Animal Product Technology I is a fundamental course that aims to provide you with a comprehensive understanding of various aspects related to the processing and preservation of animal-derived products. As we explore this subject, we will delve into the techniques, technologies, and principles involved in transforming raw animal products into valuable commodities that meet the needs of consumers.

1. Anatomy and Physiology of Mammary Gland

3. Development of Mammary Gland
Ø The development of the mammary gland starts early in the fetal life.
Ø Already in the second month of gestation teat formation starts and the development
continues up to the sixth month of gestation.
Ø When the calf fetus is six months, the udder is almost fully developed with four
separate glands and a median ligament, teat and gland cisterns.
Ø The developments of milk ducts and the milk secreting tissue takeplace between
puberty and parturition.
Ø The udder continues to increase in cell size and cell numbers throughout the first five
lactations, and the milk producing capacity increases correspondingly.
Ø This is not always fully utilized, since the productive life time of many cows today is
as short as 2.5 lactations.

4. Anatomy of Mammary Gland
v The mammary gland of the dairy cow consists of four separate glands each with a
teat.
v Milk which is synthesized in one gland cannot pass over to any of the other glands.
v The right and left side of the udder are also separated by a median ligament, while
the front and the hind quarters are more diffusely separated.
v The udder is a very big organ weighing, around 50 kg (including milk and blood).
However, weights up to 100 kg have been reported. Therefore, the udder has to be
very well attached to the skeleton and muscles.
v The median ligaments are composed of elastic fibrous tissue, while the lateral
ligaments are composed of connective tissue with less elasticity.

5. Anatomy of Mammary Gland
v The mammary gland consists of secreting tissue and connective tissue.
v The amount of secreting tissue, or the number of secreting cells is the limiting factor
for the milk producing capacity of the udder.
v It is a common belief that a big udder is related to a high milk production capacity.
This is, however, not true in general, since a big udder might include a lot of
connective and adipose tissue.
v The milk is synthesized in the secretory cells, which are arranged as a single layer on
a basal membrane in a spherical structure called alveoli.
v Several alveoli together form a lobule. The structure of this area is very similar to the
structure of the lung.
v The milk which is continuously synthesized in the alveolar area, is stored in the
alveoli, milk ducts, udder and teat cistern between milkings.

6. Anatomy of Mammary Gland
Ø 60-80% of the milk is stored in the alveoli and small milk ducts, while the cistern
only contains 20-40%.
Ø However, there are relatively big differences between dairy cows when it comes to
the cistern capacity.
Ø The teat consists of a teat cistern and a teat canal. Where the teat cistern and teat
Ø canal meet, 6-10 longitudinal folds form the so called Fürstenberg' s rosette, which is
Ø involved in the local defense against mastitis.
Ø The teat canal is surrounded by bundles of smooth muscle fibers, longitudinal as well
as circular.
Ø Between milkings the smooth muscles function to keep the teat canal closed. The teat
canal is also provided with keratin or keratin like substances which between milkings
act as a barrier for the pathogenic bacteria.

9. Physiology of Mammary Gland
Ø The mammary gland is densely innervated especially in the teat.
Ø The skin of the teat is provided with sensory nerves which are sensitive to the
suckling performed by the calf, and thus influenced by pressure, heat and frequency
of suckling.
Ø The mammary gland is very well supported with blood vessels,arteries and veins.
Ø Right and left udder halves generally have their own arterial supply.
Ø The primary function of the arterial system is to provide a continuous supply of
nutrients to the milk synthesizing cells.
Ø To produce 1 liter of milk 500 ltr. of blood have to pass through the udder.
Ø The udder also contains a lymphatic system. It carries waste products away from the
udder.
Ø The lymph nodes serve as a filter that destroy foreign substances but also provide a
source of lymphocytes to fight infections.

10. Milk Secretion and Milk Components
Ø Milk synthesis takes place in the alveoli where the milk secretingcells in the
mammary gland are provided with a continuous supply of nutrients.
Ø Milk fat consists mainly of triglycerides, which are synthesized from glyceroles and
fatty acids.
Ø Long chained fatty acids are absorbed from the blood. Short chained fatty acids are
synthesized in the mammary gland from the components acetate and beta
hydroxybutyrate which have their origins in the blood.
Ø Milk protein is synthesized from amino acids also with origin from the blood, and
consists mainly of caseins and to a smaller extent whey proteins.
Ø Lactose is synthesized from glucose and galactose within the milk secreting cell.
Ø Vitamins, minerals, salts and antibodies are transformed from the blood across the
cell cytoplasm into the alveolar lumen.

11. Induction of Milk Letdown
Ø Physical stimulation of the teats, either by the calf’s suckling or the milkers hands,
excite receptors from which nerve impulses are sending to the posterior pituitary
gland causing secretion of the hormone oxytocin.
Ø The hormone is transported via the blood to the mammary gland. Because both
hormones and nerve impulses are involved in the milk ejection reflex, it is called a
neuro-hormonal reflex.
Ø Oxytocin stimulates the contraction of the alveoli and small ducts thereby emptying
the milk into the larger ducts and the cistern. Hereafter the milk can be evacuated
from the udder.
Ø The contraction of the alveoli may, to some extent, be enhanced by tactile stimuli of
the udder (massaging, squeezing) the so called tap reflex.
Ø When calves suckle, they butt at the udder in order increase milk secretion. Manual
massage of the udder during milking imitates this reflex.

12. Milk Letdown
Ø Milk is initially secreted into small sacs within the mammary gland called alveoli,
from which it must be ejected for consumption or harvesting.
Ø Mammary alveoli are surrounded by smooth muscle (myoepithelial) cells which are a
prominent target cell for oxytocin.
Ø Oxytocin stimulates contraction of myoepithelial cells, causing milk to be ejected
into the ducts and cisterns above the teat.
Ø Oxytocin is released after the cow receives an appropriate stimulus, this can be visual,
aural or physical, and should be predictable and consistent at every milking.
Ø Handling/massage of the teats for at least 15 seconds is a strong stimulus, but cows
can also learn to let down through the association of the dairy environment to the
milking process.
Ø The pressure of milk being forced into the ducts/cistern and down towards the teat
causes the teat to swell with milk and become ‘plump’.

15. Inhibition of Milk Letdwon
v Cows/Buffaloes are sensitive to changes in the environment. They may withhold the
milk if they are uncomfortable with the situation.
v If the animals are stressed, scared or in pain, the hormone adrenaline is secreted. This
hormone causes constriction of the blood vessels, thereby hindering the supply of
sufficient amount of oxytocin to the udder.
v Adrenaline also directly acts on the myoepithelial cells in the alveoli by blocking the
oxytocin receptors.
v The inhibition if milk letdown will result in the leaving of milk in the secretary parts
of the udder.
v Continuous exposure of stress to the buffaloes will affect the milk production
negatively.
v Change of milker or milking routine, application of wrong milking technique or
milking machines in bad conditions are some reasons for the buffaloes to with hold
the milk..

16. Milk Letdown
Ø It takes 60 – 90 seconds for teats to become plump after let down has been initiated.
Ø Cows with well-filled udders require a shorter period of stimulation to elicit milk let
Ø down response than cows with less-filled udders.
Ø The action of oxytocin is essential for emptying of the udder during milking. As
much as 80% of a cow’s milk is unavailable if this oxytocin release is insufficient or
does not occur.
Ø Its let down action lasts for about 5 minutes and is strongest for the first 3 minutes of
milking.
Ø It is important to get the cups attached / hand milking quickly after let down has
started to make full use of the increased udder pressure that occurs.