Development of bovine feeding regimes, which improve production efficiency, microbiological safety and/or sensory quality of milk
The workpackage departs with studies in two different areas
Interaction between feeding regimes (surveyed under WP2.2) and faecal pathogen shedding
Escherichia coli notably E. coli O157 is an enteric pathogen, which rarely causes disease in cattle, but can cause life-threatening gastro-intestinal infections in humans. Several recent studies have shown that the dairy feeding regime significantly affects the risk of pathogen shedding in the faeces of dairy cows. Recent studies from the USA indicated that calves fed a diet high in Bermuda grass hay (Cynodon dactylon) had on average 10-fold fewer E. coli 0157 than those fed a pre-dominantly grain diet. This is thought to be mainly due to a decrease in colon and rumen pH (due to a higher content of easily digestible carbohydrates) resulting in improved competitiveness and reduced persistence of E. coli in the digestive tract. Factors other than the proportion of grain in the diet may also affect E. coli shedding. For example, feeding high cereal grain diets was associated with increased faecal shedding of E. coli 0157, whereas feeding of soya decreased the incidence.
If studies under WP2.2 indicate that there may be an increased risk of pathogen shedding associated with feeding regimes, which increase the nutritional quality of milk it will be necessary to assess the effect of novel feeding regimes developed to improve the nutritional composition and sensory quality of milk on potential microbiological risk associated with pathogen shedding.
Effect of clover based feeding regimes on milk quality and shelf life
Clover or grass/clover (rather then grass) swards are widely used in organic and “low input” production systems to improve nitrogen content in soils and cows fed legumes rather than grass showed a doubling in the content of polyunsaturated fatty acids (PUFA) in milk from cows. This potentially has important positive effects on various aspects of product quality: increased healthiness for humans of milk and beef, improved spreadability of butter, improved (‘grass-finished’) flavour of beef.
However, increasing the content of PUFA and other compounds (e.g. aldehydes, phytenes, skatole, indole and phenolic compounds) through incorporation of clover in the diet can lead to a reduction in shelf life of milk or meat and lower sensory quality of milk.
To address the technology requirements and deficiencies in knowledge described above we will carry out the following studies (sub-workpackages):
WP4.6.1 Effect of feeding regimes on rumen and hind gut microbial communities and pH, enteric pathogen transfer risk and sensory and nutritional quality of milk. This study will utilise steers with established rumen and hind-gut fistulae and a change-over design with period length determined by pathogen die-off and non-verotoxic E. coli 0157 inocula. Samples of faeces and gut digesta will be taken at intervals over the following few weeks (until pathogen die-off) and analysed for pH and numbers of E. coli.
WP4.6.2 Effect of forage types and/or feed energy supplementation (based on different concentrate types) on production efficiency, quality of milk and/or the maintenance of herd health status and reproductive efficiency. Milk quality analysis will be based on laboratory analytical techniques (solid-phase micro-extraction gas chromatography- mass spectrometry (SPME-GC/MS) and gas chromatography-olfactometry (GC-O). This workpackage will also investigate the integration of feeding regimes with alternative treatments developed under WP4.5 for mastitis control
Environmental and sustainability audits and cost/benefit analyses on novel strategies developed under WP4.6 will be carried out as part of Horizontal activity 1 & 2. The studies under WP4.6 will provide important data/deliverables for SPs 5 & 6 (see graphics).