Recipient Organization
AUBURN UNIVERSITY
108 M. WHITE SMITH HALL
AUBURN,AL 36849
Performing Department
Animal Sciences
Non Technical Summary
The objective of this project is to reduce the negative effects of an endophyte fungus on beef heifer's reproductive efficiency and their offspring's growth efficiency while grazing infected tall fescue. To accomplish our objective we will use a combination of genetic testing and supplementation with a specially developed mineral formulation. The genetic test utilize DNA harvested from hair samples to detect tolerance to grazing endophyte-infected tall fescue. The specially developed mineral supplement will be fortified with a protected vitamin (niacin) known to increase peripheral blood flow. Forty-eight cows will be separated into 2 groups based upon their genetic tolerance to the endophyte. Within each group; 12 dams will receive the mineral mix supplement containing niacin and 12 dams will be maintained on mineral supplement without niacin. Calves born from each animal will be maintained on the same dietary treatments as dam. Liver samples of cow-calf pairs exposed to endophyte-infected tall fescue will be collected for DNA extraction in order to determine gene expression analysis. Genetic and nutritional treatments will be tested in genes related to oxidative stress and immune system (dam) and, muscle growth and early adipose tissue development (offspring). Our hypothesis is that genetically tested infected-tall fescue tolerant beef cow-calf pairs receiving the proposed enriched mineral supplement will be more tolerant to endophyte-infected tall fescue resulting in greater conception rates and offspring's growth performance. Genes impacted by treatments will be used as biomarkers for animal selection. Positive outcomes will encourage cow-calf producers to implement these proposed genetic and nutritional programs.
Animal Health Component
30%
Research Effort Categories
Basic
60%
Applied
30%
Developmental
10%
Goals / Objectives
1) Determine the level of ergot alkaloid detoxification at the cellular level on the liver of genotyped beef heifers and offspring grazing endophyte-infected tall fescue, after supplementation with a mineral mix enriched with rumen-protected niacin.2) Evaluate the occurrence of any alteration in gene expression at the cellular level related to offspring's growth performance due to treatments applied, using liver and skeletal muscle samples.3) Assess the stacked effect of genetic testing for tolerance to fescue toxicosis, mineral and niacin supplementation on heifer's reproductive performance and offspring's growth performance.
Project Methods
We plan to test the effect of mineral supplementation (Fescue EMT, Cargill, Inc. Wayzata, MN), enriched with rumen-protected niacin (Anevis, QualiTech, Inc., Chaska, Minnesota) on 48 genotyped pregnant Angus × Simmental cows and heifers. Cow/heifer and offspring liver and liver/skeletal muscle samples respectively, will be collected to determine gene expression levels and responses to this supplementation strategy. Hair samples will be collected from a total of 153 Angus × Simmental cows and 53 replacement heifers from Auburn University Black Belt Research Station to test them for fescue toxicity resistance using a genetic test (Agbotanica, Columbia, MO). After receiving the results from the genetic test, 48 pregnant animals will be selected for the study and separated in two groups of 24 animals tolerant to fescue toxicity (Star rating = 4 and 5 stars) and 24 animals susceptible to fescue toxicity (Star rating = 0 to 1 star). Within these two groups, we will randomly selected 12 animals that will receive mineral supplementation enriched with rumen-protected niacin on the diet and 12 animals' control (mineral supplement alone). Furthermore, rumen-protected niacin has the aim to increase serum prolactin levels and decrease vasoconstriction and it is required for liver detoxification of portal blood ammonia to urea and liver metabolism of ketones bodies. Cow/heifers will start to receive the mineral supplementation alone or in combination to rumen-protected niacin, three months before calving.The heifer's reproductive stages analyzed will be the last trimester of gestation, the transition period and lactation. After calving, cow/calf pairs will continue grazing ergot alkaloid-contaminated fescue. During these mentioned stages, important physiological, metabolic, and nutritional changes that can significantly affect profitability occurs; these changes are linked to lactation performance, clinical and subclinical postpartum diseases, and reproductive performance.The 48 cow/heifers of the study will be located at Beef Evaluation Center (Auburn, AL) and they will be constantly exposed to endophyte-infected tall fescue seeds prior to biopsy sampling. Treated and control groups will have an assigned pen. Calan gates will be use to ensure individual dose of the mineral mix enriched or not with rumen-protected niacin. Furthermore, fescue seeds offered to the animals will be tested for concentration of ergovaline alkaloids, to determine the specific levels of ergovaline an