Research Accomplishment Reports 2007

Regulated Expression of Genes/Proteins Critical to Anionic Amino Acid N Metabolism by Developing and Aging Beef Cattle

J.C. Matthews, J.A. Boling
Department of Animal and Food Sciences

 

Project Description

The overall goal of this new Hatch project (approved spring 2007) is to optimize the dietary protein load to absorption and metabolic capacities of gastrointestinal and peripheral tissues throughout the life cycle of beef cattle by developing the means to manipulate amino acid N metabolic capacity. Significant progress towards meeting research goals of Objectives 1 and 2 are presented:

Objective 1: To determine if expression by the small intestine of mRNA encoding transport proteins capable of cationic amino acid (CAAT) absorption responds to increased abomasal supply of rumen-derived microbes (hence, AA substrates), energy, or both. Angus steers (BW 260 kg) were assigned (n=6) to either water (control) or ruminal or abomasal corn starch infusion treatment and fed an alfalfa-cube based diet at 1.3 NEm requirement. After a 14 or 16-d infusion period, steers were killed, and total RNA extracted from duodenal., jejuna, and ileal epithelia. Real-time RT-PCR analyses were conducted to quantify the relative expression (CAAT mRNA:18S RNA) of seven mRNA of four known mammalian CAAT activities. All CAAT associated mRNA were differentially expressed by duodenal, jejunal, and ileal epithelia. Four mRNA expressed by jejunal epithelium were down-regulated in the presence of increased luminal supply of microbial-AA (CAT1, 27%; rBAT, 41%; y+LAT2, 35%; and 4F2hc, 39%) or increased luminal supply of energy (y+LAT2, 32%, and 4F2hc, 25%).

Thus, unique (to both cattle and other species) knowledge has been generated describing the small intestinal expression profile (thus, potential functional capacity) and substrate regulation of gene expression for transporters that absorbed lysine, a predominant limiting amino acid of growing cattle raised under commercially-relevant conditions.

Objective 2: Ongoing research in our lab has shown that old beef cows have reduced (60 to 80%) hepatic expression of glutamine synthetase (GS) and alanine transaminase (ALT), two enzymes in the liver that are critical for optimal N recycling. To characterize the effect of supplemental estrogen on these two proteins and other indicators of hepatic glutamate metabolic capacity. Fourteen old (> 10 yrs) non-pregnant beef cows were fed an alfalfa hay-based diet for 28 d, after receiving (n = 7) either a sham (Control) or COMPUDOSE(reg. tm) (Implant; 25.7 mg estradiol) implant. On d 14 and 28, jugular blood and liver biopsy samples were collected. Plasma estrogen concentration of implanted cows (5.07 pg/mL) was 222 % more than for Control cows (1.5 pg/mL). Plasma ammonia, serum urea N levels, aspartate transaminase, and ALT concentrations were not affected. Immunoblot analyses were performed to quantify the relative liver content of four glutamate/aspartate metabolizing and 2 glutamate/aspartate transporters. GS content was increased 350% by d 14 and 200% by d 28. In contrast, the expression of the 3 other glutamate metabolizing enzymes and 2 glutamate/aspartate transporters was not affected.

Thus, hepatic expression of GS in old beef cows is sensitive to upregulation by supplemental estrogen, whereas expression of other proteins that support hepatic glutamate metabolism may not be.

Impact

The findings of this research will give insight into when and how amino acid metabolism is altered to support growth and fattening of steers and milk production capacity of mature and aging beef cows. Specifically, these studies will provide data to determine differences in gene expression that account for different levels of metabolic capacity in the life-cycle of cattle.

The extent to which protein and amino acid-N is utilized and retained in the tissues contributes to the efficiency of growth, maintenance, and production of cattle. The application of this research is to optimize the dietary protein load to absorption and metabolic capacities of gastrointestinal and peripheral tissues as calves develop and cows age so that management tools and agents to control/achieve optimal functional capacity of these proteins can be developed. Having the ability to manipulate metabolic capacity will enable feeding strategies and systems to be developed that improve the efficiency of N utilization for maintenance and production, while minimizing excretion of metabolic N where differences are determined to exist in the young versus old mature beef cow. There are 1.12 million cows grazing forage lands in Kentucky, and 32.8 million throughout the United States (National Agricultural Statistical Service Report, USDA, January 1, 2004). By identifying proteins that are altered in commercially-relevant production stages throughout the life cycle of cattle, this research fills a critical void in our current growth prediction models used by the livestock industry. For Kentucky alone, if only a 0.9 kg gain/calf (0.4% of body weight) is realized from this research, then an increase in direct farm receipts of $1.2 million dollars from the sale of weanling calves and a total economic gain of $6 million annually will be realized. Analogously, if the productive life of aged cows (about 200,000 cows) can be increased by only one calf, then a net savings of $4,000,000 ($20/cow) per year in heifer replacement costs will be realized.

Another significant problem of the many of Kentucky's 30,000 cow/calf producers that our research addresses is the lack of a rational basis for culling an old cow from the herd, other than whether she breeds back. However, very little data exists regarding the effects of age on the metabolic capacity of the beef cow. Threfore, the clinical blood profiles of old vs young cows being generated by our correlating clinical blood profiles to hepatic and skeletal muscle protein profiles of old vs young beef cows will provide unique and extremely pertinant data. This data will be useful for producers to make management decisions (when to cull) and to veterinarians as a diagnostic tool. In addition, this data describing the metabolic decline of beef cows will be highly relevant to the effect of senecence in other animal species (including humans).

