Catherine Gulliver

Improving reproductive efficiency in ewes: manipulating maternal nutrition to increase ovulation rate and alter the sex ratio of offspring

Manipulation of ewe nutrition offers farmers a viable and sustainable method of improving reproductive efficiency in sheep. These nutritional strategies can be employed firstly, to increase ovulation rates and maximise the number of lambs born, and secondly, to alter the sex ratio of offspring and maximise lamb numbers of the preferred gender.

Increasing ovulation rate

Reproductive wastage is one of the major causes of economic loss to Australian sheep producers and thus to the Australian sheep industry. Loss of potential lambs can occur at several stages during the reproductive cycle, however to maximise lambs produced, ovulation rates need to be maximised (the number of eggs shed and a measure of the potential number of lambs born). Short-term nutritional supplementation (flushing) can increase ovulation rate, without affecting liveweight or body condition score. Catherine’s research will investigate the physiological mechanisms involved; the role of oestrus synchrony in facilitating the short-term flushing mechanism and the efficacy of perennial pasture species in these treatments.

Altering sex ratio of offspring

Stud and commercial sheep operations could benefit from skewing the sex ratio of offspring towards their preferred gender. Prime lamb producers using terminal sires for example, typically prefer male offspring due to their faster growth rates and muscle accumulation. Preliminary evidence indicates that diets high in omega-3 may have anti-inflammatory effects in utero and lead to lower losses of male embryos and, therefore, a higher proportion of male offspring. Catherine’s research will investigate the ability to alter sex ratios in sheep through altering the ratio of omega-3 polyunsaturated fatty acids (PUFA) in the maternal diet and the potential mechanisms involved.

Catherine’s research fall into the CRC’s Program 1 research area and is related to the EverGraze project.

Objectives:

• Increase ovulation rate in unsynchronised ewes through short-term nutritional treatments
• Manipulate pre- and post-conception nutrition of ewes to alter the sex ratio of offspring
• Determine the mechanism behind nutritional alteration of offspring sex ratio.

For more information, email Catherine