Predicting body fat depots in Katahdin sheep using ultrasound kidney fat thickness measurements

Abstract

The present study aimed to predict the amount and energy content of body fat depots in Katahdin sheep using ultrasound measurements of kidney fat thickness (uKFT). Twenty-four h before slaughter, the uKFT was measured behind the 13th rib on the right side of 34 animals. After slaughter, data were collected on both carcass and non-carcass components. Internal fat depots were dissected, weighed, and classified as mesenteric (MF), omental (OM), or perirenal (PF) fat and then summed to give the total internal fat (IF) weight. Carcass fat (CF: subcutaneous plus intermuscular fat), muscle, and bone weights were then obtained by manual deboning of the left half of the carcass. Total body fat (TBF) was the sum of IF and CF. Finally, the gross energy content (GE) of IF, CF, and TBF was calculated. The uKFT was moderately to highly associated with internal body fat depots (0.63 ≤ r ≤ 0.83, P < 0.001). In addition, r was 0.76 to 0.86 for IF and CF and had a similar range for GEIF, GECF, and GETBF. To predict internal body fat depots, the equations had an r2 ranging from 0.43 to 0.76, and in these models, the uKFT and empty body weight (EBW) were included (P < 0.05). The equations for IF, CF, GEIF, GECF, and GETBF had an r2 ranging from 0.54 to 0.78. The evaluation showed that the equations had low to moderate precision (> 0.44 ≤ and ≤ 0.78), moderate to high accuracy (> 0.75 ≤ and ≤ 0.99), and moderate to high reproducibility index (> 0.61 and ≤ 0.88). The results indicate that the equations developed from ultrasonic measurements of kidney fat thickness can be used to predict the amount and energy content of body fat depots in Katahdin sheep with moderate accuracy and precision. It also appears that Katahdin sheep store a significant proportion of absorbed energy in the carcass rather than in internal depots.