Feed efficiency (also referred to as milk performance efficiency and dairy efficiency) can be defined as pounds of 3.5% fat-corrected milk (FCM) produced per pound of dry matter (DM) consumed. The beef, swine, fish, and poultry industries have used feed efficiency (feed-to-gain ratio) as a benchmark for profitability. Monitoring feed efficiency (FE) 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 feed efficiency reflects the idea that as cows consume more feed, digestive efficiency decreases because 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.
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 $3.50 per cow per day for Holstein cows at 70 pounds of milk. A better application of this value is to divide the components to determine if your costs are optimal for your herd's production and local feed costs (Table 1).
|Feed||DMI (lb/day)||Cost ($/lb DM)||Total cost ($/day)|
Feed cost per pounds 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 100 pounds (cwt) or 45 kg 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 cwt 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 herds 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 cwt). 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 cwt 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 Mcal of net energy. If corn is the base energy feed resource, then forages, by-product feeds, and other cereal grains can be compared on their cost per unit of target nutrient.
Feed efficiency 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.
|Group||Days in Milk||FE (lb milk/lb DM)|
|One group, all cows||150 to 225||1.4 to 1.6|
|1st lactation group||< 90||1.5 to 1.7|
|1st lactation group||> 200||1.2 to 1.4|
|2nd + lactation group||< 90||1.6 to 1.8|
|2nd + lactation group||> 200||1.3 to 1.5|
|Fresh cow group||< 21||1.3 to 1.6|
|Problem herds/groups||150 to 200||< 1.3|
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, body weight, 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.
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. An Illinois herd is listed in Table 3.
|Pen||Age (group)||Cow (no)||DMI (lb)||Milk yield (lb FCM)||DIM (days)||FE (lb FCM/lb DM)|
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:
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 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 could 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: Weigh back. Estimations of feed refusals can use a bunk scoring system based on a subjective estimate.
If a bunk reading was bunk score 3 in our example herd, the weigh back 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 and/or walking to pasture resulting in four trips a day averaging 200 meters per trip can increase maintenance requirements by 1.9 Mcal, 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.
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; an animal protein blend increased FE by 0.07 unit compared to soybean meal control source.
Factor 8: Feed additive. Adding yeast culture/yeast, ionophores, buffers, and direct-fed microbial 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.
For dairy managers and nutritionists who 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 cow fresh 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).
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), and/or excess weight losses leading to ketosis and fatty liver development. Table 4 lists dry matter intake guidelines by week after calving and parity.
|Week after calving||1st lactation cows||2nd+ lactation cows|
|----------- lb per cow per day---------------|
With shifting milk prices, one way to maintain profitability without sacrificing milk production or herd health is by enhancing feed efficiency. A herd or group of cows producing 80 pounds of milk consuming 57 pounds of DMI has a feed efficiency of 1.40. Another herd or group produced the same amount of milk, but the cows consume only 50 pounds of dry matter, for a feed efficiency 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 feed efficiency, 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 increase in 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:
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 overestimation of energy values.
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 increase. Values reported in this paper are based on 3.5 percent fat-corrected milk (3.5% FCM). The following formulas can be used:
Equation 1: 3.5% lb FCM = (0.4324 x lb of milk) + (16.216 x lb of milk fat)
Equation 2: 3.5% lb fat and protein-corrected milk (lb) = (12.82 x lb fat) + (7.13 x lb protein) + (0.323 x lb of milk)
On Holstein farms, use the general rule of adding or subtracting one pound of milk for every one-tenth percentage point change above or below 3.5 percent fat test. For example, if a herd averages 70 pounds of milk with a 3.9 percent milk fat test, the estimated pounds of 3.5% FCM would be 74 pounds instead of 70 pounds.
Field Study One. A herd of 1,200 high-producing Holstein cows illustrate herd trends based on parity and days in milk (Table 5).
|Group||DIM (days)||Milk (lb)||DMI (lb)||FE (lb/lb)|
Field Study Two. A herd of 1,800 Holstein cows dropped several feed additives replacing it with a new commercial product. Changes (monitored using Feed Watch and Dairy Comp 305) included an increase in milk yield from 76 pounds to 80 pounds of milk per cow. A drop in dry matter intake from 53 pounds to 51.7 pounds per cow increased feed efficiency from 1.43 to 1.55, and a decline from $5.44 to $4.58 per 100 pounds (45 kg) of milk. Dry matter intake became more consistent along with more uniform manure.
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