Influence du parcage nocturne et du fractionnement de la surface à pâturer sur l'ingestion chez les génisses créoles conduites à l'attache

Abstract

The experiment was aimed at studying the effect of nocturnal enclosing and splitting the offered area during the day upon intake and feeding behaviour of creole heifers grazing Dichanthium sp pastures. The three treatments were i) a whole area available during 24 h (S24); ii) a same whole area available during 11 h (S11); iii) a same area available during 11 h, but divided into two parts (F11), the first available from 700 to 1200 hours, the second one from 1230 to 1800 hours. Offered area and daily herbage allowance were similar for the three treatments. All the heifers were moved to a fresh area every day at 700 hours. The treatments S11 and F11 were tethered outside pasture at night from 1800 hours and no supplementary feed was available. Three groups of two heifers (mean weight 162 kg) were used in a 3 x 3 latin square design repeated two times (six periods). Organic matter intake (MOI, kg) was calculated from faecal organic matter output and organic matter digestibility (dMO). dMO was predicted from faecal crude protein content (MATf, % MO) in feeding trials with similar swards: dMO = 0.983 - 4.002/MATf; RSD = 0.023; R2 = 0.84. Total faecal excretion was collected for 4 days. The mean herbage allowance was 11.6 kg OM/heifer/days. MOI was greater in treatment S24 (4.3 kg OM, P < 0,001) than in treatment S11 and F11 (3.7 kg OM on the mean). This was related to a higher grazing time in S24. Indeed, daylight grazing times (mean 320 mn) and biting rates (53 bites/min) were not affected by treatment, nocturnal grazing time was 100 min for treatment S24. However, biting rates during the night (42 bites/min, P < 0.00/; was lower than during the daylight period. Splitting the daylight offered area did not affect herbage intake or feeding behaviour.