Animal Growth and Development exam 3

What are the two main principles regarding changes in body form during growth

1. Body components that are physiologically more important develop first a. Head → thorax → loin b. Nerve → bone → muscle → fat 2. Extremities complete their development first a. Outside in/'distal to proximal' fashion of development b. What grows first and why? -Nervous Tissue of the brain because it is more important than bone tissue

What is the 'issue'/'gap in the knowledge' the authors addressed for completing their study

Cattle- changes in market demands Chickens- modifications of body composition, precocity, and sexual maturity and in an increase in sexual dimorphism Pigs- using purebred characteristics to estimate crossbred economically important traits Sheep- modeling and genetic control of growth curve variables

Describe the difference between physiological and chronological age of an animal

Chronological- Age in time units (days, months, years) Physiological- Age at physical or chemical maturity

List the events occurring during the fetal to neonate transition

Functioning lungs Redirected circulatory system Suckling reflex Some species - limbs that are fully functional for locomotion within minutes

All of the definitions of heritability share what common description?

Genetics

What factors are included in physiological age

Height, Weight, Composition, Puberty

What does it mean when b is greater than, equal to, or less than 1

If b > 1 = tissue growth rate faster than whole (high growth rate) If b < 1 = tissue growth rate slower than whole (low growth rate) If b = 1 = tissue growth rate same as whole (average/isometric growth rate)

Know the heritability value ranges for low, intermediate, and highly heritable traits.

Low - <.2 Moderate- .2-.4 High- >.4

What are some general characteristics of and factors driving growth

Not uniform adaptations from current to future needs of the animal

What are the 3 classifications of maturity (briefly describe each)

Sexual- able to reproduce Body composition/fatness- sustain pregnancy and lactation Body Size-

What is the chemical composition of fat

a. 5 to 25% water b. Lipid c. Connective tissue d. *dependent on speed of growth* - plane of nutrition - Sex - genotype

What is the chemical composition of muscle

a. 68 to 85% water on a weight basis b. 21% protein c. 6% lipid (1st triglycerides, 2nd phospholipids, 3rd cholesterol)

What is the chemical composition of bone

a. Mostly mineral/ash (60-70%) b. Water content higher during early development (think - cartilage model being replaced) c. As animal ages: ↑ mineral content ↑ fat content ↓ protein content ↓ water content

Compare and contrast age and maturity

Age- how long it has been since the animal was born Maturity- point in time when an animal reaches its highest level of complexity or development

BRIEFLY: What were the overall results, what do they mean, and overall conclusions/implications in the study

Cattle- high grain diet cattle showed better growth and total carcass gain and daily protein gain. High silage diet cattle showed a higher weight and total protein gain. Chickens- sexual dimorphism of body weight at a given physiological age was different than at chronological age Pigs- growth traits were moderate and similar, estimates for carcass traits were higher in purebred Sheep- texel lambs had higher heritability, greater birth weight, and maximum ADG compared to the other breed of lamb

Understand various phases and inflection points for whole animal growth described by sigmoidal/cumulative growth curves

1. Conception 2. Birth 3. Self accelerating phase - exponential growth - Each cell divides into two daughter cells at a constant rate - Supply nutrients and removes waste 4. Point of inflection - Point of maximum growth velocity - Greatest average daily gain 5. Self inhibiting phase - Growth begins to slow and animal reaches mature weight 6. Maturity 7. Senescence - Failure of vital systems

Compare and contrast between the different types of growth curves and be able to identify and label each

1. Cumulative growth- Total weight of the animal 2. Absolute growth- Weight gain per unit of time 3. Relative growth curve- Growth in relation to total weight X,Y axes: 1. Cumulative- time= x axis, weight/ growth unit= y axis 2. Absolute- time=x axis, weight/time= y axis 3. Relative- time= x axis, growth rate/weight= y axis

Give examples of tissues for each allometric growth category as determined by b

1. High Growth Rate (late developing/maturing, b>1) a. Fat, neck and abdominal muscles 2. Low growth rate (early developing/maturing, b<1) a. Bone, some muscles 3. Average growth rate (isometric, b=1) a. Muscle (medial/central tissues)

