Recipient Organization
TEXAS A&M UNIVERSITY
750 AGRONOMY RD STE 2701
COLLEGE STATION,TX 77843-0001
Performing Department
Animal Science
Non Technical Summary
Beef cattle production provides a large economic impact in all regions of Texas with approximately 125,000 cow-calf, stocker and feedlot operations and approximately 12.5 million cattle including 4.6 million beef cows and 2.7 million cattle on feed (NASS, 2018). Cow-calf producers in much of the state rely on breeding strategies that incorporate Bos indicus influence in breeding programs (as do producers in other Gulf Coast states and numerous regions of the world) for adaptation and heterosis advantages. However, certain "unusual" aspects have been reported in several trials involving reciprocal Bos indicus-Bos taurus. As more is learned in humans and rodent model species, epigenetic (non-traditional inheritance patterns) influences appear to be important for many body composition and health-related phenotypes in these species, but investigation of this phenomenon is scarce in beef cattle. Furthermore, bovine respiratory disease (BRD) continues to plague the industry, and information regarding incidence precise health phenotypes in Bos indicus influenced cattle limit potential understanding and control. The potential degree of "noise" in beef cattle production systems due to these types of undocumented variation need to be quantified. The over-arching goal of this project is to characterize potential sources of variation in growth, health, and production efficiency traits of beef production systems, with particular emphasis on Bos indicus-Bos taurus crosses. This project should contribute knowledge for increased the competitiveness of Texas and U.S. beef production through improved understanding of input and efficiency variability, and has implications in developing nations for improved food security and financial stability. A brief literature review and discussion of major concepts follow.
Animal Health Component
65%
Research Effort Categories
Basic
15%
Applied
65%
Developmental
20%
Goals / Objectives
This project will utilize predominantly Bos indicus-Bos taurus crossbred cattle to: (1) Evaluate parent-of-origin (i.e. epigenetic) effects for a wide variety of economically important phenotypes, including post-weaning performance and carcass traits, (2) identify (epi)genetic differences for health traits, immune responses and performance measures associated with BRD, (3) investigate economic influences of cattle health and new combinations of health and production phenotypes on economic outcomes, and (4) provide resources for genomic investigation and economic evaluation of multiple phenotypes of beef cattle production traits.
Project Methods
Nellore-Angus cross cattle previously produced in the TAMU McGregor Genomics Project will be utilized, as well new crosses of Brahman and Angus. The structure of these project herds is described below.Animal resources targeted by year of birth:TAMU McGregor Genomics Project (by Cycle):Cycle I - F2 cattle embryo transfer and natural service cattle born 2003-2007Cycle II - Reciprocal F2 cattle (all 4 types) produced by natural service born 2009-2013Cycle III - F3 cattle produced through natural service breeding F2 sons of two bulls to F2 daughters of other two bulls and vice versa born 2009-2013New crosses intended:2019-2020 - Brahman-sired (BA) and Angus-sired (AB) reciprocal F1 crosses2019-2020 - Cycle V Angus-Nellore (F5) crosses2021-2023 - Reciprocal F2 crosses of AB-BA, AB-AB, BA-AB, and BA-BA; possible backcrosses of A and B purebred and AB and BA F12021-2023 - Cycle VI Angus-Nellore (F6) crossesGenomic DNA is banked on all parents and progeny in projects. Approximately 1,600 total animals have been produced in Cycle I-II of the McGregor Genomics Project. Approximately 100 to 200 F1 and F2 Brahman Angus crosses are anticipated per year.For Objective 1 multiple phenotypes are collected and available for analysis including birth weight, weaning weight, and temperament score on approximately 900 progeny. Analyses for Objective 1 will assess the reciprocal F1 and F2 animal types (NA x NA, AN x NA, NA x AN, AN x AN) where sire breed is listed first; NA represents Nellore-sired F1 whereas AN represents Angus-sired F1, and similar designations follow for Angus and Brahman crosses and backcrosses) for calf size, birth weight and weaning weight as well as post-weaning performance and carcass traits.For Objective 2, Cycle II and Cycle III steers were previously stratified by sire and cow family across BRD vaccine treatments of (1) killed, (2) modified live, or (3) no vaccine, and administered an intranasal challenge with BVD virus Type 1b strain. Cattle in the killed group received a primary and booster vaccination with a commercial BRD vaccine on days -56 and -35, respectively; cattle in the modified live group received a single vaccination on day -35. All cattle were challenged intranasally on day 0. Blood and serum have been evaluated for serum neutralizing antibody titers (days -56, -35, 0, 14, 28 and 42) and hematology profile (days 0, 7, 14, 28 and 42). Animals were evaluated for rectal temperature (days 0, 3, 7, 10, 14, 28 and 42) and visual clinical signs of disease (twice daily for 14 days following challenge). For future work involving Angus-Brahman crosses, this approach may be modified to utilize a single vaccination program, but will be determined based on collaborator recommendations.Cattle have individual feed intake and feeding behavior recorded for 70 days (28 days prior to challenge and 42 days following challenge) for Cycle II and Cycle III steers, and this approach is likely to continue for Angus-Brahman cross steers. Temperament based on subjective scoring after weaning and/or objective exit velocity coinciding with the challenge period will be assessed. After the 42-day evaluation period, cattle will be finished and harvested at a commercial beef plant; carcass data including liver abscess and lung color scores will be collected. Individual traits such as titers, feeding behavior, feed intake, rectal temperature, weight, etc. will be analyzed through mixed model procedures as repeated measures of individual steers that incorporates an autoregressive covariance structure to account for different relationships between measurements.For Objective 3, a stochastic approach that has been employed in economic assessments will be investigated to assess impacts of various phenotypes and their interactions on animal performance and profitability. The ability to combine individual component phenotypes in aggregate?type traits for overall classification of health and efficiency-type traits as through an index approach will also be investigated. The ability to assess the economic impact of all the component phenotypes in our data will be pursued.Objective 4 will allow for appropriate genotyping of animals as additional funds become available. Appropriate phenotypes along with pedigree information and DNA continue to be collected as animals become available for future analyses. QTL analyses will investigate parent-of-origin effects.For more detailed methods, please see attached proposal