Webbinarium om förbättrat utnyttjande av vallfodrets näringsinnehåll hos mjölkkor

Ensiling is used widely to conserve forages for feeding to dairy cattle. Silage making methods are better mechanized than those used to make dry hay; this increases the speed of harvest and capture of crop nutrients. Ensiling cool-season grasses also reduces field loss of the nutrients and the chance of weather damage. Grass silage often provides most of the forage fed to dairy cattle and other ruminant livestock in Nordic countries; however, legume silages are potential alternatives that are higher in crude protein (CP). Utilization of CP in both grass and legume silages is inefficient because of extensive CP breakdown to nonprotein nitrogen (NPN) in the silo. Acidification (e.g., with formic acid) improves utilization of silage CP by dairy cows by reducing pH, thereby suppressing NPN formation. Inoculation with lactic acid bacteria (LAB), a method available to organic dairy producers, also increases the rate and extent of pH drop, thus reducing silage NPN. Shorter wilting times, increased harvest speed and other management practices that preserve more plant sugars will speed pH drop because the LAB use these sugars to produce lactic acid in the silage mass. Polyphenol oxidase, an enzyme found in red clover and certain grasses, acts to produce silage with substantially reduced NPN. Similarly, tannin-containing legumes (e.g., birdsfoot trefoil) also yield silages with reduced NPN. Moreover, research conducted in both Sweden and the U.S. indicated that greater rumen-undergraded protein (RUP) in birdsfoot trefoil silage improved CP utilization compared to white clover silage (Sweden) and lucerne silage (U.S.). However, protein breakdown in the silo can never be completely halted. Substantial evidence indicates that even intact silage protein is subject to extensive microbial degradation in the rumen.

Increasing dietary energy stimulates rumen microbial utilization of silage NPN, acting to provide a protein “supplement” to the dairy cow. Organic dairy farmers must provide adequate dietary energy to maximize microbial protein; this requires optimizing rumen fiber digestion in grass and legume silages to allow minimal concentrate feeding. Earlier forage harvest improves fiber digestibility, increasing microbial protein formation. Generally, fiber in legume forages has more rapid rates of digestion, but lower extents of digestion, than fiber in grass forages. The trade-off is greater dry matter intake but lower digestion on legumes, versus greater digestion but lower intake on grasses.

Ration-balancing models, such as NorFor, are valuable tools for assessing whether specific diets meet the dairy cow’s requirements for metabolizable protein--the protein absorbed as total amino acids (the AAT). NorFor can be used to identify situations where dietary supplementation, such as with protein and/or grain energy, will improve RUP supply and, as a result, milk and protein yield. This will increase protein efficiency and reduce nitrogen excretion, thus reducing the environmental impact of dairy production.

Glen Broderick is retired from the USDA-Agricultural Research Service and is an Emeritus Professor in the Department of Animal and Dairy Sciences of the University of Wisconsin.

After receiving his PhD (1972) degree as a joint major in Biochemistry and Dairy Science at the University of Wisconsin-Madison, Glen served as assistant and associate professor of Animal Science at Texas A&M University in College Station from 1972 to 1980. In January 1981, he returned to Madison to work as Research Scientist at the U.S. Dairy Forage Research Center and professor of Dairy Science at the University of Wisconsin.

His research focused mainly on protein nutrition of the lactating dairy cow with emphasis on enhancing utilization of feed nitrogen for milk production. This work has involved developing strategies to minimize dietary crude protein without losing milk or component yield, identifying factors influencing microbial protein formation in the rumen, and perfecting methodology for quantifying ruminal protein escape.

Glen’s research has generated 150 peer-reviewed publications. In addition to teaching and mentoring of graduate students at Wisconsin and other universities, he has served on the editorial boards of several journals and continues to review papers and make occasional invited presentations at national and international meetings.

Glen did sabbaticals at the Rowett Research Institute in Aberdeen, Scotland (1985-6) plus the Swedish Agricultural University in Uppsala (1997-8; 2013). He received an honorary doctorate from the Swedish Agricultural University in 2016.

According to the Web of Science, Glen’s research articles have been cited more than 8,000 times in more than 4,000 articles with an average of about 54 citations per article. In 2019, Glen was named a Fellow of the American Dairy Science Association and, in 2020, joined the “Club 100” with the publication of the 100th of his 102 papers in the Journal of Dairy Science.