[Predictive value of back fat thickness for body fat content in cattle]

Back fat thickness was measured at six points in 251 beef heifers aged 3 to 17 months, in 27 beef bulls aged 15 months and in 200 SMR-cows of different age. This was paralleled by estimation of body composition based on total body water analysis. All groups of animals showed the same pattern of back fat thickness for the measuring points investigated. This lead to the result of one optimum measuring point for determination of back fat thickness, which will be described. The portion of body fat relative to body weight change showed great variations in dependence on age. Therefore live weight is of limited relevance for the estimation of body condition. The correlation coefficients between back fat thickness and body fat content were estimated to be between 0.80 and 0.87 for all groups investigated. Change in back fat thickness by 1 mm corresponded to gain or loss of around 5 kg body fat in all animal groups. Hence, measurement of back fat thickness is a suitable method for objective estimation of body condition.