Explain key processes occurring in the male and female during puberty → discuss changes at the whole body and reproductive tract level

1. Whole body composition a. Males - muscle deposition b. Female - body fatness 2. Reproductive tract a. Males - enlarges testicular size b. Female - ovaries 'activated', uterus size ↑

What are the two main changes occurring in the newly weaned juvenile (provide examples for each)

1. changes in digestion strategies a. Pre-weaning - primary feed source = milk → abomasum 2. changes in dentition - Deciduous teeth aka milk teeth; Smaller roots to fit small jaw size - Deciduous teeth later replaced by permanent teeth

Briefly describe senescence and how it relates to aging

1. decreased functionality of tissues/cells - Exhaustion of progenitor/stem cell populations - Cellular senescence results from a variety of stressors - Senescent cells accumulate during aging - The functionally of the cells and their production of mRNA slows down - Less efficients in shoveling out waste cells - Causes stress

How does chemical composition of each of the tissues discussed change over time

Absolute amount ↑ with age (associated with muscles and tendons) Collagen and elastin fibers ↑ significantly with muscle development As muscles atrophy with age the percentage of connective tissue ↑

Explain quantification of growth on an absolute versus a percent basis

Absolute basis = cumulative weight gain over time Percent basis = proportion of total body weight over time

Know the difference between absolute and percent basis

Absolute basis = cumulative weight gain over time Percent basis = proportion of total body weight over time

Give an examples each of a tissue that grows in an isometric fashion and one that grows in a allometric fashion

Allometric- fat, reproductive tissues, lower limb muscles Isometric- longissimus dorsi (loin)

What is the driving force/goal of the growth phase

Attainment of optimal size - species dependent, for reproduction and maturity

BRIEFLY: how did they measure their objective in the study

Cattle- they took several different breeds of steers and fed them on a high grain diet, or a high silage diet then slaughtered them randomly between years 2 and 3 and extracted the muscle from their left hind quarter Chickens- they experimented on form of growth curve on meat chickens and created function to describe the relationship parameters Pigs- they compared and contrasted growth, meat quality, carcass traits, and comparison of phenotype and genotype Sheep- they recorded and observed female and intact males using graphs and non linear growth functions, then slaughtered half for breed and sex, and the other half for x ray scoring

What was the objective of the study

Cattle- to evaluate effects of select genetic type, and diet energy level on variation in growth and muscle development Chickens- establish whether sexual dimorphism was modified by selection and due to differences in precocity or to a scale effect Pigs- to estimate corresponding genetic correlations between purebred and crossbred performance Sheep- to compare growth in 2 different breeds of lambs to estimate heritability and correlation between growth curve variables

Explain direct and indirect body composition measures

Direct: Kill, grind, sub-sample, and analyze Indirect: Non-invasive Non-destructive

What are some key concepts and determining factors specific to the embryonic and fetal stages of development

Embryonic -Embryo commands uterine space to access nutrient supply Fetal -Early specialized structure formation requires collection, processing and distribution of nutrients and oxygen -Waste removal is also important -Must be compatible with the birth process

Explain what each variable of the allometric growth equation is

Equation: y = axb Y = weight of a specific tissue or component A = a constant X = log weight of total carcass or live weight B = growth coefficient (the slope of the line)

What impact does hybrid vigor/heterosis have on heritability of reproductive and gr

Improved or enhanced traits/performance in hybrid offspring

Internal and external factors of chronological age

Internal factors- drive differences across species, within breeds, or even within sexes within breeds External factors- Nutrition, Disease, Stress, Activity level

Define isometric and allometric growth

Isometric - uniform growth in relation to whole body; less common Allometric - disproportionate growth; more common

What are the different targets of growth

Size Ideal proportion of organs

Explain the growth characteristics associated with the reproductive phase

Variation in relative size of organs and tissues Adipose tissue in females Energy storage to support pregnancy and lactation

What factors drive changes in fat and meat color?

nutrients/diet