Introduction to Animal Science

1. Introduction to Animal Science Lactation AGR Vet Science 1-3-2012

2. Lactation

3. Definition of Lactation • The process of producing milk. • Occurs specifically in the mammalian species. • Milk is the food source for the nourishment of the young. • Calcium and Phosphorus • Protein • Carbohydrates & Fat • Vitamins and Minerals

4. Milk • Produced and secreted by the mammary glands of the female. • A liquid containing these major constituents • Water (88%) • Triglycerides (Fat) (3.5 – 9.6%) • Lactose (4 -5%) • Protein (3 – 6%) • Refer to Table 12-1 on page 260 in text

5. Discussion of the udder and mammary gland is like the chicken and egg discussion, where do we start first?

6. Mammary Gland • A milk secreting structure consisting of: • Teats (storage and delivery) • Duct system • Lobes of a secretory system • A modified sweat gland (sudoriferous gland) of the exocrine system • All a part of the total called the udder.

7. Mammary Gland Development • Prenatal – Anatomical structures are present. • Birth to puberty – Structural growth is influenced by somatotropin (growth) hormone. Hormone produced for each species is similar to each other. • Puberty – onset of progesterone and estradiol hormones stimulate the growth of the mammary gland at a rate greater that prepuberty.

8. Development Cont’d • During gestation, progesterone stimulates the lobule-alveolar development. • The lobule-alveolar are responsible for milk synthesis.

9. The Mammary Gland

10. Another View of the Mammary Duct

11. An Udder • A complex organ made up of: • A supportive system • A secretory system made up of epithelial cells (lubule – alveolar) • A duct system for the storage and conveyance of milk • Blood, lymph and nervous systems

12. Supportive System

13. Anatomy and Physiology of the Udder • Anatomically, the udder hangs from the pelvis • Physiologically • Supported by the median suspensory ligament and the lateral suspensory ligaments on each side. • Connective tissue attaches the udder to the abdominal wall. • Connective membranes divide the udder into quarters or halves depending on species.

14. Teat Structure

15. Anatomy and Physiology of the Teat • Exterior portion or visible structure attached to the duct system of the mammary gland. • Limited storage capacity. • Physiologically • Smooth muscle surrounded by skin (epidermal layer of tissue). • Circular muscle form a sphlincter at the base with a teat canal for milk flow or a wax barrier.

16. Hormonal Activities Before, At and Immediately After Parturition Related to Mammary Activity and Lactation • Prolactin • Released from the anterior pituitary gland • Initiates and maintains lactation • Progesterone and estrogen • Decreases abruptly at parturition • Lactogenesis begins with decrease • Oxytocin • Released by the posterior pituitary gland • Responsible for milk letdown from the ducts of the udder

17. Circulatory System Related to the Mammary Gland • The primary aorta and the cranial epigastric artery provide blood from the heart to the arteries which provide to the udder and its milk producing components. • External iliac artery • External pudic or mammary artery • Subcutaneous abdominal artery • Perineal artery

19. Circulation from Udder to Heart • While arteries carry blood from the heart, veins carry blood back to the heart from the udder. • Vena cava • External iliac vein • External pudic vein • Subcutaneous abdominal vein

21. 100 Days & 106 Days of Gestation

22. Milk Production or Lactogenesis • Colostrum produced Stage I lactogenesis • Specialized milk produced in the early days following parturition to provide extra nutrients and immunology to the newborn offspring. • Contains immunoglobulins produced by the mother’s immune system. Antibodies are specific to mother. • Easily absorbed into the digestive tract for 2-3 days after birth. • Contains higher levels of milk proteins and lipids. • Contains higher levels of Vit. A & D as well as iron (note exception in swine)

23. Feeding Orphans Colostrum • Use frozen colostrum from your farm • Old ice cube trays work well. • Use oesapageal feeding tubes to get young animals too weak to feed on their own. • Never feed young unless standing. • Allow them to “chew” down the tube, thus avoiding the wind pipe and drowning or causeing lung infections.

24. Mares’ Waxing

25. Lactogenesis Stage II • The primary structures of the gland are the alveoli. • Milk is secreted by the secretory cells that surround the outside of the lumen. • The alveoli are spherical and are capable of storing milk. • The secretory cells are housed in the alveoli and contain the necessary enzymes to produce the components of the milk.

26. Practices to Encourage Oxytocin Production & Milk Letdown • Wash and massage the udder prior the milking with dairy cows. • Maintain are routine in the milk shed. • Play music to drown out unusual or startling sounds. • Play recorded sounds of sow’s nursing to encourage other sow’s to letdown milk.