Discipline: Veterinary Medicine
A total of 84 (41 males and 43 females) apparently healthy Philippine-born Thoroughbred horses two to 11 yrs old were weighed using a digital weighing scale and their external body measurements (height; heart girth; umbilical girth; body length 1=distance from point of shoulder to tuber ischium; and body length 2= distance from tuber ischium to olecranon) taken using a tailor 's tape measure to develop a method of weight determination based on the above external body parameters. Correlation analysis revealed a linear relationship between the external body measurements with the actual body weights of horses. Heart girth, as compared to the other external body measurements, has the strongest positive linear relationship with body weight (r=0.803), while body length 2 proved to be the least correlated (r =0. 149). Heart girth was found to be the best single predictor of body weight for the male (r 2=0.635), female (r2= 0. 714), and t he combined population groups (r 2=0.64). On the other hand, measuring the heart girth and umbilical girth increases the accuracy of weight determination in these animals to as much as 10% (r2= 0. 739). Multiple regression analysis revealed that the horses' height and body length 1 are also significant (P<0.05) together with the first two body parameters to predict the weight of horses, but only limited to the female group. Nevertheless, the predicting equation derived through dual regression analysis regardless of sex: CY= -528.096 + 3.101HG + 2.266UG) is the best practical predicting equation for body weights of Philippine-born Thoroughbred horses. Thus, in the absence of a weighing scale, this new formula is fairly suitable for obtaining· the body weights of Philippine-born Thoroughbred horses.