Beef cattleselection


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Beef cattleselection

  1. 1. SELECTING BEEF CATTLE Agriscience 332 Animal Science #8399 TEKS: (c)(7)(B)
  2. 2. Introduction Knowledge of selection practices and how to properly apply them can help improve a producer’s herd genetics and economics. Photo by Bill Tarpenning courtesy of USDA Photography Center.
  3. 3. Methods of Selection The methods of beef cattle selection that are used must support the goals of the production system type. The objectives of commercial cow/calf producers and purebred breeders are similar; however, the management practices may be quite different.
  4. 4. The goal of most cow/calf producers is to produce the maximum pounds of calf at the most economical cost. Photo by Gary Kramer courtesy of USDA Natural Resources Conservation Service.
  5. 5. The goal of the purebred breeder is to produce breeding cattle for purchase by other breeders and commercial cow/calf producers. Photo by Bill Tarpenning courtesy of USDA Photography Center.
  6. 6. The three principle considerations for selection of breeding animals are: • Visual appraisal, • Pedigree, and • Performance.
  7. 7. Depending upon the producer’s objectives, varying degrees of emphasis are placed on the selection factors. For example, the purebred breeder often places more emphasis on pedigree than does the cow/calf producer.
  8. 8. Visual Appraisal as a Basis of Selection Selection by visual appraisal has been responsible for much of the genetic improvement of beef cattle.
  9. 9. Visual appraisal can be a good indicator of an individual’s offspring characteristics, such as: • Frame size, • Muscle and body structure, • Predisposition to waste, • Feet and leg structure, and • Breed character.
  10. 10. A close relationship exists between the appearance of a breeding beef animal and its reproductive efficiency, a critical factor in the success of purebred and commercial operations. Breeding cattle must be able to reproduce regularly over a long period of time to be economically productive.
  11. 11. An understanding of beef animal parts and their description is necessary for effective communication in any segment of the beef industry involving live cattle or carcass evaluation.
  12. 12. The following characteristics should be visually appraised: • Body structure, • Soundness of feet and legs, • Muscling and muscle structure, • Frame or skeletal size, • Reproductive soundness,
  13. 13. • Predisposition to waste, • Breed character, • Temperament, and • Conformation score. These characteristics are then combined with production records and pedigree analysis for effectiveness in selecting beef breeding animals.
  14. 14. Body Structure Body structure is a major factor in the visual evaluation of beef cattle. The general body structure of an animal is a good indicator of production characteristics.
  15. 15. Cattle with the correct body structure will be more efficient producers, thus having more potential for economic returns. To evaluate body structure, look for the following factors in the animal.
  16. 16. • The neck of a beef animal should be moderately long, which is an indicator of growth; • The animal should be clean in the throat area; • The loin and rump should be long, wide, and level causing the animal to be long and strong in its back;
  17. 17. • Extremely short-bodied and short- legged cattle are associated with excessive fat deposition and inefficient growth rates; • Long-legged and long-bodied cattle are associated with late maturity and low-quality grades;
  18. 18. • The round of beef cattle should be deep and wide when viewed from the rear, with the widest portion being about midway between the tail head and hock;
  19. 19. • The shoulder should be well- muscled, but free of coarseness; • Offspring with extremely heavy, open shoulders can cause calving difficulties;
  20. 20. • A beef animal should be moderately trim in its rear flank, underline, and brisket, and carry minimal excessive waste; • At the same time, the animal should show good depth of body, indicating body capacity and overall productiveness.
  21. 21. • An animal that has a wide, full heart girth, adequate spring of the fore-ribs, and a wide chest floor and chest indicates proper growth and function of vital organs; and • Adequate width between front and hind legs also indicates good body capacity and muscling.
  22. 22. Soundness of Feet and Legs Visual appraisal of structural soundness is useful in evaluating longevity and productivity. For cattle to travel and remain sound during long productive lives, they must have correct conformation of feet and legs.
  23. 23. Factors to look for when evaluating soundness: • The legs should be squarely set under the four corners of a beef animal and be reasonably straight; • The shoulders should not be too straight, as this may be an indicator of leg problems; and
  24. 24. • Animals that exhibit signs of structural abnormalities should not be selected as potential breeding animals.
  25. 25. Examples of common structural abnormalities of the feet and legs include: Post-legged – hind legs are set too far back, thus making them too straight; Sickle-hocked – hind legs are set too far under the body.
