Brian Sloan Ph.D.
October 25th 2002

Index:
Introduction
Why the reluctance to formulate on an individual metabolizable AA basis?
Increasing MP (RUP) supply gives a predictable improvement in milk yield – HELLO !!!
Failing to respect minimum LYS and MET concentrations in MP has a negative effect on milk yield
Factors of variation in predicting amino acid supplies…
Advantages to formulating on an individual amino acid basis…
Milk performance when increasing MET, LYS and/or both (% of MP) after calving
Milk performance when increasing MET, LYS and/or both (% of MP) were fed prior to calving
Using the appropriate AA formulation constraints will give consistent performance benefits
Whereas using inappropriate AA formulation constraints will give inconsistent performance benefits…
Effect of LYS (% of MP) on efficiency of MP utilization for milk protein production
Balancing rations for LYS and MET improves the efficiency of utilization of MP
How should we approach ration formulation for amino acids?
Practical Formulation Levels of LYS and MET as a % of MP – NRC 2001
Practical Formulation Levels of LYS and MET as a % of MP – CPM Version 1
Methionine for the Rumen ??
Influence of HMB in a dairy rationon milk fat % and yield of milk fat.
The influence of HMB was evaluated using the in vitro continuous culture technique
Composition of Rations...
RESULTS - Effect of Level of HMB (% of DM) on Digestibilities
RESULTS - Effect of Level of HMB (% of DM) on Nitrogen Partition
RESULTS - Effects of Level of HMB (% of DM) onMicrobial Efficiency
HMB does effectively modify aspects of ‘rumen’ digestion and metabolism
Effect of level of HMB (% of DM) on milk performance…
Practical Recommendations for the use of HMB
Formulation constraints to take advantage of HMB enhancing microbial protein synthesis and balancing for met. LYS and MET…
“Conventional Ration” – 100lb ration in CPM Dairy
“Reformulated Ration” – 100lb ration in CPM Dairy
Ingredient Composition of Diets
Chemical Composition and NRC (2001) Evaluation of Diets
Benefits of reducing ration protein levels, balancing for LYS and MET and including a ruminal source of methionine.
Maximize rumen N-utilization, drastically decrease N excretion and still optimize milk performance.
The ration balanced for amino acids at both the rumen and metabolic level was themost cost effective
Ingredient composition of “Conventional” and “New” UNH diets (% of DM)
Chemical composition and 2001 NRC evaluation of “Conventional” and “New” UNH diets (% of DM)
A Case Study - Applying the Principles of Balancing for LYS and MET and Including a Ruminal Source of HMB.
Goodbye Protein – Hello Amino Acids :Are you prepared to go the next step ?

Introduction

With the data now available, it is reasonable to say that, as a market, this is the way we now have to formulate diets to achieve the best possible returns for our milk producer customers.

We have already the basic formulation tools and practical recommendations available to evolve from purely a metabolizable protein ( MP) based system to one that also incorporates formulation constraints for at least the first two limiting amino acids – lysine (LYS) and methionine (MET).

Risks are minimal to evolving diet formulation in the direction of metabolizable amino acids compared to the potential benefits.

Why the reluctance to formulate on an individual metabolizable AA basis?

• No additional or large enough performance advantage…
  Marginal responses in the published trials to date so that it is not worth the extra formulation challenge
  
  
• Inconsistent responses…
  Yes, amino acid nutrition is important but our knowledge base is such that when we try to apply amino acid formulation in the field we get inconsistent responses therefore we have to wait for more data
  
  
• Costly – milk payment schemes, ration cost…
  There is a perception that amino acid balancing means a large increase in ration cost. It is sometimes perceived to cost 20-30 cents per-cow-per-day. However, this would be an exception as we can balance rations for AAs at little or no increase in ration cost.
  In most federal orders, milk is now remunerated for protein - this becomes a major economic incentive. These economic benefits are improved compared to four or five years ago.
  
  
• Introduces more variation than simply sticking with the “tried and trusted” MP approach…
  Many nutritionists feel today’s MP systems perform adequately. They also feel evolving MP systems to consider individual amino acids (rather than simply total amino acids) will introduce greater variation into the rationing approach, rather than reduce it.
  

