September 5, 2017 at 3:32 p.m.
Highlights from the Minnesota Nutrition Conference
This year, as always, interesting dairy topics were presented. Topics covered included calf nutrition, feeds for lactating cows and environmental nutrition issues in managing the dairy farm feeding program. Below is a brief summary with take home messages from the four dairy presentations at the conference.
"Calf Nutrition and Milk Replacers" - Dr. Al Kertz, Milk Specialties
Dr. Kertz reviewed the development and evolution of milk replacers and baby calf feeding programs over the last 50 years. Milk replacer feeding programs have come from a basic 20 percent protein-20 percent fat at about one pound of powder per day to the accelerated programs with high protein (28 percent) and moderate fat (15 percent) fed up to two pounds of powder per day. Early weaning programs with conventional milk replacers emphasized calf starter intake to limit feed costs and promote rumen development. The newer accelerated programs place more emphasis on optimum growth the first few months of life and developing the calf for future milk production. The take home messages from Dr. Kertz were:
• A calf should double its body weight from birth to 2 months of age.
• The ideal milk replacer today has around 26 percent protein and 18 percent fat.
• 15 percent solids is the practical upper limit on milk replacer concentration for feeding.
• A 100 pound calf will need 1.75 Mcal of metabolizable energy (ME) per day which equates to 5.5 pounds or about 2.5 quarts of whole milk per day for maintenance with no cold stress. Milk replacers are lower in fat (energy) than whole milk so about 0.85 pound of milk replacer powder is needed per day just for maintenance.
• There is 1,990-pound gain in milk production over three lactations for every Mcal of ME a calf is fed above maintenance during the pre-weaning period.
"Optimum Feeding of Low Starch Diets" - Dr. Jeff Firkins - Ohio State University
Dr. Firkins discussed some nutritional considerations and diet formulation guidelines to optimize milk production with low starch diets (less than 25 percent starch). High fiber byproduct feeds have been increasing in dairy cattle diets as corn prices have increased. Replacing some corn starch in diets with digestible fiber can support good milk production and help control feed costs if some basic nutrition needs of the rumen microbial population are met. Some of his suggestions included:
• Diets should be higher than 20 percent starch to support good microbial growth.
• The fiber in high fiber byproduct feeds can restrict feed intake (fill effect) the same as high forage fiber diets.
• Diets high in fiber byproduct feeds may have adequate fiber in the ration, but they may not support a good rumen fiber mat for digestion. Therefore, forages fed in a high byproduct fiber diet need to have adequate particle size for good rumen mat formation.
• Sugar byproduct feeds can be fed at two to five percent of the diet dry matter and can support the digestion of fiber in the rumen.
• Sugars digest to butyric acid and valeric acid in the rumen and aid absorption of all volatile fatty acids from the rumen which helps reduce the potential of acidosis.
• Rumen degradable protein (RDP) is needed to optimize rumen digestion of fiber and sugar feeds. An RDP of 11 percent of the dry matter or about 65 percent of the total protein should be maintained for good rumen feed digestion.
"Using Corn Distillers Grains in Dairy Rations" - Dr. Dave Beede, Michigan State University
There is a lot of confusion and differences of opinion on how much and in what types of diets DDGS should be fed. The analysis of research studies on distillers grains (DDGS) in lactating dairy cow diets by Dr. Beede and co-workers at Michigan State provided the following guidelines to optimize milk production from DDGS.
• Diet fermentability and quality of protein in the diet markedly influenced milk production response when DDGS replaced other protein and energy sources in diets.
• Milk production responses to inclusion of DDGS in diets peaked at about 2.5 pounds per cow. Diets with 24 percent corn silage and 23 percent starch (dry matter basis) yielded the greatest response in milk production with DDGS feeding while higher corn silage (47 percent) and starch diets (32 percent) resulted in reductions in milk production with DDGS feeding. The low corn silage (24 percent) and starch (23 percent) diet would be considered a moderate fermentability diet whereas the higher corn silage and starch diet is considered a highly fermentable diet.
• Protein from corn sources should be less than 8.5 percent of the total crude protein in diets. Protein from non-corn sources should be more than 6.5 percent of the total crude protein when DDGS is fed for optimal milk production. A balance of protein and amino acid sources is needed to optimize milk production as corn protein is limiting in lysine and some other amino acids.
• Milk fat percent was not decreased in cows with a 3.6 percent milk fat or lower when DDGS was included in the diet, but for cows above 3.6 percent milk fat, a negative milk fat response was observed.
"Phosphorus and Potassium in Dairy Nutrition" - Tamilee Nennich, Purdue University
The focus of dairy nutrition needs to go beyond providing animals with nutrient balanced, nutritious diets. Dairy nutritionists today must be concerned with getting the highest digestibility and absorption of feed nutrients and not over feeding nutrients. Feeding nutrients in excess of animal requirements can have detrimental effects on the environment. Some concerns about phosphorus (P) and potassium (K) in dairy cattle diets are:
• Intake of P is directly related to P excretion and the amount of P that needs to be handled in the manure.
• Recent research shows cows may respond in milk production to diets as high as 0.42 percent P (dry matter basis), but there is no data to support feeding diets above this for better reproductive performance or milk production.
• Byproduct feeds are high in P and inclusion of them in diets often results in diets much greater in P content than needed to meet requirements.
• High dietary P levels cannot be ignored as it has a direct cost in manure handling and application.
• Potassium is the mineral needed in the largest amount by lactating cows.
• Grass forages are luxury consumers of K and high manure or commercial fertilizer applications to these forages can substantially increase their K content. Some forages raised on heavily manured ground has been found to contain more than four percent K.
• The role and balance of all nutrients in the dairy feeding program needs to be considered today. Excreted nutrients must be handled in a responsible manner to prevent negative impacts on the environment.
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