  26. 26. Knock-kneed – front legs are close at the knees and feet are “toed-out”. Pigeon-toed – front feet are “toed-in”.
  27. 27. Bow-legged – hind legs are wide at the hocks and feet are toed-in”. Cow-hocked – hind legs are close at the hocks and feet are “toed-out”.
  28. 28. An animal’s productive longevity is largely dependent on its structural soundness. Longevity is important in all phases of beef production because it affects the number of replacement animals needed to maintain a herd.
  29. 29. An animal’s movement should be free and easy as opposed to being uncoordinated, slow, stiff, and restricted. Animals with uneven, small, curled, or twisted toes and crooked feet usually become lame and should not be selected.
  30. 30. Unsound feet, legs, and joints affect the ability of bulls to follow and breed cows, which reduces herd productivity. Breeding animals with feet or leg problems are not physically capable of being productive over an extended period of time.
  31. 31. Muscling and Muscle Structure Evaluating muscling is another important factor to consider when visually appraising beef cattle. Muscling is the source of meat for consumers and, therefore, is essential to evaluate.
  32. 32. Muscling is indicated by: • Conformation, • Overall thickness and fullness, and • Muscular development in relation to skeletal size.
  33. 33. Bulls Thick, heavy, long muscling is desired by bulls and is indicated by: • Length and size of muscling in the forearm and gaskin areas; • Width and bulge of muscling in the stifle area as viewed from the rear and side;
  34. 34. • Width between the hind legs (both standing and walking); • Thickness, length, and bulge of muscling in the back and loin; and • Expression of muscling in the shoulder and round as the animal moves.
  35. 35. Length of muscling is largely determined by length of bone. If muscling is thick and bulging in one area of an animal’s body, the animal is usually heavily muscled throughout the body.
  36. 36. Animals with extreme muscling, to the point of being impaired in movement or appearing “double- muscled,” should not be selected. “This Piedmontese-Hereford crossbred calf displays classic double muscling because it inherited a defective myostatin gene from both of its parents.” (USDA-ARS) Photo by Keith Weller courtesy of USDA Agricultural Research Service.
  37. 37. Cows and Heifers Muscling in females should be long, smooth, and of moderate thickness. In females, short, coarse, bully muscling is usually a sign of poor reproductive efficiency and low milking ability.
  38. 38. A female’s overall body shape should have a slightly angular appearance, with a slight skin fold shown by the dewlap down the throat and in the brisket area.
  39. 39. The shoulders should be moderately muscled and “clean.” The shoulder blades should extend to the top of the vertebrae, giving a lean appearance to the top of the shoulders.
  40. 40. Frame or Skeletal Size Frame size is a numerical description that refers to an animal’s skeletal size; that is, its height and body length in relation to its age.
  41. 41. Cattle reach mature size and weight and different rates. Age Percent of Mature Height Percent of Mature Weight 7 months 80% 35% - 40% 12 months 90% 50% - 60% Comparison of Rates of Maturity for Height and Weight
  42. 42. Frame size indicates growth, but also is an indirect measure of the composition, or fat-to-lean ratio, of beef animals. Frame size can be used to approximate projected mature size and to characterize performance potential and nutritional requirements of an animal.
  43. 43. A producer should select a frame size that best fits their feed resources, breeding systems, and markets.
  44. 44. Larger-framed cattle, such as most exotic breeds of cattle, tend to grow faster, mature later, be leaner, and produce more pounds of edible beef per day of age than smaller-framed cattle. Image from IMS. Image from IMS.
  45. 45. Small-framed animals, such as most British breeds of cattle, tend to be shorter in stature, earlier maturing for their age, and tend to finish and mature at lighter body weights. Image from IMS.
  46. 46. The Beef Improvement Federation (BIF) has correlated hip height with frame types. When taking this measurement, care must be take to ensure that animals are standing on level ground and that all animals are measured at the same point.
  47. 47. Hip height measurement should be taken at the hip directly above the hook bone.
  48. 48. Most commercial producers use medium-framed cows, as they are more economical. Usually, the cows are bred to large-framed bulls.
  49. 49. Typically, small-framed cows produce calves with less growth potential and have little salvage value.
  50. 50. Large-framed cows are not as economical because they have higher body maintenance requirements. However, some large-framed cows are required in purebred herds to produce large-framed bulls.
