Feeding Management at Grass

Aidan Cushnahan, Dairying Development Adviser, Greenmount Campus, College of Agriculture, Food and Rural Enterprise

Introduction

Grazed grass forms a major part of spring and summer diets for dairy cows in Northern Ireland. However grass alone will not always meet the needs of these animals. In order to maximise the economic response to concentrate feeding, it is important to develop a strategy that maximises responses to supplementation while minimising reductions in grass intakes. The following article will highlight factors which affect this strategy.

Is there a need to supplement grass diets?

Supplements should be fed in situations where grass energy intakes are unable to meet the needs of the cow. Situations under which the best responses to concentrate feeding are obtained are as follows

Grazing conditions

Grazed grass can potentially supply up to 27 l/ cow/ day in mid May. However in order to realise this potential, cows must graze around 18 KG dry matter (DM)/ cow/ day (approximately 100 KG fresh grass/ cow/ day). Under cold, wet conditions or situations where grass supply is limited, it will be difficult to achieve these intake targets. Cows grazing under these conditions should receive additional supplementation above their normal allocation. Consider the following options when grazing conditions are difficult:

Select the driest fields for grazing
Create additional access points to the grazing area to reduce damage by poaching
Graze cows for no more than two to three hours daily
Use a back fence to reduce the risk of poaching
Assess grass covers with a view to utilising excess covers when weather conditions improve

Target yield

Cows yielding in excess of 25 l/cow/day will require supplementation in order to minimise loss in condition and maintain herd fertility. It may be argued that this approach could be costly under poor milk prices. However it should be borne in mind that cows which are underfed in early season will produce less milk during the summer and into the autumn at a stage when milk prices are increasing and that the current cost of leasing or buying milk quota is low compared to previous years. In addition responses to concentrate feeding increase as milk production rises. The figures in Table 1 give suggested levels of feeding for cows grazing well managed pastures over a range of milk yields and some suggestions for feeding levels under difficult grazing conditions. It should be noted that the recommendations will change according to the quality of grass available and grass DM intakes which are achieved.

Table 1. Supplementary concentrate levels for high yielding cows under varying grazing conditions

	Milk yield (l/ cow/ day) 25	Milk yield (l/ cow/ day) 35	Milk yield (l/ cow/ day) 40
Normal grazing conditions Grass DM intake (KG/ cow/ day)	18	16	14
Concentrate (KG/ cow/ day)	0	5	10
Margin over feed (£/ cow/ day)	3-55	4-52	4-61
Difficult grazing conditions Concentrate (KG/ cow/ day)	4	8	13
Margin over feed (£/ cow/ day)	3.02	4.13	4.21

Assumes milk price @ 18 ppl, grass cash cost @ £53/t DM and concentrate @ £185/t

Buffer feeding

Many milk producers have had to rely extensively on buffer feeding their cows because of difficult grazing conditions recently. However there are a number of points which should be remembered when developing a buffer feeding plan:

The best responses to buffer feeding occur under difficult grazing conditions and/ or when herd demands cannot be met by the grass available
Design the buffer diet with the milk yield profile of the herd in mind. Herds with a large number of late lactation cows which are fed as one group and are fed a diet designed for early lactation cows will incur higher feeding bills and increase the risk of over conditioned cows at drying off and calving
Extra silage and slurry spreading costs are incurred when cows are housed and buffer fed

Summary

An effective concentrate feeding strategy at grass should target supplements to high yielding cows and animals grazing under difficult grazing conditions. Concentrate feeding at grass is one of the topics which is addressed in the Grass Challenge. Contact your local Dairying Development Adviser to discuss how participating in the Grass Challenge can help to identify the grazing management programme that best meets the needs of your farm

Aidan Cushnahan discusses grass management with Harold Johnston, Ahoghill