The effect of linseed supplementation on performance and concentration of fatty acids in subcutaneous adipose tissue and longissimus thoracis muscle in fattening lambs: A Meta-Analysis

Studies have shown that the addition of oilseeds to ruminants diets can affect the fatty acid composition of livestock products. linseed oil contains more than 70% poly unsaturated fatty acids with alpha-linolenic acid generally contributing over 50% of total fatty acids. Hence, protection against rumen biohydrogenation determine the amount of alpha-linolenic acid reach to the duodenum. The extrusion of linseed may protect unsaturated fatty acids against ruminal biohydrogenation. However, the effects of extrusion on ruminal degradability of linseed are inconsistent in the literature. meta-analysis can combine the results of studies about linseed supplementation to the fattening lamb diets for accurate and reliable estimation.

A literature search was initially conducted using PubMed, Medline, Science Direct, and Google Scholar data bases and investigated references in the papers. It was also based on the following key words: fatty acid, linseed supplementation, linseed oil, growth performance, and fattening lamb. Then 12 studies were included in this meta-analysis; and prepared comparisons for average daily gain, feed intake and hot carcass weight and concentration of n3, n6 and conjugated linoleic acid fatty acids in subcutaneous adipose tissue and longissimus thoracis muscle. Meta-analyses were carried out using the Comprehensive Meta-Analysis package, version 3. The effect sizes of across studies were calculated with fixed and random effect models. The presence of true heterogeneity among studies was identified with Cochran’s Q–tests and quantification of the degree of heterogeneity was done with the I2 index. Possible publication bias was evaluated with funnel plot and statistical tests.

The results of this meta-analysis showed that the addition of linseed in the diet, has a positive effects on average daily body weight gain and hot carcass weight. However, linseed supplementation had no significant effects feed intake. Addition of linseed in the diet increase n3 fatty acids content and decrease n6 fatty acids concentration in subcutaneous adipose tissue and longissimus thoracis muscle, respectively. Subcutaneous adipose tissue and longissimus thoracis muscle conjugated linoleic acid concentration were not influenced by linseed supplementation. Comparison of the effect size of type of supplements to the overall effect size for the amount of n3 and n6 fatty acids in subcutaneous adipose tissue and longissimus thoracis muscle showed that the addition of flaxseed oil had the most effect on the concentration of this fatty acids.

The results indicate that feeding linseed increase growth parameters such as lambs average daily body weight gain, hot carcass weight and n3 fatty acids content in subcutaneous adipose tissue and longissimus thoracis muscle in fattening lambs. Nevertheless, adding linseed to diets reduced n6 fatty acids content in subcutaneous adipose tissue and longissimus thoracis muscle of lamb.