It is estimated that currently only 1% of the cows in the U.S. receive rations where there has been a serious attempt to balance rations for LYS and MET.

Increasing MP (RUP) supply gives a predictable improvement in milk yield – HELLO !!!

So, how well do MP systems work? Irrespective of what MP system is used, intrinsic to each system is the necessity for rations to supply appropriate quantities of rumen undegradable protein in order to augment microbial protein supply. This ensures that the cow’s total amino acid requirements for optimal milk performance will be met.

If we apply the ‘addition of undegradable’ principle correctly, we would expect to find consistent benefits to substituting less rumen- degradable protein sources for more degradable protein sources as long as we continue to meet microbial nitrogen (N) requirements.

However, numerous data does not seem to confirm this principle.

In the excellent review of Santos et al which covered over 88 scientific articles two things are clear –

• Overall milk yield responses were marginal compared to model predictions - >2kg of milk per day would be expected to the estimated increase of at least 100g of RUP when the high RUP supplements were supplemented for soybean meal.
• The use of certain raw materials gave either no response or had a negative impact compared to feeding soybean meal.

The variation in response would seem to be related to the amino acid profile of the raw materials!

Failing to respect minimum LYS and MET concentrations in MP has a negative effect on milk yield

Hidden away on page 316 in the 2001 NRC publication is perhaps one of the most pertinent observations validating the importance of metabolizable LYS and MET content as a percent of MP.

NRC 2001 Page 316 – Weiss and Schwab personal comm.

In the validation dataset, Dr. Bill Weiss determined that when actual milk yield was lower than predicted, this was related to lower levels of metabolizable LYS and MET (% of MP) in the ration.

A level of 6.2% LYS would not be atypical of conventionally fed rations.

Failing to feed adequate levels of MET and LYS is going to reduce production. This begs the question – “Are we currently overfeeding protein in our diets just to compensate for the inefficient use of dietary protein (when rations are not balanced for LYS and MET?)”.

Factors of variation in predicting amino acid supplies…

What is really different between an older MP system and newer ones evolved to take into consideration individual amino acids?

Really, all the principal sources of variation are the same for the two systems except for the amino acid profile of DRUP. The question is,
“What introduces more variation - making an estimate of the amino profile or completely ignoring the amino acid profile?”.

Obviously, ignoring the amino acid profile leads to more variation in predicting milk performance.

Advantages to formulating on an individual amino acid basis…

Five good reasons:

1. Increase milk protein percent
2. Maximize milk production
3. Improve N efficiency, reduce N excretion
4. Reduce metabolic problems
5. Improve energy utilization - favors reproduction

Milk performance when increasing MET, LYS and/or both (% of MP) after calving

Milk yield and protein % are generally both improved in early lactation when rations are balanced for LYS and MET at freshening/or within the first few weeks after calving.

+ 0.7 kg/d milk + 0.16% units milk protein + 79 g/d milk protein + 0.02% units in milk fat + 48 g/d milk fat

Summary of Seven Trials - Garthwaite et al. (1998)

Milk performance when increasing MET, LYS and/or both (% of MP) were fed prior to calving

The improvements in milk yield can be enhanced if rations are also properly balanced for LYS and MET not only in early lactation but also in the pre-fresh ration.

+ 2.3 kg/d milk + 0.09% units milk protein + 112 g/d milk protein + 0.10% units in milk fat + 116 g/d milk fat

Summary of Five Trials - Garthwaite et al. (1998)

Using the appropriate AA formulation constraints will give consistent performance benefits

The previous data certainly shows the potential benefit. The question now is – “How consistently can we predict the response?”.

In order to validate these proposed formulation nutrient levels, the trial results from the summary of Garthwaite et al were re-scrutinized. Only trials or treatments within a trial were selected, which matched optimum LYS and MET levels and ratios.

There were seven trial/treatments in total and responses were calculated relative to their respective Controls. The Control rations had variable LYS and MET levels.

*Trials selected where treatments achieved LYS (6.83 to 7.09) and MET (2.13 to 2.30) constraints and where a LYS/MET ratio of 3.1 to 1 (2.97 to 3.32) was respected – CPM Version 1.

