Increasing the sustainability and reducing the environmental impact of milk production requires an improvement in feed use efficiency and a reduction in greenhouse gas emissions from dairy cows. One means to improve feed efficiency in dairy cattle is to modify rumen fermentation to minimize losses of carbon in the form of methane, or shift the fermentation to end products that are more efficiently used by the animal. Shifting the rumen fermentation pattern also reduces the risk of energy imbalances, particularly in early lactation in higher yielding dairy cows. It is usual for dairy cows that are in early lactation and producing high volumes of milk to experience an imbalance between dietary energy intake and nutrient demand for milk production that results in varying degrees of negative energy balance and consequently mobilisation of body fat. The inability of the liver to metabolise mobilised fat can result in sub-clinical or clinical ketosis. The prevalence of sub-clinical ketosis (SCK) has been reported to be ~22% in European dairy herds, whilst in North America a rate of 43% has been reported. Cows with SCK have an increased odds of developing clinical ketosis, displaced abomasum and metritis and a decreased probability of pregnancy. Antibiotic based compounds are used extensively to manipulate rumen fermentation and improve productivity, but have been banned in animal feeds in Europe. Essential oils are of particular interest as they are natural alternatives to antibiotics and there is a body of evidence supporting the claim that they shift rumen fermentation, reduce the risk of ketosis, and decrease methane production. Decreasing methane production from dairy cows is of particular importance to meet the UK governments pledge of at least a 30% reduction in methane emissions by 2030 compared to 2020.
There have been several studies that have investigated the effects of feeding essential oils to dairy cows, but none have evaluated the efficacy of supplying the product within a slow-release rumen bolus. The provision of essential oils to ruminants in a slow release bolus has two major advantages. Firstly, the loss of volatiles compounds that occurs when essential oils are mixed with feed are eliminated. Secondly, it is easier to administer essential oils to grazing animals when contained in a slow-release rumen bolus. The objectives of this studentship is to determine the effects of essential oils when supplied in a slow release rumen bolus on energy metabolism, methane production and performance of high yielding dairy cows.
All applicants must have a minimum of an upper second class UK honours degree or MSc (or equivalent), in disciplines such as Biochemistry, Animal Sciences, Molecular Biology or a related biological science. A good working knowledge of statistics and statistical analysis software is also required. This project will give training and experience in dairy cow nutrition, feed evaluation and formulation. Consequently, there will be good future job prospects in this area within the UK and elsewhere.
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