  51. 51. Animal scientists at Texas A&M University recommend that bulls be a minimum of frame size 6 (51 inches at the hip) at 12 months of age and weigh 22 or more pounds for each inch of height (minimum of 1,120 pounds).
  52. 52. Mature bulls should weigh a minimum of 1,700 pounds and have a minimum hip height of 57 inches. These researchers also recommend that bulls weigh at least 600 pounds at weaning and exhibit rapid, efficient growth rates, thus maximizing muscle production and minimizing fat deposition.
  53. 53. Age (months) Frame Score 1 2 3 4 5 6 7 8 9 10 11 24 30 36 48 46.4 48.3 50.3 52.3 53.9 56.0 58.0 60.0 62.0 64.0 66.0 47.3 49.3 51.3 53.2 54.9 57.0 59.0 61.0 63.0 65.0 67.0 48.0 50.0 51.9 53.8 55.5 57.5 59.5 61.5 63.5 65.5 67.4. 48.5 50.4 52.3 54.1 55.9 58.0 60.0 62.0 63.9 65.8 67.7 Hip Heights (inches) and Frame Scores for Mature Bulls Source: Beef Improvement Federation Guidelines
  54. 54. Age (months) Frame Score 1 2 3 4 5 6 7 8 9 10 11 24 30 36 48 43.1 45.0 46.9 48.8 50.7 52.5 54.5 56.4 58.2 60.1 62.0 43.8 45.8 47.5 49.4 51.3 53.1 55.1 57.0 58.9 60.8 62.5 44.2 46.1 48.0 49.8 51.8 53.6 55.5 57.2 59.2 61.0 62.8. 44.6 46.5 48.2 50.0 52.0 53.9 55.8 57.5 59.4 61.2 63.0 Hip Heights (inches) and Frame Scores for Mature Cows Source: Beef Improvement Federation Guidelines.
  55. 55. The USDA standards for feeder cattle grading uses three separate frame sizes: small, medium, and large. Frame Size1 Steers weight Heifers weight Small <1100 lbs. <1000 lbs. Medium 1100 – 1250 lbs. 1000 – 1150 lbs. Large >1250 lbs. >1150 lbs. Relationship Between Sex, Weight, and Frame Size Grades Used for Feeder Cattle Grading.
  56. 56. Small-framed Medium-framed Large-framed Image from IMS. Image from IMS. Image from IMS.
  57. 57. Reproductive Soundness Male and female breeding stock need to be evaluated for reproductive soundness. Image from IMS.
  58. 58. Bulls The following factors affect reproductive soundness in bulls: • Bulls should be free of eye problems (e.g., cancer, pinkeye, and cloudy eyes) because good vision is required to find cows that are in heat;
  59. 59. • Soundness of feet and legs is critical because bulls will have to travel in order to mount and mate with females; Image from IMS.
  60. 60. • Testicles should be well- developed, uniform in size, and properly balanced in relation to the age and size of the bull; Image from IMS.
  61. 61. • The scrotum and testicles should be a minimum of 30 centimeters (approximately 12 inches) in circumference on a twelve-month old bull to indicate adequate reproductive ability;
  62. 62. • The sheath region should be “tight” or free from excess skin folds and obstructions; though bulls with Brahman breeding will exhibit a more pendulous sheath; and Image from IMS.
  63. 63. • Bulls should exhibit adequate libido, or sex drive. Image from IMS.
  64. 64. Cows and Heifers The following factors affect reproductive soundness in female cattle: • A productive cow will have a large spring of ribs, indicating adequate body capacity to carry a large, healthy calf;
  65. 65. • Females should be wide and long from hip to pin bones and deep from pins to stifle joint, indicating calving ease; Image from IMS.
  66. 66. • The widest portion of the fertile cow should be the midrib; and Image from IMS.
  67. 67. • The udder should be strongly attached with a level floor and the teats should be proportional to body size. Image from IMS.
  68. 68. Predisposition to Waste The location and degree of fat deposition is very important in the beef industry. Finish affects carcass yield.
  69. 69. Consumers prefer an optimum combination of intramuscular fat (marbling) and total fat (finish). Finish and marbling contribute to the juiciness, flavor, and palatability of meat. Photos by M.A.R.C. courtesy of USDA Agricultural Research Service.
  70. 70. A correct degree of finish is necessary to ensure proper quality and high cutability in the carcass. Photos by M.A.R.C. courtesy of USDA Agricultural Research Service. Carcass with high marbling and low lean-to-fat ratio. Carcass with low marbling and high lean-to-fat ratio.
