Comparison of growth curves of lamb fat tail measurements and their relationship with body weight in Babarine sheep

A total of 695 fat-tailed Barbarine lambs born in two flocks between 1995 and 1997 were recorded for growth and fat tail measurements according to “standard growth recording protocol”. Recorded traits are body weight (BW) and the following fat tail characteristics: upper circumference (UFTC), lower circumference (LFTC), upper width (UFTW), lower width (LFTW), upper depth (UFTD), lower depth (LFTD) and tail length (FTL). Lamb body growth performance and tail measurements are analyzed from two points of view. Firstly through the adjustment of a growth curve chosen among the following: Brody, Logistic, Gompertz and Bertalanffy functions. Secondly, age-adjusted weight and tail measurements (10, 30 and 70 days) were analyzed and average daily gains (ADG) were calculated. All functions (Brody, Logistic, Gompertz and Bertalanffy) fitted closely body weight and fat tail measurements of Barbarine lambs for the recording period (up to 120 days), while the Bertalanffy function provided more accurate estimation of the asymptotic value (adult size) for the weight and tail measurements. High significant correlations (p < 0.01) were obtained between body weight and tail measurements. However, the LFTW-ADG had the highest correlation with BW performance, and was therefore the best indicator of the state of lamb fattening. Furthermore, the LFTW-ADG recorded between 10 and 30 days of age has a higher correlation with lamb BW performance at later age (30–70 days) than those recorded at the same period (between 10 and 30 days), indicating that lambs with higher fat storage during the suckling period express better performance at later ages. Therefore, this study confirms the role of the tail fat as an adaptive character of the Barbarine breed and most likely of other fat-tailed sheep breeds.