Sheep, Goat Producers Learn
About Innovative Technology

SAN ANGELO — Recent technological advances at the molecular level have allowed the livestock industry to look at gene differences to select and improve livestock. The ability to use this information is contained within DNA, and this DNA is being used to determine parentage.

Andy Laughlin, assistant sheep and goat specialist at the Texas A&M Research and Extension center here, is testing the validity of determining parentage in sheep flocks. Laughlin is a graduate student at Angelo State University. He provided an overview of his research work and some preliminary results during the recent annual sheep and goat field day at the research center.

The primary objectives of the study are to use DNA to determine parentage in a sheep group breeding system where, for example, a breeder may be using three rams in a select group of ewes, and to determine why some rams breed more and

have more progeny under the same environmental conditions.

"Today most registered operations use a single sire breeding scheme where one proven sire is used on one set of breeding ewes. If something happens to that one proven sire, you've lost all the progress you were trying to make," Laughlin explained. "Through the use of DNA we can actually breed multiple sires and still determine the parentage."

Lauglin is using two different study groups — an intensive group and a conventional group which represents the way in which the animals are lambed. The intensive study group represents those producers who jug lamb, for example. Lambing records on this group were kept every day. The conventional study group represented traditional pasture lambing practices. In this group, lambing records and pairing were done every few days.

Thus far, 64 of the 72 lambs in the intensive lambing group could be identified to their sires. Of the three sires used in the test, ram 2788 sired 29 lambs out of the 64 total lambs, or 40 percent; ram 2863 sired 25 lambs or 35 percent; and ram 6099 sired 10 lambs or 14 percent of the total. Sire determination is still pending on eight lambs, Laughlin said.

In the conventional group, 48 out of the 54 lambs have thus far been identified back to their sires. Ram 2888 sired 24 lambs or 44 percent of the total lambs born; ram 2856 sired 16 lambs or 30 percent; and ram 6863 sired six lambs or 15 percent. Sire determination is still pending on six lambs.

Laughlin noted that it is not uncommon for lambs to be mis-mothered. In general there's about a three percent chance, he said. In the case of this study, three lambs in the intensive group could not be matched to their dams while in the conventional group eight lambs were not matched to their dams.

As is the case with any new technology, cost can often be prohibitive, at least until supply and demand balance out. The cost to perform DNA analysis, Laughlin told listeners, currently averages about $60 per ram and another $25 per lamb, which includes DNA analysis on the mother as well.

DNA, the speaker noted, is also being widely used in the Texas validation program for animals participating in the major show circuit. In the case of sheep and goats, it is mandatory that animals be validated. Laughlin said he expects some 12,000 goats and 11,000 lambs, 28,000 hogs and 8000 steers will be validated this year in Texas.

DNA is also being used in embryo sex determination, and research geneticist Dr. Dan Waldron has initiated a marker-assisted selection research project. More long range uses for DNA include such things as gene mapping. There is already a good map for cattle and sheep, and researchers are in the process of mapping the human genome, Laughlin said.

Drs. Ed Huston and Chris Lupton initiated a research project two years ago in an effort to address some of the problems of the sheep industry in a more innovative way. The goal was the concurrent production of a lean lamb and high quality wool. That initial study has now been completed and the researchers summarized performance and cost production data for those attending the field day.

The study trial is centered around the use of a low-energy ration and a raised floor to determine if high quality wool can be produced concurrently with a high quality carcass.

A raised floor provides a cleaner environment, no parasites and no predation, Lupton explained. It's also cool in the summer and warm in the winter.

"We rationalized that by growing these lambs on this raised floor, we could produce cleaner fleeces and we also thought that by growing lambs out slower we could produce more uniform fibers and a more consistent product overall, both lamb and wool," Huston remarked.

Lambs went on test averaging 70 pounds and were four to six months of age. The goal was to keep the animals on feed until they were 12 to 13 months of age.

