Effect of plant oil addition to dairy goat diet on milk fat contents of trans-9 C16:1 and C16:2

Resumen del trabajo presentado al 22nd Congress of Animal Science and Production Association, celebrado en Perugia (Italia) del 13 al 16 de junio de 2017.

Milk fat has a great variety of fatty acids derived from ruminal and mammary gland metabolism. Some milk fatty acids are quantitatively minor, but might be relevant from the human health point of view. The aim of the present study was to contribute to the knowledge of changes in the contents of trans-9 C16:1 and C16:2 when differently unsaturated plant oils are fed to dairy goats. Trans-9 C16:1 has recently been attributed positive effects on insulin resistance and risk of type II diabetes, probably due to its elongation in the organism to vaccenic acid and ulterior desaturation to rumenic acid, while C16:2 could act as a substrate for the synthesis of long chain x-6 fatty acids. The data obtained in three experiments were used. The oils tested in each experiment were high oleic sunflower oil (HOSO), regular sunflower oil (RSO) and linseed oil (LO). In each experiment, four treatments were tested: control diet (CTR) without added oil, or the same diet added with 30, 48 or 66 g/d of oil. At the beginning of each experiment, 3 mid-lactation Malagueña goats, kept in individual cages were randomly assigned to each one of the four treatments. The basal diet comprised a pelleted concentrate and alfalfa hay and was the same in all the treatments and experiments. Milk fatty acid composition was determined by gas chromatography on the lipid fraction extracted and subjected to methylation. Data were analyzed with a nested mixed model by using the MIXED procedure of SAS UE 3.5. Linear trends and least-squares mean differences were tested by polynomial and orthogonal contrasts. Supplementation with 30 to 66 g/d of RSO or LO had a positive and linear effect (p<.05) on the content of trans-9 C16:1 in milk fat. The HOSO only increased (p<.05) the milk fat content of trans-9 C16:1 at a supplementation level of 66 g/d, and the response was also linear (p<.05). The content of C16:2 in milk fat only increased (p<.05), compared to CTR, when the animals consumed LO. This change was linear (p<.05) and correlated (p<.05) with that of trans-9 C16:1. The present work indicate that the increase of trans-9 C16:1 content in goat milk fat, after plant oil supplementation, depends on the unsaturation degree of the oil and is higher when the amount of supplied oil increases. There is a positive relationship between the consumption of LO and the contents of C16:2 in milk fat and also between the contents of C16:2 and trans-9 C16:1 in milk fat, which deserves further research

Peer reviewed