Introduction to Animal Science Lactation AGR Vet Science

Lactation

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

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

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

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.

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.

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

The Mammary Gland

Another View of the Mammary Duct

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

Supportive System

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.

Teat Structure

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.

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

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

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

100 Days & 106 Days of Gestation

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)

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.

Mares’ Waxing

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.

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.