"We were not trying to maximize growth," he pointed out, "but rather make it a constant growth over a longer period of time. We wanted a 65-pound carcass, with two-tenths of an inch of backfat that had a quality grade of Choice or Prime and an average yield grade of 2.5.

To get a 65-pound carcass weight, the researchers reasoned that lambs needed to grow to 130 pounds; to do this, average daily gains needed to be about .33 pounds per head per day.

The goal for wool production, Lupton told listeners, was more than eight pounds of wool per animal, grease weight, with a yield higher than 60 percent, vegetative defect less than three-tenths percent, and staple length greater than 3.75 inches. Also, to truly be a premium product, the wool needed to be finer than 19 microns and it needed to be uniform, white, bright, and sound.

The researchers wanted to compare performance of animals in three settings — the raised floor, conventional feedlot and on the range with supplement. Lambs on the raised floor were fed a ration consisting of 85 percent oat hay, 10 percent wheat grain and five percent molasses pellet. This "oat" pellet was developed in Fort Stockton.

The feedlot animals were fed standard commercial feedlot rations while those on the range were fed a salt- limiting supplemental ration.

Half of the animals on test were Merino-Rambouillet crosses and the other half were straight Rambouillet lambs. Prior to the initiation of the study, all lambs were fed the same diet for four weeks to equalize their eating habits.

Huston outlined results from the lambs grown on the raised floor environment and made comparisons between the two different breed groups. The Merino cross lambs, which originated from Nevada, did not gain quite as well as the Rambouillet lambs, he said. It took the Merino lambs more days on feed to get to the desired slaughter weight, and even then they had a lighter slaughter weight which corresponded to a lighter carcass weight; yield was also less because the lambs weren't as fat, which also meant the quality grade on the lambs wasn't as good as they had hoped. The yield grade, however, was 2.17, which Huston said was more desirable than the yield grade on the Rambouillet lambs, which averaged 2.56.

The Merinos grew almost two pounds more wool grease weight or 1.7 pounds more clean wool than the Rambouillet. The Merinos' clean yield was also higher.

"We were disappointed, however, in the micron," Lupton told listeners. "The Merino wool averaged 21 microns while the Rambouillet averaged 19.7 microns across the board. Because of the high micron, the wool was more variable in terms of fiber diameter and the prickle factor was higher.

"We were also disappointed in staple length, which averaged only about two-tenths of an inch longer than the Rambouillet wool — 3.6 versus 3.4 inches."

The researchers also presented data which compared the difference between treatments. Lambs on the raised floor were kept on feed for more than 200 days to allow the wool to grow to a more desirable length. A mean unshorn body weight across both breeds was calculated to be 140 pounds for the raised floor lambs while those in the feedlot had an average body weight of 130 pounds. The average carcass weight for both treatments was 66.6 pounds, which Huston said was about on target, and the yield was 51 percent.

"What disappointed us was that the lambs on the raised floor did not stay lean even on this low energy diet," the researcher said. "They all graded Choice or Prime, which was essential, but they had yield grades higher than the 2.5 target."

"We fed that low energy ration thinking the animals wouldn't grow a lot of excessive fat. We learned that probably the only way we're going to have an impact on backfat is with genetics," Huston concluded.

Lambs on the raised floor grew more wool than those in the feedlot. Clean fleece weight was half a pound higher on the raised floor than in the feedlot.

"We were disappointed in the fiber diameter," Huston said. "We thought if we fed that type of diet that the fibers would be more uniform," he reiterated.

Researchers also looked to see if they could keep the wool even cleaner by putting "coats" on some of the lambs grown out in all three systems. Huston assumed that the rate of gain of coated lambs would be significantly less than that on uncoated lambs. In fact, lambs with coats actually had a higher rate of gain. Grease fleece weights were six-tenths of a pound less but yield was higher compared to uncoated lambs. The six-tenths of a pound difference, Lupton said, was simply due to dirt.

Extension risk management specialist Wade Polk provided cost of gain comparisons between the prescribed rations, based on feedstuff costs alone. Cost of gain in the feedlot was 43 cents per pound or $24.30 per head versus 34 cents on pasture or $19.69 per head, and 66 cents per pound on the raised floor or $44.02 per head, he said.

