Evaluation of fatty acids profile of milk produced by mid-lactating Holstein cows fed with enriched olive cake diet

The use of by-products such as olive cake (OC) for alternative animals feed is widespread to reduce cost associated with animal nutrition (due to the recent increasing costs), to limit environmental impact and to enhance the quality of meat and milk. In fact, it is well known that OC is rich in unsaturated fatty acids (UFA) and polyphenols. The aim of this study was to evaluate the effects of supplementing enriched OC (EOC) to mid-lactating Holstein cows on milk fatty acids (FA) profile. A total of 20 cows were enrolled into 2 homogeneous groups (10 for EOC group and 10 for CTR group) according to BCS (2.43±0.26), lactation period (113±47 d), and milk yield (31.42±3.28kg/d). The EOC group was fed with a 7% inclusion of enriched destoned OC, whereas control group (CTR) received a conventional diet. Milk samples were collected at d 0 and at d 28, to compare FAs in EOC and CTR group at d 0 and at d 28. FAs were extracted, methylated, and separated with a gas-chromatographer fitting a CP-Sil88 column. Peaks of individual FAs were identified and quantified using a 37 FAME standard. Data were analyzed with the PROC GLIMMIX of SAS. Values are expressed as a percentage of total FAME. The results showed that the inclusion of EOC for 28 days modified the FA profile of milk. In fact, at 28 d, among saturated, short- and medium-chain FAs, C10:0 (2.84 vs. 3.68; p=0.08), C13:0 (0.16 vs. 0.24; p=0.08), and C14:0 (12.73 vs. 14.64; p=0.06) tended to be lower in EOC compared with CTR group. A lower content of C12:0 (3.77 vs. 4.93; p=0.05), C15:0 (1.61 vs. CTR 2.01; p=0.03), C16:0 (33.73 vs. 36.76; p < 0.001) was also observed in EOC compared with CTR group. Concerning long-chain fatty acids, EOC group had greater C18:1 cis-9 (20.32 vs. 16.63; p=0.02) compared with CTR. C18:0 tended to be greater in EOC compared with CTR group (6.68 vs. 4.51, respectively; p=0.08), whereas C22:2 (0.05 vs. 0.09; p=0.07) and C24:0 (0.04 vs. 0.08; p=0.09) tended to be lower in EOC compared with CTR. These results point out the beneficial effects of supplementing EOC since it improves milk FAs profile that are positively related to human health and are indicative of a better nutritional and nutraceutical properties of milk. Thereby, using this by-product may be considered as a good alternative to conventional feed, giving moreover an added value to the final product.