  71. 71. The degree of finish on a breeding animal will vary depending on the energy level and amount of feed the animal is being fed. The season of the year is also a factor in fat deposition.
  72. 72. Bulls Bulls should naturally show an even, thin distribution of fat, even when they are being fed heavily or during the non-breeding season. Excessively fat bulls will lack libido.
  73. 73. Indicators of predisposition to excessive waste are: • Large amounts of loose hide in the dewlap or brisket, • Excessive depth in the flank, and • Loose hide in the twist.
  74. 74. Cows and Heifers Females should never be fed to excessively fat conditions. Fatty tissue is deposited in their udders and around their reproductive organs, resulting in reduced milk production and lower reproductive rates.
  75. 75. Females will normally deposit more fat in the brisket, along the underline, and over the ribs and back than will bulls, especially during their dry season.
  76. 76. The fat deposits can be advantageous if not excessive, because these cattle will require less feed during the winter, in comparison to “poor-doing” or “hard-fleshing” cattle.
  77. 77. Breed Character Each particular breed of animal is composed of a unique combination of genetics that allows the animal to be recognized as a member of that breed (i.e., its phenotype).
  78. 78. Breed character is the “trademark” or specific identity for the breed that the animal represents. Image from IMS.
  79. 79. In purebreds, the traits that distinguish one breed from another include: • Hair color or hair color patterns, • Head size and shape, • Ear size, shape, and carriage, • Dewlap characteristics,
  80. 80. • Sheath characteristics, • Overall body shape, and • Horned or polled.
  81. 81. If an animal is being purchased as a purebred, it should exhibit the significant characteristics of that breed, thus making it eligible for registration. Image from IMS.
  82. 82. Breeders should purchase the breed or breeds of cattle that will produce the type of offspring most desirable for their production system and end market.
  83. 83. Temperament The temperament, or disposition, of the breeding animal one selects can be important to their overall productivity.
  84. 84. Genetic makeup and environmental conditions are two factors that affect the disposition of cattle. A producer’s handling methods also have a significant impact on an animal’s temperament, but some breeds have a tendency to be more nervous than others.
  85. 85. Frequently, indicators of bad temperament are high-headedness, nervousness, frequent urination, charging, and kicking.
  86. 86. Temperament in cows is critical because gentle, easy-handling mothers usually raise better calves. A bad-tempered bull can be dangerous regardless of his genetic superiority.
  87. 87. Cattle with very poor dispositions should be culled to prevent human injury, decrease excitability of other animals, and minimize repair costs of facilities from damages caused by destructive behaviors.
  88. 88. However, culling is not an effective solution if bad handling is causing the problem. In this case, the handling methods and facilities should be examined.
  89. 89. Sales are often not a good time to make decisions about an animal’s temperament. Frequently, sale animals will express abnormal behaviors because of pre- sale handling and processing. These behaviors may not be a true indicator of the animal’s temperament under normal pasture conditions.
  90. 90. When possible, selection of animals in the pasture is a more desirable option for determining temperament. Image from IMS.
  91. 91. Conformation Scores A conformation score is often provided with sale cattle by a breed association, an individual breeder, or some other authority. Conformation scores are usually based on form, shape, and visual appearance.
  92. 92. Example of conformation scoring system:
  93. 93. This evaluation form could be used in the selection of females, as well as, bulls for a breeding cattle herd.
  94. 94. Pedigree as a Basis of Selection Pedigree data is information on the genotype or performance of ancestors and collateral relatives of an individual. With pedigree selection, animals are selected based on the merit of their ancestors.
  95. 95. If a pedigree is used, greatest value should be placed on the most recent ancestors because of their close genetic relationship to the animal being evaluated.
  96. 96. The genetics in a superior animal is halved in each successive generation; therefore, parents and grandparents are the only animals that will contribute significantly to an offspring’s genotype.
  97. 97. The best uses of pedigree information are in the selection of young animals, before production and performance records are available, and in the selection of highly heritable characteristics such as longevity, yearling weight, and mothering ability. Image from IMS.
  98. 98. Pedigree information is also useful in identifying genetic abnormalities, as well as, selecting for traits expressed only in one sex. However, more emphasis should be placed on individual performance and progeny testing than on pedigree.
  99. 99. Performance as a Basis of Selection Performance testing is the measuring of traits that can be observed and may include either individual performance or progeny testing.
