Scientists may have paved the way for technologies to help livestock breeders quickly and accurately identify animals with superior qualities.
Researchers at USDA's Agricultural Research Service (ARS) recently completed a pilot project to decipher segments of cattle genes.
The scientists deciphered sequence information on 80,000 DNA segments called expressed sequence tags (ESTs) from cattle. The cattle ESTs represent significant parts of genes that determine the proteins produced by certain tissues such as muscle, ovary and hormone-producing glands.
The scientists also produced clonal "libraries" of expressed genes from a variety of tissues important to livestock growth, composition, reproduction, animal health and food safety. Each of many genes may have a small impact on an inherited trait. But when added together, they may have great economic importance for the livestock industry.
For that reason, ARS scientists and genomics companies are working together to develop technologies called microarrays. Also called gene chips, microarrays can be used to monitor the activity of thousands of genes in a single experiment.
This research also may advance biomedicine. Even before the livestock pilot project was completed, scientists with the not-for-profit Institute for Genomic Research began to perform additional analysis on the sequence information - along with data from the human genome project - to predict the function of many related livestock and human genes.
The ESTs information is accessible through the databases at the National Center for Biotechnology Information. In addition, the clonal libraries soon will be available to other researchers through Children's Hospital Oakland Research Institute, Oakland, CA.
For more information, contact Timothy P. Smith, USDA, ARS, U.S. Meat Animal Research Center, Clay Center, NE, at 402/762-4366, or e-mail [email protected]
Selecting simultaneously for below average birth weight and high yearling weight is a popular strategy for beef producers. It's perceived to result in improved calving ease while maintaining an increasing genetic trend in growth.
But that perception is apparently flawed, say ARS researchers. Their research evaluated changes in the characteristics of mature beef cows resulting from two selection protocols based on juvenile growth.
By selecting either for below-average birth weight and high yearling weight (YB) or for high yearling weight alone (YW), researchers established two sublines of Line 1 Hereford cattle. Direct effects on birth weight and yearling weight diverged between sublines with approximately four generations of selection.
The researchers found the simultaneous selection strategy can result in improved post-natal performance relative to random selection. However, growth performance is compromised somewhat with the resulting cattle becoming earlier maturing and smaller at all ages than under selection for high yearling weight alone.
In making the trade off between yearling weight and birth weight, researchers suggest using the formula: Index =YW-3.2(BW). The index is the value by which to rank the candidates for selection. (See Table 1 below.)
For more information contact Mike MacNeil, USDA ARS, Fort Keogh Livestock and Range Research Laboratory, Miles City, MT, at 406/232-4970 or e-mail [email protected]
The Select Synch protocol - GnRH injection followed one week later by prostaglandin - is effective in synchronizing estrus in anestrous cows as well as cows at all stages of their estrous cycle, according to ARS and Colorado State University researchers.
Artificial insemination resulted in high conception and pregnancy rates; however, estrous and ovarian responses to this protocol depend on the day of the estrous cycle that an individual cow is on when treatment begins, researchers say.
Producers need to initiate estrous detection 24 hours before the prostaglandin injection, as most cows in the later stages of their estrous cycle when treatment begins will exhibit estrus before the injection.
Researchers also emphasize that intense observation of cows for signs of estrus (four hours/day for six days) can be as effective as continuous electronic detection of estrus.
For more information, contact Tom Geary, USDA, ARS, Fork Keogh Livestock and Range Research Laboratory, Miles City, MT, at 406/232-8215.