The estimation of live weight based on linear traits in indigenous Tswana goats at various ages in Botswana

Abstract

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.

Using path analysis to predict bodyweight from body measurements of goats and sheep of communal rangelands in Botswana

“…In Botswana, goats and sheep are usually slaughtered for social events, such as weddings, funerals, and traditional ceremonies, or sold to local butcheries and abattoirs. Marketing and sale prices of livestock in rural areas for these activities are primarily dependent on the live weight of the animal (Sebolai et al, 2012;Norris et al, 2015). When smallholder farmers have little experience with weight scales, their ability to estimate animal weight 'by eye' is likely to be relatively limited, and may result in incorrect weight being utilized to determine sale price (Sebolai et al, 2012).…”

“…Marketing and sale prices of livestock in rural areas for these activities are primarily dependent on the live weight of the animal (Sebolai et al, 2012;Norris et al, 2015). When smallholder farmers have little experience with weight scales, their ability to estimate animal weight 'by eye' is likely to be relatively limited, and may result in incorrect weight being utilized to determine sale price (Sebolai et al, 2012). Having some knowledge of the weight and growth rates of goats and sheep is therefore vital information for smallholder farmers in making livestock management decisions and evaluating alternative strategies (ESGPIP, 2009).…”

“…In arid grazing systems, BW measurements could provide a monitoring tool for assessing animal performance when pasture cover is monitored on grazing land, especially in communal systems. There is potential to address these issues by developing simple and reasonably accurate methods for estimating the BW of goats and sheep, using prediction equations based on linear body measurements that have been obtained with a metric tape rule (Worman et al, 1980;Sebolai et al, 2012).…”

“…The interrelationships between linear body dimensions and BW of goats and sheep in Botswana have been investigated (Owen et al, 1977;Worman et al, 1990;Nsoso et al, 2003;Sebolai et al, 2012). Owen et al (1977) used linear regression models to estimate the relationship between live weight and HG for castrated indigenous goats and sheep in southern Botswana.…”

“…They concluded that BCS was the most useful of these indicators in identifying seasonal nutritional defects in goats. In a more recent study, Sebolai et al (2012) applied a multiple regression model to estimate the relationship between live weight and linear traits in indigenous goats at various ages, identifying a significant increase in BW and linear associations relating to older animals.…”