BEEF CATTLE RESEARCH UPDATE

Spring, 2004

Harlan Ritchie, Steven Rust and Daniel Buskirk

Beef Cattle Specialists

Michigan State University

East Lansing, Michigan 48824

Following are reviews of research projects recently reported at scientific meetings or in scientific publications. Scroll down to read:

1) 19 Genes are Affected by Inactive Myostatin

2) Sexed Semen

3) Emerging Issues For Cow Herds – Higher Yielding Cattle !

4) Feed Flax to Increase Omega-3 Fatty Acids

5) Fatty Acids in Beef - Heritable Trait

6) Grass-Fed versus Grain-Fed, Nutrient Content

7) Cooking affects Tenderness more than Marbling

8) Future Trends – Global Meat Demand.

BREEDING/GENETICS

Nineteen Genes Were Differentially Expressed Between Normal and Double-Muscled Embryos

Cattle that have two copies of the mutated (inactive) myostatin gene express the “double-muscled” phenotype. The active form of the myostatin gene is somehow involved in the control of muscle growth. In this Iowa State Univ. study, heterozygous (one-copy) bulls were mated to heterozygous cows. Shortly after the time at which myostatin is first expressed in the embryo, the cows were slaughtered and the embryos were collected and genotyped. Using a process known as suppressive subtractive hybridization, 19 genes were found to be expressed differently between normal and double-muscled embryos. The known functions of several of these genes suggest that they may act directly in the control of muscle growth by myostatin. The authors stated that this information could potentially aid in the development of strategies to improve lean tissue deposition in livestock species (Steelman et al. 2004. Iowa State Univ. Anim. Ind. Rep., A.S. Leaflet R1876).

Flow Cytometry Was 90% Accurate in Sorting Sperm Into Male and Female Cells

This Colorado State Univ. study had two objectives: to determine whether calves produced by sexed sperm differed from controls, and to what extent the sex ratio of calves was altered by the sexing procedure (flow cytometry/cell sorting). Data were used from 739 calves produced from control sperm and 1,169 calves produced from sexed sperm.

There were no significant differences between treatments in gestation length, calving ease, birth weight, calf vigor, abortion rate, weaning weight, and calf death rate from birth to weaning. No anatomical abnormalities were noted for any calves in this study. The sex ratio of calves from unsexed control semen was 49.2% male; 50.8% female. Accuracy of using X (female)-sorted sperm was 87.8% female calves, and Y (male)-sorted sperm produced 92.1% male calves. It was concluded that flow cytometry/cell sorting can be used to preselect calves safety with approximately 90% accuracy (Tubman et al. 2004. J. Anim. Sci. 82:1029).

Emerging Issues for Cow Herds

Dr. John Lawrence, Director of the Iowa Beef Center at Iowa State Univ. recently presented an excellent review of emerging trends and issues in the beef industry. Following is a brief summary of some of the points he made (Lawrence. 2004. Proc. 33^rd Annual Cornbelt Cow-Calf Conf., Ottumwa, IA).

· Now that USDA has prohibited acceptance of “downer” cows, producers should rethink management of cattle that may potentially become nonambulatory and market them before they begin to go down hill rather than waiting until they are worse.

· Value-based or grid marketing will continue its growth and will likely evolve to include other attributes. To date, Choice-Select spread has been the major determinant of grid premiums and discounts. However, premiums on Yield Grades 1 and 2 are growing and discounts on YG 3.5 will become more common. The base price may eventually decline into the YG 2 range. Economics are driving the trend to higher yielding cattle as the industry moves to more case-ready beef products.

· Information on how calves may be expected to perform in the feedlot has become increasingly important. In the future, performance in the cooler will increase in importance as carcass premiums and discounts increase.

· Information on cow herd health practices will become more valuable now that we know calf sickness has a dramatic impact on carcass value as well as feedlot performance.

· Special calf sales in which consignors have common management practices and genetics will become increasingly popular.

· A national ID system will improve the opportunity to verify and pass information from seller to buyer regardless of how cattle are sold.

