Breeding hoggets is a potential means of increasing the lifetime reproductive performance compared with traditionally breeding ewes first as two tooths (2-years old). An issue with hogget breeding is the low reproductive performance which has been highlighted in a previous post, with similar results when hoggets were bred alongside mature ewes.
Vasectomised rams or 'teaser rams' have been used to increase breeding activity early in the breeding season. Exposure of hoggets to teaser rams in previous studies have shown to have limited effect. So the aim of the studies summarised in this post was to consider both teaser ram use and feeding levels prior to the breeding period.
Key Points
The use of teaser rams advanced the onset of puberty in hoggets.
Exposing hoggets to teaser rams increased the proportion of hoggets pregnant early in the breeding period.
Farmers should consider ensuring their hoggets are gaining live weight, rather than maintaining it, to achieve a greater response from teasing.
Keywords: #hogget #hoggetbreeding #teaserrams #hoggetperformance
Puberty Attainment
There were 160 Romney ewe hoggets each year (2008 and 2009) blood sampled to determine puberty attainment by progesterone concentrations (greater than 1ng/ml = puberty attained).
The graph below shows the effect of Teased vs Unteased hoggets on the puberty attainment in the first breeding period (17 days after ram introduction) or the entire breeding period (34 days after ram introduction). This was repeated over two years, 2008 and 2009.
In the first year, there were more teased hoggets that reached puberty in the first breeding period compared with the unteased hoggets. However over the entire 34 day breeding period, this difference was no longer observed.
In the second year (Graph 2), there was a difference between treatment groups (Teased vs Unteased) in both the first breeding period and across the entire breeding period. In both periods a greater proportion of the teased hoggets attained puberty than the unteased hoggets. This shows that the use of teaser rams may advance the onset of puberty.
Teaser Use and Feeding levels
This study compared different feeding levels along with using teaser ram or not prior to breeding.
Treatment groups
Control-Low: No exposure to rams prior to breeding, pastoral feeding conditions to achieve live weight gains of 0-0.1kg/day (n=73)
Control-High: No exposure to rams prior to breeding, ad libitum feeding to achieve liveweight gains of >0.2 kg/day (n=75)
Teased-Low: Joined with 3 teaser rams, pastoral feeding conditions to achieve live weight gains of 0-0.1 kg/day (n=74)
Teased-High: Joined with 3 teaser rams, ad libitum feeding to achieve liveweight gains of >0.2 kg/day (n=73)
After the treatment period, all hoggets were joined together and bred with 4 Cheviot Rams over two 17 day breeding cycles. Following this they were managed as a commercial flock together and pregnancy diagnosed around 80 days after the first introduction of the ram.
Graph 2 below shows the percentage of hoggets marked by the ram in either breeding period, both breeding periods or were not marked at all during this 34 day period. The letters indicate significant difference between groups.
A greater number of Teased-High (high feeding level and teaser ram use) were marked (54.7%) during the first breeding 17 day breeding period. The hoggets that had no exposure to the teaser rams had a similar number marked in the first breeding period, 23.3% and 24.0% for Control-Low and Control-High, respectively.
Although there appears to be a difference in the number of hoggets marked by the ram in the second breeding period, the study found no statistical difference. This could have been a result of the data being analysed as log transformed data.
Interestingly, the hoggets in the Teased-Low group had the highest proportion of ewes with no mark. This shows that it is important for hoggets to be increasing live weight over the mating period.
The pregnancy diagnosis results are presented in the graph below. The proportion pregnant in the first 17 day cycle were tested as well as the total pregnancy rates.
The Teased-High group had the highest pregnancy rate in the first cycle and the Control-Low group had the lowest. However, over the entire breeding period there were no significant differences, with Teased-High showing slightly higher pregnancy rates.
Exposing hoggets to teaser rams increases the proportion of hoggets pregnant early in the breeding period. The results also indicate that farmers should consider ensuring their hoggets are gaining live weight at approximately 0.2 kg/d, rather than maintaining it, to achieve a greater response from teasing.
Both of these studies show that the use of teaser rams can advance the onset of puberty and increase pregnancy rates early in the breeding season, however, the overall reproductive rate of hoggets in the second study remained between 60-70%. So even though teasing increases the number bred in the first cycle, many of the remaining hoggets are still failing to conceive which could be due to other unknown reasons not related to puberty attainment.
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