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United States Department of Agriculture

Agricultural Research Service

Research Project: GENETIC AND PHYSIOLOGICAL APPROACHES TO IMPROVING PERFORMANCE OF BEEF CATTLE GRAZING PASTURES IN WHICH ENDOPHYTE-INFECTED FORAGES DOMINATE
2010 Annual Report


1a.Objectives (from AD-416)
The long-term objective of this project is to develop an improved understanding of livestock physiology and genetics to enhance the productivity and profitability of meat production from cattle grazing improved temperate pastures while reducing animal stress. Over the next 5 years this project will focus on the following objectives: Objective 1: Improve grazing animal performance by identifying genes that reduce stress from endophyte-infected cool-season pastures. Subobjective 1.A. Determine if the tropically adapted Romosinuano breed of cattle is more tolerant of heat stress and fescue toxicosis than Angus cattle. Subobjective 1.B. Identify genetic markers in cattle tolerant of heat stress and/or fescue toxicosis. Subobjective 1.C. Determine the role of thermoregulation in tolerance to fescue toxicosis in ruminants. Objective 2: Enhance nutrient utilization from endophyte-infected cool-season forages through improved understanding and manipulation of the microorganisms of the rumen. Objective 3: Develop improved cow-calf and stocker management practices for pastures in which endophyte-infected forages dominate. Subobjective 3.A. Define the effects of ergot alkaloids and lower body condition on cow and/or heifer reproductive performance. Subobjective 3.B. Define sequences of forages and forage management protocols to enhance the productivity and profitability of cow-calf and stocker cattle grazing temperate pastures. Subobjective 3.C. Investigate the mechanisms involved in fecal shedding of pathogenic bacteria from ruminants consuming toxic endophyte-infected (wild type) tall fescue (EI-TF).


1b.Approach (from AD-416)
Physiological parameters (respiration rate, skin and rectal temperature, and blood metabolites) of cattle consuming endophyte-free and -infected fescue diets will be compared in environmentally-controlled chambers. Genetic markers of cattle tolerant to heat stress and/or fescue toxicosis will be assessed. Microarray hybridization will be utilized to obtain estimates of gene expression changes due to heat stress and/or fescue toxicosis within breeds of cattle. Replicated field experiments will evaluate cow-calf and stocker management practices and genotypes on novel, endophyte-free or -infected tall fescue pastures to alleviate fescue toxicosis and improve calf production. Ruminal microbes that are capable of degrading ergot alkaloids will be evaluated. In vivo and in vitro studies will be conducted to determine production practices affecting fecal shedding of E. coli and Salmonella.


3.Progress Report
Objective was to determine the effects of fescue variety (Toxic vs. Not toxic), single nucleotide polymorphisms (SNPs) genotype of a prolactin promoter segment and a coding sequence of cytochrome p450 (CYP450), as well as their interaction on gene expression levels of various cytokines [a measure of immune function; prolactin (L-PRL), interleukin-8 (IL-8), and tumor necrosis factor a (TNFa)]. Fifty-eight steers grazed either toxic (KY-31) or non-toxic (HM4 or MaxQ) fescue for 6 months after weaning. Gene expression of proteins involved in immunity did not appear to be influenced by toxic fescue, genetic make-up or both in steers. If immune function is jeopardized in steers consuming toxic fescue, it would seem a mechanism other than white blood cell expression is involved. Objectives were to examine effects of toxic endophyte and non-toxic novel (MaxQ and HiMag) endophyte-infected tall fescue on performance and grazing behavior of pregnant Brangus and Gelbvieh x Angus heifers. Pregnant heifers grazing HiMag or MaxQ tall fescue performed better than those grazing E+ fescue. Incorporation of novel endophyte-infected tall fescue into a grazing program can increase the performance of pregnant beef heifers compared with heifers consuming toxic endophyte-infected tall fescue. Increased performance is partially due to heifers spending more time grazing and less time in the shade than heifers grazing toxic endophyte-infected tall fescue. Response to heat stress may differ in Bos taurus originating in different US regions. Angus steers from Oklahoma (OK) and Missouri (MO) were compared to heat-tolerant Romosinuano steers (RO) from Florida in the University of Missouri Brody Environmental Center. Geographic origin of Angus did not affect the heat stress response. Romosinuano steers exhibited characteristic heat tolerance, but showed that some temporal response to heat stress may differ in Bos taurus cattle originating in different US regions in response to prolonged heat exposure. In the process of identification of the bacterial isolates and understanding the metabolic processes of the bacteria. A method for determination of ergot alkaloids by liquid chromatography-mass spectrometry has been developed which was able to identify 87 mycotoxins and mycotoxin metabolites. This assay is being used to accomplish other milestones, namely, degradation of ergovaline by soil microbes. This assay will also be used for quantification of ergot alkaloids and determination of metabolites from feeding trials, microsomal incubations, and clinical and forage samples. In FY 2010, 7 peer-reviewed journal articles, 8 agricultural experiment station reports, 9 abstracts, and 3 invited presentations resulted from this project.


