Factors affecting ewe longevity on sheep farms in three European countries

Abstract

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Ewe Wastage in New Zealand Commercial Flocks: Extent, Timing, Association with Hogget Reproductive Outcomes and BCS

“…Productive longevity is the ability of a ewe to survive and be productive until she is culled for age. In New Zealand commercial flocks, the age at which ewes are culled for age varies between farms, but is typically approximately six to seven years of age [ 1 ], similar to flocks internationally [ 2 , 3 ]. Ewe wastage is defined as the combination of both on-farm mortality and premature culling [ 4 ].…”

“…Increased ewe wastage results in a reduction in farm productivity and subsequent ability to generate profit [ 1 , 4 ]. However, there is limited research on actual wastage rates and causes in commercial ewe flocks in New Zealand [ 1 ] and internationally [ 2 , 5 , 6 ]. To maintain consistent breeding ewe flock numbers, replacement ewe lambs (hoggets) are required, with numbers of replacements needed equaling the combined annual total of ewes that are culled for age and ewes that are lost due to wastage.…”

“…Therefore, flocks that have higher ewe wastage rates require an increased proportion of replacement hoggets. Rearing additional replacement hoggets to a productive age (or purchasing additional replacements) incurs a number of costs [ 1 , 2 , 7 ], including fewer sale lambs, increased management and feed costs, reduced selection pressure, potential biosecurity risks and increased greenhouse gas emissions. In addition, the reproductive performance of ewes increases as they age [ 8 ], so having an unnecessarily high proportion of younger ewes in a flock, due to increased wastage, reduces overall flock productivity due to a lower average flock age [ 1 ].…”

“…It is important to note variability and potential inaccuracy in recording wastage rates in extensively managed commercial flocks [ 2 , 5 ]. This is likely due to farm topography and flock size, farm management structure, degree of human contact with individual ewes within the flock, and perceived likelihood of wastage [ 11 , 12 , 13 ].…”

“…To the authors’ knowledge, there are no published reports directly examining the premature culling policies in New Zealand commercial flocks. However, it is likely that ewes are culled for similar reasons as reported internationally, namely known poor performance (for example non-pregnant), predicted poor performance (for example ewes whose lambs are predicted to have poor survival), or poor ewe health [ 2 , 6 , 22 , 23 , 25 ].…”