|KELLY, W - World West Sire Services|
|LARSON, C - Zinpro Corporation|
Submitted to: Journal of Agricultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/2017
Publication Date: 7/1/2017
Citation: Waterman, R.C., Kelly, W.L., Larson, C.K., Petersen, M.K. 2017. Comparison of supplemental cobalt form on fibre digestion and cobalamin concentrations in cattle. Journal of Agricultural Science. 155(5):832-838. doi:10.1017/S0021859617000107.
Interpretive Summary: Cobalt (Co), an essential trace element, has long been recognized to have several important functions in the ruminant. The effectiveness of supplemental Co is dependent on the biological availability of Co not only to ruminal microorganisms but ultimately the host ruminant. Thus, the source in which Co is fed may be of importance to both vitamin B12 production and the various roles Co is responsible for in the ruminant animal. However, limited information is known about organic Co sources and what, if any, benefits apply to supplementing an organic source of Co to ruminant diets. The objective of this study was to determine the effect of supplementing an organic Co source on in situ fiber fermentation and serum vitamin B12 concentrations. Our research indicates an increased extent of fiber digestion in later incubation hours. Very few studies have increased disappearance with any supplementation this late in the fermentation process thus cobalt may be a valuable resource for maximizing forage fermentation. Although there was a increase in organic matter disappearance at 48 h during the residual period this is not to be directly attributed to cobalt supplementation and the 96 h interaction detected describes extent of fiber disappearance to be enhanced in cows supplemented with CGH with CC cows numerically having improved in situ organic matter disappearance. Cows in this study were not as challenged as a cow grazing late season vegetation might be in the Northern Great Plains, thus this may be an area worthy of further investigation.
Technical Abstract: Cobalt is essential for rumen microbial metabolism to synthesize methane, acetate and methionine. It also serves as a structural component of vitamin B12, which functions as a coenzyme in energy metabolism. A study was conducted to determine if cobalt form (cobalt carbonate vs cobalt glucoheptonate) supplemented above NRC requirements would improve digestibility of a low quality forage diet and change serum cobalamin concentrations. Nineteen ruminally-cannulated cows (577 ± 13 kg) were individually fed in a completely randomized experimental design. Cows were fed a grass hay diet (7.9% CP, 56% TDN, 63% NDF, 87% DM) at 2.25% of BW for a 62 d study, which consisted of 3 periods; acclimation (AC), treatment (TR), and residual (RE). Cows were stratified by age (5 ± 0.37 yr) and lactational history, and assigned to receive 12.5 mg supplemental cobalt in 1 of 2 forms: (1) 27.2 mg of cobalt carbonate (CC, n =11 cows) or (2) 50 mg of cobalt glucoheptonate (CGH, n = 8 cows). Supplement was administered daily via a gelatin capsule placed directly into the rumen 2 h after feeding. During the last 96 h of each period, forage digestibility was measured using an in situ nylon bag technique. Blood samples were collected 4 and 6 h following feeding, and 24 h before the end of each period. Measurements taken in the AC period were used as covariates for analysis in the TR and RE periods. A treatment × period interaction (P = 0.03) was detected for in situ OM disappearance at 96 h; (TR period, 68.44 and 70.83 ± 0.81 %, and RE period, 67.61 and 66.82 ± 0.75 %, for CC and CGH, respectively). Once inclusion of cobalt in the CGH group was removed, OM disappearance was reduced by 4.01 % compared to 0.82 % in the CC cows. The NDF disappearance (OM basis) was lower for the TR period compared to the RE period at 48 h (P < 0.001; 62.95 and 65.18 ± 0.39 %, respectively). However, by 96 h the NDF disappearance was higher for TR period than the RE period (P = 0.02; 70.44 and 68.89 ± 0.44 %; respectively). No differences were detected for cobalamin serum levels or rate of fiber fermentation. The outcomes of this research signify that there may be slight residual effect of cobalt supplementation on fermentation; there was also an indication that cobalt source may enhances the overall extent of fermentation.