Chapter 12 Animal Growth

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

Factors in Animal Growth Heredity Nutrition Environment

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

Stages of Prenatal Growth Ovum Embryonic Fetal

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

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

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

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

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

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

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