In situ and in vitro estimation of mineral release from common feedstuffs fed to cattle

• Published in: The Journal of agricultural science Vol. 155; no. 7; pp. 1160 - 1173
• Main Authors: ZANETTI, D., MENEZES, A. C. B., SILVA, F. A. S., COSTA E SILVA, L. F., ROTTA, P. P., DETMANN, E., ENGLE, T. E., VALADARES FILHO, S. C.
• Format: Journal Article
• Language: English
• Published: Cambridge, UK Cambridge University Press 01.09.2017
• Subjects: Abomasum; Animal Research Papers; Animal sciences; Asymptotic methods; Beef cattle; Cattle; Cluster analysis; Computer simulation; Correlation; Dietary minerals; Digestibility; Digestion; Dry matter; Feeds; Fermentation; Forage; Gastrointestinal tract; Group dynamics; Hydrochloric acid; In vitro methods and tests; Minerals; Pepsin; Rumen; Solubilization; Brazil; United States > US
• ISSN: 0021-8596; 1469-5146
• DOI: 10.1017/S002185961700034X

The objective of the current study was to quantify the dry matter (DM) digestibility, and total ash (TA) and mineral release from 12 concentrate and 12 forage feedstuffs commonly fed to cattle using in situ and in vitro methods. Concentrate and forage feedstuffs were incubated in the rumen of ruminally cannulated beef bulls at eight different time points. Two different trials were conducted for concentrates and forages, with maximum incubation time of 72 and 120 h, respectively. The residue from samples incubated for 24 h were treated with pepsin and hydrochloric acid to simulate abomasum digestion in vitro. The initial and residual samples after in situ and in vitro incubations were measured. An asymptotic model was adopted for estimating solubility of minerals, disappearance rate of DM, and TA. Correlations between feedstuff contents and mineral release were evaluated. Residual samples from rumen fermentation after 24 h were incubated in simulated abomasal conditions and mineral release was measured. Cluster analysis was performed to group feedstuffs in relation to TA release. Large variability was observed between concentrate and forage feedstuffs for all constituents analysed. Large variability was observed for the effective ruminal degradation of TA and individual mineral release. When feedstuffs were clustered according to the immediately soluble fraction (‘a’), the insoluble by potentially releasable fraction (‘b’) and the release rate of ‘b’ (‘kd’,/h) estimates of TA ruminal release, four groups were identified. From group ‘1’ to group ‘4’, an increase in the soluble fraction and a reduction in both moderate releasable fraction and release rate was observed. Neutral detergent fibre content had a negative correlation with mineral release in the rumen, while mineral content had a positive correlation. These results demonstrate that mineral solubilization in the digestive tract is not the limiting factor for mineral absorption from the feedstuffs tested.