On average the compilation showed consistent increases in both milk protein and milk fat yield and justify the application of the LYS and MET levels proposed to optimize milk performance.

Whereas using inappropriate AA formulation constraints will give inconsistent performance benefits…

Using the same dataset from Garthwaite et al we also identified the trials where in the reformulated diets, though MET and/or LYS were increased, the LYS:MET ratio failed to meet a minimum of 3.0 : 1.

* Trials extracted from Garthwaite et al. 1998 dataset where Treatment LYS and/or MET (% of MP) were improved over Control but LYS:MET Treatment ratios failed to exceed 3.0:1

Compared to the previous trials a consistent response was less evident.

This appears to reinforce the practical significance of the 3.1:1 LYS:MET ratio.

Effect of LYS (% of MP) on efficiency of MP utilization for milk protein production

Let’s now consider how amino acid balancing will help use dietary protein more efficiently.

Large improvements in efficiency of MP utilization will occur when balancing the LYS and MET in MP.

In the above trial Smartamine M was included across all diets to maintain a constant metabolizable MET level (2.4 % MET of MP).

Going from a low LYS level of 5.1 to 6.5% of MP (NRC) increased linearly the efficiency of use of MP for milk protein production from 0.57 to 0.66.

Balancing rations for LYS and MET improves the efficiency of utilization of MP

The average Control diet is more representative of the levels of LYS and MET found in conventional rations.

When improving these levels the corresponding milk production increases are observed. Overall there was a 4% point improvement in efficiency of utilization of MP for milk protein synthesis (0.62 to 0.66).

The 0.66 is close to the efficiency factors used in NRC 2001 (0.67) and CPM (0.65)

How should we approach ration formulation for amino acids?

1. Formulate for a minimum MP requirement
2. Optimize LYS as a % of MP.
3. Optimize the ratio of LYS : MET

Rationing on a ratio (ideal protein) is equally as important as rationing grams per head per day.

Amino acid balance integrates both concepts and will work only if total amino acid (TAA) requirements are met first, before optimizing the profile (ideal protein) of amino acids.

Practical Formulation Levels of LYS and MET as a % of MP – NRC 2001

Although the new NRC proposes optimum ration metabolizable LYS and MET levels of 7.2 and 2.4 % of MP respectively, these levels cannot be attained through practical formulation.

Practical LYS and MET levels to target, are 6.66 and 2.22 (% of MP), and a ratio of 3.0 to 1. These are still high enough to express the majority of the potential increase in milk components.

Practical Formulation Levels of LYS and MET as a % of MP – CPM Version 1

The optimum and practical LYS and MET recommendations in the CPM model are numerically different from NRC.

CPM relies on the recommendations imported for the French PDI system. This simple transfer of requirements cannot be totally justified.

Sloan et al 2000 showed that estimates of metabolizable LYS and MET supplies are different between the CPM and PDI systems. Adjusting for these differences indicates that practical formulation levels for LYS and MET in CPM are 6.82 and 2.19 % of MP with the optimum ratio being 3.12 : 1.

Methionine for the Rumen ??

Up until now we have only considered the cow and her metabolic needs for amino acids. Perhaps the rumen microbial population has amino acid requirements also. If they do and we can enhance microbial protein synthesis we will help the cow by supplying more total amino acids of a better amino acid profile reducing the quantities of RUP sources that need to be supplied.

Influence of HMB in a dairy rationon milk fat % and yield of milk fat.

The benefits of using the methionine hydroxy analogue now more commonly referred to as HMB has been tested for its influence on milk performance since the early 70s - first in its calcium salt form and then as the pure acid form.

Responses have been mixed. Milk yield was increased in a few studies, milk fat % was increased in approximately 50 % of the cases.

When it did have a positive effect, the results could be quite dramatic as shown by the results of Rode et al 1997.

Rode et al 1997

The literature would suggest that the primary mode of action must be in the rumen.

The influence of HMB was evaluated using the in vitro continuous culture technique

Potential effects of HMB in a dynamic environment which mimicks the in vivo situation was examined employing the continuous culture methodology of Hoover et al.

