Dr. Nóirín McHugh, Teagasc asked the question “how many lambs is too many?” at the ICBF & Sheep Ireland Genetics Conference which took place Friday 17th of January 2020 in the Heritage Hotel, Killenard, Co. Laois.
To view Norin’s presentation click here
Some of Dr McHugh’s take home messages were:
- Number of lambs born (NLB) accounts for approximately 24% of the makeup of the Replacement indexes
- Currently a linear economic value used whereby for each 0.1 increase in NLB is worth €18.69 in the Replacement Index
- The question arises is there an optimum NLB in terms of farm profitability and if so what is this level
- Data from the Teagasc bio-economic model has shown that the optimum NLB is 2.18
- A new non-linear economic value will now be introduced in the Replacement Index which will cap the economic reward given to any animal at a maximum of 2.18 lambs
- New traits that can help to predict an animal’s NLB were also investigated, these include pregnancy scan data, barren rate and ewe weight and body condition score at mating
Number of lambs born (NLB) is one of the key drivers of profitability in sheep systems and accounts for approximately % of the makeup of the Replacement indexes. Currently there is a very strong relationship between a rams breeding value for NLB and the overall replacement index. In the current index, there is a linear economic value used whereby each 0.1 increase in NLB is worth €18.69. This means that animals with very high litter sizes have the potential of being over-valued in the genetic evaluations. The question arises is there an optimum NLB in terms of farm profitability and if so what is this level. Using data generated from the Teagasc bio-economic model developed by Alan Bohan which takes in accounts factors such as mortality, the number of lambs reared per ewe (cross fostered), the number of lambs sold as pets, the labour requirement and ultimately number of lambs weaned, the results showed that the optimum upper limit for number of lambs born is 2.18 lambs. This means that in the future a non-linear economic value will now be used which will result in the economic reward given to animals with a predicted NLB greater than 2.18 lambs will be capped at that level. In addition recent genetic research has shown that the heritability of NLB is 11% which is greater than recent Irish estimates which will result in a greater accuracy associated with the breeding value for NLB. New traits that can help to predict an animal’s NLB were also investigated including pregnancy scan data, barren rate and ewe weight and body condition score at mating. All of these traits will help to predict more accurately the genetics of ewe reproduction.