Three experiments compared ruminal, physiological, and performance responses of beef steers consuming hay ad libitum and receiving grain-based supplements without (control) or with (CAM) the inclusion of camelina meal. In Exp. 1, 9 steers fitted with ruminal cannulas received CAM (2.04 kg of DM/d; n = 5) or control (2.20 kg of DM/d; n = 4). Steers receiving CAM had reduced (P = 0.01) total DMI and tended to have reduced (P = 0.10) forage DMI compared with control. No treatment effects were detected (P ? 0.35) for ruminal hay degradability parameters. In Exp. 2, 14 steers fed CAM (1.52 kg of DM/d; n = 7) or control (1.65 kg of DM/d; n = 7) were assigned to a corticotropin-releasing hormone (CRH; 0.1 ìg/kg of BW) and a thyrotropin-releasing hormone (TRH; 0.33 ìg/kg of BW) challenge. Steers fed CAM had greater (P < 0.05) serum concentrations of PUFA compared with control before challenges. Upon CRH infusion, plasma haptoglobin concentrations tended (P = 0.10) to be reduced and ceruloplasmin concentrations increased at a lesser rate in CAM steers compared with control (treatment ? time; P < 0.01). Upon TRH infusion, no treatment effects were detected (P ? 0.55) for serum thyrotropin-stimulating hormone, triiodothyronine, and thyroxine. In Exp. 3, 60 steers were allocated to 20 pens. Pens were assigned randomly to receive CAM (2.04 kg of DM/steer daily; n = 10) or control (2.20 kg of DM/steer daily; n = 10) during preconditioning (PC; d -28 to 0). On d 0, steers were transported for 24 h. Upon arrival, pens were assigned randomly to receive CAM or control during feedlot receiving (FR; d 1 to 29). During PC, CAM steers had reduced (P < 0.01) forage and total DMI, and tended to have reduced (P = 0.10) ADG compared with control. Plasma linolenic acid concentrations increased during PC for CAM steers, but not for control (treatment ? day; P = 0.02). During FR, steers fed CAM during PC had reduced (P < 0.01) forage and total DMI, but tended (P = 0.10) to have greater G:F compared with control. Steers fed CAM during FR had greater (P < 0.05) plasma concentrations of PUFA, and reduced rectal temperature and concentrations of haptoglobin and ceruloplasmin during FR compared with control. In summary, CAM supplementation to steers impaired forage and total DMI, did not alter thyroid gland function, increased circulating concentrations of PUFA, and lessened the acute-phase protein reaction elicited by neuroendocrine stress responses.
Animal Feed Animal Nutritional Physiological Phenomena