Original articleCan farmers reliably perform neonatal lamb post mortems and what are the perceived obstacles to influencing lamb mortality?
Introduction
Neonatal lamb mortality constitutes a significant economic cost, an obstacle to achieving efficient and sustainable lamb production and is an important welfare challenge (Binns et al., 2002, Sawalha et al., 2007, Dwyer, 2008).
Neonatal lamb mortality is defined as the death of lambs during the first week of life with the predominant risk period being the first 48 h. Overall lamb mortality between scanning and sale ranges from 10 to 25% (Mellor and Stafford, 2004) but in the author’s experience, it can as high as 30–40% on some farms. Typically 5.9–12.5% of scanned lambs are lost between 0 and 48 h old (Binns et al., 2002). Key causes of neonatal lamb mortality include stillbirth, hypoxia due to dystocia, starvation, hypothermia, injury secondary to dystocia or mismothering and infectious disease such as watery mouth (Dwyer, 2008).
Risk factors leading to these causes of deaths include low birth weight, high birth weight, poor maternal body condition, lamb vigour at birth, underlying deficiency i.e. selenium or iodine, dystocia, ewe with poor mothering ability andpoor hygiene (Mellor and Stafford, 2004). Multi-level modelling has identified farm and management risk factors which are linked to increased risk of lamb mortality such as outdoor lambing, less frequent renewal of bedding in pens, larger flocks and flocks with higher replacement rates. Factors such as housing ewes and supplementing thin ewes were found to be protective (Binns et al., 2002). Experience of the farmer, feeding frequency, provision of suckling assistance and use of lambing pens were found to be protective in an additional model (Holmoy et al., 2012).
Targets for lamb mortality for a lowland flock should be less than 14% between scanning and sale, made up of 6% from scanning to birth, 6% from birth to turnout and 2% from turnout to sale (AHDB Beef and Sheep Manual, 2015).
In 2014 a veterinary practice based lamb mortality survey of commercial flocks in South West England measured total lamb mortality between scanning and weaning, with the median found to be 10.4% (n = 30, range = 4.4%–20.8%) (unpublished data). Losses before turnout i.e. including pre-lambing and peri-lambing mortality represented the largest loss period in most flocks. Few flocks could attribute suspect or confirmed causeof loss to those lambs not surviving to weaning through their existing recording methods.
The variation in lamb losses demonstrated both in peer reviewed literature and in commercial flocks in this practice-based survey, highlights that low levels of lamb loss are achievable. Despite this and greater knowledge about causes and risks of lamb mortality, evidence for reduction strategies and the associated cost benefits, there has been no reduction in lamb mortality in the past 40 years (Dwyer et al., 2016).
Possible reasons for this lack of reduction suggested in the literature to be (a) lack of farm specific solutions, (b) dismissal of research results by commercial farmers due to use of non-commercial flocks in studies, (c) difficulty in applying the evidence base to commercial flocks given the complex nature of mortality or finally (d) lack of communication of the evidence base by advisors to the farmers (Dwyer et al., 2016).
This work also suggested that farmers felt ‘powerless’ to effect change and reduce losses within the first 48 h in the lambs life. They prefer to divert resources to latter stages of production where their efforts are perceived to be more effective (Dwyer et al., 2016). Other challenges to loss reduction could be perceived scale of investment in labour and resource necessary to reduce losses and underestimate of the level and cost of lamb mortality to a sheep business.
The variation in losses observed in the 2014 practice based survey suggested that generic lamb mortality advice has limited value when applying to sheep flocks, given (a) the diverse range of farming systems and (b) the diversity in main causes and timings of lamb losses. For example, not all participating flocks experienced peak lamb loss in the neonatal period, with post-turnout losses more significant for some.
Data collection on farm or lack thereof is often cited as a challenge for quantifying level of and causation of lamb mortality at all stages of production. The practice survey examined scanning and movement record data to compare potential lambs available for sale and actual number sold or retained within the flock. Mid production cycle figures such as numbers at first gather may enable crude assessment of specific phases of loss, but suspected cause of death is often challenging to obtain from flocks unless there is pre-existing farmer motivation to record. Furthermore, in our experience, unless there is a substantial increase in the level of morbidity and mortality in lambs, veterinary surgeons are rarely asked to routinely examine neonatal lambs for post-mortem, presumably because of (a) cost, (b) logistics and time of taking lambs to a collection centre and/or (c) lack of perceived benefit.
We hypothesised that equipping sheep farmers with skills and resources to enable them to define the specific causes of neonatal mortality on their own units can lead to generation of useful flock specific data.
Our hypotheses for investigation are:
- 1.
To evaluate whether a knowledge exchange solution can be accurately used to define risks by training farmers how to examine neonatal lambs post-mortem and follow a basic framework to record common causes of mortality
- 2.
To work with farmers and using the results to build up a farm specific picture of causes of mortality
To assess if trained farmers felt that the data was valuable in targeting lamb mortality for their flocks.
We measured our success in achieving these objectives by answering the following questions:
- 1.
Once trained by a veterinary surgeon, can sheep farmers reliably reach the same conclusion with regard to presumptive diagnosis as a veterinary surgeon?
- 2.
What were the common causes of lamb loss on each farm and how did these differ between units?
- 3.
Did the farmers use their findings to effect change?
Section snippets
Flocks
Five flocks were recruited to participate in the study. The flocks were convenience selected based on an expressed interest by the farmers to target lamb mortality as one of their annual key performance indicators, proximity to a central veterinary practice (within 40 miles of Synergy Farm Health Ltd), defining themselves as commercial sheep flocks i.e. lamb sales were a significant portion of farm revenue and lambing in Springtime. Four of the flocks were within Dorset and the fifth was in
Overall mortality
Total lamb mortality from scanning to end of lambing old ranged from 8% to 19% (n = 3, median = 11%). Two of the flocks did not have mid-production figures available. The total mortality scanning to sale ranged from 15 to 25% mortality (n = 5, median = 21%).
Quantitative analysis
A total of 96 lambs were examined via supervised PMs across five flocks in the presence of the investigator and an additional 40 lambs examined by farmers during unsupervised PMs. Supplementary samples were submitted from flock D as part of an
Discussion
We have demonstrated that farmers can post-mortem neonatal lambs which a high degree of agreement with a veterinary examiner and that this data does generate flock specific results.
Dwyer et al. (2016) identified the challenge for commercial sheep flocks in implementing and effecting change on commercial sheep flocks when considering lamb mortality. The lack of progress reported over the past forty years represents a substantial threat to ongoing animal welfare and the profitability of sheep
Conclusions
We have demonstrated that farmers can accurately identify key findings on post-mortem of neonates and use this data to generate flock specific information. Three out of four flocks could successfully achieve delivering over 10% of post-mortems and reliably identify cause of death. We consider that farmer PMs of lambs could be a tool for the veterinary-farmer team, facilitating the communication of farm specific advice and empowering farmers to effect positive change. Veterinary surgeons should
Conflict of interest
The authors declare they have no competing interests.
Acknowledgements
The work was funded by AHDB’s Farmer Innovation Grant (Animal Horticultural Development Board Farmer Innovation Grant). We thank all of the farmers who participated in this study. With thanks to Laura Randall (University of Nottingham) for providing statistical advice.
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