Differences in lambing performance between ewes and hoggets
Updated: Apr 26, 2020
Farmers are increasingly breeding their hoggets to increase ewe and farm productivity and reduce the non-productive period of the ewe’s lifetime. Hoggets are commonly bred later than the mature ewes, to increase their likelihood of attaining puberty prior to breeding, and to ensure lambing occurs during the spring pasture flush. They are also commonly bred to different rams.
It has been reported that lambs born to hoggets are smaller at birth and at weaning and have lower rates of survival. However, due to the differences in lambing time and rams used, direct comparisons can’t be made. Thus, there is little comparable information about the lambing performance of mature ewes and hoggets. This study was a preliminary step in breeding lambs to be selected as replacements born to mature ewes and hoggets.
Emma Pettigrew is looking at selecting replacements that are born to ewe hoggets for her PhD studies. She has written an article for us a few month back (check it out here). This week she has written a new article to promote the results from a study comparing the lambing performance of mature ewes and hoggets, bred to the same rams.
There were fewer lambs born per hogget bred than per mature ewe bred
Lambs born to hoggets were smaller at birth and weaning
Lambs born to hoggets had lower rates of survival
Selecting the best lambing paddocks (grass and shelter) for hoggets to lamb in should improve lamb survival and maximise lamb growth to weaning
This study used:
1100 mature ewes
40 mature rams
Ewes and hoggets were managed as one group and joined with the rams on the 10th of May 2017. The rams were left in for two reproductive cycles (17 days each). After this 34 day period, the mature ewes were removed, and the hoggets continued with the ram for an additional 10 days to give them the best chance of getting pregnant.
After breeding, the mature ewes and hoggets remained separate, so the hoggets could be preferentially fed to meet their growth targets.
The mature ewes were heavier than the ewe lambs throughout the experimental period, as seen in Figure 1.
The mature ewes had greater body condition scores at pre-breeding and mid-pregnancy, as seen in Figure 2. At pre-lambing, the hoggets had a greater body condition score than the mature ewes. At weaning there was no difference between the two ewe age groups for body condition score.
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Understandably, there were large differences in the proportion of the mature or hogget flock that were multiple-bearing, and that conceived during the first breeding cycle (17 days).
Overall, 94.7% of the mature ewe flock conceived during the first cycle, and only 1.4% of mature ewes were dry, as seen in Figure 3. Meanwhile, 19.8% of hoggets conceived in the first cycle, 26.9% conceived in the second cycle, 15.7% conceived in the third half cycle, and 37.5% were dry, as seen in Figure 3.
The total number of lambs born per ewe bred was 183% for mature ewes and 70% for hoggets, as seen in Figure 4.
Based on these results, it was concluded that the ewes held dominance over the hoggets for the attention of the ram during the first cycle. Hoggets are known to be more shy towards the ram than mature ewes. Once the majority of the mature ewes had conceived during the first cycle, the hoggets had the attention of the rams for the remaining cycles.
Hoggets are also less likely to have attained puberty, and therefore be cycling during the breeding period. This is likely why there was a much higher percentage of hoggets being dry after a longer breeding period than the mature ewes.
Lambs born as singles to mature ewes were the heaviest at birth, docking and weaning, as seen in Figure 5.
Twins born to mature ewes were the next heaviest at birth. Triplets born to mature ewes were similar in weight to singles born to hoggets at birth, being the third heaviest, and twins born to hoggets were the lightest at birth.
Twins born to mature ewes and singles born to hoggets were similar, and second heaviest at docking and weaning. Triplets born to mature ewes and twins born to hoggets were similar, and the lightest at docking and weaning.
*Note, as there were only two sets of triplets born to hoggets, they were not used in the analysis.
Lambs born to hoggets were less vigorous than lambs born to mature ewes at tagging, as seen in Figure 6.
The score used was:
No struggle during tagging and restraint
Moderate struggle during tagging and restraint
Regular struggle during tagging and restraint
Even when adjusted for birth weight (as lighter lambs are less vigorous, and hogget-born lambs are lighter at birth), there was still a difference between the groups. This suggests that there is something other than just birth weight affecting the vigour of the lambs at birth, resulting in hogget-born lambs being less vigorous.
The conclusions from these studies are that hoggets had lower reproductive rates than mature ewes. Lambs born to hoggets were lighter at birth, docking and weaning than lambs born to mature ewes. This highlights the need for farmers to ensure hoggets are heavy enough at breeding to maintain a pregnancy, and successfully wean a lamb.
This study also compared survival rates of lambs born from mature ewes or hoggets based on their birth weights. We've decided to separate this post out into another summary (coming soon!). Make sure you are subscribed to our emails to get notified straight away!
Pettigrew, EJ, Hickson, RE, Blair, HT, Griffiths, KJ, Ridler, AL, Morris, ST and Kenyon, PR. 2018. Differences in birth weight and neonatal survival rates of lambs born to ewe hoggets or mature ewes. New Zealand Journal of Animal Science and Production 78, (16-20).
Pettigrew, EJ, Hickson, RE, Blair, HT, Griffiths, KJ, Ridler, AL, Morris, ST and Kenyon, PR. 2020. Differences in lamb production between ewe lambs and mature ewes. New Zealand Journal of Agricultural Research, In Press.