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Identifying Limiting Nutritional Constraints To Profitability

Michael F. Hutjens

Department of Animal Sciences, University of Illinois,
232 Animal Sciences Lab,
1207 West Gregory Drive,
Urbana, IL, U.S.A. 61801
E-mail: hutjensm@idea.ag.uiuc.edu

Take Home Messages
Dairy managers should partition their feed costs to determine if all areas are price competitive compared to herds in their area at comparable production.
Dry matter intake will be the key management factor to maximizing profitability including the role of forage quality, factors that limits consumption, and dry matter intake management factors.
Purchased feeds should be portioned correctly to maximize profit responses based on milk yield and forage quality.
Service is critical to profitability and must be evaluated.


Profitability can be defined as income minus expenses. Income over feed costs focuses on milk yield (income) and feed costs (expenses). Maximum milk yield is not always most profitable, but nutrient costs for maintenance are the same if cows produce 20 or 40 kg of milk. Generally, higher producing cows will increase profits, but at a diminishing rate. Partitioning feed costs is one approach to evaluate feed component costs (Table 1). Dairy managers should compare their partitioned feed costs to herds in their area and at similar levels of milk production.

Additional feeding comparisons are:

Feed cost per kg of DM------------------------------------ $ 0.13
Feed cost per 100 kg of milk (milk cows only)-------------- $ 9.99
Feed cost per 100 kg of milk (including dry cows)---------- $10.66
Feed cost per 100 kg of milk (including heifers)------------- $12.88

This paper will discuss areas which are important in identifying feeding factors which limit profitability.

Optimizing Dry Matter Intake

Dry matter intake (DMI) is "the key factor" in profitable feeding programs. Energy is the first limiting nutrient in most dairy rations. Two practical approaches to increasing energy intake are available to dairy managers and nutritionists.

Increase DMI through feeding management, blending of ration ingredients (TMR), forage quality, nutrient balance, and optimum ration moisture.
Increase energy concentration per unit of DMI using higher quality forage, feeding more grain, lowering fiber levels, and adding fat or oils to the ration.

Dry matter intake guidelines are outlined below which illustrate factors that impact intake and management.

Most ration formulation programs base DMI on milk yield and body weight (Table 2). Producers and nutritionists must refine and adjust these values based on farm situations.
Dry matter intake is lower in early lactation (Table 3). Transition dry cow rations can improve DMI postpartum by increasing rumen papilla surface area, expanding rumen area, and minimizing metabolic disorders such as acidosis and displaced abomasum.
For each additional kg of ration DMI consumed, milk yield can increase by 2 to 2.5 kg depending on fat test and ration energy concentration.
Peak DMI occurs 4 to 6 weeks after peak milk or 8 to 12 weeks postpartum. Feeding TMR can shorten this lag period and encourage higher DMI.
After injecting BST, DMI lags milk response by three to five weeks causing cows to mobilize body reserves.
Feeding high levels of fat (over five percent total fat) after calving may reduce DMI because of high levels of non-esterified fatty acids (NEFA) mobilized from body fat reserves cause the cow to reduce lipid intake.
Equations to predict kg of DMI are listed below.

Milk cows: (.018 X body weight in kg) + (kg 4% FCM X .305)
Example: (.018 X 600 kg) + (30 kg X .305) = 10.8 + 9.2 = 20 kg

Dry cows (far off): .018 X body weight in kg
Example: .018 X 650 kg = 11.7 kg

Dry cow (close up): Dry cow DMI in kg x .8
Example: 11.7 (above) X .8 = 9.4 kg

Cows consume 1.2% of the body weight as total NDF or 0.9% of body weight as forage NDF. For example, 600 kg cow times .012 total NDF equals 7.2 kg NDF intake (forage and grain). Forage intake for a 600 kg cow would be 5.4 kg (600 kg X .009) based on forage NDF.

Wisconsin researchers have identified three factors that limit feed intake and must be managed to optimize DMI. These are listed in Tables 2 and 3.

Physical Fill Factors Which Limits the Cow From Eating More DM. High levels of fiber, feed with high fill factors, slower rates of digesta flow, and long fiber sources can cause the cow to stop eating. Review ADF, NDF, lignin, and functional NDF values to evaluate if a fill factor limitation exists.

Elevated Blood Metabolites Can "Signal" the Brain Satiety Center to Stop Eating. Chemical signals could include blood ammonia or other nitrogen compounds, circulating fat or non-esterified fatty acids, blood pH, or VFA profiles absorbed from the rumen.

The Environment and Bunk Management Can Cause the Cow to Stop Eating Independently of Ration Characteristics. Examples include empty bunk syndrome, moldy feed, secondary bunk fermentation, poor cow comfort, leg problems that limit cow movement, heat and cold stress, and bunk design.

