The effect of neutral detergent fibre source on lambs growth performance and meat nutritional value
J. Santos-Silva 1, A. Francisco 1, T. Dentinho 1, J. Almeida 1, A. Portugal 1, S. Alves 2, E. Jerónimo 3 and R. Bessa2
1 INIAV, Fonte Boa, 2005-048 Vale de Santarém, Portugal,
2 Faculdade de Medicina Veterinária, U. Lisboa, Av. Universidade Técnica, 1300-477 Lisboa, Portugal,
3 CEBAL, R. Pedro Soares, 7800-295 Beja, Portugal;
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The objective of this study was to evaluate the effect of changing the source of neutral detergent fibre (NDF) in complete ground diets on lambs growth, carcass quality and meat nutritional value. Twenty lambs were individually housed and assigned to 3 diets with low starch (5.6% DM), high oil (7.5% DM) and the same NDF content (42.9%DM) but differing in NDF composition. The main NDF source was dehydrated pelleted alfalfa (Medicago sativa) with levels of 200, 400 and 600 g/kg DM, that were balanced with the proportions of soyhulls (Glicine max), and dehydrated citrus and beat pulps. The experiment lasted 6 weeks. Intake was controlled daily and lambs weight weekly. After slaughter, carcass quality parameters were determined and Longissimus dorsis (LD) muscle was sampled for chemical and physical analysis. Intake increased (P<0.05) with alfalfa proportion in the diet but growth rate was unaffected (290 g/day). Carcass traits and LD and fat colour, (L*,a*, b*), were not changed by the diet. Meat shear force measured 7 days after slaughter presented low values (2.75 kg/cm2) and diets did not affect the LD colour stability and lipid oxidation during storage. The composition of NDF affected rumen biohydrogenation (BH) pattern and the proportion of some bioactive fatty acids in meat. Increasing the forage proportion in diets increased the main healthy BH intermediates vaccenic (t11-18:1; P=0.003) and rumenic acids (c9,t11-18:2; P=0.021) and decreased the proportion of t10-18:1 (P=0.058) and t10,c12-18:2 (P=0.007). Moreover, increasing alfalfa proportion in diets reduced the frequency and intensity of the t10 shift, as evaluated by t10-/t11-18:1 ratio in the tissues. Concluding, the NDF source is a determinant factor on the results of the feeding strategies designed to improve the nutritional value of lamb meat.