The objective of this study was to determine the usefulness of some linear body measurements in predicting live weight in indigenous Tswana goats at various ages. Data for this study were obtained from 2,783 goats sampled from six agricultural regions of Botswana except for Tsabong and Ghanzi districts. Fifteen farmers keeping goats were randomly selected from each district and records taken on a random sample of 4-12 animals per farm depending on the 1999 Botswana Government average district flock size. Body measurements recorded were heart girth, height at withers, body length, shoulder width, and live weight. Information on age of each animal was estimated from dentition; flock size and sex of the animal were also recorded for each farm. Regression analysis using stepwise selection method in Statistical Analysis System was used to determine prediction equations for live weight with heart girth, height at withers, body length, and shoulder width as independent variables for male and female goats of different ages. In all models, heart girth contributed most in explaining variation in body weight as shown by high partial R(2) which ranged from 0.48 for female mature to 0.80 for mature male goats. Using mean square error, R(2), and Mallows' C(p), the best prediction equations were for female and male kids (R(2) = 0.83 and 0.82, respectively) and mature male goats (R(2) = 0.82). The poorest model was for mature female goats with R(2) = 0.57. Live body weight could be estimated with accuracy from linear body measurements in Tswana goats which are unique for each sex and age. More research is required to explore using these models to develop measuring tapes for use by resource poor farmers who keep indigenous Tswana goats.

A modified form of restricted, recurrent phenotypic selection was used to select for seedling shoot weight in switchgrass (Panicum virgatum L.), big bluestem (Andropogon gerardii Vitman), and indiangrass [Sorghastrum nutans (L.) Nash] populations for three generations. Seedlings were grown in micropots in trays in a greenhouse and were individually clipped and weighed 4 wk after emergence. The seedlings were allowed to regrow, and the heaviest seedlings were transplanted to field nurseries for polycrossing to produce Syn 1 seed. Three breeding cycles were conducted for each grass. After the third breeding cycle, Syn 2 generation seed was produced for each cycle, including cycle 0 for 2 yr, and was used in subsequent greenhouse and field evaluations to determine if the breeding procedure improved seedling vigor as measured by seedling shoot weight. In two greenhouse evaluation trials, the increase in seedling weight per cycle was 7.8, 5.6, and 10.2% for big bluestem, switchgrass, and indiangrass, respectively. In two field trials, seedling weight also increased with successive cycles of selection except for indiangrass in one trial. Establishment success as measured by stand counts did not differ among the cycles of selection for the three grasses in the field trials. Based on these results and the results of subsequent breeding and field evaluation work on seedling tiller number, it is apparent that seedling traits of these grasses can be modified by breeding. To improve establishment of these grasses, research on developing agronomic seed production practices that result in improved seed quality would also be beneficial.

A study was carried out in forest reserves located in Chobe district in Botswana to assess the effect of dieback and associated causes on Mukwa tree, Pterocarpus angolensis Fire, elephant damage and dieback were assessed in Chobe and Kazuma forest reserves and Pandamatenga farming area. Fire damage frequency on mukwa trees ranged between 60 to 100 % and was highest in Pandamatenga and Chobe forest reserves. The frequency of elephant damage in Kazuma and Chobe forest reserves was 75 and 100 % respectively. There was no elephant damage in Pandamatenga farms because the area is fenced out and minor dieback occurred in the area. All areas under study experienced 100 % incidence of dieback, but the severity ranged from 22 to 100 %, the highest being at Chobe forest reserve and the lowest at Pandamatenga. Severity of dieback was associated with elephant damage and age of P. angolensis trees. The incidence of dieback was correlated with DBH and tree age. The results indicate that the cause of dieback is mostly due to elephant and fire damage.

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