When rations exceed 50% moisture, DMI can decline. This effect applies to fermented feeds, not pasture or green chop. Cornell workers suggest a decline of .02 percentage units DMI as a percent of body weight per one percentage unit increase in ration moisture. A 635 kg cow fed a ration 10 units wetter may consume 1.3 kg less DMI due to moisture. Israeli researchers in three experiments reported DMI was six to nine percent higher with drier rations (38% DM) compared to wetter rations (53% DM). Adding a dry ingredient such as chopped hay, dry corn, beet pulp, or a buffer can increase DMI. Maryland workers reported adding buffer to corn silage prior to feeding increased silage pH and DMI, with an ideal ration pH of 5.5. Moisture content per se is not the primary factor limiting intake. Fermented products produced during the ensiling process (pH, soluble nitrogen products, or VFA); intracellular water low in pH; or a localized environment low in pH which may cause fiber digesting bacteria not to attach and digest forage fiber have been implicated as causative factors in feed intake depression. Rations can also be too dry which can lower feed intake because feeds are dusty, fines can separate, cows prefer acidic feeds, palatability is reduced, or bunk life is shortened. Optimum ration DM appears to be 55 to 65% DM. Cows appear to be able to eat 50 kg of wet feed a day (at milk yields of 40 kg of milk).

Israeli workers proposed grouping cows receiving TMR based on DMI, days in lactation, and milk yield potential. In the initial 45 days postpartum, cows are challenged to reach true potential by consuming the high group TMR. Mature cows over 38 kg remain in the high group until they dry off or become fat. Mature cows below 38 kg were assigned to a lower quality and cheaper TMR and remain there until they dry off. Cows were not shifted after 45 days because DMI was significantly reduced which reduced milk yield 2 to 4 kg a day. Differences in DMI (4 to 5 kg per cow per day), energy concentration (1.65 versus 1.76 Mcal per kg of DM), and ration costs result in economic responses.

Forage quality has a major impact on milk performance and feed intake. An ideal forage maturity should support maximum intake, optimum nutrient yield per acre, maintain forage crop stand, and minimize losses. Missouri workers illustrate the relationship of forage source and maturity to milk yield (Table 4). Improved palatability stimulates intake. Wisconsin workers proposed that NDF content of forage can be used to predict forage DMI (Table 5). Additional amounts of grain cannot compensate for lower quality forage. Low quality forages result in lower nutrient content per unit of DM, lower digestibility of the DM, and lower DMI.

The following management factors can optimize DMI:

Forage quality that exceeds 1.32 Mcal of NE per kg of DM.
Ration ADF levels of 18 to 20%.
Ration NDF levels of 28 to 33%.
Effective NDF levels of 20 to 22%.
Fermentable carbohydrate levels of 36 to 38%.
Feeding of TMR.
Excellent dry cow rations (far off and close phases).
Ration DM content of 55 to 65%.
True feed weigh backs of 2 to 4%.
MI that meet or exceed NRC guidelines.

Positioning Purchased Feeds

Purchased feed represent significant out of pocket feed costs including protein supplements, minerals, vitamins, fat, by-product feeds, additives, and excellent quality hay. These feeds can add up to for $1.73 per cow per day in Illinois.

Protein supplements = .44
Purchased hay = .30
By-product feeds = .40
Minerals = .11
Vitamins = .03
Fat = .33
Additives = .12

Purchased feeds also include charges for service (forage testing, ration balancing, consulting, and feed quality monitoring). Common questions raised by dairy farmers are:

What should my purchased feed cost be?
When should I purchase feeds?
How can I position purchased feeds?
How much does service cost?

Dairy producers may not purchase enough, excess levels, or the incorrect types of feeds to provide balanced and economical rations. Purchased feeds for lactating dairy cows are affected by two factors: forage quality and level of milk production (Table 6). If forage quality is low, supplemental energy and protein will be needed.

Feed additives can raise feed costs by 2 cents to 60 cents per cow per day. Table 7 lists several feed additives and strategies for use. Dairy farmers and nutritionists must correctly position feed additives to economically justify their use. Benefit to cost ratios can vary from 10:1 (anionic salts) to 8:1 (ionophores and zinc methionine) to 4:1 (buffers and yeast) to 3:1 (niacin). A survey of high producing US herds in 1991 and 1983 illustrate additive use and trends.

Additive inclusion should be based on its role in the ration, economic response, research support; and ability to measure and evaluate on the individual farm.

Service Charges And Strategies
Time has value when farmers receive ration formulating and consulting from a private consultant, feed company, veterinarian, or extension personnel. A value of 10 cents per cow per day was used. This charge results in $3.00 per cow per month or $180 per month (for a 60 cow herd). Several methods can be used to collect this cost.

One-half day of time which results in $45 per hour charge per month.
Add 1 cents per kg to complete grain mix fed per cow per day (10 kg) which raises grain price $10 per ton.
Add 5 cents per kg to protein supplement fed per cow per day (2 kg) which raise the protein supplement price $50 per ton.
Add $0.33 per kg (.3 kg) to mineral/vitamin supplement which raises the mineral mix $330 per ton.

There is no "free" time or service. Mathematics become more interesting if you calculate 150 cow herd size at 10 cents per day. Services include forage testing, computer time, educational meetings, mileage and expenses incurred travelling to the farm, and expected time committed; i.e. one-half day per month, phone calls at night, and response to emergencies. An effective service representative could increase milk yield 2 kg per cow (worth 36 cents per day) and/or lower feed costs 20 cents per day at a cost of 10 cents per day (6 to 1 benefit to cost ratio).


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