  100. 100. Performance testing usually focuses on the traits that have the greatest economic importance. Image from IMS.
  101. 101. Potentially, the most improvement is offered by those traits that are highly heritable, as indicated in the table on the following page. The heritability percentage identifies that portion of variation that is passed on from parent to offspring.
  102. 102. There are considerable differences in cattle regarding the transmission of economically important traits, such as birth weight, mothering or milking ability, weaning weight, yearling weight, efficiency of gain, carcass merit, and conformation score.
  103. 103. Genetic improvements can be made by evaluating individual performance criteria and using the results of progeny testing. One must understand that these traits are affected by the environment, as well as, by genetics.
  104. 104. Measurements of Reproductive Performance Reproductive performance has the highest economic value of all the traits. Image from IMS.
  105. 105. One of the most important measures of reproductive performance is the weaned calf crop percentage. For each 10% drop in calf crop weaned, an increase of about 20% occurs in production costs (as determined under Texas conditions).
  106. 106. Reproductive performance can be improved through selection, based on carefully kept records of reproduction. Reproductive records that are helpful include conception rate, calf crop percentages (born and weaned), calving interval, and birth weight relative to calving ease.
  107. 107. Conception Rate The conception rate of a herd is determine by comparing the number of breeding age females that conceive or become pregnant to the total number of breeding age females that were exposed to a bull during breeding season.
  108. 108. A conception rate percentage can be calculated by using the following formula. The number of cows that conceived at the end of a breeding season is divided by the number of cows exposed to a bull during the breeding season and then multiplied by 100% to get the conception rate percentage. # Cows Conceived # Cows Exposed X 100% = Conception Rate
  109. 109. If a cattle producer has 100 cows that are exposed to bulls during the breeding season and finds that 95 of the cows are pregnant at the end of the breeding season, the conception rate would be calculated as follows. 95 Cows Conceived 100 Cows Exposed X 100% = 95% Conception Rate
  110. 110. Calf Crop Percentage (Born) Calf crop percentage born is determined by dividing the number of calves born by the number of cows exposed to a bull during the breeding season. # Calves Born # Cows Exposed X 100% = Calf Crop % (Born)
  111. 111. If the cattle producer had 93 calves born out of the 100 cows exposed to bulls during the breeding season, his calf crop % born would be as follows. 93 Calves Born 100 Cows Exposed X 100% = 93% Calf Crop Born
  112. 112. Calf Crop Percentage (Weaned) Percentage weaned is computed by dividing the number of calves weaned by the number of cows that were exposed to bulls during the breeding season. # Calves Weaned # Cows Exposed X 100% = Calf Crop % (Weaned)
  113. 113. If the cattle producer was able to wean 90 calves from the 100 cows exposed to bulls during the breeding season, the percentage of calf crop weaned would be as follows. 90 Calves Weaned 100 Cows Exposed X 100% = 90 % Calf Crop Weaned
  114. 114. Calving Interval Calving interval is a measurement of the average length of time in days between successive parturitions or calvings for all of the breeding age females in a herd.
  115. 115. Calving interval would be calculated for each cow and then an average would be computed for the herd, which would be a measure of the fertility of the herd.
  116. 116. Cow A Calving Dates: 3/1/05 and 3/1/06 = 365 days Cow B Calving Dates: 4/1/05 and 8/1/06 = 485 days Cow B should be culled for poor reproductive efficiency.
  117. 117. Birth Weight Related to Calving Difficulty Average birth weights of offspring should be considered when selecting breeding beef cattle because they are directly related to ease of calving.
  118. 118. Calving difficulty, or dystocia, can increase calf losses, cow mortality, and veterinary and labor costs, as well as, delay return to estrus and decrease conception rates.
  119. 119. Calves that are heavy at birth require a larger birth canal or pelvic area for normal delivery than do lighter calves. Birth weights in excess of 90 pounds usually create calving difficulty. Photo by Scott Bauer courtesy of USDA Agricultural Research Service.
  120. 120. Heifers are more likely to experience calving difficulty; so more care must be taken when selecting bulls for heifers than for cows.
  121. 121. Many producers of breeding stock, especially bulls, will provide buyers with calving ease information, such as calving difficulty scores.
  122. 122. The primary goal of every cow/calf producer should be to produce one live healthy calf from each cow every twelve months. Cows that are incapable of meeting these standards should be culled.
