Final answer:
Milk fever, also known as parturient paresis, typically occurs around the time of calving, especially within 24-48 hours postpartum. It is caused by low blood calcium levels due to increased demands for milk production, especially in cows in their third or older lactations and those bearing twins.
Step-by-step explanation:
Milk fever, or parturient paresis, typically occurs in dairy cows around the time of calving, predominately within 24-48 hours postpartum. This condition is characterized by low blood calcium levels (hypocalcemia) and is often related to the initiation of milk production. Milk fever can lead to a decrease in milk production, and in severe cases, cows can display symptoms such as loss of appetite, weakness, and difficulty standing.
During the late stages of pregnancy and the onset of lactation, the demand for calcium for milk production increases dramatically, and if the cow is unable to mobilize enough calcium from her bones quickly enough, the blood calcium levels can fall, resulting in milk fever.
The risk is particularly high with dairy cows that are in their third or greater lactation and for cows bearing multiples like twins, due to the greater demand for calcium. Hay farming supports the dairy industry by providing a steady diet to milk cows, including during times when grazing is not feasible. Adequate dietary management and calcium supplementation during the transition period can help in the prevention of milk fever.