ADSC 3600 Midterm: Beef Prod Exam 1

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University of Georgia
Animal and Dairy Sciences
ADSC 3600

Beef Production Exam 1 Review • What 5 factors affect the rate witch which populations can be changed by selection. HSGGN a. Heritability b. Selection differential c. Generation interval d. Genetic correlation e. Number of traits for which 1 selects • Heritability (expressed as h^2) is the proportion of the differences that we observe between animals that can be transmitted to their progeny. • Rank the following in terms of increasing heritability: growth, carcass, and fertility a. Low heritability—fertility, growth, and carcass—High heritability • What’s the heritability equation? Genetic variance / total variance • What’s the genetic change equation? Heritability X Selection differential • Genetic interval is the average age of the parents when the progeny is born. • What’s the average generation interval in beef cattle? 5-6 years • What’s the selection interval equation? Individual – group average • What’s an EPD? ½ breeding value • Change occurs at a rate of what? 1 / square root of traits being selected • ____ is selection for one trait at a time. a. Tandem • What does independent culling level establish? Min and max values that are acceptable for each trait • Selection index is a means of including several traits and different economic weighting factors for each trait. Example: $W • CAB is the largest branded beef product in the USA. • Cattle must have at least 50% black hide to qualify for CAB. • An animal’s color can affect the price it brings. a. Black cattle are more valuable • Epistasis is where genes at one locus affect the expression of genes at another loci. • What is a dilution gene? Incomplete gene; example: roan, grulla • What’s a contemporary group? A group of animals reared together that have the same sex, herd, and year. • Be able to explain calving ease direct: It predicts the differences in the % of unassisted births of a bull when is bred to first calf heifers. • What is large scrotal circumference related to? Lowered age at puberty in daughters • What’s stayability? Longevity • What measurement do we like to see pelvic area in yearling heifers? 144cm • What’s dystocia? Difficulty calving a. Primary cause of dystocia? Disproportionately large calf size or birth weight compared to pelvic area • We breed heifers at 15-16 months of age. What % of their mature body weight should they weight at breeding? 65% • Calculate daily weight gain: (Target weight-actual weight) / days till breeding • What’s an Animal Unit Month (AUM)? The amount of grass it takes to support one cow/calf pair for 30 days • Ranches out west need more or less land per cow? More • What are the 3 categories of slaughter cows? Breaking, boning, and lean • Georgia has approximately how many beef cattle? Average farm size? 1 million; less than 50 head • Frame sizes: a. Large 1250+ lbs b. Medium
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