Growth

What is growth?

  • the process of developing physically, mentally or spiritually

  • progressive development

  • increase in size, complexity, development, etc.

Quantities of growth

  • physical (height and weight)

  • abstract (maturing of organism)

Growth involves a positive change that occurs over time

  • to measure growth, it must be measured at least two times

Can growth ever be negative?

  • yes

    • regression, atrophy

    • old people

Why don’t we see negative growth in livestock?

  • harvested early in life cycle

  • breeding livestock stop producing before significant net loss

Types of growth

  • population growth

    • human population

    • cell culture or bacterial population

    • continues to increase

  • organismal growth

    • total growth

    • growth rate

    • fractional growth

    • we die

Types of growth within cells

  • hypertrophy

    • cell growth in size

    • nutrients, hormones, growth factors, environment

  • hyperplasia

    • cell multiplication (mitosis)

Periods of growth

  • early pregnancy

    • mostly placenta, fluids and hyperplasia of embryo

  • late pregnancy

    • primarily hypertrophy

  • post-natal

    • primarily hypertrophy

History of growth

  • Sir John Hammond (1889-1964)

    • early pioneer of animal physiology

    • recognized patterns of growth

      • growth my organ/tissue system priority

      • sigmoidal curve

  • C. P. McMeeken

    • planes of nutrition

    • bone, muscle and fat deposit differently

    • used hammond’s research

How to we measure growth?

  • changes over time → equation

  • total growth

    • total growth from time1 to time2

    • weight EX: ΔW= WT2 - WT1

    • growth rate

      • rate of change between a certain time

      • weight EX: ΔW= WT2 - WT1, ΔW/time

How do we measure organismal growth

  • not smooth like population

    • “stair step”

  • creates an S-Shaped Curve with different phases

    • initial

      • exponential phase

    • linear phase

    • deceleration phase

    • final

      • steady-state, or maintenance phase

Factors that affect growth

  • Environment

    • climate, social order, pre-natal and post-natal factors, activity level

  • Hormones

    • sex hormones, adrenal gland function, growth hormone, IGF

  • Genetics

    • species, breed, frame size, sex

  • Nutrition

    • physiological status, ration quality/amount, pre/post-natal nutrition

  • Health

    • diseases, puberty, veterinary management, stress

What is development?

  • occurring during the time of growth

  • advancement, maturity, conformation

  • increase in size complexity, maturation, etc

  • occurs over time

  • Dr. Wettemann

    • changes in body conformation and shape and the coordination of body processes

    • acquisition of functions different from those of the original cell type, a result of altered gene expression

  • lower state → higher state of complexity

    • differentiation

      • generation of cellular diversity

    • morphogenesis

      • organization of different cells to tissues

        • nervous, epithelial, muscle, connective

  • 2-6 cell

    • 2n → CNS, bone, muscle, fat

    • why do we mainly care about these parts?

      • marketable parts, important for animal and consumer

When does development start?

  • stages of prenatal development

    • ovum phase

      • from fertilization to implantation

    • embryonic phase

      • from implantation to fetal stage

    • fetal phase

      • from beginning of fetal stage to parturition

Take homes:

  1. what is growth?

    1. who are the major contributors

    2. hypertrophy vs hyperplasia

    3. how do we measure it

    4. periods of growth

    5. sigmoidal curve

  2. what is development

    1. periods of development