Abstract
ABSTRACTWe investigated the prediction of live weight (LW) of dairy cattle in low- to medium-input systems in Senegal, based on measurements of heart girth (HG) and height at the withers (HW). A total of 459 female dairy cattle, mainly comprising indigenous Zebu and their crosses with Guzerat or Bos Taurus, were weighed (kg), and their HG (cm) and HW (cm) determined. Farmers were asked to provide their own weight estimates for each animal. The single explanatory variable that explained the most variation in LW was HG. The best model to predict LW from HG for the overall data was with an adjusted R2 of 0.85 and a root mean square error of 34.25 kg corresponding to 11.10% of the mean LW. This model predicted the LW of 91–100% of cows and 64–100% of heifers within 20% of their true-live weight, in the weight range of about 100–500 kg. In comparison, farmers could only estimate the LW of about a quarter of their animals within 20% of their true LW. This weight prediction equation, when translated into a weigh band, could provide a simple and reliable method for cattle keepers to estimate the weight of studied cattle breed types.
Highlights
The accurate estimation of body weight of livestock is important in deciding the slaughter weight, feeding level and what treatment dose to use (Ulutas et al 2002; Machila et al 2008)
In most rural areas of Africa, cattle are rarely weighed as weighing instruments are costly to obtain, need technical maintenance and are difficult to transport to livestock farms, especially in pastoral and agro-pastoral systems (Machila et al 2008)
Body weight is closely related to body measurements, with heart girth (HG) generally accepted as the most satisfactory single predictor of live weight (LW) in cattle (Fall et al 1982; Dodo et al 2001; Yan et al 2009; Isik et al 2009; Lesosky et al 2012; Lukuyu et al 2016)
Summary
The accurate estimation of body weight of livestock is important in deciding the slaughter weight, feeding level and what treatment dose to use (Ulutas et al 2002; Machila et al 2008). Farmers and cattle traders often rely on visual judgement to determine the live weight (LW) of animals, which is a subjective method whose accuracy depends on users’ experience. The method is cheap, accurate and consistent; many predictive regression equations are based on this parameter alone or in combination with others. Whilst such studies have been carried out in Senegal – the focal country of this study – in the past (Chollou et al 1978; Fall et al 1982; Buldgen et al 1984), they are more than 30 years old and may not be valid for the new cross and pure cattle breed types that are emerging in Senegal, primarily through the use of exotic breed types via artificial insemination
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