  123. 123. Palpation can assist producers in early detection and elimination of poor producers. Heifer replacements should be selected only from cow with excellent reproductive records.
  124. 124. Fertility Testing of Bulls Fertility testing is an important consideration when selecting a bull. Both young bulls and old bulls, should be fertility tested before being used. Fertility testing involves physical and visual evaluation of the bull’s reproductive soundness.
  125. 125. A breeding soundness exam (BSE), a common method for fertility testing bulls, includes: • A physical examination of the bull’s reproductive system, • A measurement of the bull’s scrotal circumference, and • An evaluation of the bull’s semen.
  126. 126. The bull’s external genitalia can be examined visually and should not exhibit any structural abnormalities. Internal organs of the bull’s reproductive system can be examined for size, shape, and consistency through rectal palpation.
  127. 127. Scrotal circumference should be evaluated because of its relationship to sperm production and semen volume. The bull’s semen should be evaluated for volume, morphology, and motility.
  128. 128. If conception rates are a problem, fertility testing of bulls should not be overlooked. An entire breeding season could be lost by using an infertile sire.
  129. 129. Previously tested, fertile bulls may later experience infertility because of disease, injury, or other reasons. It is a good practice to fertility test before each breeding season.
  130. 130. Measurements of Growth and Gain Performance The following measurements are used to evaluate growth and gain performance: • 205 Days Adjusted Weaning Weight, • Yearling (365-day) and Long Yearling (452 or 550 days), • Post-weaning Rate of Gain, and • Weight Per Day of Age.
  131. 131. Weaning Weights (Adjusted to 205 Days) Weaning weights are used to evaluate differences in mothering ability of cows and the growth potential of calves. For best estimates of genetic worth of weaning weight, it is necessary to adjust individual calf records to a standard basis.
  132. 132. Most organizations that record weaning weights use weights taken between 160 to 205 days and adjust these weights to a uniform age of 205 days.
  133. 133. This procedure is summarized by the following formula. 205-Day Weight (lbs.) = Actual Weight – Birth Weight Age in Days X 205 Days + Birth Weight If the actual birth weight is unknown, 70 can be used for this figure.
  134. 134. The 205-day weight should then be adjusted for the age of the dam and for the sex of the calf. This is necessary for uniformity in evaluating 205-day weights.
  135. 135. The following table can be used to adjust the 205-day weights to a mature dam equivalent for bulls and heifers.
  136. 136. Weaning weight ratios within sex groups are calculated by dividing each individual animal’s 205-day weaning weight, adjusted for age of dam, by the average of its sex group. Weaning weight ratios provide a record of each animal’s deviation from the average of its contemporaries.
  137. 137. Weaning weight ratio is calculated by using the following formula. Weaning Weight Ratio = Individual 205-Day Weight__________ Average 205-Day Weight of Animals in the Group X 100%
  138. 138. Yearling (365-day) and Long Yearling Weights (452 or 550 days) Yearling weights at 365 days are particularly important because of their high heritability and high genetic association with efficiency of gain.
  139. 139. Yearling weight is the best performance measure for selecting bulls. It is closely related to the eventual market weight of the steers to be produced. Usually, the weights are adjusted to a 365-day basis, yearling weight, or to a 550-day basis, long yearling weight.
  140. 140. The following formula is used to calculate yearling weight. Adjusted 365-Day Weight = Actual Final Wt. – Actual Weaning Wt. Number of Days Between Weights X 160 Days + Adjusted Weaning Wt. (205-days)
  141. 141. Adjusted 452-Day Weight = Actual Final Wt. – Actual Weaning Wt. Number of Days Between Weights X 247 Days + Adjusted Weaning Wt. (205-days) Adjusted 550-Day Weight = X 345 Days + Adjusted Weaning Wt. (205-days) Actual Final Wt. – Actual Weaning Wt. Number of Days Between Weights
  142. 142. A yearling weight ratio can be calculated by comparing the individual’s yearling weight to the average of a specific sex group. All animals in a sex group must have been given similar environmental treatment for the weights and ratios to be meaningful and comparable.
  143. 143. The following formula is used for this calculation. Yearling Weight Ratio = ___Adjusted 365-Day Weight of Bull_____ Adjusted 365-Day Weight of All Bulls Tested X 100%
  144. 144. Post Weaning Rate of Gain (Minimum 140 Days on Test) Individual rate of gain testing is usually conducted on bull calves or short yearlings to determine their ability to grow.
