Feed efficiency (FE) can be defined as pounds of 3.5 percent FCM (fat-corrected milk) produced per pound of dry matter (DM) consumed.
Beef, swine, fish and poultry industries have used feed efficiency (feed-to-gain ratio) as a benchmark for profitability. Monitoring FE (also referred to as milk performance efficiency and dairy efficiency) in the dairy industry has not been used as a common benchmark for monitoring profitability and evaluating dry matter intake relative to milk yield.
The focus on maximizing FE reflects that as cows consume more feed, digestive efficiency decreases as the relationship between net energy-lactation intake and milk production is subject to diminishing returns. The “traditional focus” was that as cows consume more feed to support higher milk production, the proportion of digested nutrients, captured as milk, is proportionally higher.
Economics of feeding programs
A key measure when evaluating feeding changes is the impact on profitability. Several measurements are listed below for consideration. Each value can have advantages and disadvantages. Feed cost per cow per day does not reflect milk yield, stage of lactation or nutrient requirements. A target value in Illinois is less than $3.50 per cow per day for Holstein cows at 70 pounds of milk. A better application of this value is to divide the components to determine if your costs are optimal for your herd’s production and local feed costs (Table 1*).
Feed cost per pound of dry matter is a useful term when comparing similar regions, breeds and levels of milk production. A target value in Illinois is less than seven cents per pound of dry matter. In the example, in Table 1 for Holstein cows at 70 pounds of milk, the cost is 7.5 cents per pound of dry matter.
Feed cost per hundredweight or 45 kilograms of milk has the advantage of standardizing milk yield, allowing for comparisons between groups and farms within a region. Milk yield per cow and feed costs will impact this value. A target value in Illinois is less than $5.50 per hundredweight for Holstein cows (the example in Table 1* is $5.39).
Income over feed costs (IOFC) is a popular value, as it provides a benchmark for a herd or groups of cows reflecting profitability, current feed prices and actual milk prices. If dairy managers have calculated fixed costs and other variable costs, IOFC can be used to determine break-even prices, optimal dry-off time and culling strategies. A target value in Illinois is over $9.50 per cow per day ($15 per hundredweight). The example in Table 1* is $9.61 per cow per day.
Marginal milk response reflects the profit if additional pounds of milk can be achieved. Generally, this approach is profitable if cows respond to the feeding change because maintenance costs and fixed costs have been covered by previous production. For example, if adding one pound of dry matter increases milk yield by two pounds with milk valued at $15 per hundredweight and dry matter at 7.5 cents, the marginal milk profit is 22.5 cents.
Cost per unit of nutrient allows dairy managers to compare the relative cost of a nutrient. If corn is priced at seven cents per pound (dry matter basis), one unit of net energy is worth $0.065 cents per megacalorie of net energy. If corn is the base energy feed resource, then forages, byproduct feeds and other cereal grains can be compared on their cost per unit of target nutrient.
FE can be defined as pounds of milk produced per pound of dry matter intake (DMI) consumed. Guidelines for FE are listed in Table 2*. In the example in Table 1*, the value was 1.4 pounds of milk per pound of feed dry matter.
Practical approaches to measuring feed efficiency on farms
Option 1: Computer software program.
FeedAd was developed by Zinpro Corporation and is available for field application. The software program allows on-farm data that will standardize FE values (similar to management-level milk or 150-day milk). Using spreadsheets, managers could enter days in milk, bodyweight, milk yield, milk fat test, milk protein test, changes in body condition score, environmental temperature, walking distances and lactation number using research-based and NRC 2001 equations to adjust values.
Option 2: On-farm measurement of FE.
This approach collects dry matter intake by group or herd using actual feed amount delivered with automated computer tracking systems (such as Feed Tracker), subtracting feed refusals, and collecting daily milk yield using a group total (such as in-line milk meters) or individual cow production summaries.
Option 3: Estimating and adjusting for FE.
Many dairy managers and nutritionists are faced with some form of this option due to the following situations or limitations.
