Delayed Insemination of Non-Estrual Beef Heifers in 7-day CO-Synch Timed Artificial Insemination

Reproductive performance in cattle is considered to be the most economically important trait and is essential for the success of an operation. In the last decade, timed artificial insemination (AI) in the beef cattle industry has increased in popularity due to the decreased amount of labor required for estrous detection. To increase the use of AI; however, cost and time inputs need to be further decreased. The objective of this study was to determine if fertility could be improved in beef heifers that are not expressing estrus before timed AI by delaying insemination

Factors Affecting Lot Low Choice and Above and Lot Premium Choice Acceptance Rate of Beef Calves in the Tri-County Steer Carcass Futurity Program

Data describing 220 lots of beef cattle in the Tri-County Steer Carcass Futurity program from 2003 through 2007 were analyzed using a multiple regression statistical model to determine specific factors that influence lot low Choice and above rate and lot premium Choice (Certified Angus Beef © ) acceptance rate. Lot low Choice and above rate was similar for years 2005-2007. This rate was significantly lower in 2003 than 2004 but both the 2003 and 2004 rates were similar to the rate in all other years. Lots consisting of heifers had higher (P\u3c.05) low Choice and above rates than lots of steers or mixed-sex pens. The greater the amount of Angus influence in the cattle, the higher the low Choice and above rate (P\u3c.0001). An inverse relationship existed between feedlot in-weight and lot low Choice and above rate; those cattle with lighter feedlot arrival weights had higher % Choice and above rates (P=.0007). Cattle with lower disposition scores (calmer cattle) had higher % Choice and above rates (P=.0496). Low Choice and above rate increased as cattle became less efficient in converting feed to gain (P=.0027). An inverse relationship existed between cost of gain and low Choice and above rate; those cattle with lower cost of gain had higher low Choice and above rates (P=.0043). Lot low Choice and above rate increased as average daily gain increased (P=.0094). Factors examined that did not have a significant effect on lot low Choice and above rate were: mud score at final sort, geographic region of origin, lot mortality rate, number of harvest groups within each lot, days on feed, adjusted final weight, individual treatment cost per head, lot size, and season of harvest. Lot premium Choice acceptance rate was similar in each year from 2003-2006 but was significantly lower in 2007 compared with all other years. Lots consisting of heifers had higher (P\u3c.05) premium Choice acceptance rates than lots of steers or mixed-sex pens. Cattle harvested during the months October through December had a lower lot premium Choice acceptance rate than those harvested during January through March, April through June, or July through September (P\u3c.05). The greater the amount of Angus influence in the cattle, the higher the lot premium Choice acceptance rate (P\u3c.0064). An inverse relationship existed between feedlot in-weight and lot premium Choice acceptance rate; those cattle with lighter feedlot arrival weights had higher premium Choice acceptance rates (P\u3c.0001). Lot premium Choice acceptance rate increased as average daily gain increased (P=.0003); however lots of cattle that were less efficient at converting feed into gain had higher premium Choice acceptance rates (P\u3c.0104). Factors examined that did not have a significant effect on lot premium Choice acceptance rate were: mud score at final sort, individual treatment cost per head, number of harvest groups within each lot, days on feed, cost of gain, lot size, geographic region of origin, average disposition score, adjusted final weight, and lot mortality rate

Oxidation of the Ediacaran Ocean

Oxygenation of the Earth's surface is increasingly thought to have occurred in two steps. The first step, which occurred ~2,300 million years (Myr) ago, involved a significant increase in atmospheric oxygen concentrations and oxygenation of the surface ocean. A further increase in atmospheric oxygen appears to have taken place during the late Neoproterozoic period (~800–542 Myr ago). This increase may have stimulated the evolution of macroscopic multicellular animals and the subsequent radiation of calcified invertebrates, and may have led to oxygenation of the deep ocean. However, the nature and timing of Neoproterozoic oxidation remain uncertain. Here we present high-resolution carbon isotope and sulphur isotope records from the Huqf Supergroup, Sultanate of Oman, that cover most of the Ediacaran period (~635 to ~548 Myr ago). These records indicate that the ocean became increasingly oxygenated after the end of the Marinoan glaciation, and they allow us to identify three distinct stages of oxidation. When considered in the context of other records from this period, our data indicate that certain groups of eukaryotic organisms appeared and diversified during the second and third stages of oxygenation. The second stage corresponds with the Shuram excursion in the carbon isotope record and seems to have involved the oxidation of a large reservoir of organic carbon suspended in the deep ocean, indicating that this event may have had a key role in the evolution of eukaryotic organisms. Our data thus provide new insights into the oxygenation of the Ediacaran ocean and the stepwise restructuring of the carbon and sulphur cycles that occurred during this significant period of Earth's history