150% Lamb Crop Challenge
There are times in life when someone says something that you remember forever. The quote sticks with you and the person that said it may not even remember or recall the conversation. One of these instances happened to me when I was in high school.
My father and I had just finished working lambs. We weaned an 85 percent lamb crop. I was proud of this set of sheep because we raised show lambs from this group of ewes. I commented to my father “This was a good year and we raised some good show prospects.”
In a disappointed tone, my fathers said, “We can raise an 85% calf crop and do not have to fight predators and parasites. They’ll have to do better than that, if we want to continue to raise sheep after you are done showing lambs.”
This was a punch in the gut for me! I thought the ewes raised award winning lambs; therefore, they “must” be superior animals. But he was absolutely right! Commercial sheep that can consistently raise twins are far more profitable than sheep that consistently raise singles. Raising show lambs requires a completely separate set of selection criteria.
Most years in Texas, the average lamb crop is ~80 percent and the average kid crop is ~100 percent. While predation is a major problem, it is a separate issue and predation shouldn’t always be the “scapegoat” for a poor lamb or kid crop.
Selection of sheep or goats for their ability to raise twins should be a priority but can be a challenge. For most range operations, ranchers don’t know which animals are twins and singles. Plus, other factors influence the chance a dam has a single or twin, such as age of ewe and nutrition. These challenges can be overcome but it requires years of accurate data collection.
One approach to select for twins on range lambing operations is to pregnancy ultrasound the ewes and sort them into twin and single-baring pastures. Then select for replacements from the twin pasture. We have been working with a group of ranchers as a case study. This project was funded by an American Sheep Industry’s Lets Grow program and is title “The 150% Lamb Crop Challenge.”
Five different range sheep operations participated in the program representing nearly 3,000 sheep. On average, 30 percent of the ewes were carrying twins the first year. Four of the five ranches scanned in the 25 to 35 percent twins depending on pasture and age of ewes. Ranch #4 was an outlier and nearly half of the ewes were carrying twins. An obvious difference was this ranch selected smaller-framed replacements and emphasized fertility.
Four ranches scanned all the ewes again the following year. The ewes that were twins the prior year were 10 to 20 percent more likely to have twins the following year. For instance, all ewes at Ranch #4 scanned at 47 percent twins the first year. The twin lambing ewes scanned at 60 percent twins the second year.
At weaning most ranches reported a 20 to 40 percent increase in number of lambs weaned in the twin vs single pastures. However, the ranch with the 50 percent twins scanning also had the highest weaning differential (80%) between twin and single pastures. This was likely due to years of selection for fertility. Variations in weaning rate by year and pasture were thought to have occurred from predation and drought. But, there were serious concerns by the ranchers that their ewes were not properly caring for twins-born compared to single-born lambs.
While, we would have liked to have seen consistently larger lamb crop in the twin ewe pastures. And we wish that ewes who give birth to twins in 1 year, consistently rear twins every year. Nevertheless, the early stages of this project indicate that there is potential for an improved lamb crop using pregnancy scanning.
There are other tools to select for sheep and/or goats that consistently rear twins. Most notably, estimated breeding values (EBVs) are accurate predictors of genetic potential for an improved weaning rate; however, it requires a full sheep generation for rams to sire daughters that are kept back in the flock. Ultrasound works faster and can be used in combination with EBVs to reach a 150% lamb crop faster.
To provide feedback on this article or request topics for future articles, contact me at reid.redden@ag.tamu.edu or 325-653-4576. For general questions about sheep and goats contact your local Texas A&M AgriLife Extension Service county office. If they can’t answer your question, they have access to someone who can.