Estimation of pasture intake by ponies from liveweight change during six weeks at pasture

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Introduction

Values for daily dry matter (DM) pasture intakes by grazing equids have generally been reported to range from [as a percentage of liveweight (LW) on a DM basis] 1.5-2.0 percent for mature horses, 2.5 percent for lactating mares and 2.0-3.0 percent for weanlings (in NRC 2007). However, other studies have reported grazed pasture intakes of 5 percent or more of liveweight per day (Smith et al, 2007; McMeniman, 2000). However, such values have tended to be regarded with caution as they are considerably higher than many measured DM intakes by stabled horses, but concur with recent values of intakes of around 5 percent of LW of chopped fibre, or pelleted chaff reported by [2], [3] and Argo et al., (2002) respectively. Rapid weight gain is often achieved in grazing equids, particularly on spring and early summer pastures at a rate often difficult to achieve in even the most intensively fed stabled animals. This may suggest that the generally accepted estimates of pasture DM intakes may be too low. In this study a range of possible pasture DM intakes by mature ponies using their change in liveweight during six weeks turn out at pasture together with published ranges of pasture DE contents and DE requirements for maintenance and liveweight gain in ponies were calculated. Mature ponies were used as opposed to young stock, to prevent growth complicating interpretation of the results.

Section snippets

Materials and Methods

Four mature pony mares (average weight 268 ± 52 kg, age 6.5 ± 2.9 yrs) grazed a mixed species pasture containing largely perennial ryegrass (Lolium perenne), white clover (Trifolium repens), bentgrass (Agrostis alba), and Yorkshire fog (Holcus lanatus) for six weeks. The average pasture CP and NDF contents were 129 ± 4.03 and 423 ± 10.3 g/kg DM respectively,. Pony weights were recorded at the beginning of the trial and 5 times weekly during the six week grazing period on a calibrated

Results and Discussion

The chemical composition of the herbage may suggest a pasture of intermediate nutritive value.

The average daily weight gain of the four ponies over the entire trial was 0.956 ± 0.517 kg. The calculated pasture DM intakes are given in Table 1, where intakes for ponies with low, average and high DE requirements for maintenance and gain are presented when grazing summer pastures of low, average and high DE content. Calculated intakes ranged from 2.9 ± 0.8 percent of LW for ponies with low DE

Conclusion

The estimated pasture DM intakes reported here of 2.9-4.9 percent of liveweight (mean 3.8) are all higher than the generally accepted 2-2.5 percent of liveweight as being the normal range for voluntary intakes of pasture by equids. Nevertheless the results in this study concur with the estimated pasture intakes of 3.2-5.2 percent of liveweight of mature horses reported by Smith et al., 2007 using alkanes. Furthermore, the DE requirements calculated for the ponies in the current study did not

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