Incorporation of by-products of rosemary and thyme in the diet of ewes: effect on the fatty acid profile of lamb
2013
Nieto Martínez, Gema
The present study measured changes in fatty acid composition of lamb meat from sheep fed plant by-products (rosemary- and thyme-distilled leaves) during pregnancy and lactation. For that, thirty-six pregnant Segureña ewes were employed per experiment (2 experiments in total: A with distilled rosemary leaf—DRL—and B with distilled thyme leaf—DTL) and were randomly assigned into three homogeneous groups. Sheep in the control group (C R: control DRL experiment; C T: control DTL experiment) were given a basal diet (BD). The experimental diets of the other two groups were modified by substituting 10 and 20 % of the BD by DRL (R ₁, R ₂) in experiment A and with 10 and 20 % of the BD by DTL (T ₁, T ₂) in experiment B. Moisture, fat, protein content, fatty acid profile, and pH of the fresh lamb meat were analysed. Pearson’s correlations were made between fatty acid profile and rancid odour (RO), TBARS of fresh lamb meat at day 21 of storage. The incorporation of thyme- and rosemary-distilled leaves in the diet of pregnant and lactating ewes caused a significant increase (P < 0.05) in the levels of polyunsaturated fatty acid (PUFA), unsaturated fatty acids (UFA), and a significant decrease in the percentage of saturated fatty acid (SFA) saturation index (S/P), atherogenic (AI), and thrombogenic (TI) indices in lamb meat. In general, this effect was more pronounced with a diet of 20 % DRL. High positive correlations were found between rancid odour and SFA (except C ₁₈:₀ and C ₂₀:₀) and monounsaturated fat (MUFA); on the contrary, a negative correlation was shown between PUFA content and RO, TBARS. Thus, adding by-products of rosemary and thyme to the diet of ewes significantly improved fatty acid profile of lamb meat.
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