4.Accomplishments
1. Identification of specific gene differences may identify cattle with superior fertility. Fertility of the cowherd is important to the profitability of beef production. Use of traditional selection techniques is slow, usually requiring several years to produce desired changes within a herd. However, use of specific genetic differences among cattle can accelerate the selection of cattle that are more productive on toxic tall fescue. Scientists from ARS in Booneville, Arkansas, and University of Arkansas personnel identified genetic differences in certain regions of two genes, prolactin and heat shock protein 70, and determined the association of these differences with fertility in beef cows. Differences in these two genes were associated with calving rate of beef cows. These results provide information that suggests identification of cows with specific genotypes can assist beef producers in selection of cows that may have increased fertility.

2. Toxic compounds found in tall fescue can influence bull semen. Decreased performance of one bull will affect the pregnancy rate of 20 to 25 cows. Minimal research exists on the negative effects of toxic tall fescue on bull reproductive performance. Less is known of how alkaloids found in toxic fescue have their effects on sperm cells. Scientists from the University of Arkansas and ARS in Booneville, Arkansas, investigated the specific pathways involved in how toxic compounds found in tall fescue reduce bovine sperm motility. Most of these toxic compounds are fat solubles, suggesting that they may easily move across sperm membranes to directly interact within the sperm cell. Beef producers should minimize the use of toxic fescue during the breeding season to optimize pregnancy rates of the cowherd. Use of nontoxic forage diets or grain supplementation during the breeding season will alleviate the detrimental effects of toxic fescue on sperm motility.

3. Dried distillers grain, a co-product of ethanol production, may provide limited-resource livestock producers with alternative supplementation strategies. Consistent daily body weight gains of stocker steers can be attained by adjusting the amount of distillers dried grain supplement (DDGS) based on forage nutritive value. Mowing and storing forages, such as silage, increase production costs. Feeding specific amounts of DDGS to steers based on pasture characteristics for targeted daily weight gains will allow weight gains comparable to more labor-intense, costly supplementation systems. If a stocker operator does not have resources or ability to mow and store forage as silage, adjusting the amount of DDGS fed to steers is a viable option.


5.Significant Activities that Support Special Target Populations
Scientists have participated in activities targeting minority, historically under-served operators/stakeholders including:.
1)co-advisor of a minority student from University of Arkansas,.
2)mentor summer intern from Langston University, and.
3)host Dean and faculty from Langston University at DBSFRC. Scientists have participated in activities targeting small farmers, including:.
1)bus tour of small farms in western Arkansas,.
2)on-farm cow-calf research on two private farms in Arkansas,.
3)farm visits to seven farms in Arkansas, and.
4)presented 'economic impact of cattle industry' to civic club in Arkansas. The Dale Bumpers Small Farms Research Center constructed and staffed an informational exhibit at the Sixth Annual Tennessee Small Farm Expo and Small Farmer Recognition Program in McMinnville, TN, at the Otis Floyd Nursery Research Center on July 15, 2010. The expo was hosted by Tennessee State University and was attended by farmers, students, representatives from federal and state agencies, and by university faculty.


Review Publications
Looper, M.L., Black, S.G., Reiter, S.T., Okimoto, R., Johnson, Z.B., Brown, M.A., Rosenkrans, C.F. 2010. Identification of polymorphisms in the enhancer region of the bovine prolactin gene and association with fertility in beef cows. Professional Animal Scientist. 26:103-108.

Wang, H., Looper, M.L., Johnson, Z.B., Rorie, R.W., Rosenkrans, C.F. 2009. Signaling pathways used by ergot alkaloids to inhibit bovine sperm motility. In Vitro Cellular and Developmental Biology - Animals. 45(8):483-489.

Rosenkrans, C., Banks, A., Reiter, S., Looper, M.L. 2010. Calving traits of crossbred Brahman cows are associated with heat shock protein 70 genetic polymorphisms. Animal Reproduction Sciences. 119:178-182.

Burke, J.M., Coleman, S.W., Chase, C.C., Riley, D.G., Looper, M.L., Brown, M.A. 2010. Interaction of breed-type and endophyte-infected tall fescue on milk production and quality in beef cattle. Journal of Animal Science. 88:2802-2811.

Last Modified: 10/21/2014
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