caa a22 4500 388060077 CHVBK 20180307125118.0 cr unu---uuuuu 161130e199812 xx s 000 0 eng 10.1017/S1357729800032847 doi S1357729800032847 pii (NATIONALLICENCE)cambridge-10.1017/S1357729800032847 Ruminal ammonia concentration and energy expenditure of cattle estimated by the carbon dioxide entry rate technique [Elektronische Daten] Five ruminallyfistulatedAngus steers (360 (s.e. 15·4) kg) were givenfood to maintain body weight constant: maize silage (TO) at 0·6 kg dry matter (DM) per 100 kg body weight twice a day. After a 15-day adaptation period they were infused continuously (I) for 96 h, with a solution of NaH14CO3 at a rate of 7 to 8 micro Curies (μCi) per h. On the last 2 days of infusion 30 g (Tl) and 60 g (T2) urea, respectively, were placed in the rumen at the end of the morning meal. Spot samples of urine (250 ml) were taken before and 5 h after the morning meal and after at least 24 h of infusion. Thereafter, animals continued with TO for one additional week, in which they were prepared with catheters inserted in salivary ducts and infused for 48 h, as previously described. Eighteen pairs of spot samples of urine and saliva were takenfrom three of thefive steers (369 (s.e. 20·7) kg), over a period of 5 h, after at least 24 h infusion (six per animal). Rate of carbon dioxide (CO2) production was estimated as the ratio USA (specific activity of CO2)from which energy expenditure was calculated (22 kj/l CO2). Silage composition, in situ degradability and ruminal ammonia and pH were measured. In situ degradability in thefirst 6 h was 200 g/kg and ruminal ammonia was in the range of 20·6 to 39·6 mg/l. Ammonia increased rapidly to 394·2 (T1) and 673·9 mg/l (T2) 1 h after addition of urea into the rumen but in 6 h in situ degradability was unchanged. Ruminal ammonia decreased linearly at rates (mgll per h) of89·3 in Tl (R2 = 0·57, s.d. = 21·5) and 151·6 in T2 (R2 = 0·81, s.d. = 23·3). Animal energy expenditure rates were not affected (P > 0·05) by treatment (TO = 15·6, Tl = 15·6 and T2 = 15·8 kj/h per M075). There was no difference (P > 0·05) in CO2 production rate (mllh per kg M0·75) determined from the SA of CO2 from urine (604) or saliva (630) samples. It was concluded that the energy cost associated with detoxification of the excess of ruminal ammonia was of minor importance in terms of total animal energy expenditure and that estimations ofC02 ratesfromsamples ofurine or saliva are comparable. Copyright © British Society of Animal Science 1998 ammonia nationallicence cattle nationallicence energy expenditure nationallicence urea nationallicence Di Marco O. N. Universidad National de Mar del Plata, Facultad de Ciencias Agrarias—Instituto Nacional de Tecnología Agropecuaria, EEA Balcarce, CC 276 (7620) Balcarce (BA), Argentina Castiñeiras P. Universidad National de Mar del Plata, Facultad de Ciencias Agrarias—Instituto Nacional de Tecnología Agropecuaria, EEA Balcarce, CC 276 (7620) Balcarce (BA), Argentina Aello M. S. Universidad National de Mar del Plata, Facultad de Ciencias Agrarias—Instituto Nacional de Tecnología Agropecuaria, EEA Balcarce, CC 276 (7620) Balcarce (BA), Argentina Animal Science Cambridge University Press 67/3(1998-12), 435-443 1357-7298 67:3<435 1998 67 ASC https://doi.org/10.1017/S1357729800032847 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1017/S1357729800032847 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Di Marco O. N. Universidad National de Mar del Plata, Facultad de Ciencias Agrarias—Instituto Nacional de Tecnología Agropecuaria, EEA Balcarce, CC 276 (7620) Balcarce (BA), Argentina NATIONALLICENCE 700 1- Castiñeiras P. Universidad National de Mar del Plata, Facultad de Ciencias Agrarias—Instituto Nacional de Tecnología Agropecuaria, EEA Balcarce, CC 276 (7620) Balcarce (BA), Argentina NATIONALLICENCE 700 1- Aello M. S. Universidad National de Mar del Plata, Facultad de Ciencias Agrarias—Instituto Nacional de Tecnología Agropecuaria, EEA Balcarce, CC 276 (7620) Balcarce (BA), Argentina NATIONALLICENCE 773 0- Animal Science Cambridge University Press 67/3(1998-12), 435-443 1357-7298 67:3<435 1998 67 ASC CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-cambridge