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ARS Home » Midwest Area » Madison, Wisconsin » U.S. Dairy Forage Research Center » Research » Publications at this Location » Publication #103705
Title: EMPIRICAL MODELLING OF BUFFER RECYCLING IN CATTLE

Author
item SAUVANT, D - RECHERCHE AGRON PARIS FRA
item MESCHY, F - RECHERCHE AGRON PARIS FRA
item Mertens, David

Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 6/20/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Estimates of buffer recycling through saliva in cattle were investigated as a function of diet characteristics. Because several experiments have shown a good relationship between saliva flow and ruminal liquid outflow, it was decided to use liquid outflow as an estimate of salivary flow. It was also assumed that the buffer concentration in sa1iva was constant and equal to 120 meq/l of bicarbonates and 25 meq/l of phosphates or about 11.35 g/l of sodium bicarbonate equivalents. A database containing observations from 65 pub1ications and 255 experimental groups with liquid outflow from the reticulo rumen was analyzed. Average liquid outflow was 166 +/- 72.4 l/d or 13.2 +/- 4.3 l/kg of dry matter intake (DMI). Average buffer recycling (BR) was equal to 3.56 +/-.14 g/d/kg of live weight (ranging from 0.83 to 6.53) or 150.3 +/- 48.8 g/kg DMI (BR/DMI ranged from 53.2 to 302.8). This last expression was more highly correlated with ruminal parameters and various characteristics of diet such as NDF (n = 240, R**2=.56), forage NDF (n = 177 R**2 = .56), and forage (n = 253, R**2 = .44) when each was expressed as concentration in dietary dry matter. The BR/DMI was also closely and quadratically related with index of mastication or chewing time per kg of DMI (n = 78, R**2 = .79). Accounting for differences among experiment improved these relationships. The BR/DMI was also related to ruminal parameters such as pH (pH = 5.83 + 0.0029 BR/DMI; n = 191, R**2 = .50, rsd = 0.08) and acetate/propionate ratio (A/P = 2.58 + 0.0060 BR/DMI; n = 186, R**2 = .40, rsd = 0.68). Moreover, BR/DMI was positively related to milk fat content (MFC = 2.71 + 0.0072 BR/DMI; n = 97, R**2 = .68, rsd = 0.38). These results suggest that estimated buffer recycling may be an important factor to integrate into diet formulation systems.