  145. 145. Testing the rate and efficiency of gain is very important in bull selection as the timing and length of this test period coincides with the finishing period of the feedlot phase for the calves that the bulls will sire.
  146. 146. Most of the tests are conducted for a period of 140 days. An initial weight is taken at the beginning of the test and a final weight at its conclusion.
  147. 147. The formula for determining rate of gain is shown below. Rate of Gain = Final “Off Test” Weight – Initial “On Test” Weight Total Days on Test
  148. 148. When making comparisons of animals on gain tests, particularly from central gain test stations, weaning weights and weight per day of age should be considered along with the gain test results.
  149. 149. According to researchers at Texas A&M University, bulls on gain tests should have an average daily gain of 3.5 pounds, requiring less than seven pounds of feed for each pound of gain.
  150. 150. An animal’s performance on a test is influenced by the handling and management received prior to the test. Therefore, it is necessary to include pre-test adjustment periods.
  151. 151. A low weight per day of age and a high gain per day of age while on test indicate an extremely low weaning weight or a long period of little or no gain before the cattle were placed on test. This could mean that much of the superiority in rate of gain while on test is compensatory gain instead of genetic ability to grow rapidly.
  152. 152. The compensatory gain may be a result of low weaning weights because of poor mothering ability or other environmental factors.
  153. 153. The rate of gain ratio is a comparison of one animal with the other animals on the 140-day test. A ratio of 100 is the group average. An average daily gain ratio of 110 indicates that a bull is 10% above the group average for rate of gain.
  154. 154. The formula to calculate rate of gain ratio is as follows. Rate of Gain Ratio = _______Individual Rate of Gain________ Average Rate of Gain of Animals in Group X 100%
  155. 155. Weight Per Day of Age The weight per day of age of an individual can be a good indictor of genetic growth potential. However, this measure contains a potentially unreliable variable because it only uses the actual weight of the individual and divides by the actual age in days of the animal.
  156. 156. There are not any adjustments for the age or mothering ability of the individual’s dam or other environmental factors, such as nutritional level after weaning. Any of these variables could influence, either negatively or positively, the animal’s genetic ability for growth.
  157. 157. The formula for calculating weight per day of age is shown below. Weight Per Day of Age = Actual Weight Age in Days
  158. 158. Example of Performance Data for a Bull Many breeders provide a considerable amount of information on sale animals. This information is beneficial to prospective buyers in evaluating the efficiency and productivity of a bull, which aids in selection.
  159. 159. Below is an example of the information provided in an advertisement for bulls completing a test and offered through a sale.
  160. 160. Progeny Testing Progeny testing is a method of evaluating an animal’s breeding value by observing its transmitting ability through a study of the characteristics of its offspring. It is the most accurate method of selection when adequate tests are conducted.
  161. 161. Progeny testing is particularly useful in selecting for carcass traits (when good indicators are not available on live animals), for sex-limited traits (milk production and mothering ability), and for traits with low heritability.
  162. 162. Through the use of progeny testing, breeders can determine differences in the genetic ability of their cattle.
  163. 163. The primary disadvantage of progeny testing is that it is not possible to include cows in the testing program. An individual cow will not produce enough calves in a lifetime for an accurate evaluation, because the generation interval for cattle is too long.
  164. 164. Although not completely accurate, cows can be selected on their production by evaluating their calves at weaning. This factor is based primarily on the cow’s mothering ability. Photo by Bruce Fritz courtesy of USDA Agricultural Research Service.
  165. 165. Carcass Merit Carcass merit is a production trait of a bull that can only be measured through progeny testing. Carcass merit is measured primarily by carcass weight, tenderness, quality grade, and yield grade.
  166. 166. Many cattle breed associations have devised a system for recognizing superior meat sires.
  167. 167. Usually, the evaluation of 8 to 12 carcasses of a bull’s progeny will indicate his probable transmitting ability of carcass traits. However, when evaluating a sire’s progeny for carcass merit, the progeny selected for evaluation should be the result of random matings, be the same sex, and be reared under similar environmental conditions.
  168. 168. Quality Traits When evaluating a sire’s progeny for carcass merit, the carcasses are graded for quality traits based on the overall palatability (tenderness, juiciness, and flavor) of the edible portion of the carcass.
  169. 169. USDA quality grades include prime, choice, select, standard, commercial, and utility. These grades are based on the degree of marbling and the degree of maturity.
