External feature of mammary gland:
- Udder
- The mammary glands of cow are group together into structure called the udder.
- It is a skin gland; covered with hair (except teats)
- It is separated into halves by intermammary groove
- Proportionally, the fore quarters = 40%: rear quarters = 60% (but variable)
- Rear quarters generally possess 25-50% more secretary tissue than fore quarters
- The udder may have extra teats called supernumary teats
- Mean empty weight variable (13-42kg)
- Depends on breed, stage of lactation, etc.
- The udder increases about 1/3 in size between milking (Depends on proportion of secretary tissue)
- Udder weight and capacity increase is largest between first and second lactation. No significant changes after 6 years
- Udder characteristics changes with lactation and weight decreases with advancing the lactation (pronounced during second and third months)
- External appearance: Select for large udder size (capacity)
Fig: Structure of Mammary glands
2. Teat
- Associated with each quarter’s gland which serves as the exit for secretion.
- Skin of teat is smooth when udder filled with milk, but becomes wrinkled after removed.
- Hair is absent in teat.
Most important characteristics of teat for easy milking should be:
- Sufficient size
- Well placed
- Large enough opening (streak canal)
- Cows with funnel shaped teat produced 12% more milk than cows with cylindrical teats.
3. Supernumerary teats- accessory or extra teats
- May or may not be associated with gland
- 25-50% cows have supernumerary teats.