In sacco dry matter disappearanceo f herbagea nd maizem eal from the rumen of lactating Dorper and Merino ewess upplementedw ith protein and energy on native pasture

Abstract

Rumen fermentation was studied during three years in lactating Dorper and Merino ewes, supplemented daily with crude protein and./or energy via rumen fistulae on veld. Herbage, collected with oesophageally fistulated wethers, and maize meal were incubated in sacco in the rumen of the ewes. Four distinct observations were made in terms of in sacco dry matter (DM) disappearanceo f herbage,n amely: (i) a significant (P < 0. 05) difference between breeds in winter; (il) an increase of 7007o from winter to summer; (lli) a significant (P < 0.05) increase due to protein supplementation in winter; and (iv) a non-signihcant (P < 0.05) tendency to decrease in summer with increasing levels of energy supplementation. None of these differences or tendencies were evident in the ln sacco DM disappearanceo f maize meal during any of the trial periods.R esultsa red iscussedin relationt o changesi n rumen pH and rumen ammonia conccntration, as well as feed intake bv the ewes. in the same trials. Rumenfermentasie is gedurende drie jare bestudeer in lakterende Dorper- en Merino-ooie wat daagliks aanvullende energie en/of ruproteien per rumenfistel op veld ontvang het. Weidingsmateriaal wat met slukdermge fistuleerde hamels versamel is, asook mieliemeel, is in sacco in die rumen van ooie geinkubeer. In terme van in sacco droe materiaal (DM) verdwyning van weidingsmateriaal,is die volgende waarnemingsg emaak : (r) 'n betekenisvolle (/D < 0.05) verskil tussen rasse in die winter; (ll) 'n verhoging van bykans 1007o vanaf die winter na die somer; (iii)'nbetekenisvolle (P<0.05)verhogingasgevolgvanproteienaanvullingindie winter;en(lv)'nnie-betekenis volle (P < 0.05) tendenso m in die somert e verlaagm et toenemendep eile van aanvullendee nergie.N ie een van die verskille of tendense was in die in sacco DM verdwyning van mieliemeel waarneembaar nie. Resultate word bespreek aan die hand van veranderingei n rumen-pH en rumenammoniakkonsentrasiea, sook weidinginname deur die ooie, in dieselfde studies.

Keywords: Artificial f ibre bag technique, diet selection, feed intake, in sacco rumen fermentation, supplementary feeding, veld.