Experimental Design

• 2 X 3 Factorial
  • two grain types (‘CORN’ vs ‘BARLEY’),
  • three levels of HMB (0 vs 0.11 vs 0.22%)
• 4 replicates per treatment

The rations (Treatments) were fermented in continuous cultures
operated with :

• a 12% liquid dilution rate and
• a 4.2 %/h solids dilution rate
  

Composition of Rations...

Forage proportions were similar between treatments. The main difference was the grain portion of the ration. However there were also some differences in the protein sources in the ration to try and achieve two rations that were balanced for crude protein and the proportion of rumen degradable protein.

The corn ration was complemented by soy based protein sources, whereas a significant portion of the barley ration protein was also from cottonseed and bloodmeal.

These rations were formulated to support 45 kgs of milk production in early lactation.

RESULTS
Effect of Level of HMB (% of DM) on Digestibilities

Responses to HMB were similar for both cereal sources, therefore the data was regrouped to look at the main effects of HMB.

The effects of HMB were quadratic in nature. The intermediate dose in general improved digestibility.

DM digestibility was improved which was almost entirely explained by the improvement in CP digestibility.

There were no significant effects on fibre dig.

RESULTS
Effect of Level of HMB (% of DM) on Nitrogen Partition

¹Non-ammonia N
²Microbial N
³Non-ammonia, non-microbial N (bypass feed N)

HMB had some profound effects on N partition.

Ammonia levels were reduced with the intermediate dose of HMB

Total flow of N was increased.

Most significantly was the effect on microbial N flows - approximately a 30% increase.

DAPA was the marker used to determine the microbial N contribution.

RESULTS
Effects of Level of HMB (% of DM) onMicrobial Efficiency

MN/Dig. N * 100

The middle level of HMB not only improved the efficiency of utilization of energy for microbial protein synthesis but also the efficiency of use of the available N.

HMB does effectively modify aspects of ‘rumen’ digestion and metabolism

N - Fraction

• fermenter ammonia’s decreased by 20%
• microbial activity and protein synthesis stimulated by 25 %
• efficiency of microbial protein synthesis enhanced by 20 %
• N utilization in the rumen is increased
• effects are independent of energy source

Lipid Fraction

• flows of lipid can be enhanced
• the profile of FA’s can be modified
• % of saturated FA’s tend to increase relative to unsaturated FA’s

Effect of level of HMB (% of DM) on milk performance…

In a recent experiment carried out at Cornell, the effect of two doses of HMB were evaluated on milk performance and liver metabolic parameters.

Overton - South West Nutrition Conference 2002

The levels used, although formulated on the basis of assuming a 40% bio-availability value for Alimet, were very similar to the doses used in the previously described fermenter study.

No effect was observed on liver metabolic parameters questioning whether there was any real effective delivery of HMB systemically.

Nevertheless there was a quadratic response in terms of milk yield, with the first dose eliciting a 6.5 lb increase in milk but with no accompanying effect on milk protein %, again indicating this response to be of ruminal origin.

Practical Recommendations for the use of HMB

0.11% of Dry Matter Intake

Working on the principle that the inclusion of HMB will increase the efficiency of microbial protein synthesis by 10 %, MP from RUP can be correspondingly reduced and total MP supply still maintained. In the CPM or NRC models this improvement in microbial efficiency can be taken into account indirectly by lowering MP requirements by 4 to 5 % points :

ie from 100 to 96.

Formulation constraints to take advantage of HMB enhancing microbial protein synthesis and balancing for met. LYS and MET…

When putting together the benefits of both balancing LYS and MET at the metabolic level and the provision of a ‘methionine’ source at the level of the rumen, MP requirements can be reduced to 92 % of the conventional MP requirements in CNCPS/CPM or NRC.

The objective is to be able to use dietary crude protein more effectively and still keep the advantages in terms of improved milk components

“Conventional Ration” – 100lb ration in CPM Dairy

“Reformulated Ration” – 100lb ration in CPM Dairy

In this case the reformulation of the previous ration gives a solution which lowers crude protein in the ration by a full % point and MP balance to -184 g. This is approximately 94 % of MP requirements. The other formulation constraints in the ration in this example prevent taking full advantage in N economy and finding a solution at 92% of MP.

