Effect of rumen-protected Capsicum oleoresin on productivity and responses to a glucose tolerance test in lactating dairy cows

Abstract Text: The objective of this experiment was to investigate the effects of rumen-protected Capsicum oleoresin (RPC) on productivity and responses to a glucose tolerance test in dairy cows. Nine multiparous Holstein cows (100 ± 9.1 days in milk; 665 ± 83.3 kg BW) were used in a replicated 3 × 3 Latin square design experiment balanced for residual effects with 3, 28-d periods. Treatments were 0 (control), 100, and 200 mg RPC/cow/d. RPC was mixed with a small portion of the total mixed ration and top-dressed. DMI (29.5 kg/d; SEM = 0.74) was not affected (P = 0.72) by RPC. Milk yield tended to increase (P = 0.06; SEM = 1.27) for RPC compared with the control: 42.8, 44.7, and 43.9 kg/d for the control, 100, and 200 mg RPC/cow/d, respectively. Feed efficiency was linearly increased (P < 0.01; SEM = 0.056) by RPC supplementation: 1.48, 1.52, and 1.57 kg/kg, respectively. Concentrations of fat, true protein, and lactose in milk were not affected (P ≥ 0.69) by RPC. On the day of the glucose challenge, glucose was intravenously administered at 0.25 g/kg BW and blood samples were collected at 0, 5, 10, 15, 20, 30, 40, 50, 65, 80, and 110 min following administration. Serum glucose concentration peaked 5 min post-glucose administration. RPC did not affect serum glucose concentration during the glucose tolerance test. Insulin concentration at 5, 10, and 40 min and the area under the insulin concentration curve were lower (P ≤ 0.04) for both RPC application rates compared with the control. Peak concentration of insulin tended to be decreased (P = 0.07) by RPC. Concentration of NEFA in serum was linearly increased (P = 0.03) by RPC at and after 65 min following glucose administration. Concentration of beta-hydroxybutyrate in serum was not affected (P = 0.17) by RPC during the glucose tolerance test. In summary, milk yield and feed efficiency were increased by RPC in this experiment. RPC increased serum NEFA and decreased insulin concentration during the glucose tolerance test whereas glucose concentration was not affected by treatment. Data suggest that dietary supplementation of RPC increased insulin sensitivity and likely redirected glucose for lactose synthesis and milk production and also slightly enhanced fat mobilization in lactating dairy cows.

Keywords: capsicum, insulin sensitivity, milk production