Enhancement of Sustainable Livestock Grazing through Selection and Training

Enhancement of Sustainable Livestock Grazing through Selection and Training

Summary

Cattle distribution patterns have been recorded by horseback riders and GPS collars at seven ranches in New Mexico, Arizona and Montana. Cows can be classified into hill climbers (use high elevations and steep terrain) or bottom dwellers (use gentle terrain near water). DNA samples from 87 collared cows were analyzed using High Density Single Nucleotide Polymorphism (SNP) technology. Preliminary results indicate grazing distribution is heritable. A relatively low cost DNA test to identify favorable genotypes for grazing distribution is being developed and evaluated. In 2012, two presentations on this project were given in New Mexico and two in Arizona.

Objectives/Performance Targets

1)Evaluate the extent that genetics influence cattle distribution.

1a)Determine if cattle that use rugged terrain far from water are familialy related.

1b)Determine if cattle that use gentle terrain near water are familialy related.

2)Determine if the propensity for cows to use rugged terrain can be identified from the behavior of the bull that sired it.

3)Use identification and selection of adapted cattle at cooperating ranches as a forum and demonstration to train ranchers to develop and implement site-specific grazing management practices.

Accomplishments/Milestones

We have completed cattle tracking activities at seven ranches: 1) Hartley Ranch near Roy, NM, 2) Corona Range and Livestock Research Center near Corona, NM, 3) Chihuahuan Desert Rangeland Research Center near Las Cruces, NM, 4) Heartstone Angus Ranch near Silver City, NM, 5) Todd Ranch near Willcox, AZ, 6) Carter Brangus Ranch, near Thatcher, AZ, and 6) Thackeray Ranch near Havre, MT. At least 10 days of cattle location recording were completed at each of the ranches, which allowed us to characterize the grazing distribution patterns of the cattle in each herd. To date, we have characterized the grazing patterns of over 300 cows and obtained corresponding DNA samples.

This is the first study to conduct genotype to phenotype association studies of difficult to measure quantitative production traits that are important for rangeland sustainability. DNA was obtained from 87 beef cows that were tracked in mountainous and/or extensive rangeland pastures. The DNA was used for high density genotyping (BovineSNPHD; ~800,000 genotypes/cow), and the GPS data were used to characterize use of rough terrain and areas far from water, using indices based on the normalized averages of slope use, elevation use and distance to water. A chromosome region associated with these traits is known as quantitative trait loci (QTL), and the significance is determined by the statistical association of genotypes with phenotype effects (log10 p-value > 5). Significant QTL regions were detected on chromosomes 17 and 29 for slope and elevation (Figure 1). One SNP on chromosome 29 accounted for 25% of the variation in high elevation and steep slope use, and a SNP chromosome 17 accounted for 21% of the variation. When these variables were combined with distance to water, QTL were detected on 11 chromosomes and a structural copy number variant QTL was detected on chromosome 8. A QTL region can span many base-pairs on a chromosome and encompass numerous genes. However, QTL analyses are a useful entry-point for identifying functional loci and potential genetic markers to help understand the genetic and physiological basis of cattle grazing distribution and to develop marker-based genetic selection procedures. This work highlights the value of combining genomic information with accurate grazing distribution phenotypes to understand the biology of cattle foraging behavior.

These extremely promising results require us to develop a new smaller targeted SNP panel to test additional cattle and verify our results. Potentially, we can develop a DNA test that can identify cattle with very superior genotypes for cattle grazing distribution for a cost around $20 per animal (Figures 2a, 2b and 2c). Note: this would be without the need for time consuming measures of grazing behavior or expensive GPS tracking collars.

Preliminary results from this research were presented at the annual meeting of the New Mexico Section of the Society for Range Management on January 5, 2012 in Socorro, NM. Five ranchers and 20 land managers attended the meeting in Socorro. Results from this project were also presented at the Southwest Beef Symposium in Roswell, NM on January 17-18, 2012. Over 40 ranchers from New Mexico and west Texas attended the symposium. During December 6 and 7, 2012, results from this study were highlighted at the Managed Grazing of Beef Cattle on Arizona Rangelands Workshop in Willcox and Payson, Arizona (respectively). The Willcox workshop had 24 participants (primarily ranchers), and the Payson workshop had 37 participants and included ranchers and few land managers from the Forest Service. We will present a one-day symposium on this project and other grazing distribution research at the annual meeting of the Society for Range Management in Oklahoma City, OK on February 5, 2013. We are also planning field tours of cooperator ranches in Arizona and New Mexico during the early summer of 2013 as well as additional grazing distribution workshops.

• Figure 1. Manhattan plot for rough grazing distribution trait. The rough grazing distribution trait is a normalized average of elevation and slope use. The X axis is the position of SNP on each chromosome (University of Maryland genome assembly, v3.1) and the Y axis is the –logP.
• Figure 2b. Heifer 7913 at the Hartley Ranch located near Roy, NM. Tracking locations for this heifer are represented by blue dots in Figure 2c. This heifer had the favorable genotype on chromosome 29 for elevation and slope.
• Figure 2a. Heifer 7710 at the Hartley Ranch located near Roy, NM. Tracking locations for this heifer are represented by pink dots in Figure 2c. This heifer did not have the favorable genotype on chromosome 29 for elevation and slope.
• Figure 2c. Tracking locations of heifers 7710 (pink dots) and 7913 (blue dots) recorded at 15 minute intervals for about 3.5 months (November 13, 2009 to March 5, 2010). Heifer 7710 (Figure 2a) did not have the favorable genotype for elevation and slope use, while heifer 7913 did (Figure 2b). The figure is a 3-d representation of terrain used by the heifers created with a triangulated irregular network (TIN) map in ESRI ArcMap 9.3 software. It was derived from a digital elevation model of the Hartley Ranch located near Roy, NM.

Impacts and Contributions/Outcomes

Grazing distribution is a critical factor in rangeland management. Many of the issues associated with cattle grazing on both public and private lands are associated with undesirable grazing distribution patterns. This project and an earlier Western SARE-funded project show that individual cattle can have very different grazing patterns. If cattle with undesirable grazing patterns are culled and cattle with desirable grazing patterns are selected, most livestock grazing concerns can be alleviated and producers can potentially increase stocking levels while maintaining rangeland health. However, it is critical to know if a trait is heritable before implementing a selection program. This study has established that cattle grazing distribution can be inherited. Preliminary results suggest that the heritability for cattle use of steep slopes and high elevations is likely over 25%. Correspondingly, selection of cattle with desirable grazing patterns can improve grazing patterns and likely resolve most grazing issues without capital intensive improvements such as water developments and fencing.

If we are successful in developing a low cost DNA test for identifying cattle with superior genotypes for grazing distribution, cattle breeders can begin to develop cattle specifically adapted to sustainably used extensive and rugged pastures (a new niche market). Workshops in Arizona showed that well over 75% of rancher participants would be willing to spend additional money on bulls with superior genotypes for grazing distribution.

Outreach efforts from this project will train ranchers and land managers how to manage livestock grazing distribution. Research results will provide a forum upon which approaches to modify cattle grazing patterns other than selection will be presented. This outreach effort will give ranchers and land managers in New Mexico, Arizona and other western states the tools needed to prevent localized overgrazing and sustainably increase grazing capacity of extensive and/or rugged rangeland pastures.

Collaborators: