Sustainable utilization of unsaleable walnut kernel in substitution for corn grain in the diet of fattening lambs improves growth performance and meat quality.

As a cost-effective typical co-product of walnut processing; this study aimed to investigate the effects of feeding poor quality, unsaleable walnut kernel, also known as wasted walnut (WW) kernel, on growth performance, carcass characteristics, meat quality and fatty acid (FA) composition of fattening lambs. The experiment was conducted using 24 fattening lambs (27 ±1.07 kg initial BW) assigned to two total mixed concentrate-based diets, over a 80-day experimental period on a completely randomized design. Dietary treatments were: 1) WW (10% WW), and 2) CON (without WW). Average daily and total gain, and final weight increased with WW inclusion (P < 0.05). Also, a significant enhancement in feed conversion ratio (P < 0.05) and carcass cooler shrink loss (P = 0.03) were observed by feeding WW. Dry matter intake (DMI) was not influenced by feeding WW as did carcass prime cuts, meat, bone and fat-tail; however, the backfat thickness was increased (P = 0.01). WW inclusion reduced cholesterol and increased protein load in muscle tissue (P ≤ 0.05). Moreover, this inclusion led to higher concentration of vaccenic acid (VA), conjugated linoleic acid (CLA) and C20 polyunsaturated FAs (PUFA), total n3 and n6 PUFA in muscle and fat-tail (P ≤ 0.05). Due to enhanced animal performance, also chemical and FA composition of muscle and adipose tissue, WW can be included in fattening lamb diets as a rich source of protein and PUFA.