian highlands for 1 year. The overall yearly mean body weight of oxen across working and nonworking periods was 281637 kg. No significant differences in mean monthly body weights were observed, except for December and January compared to August (297636 and 296637, and 271635 kg, respectively, P , 0.05) and December versus April 272635 kg (P , 0.05). Simple linear regression equations derived from body weight and heart girth measurements were significantly different between months. Nevertheless, separate monthly equations and a single equation for the year explained variation in body weight about the same. The monthly equations predicted 83 to 95% of oxen weights to within 610% of 2 weighbridge values, while the equation for the entire year predicted 87%. The R values for the monthly equations ranged 2 from 0.63 to 0.87 and the R value for the entire year was 0.75. The single equation for the year predicted body weight of oxen as a group to within 627 kg of mean monthly weighbridge values, whereas for a single animal the predicted body weight was 637 kg of the actual weight (C.I. 95%). The single equation can be used to monitor mean body weight of the oxen population equally well across working and nonworking periods of the year.

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