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https://hdl.handle.net/1959.11/23274
Title: | Effect of intra-ruminal urea infusions and changing digestible organic intake on nitrogen kinetics in sheep fed rice straw | Contributor(s): | Hettiarachchi, M (author); Dixon, R M (author); Nolan, John V (author) | Publication Date: | 1999 | DOI: | 10.1017/S0021859699006590 | Handle Link: | https://hdl.handle.net/1959.11/23274 | Abstract: | Sixteen sheep were continuously fed diets based on straw, straw and barley grain, or NaOH-treated straw, each with adequate minerals and with or without additional urea (7.3 g N/day for the straw and straw and barley diets; 14-4 g N/day for the diet containing NaOH-treated straw) infused intra-ruminally. [14C] tracers were used to measure the rate of irreversible loss (i.e. synthesis) of plasma urea and its transfer to the rumen and to the remainder of the gastrointestinal tract in 4-6 sheep per treatment. [15N] tracers were also used to make these measurements in four sheep fed the straw, straw and barley and straw and barley with intra-ruminal urea infusions. Inclusion of the barley grain in the diet increased digestible organic matter intake by c. 70%. Replacing the straw with a greater amount of NaOH-treated straw increased digestible organic matter intake by 43 % in the absence of additional urea, and by 65% when urea was infused intra-ruminally. Rumen ammonia concentrations were 37 and 31 mg N/l when straw or straw and barley diets respectively were provided and were reduced to 3 mg N/l when treated straw was given to the sheep. These concentrations exceeded 223 mg N/l when urea was infused intra-ruminally. Rate of irreversible loss of plasma urea measured using [14C]urea ranged from 3.7 g N/day in sheep given the treated straw diet to 16.8 g N/day when urea was infused intra-ruminally, while this rate was correlated with plasma urea concentration. In the three diets where it was measured, rate of irreversible loss of [15N]urea was on average 0.73 of the rate of irreversible loss of [14C]urea. Measurements made with 14C and 15N tracers of plasma urea transfer to the rumen were similar. This transfer measured with 14C tracers ranged from 1-4 to 2.4 g N/day for the three diets without additional urea, while providing urea by intra-ruminal infusions reduced the transfer to 1.1-1.4 g N/day. Transfer of plasma urea to the rumen was not changed by the higher digestible organic matter intake associated with either inclusion of barley grain in the diet or provision of a greater amount of more highly digestible NaOH-treated straw. These studies indicate that plasma urea transfer to the rumen is not always increased by greater organic matter fermentation in the rumen. | Publication Type: | Journal Article | Source of Publication: | The Journal of Agricultural Science, v.133, p. 109-121 | Publisher: | Cambridge University Press | Place of Publication: | United Kingdom | ISSN: | 1469-5146 0021-8596 |
Fields of Research (FoR) 2008: | 070204 Animal Nutrition | Socio-Economic Objective (SEO) 2008: | 970107 Expanding Knowledge in the Agricultural and Veterinary Sciences | Peer Reviewed: | Yes | HERDC Category Description: | C1 Refereed Article in a Scholarly Journal |
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Appears in Collections: | Journal Article |
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