· In the past, cow herds needed to retain ownership of their calves to capture their full value. With proven performance and traceable data that can be marketed with the calves, feedyards will be willing to pay closer to their full value.

STOCKER/FEEDLOT

Effect of Processing Flax on Feedlot Performance and Carcass Characteristics

Flaxseed is a rich source of the omega-3 polyunsaturated fatty acid, alpha-linoleic acid, which has been shown to reduce the risk of cardiovascular disease and cancer in humans. Research at North Dakota State Univ. (Maddock et al., Proc. 2003 Recip. Meat Conf.) indicated that supplementing cattle diets with flax may increase the level of omega-3s in the beef. Furthermore, work at Kansas State Univ. (Farran et al., 2002 Kansas Beef Res. Rep.) suggested that feeding flax to incoming feeder cattle may increase immune response and improve feed efficiency. The objective of this North Dakota State Univ. trial was to determine if processing of flax would enhance feedlot performance and carcass traits. A total of 128 heifers (794 lb) were allotted to four treatments: 1) control (no flax); 2) whole flax; 3) rolled flax; or 4) ground flax. Supplemental flax level was 8% of diet dry matter. Compared to control, the flax treatments had increased average daily gain (3.35 vs. 3.06 lb/d) and improved feed conversion (7.46 vs. 8.26 feed/gain). Processing improved average daily gain over whole flax (3.44 vs. 3.18 lb/d), but there was no significant difference between rolled and ground. Flax addition had no effect on dressing percentage, external fat thickness, or ribeye area. However, KPH fat percentage and yield grade score increased with flax supplementation. There were no differences in marbling score. The authors concluded that supplemental flax may improve feedlot performance, and that processing flax may further enhance daily gain. However, there may be a risk of increasing yield grade score with flax addition (Maddock et al. 2004. Midwestern Section, ASAS, Abstract 302 ).

CARCASS/MEAT SCIENCE

Fatty Acid Composition of Beef Is Moderately Heritable

Iowa State Univ. (ISU) animal scientists used the data from 800 sire-identified cattle in the ISU breeding herd to determine if the healthfulness of the fatty acid composition of beef can be improved through selection. The objective would be to decrease the amount of the saturated fatty acids, palmitic and myristic, which account for 29% of the total fatty acids in beef, or increase the amount of the monosaturated fatty acid, oleic acid, which accounts for 41% of the total fatty acids. Heritability estimates of these fatty acids were found to be as follows: palmitic, .40; myristic, .39; and oleic, .33. These estimates suggest that traditional animal breeding selection programs could improve the fatty acid composition of beef. The authors stated that while these changes may not be large enough to make immediate compositional changes in beef fatty acids that are meaningful to the consumer, it does offer hope that improvements could be made over time. They further stated that they are interested in identifying genetic variance in candidate genes to eventually be able to predict the fatty acid composition of beef based on DNA analysis (Knight et al. 2004, Iowa State Univ. Anim. Ind. Rep., A.S. Leaflet R1882).

Nutrient Content of Grass-Fed and Grain-Fed Beef

Scientists at California State University, Chico (CSUC) recently conducted a comprehensive review of research on the nutrient content of grass-fed beef. Following is a brief summary of their review.

· Although beef is not a significant source of beta-carotene (pro-vitamin A), grass-fed beef furnishes approximately two times the beta-carotene content of that raised on a concentrate-based diet. It also provides a three-fold increase in vitamin E.

· The typical American diet contains an imbalance of 10 to 20 times more omega-6 fatty acids than omega-3 fatty acids. A more appropriate omega-6 intake would be no greater than 4 to 5 times than that of omega-3. An ideal ratio would be 2 to 1. Concentrate-fed beef has a ratio of about 4 to 1. The ratio in grass-fed beef is approximately 2 to 1.

· In recent years, numerous human health benefits have been attributed to an increased consumption of conjugated linoleic acid (CLA), which is synthesized in the rumen of cattle and other ruminants. Beef raised on grass-based diets contains 2 to 3 times more CLA than beef from cattle fed concentrate-based diets.

