Cymraeg

Body Systems
Session 7 -
The Mammary System Including the Endocrine System

This resource is suitable to support Level 2 Agriculture courses.

Functions of the Udder

Milk is the feed of young animals and is produced and stored in the udder. Cells capable of producing milk develop in the udder as a female animal matures.

  • During pregnancy hormones prepare the cells for milk production and in the final hours of gestation produce milk available to the young animal immediately after parturition.

    • Colostrum

    The first milk produced is colostrums and has a high fat content making it rich in energy.

  • It also provides antibodies for newborn animals. Gradually the dam will produce milk used for rearing the young stock or for sale e.g. dairy cows.

    • Structure of the Udder

    The number of sections and teat will vary according to the type of livestock:

  • Cows – four sections in the udder, each is known as a quarter.
  • Ewes – have two parts to the udder and two teats.
  • Sows –have a large number of independent teats 14-16 (the number and positioning of the teats will be one of the criteria used for selecting replacement gilts).

    • The Cow’s Teat or ‘Quarter’

    The quarter of a cow has a large blood supply.

  • There is a large amount of spongy tissue which contains millions of milk producing cells that are arranged to form small spheres of cells (alveoli).

    • Diagram of the Cow’s Teat

    diagram of teat

    Diagram Showing the Cistern

    Small tubes lead from the alveoli leading to the lower part of the udder where they join together to form the milk duct (or cistern) above the teat. A narrow duct or tube runs through the teat. A band of muscle closes the opening at the end of the teat.

    diagram of cistern

    Milk Let-Down

    For the young to drink the milk or for the cow or ewe to be milked, there must be milk let-down.

  • Milk is released from the cells where it has been produced and it is moved from the alveoli to the lower part of the udder.

    • Oxytocin - the Milk Let-Down Hormone

    Stimuli, such as the calf pushing the udder and sucking the teat or cleaning the teats as part of the pre-milking routine, make the cow release a hormone called oxytocin.

  • The oxytocin is carried in the bloodstream to the udder for the milk let down to occur.

    • Milking Routine

    If the animal is frightened or upset, adrenalin will be released, this will block the oxytocin so the milk will not be let down properly.

  • Milk let-down does not occur instantly so the parlour milking routines must allow time for the hormone to work (60 -90 seconds); therefore five cows may be prepared for milking before returning to the first cow to attach the units.

    • The Endocrine System

    The Endocrine System

    Functions:

  • The endocrine system produces chemicals known as hormones which are secreted into the bloodstream.
  • These hormones carry messages to other parts of the body and produce specific responses.

    • Examples of Endocrine Glands and Hormones

  • Thyroxine
  • Adrenanlin
  • Insulin
  • Oxytocin
  • Oestrogen
  • Progesterone
  • Testosterone

    • Functions of the Hormones

    Thyroxine

  • Controls the metabolic rate - how fast body systems work.

    • Adrenanlin

  • Prepares the body to respond to danger: pulse, breathing and ready to run: blocks milk let-down.

    • Insulin

  • Controls sugar levels in the blood.

    • Functions of the Hormones

    Oxytocin

  • Milk let-down: Uterine contractions at birth.

    • Oestrogen

  • Development at puberty and produces signs of heat-oestrus.

    • Progesterone

  • Maintains pregnancy and prevents any more eggs being released from ovary.

    • Testosterone

  • Controls secondary male sexual characteristics.

    • Where are the Hormones Produced and Secreted From?

    Thyroxine

  • Thyroid gland.

    • Adrenanlin

  • Adrenal gland on top of the kidney.

    • Insulin

  • Pancreas.

    • Oxytocin

  • Pituitary gland.

    • Where are the Hormones Produced and Secreted From?

    Oestrogen

  • Ovaries.

    • Progesterone

  • Ovaries from the corpus luteum and later the placenta.

    • Testosterone

  • Testicles.

    • Growth of the Farm Animal

    When young stock such as lambs or calves grow they develop in a set pattern.

  • The carcass is made up of bones, muscle and fat and the proportion of these tissues will change as the animal matures, the animals’ body shape will also change.

    • Growth Pattern

    A typical growth pattern shows a rapid increase in weight at first, slowing down as the animal reaches puberty.

    diagram of growth rate

    What is the Pattern of Growth?

    Initially there is a high proportion of bone growth followed by an increase in the proportion of muscle, then fat will be deposited.

  • The rate of fat deposition will vary between breeds and this will be considered in the selection of finishing system for stock.

    • The Rate of Growth

    The rate of growth will vary according to:

  • Genetics
  • The environment (including the amount and type of feed available, health)
  • Sex (and whether the males are entire or castrated)

    • Working Out the Growth Rate

    An animal’s growth rate can be calculated by dividing the weight increase by the number of days of growth; this is the daily live weight gain (d.l.w.g.).

  • The d.l.w.g. is usually expressed in kg or grams per day.

    • The formula is:

  • Daily live weight gain = Weight gain ÷ the number of days of growth.

    • Example

    A lamb weighed 5.5kg at birth; it weighed 8.5kg twenty days later. What is the daily liveweight gain?

  • Second weight – birth weight = 8.5kg - 5.5kg = 3.0kg weight increase.
    Days of growth = 20 days.
  • Weight gain = 3.0 kg
    Days of growth = 20 days.
    = 0.15kg/day daily live weight gain
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