animal is exposed to. To maintain control of the total ergovaline concentration offered to the animals, hay other than fescue will be provided.The mineral supplement and rumen-protected niacin will be "top dressed" on individual stalls containing each animal's ration (2 pounds) of a soy hulls and corn gluten feed based supplement (50:50). Offspring will be creep-fed and after weaning (~ 9 months old), they will receive progressive increments of supplemental diet until they reach an intake of 4 pounds per day. In order to ensure a daily dose of 5 oz/head/day of the mineral mix and 0.5 grams of rumen-protected niacin, according to manufacturer recommendations, cow/heifers and offspring will be trained to be fed in Calan gates stalls. This will allow us to use the cow/heifer/offspring as the experimental unit.Phenotype data will be collected during summer months to detect animals that exhibit heat stress related traits. These phenotypic measurements include: body weight, body condition scores (BCS, 9 points scale), respiration rate (breaths/min), rectal temperature (?F), hair shedding score and time spent grazing during the daylight hours. Reproductive traits such as pelvic area, calving ease, number of services to breeding, number of days open and Julian calving date will be recorded.Liver biopsies will be performed in cow/heifers at the beginning of the mineral supplementation period, at the beginning of the calving season, at the end of the calving season and before weaning. Skeletal muscle and liver biopsies will be performed in offspring at weaning and, at 30 and 60 days after weaning. Animal IDs will be recorded so that the same animals are biopsied at each time point to provide repeated measures sampling. On each biopsy day, blood will be collected to determine hormonal and metabolic changes due to genetic and nutritional treatment. Upon arrival to the laboratory, blood samples will be centrifuged at 4C for 15 minutes at 2000 rpm and, serum will be isolated from clotted blood and plasma from anticoagulant-treated tubes. Samples will be aliquoted into two even quantities for long-term storage at -80?C prior to analysis. Serum quantification of metabolic indicators includes concentrations of lactate dehydrogenase (LD), aspartate transaminase (AST), alanine transaminase (ALT) and creatine kinase (CK). These metabolites will be analyzed at the Clinical Pathology Lab (Auburn University Vet School). Furthermore, serum prolactin levels will be tested in all heifers at Dr. Brandebourg's lab (Auburn University - Animal Science department) as means of determining if fescue toxicosis is occurring within an animal. Endocrine effects in steers associated with infected tall fescue include reduced prolactin levels. Plasma samples will be used to measure luteinizing hormone (LH) concentration in heifers using radioimmunoassay (Dr. Goodman's lab - West Virginia University).After finalizing sample collection, mRNA samples will be extracted from liver and skeletal muscle tissue using the TRIzol Reagent protocol for total RNA extraction (Invitrogen, Carlsbad, CA). Genes that are known to be biological candidate genes for heat stress (PRLH, SOD2 and SOD1), toxic fescue tolerance (DRD2), increased Proline (PYCR1) and Serine (PSPH) synthesis, shunting of aminoacid carbons into pyruvate (ALT2), ATP synthesis (NDUFC1, NDUFV2, UCRC, COX4, ATP5D, and ATP5F1), glucocorticoid receptor signaling (NR3C1) and mitochondrial mass (COX4) will be analyzed using RT-qPCR in the liver of heifers. Genes known to be responsible for muscle growth (MTOR, PI3K, S6K, 4EBP1, AKT3) and early adipocyte differentiation (CEBPB, CEBPD), adipogenesis (PPARG, CEBPA, SREBP1) and feed efficiency (TAP2, CAMK2, FOXO1) will be tested in offspring's skeletal muscle. The above mentioned genes to be analyzed on heifer's liver will be tested in offspring's liver as well.Statistical analysis Quantitative PCR data will be analyzed using the MIXED procedure of SAS (SAS 9.4 Institute, Cary, NC, USA). Before statistical analysis, normalized qPCR data (using the geometric mean of 3 housekeeping or internal control genes) will be transformed to fold-change relative to day 0 (i.e., beginning of supplementation with enriched Fescue EMT™). To estimate standard errors at day 0 and prevent biases in statistical analysis, normalized qPCR data will be transformed to obtain a perfect mean of 1.0 at day 0, leaving the proportional difference between the biological replicate. The same proportional change will be calculated at all other time points to obtain a fold-change relative to day 0. Fixed effects in the statistical model for each variable analyzed (i.e., genes, animal performance and blood metabolite) included genetic treatment (T-snip genotyped test), nutritional treatment (enriched Fescue EMT™ and control), and interactions of second and third order. Gene expression data analysis will include a repeated-measures statement with an autoregressive covariate structure. Animal performance and blood metabolites will be also analyzed using the MIXED procedure of SAS. The random effect in all models will be cow/offspring within treatment.