Project title:    Effect of nutritional management during the first 42 days post calving on ‘lactational’ performance, uterine health, and subsequent reproductive performance post partum
Project leader and team:   Ryan Law and Conrad Ferris  
Duration:  12 months commencing September 2009 
Organisations involved: AFBI

Background to proposal:
Reproductive failure is the predominant reason for culling high yielding dairy cows, and at an estimated annual cost of £18,000 per 100 cow herd, can severely reduce profitability. Although many factors have contributed to the decline in dairy cow fertility, there is a strong relationship between the increased genetic capacity for milk production and reduced reproductive performance.

 Recent modelling studies suggest that under current dairy management practices the modern high yielding dairy system will become unsustainable within 10 years due to increased calving intervals and decreased fertility (Maas et al., 2008). During early lactation, high yielding dairy cows are unable to consume sufficient food to support high levels of milk production, resulting in severe and prolonged periods of negative energy balance and excessive body reserve mobilisation. Research has shown that severe negative energy balance (NEB) increases the interval from calving to the commencement of luteal activity (Canfield and Butler, 1991; Lucy et al., 1992), extends the interval to first service (Butler et al., 1981) and decreases conception rates (Domecq et al., 1997).

Reducing negative energy balance in early lactation is difficult as the cow has a high genetic capacity to produce milk. While nutritional strategies such as increasing the energy density of the diet (for example, through increased concentrate feed levels) may have a role, this may actually increase milk production further. Furthermore, feeding high concentrate levels can lead to rumen acidosis and/or displaced abomasums which may in turn further increase negative energy balance. An alternative approach involves modifying the diet in early lactation to delay the rapid increase in milk production post calving, so that cows reach peak milk yield a little later, closer to the time when dry matter intake is at its peak. The delay in reaching peak yield could be achieved by reducing both concentrate feed levels and total dietary crude protein content in early lactation.  Dietary protein is a key driver of milk production as the cow has a limited capacity to utilise body protein reserves to maintain production (Oldham, 1984). Previous work has demonstrated that reducing the dietary protein concentration suppresses milk production, with no significant effect on dry matter intake, and improves energy balance (Law et al., 2009). Additional benefits associated with the proposed approach may include higher forage intakes in early lactation promoting rumen function once supplementation levels increase, together with a flatter but more sustained lactation curve. 

Objective of the proposed study:

To examine the effect of offering a high forage-low protein diet during the first 28 days of lactation on food intake, milk production, body tissue reserves, metabolic and energy status and reproductive function.

Proposed programme:
This two treatment study will involve 60 winter calving dairy cows, and will run from calving in the autumn until turnout in the spring.  The treatments which will be examined are as follows:

1.  Rapid concentrate build up post calving:  post calving cows on this treatment will be offered a complete diet containing 35% concentrate and 65% forage (grass silage and maize silage) on a DM basis (15.0 % crude protein).  During the first 10 days post calving, concentrate feed levels offered through an out-of parlour feeder will be increased to a maximum of 7.0 kg/cow/day. By day 10 post calving, the total crude protein content of the diet will be approximately 18%.

2.        Delayed concentrate build up post-calving: post calving cows on this treatment will be offered a complete diet containing 35% concentrate and 65% forage (grass silage and maize silage) on a DM basis during the first 28 days post calving (15.0 % crude protein). At day 28 post calving, these cows will start to be offered concentrates through an out-of parlour feeder, with feed levels being increased to a maximum of 7.0 kg/cow/day by day 42 post calving. The total crude protein content of the diet at day 42 will be approximately 18%.

• Milk yield and milk composition
• Liveweights and Condition score
• Dry matter intakes
• Blood metabolites and immune competence
• Liver biopsy (accumulation of liver fat)
• Locomotion score
• Health e.g. mastitis, displaced abomasums, lameness, ketosis
• Classification of vaginal mucus
• Reproductive function, including milk progesterone

Milestones with proposed dates:
1. September 2009 – Commence study with freshly calved cows
2. April 2010 – Completion of study
3. Summer 2010 – Collate data
4. August 2010 - Outcomes of study presented to Industry
5. February 2011 – Final report to AgriSearch

Potential benefits to industry etc:
1. Emerging concept: opportunity to test in Northern Ireland
2. Reducing negative energy balance in early lactation may improve fertility and improve the longevity of the modern high yielding dairy cow.
3. Improved welfare associated with improved energy status
4. Higher forage intakes, and possibly improved performance if a flatter lactation curve is achieved.

Outputs with timescales: 
Scientific: One conference papers and one full scientific paper.
Industry: Presentation of results to visiting farmer groups, in the farming press, at producer meetings, and via AgriSearch newsletters and members meetings
AgriSearch (NI): Preliminary outcomes presented to AgriSearch dairy committee in September 2010, with final report in February 2011.

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