July 16, 2007

 

US study shows improved feed cattle rations maintain profit margin

 

 

Many factors can reduce a dairy operation's profit margin such as culling practices, preproduction and milk quality but feed rations can impact dairy efficiency, according to J.W. Schroeder, dairy specialist from North Dakota State University (NDSU).

 

According to Schroeder, dairy efficiency can be defined as pounds of milk produced per pound of dry matter (DM) consumed. He feed efficiency easily comes to the table during times of low milk prices and/or high feed costs and livestock and aquaculture sectors have used feed efficiency (feed-to-gain ratio) as a benchmark for profitability. Monitoring dairy efficiency (DE) 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 research conducted by NDSU is to maximize efficiency as cows consume more feed. Schroeder said digestive efficiency decreases and 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 was proportionally higher.

 

For this reason, maintaining profitability without sacrificing milk production or herd health is to enhance feed efficiency.

 

Schroeder illustrates the following example. Herd A produced 80 pounds of milk, consuming 57 pounds of dry-matter intake (DMI), for a feed efficiency of 1.40. Herd B produced the same amount of milk, but the cows consumed only 50 pounds of DM, for a feed efficiency of 1.60. Assuming feed costs of 7 cents per pound of dry matter, Herd B has a lower feed cost of 49 cents per cow per day, compared with Herd A. In addition, Herd B, with the lower feed intake and higher feed efficiency, will have lower nutrient excretion as manure. This will be important because manure regulations for whole-farm nutrient management are enforced by local, state and national government groups.

 

Schroeder said optimising feed intake is the key not maximising DMI as higher nutrient demand for higher milk production led to maximum DMI to meet higher requirements. The more DM the cow eats, the more she will milk. For Holstein cows, each additional pound of DM consumed could lead to an additional 2 pounds of milk. If 1 pound of DM costs 7 cents, 2 pounds of milk can be worth 30 cents in added income, or 23 cents more income over feed costs. The NDSU research outlines two key points:

• Ration digestibility is constant (but digestibility declines with increased DMI).
   
• All the nutrients consumed are converted to milk production after maintenance needs have been met (not true as growth and/or weight gain occurs).

Composition of the diet (forage-to-grain ratio) and dry-matter intake (multiples of maintenance) have marked effects on digestibility and subsequent energy values. Diets that do not promote optimal rumen fermentation will result in an overestimation of energy values and impair health.

 

Dairy efficiency values in the field can vary from 1.1 to 2. The DSU outlined the following factors that will shift DE values:

• Reducing days in milk can lead to higher DE values because cows direct more nutrients to milk production at the expense of growth and weight gain. Cows losing body condition or body reserves will have high DE values because these nutrients can be captured as higher milk yield.
   
• Age or lactation number (first-lactation cows) can lead to lower DE values because young cows divert nutrients to growth in mid and late lactation. Expect DE values for young cows to be 0.1 to 0.2 unit lower than for mature cows.
   
• Pregnancy requirements reduce DE values as the fetus requirements increase during late gestation (this impact will be small).
   
• Fresh cows (less than 21 days in milk) may have DE values below 1.2 if cows achieve higher DMI (desirable) relative to milk yield. If DE values exceed 1.4, cows could be mobilizing excessive body condition with high milk fat test (undesirable).
   
• Cows gaining body weight will have lower DE values because nutrients are stored as body condition or fat. This decline in DE must occur if cows lose body weight in early lactation. Lower DE values in late lactation can be desirable.
   
• Higher digestible forage will increase DE values because more nutrients are available for productive functions. Neutral detergent fiber (NDF) digestibility tests will be useful benchmarks that will impact DE.
   
• As NDF percent in the ration dry matter increased, DE declined from 1.8 to 1.4, based on Journal of Dairy Science data from 2002 to 2004. DE values remained constant at 35 percent NDF and higher.
   
• Stimulating rumen fermentation while stabilizing the rumen environment will improve nutrient and fiber digestibility. Rumen acidosis will reduce DE values. When US Department of Agriculture calorimetry data with inverted milk fat-to- milk protein tests (one potential sign of rumen acidosis) were removed, the R squared value was 0.55, compared with only 0.14 when all data comparing DE and DM digestibility were included. The higher R squared value explains more variation relating dry-matter digestibility to higher dairy efficiency values.
   
• Excessive heat and cold stress will reduce DE values because more nutrients are needed for maintenance requirements.
   
• Feed additives (such as rumen buffers, ionophores, yeast cultures and fermentation/digestion aids) and silage inoculants can improve DE values by improving digestion and/or nutrient availability. A summary of 12 yeast culture studies reflected a 5 percent improvement in DE (control cows averaged 1.26, compared with yeast culture supplemented cows at 1.32).
   
• Injecting BST (bovine somatotropin) can improve DE values as cows divert more nutrients to milk production.

In the NDSU paper, actual feed intake is critical for an accurate DE value and feed refusals should be lessened because this feed has not been consumed. If a dairy owner targets 4 percent feed refusal with 50 pounds of dry matter offered, Schroeder said the correct value to use in the calculation is 48 pounds instead of 50 pounds. 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.

 

Values are based on 3.5 percent fat correct milk (FCM). Use the following formulas:

• Equation 1: 3.5% FCM = (0.4324 x lbs of milk) + (16.216 x lbs of milk fat)
   
• Equation 2: 3.5% fat and protein corrected milk (lbs) = (12.82 x lbs fat) + (7.13 x lbs protein) + (0.323 x lbs of milk)

Schroeder concludes dairy or feed efficiency reflects the level of fat-corrected milk yield produced per unit of DM consumed, with an optimal range of 1.4 to 1.8 pounds of milk per pound of DM. Days in milk, age, growth, changes in body  condition score, body weight, forage quality, feed additives and environmental factors will impact feed efficiency values.

 

The NDSU advises dairy operators should monitor changes in feed efficiency as feeding and management changes occur on their farms to evaluate the impact of the change. Comparisons among herds must be done carefully.