Cattle growth, breeds and breeding Animal Science 144 Beef Cattle & Sheep Production R. D. Sainz Lecture 04 Growth curves 500 400 Body wt, kg 300 200 100 0 0 5 10 15 20 25 30 35 Age, months Allometric growth 100 80 Muscle Wt, kg 60 40 Fat 20 Bone 0 0 50 100 150 200 250 300 Carcass wt, kg 1
Allometric growth curves 250 28% fat Weight, kg 200 150 100 50 0 Frame 5 Frame 7 0 100 200 300 400 500 600 Carcass weight, kg Source: National Beef Cattle Evaluation Consortium: Beef Sire Selection Manual Growth gradients among adipose depots Intermuscular Intramuscular Perirenal Subcutaneous 2
Growth of four body fat depots 120 Weight, kg 100 80 60 40 20 0 0 200 400 600 800 Age, d Intermuscular Subcutaneous Visceral Intramuscular Taste fat vs waste fat Yield grade is a function of the yield of saleable meat, which declines as fat accumulates in extramuscular depots: subcutaneous intermuscular internal/visceral Quality grade is a function of marbling or intramuscular fat -- this gives beef flavor and juiciness Yield Grade = 2.5 + ( 2.50 x backfat) + ( 0.20 x % KPH) + ( 0.0038 x hot carcass wt) ( 0.32 x ribeye area) 3
Retail product yield and backfat Retail product yield, % 60 55 50 45 40 0 2 4 6 8 10 12 14 Backfat, mm Source: Boggs & Merkel, 1993 USDA Quality Grades Source: Meat Evaluation Handbook, 2001 USDA Marbling Scores 4
USDA quality grades Quality grade Marbling score % IM fat Prime Slightly abundant 10.13 High Choice Moderate 7.25 Choice Modest 6.72 Low Choice Small 5.04 Select Slight 3.83 Standard Traces 2.76 From: Bailey, 1976 USDA Grades and Carcass Fat Prices for market weight cattle in the US are determined by their yield and quality grades Yield grade worsens as cattle become fatter Quality grade improves as cattle become fatter The ideal fat content is around 28 to 32%, but this also depends on the distribution of fat Breeding 5
Goals Type of operation Available resources Land Facilities Feed Labor Markets Production goals From: Taylor, RE and Field, TG. 1999. Beef Production and Management Decisions. Prentice Hall, Upper Saddle River, NJ. 6
Important phenotypic & visual traits Overall balance & eye appeal Muscling Topline Feet & leg structure Testicle / udder conformation Eye pigmentation Sound teeth / jaws Temperament 7
Importance of structure and muscling Feet & leg structure Feet & leg structure 8
Structural correctness feet & legs Correct Sickle hocked Post-legged calf Sickle-hocked calf 9
Ideal udder Eye pigmentation Quantitative traits Calving ease Birth weight Weaning weight Yearling weight Scrotal circumference Carcass traits Mature size 10
Most performance and quality traits exhibit continuous variation, i.e. they are quantitative characters Quantitative characters are polygenic, that is controlled by many genes They cannot be followed individually biometric tools are needed The heritability (h 2 ) of a trait expresses the proportion of the total variance in the population that is attributable to genotype Source: National Beef Cattle Evaluation Consortium: Beef Sire Selection Manual From: Ferrell & Jenkins, 1985 11
From: Jenkins & Ferrell, 2002 From: Taylor, RE and Field, TG. 1999. Beef Production and Management Decisions. Prentice Hall, Upper Saddle River, NJ. From: Taylor, RE and Field, TG. 1999. Beef Production and Management Decisions. Prentice Hall, Upper Saddle River, NJ. 12
From: Taylor, RE and Field, TG. 1999. Beef Production and Management Decisions. Prentice Hall, Upper Saddle River, NJ. Genetic progress Rate = 2 h selection differential generation interval So: if average weight of animals in a herd is 500 kg, and we select only animals that weigh on average 550 kg, and the heritability of body weight is 0.30, and the generation interval is 2 years, then Rate of change = [0.30 x (550 500)] / 3 years = 5 kg/year Of course, in practice we would have selection on the male and the female sides; in that case one must perform the above calculation for each sex, then divide each by two and then add them together. (simple, huh?). From: Taylor, RE and Field, TG. 1999. Beef Production and Management Decisions. Prentice Hall, Upper Saddle River, NJ. 13
Ratios Individual's measurement Ratio = 100 Average group measurement Indicates individual rank within contemporary group Average ratio = 100 Used for within-herd selection Expected Progeny Differences Best estimate of what animals are expected to transmit to their offspring Expressed in units of interest (lbs, kg, inches, cm) Predict differences between progeny groups, not actual performances Depend on Performance of individual and relatives Heritabilities Genetic correlations 14
Genetic correlation: two traits are genetically correlated when they are under the control of the same genes. Such a trait changes when a correlated trait is under selection. From: Parnell, PF, Herd, RM, Perry, D and Bootle, B. 1991. Proc. Asian-Australasian Assoc. Breeding Gen. 9:182-185. From: Taylor, RE. 1994. Beef Cattle Production and Management Decisions. MacMillan Publishing Co., New York. 15
Interactions with environment There are major genotype X environment interactions): Brahman SantaGertrudis Shorthorn Temperature, C 10 27 10 27 10 27 Daily gain, kg/d.70.74.89.80.81.56 Ears & dewlap, % area 9.6 7.6 5.0 From: Ragsdale et al., 1957; Johnson et al., 1961, cited by Fuller, MF. 1969. Climate and growth. In: Hafez, ESE and Dyer, IA (Eds.) Animal Growth and Nutrition. Lea & Febiger, Philadelphia. There is a cost associated with environmental adaptability: Brahman influence and meat tenderness 6 a a Shear force, kg 5 4 b ab 3 0 25 50 75 Percentage Brahman From: Johnson,DD, Huffman, RD, Williams, SE, and Hargrove, DD. 1990. Effects of percentage Brahman and Angus breeding, age-season of feeding and slaughter end point on meat palatability and muscle characteristics. J. Anim. Sci. 68:1980-86. Bos indicus vs. Bos taurus Advantages: better adapted to hot climates more resistant to endo- and ecto-parasites lower maintenance requirements stronger maternal instincts leaner meat ( marbling) Disadvantages: poorer performance in cold environments later puberty, inferior reproductive performance lower protein turnover (elevated calpastatin) tougher meat poorer quality grades ( marbling) 16
Source: National Beef Cattle Evaluation Consortium: Beef Sire Selection Manual Source: National Beef Cattle Evaluation Consortium: Beef Sire Selection Manual Source: National Beef Cattle Evaluation Consortium: Beef Sire Selection Manual 17
Source: National Beef Cattle Evaluation Consortium: Beef Sire Selection Manual From: Taylor, RE and Field, TG. 1999. Beef Production and Management Decisions. Prentice Hall, Upper Saddle River, NJ. 18