The cost of the ration is only increased by 4 cents and we have optimized the ration in terms of metabolizable LYS and MET.

Ingredient Composition of Diets

This previous type of calculation looks very pretty on paper but does It
work in practice. Can we really reduce ration crude protein levels through
reducing MP requirements and at least hold milk production and still
improve milk composition when we adjust rations on an amino acid
balance basis.

A recently competed trial at OSU indicates that this is indeed possible.

Noftsger and St-Pierre (2001)

The objectives were first to compare the incorporation of a selected
animal protein blend high in intestinal digestibility (Trt 2) in place of an
unselected meat meal (Trt 2) at a conventional dietary crude protein level (18.3%)
Secondly the objective was to lower also the CP in the ration while
incorporating this selected blend (Trt 3). Lastly, was to observe the effects
of balancing rations for metabolizable LYS and MET (Smartamine M included)
at a lower dietary crude protein level while also incorporating Rhodimet AT 88
as a ruminal source of methionine (Trt 4).

Chemical Composition and NRC (2001) Evaluation of Diets

Noftsger and St-Pierre (2001)

There were 15 cows per treatment (approximately 50% in first lactation). Treatments were started in the 4th week of lactation and continued for 15 weeks.

The retrospective measurements and estimates showed that TRTs 2, 3 and 4 had improved metabolizable LYS contributions compared to the Control (1). Only treatment 4 had an enriched level of metabolizable MET and a LYS to MET ratio close to recommendations.

Benefits of reducing ration protein levels, balancing for LYS and MET and including a ruminal source of methionine.

Noftsger and St-Pierre (2001)

The Control had a lower intake than the other 3 treatments and this probably partly contributed to the lower observed milk yields.

Nevertheless the substitution of the more highly digestible animal protein blend increased milk yield by nearly 6kgs per day. However reducing dietary CP at the same time lost part of this response (TRT 3). But balancing for LYS and MET at the lower dietary CP level while including HMB ensured optimum production with the best milk components – both fat and protein.

The retrospective calculation of MP allowable milk for each treatment again shows clearly the superior efficiency of dietary protein utilization on Trt 4. NRC would only predict sufficient MP in the diet to support a daily yield of 39.5 kg (87lbs) whereas the cows on this treatment achieved 46.6 kg (102.5 lbs).

Maximize rumen N-utilization, drastically decrease N excretion and still optimize milk performance.

Trt 4 shows the dramatic effect that correctly balancing rations for LYS and MET can have on N-excretion. This means that there is less of a requirement on the animal’s metabolism to eliminate surplus amino acids through urea and thus energy is spared for more productive purposes. BUN’s and MUN,s were reduced which will be favorable for rebreeding. Feeding rations balanced for LYS and MET will help respect environmental concerns and legislation designed to balance farm N inputs and outputs.

Cows on treatment 4 excreted 1.47 g N per g of N in milk

VS

2.38g N per g of milk N for cows on treatment 1

A 35% improvement in N efficiency

The ration balanced for amino acids at boththe rumen and metabolic level was themost cost effective

One of the most pertinent economic comparison to make in this trial is Trt 2 vs Trt 4. There was only a marginal increase in feed costs of 6 cents per cow per day. In return due to the improved milk components milk income was increased by 42 cents a net benefit of 36 cents per cow per day.

Trts 1 and 3 show what can happen if you do not respect some of the basic principles of amino acid formulation – milk performance is compromised and profitability hurt.

Ingredient composition of “Conventional” and “New” UNH diets (% of DM)

A field trial was conducted at the University of New Hampshire. After the publication of the New NRC, the rations at UNH were reformulated to be balanced for metabolizable LYS and MET.

The changes in formulation constraints resulted in a selected blood meal based animal protein blend (ProvAAl Elite) being incorporated at the expense of the protected soybean meal.

Smartamine M inclusion ensured a LYS:MET ratio of 3.0 : 1. Rhodimet AT88 was also included to maximize rumen digestive processes.

Chemical composition and 2001 NRC evaluation of “Conventional” and “New” UNH diets (% of DM)

Rations -The conventional ration had been fed from May 2000 to the University of New Hampshire Experimental herd. The ration was reformulated in February 2001 according to the new NRC recommendations.