Growth and Development Dr. Randy Harp

Growth: Growth is an increase in mass True Growth?? Tissues Bone Internal organs Muscle Fat True Growth??

Growth: Growth is an increase in mass True Growth? Tissues Bone Internal organs Muscle Fat True Growth? Everything except Fat

Normal Postnatal Growth Curves of Bone, Muscle, and Fata Maturity Muscle Growth Units Fat Birth Bone Time Units a Adapted from Boggs, et al, 1998

Normal Growth Curve of Cattlea Units Time Units a Adapted from Berg & Butterfield, 1976 Birth Maturity 1400 lbs 1100 lbs 900 lbs

Age: Physiological Age Chronological Age

Age: Physiological Age Development of the animal relative to maturity Chronological Age Actual Age in days

Fat Tissue Depots: Subcutaneous Fat Internal Fat Intermuscular Fat Intramuscular Fat

Fat Tissue Depots: (order) Subcutaneous Fat ~ Backfat (3rd) Internal Fat ~ KPH (1st) Intermuscular Fat ~ Seam fat (2nd) Intramuscular Fat ~ Marbling (4th)

Normal Postnatal Growth Curves of Bone, Muscle, and Fata Maturity Marbling Muscle Growth Units Fat Birth Bone Time Units a Adapted from Boggs, et al, 1998

Visual Indicators of Finish

Visual Indicators of Finish

Visual Indicators of Finish BF 1.50 REA 10.6 YG 6.0 BF .70 REA 13.5 YG 3.3

Visual Indicators of Finish

Types of Growth: Hyperplasia Hypertrophy Increase in cell number Occurs during Prenatal growth Research indicates that cell number is set Hypertrophy Increase in cell size after birth

Benefits to altering growth: Increase in the amount of product to sell Change composition of saleable product

Methods to alter growth: Natural A) Genetics British vs European/Continental Breeds British ~ “Maternal” Earlier rate of maturity Less muscle more fat Continental ~ “Growth and Carcass” “Terminal” Later rate of maturity More muscle less fat F1 Progeny Heterosis

Factors Affecting Growth: Natural B) Nutrition: 1. Types of growing/finishing cattle a. Grass Cattle - growing b. Finishing- growing/fattening

Methods to alter growth: Adminstered ~ Growth Promoting Agents A) Implants - Made of naturally occurring hormones - Estrogen, Progesterone Ralgro, Synovex, etc. - Synthetics Trenbolone Acetate (TBA)

What Implants do: Improved Feed Efficiency Increased Average Daily Gain Increased Dry Matter Intake Increase in Body Mass

What Implants do: Improved Feed Efficiency 15% Increased Average Daily Gain 10% Increased Dry Matter Intake 5-10% Increase in Body Mass 15-20% Efficiencies and increase in wt gain can result in 50 -150 dollars advantage over non-implanted

Methods to alter growth: Administered ~ Growth Promoting Agents A) Implants B) Beta Agonists

Beta Agonists: Ractopamine HCl - Cattle ~ Optaflex Fed last 28-42 days 100 – 300 mg / day Improvement: 1) Performance F/G, ADG same DMI 2) Dressing Percent 3) Carcass wt 4) No adverse affect on Marbling 5) Tenderness affected at 300 mg Zilpaterol HCl – 6.8 g/ton to provide 60-90 mg/hd/day Fed as Showmaxx via layman OR Fed in feedlots in concentrate form supervised by a DVM