Technical Note

Technical Notes
Martin Mulholland

Enhancing milk protein
Tim Keady, Olwen Gormley

Of the main processed dairy products, cheese production and consumption is a growth area. Successful cheese making is largely dependent on the protein content of milk. Improving milk protein concentration also represents an increasingly attractive option for improving returns from milk production with proposed increases in payments and penalties for milk protein. This technical note outlines the major factors influencing milk protein and how milk protein concentrations can be improved through management.

Factors influencing milk protein content

The average protein content of milk supplied in Northern Ireland has risen from 3.15 percent to the current level of 3.19 percent. Milk protein concentration is influenced by many factors including:-

Breed - Channel Island and Ayrshire cows produce milk with a higher protein content than Friesian/Holstein cows.
Stage of lactation - Protein is high at calving, but falls rapidly to a minimum at peak yield and gradually improves towards the end of lactation.
Age of cow - Heifers have higher milk protein than older cows, with a decline of 0.05 percent between the first and fourth lactation.
Seasonal effects - Seasonally low milk production from the autumn calving cow normally results from the combination of stage of lactation and declining nutritional status over the winter.
Cow condition at calving and condition loss post calving - Milk protein drop post calving is due to the cow being in a negative energy balance. The greater the liveweight loss, the lower the milk protein.
Cow health - The effect of internal parasites such as worms and fluke, and production diseases such as mastitis, is to lower the protein quality of milk.
Nutrition - The overall plane of nutrition and the type and quality of foods offered to the cow can have a major impact on milk protein production in the short term.

Management guidelines for improving milk protein

Feeding

Pre-calving nutrition

Prime dry cows for lactation by feeding 2kg/day of high protein (UDP) concentrate properly balanced with dry cow (low calcium) minerals for up to four weeks before calving. Restrict forage intake to avoid excess weight gain. Total milk protein production will be increased either through higher protein concentration in milk or through higher milk yields.

Silage quality

Feeding high D-value, high intake potential silage gives an improvement in milk protein content as a result of increased energy intake. Plan to feed the best first cut silage after the majority of the herd is freshly calved. Cows need to be given unrestricted access to such silage.

Concentrates should have a minimum of 20% starch and include digestible fibre and sugar sources. Starch is provided mainly from cereals. Raising starch levels in the diet consistently increases milk protein levels. Avoid feeding concentrates with high oil levels of over 6.5%.

D-Value of silage %	62	70	73
Silage intake (KgDM/day)	8.1	10.0	10.7
Milk Yield (Kg cow/day)	26.3	28.2	28.9
Milk protein Composition %	3.17	3.22	3.35
Milk fat composition(%)	3.68	3.68	3.77

Second forages (maize silage, fodder beet) or alternative feeds (Brewers grains, pressed beet pulp) can improve energy intake especially when silage quality is moderate

Concentrate type

Straight	Starch %
Maize	65
Wheat	60
Barley	50
Maize gluten	15
Brewer's grain	6

Grazed grass

Grass in the diet improves milk protein in early spring and late autumn. Extending the grazing season beyond the limits of early April and early November increases milk yield and milk protein concentration.

Autumn calvers grazing autumn grass silage plus 6 kgs concentrates	Housed	3 hours Grazing
Silage intake (kg DM/day)	11.0	6.8
Grass intake (Kg DM/day)	-	4.5
Milk Yield (Kg/day)	23.1	25.2
Milk Protein composition (%)	3.14	3.27
Milk Fat composition (%)	4.12	4.00

Breeding

Milk record to identify cows with high milk protein yields from which to breed replacements

Cull cows with low milk protein yields

Select well proven AI sires (reliability over 70%) with high PTAs for fat plus protein yields and high PIN 95 values

From a shortlist of bulls with desirable PINs and conformation, select those with the highest protein percent deviation

Technical note prepared by Martin Mulholland, Greenmount College

With lower milk prices and the resulting effect on dairy cow profitability, the emphasis for many progressive dairy farmers is on improving milk quality. Recent research undertaken at the AgriculturalResearch Institute of Northern Ireland, Hillsborough has shown that it is possible to increase protein content from 3.04 to 3.56% during the winter feeding period. This increase is worth approximately 1.7p per litre. As most purchasers offer greater bonuses for protein relative to fat, increasing milk protein content is one of the few methods of increasing returns from milk sales in a quota situation.

Methods of increasing milk protein

A steady improvement in milk protein can be made by a combination of factors, all contributing to better cow nutrition and management.

Grass/silage

Research from Hillsborough clearly indicates that production of high feed value silage increases milk protein content. Silage digestibility is the most important variable influencing silage feed value, with milk protein content increasing by 0.1% for each additional six units increase in 'D' value. Studies undertaken at Hillsborough have also shown the use of effective inoculants or formic acid, to increase protein on average by 0.1%. Rapid wilting of grass prior to ensiling will increase milk protein content by on average 0.11% but also increases intake by up to 20%.

THE KEY PRINCIPLES ARE:

Planned grazing system

A carefully managed grazing system can improve milk protein through:

Control and utilisation using rotational paddocks and/or strip grazing.
Planned access to fresh and palatable grass.
Assessing grass availability and planning ahead to meet requirements.
Topping when necessary.
Extending the grazing season. Increases in protein content of up to 0.24% have been obtained in studies at Hillsborough.

Alternative forages

There is growing interest in the production of alternative forages, for example, maize, whole crop cereals and kale on dairy farms in Northern Ireland. Research results clearly show that the inclusion of whole crop cereals or kale in the ration of dairy cattle does not improve milk yield or composition relative to good quality grass silage. Inclusion of maize silage in the diet can increase protein content but only if the maize silage has a high dry matter (greater than 25%) and high starch (greater than 20%) contents.

Concentrate feeding

Research has clearly illustrated that feeding concentrates in the form of a complete diet does not alter milk protein content relative to feeding through out-of-parlour feeders, even at feeding levels as high as 14kg concentrates per cow per day.

Other trials show that regardless of silage composition, increases in protein content of up to 0.16% can be obtained by increasing the level of cereals (starch) in the concentrates, without altering silage intake or milk yield.

The key points in concentrate feeding are:

Use concentrates with a high level of starch (greater than 30%) by including cereals.
Avoid oil levels greater than 6.5%.
Use good quality concentrates (greater than 20% protein).
Match concentrate level to silage quality (silage analysis and ration programme).

Conclusions

The most economical methods to increase milk protein are as follows:

High quality silage.
High levels of cereals in the concentrate.
Extended grazing as part of a planned grazing system.

Technical Note prepared by Olwen Gormley, Farm Development Division and Tim Keady, ARINI Hillsborough

ISBN 1 85527 336 5