Relationship between plasma leptin concentrations and carcass composition in fattening mutton: a comparison with ultrasound results

Abstract

Positive relationships between circulating leptin concentrations and body fat content have been established in sheep when covering a rather broad range of age and/or body weight. The usefulness of leptin measurements for predicting carcass fat has yet to be evaluated specifically in fattening lambs. We therefore measured plasma leptin concentrations in 56 male lambs half and half Merino Mutton and Blackheaded Mutton. Subcutaneous fat thickness was measured by ultrasound 1 day before the lambs were slaughtered at 35 or 45 kg live weight. Carcass composition was determined by tissue dissection. The coefficients of correlations between leptin and the different amounts in fat depots ranged from 0.40 to 0.56 within the two live weight groups, and from 0.53 to 0.64 when taking the two groups together. Carcass fat percentage was estimated by leptin concentrations with the same accuracy (R2 = 0.34) as with ultrasound fat thickness. The accuracy was higher for leptin in the 35 kg-group whereas the accuracy was higher for ultrasound fat thickness in the 45 kg-group (R2 = 0.26 vs. 0.31). A combination of leptin and ultrasound fat thickness clearly enhanced the precision of estimation in all groups. Further investigations on the influence of factors such as breed, gender, duration of feed withdrawal or photoperiod on the association between leptin and carcass composition are necessary before the suitability of plasma leptin concentration for practical application can be evaluated.

The usefulness of leptin measurements and ultrasound fat thickness for assessment of body fat reserves of Awassi lambs

“…Additionally, in the present study, leptin level increase was approximately 30% (no data info) until 40 kg but Altmann et al (2006) reported that leptin increase was more than 30% between 30-35 kg BW, also Radwanska and Kosior-Korzecka (2016) Orman et al (2008Orman et al ( , 2010 UFT was increased with the increase of live weight of Awassi lambs. Also, a similar result was reported by Altmann et al (2005) for different breeds (East Frisian and Blackheaded Mutton  East Frisian crosses). On the other hand, Kuznicka et al (2017) reported that fat thickness over the eye loin did not change with live weight in merino male lambs.…”

“…For instance, Ehrhardt et al (2000) reported the value for the same parameter to be 0.91 (p < .05) in Holstein bull cows, whereas Yamada et al (2003) reported the values changing between negative (not significant) and 0.81 (p < .05) in different BW Japanese Black  Holstein cross breed steers. Also, in male lambs, the various correlation coefficients were reported by Altmann et al (2005Altmann et al ( , 2006 as 0.51, 0.49 and 0.48 (p < .05) for 35, 40 and 45 kg BW. A similar correlation coefficient was reported by Delavaud et al (2000) as 0.68 (p < .05) for Lacaune ewes.…”

“…Altmann et al (2005) reported the value for the same parameter to be 0.17 and 0.15 (p > .05) Figure 1. Correlation coefficients (r) between leptin levels and body weight (BW), ultrasound fat thickness (UFT) and fat tissues at different BW.…”

“…Ultrasound fat thickness (UFT) measurements were similar to the accuracy for the estimation of carcase fat by serum leptin concentrations at slaughter time in lambs (Altmann et al 2005). On the other hand, the relationship between serum leptin concentrations in early life and carcase characteristics are poorly found out in lambs (Altmann et al 2005(Altmann et al , 2006.…”

Selected hormonal and neurotransmitter mechanisms regulating feed intake in sheep

“…In ruminants, leptin gene expression and immunohistochemistry indicate that leptin is synthesized by the fat cell (Dyer et al, 1997;Kumar et al, 1998;Daniel et al, 2003). Circulating leptin concentrations are episodic in nature and are increased by obesity and decreased by fasting, though there were no apparent photoperiod effects on plasma leptin concentrations (Kumar et al, 1998;Marie et al, 2001;Daniel et al, 2002;Ehrhardt et al, 2003;Altmann et al, 2005;Chilliard et al, 2005;Delavaud et al, 2007). Feeding high fat or carbohydrate meals resulted in increased plasma leptin concentrations (Yildiz et al, 2003) suggesting that higher energy content rather than the source of energy was important.…”