Sheep composites address needs of sheep industryWritten by Saige
Gillette – The USDA Agricultural Research Service (ARS) is developing a composite sire line that specializes in growth and carcass traits that are desirable in sheep.
“Livestock work for us. If they aren’t doing the job we ask them to do and aren’t utilizing the resources we give them, then we need to get rid of them,” said USDA ARS research leader Gregory Lewis at the Northeast Wyoming Sheep Symposium on Oct. 20. “We have to be able to link genetics, nutrients and reproductive efficiency to use them efficiently.”
Lewis explained to producers at the symposium a project that has created a new composite sheep to use as a terminal sire in extensive rangeland production systems.
The mission of the U.S. Sheep Experiment Station is to develop integrated methods for increasing production efficiency of sheep and to simultaneously improve the sustainability of rangeland ecosystems, and this recent project hopes to create a composite breed that will allow sheep producers to increase efficiency and profits.
Feeders, packers and pelt buyers all seek different qualities in sheep, and the ideal animal will meet the needs of each group, commented Lewis.
“Sheep feeders like to see fast growing lambs, and the packers like to see carcass merit and value. Pelt buyers are also concerned about pelt value, and white pelts tend to sell better than black pelts,” explained Lewis. “We developed this study with the goal of producing a white-faced terminal sire composite sheep.”
The study, currently being conducted in Dubois, Idaho at the U.S. Sheep Experiment Station, looked at Texel, Suffolk, Columbia and a U.S. Meat Animal Research Center composite breed and their reproductive abilities, efficiency and carcass qualities.
“We don’t care much about the individual rams,” added Lewis. “What we care about is the genetics in those rams.”
In evaluating reproduction, Lewis noted that Suffolk sired lambs were no more likely to survive or die than lambs sired by any other ram.
“From a survival aspect, we did not see penalty for a heavy weight lamb,” said Lewis, who added that smaller lambs are much more likely to die.
In general, Suffolk sired lambs outgrew the other breeds, and Texel sired lambs were always the lightest. Columbia sired lambs were smallest, after adjusting for body weight, with the lightest muscling.
Carcass analysis showed that, when adjusted for body weight, the Texel produced the largest loin muscle area (LMA), and Columbia sheep bottomed the category.
“In a composite breeding system, Texel could have advantages,” said Lewis. “Suffolk are also producing consistently large muscle areas.”
Lewis explained that because of a genetic mutation, called the myostatin mutation, Texel sheep are exceptionally well muscled.
In analyzing the carcasses, Lewis highlighted that there was a difference in where the animals ranked after adjustments were made for body weight. Efficiency provided another aspect for analysis of the breeds.
“We can produce large lambs that survive well and grow well,” said Lewis. “The question is, can they do it efficiently? Whatever we are putting in needs to be turned into output.”
Three methods were used to calculate efficiency: rate of gain to intake ratio, residual feed intake and residual gain.
Residual feed intake serves to determine the amount of feed intake that is independent of size and growth rate, according to Lewis.
“The idea is that we should be able to select animals that are big and grow fast with less feed,” explained Lewis. “It’s a good idea.”
Residual gain looks at the amount of gain independent of size and intake and is the method that the Hereford Association and Angus Association are moving toward.
“We are seeing that Suffolk are the most efficient of the lambs. They ate more than anything, but they grew a lot,” said Lewis. “Columbia came out on the bottom. Looking at RFI, the Suffolk started badly, got worse and then got really good. Texel started good and started to taper off, but the Columbia just continued to get worse.”
“We were pretty disappointed with the Columbia,” added Lewis.
The residual gain method showed Suffolk as most efficient and Columbia as worst, with the composite and Texel in the middle.
“We asked the question using the data that we have available, which of these lambs will make the most money for you in the feedlot?” asked Lewis. “The Suffolk and composites will earn you over $30 a head, with the Suffolk getting close to $40. The Texel about $27, and the Columbia will earn about $28. That’s quite a bit of money.”
Lewis also looked at the relationship between LMA and profits, saying that LMA does matter.
“For each standard deviation increase in loin muscle area, we calculated that we can increase dressing percentage by 1.57 points. We also saw an increase in gross carcass value by five dollars per carcass, and an increased box value of nearly seven dollars,” said Lewis. “If we started selecting on large loin muscle areas and growth, we will have an increase in value coming out of the feedlot and also an increase in carcass value.”
From the data collected on each breed, Lewis said that his team has started developing a composite line of sheep that will be three-eighths Suffolk, three-eighths Columbia and one-quarter Texel.
“Suffolk are good at growing, Columbia are better survivors, and the Texel will get the muscling,” said Lewis. “That cross will allow us to get rid of the black in the rams when crossed with a white-faced maternal line to produce a slaughter lamb.”
“We will compare this composite to the original breeds, and, based on our literature, it should be at least as good or better,” added Lewis.
Currently, the research team has about 300 composite lambs produced.
“They look really nice,” commented Lewis. “They are tall, thick, heavily muscled lambs.”
Lewis adds that the color of the lambs will take time to work out, but continued research will fix that issue.
Three manuscripts with the data from the project are currently being peer reviewed before being published in the Journal of Animal Science.