This study was carried out to evaluate the reliability of using faecal N as a predictor of organic matter (OM) intake by sheep and cattle fed a natural pasture hay

GENRO, T. C. M.

KOZLOSKI, G. V.

LONGO, T. R.

OLIVEIRA, L. de

ONGARATTO, F.

ZILIO, E. M. C.

English

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Fecal N excretion as an approach to estimate forage intake by sheep and cattle Gilberto V. Kozloski*1, Elissandra M. C. Zilio1 , Fernando Ongaratto1 , Thais R. Longo,Lisandre de Oliveira1, Teresa C. M. Genro2* Professsor Associado 1 Universidade Federal de Santa Maria, Av. Roraima 1000,Bairro Camobi, 97105-900, Santa Maria, RS; 2 Centro de Pesquisa Pecuária Sul,EMBRAPA, Bagé, RS. * gilberto.kozloski@ufsm.brThis study was carried out to evaluate the reliability of using faecal N as a predictor oforganic matter (OM) intake by sheep and cattle fed a natural pasture hay. The hay wasproduced from two areas of natural grassland pastures of Southern Brazil by cutting thesward 5 cm above the ground, and contained on average 0.93 of OM, 12.6 g kg-1 of Nand 775 g kg-1 of neutral detergent fibre (dry matter (DM) basis). Two digestibility trialswere  conducted  with  male  sheep  (25±6  kg  mean  body  weight  (BW))  housed  inmetabolism cages and two digestibility trials were conducted with steers (180±23 kgmean BW) housed in individual pens. Two trials with sheep and one trial with cattlewere conducted as a replicated 3 × 3 Latin Square (n=18) whereas one additional trialwith cattle was conducted in a simple 3 × 3 Latin Square (n=6) design. In all trials theanimals were fed only with hay offered in either amount 15 or 20 g DM kg-1 BW, or adlibitum, which constituted the experimental treatments in each trial. The experimentalperiods vary from 15 to 21 days, including 10 to 14 days for adaptation and 5 to 7 daysfor data and sample collection. In all trials total feed offered and leftovers, as well astotal feces were measured and sampled daily throughout the collection periods.  Datawere analyzed using a variance-covariance model where the animal specie was includedas the class fixed effect. No effect of specie was observed for any variable. The actualOM intake varied from 3.8 to 27.0 g day-1.kg BW and the excretion of fecal N variedfrom  0.04  to  0.21  g  day-1.kg  BW.  The  apparent  OM  digestibility  was  on  average0.44±0.09 and was not affected by the level of forage intake. The OM intake (y, g kg-1BW) was linearly related to the amount of N excreted in feces (x, g kg-1 BW) whichlinear equation was:  y=1.10 + 101.2x, R2=0.83, P<0.05. In conclusion, the OM intakeby sheep or cattle grazing a natural grassland in Southern Brazil might be estimatedbased on the amount of N excreted in feces. Key words: fecal nitrogen, methodology, natural grasslands, organic matter intake, ruminants

Fecal N excretion as an approach to estimate forage intake by sheep and cattle.

http://www.alice.cnptia.embrapa.br/bitstream/doc/1058897/1/ResumoSBZNfecal.pdf

Fecal N excretion as an approach to estimate forage intake by sheep and cattle.

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