  170. 170. Degree of Marbling – intramuscular fat or fat within the muscle is referred to as marbling. The amount and distribution of marbling is evaluated in the cut surface of the ribeye muscle between the 12th and 13th rib. The degree of marbling is the most important factor in determining quality grade.
  171. 171. Degree of Maturity – carcass maturity is based on the physiological age of the animal as indicated by the bone and cartilage characteristics, and the color, texture, and firmness of the ribeye muscle. When evaluating carcasses, emphasis is placed on cartilage and bone maturity.
  172. 172. As an animal ages, cartilage becomes ossified into bone, lean meat darkens in color, and the texture of meat becomes coarser.
  173. 173. Quantity Traits The carcass is also graded for quantity traits based on the amount of marketable meat (boneless, closely-trimmed retail cuts) the carcass will yield. USDA yield grades range from 1 to 5, with YG1 being the highest yielding carcass and YG5 the
  174. 174. Yield grades are based on the following factors: • Amount of KPH fat (kidney, pelvic, and heart); • External fat thickness over the 12th rib, • Area of the ribeye muscle at the 12th rib, and • Hot carcass weight.
  175. 175. Cattle producers should select sires capable of producing superior beef carcasses.
  176. 176. Beef cattle specialists at Texas A&M University recommend that sires selected produce progeny that will yield carcasses grading at least low choice with a minimum “small” degree of marbling and a maximum of 0.04 inches of outside carcass fat per 100 pounds of live weight.
  177. 177. The carcasses should contain ribeyes with areas of 1.1 to 1.4 square inches per 100 pounds of live weight, have a minimum dressing percentage of 60%, and consist of 50% or higher boneless retail trimmed loin, rib, round, and chuck.
  178. 178. Using EBV and EPD in Selecting Beef Cattle Estimated Breeding Value (EBV) is an estimate of an individual’s true breeding value for a trait. EBV is based on the heritability of the trait and the performance of the individual and close relatives.
  179. 179. EBVs for growth traits are generally expressed as ratios. EBVs include the individual’s performance records, as well as records of collateral relatives, such as the sire, dam, sire of dam, and half brothers and sisters.
  180. 180. EBVs are valuable in the selection of young bulls and females for birth weight, weaning weight, yearling weight, and mothering ability (milk).
  181. 181. Example: A bull with an EBV for yearling weight has a genetic potential or estimated breeding value of 8% above the average of those bulls to which he was compared. The value to be placed on this figure is dependent on whether he was compared to other bulls from his herd, to bulls from several different herds, or to many other bulls of his breed.
  182. 182. Expected Progeny Difference (EPD) provides a prediction of future progeny performance of one individual compared to another individual within a breed for a specific trait. The most common EPDs reported are birth weight, milk, weaning weight, maternal influence, and yearling weight.
  183. 183. EPDs are based on a herd or breed average. Different breeds have different bases, which makes it difficult to compare EPDs across breeds. Photo by David Riley courtesy of USDA Agricultural Research Service.
  184. 184. The Expected Progeny Difference (EPD) is equal to one-half of the Estimated Breeding Value (EBV). Using the same bull from the previous example, the amount of change that could be expected in yearling weights of his offspring would only be a 4% increase because the bull transmits half of the trait while the dam transmits the other half.
  185. 185. The accuracy (ACC) of the EPD is given for each trait and reflects the degree of relevance of the information used to calculate an individual EPD. The accuracy is a measure of confidence that the EPD reflects the true genetic merit of an animal.
  186. 186. Accuracy can be classified into three basic categories: • Low (.00 – 0.50), • Moderate (0.51 – 0.70), and • High (0.71 – 1.00).
  187. 187. The use of EPDs allows producers to make comparative selection decisions for beef cattle traits of economic importance. The most economical way that a commercial breeder can obtain the use of proven superior sires is with artificial insemination (AI).
  188. 188. Summary The systematic use of sire summaries, in conjunction with other performance and pedigree data, as well as visual appraisal, can be beneficial tools for beef cattle producers.
  189. 189. Knowledge of selection methods can help producers reduce the risks associated with beef cattle selection and improve the genetics and productivity of their herds.
  190. 190. ALL RIGHTS RESERVED Reproduction or redistribution of all, or part, of this presentation without written permission is prohibited. Instructional Materials Service Texas A&M University 2588 TAMUS College Station, Texas 77843-2588 2007