– Milk yield is available monthly from DHI or daily bulk tank yields.
– Feed intake by groups or herd is not recorded daily. A feed sheet or ration may be available.
– Weighbacks may or may not be measured.
– No group or pen milk components are available.
Using this approach to estimate FE, the following factors can be used along with bulk tank milk yields and ration summaries. For example, the herd of 100 cows averaged 6,800 pounds of milk and consumed 4,800 pounds of dry matter a day based on feed ration sheets. The FE is 1.42 for this herd (a low value that requires review of potential factors that may be causing this to occur).
The following factors can be used with estimated impact values on FE. Nutritionists and dairy managers can adjust these values as data are not available for several of these factors (modify as desired).
Factor 1: Weighback
Estimations of feed refusals can use a bunk scoring system based on a subjective estimate.
– Feedbunk score 1 has no feed remaining
– Feedbunk score 2 has 2 to 4 percent remaining
– Feedbunk score 3 may have over 5 percent remaining
If a bunk reading was bunk score 3 in our example herd, the weighback could represent 2.4 pounds. Adjusting for this amount of feed not consumed, the adjusted FE could be 1.49.
Factor 2: Days in milk (DIM)
Add 0.15 FE unit for each 50 days starting at 150 DIM. In our example herd, if days in milk were 200 days, add 0.15 unit or adjusted FE of 1.57.
Factor 3: Somatic cell count
For each linear score decrease in SCC, add 2.5 pounds more milk to the current production. If our example herd was linear score 4, reducing linear SCC to 3 could add 2.5 pounds to 68 or 70.5 pounds, leading to an adjusted FE of 1.47.
Factor 4: Change in body condition
If cows are gaining one-half body condition score, this milk equivalent can represent 138 pounds of milk (60 pounds of body condition equals 2.3 pounds of milk per pound). If this occurs over 100 days, adding 1.4 pounds of milk to the base results in an adjusted FE of 1.45.
Factor 5: Exercise/pasture
If cows walk 800 meters per day (two times a day milking or walking to pasture resulting in four trips a day averaging 200 meters per trip can increase maintenance requirements by 1.9 megacalories, which is equal to 5 pounds of 3.5 lb FCM). Adding this amount to the example herd could raise FE to 1.52 units.
Factor 6: Rumen acidosis
Field reports estimate that FE may drop 0.1 unit if cows experience subacute rumen acidosis (SARA). Diagnosis could be based on several field indicators:
– Milk protein: milk fat ratios over 0.9 (3.0 true milk protein test and 3.3 milk fat test)
– Loose manure (average manure scores under 2.75)
– Average lameness scores over 1.6
– Dry matter intake varies over 2 pounds per cow per day using TMR values
Factor 7: Protein level and form
Illinois data indicated that the level of protein can impact FE, as diets from 16.8 to 18.7 decreased FE by 0.03 unit, while an animal protein blend increased FE by 0.07 units compared to soybean meal control source.
Factor 8: Feed additive
Adding yeast culture/yeast, ionophores, buffers and direct-fed microbials may increase FE by 0.05 to 0.10 unit.
Factor 9: Fiber level
As NDF (neutral detergent fiber) percent in the ration dry matter increased, FE declined from 1.8 to 1.4 based on Journal of Dairy Science data from 2002 to 2004. FE values remained constant at 35 percent NDF and above.
Factor 10: Heat stress
If cows are exposed to heat stress with no heat abatement intervention, the following declines in FE can occur due to higher maintenance requirements, lower milk yield and lower feed intake. Cows exposed to 86ºF compared to 68ºF, reduce FE by 0.1 unit. Cows exposed to 95ºF compared to 86ºF, lower FE by 0.3 units.
Fresh cow monitoring of FE
For dairy managers and nutritionists that have a fresh cow pen with daily milk yields, group feed intakes and days in milk recalculated daily, FE is a useful tool to monitor dry matter intake after calving, comparison of heifer and mature, fresh cow pens and the success of the transition program. A California field study of 50 herds reported the FE for the following groups of cows (days in milk was not reported).
