2018 WA Lambing Survey

Results

Participants in the survey were sheep producers operating within the medium rainfall zone (MRZ) or cereal-sheep zone (CSZ).

• The cereal-sheep zone (CSZ) extends from the Geraldton area in the north west to the Esperance region in the south east. This is often known as the wheatbelt.
• The medium rainfall zone (MRZ) includes the whole south west, from the Perth area in the north, to Albany in the south. This was often known as the woolbelt.

Seventy one percent of ewes were Merinos mated to Merino sires, 27% were Merino ewes mated to meat sires and 6% were meat breeds. There were a greater number of participants in the Medium Rainfall zone although the proportion of producers listed by ABS (2016) shows that 1400 sheep producers are in the MRZ and 3072 sheep producers are in the CSZ - a one-third to two-thirds split between the two production zones. There was a large difference in the number of sheep represented in the survey between zones (Table 1) and for this reason, data is presented within these zones to allow a legitimate comparison.

Pregnancy scanning data for multiples was collected where available; however, there were only 34 Merino matings flocks, 10 Merino to meat sires flocks and four meat flocks with complete data. The reproductive rate (# of foetuses/ewe scanned) for Merino matings ranged from 101% to 148%; Merino to meat sire matings from 115% to 148% and meat matings from 107% to 170%.  These reproductive rates are within the average of WA flocks (Butcher, 2018).  The CSZ had a higher average reproductive rate than the MRZ however only 10 flocks were represented in the sample.

Merino flocks

The CSZ had a slightly higher marking than the MRZ in Merino flocks (Table 2).  Marking rates were calculated using the number of lambs marked to the number of ewes joined. Overall the median and average of the zones combined was 91%.

Figure 1 shows the significant variation in Merino marking rates between flocks. A similar spread in marking rates was observed in 2017 (WA Producer survey 2018, unpublished). The average and median marking rates were also very similar in the 2017 season (Table 3)

Figure 2 Merino lamb marking rates showing zones and month of lambing in 2018 (months with less than four flocks were omitted)

Merino producers in the CSZ tended to lamb earlier than the MRZ and the peak marking rate was in May with slightly lower rates in the months either side. Merino producers in the MRZ lambed later with a peak in marking rates in July – August (Figure 2). This is reflected in the larger 2011 Producer survey (Jones & Curnow 2012) and the 2018 Producer survey data (unpublished).

Crossbred flocks

The marking rate for crossbred flocks in the CSZ (97%) was significantly higher than that of the MRZ (88%) although the reproductive rate was similar (albeit from a small sample), indicating that the survival of lambs from scanning to marking in many flocks was considerably better in the CSZ (Table 4). This may indicate that either more benign weather conditions at lambing or better nutrition of the ewe leading up to lambing led to better lamb survival.  In poor seasons, particularly when feed is limiting leading up to and during lambing, the lamb has lower birthweight, and therefore body reserves, leaving it vulnerable to exposure and starvation on the birth site (Oldham et al, 2011).

The histogram of marking rates (Figure 3) shows a similar range of marking rates to the Merino matings but the poorer rates are predominately from the MRZ. The median values for each zone reflect the average value at 0.97 for the CSZ and 0.89 for the MRZ.

Figure 3 Merino-to-meat sires (crossbred) marking rates as a proportion of respondents in 2018

Marking rates in the MRZ for the 2018 season were significantly lower than in 2017 (Table 5) and with a reasonable sample size (113,000 ewes) and 65 flocks represented in 2018, we can assume that this is reflective of the broader situation in the zone.

In the MRZ, later lambers achieved higher marking rates than earlier lambers (Figure 4). In the CSZ, July recorded the lowest marking rates for crossbred flocks.  This appears to be in line with other years and other seasons.

Figure 4 Crossbred lamb marking rates showing zones and month of lambing (months with less than four flocks were omitted)

Meat flocks

A smaller number of sheep were represented in the meat matings (~30 000 ewes) spread over 27 flocks (Table 6).  Only four of these flocks were scanned for multiples with one flock at 107% and the rest at 150, 155 and 170%. The flock with 107% reproductive rate and a resulting 65% marking was in the worst hit area for pasture production in both 2017 and 2018. Other producers in the area reported a drop of up to 30% on their average marking rates.

Figure 5 The range of meat-to-meat marking rates as a proportion of respondents in 2018

Meat marking rates in the CSZ at 1.09 for the 2018 season were higher than in 2017 (Table 7) and had a higher median score of 1.04, however, the smaller sample size in 2018 limits our interpretation of the situation.

The time of lambing for meat producers is much less defined than other of other enterprises, the WA Producer survey 2018 showing a fairly even spread from March through to September.  Due to the low numbers in the survey, it was not possible to analyse the results on time of lambing by region, however, there was a general trend of higher marking rates later in the season.

Overall impacts

Lambing marking data is not regularly collected on a large scale in WA. We therefore must rely on a sample of data that may mask some of the lower results; particularly in a poor season where producers maybe uncomfortable with sharing data that they see is not reflective of their usual results.

Grower groups in the worst hit areas such as RAIN, FEAR, Gillamii and LIFT showed the lowest marking rates, however, due to a lack of data from previous years and small sample sizes for those grower groups we aren’t sure how large the impact was (Table 9). Several members reported their lowest lambing season on record (up to 30% lower than average). Many reported issues around feeding ewes due to lamb and metabolic issues with several participants indicating that they believe they started feeding extra fodder too late.  Participants from other groups reported difficult conditions or a late start and indicated that they had fed significantly more supplementary feed at considerable cost or dispersed part of the flock to be able to cope with the extreme conditions.

Lamb marking rates are highly variable in any season across different regions and rainfall zones. This is due the fact that reproduction rates rely on principally nutrition management and secondarily on genetics. The systems and management that individual farmers use to manage lambing flocks have a significant impact, with many producers seeing little variation in rates from year to year as they adjust feed budgets and management to match the pasture production. Although some flocks have seen a significant drop in lambing rates where, for whatever reason, managers weren’t able to match nutritional needs, experienced poor lambing conditions or other issues, most producers still achieved an excellent result in challenging times.

The overall impact of the season on lamb production in 2018 will be significant in some areas but likely overall given the smaller drop in regions with larger flock densities.  It is estimated that the reduction in lamb production across the WA flock will be in the order of 4-7%.

References

R. Butcher, 2018. Southern WA reproductive rates, Ovine Observer October 2018

C. M. Oldham, A. N. Thompson, M. B. Ferguson, D. J. Gordon, G. A. Kearney and B. L. Paganoni 2011. The birthweight and survival of Merino lambs can be predicted from the profile of liveweight change of their mothers during pregnancy  Vol 51, APS.

M. Curnow, A. van Burgel, J. Bucat, A. Jones. 2011.   Western Australia Farmer Survey 2011, DPRID.