Progesterone administration in planned reproduction of cattle

Abstract

Cattle are one of the most used species for animal husbandry. The growing demand of products derived from cattle has led to the development of intensive production systems. These systems require a programmed reproduction of the animals to maintain production levels at optimum. Planned reproduction involves the control of the estrous cycle and the use of artificial insemination to assist the reproduction. The estrus control is a hormonal treatment, that can be performed with different protocols, with the aim of manipulate the reproductive cycle to synchronize the estrus in the females. Estrus synchronization presents several advantages relates mainly with the avoidance of estrus detection and facilitate the overall planning including logistics of artificial insemination, grazing and specific nutrition programs, calving dates and vaccination schedules. Progesterone plays a major role in the estrus cycle control programs. Progesterone blood level regulates the secretion and patterns of different hormones that induce estrus and controls the growth and development of follicles and the corpus luteum. Hence, one of the most important step for cycle regulation is the control of progesterone concentration in the animal blood at require time periods. Typically, the reproductive management strategy includes the administration of a exogenous source of progesterone to the animal, releasing the hormone at controlled rates to maintain the concentration at supraluteal levels for a specific period of time. When delivery is disrupted, progesterone concentration falls below the threshold to subluteal levels inducing the beginning of a hormonal-regulated mechanism which will lead to the onset of heat and subsequent ovulation.Several technologies have been developed to deliver the progesterone to the animal body. The most extended is the use of matrices for the sustained administration. These matrices are made from polymeric materials and contain the hormone inside. The polymeric matrices can be fabricated with different geometric shape and can be placed in different sites on the animal body. To date, the principal route of administration is the intravaginal route. Intravaginal devices made of non-biodegradable polymers are the main systems utilized for synchronization purpose. However, some concerns about non-biodegradable materials and other inconvenient related to the use of these intravaginal devices promote new lines of research. The general trend is to simplify the administration of progesterone and develop more-friendly delivery systems. Strategies include reducing the hormone residue in used-devices, the possibility of re-utilize devices, the incorporation of biodegradable polymeric material to fabricate the matrices and the simplification of fabrication process. In this context, this chapter attempts to point out the importance of planning reproduction in production animals and the use of progesterone to control the estrus cycle describing its role, advantages and disadvantages of biodegradable and non-biodegradable delivery devices and future trends in the field of progesterone delivery.