Context
In response to the nutritional imbalances prevalent in the West, specifically excessive consumption of saturated fats and too high an n-6/n-3 polyunsaturated fatty acid (FA) ratio, various research projects are under way in an attempt to improve the fat composition of animal products. Against this background, grazing and linseed supplementation offer a natural way to achieve this objective. These feeding methods take account of consumer expectations and thus present an opportunity for the agricultural sector.Objectives
The first two trials have been conducted to investigate the effects of extruded linseed supplementation of ewe and lamb rations on production performance and the fatty acid composition of the meat from lambs reared under the two systems (sheepfold and pasture). A third trial was carried out to study the effet of linseed (whole, crushed or extruded forms) on rapeseed cake supplements on meat fatty acid composition of sheepfold lambs.Results obtained
In the “sheepfold” trial, no significant differences were found in lamb growth performance or carcass yield according to the type of rearing method (Table 1). However, the lambs supplemented with linseed apparently achieved lower growth (-12% approximately) than the lambs without the linseed supplement. In the “pasture” trial, lambs finished on grass recorded significantly lower growth than the lambs finished indoors, with or without linseed, and had a later slaughter date with a lower carcass yield (Table 1). The feeding system for the ewes and lambs had no effect on the dry matter and fat content of the meat (Table 2). In the case of “sheepfold” lambs, adding linseed (15% of the diet) to their feed significantly increases the C18:3 n-3 content (+130%) and the CLA content (+20%) while reducing C16:0 (-5%), C18:1 cis (-5%) and the n 6/n 3 ratio (-61%) (Table 2). In the case of “pasture” lambs, finishing on grass (H), compared to indoor finishing with (L) (12.5% of the diet) or without (T) linseed supplement has the effect of increasing the C12:0 content (+63 and 68% respectively), C18:0 (+26 and 21%) and SFA (+8 and 4%) and reducing the C16:0 content (-8 and 11%), C18:2 cis (-33 and 25%) and total monounsaturateds – MUFAs – (-5 and 6%) (Table 2). The higher proportion of SFA in grazing lambs is essentially attributed to the significant rise in C18:0. Lambs finished on grass or indoors with linseed are distinguished from those without linseed supplement by a greater proportion of C18:3 n-3 (+ 103 and 117% respectively), a lower proportion of C18:1 cis (–10 and 8%) and a lower n 6/n 3 ratio (-60 and 52%). With regard to CLA, the highest proportions were found among the lambs finished on grass. Lambs finished in housing showed higher C18:1 trans (+108%) and PUFA (+21%) levels with the linseed supplement. In accordance with the literature, our research confirms that the feeding method for lambs before and after weaning can, in certain conditions, significantly affect the fat composition of the meat. Feeding lambs supplementary linseed, which is rich in C18:3 n-3, raises the proportions of that fatty acid and CLA. Similarly, the high proportion of C18:3 n-3 in lambs finished on grass may be attributed to a substantial supply of PUFAs (chiefly C18:3 n-3) from the grass. Grazing also significantly increases the CLA content. The milk feeding of the lamb also affects the meat fat composition. The closer the date of slaughter to weaning, the more marked is this effect. This may account for the beneficial effect of feeding suckling ewes a linseed supplement on the fatty acid pattern of meat from housed lambs. Apart from diet, the sex of the lambs also apparently affects the dietetic quality of the meat FA, with housed male lambs having higher proportions of CLA than females. However, this gender effect is not apparent in the CLA content of meat from grazing animals. For the third trial, no changes of the intramuscular lipids content, nor proportions of saturated, mono and poly-unsaturates fatty acids were observed between diets. Compared to the control and rapeseed diets, the contribution of linseed, whatever its form, generated a significant higher alpha-linoleic acid content (+60%). The trial did not show any difference for the criteria age (97 days) and weight at slaughtering (37 kg), weight of carcass (18 kg) and carcass yield (48%), state of fattening (average note of 2,8 according to OFIVAL grid) and quality of fat (color and visual aspect of dorsal fat). This absence of difference (zootechnical data and FA profile) between the three diets with linseed (whole, flattened and extruded) seem to indicate that the lambs have an equivalent aptitude to metabolize seed in the various forms tested Our research therefore appears to indicate that where adequate grass is not available for finishing lambs, using extruded linseed can give the meat a fatty acid pattern of similar quality. Moreover, the use of whole linseed seems to confer same nutritional meat qualities as the extruded form. Although it’s not possible to reach a similar FA profile to that obtained with the linseed, rapeseed cake appears however more interesting from an economic point of view.Contribution
CRA-W
Partners
Catholic University of Louvain MR-W, Department of Development and ExtensionCRAW off coordinator
BARTIAUX-THILL Nicole (Inspecteur général scientifique) Rue de Liroux, 8 B-5030 Gembloux Téléphone direct :62 67 71 Téléphone département :+ 32 (0) 81/61.27.39 - 61.27.40 Fax département :+ 32 (0) 81/61.58.68 E-mail :bartiaux@cra.wallonie.beFunding
- CRA-W - Walloon Agricultural Research Centre
