Dietary black soldier fly oil reduces oxidative stress in dairy cows without affecting blood nutritional parameters

Some lipid sources traditionally used in ruminant nutrition pose concerns due to their negative effects on the environment. Therefore, nutritionists are looking for innovative and sustainable feedstuffs to be included in ruminant diets. The oil extracted from black soldier fly (Hermetia illucens) larvae (HIO), being rich in lauric and palmitic acids, could replace conventional lipid sources characterized by high saturation levels. This study aimed at assessing the effects of replacing hydrogenated palm fat (HPF) with HIO in the diet of dairy cows on their blood nutritional parameters and oxidative stress. Twenty-six Valdostana Red Pied cows fed mixed hay ad libitum were divided into two balanced groups that received isonitrogenous and isoenergetic concentrates containing HPF or HIO at 3% as fed (162 g/head×day). Individual blood samples were collected from the jugular vein, before the morning milking, at the beginning (d0, the day before starting the experimental diets administration), middle (d26) and end (d50) of the trial. Plasma collected at d0 and d50 was assayed using colorimetric enzymatic reactions with a multiparameter analyzer (Kone Instruments Corporation) to determine non-esterified fatty acids, cholesterol, glucose, triglycerides, urea, and β-hydroxybutyrate concentrations. Serum collected at d0, d26 and d50 was analyzed for blood oxidative stress using the OXY-Adsorbent Test and the d-ROMs Test (Diacron International, Grosseto, Italy). Data was statistically analyzed with SAS software using a mixed model, considering as factors the sampling period (repeated), the dietary treatment, their interaction (fixed), the animal (random), and the values of each parameter at d0 as a covariate. All the considered plasma metabolites did not differ between the two experimental groups (P>0.05). Serum antioxidant capacity was not affected by dietary treatment (P>0.05). However, lower d-ROMs concentrations were observed in the HIO-fed cows when compared to the HPF-fed ones (73.70 vs. 110.84 UCARR, respectively; 1 UCARR = 0.08 mg H2O2/dL; P<0.001). The interaction between diet and time was never significant. These results show that the dietary replacement of HPF with HIO increased the resistance to oxidative stress in dairy cows, which is known to weaken the animals and cause several diseases and metabolic disorders during lactation. The HIO naturally possesses antioxidant activity, suggesting its potential use as a novel energy source in ruminant nutrition. Research supported by Hi-Ga project; Green Era Hub on Agri Food and Biotechnology.