Project code:  D-19-04

Duration 12 month extension to existing programme (1st March 05 - 29 February 06)

Team and Leader Drs C Ferris, M McCoy and D Patterson

Organisations Involved ARINI, Hillsborough and Veterinary Science Div., DARD

Background and Summary

This research programme was established to address two important issues, namely pollution by phosphates, and on-farm labour shortages. However since its initiation, environmental legislation in relation to both phosphates and nitrates has become one of the most critical issues for the Northern Ireland dairy industry.

Progress to date: This programme commenced in autumn 2001 with eighty primiparous dairy cows. An additional 20 primiparous dairy cows were added in autumn 2002. These animals have been used in the following studies:

P research: Animals have been managed on either "high" or "reduced" P diets since the start of the study. During the first 2.5 years of the study, dietary P level had no effect on either milk output or milk composition. However, during the third winter period intakes were significantly lower with animals managed on reduced P diets. In addition, while dietary P levels have had no significant effect on fertility, fertility levels have been numerically lower with animals offered reduced P diets. From an environmental point of view, offering reduced P diets to dairy cows reduced the amount of P excreted in faeces by approximately 45%. P intakes were measured on 24 dairy farms during the winter and summer periods of 2004.

Labour research: A total of four studies have been completed, two involving a comparison of two winter feeding systems, and two involving a comparison of two summer grazing regimes. When animals were offered the forage component of the diet twice weekly along a moveable feed barrier, compared to daily via a complete diet, animal performance was unaffected, while feeding times were reduced by 50%. Giving animals access to silage at night during the grazing season had a positive effect on milk production in one study, and a negative effect in another. This difference in response is likely due to the very different grazing conditions and silage qualities offered in the two studies. An ongoing study is examining the efficiency of applying fertiliser on grazing paddocks within 2 - 3 days of grazing, vs. once every three weeks across all paddocks.

Approximately 48 of the original 100 cows are likely to enter the fourth year of the study, including 32 animals that have already completed 3 full lactations on the study. Animals will continue to be managed on their appropriate P diet for a further full lactation. This will provide an opportunity to obtain further information on fertility, and to examine if the significant fall in intakes observed with the reduced P diets in Year 3, is related to long term feeding of lower dietary P levels. If this reduction in intake proves to be a genuine effect, it may call into question the whole concept of reducing dietary P levels to the extent being examined in this study. Additional P balance measurements will also be undertaken. Due to the need to obtain accurate intake data, no additional labour related study will be conducted during the coming winter. However, during the summer the "frequency of fertiliser application" study will be repeated, with this being undertaken using lower fertiliser levels than used in the current study (ie 300 rather than 370 kg N/ha).


September 2004: Start of Year 4 of study

February 2006: Last animal completes study
Final report due to AgriSearch - November 2006


New environmental legislation poses a considerable challenge to our dairy Industry. If reduced P diets are advocated by Government, it is critical to establish that these diets have no adverse effects on animal performance.

Related documents:

Expanding output efficiently in environmentally friendly systems Final Report for AgriSearch, John Thompson and Sons Ltd and Devenish Nutrition Ltd (D-19-04)

Expanding output efficiently in environmentally friendly systems Final Report for AgriSearch, John Thompson and Sons Ltd and Devenish Nutrition Ltd (D-12-01)

FileDescriptionFile size
Download this file (Booklet_18_-_Reducing_Phosphorus_levels_in_dairy_cow_diets.pdf)Reducing phosphorus levelsReducing phosphorus levels in dairy cow diets 226 kB
Download this file (Booklet_17.pdf)Comparisons of dairy cow management strategiesComparisons of dairy cow management strategies which differ in labour inputs537 kB