Effects of feeding system and nitrogen source on lamb growth, meat characteristics and fatty acid composition N. Atti a, * , M. Mahouachi b a INRA-Tunisie, Laboratoire de Productions Animales et Fourragères, rue Hédi Karray, 2080 Ariana, Tunisia b Ecole Supérieure d’Agriculture du Kef, Le Kef, Tunisia article info Article history: Received 4 October 2006 Received in revised form 20 July 2008 Accepted 24 August 2008 Keywords: Sheep Dry pasture Stall Soya Faba bean Carcass characteristics Fatty acids abstract For this study, 28 lambs were allocated to four groups: two groups were raised in stalls and fed a hay- concentrate ration. The two remaining groups were reared on dry pasture and received concentrate in stalls. In each feeding system, two iso-nitrogen concentrates were used, soya bean and soya plus faba bean. At the end of the growth trial (77 days), all lambs were slaughtered. Samples of longissimus dorsi muscle were used for muscle analysis and fatty acid (FA) composition determination. Average daily gain (134 g) was similar for all treatments. Stall lambs deposited significantly (p < 0.001) more fat per day (13 vs 5 g) and slightly more muscle (41 vs 35 g) than pasture grazing ones; the first had more fat tissue (5.2 kg) than the later (4.6 kg). All these parameters were not influenced by nitrogen source. FA profile and meat characteristics were similar for all dietary treatments. It could be concluded that dry pasture did not affect meat quality but lead to the leaner lambs. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction Meat from lambs raised on pastures is often considered to be of superior quality to that of stall raised lambs (Atti & Abdouli, 2001; Murphy, Loerch, McClure, & Solomon, 1994; Popova, 2007; Ådnøy et al., 2004). Meat of lambs reared on pasture contained less total lipid and triacy-glycerol than that of lambs fed a concentrate based diet (Aurousseau, Bauchart, Calichon, Micol, & Priolo, 2004; Engle & Spears, 2004; Popova, 2007; Rowe, Macedo, Visentainer, Sousa, & Matsushita, 1999). When compared to grain feeding, pasture in- creases the nÀ3 PUFA content and decreases C18:2nÀ6/ C18:3nÀ3 ratio (Nuernberg et al., 2005; Aurousseau et al., 2004; Popova, 2007). On the other hand, in arid and semi-arid areas, natural pasture supply is too poor, particularly in summer, to meet the nutritional requirements of growing lambs. Furthermore, oat hay which is the main forage used indoors, has a low nutritive value (INRA, 1978; Nefzaoui & Chermiti, 1989). Thus, the supplementation of these feedstuffs becomes necessary to increase lamb growth rate. Soya bean is the most common nitrogen source included in the concen- trate. It is important to find alternative sources in the aim to re- place soya bean in the ruminant diets. Legumes seeds, such as faba beans, lupins and peas, have attracted attention as supple- ments for ruminants in recent years. Indeed, faba bean has a high protein (30%) and starch (42%) content (Yu, Goelema, Leury, Tamminga, & Egan, 2002) and is a potentially valuable protein and energy supplements for animals. Thus, the objective of this study was to compare the effect of rearing system (indoors vs pasture) and nitrogen source (soya bean vs faba bean) on growth, tissue composition, meat quality and fatty acid composition of fat-tailed lambs. 2. Material and methods 2.1. Experimental design The experiment was carried out at the National Institute of Agricultural Research of Tunisia (INRAT). The experiment started in mid May with a total of 28 fat-tailed Barbarine male lambs trea- ted against internal and external parasites and entero-toxemia. They were 6 months old and had an average body weight (BW) of 36.4 ± 1.9 kg. They were divided into four equal groups accord- ing to live weight, and calculated muscle and fat weights (Table 1). Two groups were raised in stalls (S) and fed in individual boxes a ration based on oat hay and concentrate. The concentrate amount (800 g per head) and the hay to concentrate ratio (40:60) were fixed as in smallholder practice. So, the hay was offered at 90% of ad libitum intake. Distributed quantities were calculated on a dry matter (DM) basis as 37 g/kg BW (15 and 22 g/kg BW of oat hay 0309-1740/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.meatsci.2008.08.011 * Corresponding author. Tel.: +216 1 230024; fax: +216 1 752897. E-mail address: belhaj.naziha@iresa.agrinet.tn (N. Atti). Meat Science 81 (2009) 344–348 Contents lists available at ScienceDirect Meat Science journal homepage: www.elsevier.com/locate/meatsci