So, it cost $19.72 per head extra or about $2.50 per pound of grease wool to produce high quality lamb wool having a potential value 10 to 20 times greater than that of feedlot wool, which in today's market is worth 25 to 35 cents per pound grease.

To realize the high potential value of a specialty type wool requires a different kind of innovative marketing system, Lupton said. To that end, Lupton, along with Extension economist Dr. Ernie Davis, have created a Web-based "listing service" whereby buyers or sellers can access the page and search. For example, a buyer could search for a specific product with perhaps a specific micron and staple length and then obtain a list of the sellers of these products. In the future, someone who has a specialty product to sell can offer it on this listing service.

The service is still in the developmental stage, Lupton said. How successful such a system might be remains to be seen.

The researchers have started another test using the raised floor.

Dr. Millard Calhoun, research nutritionist, has been working for the Texas A&M Experiment Station for 38 years. In his tenure, the researcher has become a leading expert in the feeding of cotton byproducts.

Calhoun started out at the McGregor station, where all sheep and goat research was being done at the time. He gave his first official presentation on cottonseed at a McGregor Beef Cattle field day. It was the winter of 1970, Calhoun recalled, and though cottonseed prices were fairly low, little cottonseed was being fed. Since then, he has been involved with more than a hundred different experiments in which cotton byproducts were fed to cattle, sheep, and goats.

The researcher pointed out some key differences between several of the more popular cotton byproducts used as supplemental feed.

Because gin trash is occasionally fed to livestock, Calhoun has conducted a number of studies to determine its feeding value. He also looked at the impact of arsenic in the feed where it was still being used as a cotton desiccant.

Though gin trash is cheap and has some nutritional value, for safety reasons he cautioned producers to consider using only trash from cotton that is naturally desiccated.

He also noted the difference between upland cottonseed and pima cottonseed. The fuzzy upland seed, Calhoun said, accounts for 98 percent of the cotton grown in the U.S.

Pima cotton is grown in far West Texas, New Mexico and Arizona, but the primary region is the San Joaquin Valley in California.

There are important differences between the two. Pima cottonseed has a higher level of fat and protein and a lower level of fiber than upland cottonseed. More important, however, is that pima has a much higher level of gossypol, which can be toxic to livestock.

Average gossypol levels for pima seed, Calhoun said, are about nine-tenths of one percent while for upland cottonseed, gossypol levels average about six-tenths of one percent. Pima also has a much higher proportion of the "minus isomer," which is the more toxic isomer of gossypol.

"So pima seed not only has higher gossypol levels, it also has a higher proportion of the minus isomer," Calhoun cautioned.

Another critical difference is that little whole fuzzy cottonseed passes through cattle without being digested.

"In contrast, when we feed pima seed we notice that a substantial amount of the seed is undigested and comes out as whole cottonseed. It could be as high as 10 to 15 percent."

That has forced many who use pima seed to either crack or grind the seed before feeding it to cattle.

"However, one thing they did not appreciate was how much more available gossypol was when the seed was processed before being fed," Calhoun pointed out.

During a drouth, the speaker cautioned, those feeding cottonseed should realize there is a greater potential for gossypol poisoning.

"The ability of the rumen to detoxify gossypol is a function of dry matter intake," he explained. "When we get into a drouth, animals don’t have the dry matter intake that they would normally have, so it's important to monitor gossypol levels in the feed and in the blood."

Signs of gossypol problems are poor reproductive performance and sudden death.

He shared research results from a recent study in which he fed 1.3 pounds of upland cottonseed and pima seed to late gestation ewes three times a week. The ewes were bled after three weeks.

Plasma gossypol levels in animals fed upland cottonseed were acceptable, about six micrograms of gossypol per milliliter. The animals fed pima seed, however, had gossypol levels in their bloodstream as high as 19 micrograms per milliliter.

"That's high enough that if we had continued the study we would have seen some serious death losses."