Quantification of relative stock units for horses to permit correct application within pasture-based production systems

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dc.citation.issue1
dc.citation.volume64
dc.contributor.authorChin YY
dc.contributor.authorBack PJ
dc.contributor.authorGee EK
dc.contributor.authorHorne DJ
dc.contributor.authorRogers CW
dc.contributor.editorBryden W
dc.date.accessioned2024-06-03T21:47:24Z
dc.date.available2024-06-03T21:47:24Z
dc.date.issued2023-05-29
dc.description.abstractContext. Overseer® is the primary software tool used to estimate farm-level nutrient cycle and management for regulatory purposes in New Zealand. The model compares feed demand among different livestock by using ‘revised stock units’ (RSUs, the annual energy requirement of a mature ewe to raise a single lamb to weaning; 6000 MJ metabolisable energy). The RSUs for several common equine stock classes are not yet available, while those currently available within the model are based on the linear scaling of feed demand to liveweight, which does not consider allometric scaling of metabolism to liveweight or the differences in digestive physiology and nutrient metabolism between ruminants and monogastric hindgut fermenters (horses). Aim. To compare the current RSU values used in Overseer® for different equine stock classes, with the equineRSU values calculated using equine-specific models. Methods. Weighted average estimates of the bodyweight for the different equine livestock classes were calculated from the published literature. These weighted average estimates of bodyweight were used to estimate the energy requirements on the basis of data published by National Research Council. The resulting dry-matter intake and N intake from the equineRSU values and the current RSU values in use within Overseer® were modelled using published data on diet composition, crude protein content and the digestibility of the different feeds offered. Results. The current RSUs in Overseer were 2.5–6.8 units higher than the equineRSU values obtained from the equine-specific models. This overestimation in feed demand resulted in N-intake estimates at an animal level being 52–108% higher than values derived using the equine-specific estimates. Conclusion. The use of RSUs based on linear scaling of feed demand from ruminants on the basis of liveweight overestimates feed demand and N intake in horses. If horses are to be included within nutrient management models, feed demand must be based on published equine data for energy requirements to avoid over-inflation of N excretion. The equineRSUs calculated in this study reduce the risk of over-inflation of N intake and excretion, and subsequently the N leaching estimations. Implication. Failure to accurately model feed demand of horses within nutrient management software would unfairly compromise stocking density and horse management on large commercial breeding farms. The implication for these errors on economic impact and restricted livestock number is greatest for the Thoroughbred breeding industry due to the scale of the operations.
dc.description.confidentialfalse
dc.edition.editionJan 2024
dc.identifier.citationChin YY, Back PJ, Gee EK, Horne DJ, Rogers CW. (2023). Quantification of relative stock units for horses to permit correct application within pasture-based production systems. Animal Production Science. 64. 1.
dc.identifier.doi10.1071/AN22441
dc.identifier.eissn1836-5787
dc.identifier.elements-typejournal-article
dc.identifier.issn1836-0939
dc.identifier.numberAN22441
dc.identifier.urihttps://mro.massey.ac.nz/handle/10179/69707
dc.languageEnglish
dc.publisherCSIRO Publishing
dc.publisher.urihttps://www.publish.csiro.au/AN/AN22441
dc.relation.isPartOfAnimal Production Science
dc.rights(c) 2024 The Author/s
dc.rightsCC BY 4.0
dc.rights.urihttps://creativecommons.org/licenses/by/4.0/
dc.subjectanimal production
dc.subjecthorses
dc.subjectmodelling
dc.subjectnitrogen
dc.subjectnitrogen intake
dc.subjectnitrogen leaching
dc.subjectnutrient budget
dc.subjectnutrient management
dc.subjectnutrition
dc.titleQuantification of relative stock units for horses to permit correct application within pasture-based production systems
dc.typeJournal article
pubs.elements-id478958
pubs.organisational-groupOther
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