Beef Cattle Breeding Project Progress Report: Body Composition EPD Determined from Ultrasound Measures

The Iowa State University beef cattle breeding project was initiated in 1996 and is being conducted at the Rhodes and McNay research and demonstration farms. The project uses the field data of the American Angus Association (AAA) along with the research resource cattle of the farms to study questions that will enhance the genetic investigations using the field data

Beef Cattle Breeding Project Progress Report: Body Composition EPDs Determined from Ultrasound Measures

The Iowa State University beef cattle breeding project was initiated in 1996, and is being conducted at the Rhodes and McNay Research and Demonstration Farms. The project uses the field data of the American Angus Association (AAA) along with the research resource cattle of the farms to study questions that will enhance the genetic investigations using the field data

Beef Cattle Breeding Project Progress Report: Growth-Trait EPDs for 1998- and 1999-Born Calves

The Iowa State University beef cattle breeding project was designed to develop two selection lines of beef cattle for use as a research base to answer questions that influence genetic improvement. The project was started in 1996 and is being conducted at the Rhodes (central Iowa) and McNay (southern Iowa) research and demonstration farms

Prediction of Lean in the Round Using Ultrasound Measurements

Real-time ultrasound (RTU) images were collected on 170 Angus sired steers. These steers had routine carcass data collected, as well as lean mass weights after round fabrication. Lean weight in the round was determined by adding the peeled knuckle, inside round, and outside round weights together. There were four significant independent variables (P \u3c .05) used to predict lean in the round from live measurements. They were: live weight (WT), ultrasound fat thickness between the 12th and 13th ribs (UFT), ultrasound ribeye area between the 12th and 13th ribs (UREA), and gluteus medius lean depth (GM)

Use of Linear and Non-linear Growth Curves to Describe Body Weight Changes of Young Angus Bulls and Heifers

The objectives of the current study were to describe bodyweight (BW) changes of purebred Angus bulls and heifer and to evaluate bias in the adjustment of weaning weight measures to a 205-d age. Linear and non-linear growth functions were used to evaluate changes in BW. Models used were a simple linear regression model fitting cubic polynomial of age at measurement (model I) and a Logistic model (model II) . Predicted mature weight for bulls was 763 kg (1,678.6 lbs.) as compared to 541.9 kg (1192.2 lbs.) for heifers. Bulls attained a maximum average daily weight gain (ADG) of 1.75 kg/d (3.85 lbs/d) at a mean age of 296 d. The maximum ADG attained by heifers was 1.24 lb/d (2.73 lb/d) at a mean age of 261 d. Beef Improvement Federation procedures underestimated 205 d BW of bull calves measured at relatively younger ages and overestimated those measured at later ages. However, the extent of this bias seems to vary depending on the rate of growth of individual calves. The current results suggest that producers should consider creating contemporary groups with a smaller spread in age

Trends in Genetic Parameter Estimates for Ultrasound Back Fat and Rump Fat Thickness Measures in Angus Bulls and Heifers

The objective of the current study was to evaluate heritability and repeatability of serially measured ultrasound 12–13th rib fat thickness (UBF) and rump fat thickness (URF) measures in purebred Angus bulls and heifers.Data included 5000 observations from 912 bulls and heifers.Results from multiple trait analysis showed h2 of 0.29 and 0.40 for yearling UBF and URF, respectively.However, the difference in h2 estimates between yearling measures based on random regression models was smaller.At one year of age, h2 of URF was 0.37 as compared to 0.33 for UBF.Heritability and repeatability values were at their optimum at one year of age. Therefore, yearling bull and 13 to 14 months old heifer ultrasound subcutaneous fat thickness measures from good quality images can be used to evaluate genetic potential of next generation parents in Angus cattle.Information from URF measures may not have an apparent advantage in terms of improving rate of genetic change in percentage retail product in yearling Angus cattle than what could be achieved through selecting against 12th and 13th rib fat thickness

Beef Cattle Breeding Project Progress Report: Growth Trait EPDs for 1998-, 1999-, and 2000-born Calves

The Iowa State University beef cattle breeding project was designed to develop two selection lines of beef cattle for use as a research base to answer questions that influence genetic improvement. The project was started in 1996 and is being conducted at Rhodes (central Iowa) and McNay (southern Iowa) research and demonstration farms

Seasonality in the Surface Energy Balance of Tundra in the Lower Mackenzie River Basin

This study details seasonal characteristics in the annual surface energy balance of upland and lowland tundra during the 1998–99 water year (Y2). It contrasts the results with the 1997–98 water year (Y1) and relates the findings to the climatic normals for the lower Mackenzie River basin region. Both years were much warmer than the long-term average, with Y1 being both warmer and wetter than Y2. Six seasons are defined as early winter, midwinter, late winter, spring, summer, and fall. The most rapid changes in the surface energy balance occur in spring, fall, and late winter. Of these, spring is the most dynamic, and there is distinct asymmetry between rates of change in spring and those in fall. Rates of change of potential insolation (extraterrestrial solar radiation) in late winter, spring, and fall are within 10% of one another, being highest in late winter and smallest in spring. Rates of change in air temperature and ground temperature are twice as large in spring as in fall and late winter, when they are about the same. Rates of change in components of the energy balance in spring are twice and 4 times as large as in fall and late winter, respectively. The timing of snowpack ripening and snowmelt is the major agent determining the magnitude of asymmetry between fall and spring. This timing is a result of interaction between the solar cycle, air temperature, and snowpack longevity. Based on evidence from this study, potential surface responses to a 18C increase in air temperature are small to moderate in most seasons, but are large in spring when increases range from 7% to 10% of average surface energy fluxes

Influence of Hide Thickness on the Ability to Predict Percent Intramuscular Fat with Real-time Ultrasound in Beef Cattle

Seven hundred forty (740) head of cattle were scanned with real-time ultrasound. Models developed by Iowa State University were used to predict percent intramuscular fat on these cattle. Hide thickness was also measured on each animal and the relationship between hide thickness and accuracy of predicting percent intramuscular fat with ultrasound was evaluated. Overall, hide thickness has little effect on accuracy of ultrasound to predict percent intramuscular fat. However some particular groups (i.e. thick hided cattle scanned with Aloka technology) may be prone to underestimation of percent intramuscular fat with ultrasound