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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
2008 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
Cow-calf performance of Romosinuano cattle is being compared to Angus cattle under field conditions. Milk production was determined every 28 days between 60 and 200 days postpartum between May and August in 2007 and 2008. At that time, body temperature of cows was determined and blood samples collected to determine serum concentrations of prolactin as an indicator of fescue toxicosis. These data will be analyzed. Body weight of calves indicated that calf growth was similar between both purebred cows and greater in calves born to crossbred cows. Fecal samples collected from cows and calves for determination of fecal egg counts indicated that infection rate was too low to determine differences between breed or forage types. Pregnancy rate, breeding interval, calf age at weaning, and adjusted weaning weight will be analyzed and paper will be submitted. (Component 1 of NP 101)

Specific primers developed for P450 (liver enzyme) and prolactin genes were evaluated in steers randomly assigned to graze either toxic or one of two animal-friendly fescue pastures. Calf body weights were recorded on the sample collection days. Following grazing of fescue pastures (approx. 160 days), steers were transported (May 20) to a feedyard in Stillwater, OK. Fat biopsies and blood samples will be collected at feedyard entry (day 0), re-implant (day approx. 56), and 10 days before harvest (day approx. 125). Enzymatic activities of lactate dehydrogenase and glucose 6-phosphate dehydrogenase will be determined. Cattle will be harvested and carcass data will be collected at a commercial processing facility in the fall 2008. (Component 1 of NP 101)

Multiparous Brahman-influenced cows were managed to achieve low or moderate body condition to determine the relationship of single nucleotide polymorphisms of follicle stimulating hormone gene with serum hormone metabolites, follicle size, calving date, and calving percentage. Polymorphisms are associated with non-esterified fatty acids and prolactin, but a larger dataset, currently being assembled, is needed to detect differences in calving rates. (Component 1 of NP 101)

Develop improved cow-calf and stocker management practices for pastures in which endophyte-infected forages dominate: A comparison of fat and thin cows grazing either tall fescue or bermudagrass found cows grazing toxic fescue during the breeding season lost body condition (got thinner); thinner cows that grazed tall fescue had lower pregnancy rates than fatter cows. Cows in adequate body condition were more tolerant of the negative effects of consuming toxic fescue. Estrous behavior was similar among all treatments. Second-year data are currently being collected. (Component 2 of NP 101)


4.Accomplishments
1. Evaluation of animal friendly tall fescue on growth rate and grazing behavior of beef heifers: Ruminants grazing toxic tall fescue have reduced feed intake, average daily gain, and poor conception rates, costing livestock producers $600 million annually. Fescue cultivars have been developed that contain a novel (animal-friendly) endophyte that does not produce the toxic ergot alkaloids that cause fescue toxicosis. Comparisons of breed types of growing heifers grazing different fescue cultivars are limited. ARS scientists from Booneville, AR, and personnel from the University of Arkansas conducted a study to evaluate the effects of toxic and novel endophyte-infected tall fescue on growth and grazing behavior of pregnant Brangus and Gelbvieh x Angus heifers. Average daily gain was not different between breed types; however, heifers grazing novel endophyte fescue were heavier than heifers grazing toxic fescue. Fewer heifers grazing toxic fescue were observed grazing during the hot time of the day than heifers grazing novel endophyte 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, partially due to more time spent grazing and less time in the shade. (Component 2 of NP101 and Component 2 of NP215)

2. Influence of toxic tall fescue diets on fecal shedding of toxic E. coli O157:H7 in ewes: Escherichia coli O157:H7 is one of the most common agents of foodborne illness in humans. Data on the prevalence of E. coli O157:H7 from ruminants consuming endophyte-infected tall fescue are minimal. ARS scientists from Booneville, AR, College Station, TX, and Lexington, KY, and personnel from the University of Arkansas studied sheep experimentally inoculated with E. coli O157:H7 and fed diets containing 50% high endophyte-infected (HI-E) or low endophyte-infected (LO-E) tall fescue seed for 7 days. Ewes fed HI-E seed had lower dry matter intake and weight gain. Fecal shedding of E. coli O157:H7 tended to be decreased in LO-E ewes compared with HI-E ewes. These results suggest short-term consumption of toxic tall fescue diets may decrease feed intake which ultimately will increase fecal shedding of E. coli O157:H7 in ruminants. (Component 3 of NP101 and Component 1.1 of NP 108)


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 and.
2)overview of research to Kentucky State University tour group. Scientists have participated in activities targeting small farmers, including:.
1)bus tour of small farms in central Arkansas,.
2)on-farm cow-calf research on one private farm in Arkansas,.
3)farm visits to five private farms in Arkansas,.
4)review panel for Southern Region SARE producer grants, and.
5)presented economic impact of cattle industry to civic clubs in Arkansas.


6.Technology Transfer

Number of Non-Peer Reviewed Presentations and Proceedings4

Review Publications
Looper, M.L., Edrington, T.S., Moubarak, A.S., Callaway, T.R., Rosenkrans Jr, C.F. 2008. Effects of the ergot alkaloids dihydroergotamine, ergonovine, and ergotamine on growth of Escherichia coli O157:H7 in vitro. Foodborne Pathogens and Disease. 5(5):25-30.

Looper, M.L., Flores, R., Rorie, R.W., Hallford, D.M., Rosenkrans, C.F. 2008. Endocrine and follicular dynamics are influenced by body condition and somatotropin in post-partum beef cows. Journal of Animal Science. 86:1335-1344.

Last Modified: 10/24/2014
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