Abstract
The effect of lucerne (Medicago sativa L.) pre-grazing pasture height on pasture intake and milk production was investigated in a sub-tropical partial mixed ration (PMR) dairy system in south-east Queensland, Australia. The experiment involved a 26-day adaptation period followed by an eight-day measurement period during April and May 2018. Twenty-four multiparous Holstein-Friesian dairy cows were offered a mixed ration at either 7 (low) or 14 (high) kg dry matter (DM)/cow/day and allocated pastures at pre-grazing heights ranging from 23 to 39 cm. The targeted pasture intake was 14 and 7 kg DM/cow/day for cows offered the low and high mixed ration allowances respectively, with a total intake target of 21 kg DM/cow/day. Pasture structure did not limit pasture intake as the all groups left at least 12% of the allocated area ungrazed, and therefore could selectively graze pasture. There was no significant difference in intake between mixed ration levels, however intake had a positive linear relationship with pre-grazing pasture height. For every one cm increase in pasture height, intake increased by 0.3 kg DM/cow/day. Using a grazing strategy that ensures the some pasture remains ungrazed and the pre-grazing height of lucerne is approximately 39 cm above ground level will maximise pasture intake in sub-tropical PMR dairy systems.
Highlights
Pastures are a highly important source of forage on many commercial dairy farms throughout the sub-tropical regions of Australia [1,2]
This study examined the effects of increasing pre-grazing pasture heights under the PUP grazing strategy and twoexamined mixed ration levelsofon defoliation intensity,pasture intake, heights and milk production
This study examined the effects of increasing pre-grazing pasture heights under the PUP grazing strategy and two mixed ration levels on defoliation intensity, intake, and milk production and composition of lactating dairy cows
Summary
Pastures are a highly important source of forage on many commercial dairy farms throughout the sub-tropical regions of Australia [1,2]. Farmers have adapted new strategies to utilise conserved forages to maintain production when pasture productivity is limited. These systems incorporate both high quality, low cost pastures and a mixed ration usually containing starch and protein based forages combined. Animals 2020, 10, 860 with concentrates and minerals, referred to as partial mixed rations (PMR) [2] These systems are relatively new within the sub-tropical regions of Australia and the interactions between pasture and mixed ration within the rumen, and the consequent effects on intake and production are not well understood when tropical forages are fed [2,3]. Manipulating either one of these parameters through grazing management strategies is likely to have significant effects on intake and productivity
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