Omega-3 (n-3) fatty acids are known immunomodulators that attenuate inflammatory responses. Our goal was to evaluate the effects of feeding microencapsulated forms of fish, algae, and oleic acid oils on the response to an immune challenge. Nine Holstein cows (mean ± SD: 82 ± 18 DIM; 3.7 ± 0.9 lactations) were randomly assigned to treatments in a replicated 3 × 3 Latin Square design with 9-d periods and 7-d washouts. At d 9 of each period cows received an i.v. lipopolysaccharide (LPS) bolus (30 ng/kg of BW of E. coli O55:B5). Cows were milked twice daily. Blood was sampled at h 0, 2, 6, 12 and 24, relative to LPS challenge. Treatments were top-dressed daily and consisted of microencapsulated fish oil (FO; Prototype 6; 36% fish oil), algae oil (ALG; Prototype 39; 45% algae oil), and oleic acid (OA; Prototype 40; 20% oleic acid). The FO and ALG products delivered 25 g of the sum of n-3 (20:5 and 22:6), while OA provided 40 g of c9,18:1. Lipid supply was balanced at 226 g/cow/d. Data were analyzed under a mixed model with fixed effects of treatment, parity, time, and their interactions. Cows on FO and ALG tended to suffer a lower milk yield reduction than OA cows (P=0.12), and DMI was higher in FO relative to ALG (P=0.06). Milk fat content was higher in ALG relative to FO (P<0.05). No treatment effects were detected on plasma glucose, however, at h 2 ALG had lower levels of glucose than FO and OA cows (P<0.05). Plasma NEFA peaked at h 2 and 24 (Time, P<0.05) and TNF-alfa at h 6 (Time, P<0.05) with lower levels at h12 for ALG and FO compared to OA (P<0.15). Cows supplemented with ALG, tended to have lower insulin levels (P=0.10) and significantly higher Interleukin-1 β (P<0.05) compared to FO. Response to an immune challenge may depend upon chain length degree of saturation of the unsaturated fat supplements.
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