The understanding of the development and growth of an ovulatory follicle within the ovary is important in order to improve the efficiency of breeding techniques such as artificial insemination and embryo transfer. The book highlights the effects of different levels and duration of dietary energy on characteristics of oestrous behaviour by visual observation, follicular development and pregnancy rate in cows. The studies use crossbred Kedah-Kelantan cows which were divided into two groups, I) received grass with maintenance supplement and II) received grass with double maintenance supplement. Oestrous was synchronised with CIDR-B® containing 1.38 g progesterone for 7 days and administered 1 ml synthetic prostaglandin analogue 2 days prior CIDR-B® removal. The knowledge of the study on energy level diets should be especially useful to professionals in nutrition reproduction fields, farmers, undergraduate and postgraduate studies, or anyone else who may be considering how importance of dietary energy level effects on oestrous behaviour and follicular development in order to increase pregnancy rate in cattle.