Animal Nutrition Lecture 7

Lecture 7 notes

Energy Balance

Basically what we’re eating must equal how much energy were exerting, intake must equal expenditure
Controlled variable

Positive Energy Balance

Animal consumes more energy than they use, extra energy can be divided in body tissues as growth or can be expressed as weight gain, can also be in preparation for birth or growth of wool.

Negative Energy Balance

Not enough nutrients compared to energy consumption, signal comes from hypothalamus to either increase feed intake or decrease energy degradation

Homeostatic Regulation

Making sure all internal processes in the body are working as they should be, long term regulation can be achieved by regulation of feed-intake and meal eating.

Intake and Energy Balance: Monogastrics

Simple stomach, more energy concentration less intake to keep energy intake the same each time.

Intake and Energy Balance: Ruminants

Complex stomach, rumen environment dictates energy intake, physical receptors in rumen send signals to stop or start food intake based on volume(fullness) of stomach.

Meal Eating (STR)

dependent on meal interval and meal size, increase of meal interval increases feed intake but decreases meal size.

Physical Signs (STI)

Based on the physical presence of feed in stomach, will either increase or decrease feed intake through signals from the hypothalamus

Chemical Signs (STI)

relies on the concentrations of pH, Volatile fatty acids, and glucose

Glucose recepters

are found in the LIVER

VFA receptors

are found in the rumen wall

pH receptors

are found in splanchnic tissues

Endocrine Signals (STR)

concentrations of hormones affect the signals which affect meal eating

Endocrine Hormones

Gastrin, Cholecystokinin, and Secretin
Control glucose level in blood

Neuroendocrine Hormones

Serotonin, Neuropeptide Y, Somatostatin 
Produced within brain

Short term regulation- Signal Integration

High fiber versus High concentration diet

High fiber diet

VFA and stretch receptors in rumen Wall

High concentration diet

Glucose receptors in liver

Long Term Intake Regulation

Feed intake must increase in times of high production which rises in long term

Energy Demand (LTIR)

Intake doesn’t drive production, excess energy may be stored in body as fat, Demand must be present for the opposite.

Homeorhesis

A physiological state that overrides the bodies metabolic and physical feedback signals, an example would be pregnancy and lactation.