Publications

Las, J. E., N. E. Odongo, M. I. Lindinger, J. C. Matthews, A. K. Shoveller, and B. W. McBride. 2007. Effects of Dietary Strong Acid Anion Challenge on Regulation of Acid-base Balance in Sheep. J. Animal Science, 85:2222-2229. doi:10.2527.

Kitts, S. E., J. C. Matthews, K. K. Schillo, T. S. Rumsey, T. H. Elasser, S. Kahl, R. L. Baldwin, and K. R. McLeod. 2007. Effects of Chlortetracycline and Synovex-S(reg. tm) on Growth Rate and on Plasma Growth Hormone and Thyroid Hormone Concentrations Following Administration of Thyroid-releasing Hormone and GH-releasing Hormone in Beef Steers. Canadian J. Animal Science 87:327-341.

Liao, S. F., E. S. Vanzant, J. A. Boling, and J. C. Matthews. 2007. Identification and expression pattern of cationic amino acid transporter-1 (CAT-1) mRNA in small intestinal epithelia of Angus steers at four production stages. J. Animal Science, doi:10.2527/jas.2006-727; PMID: 17998425

Guimaraes, K. C., S. M. Rodriguez, J. C. Matthews, K. C. Swanson, D. L. Harmon, and A. F. Branco. Influence of Starch and Casein Administered Postruminally on Small Intestinal Sodium-Glucose Cotransport Activity and Expression. 2007. Brazilian Archives of Biotechnology and Technology 6:963-970.

S. F. Liao, M. J. Alman, E. S. Vanzant, E. D. Miles, D. L. Harmon, K. R. McLeod, J. A. Boling, and J. C. Matthews. 2008. Basal expression of nucleoside transport mRNA differs among small intestinal epithelia of beef steers and is differentially altered by ruminal or abomasal infusion of starch hydrolysate. J. Dairy Science (accepted, manuscript no. JDS-07-0763R1).

Greenwood, S. L., N. E. Odongo, O. AlZahal, K. C. Swanson, A. K. Shoveller, J. C. Matthews, and B. W. McBride. 2007. Plasma amino acid profile and expression of the ubiquitin-mediated proteolytic pathway in lambs with induced metabolic acidosis. J. Animal Science (submitted December 2007.)

Matthews, J. C., and K. R. Brown. 2007. Nutritional Genomics: A New Frontier of Livestock Nutrition? Page 206 to 213 in Proc. 68th Minnesota Nutrition Conference, Minneapolis, MN.

Brown, K. R., R. B. Cox, G. A. Anderson, G. K. Rentfrow, L. P. Bush, J. R. Strickland, J. A. Boling, and J. C. Matthews. Evaluation of Neotyphodium coenophialum Exposure on Carcass Mass, Ribeye Area, and Meat Quality of Growing Steers Grazing High versus Low Endophyte Infected Forages.2007. SERA-IEG 8, Tall Fescue Toxicosis/Endophyte Workshop. October 14-16, 2007, Wildersville, TN.

Klotz, J. L., B. H. Kirch, G. E. Aiken, J. R. Strickland, L. P. Bush, K. R. Brown, J. C. Matthews, and J. A. Boling. Vasoactivity of Selected Ergot Alkaloids. SERA-IEG 8, Tall Fescue Toxicosis/Endophyte Workshop. October 14-16, 2007, Wildersville, TN.

Taylor-Edwards, C., K. M. McLeod, J. C. Matthews, J. J. Holst, and D. L. Harmon. 2007. Evidence for a Role for Glucagon-like Peptide-2 (GLP-2) in Ruminant Animals. FASEB J. 21 (6):A1077.

Liao, S. F., M. A. Alman, E. S. Vanzant, E. D. Miles, D. L. Harmon, K. R. McLeod, J. A. Boling, and J. C. Matthews. 2007. Ruminal, but not Abomasal Infusion of Starch Differentially Increases Expression of Concentrative Nucleoside Transporter (CNT) mRNA by Small Intestinal (SI) Epithelia of Forage-fed Steers. J. Dairy Science 90 (suppl. 1):343.

Brown, K. R., R. B. Cox, G. A. Anderson, G. K. Rentfrow, L. P. Bush, J. R. Strickland, J. A. Boling, and J. C. Matthews. 2007. Neotyphodium coenophalium Exposure Reduces Carcass Mass and Ribeye Area, but not Meat Quality, of Growing Steers Grazing High Versus Low Endophyte Infected Forages. J. Animal Science 85 (suppl. 1):418.

Brown, K. R., L. R. Harrison, J. L. Klotz, J. R. Strickland, J. A. Boling, and J. C. Matthews. 2007. Neotyphodium coenophalium Alters Blood Metabolites Involved in Nitrogen, Energy, and Mineral Metabolism in Growing Steers. J. Animal Science 85 (suppl. 1):12.

Klotz, J. L., K.R. Brown, L. P. Bush, J. C. Matthews, J. A. Boling, and J. R. Strickland. 2007. Grazing High Versus Low Endophyte-infected Fescue Reduces Contractility of Bovine Lateral Saphenous Veins. J. Animal Science 85 (suppl. 1):12.

Greenwood, S. L., T. C. Wright, J. Gilmore, J. E. Las, N. E. Odongo, O. AlZahal, A. K. Shoveller, J. C. Matthews, and B. W. McBride. 2007. Impact of Metabolic Acidosis on the Amino Acid Metabolism in Lambs. J. Animal Science 85 (suppl. 1):83.