The Interaction of Microalgae Dietary Inclusion and Forage-to-Concentrate Ratio on the Lipid Metabolism-Related Gene Expression in Subcutaneous Adipose Tissue of Dairy Goats

Long-chain polyunsaturated fatty acids (PUFAs) such as docosahexaenoic acid (DHA) have been shown to be effective in enhancing the quality of ruminant products, including meat and milk. However, under these dietary conditions, the de novo lipogenesis could be influenced, too. On the other hand, even if the forage-to-concentrate ratio (F:C) is also a key factor affecting lipid metabolism in small ruminants, there is scarce information about its interaction with dietary PUFA. This study investigates the potential of the F:C ratio as a lever to manipulate lipid metabolism in dairy goats under high dietary PUFA supplementation. For this purpose, twenty-two crossbred dairy goats [Alpine × Local (Greek) breeds] (BW = 50.6 ± 6.1 kg) at early lactation (70 ± 10 days in milk) during the age of 3-4 years old, were separated into two homogeneous subgroups (n = 11). In the first phase, each goat was fed 20 g <i>Schizochytrium</i> spp./day followed by either a high-forage (20 HF) or a high-grain (20 HG) diet, while in the second phase, each goat was fed 40 g <i>Schizochytrium</i> spp./day followed once again either a high-forage (40 HF) or a high-grain (40 HG) diet. The F:C ratio of a high-forage and high-grain diet was 60:40 and 40:60, respectively. Tail fat tissue samples were collected by biopsy on the 42nd day of each experimental phase (last day). Significant decreases (<i>p</i> < 0.05) in the gene expression of <i>ACACA</i>, <i>CBR2</i>, <i>COX4I1</i>, <i>ELOVL5</i>, <i>ELOVL7</i>, <i>LEP,</i> and <i>SCD</i> were presented in goats fed 40 g compared to those fed 20 g <i>Schizochytrium</i> spp., while the gene expression of <i>ACACA</i>, <i>AGPAT2</i>, <i>AGPAT3</i>, <i>ELOVL5</i>, <i>ELOVL6</i>, <i>EPHX2</i>, <i>FASN</i>, and <i>SCD</i> was decreased in high grain compared to high-forage diets. This study also indicated that with the aim to enrich goat products with PUFA by increasing their levels in the diet, lipid metabolism is negatively affected. However, a diet with higher forage inclusion can partially attenuate this condition.