Investigating associations between lamb survival to weaning and dam udder and teat scores

Abstract

Aims: To examine a range of udder and teat traits in Romney ewes and to describe the frequency with which different scores occur, and to investigate associations between lamb survival to weaning and ewe udder and teat scores. Methods: Mixed-age, mature Romney ewes (n = 1,009) were enrolled from a commercial sheep flock located in the Wellington region of New Zealand in January 2017. A range of udder and teat traits were scored in all ewes, using visual assessment and palpation, at pre-mating (February), pre-lambing (October), docking (November) and weaning (January 2018). During the lambing period each newborn lamb was matched to its dam, with lamb mortalities recorded until weaning. Associations between udder and teat scores and lamb survival to weaning were examined using multivariable models for each udder-scoring time. Results: Records from 981 ewes and 1,822 live-born lambs were included in analyses, with 252 (13.8%) lambs recorded dead between birth and weaning. Lambs born to ewes with pre-mating udder scores of lump or hard had 4.9 (95% CI = 2.6-9.6, p = 0.003) and 3.0 (95% CI = 1.5-6.1, p < 0.001) increased odds of failure to survive to weaning, respectively, compared with lambs whose dams had normal udder scores. Lambs born to ewes with mastitis at docking or weaning had 3.0 (95% CI = 1.5-5.9, p = 0.001) and 3.9 (95% CI = 1.3-11.6, p = 0.013) increased odds of failure to survive to weaning, respectively, compared with lambs whose dams did not have mastitis. Offspring of dams with asymmetrical udders at docking or weaning had 3.3 (95% CI = 2.2-4.9, p < 0.001) and 2.5 (95% CI = 1.5-4.0, p < 0.001) increased odds of failure to survive, respectively, compared with lambs whose dams had symmetrical udders. Conclusion and Clinical Relevance: Pre-mating udder palpation scores of hard or lump were associated with increased odds of lambs not surviving to weaning compared with normal scores, and could be used to identify ewes that are likely to be unsuitable for retaining in the breeding flock. Farmers could also use clinical mastitis scores and udder symmetry scores at docking or weaning to identify ewes whose lambs had greater odds of failure to survive to weaning. However these scores do not provide an indication of future performance, therefore further investigation into the impact of the present season's score on future seasons' lamb survival is required.

Associations between lamb growth to weaning and dam udder and teat scores

“…However these relationships varied between traits and management times. Similarly, we found that the relationship between lamb survival and udder and teat scores varied between traits and management times (Griffiths et al 2019).…”

“…If farmers wish to identify ewes whose lambs are predicted to have poorer performance, the results of the present study indicate pre-mating udder palpation score would be an appropriate trait to assess. When combined with the results of our analysis of traits associated with lamb survival (Griffiths et al 2019), these results indicate that offspring of ewes with premating udder palpation scores of hard have greater odds of failure to survive to weaning, and, should they survive, have lower growth rates to weaning compared with offspring whose dams had normal udder palpation scores.…”

“…In our companion article, we report the frequency of different scores for udder traits in ewes on four occasions between mating and weaning (Griffiths et al 2019). We also found that lambs born to ewes with poor udder scores had lower survival to weaning than lambs born to ewes with desirable udder scores.…”

“…The present study utilised data collected during 2017 from mixed-age, mature Romney ewes (n = 1009) that were born in 2013 or 2014 and were part of a commercial sheep flock located near Masterton, in the Wellington region of New Zealand. The enrolment, general and reproductive management of the study flock is described in Griffiths et al (2019).…”

“…The udders and teats of all ewes were scored immediately prior to the start of mating (pre-mating), 11 days before the planned start of the lambing (pre-lambing), and at docking and weaning. The system used for scoring is described by Griffiths et al (2019) and is summarised in Table 1. Due to the small number of ewes in some categories, some scores were subsequently combined for analyses, as described in Table 1.…”