This is a brief paper published in the New Zealand Society of Animal Production conference proceedings looking at the reproductive success of hoggets and mature ewes. There has been a bit of research done around hogget breeding, however, few studies consider hoggets bred together alongside the mature ewes.
Hoggets bred at the same time as mature ewes had lower reproductive rates.
In the first cycle (first 17 days of the breeding period) a greater percentage of mature ewes were bred compared with hoggets.
In the second cycle a greater percentage of hoggets were bred compared with mature ewes.
Often hoggets are bred at 7 to 8 months of age, one month later than mature ewes to provide the hogget with enough time to reach puberty. Puberty is influenced by age, live weight and daylight hours.
Hogget breeding can have a few benefits. These include:
increased net profit from lamb production
improved spring pasture utilisation
improved ewe lifetime performance
improved flock reproductive rate
increased rate of genetic gain, if you keep replacements from these hoggets as outlined in this post
However, there are also a few limitations to hogget breeding:
lower lambing percentage
lower lamb birth weights
lower lamb survival
Therefore, the later breeding of ewe lambs allows the maximum proportion of ewe lambs to have reached puberty and thus potentially increase pregnancy and lambing rates.
The objective of the current study was to compare aspects of reproduction of mature ewes and hoggets when bred together to aid in identifying where potential is lost in breeding hoggets.
Mature ewes and hoggets were bred to the same rams during the same breeding period.
At the start of the breeding period, 20 entire Romney rams, fitted with mating harnesses, were introduced at a ratio of 1:40.
Figure 2 below shows the percentage of mature ewes and hoggets that were bred during the first and second breeding periods. Mating harness crayon colours were changed on day 17 (first breeding period) so that the percentage bred during each period could be determined.
Majority of the mature ewes (95.7%) were marked by the ram in the first breeding cycle. The remaining mature ewes were marked in the second cycle (1.3%) or were unmarked (2.0%).
Hoggets had a lower percentage bred in the first breeding period (43.5%) when compared with mature ewes. However, there were still more hoggets bred in the first breeding period when compared to the second breeding period (24.3%).
A similar percentage of hoggets were unmarked (26.8%) to those hoggets that were bred in the second breeding period.
These unmarked hoggets most likely had not reached puberty, therefore, had not been marked by the ram.
It is likely that the hoggets were of adequate live weight.
The average live weight at the start of the breeding period of the mature ewes was 66.7 kg and of the hoggets was 46.1 kg (Figure 2).
This average hogget live weight is above the recommended individual hogget live weight for breeding of 40kg, hopefully indicating that most of the hoggets are above 40kg.
The figure below shows the results from pregnancy diagnosis at 80 days after the start of the breeding period. There was a greater percentage of hoggets non-pregnant (26.5%) compared with mature ewes. The number of non-pregnant hoggets and the number of hoggets that were not marked by the ram during the breeding period were similar.
This is to be expected as there was likely to be a number of hoggets that did not reach puberty by the mature ewe breeding period, even if they were at target live weight (40kg). This is why hogget breeding is often delayed until May, to ensure more hoggets have reached puberty, to increase the chances of becoming pregnant.
The majority of the pregnant mature ewes were multiple-bearing, whereas, most of the pregnant hoggets were single-bearing (as seen in Figure 3 below).
The authors concluded that the failure to be bred, high return rates and lower pregnancy rates of hoggets are limiting the use of hogget breeding, even when live weights are adequate. They recommended that hoggets are not bred until May.
However, in this study both the mature ewes and hoggets were bred together. It would be interesting to see if the same pregnancy rates would occur if the hoggets were bred separately to the mature ewes but at the same time (i.e. same breeding period). This would determine if the hoggets had not reached puberty or perhaps the rams were prioritising the mature ewes.
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Corner R, Blair H, Morris S, Kenyon P. 2013. BRIEF COMMUNICATION: A comparison of aspects of the reproductive success of ewe lamb and mixed age ewes joined over the same period. In: Proceedings of the New Zealand Society of Animal Production. p 76-78.