· It is important to note, however, that an average 3.5 oz. serving of beef, whether it be grain-fed or grass-fed, contains only a fraction of the omega-3 fatty acids (8% vs. 13%) or CLA (10% vs. 25%) recommended in the human diet (Abbott et al. 2004. College of Agriculture, CSUC and Univ. of California Cooperative Extension Service).

Endpoint Cooking Temperature Had a Greater Effect on Steak Tenderness Than Did Marbling

Kansas State Univ. researchers conducted a study to determine the effects of endpoint temperature, cooking method and marbling on the tenderness of three different beef muscles, one containing a low amount of connective tissue (strip loin) and two containing high amounts of connective tissue (bottom round and brisket). Cooking methods were an electric belt grill (rapid conduction) or a water bath (slower, convection method). Steaks were cooked at nine different endpoint temperatures, ranging from 104 to 176º F. Marbling levels were USDA Select and Certified Angus Beef. Warner-Bratzler Shear Force (WBSF) was used to measure tenderness.

· Optimum tenderness occurred around 131º F (rare) for the strip loin. However, increased marbling protected strip loin tenderness at higher endpoint temperatures. Steaks on the belt grill were more tender than those cooked in the water bath.

· Bottom round and brisket improved in tenderness as endpoint temperature increased from 104 to 140º F and then declined as temperature increased from 149 to 176º F.

· Neither cooking method nor marbling influenced the tenderness of bottom round. Marbling had no effect on brisket tenderness. Brisket steaks cooked on the belt grill were more tender than those cooked in the water bath.

The authors concluded that the effect of increasing the endpoint temperature on tenderness of the strip loin was appreciably different than that for bottom round and brisket. They also noted that endpoint temperature had a greater impact on tenderness than did marbling, especially in muscles with a high content of connective tissue (Obuz et al. 2004. Kansas State Univ. Report of Progress 923).

FUTURE TRENDS

Meeting the Growing Global Demand for Meat Will be A Challenge

In a recent review of future needs for global meat production, Thomas Elam, economist at the Univ. of Indiana/Purdue Univ., Indianapolis, projected that world demand for meat will increase by 55% during the period from 2001 to 2025 (Feedstuffs, Jan. 26, 2004). This prediction was based upon the following projections.

· The global economy (gross domestic product) will increase by 30%. Modern history has shown that

when people earn more income, they will eat more meat.

· World population will increase by 25%, from 6.2 to 7.8 billion.

The author went on to say that the world has essentially run out of land that can easily and productively be bought under cultivation. Furthermore, nearly all of the world’s grasslands are already being grazed. Global grain yield per acre is projected to increase by 31%, and oilseed yields by 25% from 2001-25. However, this will not be adequate to cover the increased demand for meat. In addition, feed conversions will need to improve by about 15-20% and feed wastage must be reduced, especially harvest and post-harvest losses of grains and oilseeds. The goals that would be required for the U.S. to maintain its share of increased global production and remain cost competitive through 2025 are shown in the following table.

Targets for U.S. Meat Production, 2025
Item	Current	2025 Target	% Change
Corn yield (bu./acre)	135	180	33%
Soybean yield (bu./acre)	35	47	34%
Fed cattle conversion feed/gain)	6.5	5.0	23%
Swine conversion (feed/gain)	3.0	2.5	17%
Broiler conversion (feed/gain)	1.9	1.5	21%
Beef production (bill. lb)	26	34	31%
Pork production (bill. lb)	20	31	55%
Broiler production (bill. lb)	32	41	28%

Is this possible? The author stated that it is feasible, but to achieve these results will require sustained investments in research for technology, including biotechnology, that does not exist today. The promise of biotechnology certainly needs to be realized, but traditional genetics, nutrition, housing and animal health will continue to play a vital role. He concluded that with adequate investments in research, we can supply the world with the food it wants, keep costs under control, improve nutritional standards in the poorest nations, and do it all with minimum impact on the environment.

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