Final answer:
The reproductive functions in a mare are controlled by the endocrine system, which produces hormones influencing the reproductive cycle and the carrying of a fetus.
Step-by-step explanation:
All reproductive functions in the mare are controlled by hormones produced in the glands of her endocrine system. This system is responsible for producing hormones that function to control and regulate many different body processes, including the reproductive cycle. The reproductive system involves the production and fertilization of gametes and, in females, the carrying of a fetus. Hormonal regulation of the reproductive system is particularly influenced by the hormones from the pituitary gland, the adrenal cortex, and the gonads. During puberty, the hypothalamus produces gonadotropin-releasing hormone (GnRH), which stimulates the production and release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH), directly impacting reproductive functions.