Dietary protein and chromium tripicolinate in suffolk wether lambs: Effects on production characteristics, metabolic and hormonal responses, and immune status

Thirty-two Suffolk wether lambs were fed for 84 d in a 2 × 2 factorial experiment using two levels of dietary protein (9.0 to 12.1% CP, low protein, LP; or 12.8 to 14.4% CP, high protein, HP) and supplemental Cr (none, C; or 400 ppb Cr as chromium tripicolinate, Cr). At 14-to 21-d intervals, lambs were weighed, and jugular blood samples were collected. Mean ADG and carcass weight (P > .10) did not differ. In lambs fed HP, Cr reduced liver weight and increased kidney weight (P < .01). Lambs fed HP had elevated plasma urea N (PUN; P < .01) and albumin (P < .04). During an i.v. epinephrine challenge on d 43, plasma cortisol declined in lambs fed Cr (Cr × time, P < .03) and in lambs fed LP (CP × time, P < .001). An i.v. glucose tolerance test conducted 3 h later showed that supplemental Cr decreased glucose clearance rate in lambs fed HP (CP × Cr, P < .10) but not in lambs fed LP. On d 62, PUN was increased in lambs fed HP (P < .001) between 0 and 3 h postprandial, and there was a Cr × CP interaction (P < .04). Postprandial plasma NEFA declined with Cr vs C (Cr × time, P < .07) and with HP vs LP (CP × time, P < .10). By d 66, lambs fed Cr had an elevated (P < .03) blood platelet and fibrinogen content. Chromium increased erythrocyte count in lambs fed HP (Cr × CP, P < .08), and isolated peripheral lymphocytes had greater blastogenic response to 4 μg/mL of phytohemagglutinin (Cr × CP, P < .001). The lymphocyte response to pokeweed mitogen (.2 μg/mL) was reduced in lambs fed Cr (P < .10). In the present experiment, Cr supplementation had minimal and inconsistent effects on production and metabolic criteria of lambs.