Dairy Cow Nutrition and Lactation Cycles

Lactation Cycles and Persistency

• The lactation cycle is the period between one calving and the next, divided into four phases: early, peak, mid, and late lactation.
• Lactation persistency refers to the rate of decline in milk yield after peak production.
• Higher producing cows tend to have lower persistency.
• Underfeeding cows, especially in early lactation, can reduce peak yield and negatively impact persistency and fertility.

Drying-Off and Dry Periods

• Lactating animals should be given a dry period of around 2 months to allow the mammary tissue to recuperate before the next lactation.
• Proper management of the drying-off process is important to maintain udder health and prepare the animal for the next lactation.

Importance of Milk

• Milk provides nourishment for young, with a high caloric value and a balance of nutrients, easily digested.
• Milk satisfies nutritional needs of the young during early critical period of development.
• Milk provides protection for neonates against disease, primarily in the form of immunoglobulins.
• Milk is a human food source, with dairy industries based on domesticated mammals bred for milk production.

Mammary Gland and System

• The mammary gland is an exocrine gland that produces milk to feed young offspring.
• The mammary system has comparative anatomy, with variations in anatomic position, number, and teat morphology among mammals.
• Cattle have four functional teats and glands, whereas sheep and goats have two; each teat has one streak canal and drains a separate gland.

Factors Affecting Milk Composition and Yield

• Species affects milk composition and yield.
• Breed and individuals within breed affect milk composition and yield.
• Stage of lactation affects milk composition and yield.
• Milk removal frequency and persistency affect milk composition and yield.
• Nutrition affects milk composition and yield.
• Udder health affects milk composition and yield.
• Environmental factors affect milk composition and yield.

Terminologies

• Lactation period: the period after parturition in which the animal produces milk.
• Lactogenesis: the process that initiates milk secretion at the end of pregnancy.
• Galactopoiesis: the maintenance of milk production, requiring prolactin.
• Mammogenesis: the process of structural development (growth) of the mammary gland.
• Udder: the mammary gland of female mammals, with two or more teats hanging near the hind legs.
• Progesterone: a hormone that stimulates breast development and inhibits production of large volumes of milk.
• Prolactin: a hormone that stimulates breast development and affects milk production.
• Colostrum: a concentrated fluid secreted by the breast at the end of pregnancy and shortly after childbirth.
• Oxytocin: a hormone that causes alveolar contraction, milk release, and uterine contractions.

Physiology of Lactation

• Milk production is regulated by several hormonal mechanisms, including prolactin.
• Constant stimulation of the nipple through milking or suckling is important to maintain milk production.
• The composition of milk is important, with fat, lactose, and casein as key components.