UTILIZATION OF BARLEY STRAW BY STEERS - THE EFFECT OF QUANTITY AND SOURCE OF NITROGEN ON THE DEGRADATION OF STRAW FRACTIONS, PARTICLE OUTFLOW RATE AND INTAKE
Iv. Nsahlai et al., UTILIZATION OF BARLEY STRAW BY STEERS - THE EFFECT OF QUANTITY AND SOURCE OF NITROGEN ON THE DEGRADATION OF STRAW FRACTIONS, PARTICLE OUTFLOW RATE AND INTAKE, Journal of Applied Animal Research, 14(1), 1998, pp. 33-50
This study evaluated the effect of quantity of rumen degradable nitrog
en (RDN; 1.37 vs 1.87 g RDN/MJ ME) and of source of nitrogen (N; Fish
us rapeseed meal) on the degradability of straw fractions, rumen metab
olities, particle passage rate, intake and digestibility of barley str
aw using six ruminally fistulated Friesian steers in a replicated 3x3
Latin square experimental design, rite degradability of leaves of spri
ng (LS) and unknown (LU)varieties and stems of spring (SS) and unknown
(SU) varieties of barley straw was determined The three test protein
supplements were designated low nitrogen with rapeseed meal (LNR; 1.37
g RDN/MJ ME; 14.25 g N/kg DM) and high nitrogen with either rapeseed
meal (HNR; 1.86 g RDN/MJ ME; 18.80 g N'/kg DM) or fish meal (HNF; 1.36
g RDN/MJ ME; 18.82 g N/kg DM). For both the DM and ADF, leaves degrad
ed to a greater extent (P<0.01) and faster (P<0.01) than stems. Increa
sed RDN improved the rate of degradation of straw fraction by proporti
onately 0.082 to 0.289, but the difference was significant (P<0.05) fo
r the LS fraction only. With the exception of LU, HNF increased (P<0.0
5) the rate of degradation by proportionately 0.139 to 0.153 compared
with LNR. Both HNR and HNF increased straw intake relative to the LNR.
HNR also increased the duration over which I rumen concentration of a
mmonia-N was above 24 mg/l compared to HNF (P<0.05) and LNR (P<0.05).
Meanwhile, HNF sustained higher ruminal concentrations of iso-valerate
than either HNR or LNR. The HNR and HNF diets were respectively assoc
iated with 7% and 10% increase in the pow of indigestible matter throu
gh the gut. It was concluded that the quantity of RDN but not the sour
ce of N is an important factor affecting the degradation of leaves of
barley straw.