Genetics and DNA Technology

Cattle Genetics and DNA Technology: A New Era in Cattle Selection in Hawai‘i

Among many factors supporting the Hawai‘i cattle industry, cattle breeds and the genetic makeup of the cattle population have significant impacts. An organized genetic program is necessary for the benefit of the entire industry. To develop an effective cattle genetic program, we believe DNA-based genetic markers for production traits have great potential. Animal production traits such as growth rate, reproduction, body frame and structure, and even adaptability to tropical environments are controlled by genes, or multiple genes in most cases. A gene is a fragment of DNA sequence that encodes a protein sequence. Many important genes have been discovered to be involved in controlling animal production traits. Microsatellites are short, tandem, repeated DNA segments in the genome. Although microsatellites do not encode specific proteins, they have been used as molecular markers for animal genetic analysis and selection. The microsatellite markers vary among individuals sufficiently to have its pattern of inheritance tracked through families, which has several practical applications for cattle breeding, including individual DNA identifications, paternity testing, DNA markers for gene mapping and production traits, and predictions of hybrid vigor. The long-term goal of this project is to identify and test potentially useful cattle genes and microsatellite DNA markers, then to apply the DNA-based testing to cattle selection and crossing for better forage utilization and meat quality. The primary activities for the current year include (1) cattle sample collections and DNA isolation, (2) growth candidate genes and cattle DNA-based parentage test, and (3) cattle growth data analysis.

Cattle Blood Sample Collections and DNA Isolations

The project is an animal genetic project requiring both a large number of animals and quality laboratory
analysis. We have worked on increasing the sample size by maintaining the Angus cattle population
and collaborating with private seedstock cattle ranches. We have collected blood samples of
more than 500 cattle from Hawai‘i and Kaua‘i. All of the genomic DNA isolations from these cattle
have been completed and are ready for various DNA-based tests.

Candidate Genes for Growth Traits and Cattle DNA Parentage Test

Several positional candidate genes have been well associated with animal growth performance in livestock, including myostatin, insulin-like growth factor-1 (IGF-1), Pit-1 gene, growth hormone and growth hormone receptor (GHR). Their mutations and/or single nucleotide polymorphisms (SNP) have been associated with growth traits in cattle, but in great variations. The DNA marker–based selection holds great promise for efficient and effective genetic programs for livestock animals due to accurate laboratory analysis technology. As a limited number of DNA markers are available for the economically important traits, it is important to realize that markers for complex traits like marbling are associated with one of the many genes that contribute to the phenotype traits. The presence or absence of the numerous other “unmarked” or unknown genes and their interactions with environment will actually determine the desired phenotype such as large weaning weight or increased marbling. In the development of DNA markers for beef cattle growth traits, we selected to study DNA polymorphisms of the candidate genes of GHR, IGF-I, and Pit-1 genes. Records from Hawai‘i ranches on breeding cattle for growth performance and other traits are necessary for our primary interest in establishing the genetic associations between DNA markers and growth traits. Our primary interest is to study their values and applications to forage-based cattle production. We are developing PCR and DNA fragment analytic laboratory procedures for these selected genes, and we are analyzing cattle samples. Based on our preliminary data, three alleles for Pit-1, four alleles for IGF-I, and at least four alleles for GHR are possibly present in our current cattle population.

For any one microsatellite marker, multiple possible variations may exist in the population. With a battery of 10 to 20 DNA microsatellite markers, we can produce a unique DNA profile or "fingerprint” for individual cattle. This profile remains as a permanent record of the individual's genetic identity. The polymorphic microsatellites can be accurately detected by multiplex PCR and polyacrylamide gel electrophoresis. By detecting10 microsatellite markers in two panels of multiplex PCR, we have established a practical DNA-based method for cattle identification. We will be testing this method in a multiple-sire mating system and using it to verify breeding records for our experimental animals.

Growth Performance Data Analysis (Angus Plus Cattle)

Angus Plus cattle are Brahman/Angus derivatives that have been derived from purebred lines (Red Angus, Angus, Brahman, Red Brangus) between 65% and 96% registered red or black Angus and a minimum of 4% registered Brahman. Angus Plus combines the genetic makeup of both breeds and is known to have great performance in tropical and subtropical environments. Angus cattle are known as early-puberty, fertile cattle with outstanding carcass traits. Coupled with the Brahman environmental adaptability, longevity, and efficiency, the resulting Angus Plus cattle offer the industry flexibility, including heat tolerance without the extra sheath and ear, reduced infections from parasite problems, overall hardiness, and better forage utilization. Angus Plus females are recognized as easycalving fertile cows with consistent lactation performance, even in hot, humid environments. Angus Plus cattle are moderate-framed, deep-bodied cattle that offer uniformity and efficiency. The cattle are more consistent genetically. The maintenance requirements for Angus Plus cattle are economical due to their moderate frame and easy fleshing ability. Angus cattle start easily on feed and have outstanding appetites, and when processed hang high-quality carcasses that grade. In collaboration with Olumau Angus Plus LLC, we have been working on the growth performance of the Angus Plus cattle population in Kaua‘i. The herd has been selected for preweaning gain, daily gain on pasture grass after weaning, fertility, and mothering ability. H1 cattle have great growth performance on pastureland (Table 2).