• Heifer fresh cow group averaged 1.47 with a range of 1.19 to 1.87
• Fresh cow pen averaged 1.75 with a range of 1.26 to 2.26 A low FE can be a plus if dry matter intake after calving is optimal.
A low FE after calving can reflect low milk production in early lactation, a potential problem. A high FE can indicate cows are achieving high milk after calving (good), low dry matter intake after calving (bad) or excess weight losses leading to ketosis and fatty liver development.
Economics of feed efficiency
With shifting milk prices, one way to maintain profitability without sacrificing milk production or herd health is by enhancing FE. A herd or group of cows producing 80 pounds of milk consuming 57 pounds of DMI has an FE of 1.40. Another herd or group produced the same amount of milk, but the cows consumed only 50 pounds of dry matter, for an FE of 1.60.
Assuming feed costs of $0.07 per pound of dry matter, the second herd has a lower feed cost of $0.49 per cow per day compared to the first herd. In addition, with the lower feed intake and higher FE, cows will have lower nutrients in fecal material. As a guideline, for each improvement of 0.1 unit in FE (from 1.4 to 1.5, for example), the increased income can vary from 15 to 22 cents per cow per day.
Optimizing feed intake is the “new approach,” not maximizing DMI. Higher nutrient demand for higher milk production leading to maximum DMI must be achieved to meet these requirements. The more DMI the cow eats, the more she will milk. For Holstein cows, each additional pound of DMI consumed could lead to an additional two pounds of milk. If one pound of dry matter costs seven cents, two pounds of milk can be worth 30 to 36 cents more income, or 23 to 29 cents more income over feed costs.
This guideline assumes two points:
• Ration digestibility is constant (digestibility declines with increased DMI).
• All the nutrients consumed are converted to milk production after maintenance needs have been met (no growth or weight gain, for example).
Composition of the diet (forage- to-grain ratio) and dry matter intake (multiples of maintenance) have effects on digestibility and subsequent energy values. Diets that do not promote optimal rumen fermentation will result in an over-estimation of energy values.
Fine-tuning feed efficiency
Actual and accurate feed intake is critical for an accurate FE value. Feed refusals should be removed (subtracted), as this feed has not been consumed. Weekly dry matter tests should be conducted on the farm to correct for variation in dry matter intake due to changes in wet feeds or precipitation. Correct for milk components as more nutrients are needed as milk fat and protein content increases.
Values reported in this paper are based on 3.5 percent fat-corrected milk (3.5 percent FCM). The following formulas can be used:
Equation 1: pounds of 3.5 percent FCM = (0.4324 x pounds of milk) + (16.216 x pounds of milk fat)
Equation 2: pounds of 3.5 percent fat- and protein-corrected milk = (12.82 x pounds of fat) + (7.13 x pounds protein) + (0.323 x pounds of milk)
On Holstein farms, use the thumb rule of adding or subtracting one pound of milk for every one 0.1 percentage point change above or below 3.5 percent fat test. For example, if a herd averages 70 pounds of milk with 3.9 percent milk fat, the estimated pounds of 3.5 percent FCM would be 74 pounds instead of 70 pounds.
Summary
• FE reflects the level of fat-corrected milk yield produced per unit of dry matter consumed, with an optimal range of 1.4 to 1.9 pounds of milk per pound of dry matter.
• Days in milk, age, growth, changes in body condition score, walking distances, bodyweight, forage quality, feed additives and environmental factors will impact FE values.
• Dairy managers should monitor changes in FE as feeding and management changes occur on their farms to evaluate the impact of the change.
• Several approaches can be used in the field to measure or estimate FE in groups, herds and feeding or management changes. PD
References omitted but are available upon request at editor@progressivedairy.com
Tables omitted but are available upon request to editor@progressivedairy.com.
—Excerpts from 2007 Penn State Dairy Cattle Nutrition Workshop Proceedings
Michael F. Hutjens
Professor of Animal Sciences
University of Illinois
