Effect of breed on the voluntary intake of grazing ewes during lactation

Abstract

SIX LACTATING SUFFOLK EWES AND EIGHT LACTATING RAMBOUILLET EWES, WITH TWINS, WERE USED TO DETERMINE BREED DIFFERENCES IN THE VOLUNTARY INTAKE OF A LOLIUM MULTIFL ORUM PASTURE, UNDER CONTINUOUS GRAZING. FECAL PRODUCTION WAS ESTIMATED USING 1 G OF CHROMIUM SESQUIOXIDE PER SHEEP AS AN EXTERNAL MARKER, ADMINISTERED IN TWO GELATIN CAPSULES PER ANIMAL, BEFORE AND AFTER THE GRAZING PERIOD (7:00 AND 17:30 H), FROM THE FOURTH TO THE 64TH DAY AFTER PARTURITION. FECAL SAMPLES WERE COLLECTED DIRECTLY FROM THE RECTUM OF EACH ANIMAL DURING THREE CONSECUTIVE DAYS, ON DAYS 18-20, 33-35, 48-50 AND 63-65 POSTPARTUM. THE IN VITRO DRY MATTER (DM) DIGESTIBILITY OF THE FORAGE WAS ESTIMATED FOR THE SAME DAYS TAKING THREE DAILY HAND-PLUCKED SAMPLES OF FORAGE. WITH THIS INFORMATION, VOLUNTARY INTAKE PER ANIMAL AND PER METABOLIC BODYWEIGHT WAS ESTIMATED. DATA WERE ANALYZED USING A COMPLETELY RANDOMIZED DESIGN WITH REPEATED MEASURES. VOLUNTARY INTAKE EXPRESSED IN KG OF DM PER ANIMAL (SUFFOLK = 3.28 VS. RAMBOUILLET = 2.44) AND PER METABOLIC BODYWEIGHT (SUFFOLK = 0.1045 VS. RAMBOUILLET = 0.1422 KGBW0.75) WAS LOWER FOR THE SUFFOLK THAN FOR THE RAMBOUILLET EWES, WHICH WAS PROBABLY DUE TO A BETTER PERFORMANCE OF THE RAMBOUILLET BREED UNDER GRAZING CONDITIONS.