1. Chapter 12
Animal Growth

2. Importance of Animal Growth
Provides earnings for animal producers
Producers earn their livings by:
Managing animals efficiently
Maximizing growth
Minimizing cost

3. Factors in Animal Growth
Heredity
Nutrition
Environment

4. Growth Process Size increases due to:
Hypertrophy: Cell size increase
Hyperplasia: Cell number increase
Growth occurs in two major phases
Prenatal
Postnatal

5. Stages of Prenatal Growth
Ovum
Embryonic
Fetal

6. Ovum Stage Fertilized egg divides Cells form ball-shaped morula
Cells group to form blastula (mass with hollow, fluid-filled cavity)

7. Embryonic Stage Blastula undergoes differentiation
Ectoderm
Mesoderm
Endoderm
Layers become organs through morphogenesis
Embryo attaches to uterus

8. Fetal Stage Organs fully develop Organ cells undergo mitosis
Fetus is expelled during birth
Oxytocin forces fetus out
Contractions forces fluid from lungs
Ground contact starts organ functioning

9. Postnatal Stage Growth is slow as organs develop
Then rapid to sexual maturity
Muscle
Bone
Fat deposits in strategic locations
Abdominal cavity
Between muscles, under skin

10. Growth Control System Glands in endocrine system release hormones
Pituitary
Thyroid
Testicles or ovaries
Adrenal glands
Artificial hormones aid in growth

11. Physiological Age Maturity: Nutrients for fat, not growth Aging begins
Physiologic: Bone solidification
Chronologic: Age in years
Physical characteristics change
Reproductive system slows
Nervous system disintegrates

12. Summary Many factors control animal growth
Agriculturists try to understand factors to produce efficiently
More efficient animals are more economical
Consumers enjoy lower-cost products