Effect of grazing cycle on milk production of cows on kikuyu pasture

Abstract

Kikuyu pasture (Pennisetum clandestinum) was evaluated as forage for milk production during the 1985/86 and 1986187 grazing seasons at the Bathurst Research Station in the seaboard area of the Eastern Cape. The effect of different rotational grazing cycle lengths on milk production, body weight, herbage intake, digestibility and grazing time was investigated. Pastures were stocked at two Friesian cows per ha and grazed for l, 2 or 4-day periods of 15, 30 or 60 days rotation cycles, respectively. Data were recorded during the grazing season which lasted from December to May eachy ear. Milk (10.9 kg) and fat-correctedm ilk (FCM; l0.l kg) yields were highest( P < 0.01) with the 30-day cycle. Neither butterfat (3.55 t 0.035Vo), nor protein (3.19 t 0.022%) content of the milk was affected by rotation cycle. Milk yield patterns showed a marked autumn slump with the 15-day cycle while the other two cycles reflected a steady decline in milk production from 13.5 kg in December to 8.4 kg in May. Mean live body weight (550.7 !2.92 kg) did not differ between cycles but followed different patterns during the growing season. Neither organic matter (OM) intake (14.2 t 0.188 kg), nor OM in vitro digestibility (56.3 tl .07%) differed between cycles. OM digestibilityd ecreased(P s 0.01) in all treatmentsf rom 67.6%oin Decembert o 44.7o/ion May. Cows in the 15- daycycle grazed longer (8.1hours;P<0.01) per day to compensate for the lack of DM availability. Overall, the 30- day cycle proved to be the best grazing strategy for kikuyu pasture in this investigation. Kikoejoeweiding( Pennisetumc landestinum)is vir melkproduksieg edurended ie weiseisoenev an 1985/86e n 1986/ 87 by die Bathurst Proefplaas in die oostelike kusgebied geevalueer. Die invloed van verskillende frekwensie rotasiebeweiding op aspektev an melkproduksie,l iggaamsgewig,v oerinname,v erteerbaarheide n weidingstyd is ondersoek. D ie lengtev an die rotasiesiklussvea n die drie behandelingsw as 15,3 0 en 60 daem et 1,2 en 4 dae besettings, onderskeidelik.D ata is deurlopendi n die weiseisoenw at vanaf Desembert ot Mei strek,v ersamel.M elk (10.9 kg) en vet gekorrigeerdem elk (VGM; 10.1k g) opbrengstew as die hoogste( P < 0.01) met die 30-daes iklus.B ottervet (3.55 t 0.35%) en proteTeninhou(d3 .19 t 0.022%)v an melk is nie deur die lengtev an die siklusseb eTnvloedn ie. Seisoenalem elkproduksietendensteo on 'n duidelikeh erfs insinkingm et die l5-dae siklus terwyl die anderb ehandelings 'n geleidelikea fnamev anaf 13.5k g melk in Desembert ot 8.4 kg in Mei weerspieelG. emiddeldel iggaamsgewigtev an koeieh et nie tussens iklussev erskiln ie (550.7! 2.92 kg) maarh et ook verskillendet endenseg edurende die weiseisoeng evolg.B eide OM-inname (14.2t 0.18 8 kg) en OM in vitro verteerbaarhei(d5 6.3t | .072%) het nie tussens iklussev erskil nie. OM-verteerbaarheidh et in al die siklussev an 67. 60/oin Desembert ot 44.7% in Mei afgeneem (P < 0.01). Koeie in die l5-dae siklus het langer (8.1 uur; P < 0.01) per dag gewei om te kompenseer vir die tekort aan DM-beskikbaarheid. In geheel was die 30-dae siklus die beste weidingstrategie vir kikoejoe in die suidoostelike kusgebied.

Keywords: Canopy height, dairy cows, kikuyu pasture, milk yield, rotation cycle.