Ram percentages: why 1% + 1 isn’t always the right number of rams.
by Regulin Russ [Davis]
Generally speaking, ram percentage can be determined by testes size X number of rams = semen required. Not always easy to calculate. The challenge with ram percentages comes about when we calculate costs vs. returns based on numbers, but without factoring in ram and ewe behaviours.
Things to consider:
- Scanning results of more than 5-8% dry ewes and mostly late conceptions can indicate insufficient ram numbers.
- A significant amount of data indicates that 15-25% of rams show no interest in ewes displaying oestrus. There is also data to show that ewes are selective about the rams they will stand for (J.A. Abecia et al./Applied Animal Behaviour Science (2005) 355-361). The easiest way to compensate for this is to increase ram percentage.
- If using synchronisation or fertility treatments (Regulin, teasers, etc.) the ram percentage must be sufficient to capture the ewes when they are all cycling or the opportunity for early conceptions and thus a compressed lambing is lost.
- Ram percentage for younger, inexperienced rams needs to be increased to compensate for their tendency to re-join with the same ewes and for their smaller testes size.
- Ewe lambs also need a higher ram percentage as their expression of oestrus is more difficult to detect by the ram; and they are open for a shorter period of 12-18 hours, compared to 24-36 hours in older, sexually-experienced ewes.
- In addition to ewes being in anoestrus, even older rams have smaller testes during anoestrus (out of season). Testicle size increases with shorter days and longer nights, when more melatonin is naturally produced. Research from the University of Sydney (Prof. Simon deGraaf, et al) showed a significant increase in testicle size and in sperm production, in rams treated with melatonin (Regulin).
Therefore we recommend treating both ewes and rams with Regulin 30-40 days prior to early or out of season joining and a ram percentage of 2-3% for maximum results.
For more information check out the presentations on our website: regulin.com.au/ceva-university