Abstract
With this trial we have tested the effects of structural and chemical composition of neutral detergent fibre (NDF) of the diet on lamb fatty acid composition of meat and subcutaneous fat. Twenty lambs, were fed complete diets with low starch and similar NDF content of different origin (ground alfalfa or soybean hulls). Animal performance and product quality were not affected by treatments. Rumen pH increased and parakeratosis intensity decreased with the level of alfalfa in the diet. Increasing the alfalfa proportion in the diet decreased t10–18:1 (P = .023), increased t11–18:1 (P = .003) and decreased the t10/t11 ratio according to a quadratic pattern (P = .020). Chemical composition and structure of the diet's fibrous fraction influenced the BI pattern of the final product. Forty percent of alfalfa in diet reduced the severity of t10-shift, but for its full resolution, other factors should be considered including forage particle size and buffering capacity of the diet.
Highlights
Rumen biohydrogenation (BH) is a set of biochemical processes by which dietary unsaturated fatty acids (FA), mainly oleic (c9–18:1), linoleic (18:2 n-6) and linolenic acids (18:3 n-3), are isomerised, hydrogenated and converted to stearic acid (18:0) by rumen microbiota
In groups fed with MA and LA diets there were no lambs with level 3 lesions, 29% and 3% presented moderate lesions, 57% and 33% presented weak lesions and 14% and 33% showed normal rumen wall, respectively
The results presented here confirm that hypothesis as replacing soybean hulls neutral detergent fibre (NDF) by alfalfa NDF in isoNDF diets led to a linear decrease of t10–18:1 and t10,c12–18:2 (Alves & Bessa, 2014; Bravo-Lamas, Barron, Kramer, Etaio, & Aldai, 2016) and to a linear increase in t11–18:1 and c9,t11–18:2
Summary
Rumen biohydrogenation (BH) is a set of biochemical processes by which dietary unsaturated fatty acids (FA), mainly oleic (c9–18:1), linoleic (18:2 n-6) and linolenic acids (18:3 n-3), are isomerised, hydrogenated and converted to stearic acid (18:0) by rumen microbiota. When fed with high-forage diets the main biohydrogenation intermediates (BI) deposited in their tissues are vaccenic (t11–18:1) and rumenic (c9,t11–18:2) acids (Bessa, Alves, & SantosSilva, 2015) Both t11–18:1 and c9,t11–18:2 are considered healthy FA and nutritional strategies to enrich them in ruminant products have been extensively researched (Mapiye et al, 2015; Scollan et al, 2014). To t11–18:1 and c9,t11–18:2, the t10–18:1 might exert deleterious health effect in the consumers (Chikwanha, Vahmani, Muchenje, Dugan, & Mapiye, 2018; Hodgson, Wahlqvist, Boxall, & Balazs, 1996) The occurrence of this shift of the BH pathways, hereafter t10-shift, has been associated with low milk fat syndrome in dairy cows (Griinari & Bauman, 2001). The causes of t10-shift are not known, but in the presence of high polyunsaturated FA (PUFA) concentration, the t10-shift is associated to high dietary starch (Maia, Bessa, & Wallace, 2009; Zened, Enjalbert, Nicot, & Troegeler-Meynadier, 2013) and low rumen pH (Choi et al, 2005)
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