Submitted to: American Society of Animal Science Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2010
Publication Date: 7/15/2010
Citation: Harrelson, F.W., Ivey, S.L., Cox, S.H., Dunlap, R.L., Mulliniks, J.T., Carter, B.H., Luest, C.A., Petersen, M.K. 2010. Effect of supplemental protein source during the winter on pre- and postpartum glucose metabolism. American Society of Animal Science Annual Meeting 88(E-Suppl. 2):473. Abstract #734. Interpretive Summary:
Technical Abstract: Circulating serum glucose concentrations as well as glucose utilization have been shown to be affected by forage quality. Supplemental protein provided to grazing range cows while consuming low quality forage may improve glucose metabolism. The objective of our study was to determine the effects of winter protein supplement strategy on serum glucose half-life, insulin response, as well as identify the effects of previous gestational protein supplementation on mid lactation milk yield. The study was conducted two consecutive calving seasons utilizing 5 yr old Angus and Angus crossbred cows (n = 8/treatment each year, 530 kg average BW). Cows were supplemented until calving with 1) a control 36% CP (35% UIP of CP%) cottonseed meal based cube (CON), hand-fed at 454 g/d delivered 3d/wk ($16/45.4 kg), or 2) a self-fed 50% loose mineral and 50% fishmeal 33% CP (60% UIP of CP%) small supplement (SSP), formulated for a targeted consumption of 113g/d ($52/45.4 kg). After calving, cows were supplemented similarly (36% CP cube at 908 g/d offered 3 d/wk). Supplemental protein source affected (P = 0.03) glucose half-life, whereby the SSP cows had a lower half-life compared to CON (62 and 85 min respectively). There was also a supplement effect on insulin area under the curve (P < 0.01) with CON having a larger area compared to the SSP treatment (62.64 and 46.34 respectively). Prepartum glucose area under the curve (P = 0.95) and insulin half-life (P = 0.75) were unaffected by supplement treatment. Milk yield or components was not affected (P > 0.05) by supplement; however year showed a significant (P < 0.05) effect on these parameters. Milk yield was decreased from 7531 g in yr 1 to 4328 g in yr 2. This year effect may be explained by forage quality which was much poorer during yr 2 (~ 3% CP compared to ~8% CP in yr 1) and may have influenced the insulin resistance of the study cows.