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      Rumen fermentation characteristics of dairy cows grazing different allowances of Persian clover- or perennial ryegrass-dominant swards in spring

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      Australian Journal of Experimental Agriculture
      CSIRO Publishing

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          Abstract

          An experiment was conducted in which cows in early lactation grazed Persian clover (Trifolium resupinatum L.) or perennial ryegrass (Lolium perenne L.)-dominant pastures at low or high pasture allowances in order to determine the effects of pasture type and level of feeding on rumen fermentation patterns. The hypotheses for grazing dairy cows were: (i) the consumption of Persian clover would result in a more rapid rate of degradation and less stable rumen fermentation patterns compared with perennial ryegrass; and (ii) the greater intake of cows grazing at high compared with low pasture allowances would also cause less stable rumen fermentation patterns. Stability of rumen fermentation refers to the level to which rumen fluid pH declines, especially for long periods of a day, indicating that the rumen is not coping with neutralising and/or removing acids. Cows grazing Persian clover had lower (P<0.05) average daily rumen fluid pH (5.7 v. 5.9), molar proportions of acetic acid (68.3 v. 70.6%) and ratios of lipogenic to glucogenic volatile fatty acid (4.6 v. 5.1) in the rumen than those grazing perennial ryegrass. They had higher (P<0.05) rumen fluid ammonia-N (26.3 v. 13.0 mg/100 mL) and total volatile fatty acid (165 v. 134 mmol/L) concentrations and molar proportions of butyric (11.3 v. 10.7%) and propionic (17.2 v. 16.1%) acids than cows grazing perennial ryegrass. Cows grazing at low pasture allowances had a higher (P<0.05) average daily rumen fluid pH (5.9 v. 5.7) and lower rumen fluid ammonia-N (18.6 v. 20.7 mg/100 mL) and total volatile fatty acid (143 v. 156 mmol/L) concentrations than cows grazing at high pasture allowances. Cows given Persian clover at the high allowance had a rumen fluid pH less than 6.0 for the entire day while rumen fluid pH was below 6.0 for at least 15 h of the day on all the other treatments. There was no effect (P>0.05) of pasture allowance on the degradation rate of perennial ryegrass dry matter, but the higher allowance of Persian clover resulted in the highest (P<0.05) rate of degradation of dry matter compared with either ryegrass treatment or the low allowance of Persian clover. The effective dry matter degradability of Persian clover was greater (P<0.05) than that of perennial ryegrass, and the effective dry matter degradability of herbage in cows grazing at low allowances was greater (P<0.05) than at higher allowances. However, future research should consider neutral detergent fibre degradation in grazing dairy cows with low rumen fluid pH levels.

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          • Record: found
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          The estimation of protein degradability in the rumen from incubation measurements weighted according to rate of passage

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            Volatile Fatty Acid Analyses of Blood and Rumen Fluid by Gas Chromatography

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              Relationship between fermentation acid production in the rumen and the requirement for physically effective fiber.

              The content of ruminally fermented OM in the diet affects the fiber requirement of dairy cattle. Physically effective fiber is the fraction of feed that stimulates chewing activity. Chewing, in turn, stimulates saliva secretion. Bicarbonate and phosphate buffers in saliva neutralize acids produced by fermentation of OM in the rumen. The balance between the production of fermentation acid and buffer secretion is a major determinant of ruminal pH. Low ruminal pH may decrease DMI, fiber digestibility, and microbial yield and thus decrease milk production and increase feed costs. Diets should be formulated to maintain adequate mean ruminal pH, and variation in ruminal pH should be minimized by feeding management. The fraction of OM that is fermented in the rumen varies greatly among diets. This variation affects the amount of fermentation acids produced and directly affects the amount of physically effective fiber that is required to maintain adequate ruminal pH. Acid production in the rumen is due primarily to fermentation of carbohydrates, which represent over 65% of the DM in diets of dairy cows and have the most variable ruminal degradation across diets. The non-fiber carbohydrate content of the diet is often used as a proxy for ruminal fermentability, but this measure is inadequate. Ruminal fermentation of both nonfiber carbohydrate and fiber is extremely variable, and this variability is not related to the nonfiber carbohydrate content of the diet. The interaction of ruminally fermented carbohydrate and physically effective fiber must be considered when diets for dairy cattle are evaluated and formulated.
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                Author and article information

                Journal
                Australian Journal of Experimental Agriculture
                Aust. J. Exp. Agric.
                CSIRO Publishing
                0816-1089
                2005
                2005
                : 45
                : 6
                : 665
                Article
                10.1071/EA04023
                48c0d293-68f3-43be-ba2d-9515ec86064d
                © 2005
                History

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