Project code: D-31-06

Duration 2 years commencing September 2005

Team and Leader Desmond Patterson & Fiona Young

Organisations Involved ARINI & DARDNI

Background and Summary

Optimisation of supplementation of forage with concentrates is essential to improve efficiency and economic sustainability of dairy cow production systems, as well as reducing the environmental impact of intensive dairy farming in Northern Ireland. 

 However, continuing fertility and health problems indicate that we are not responding effectively to the needs of high genetic merit cows in terms of current feeding and management strategies.  To date, increases in milk yield have been associated with reduced fertility in dairy cows and although the rapid increase in genetic merit for milk production has a major adverse impact, with current reports highlighting conception rates as low as 38% in NI, the precise interaction between nutrition and reproduction still needs to be characterised with this type of animal (Sheldon and Dobson, 2003).

Major nutrients, such as protein, play an important role in an animal’s susceptibility to disease and health status, especially in early lactation. In terms of nutrient requirements, the protein needs of the dairy cow are not as clearly defined as those for energy.  At present, for high yielding dairy cows a crude protein level of approximately 18% in commercial TMR is standard practice.  The proposed study will examine the effects of arrange of protein contents of the diet on the mobilisation of body reserves post parturition, and subsequent replenishment of reserves, in addition to effects on fertility and health, major issues crucial to sustainable milk production.  From an environmental perspective, lower crude protein levels within the diet may ultimately aid in reducing mature N output by increasing the efficiency of N capture in milk. 

In addition, the diets will contain reduced levels of P, which has been shown from current studies (Ferris et al) at ARINI to be sustainable long term, with no detrimental effects on health and fertility in dairy cows.  The overall aim of this study will be to explore the response of high yielding dairy cows to lower protein diets as a means of improving the sustainability of milk production through reducing loss of body reserves in early lactation and reducing the environmental impact.


1.      Measure total lactation yield responses to 3 levels of crude protein in the total diet (185, 15% and 12%)
2.      To monitor the effects of protein content of diet on body condition score, metabolic stress / negative energy balance, milk yield, milk composition, fertility, other health parameters and nitrogen excretion (environmental impact)

Proposed programme:

This study will involve a total of 90 freshly calved dairy cows and heifers (autumn calvers) with 3 treatments applied throughout the winter period, followed by turnout to grass:

1.      18% protein/ high energy diet
2.      15% protein / high energy diet
3.      12% protein / high energy diet



Final report to be submitted to AgriSearch in September 2007



1.      Will assess the sustainability of lower protein levels in diet on milk yield, milk composition, body reserves, health and fertility in high yielding dairy cows.
2.      Will assess the potential benefit of reduced protein levels in terms of environmental impact, including assessment of manure N output per animal (NVZ)
3.      Will assess the overall cost effectiveness of reduced crude protein levels in diets.


Technical report - The effect of protein levels in dairy cow diets on body reserves throughout lactation - Technical Report (D-31-06) 

FileDescriptionFile size
Download this file (D-31-06 Final Report.pdf)D-31-06 - Final ReportD-31-06 - Final Report - The effect of protein levels in dairy cow diets on body reserves throughout lactation850 kB
Download this file (Booklet_16.pdf)Protein levels in dairy cow dietsThe effect of protein levels in dairy cow diets on body reserves throughout lactation - D-31-06567 kB