Milk production and efficiency of utilization of nitrogen, metabolizable protein, and amino acids are affected by protein and energy supplies in dairy cows fed alfalfa-based diets
Open Access
- 1 January 2022
- journal article
- research article
- Published by American Dairy Science Association in Journal of Dairy Science
- Vol. 105 (1), 329-346
- https://doi.org/10.3168/jds.2021-20923
Abstract
Alfalfa has a lower fiber digestibility and a greater concentration of degradable protein than grasses. Dairy cows could benefit from an increased digestibility of alfalfa fibers, or from a better match between nitrogen and energy supplies in the rumen. Alfalfa cultivars with improved fiber digestibility represent an opportunity to increase milk production, but no independent studies have tested these cultivars under the agroclimatic conditions of Canada. Moreover, decreasing metabolizable protein (MP) supply could increase N use efficiency while decreasing environmental impact, but it is often associated with a decrease in milk protein yield, possibly caused by a reduced supply of essential AA. This study evaluated the performance of dairy cows fed diets based on a regular or a reduced-lignin alfalfa cultivar and measured the effect of energy levels at low MP supply when digestible His (dHis), Lys (dLys), and Met (dMet) requirements were met. Eight Holstein cows were used in a double 4 x 4 Latin square design, each square representing an alfalfa cultivar. Within each square, 4 diets were tested: the control diet was formulated for an adequate supply of MP and energy (AMP_ AE), whereas the 3 other diets were formulated to be deficient in MP (DMP; formulated to meet 90% of the MP requirement) with deficient (94% of requirement: DMP_DE), adequate (99% of requirement: DMP_ AE), or excess energy supply (104% of requirement; DMP_EE). Alfalfa cultivars had no significant effect on all measured parameters. As compared with cows receiving AMP_AE, the dry matter intake of cows fed DMP_AE and DMP_EE was not significantly different but decreased for cows fed DMP_DE. The AMP_AE diet provided 103% of MP and 108% of NEL requirements whereas DMP_DE, DMP_AE, and DMP_EE diets provided 84, 87, and 87% of MP and 94, 101, and 107% of NEL requirements, respectively. In contrast to design, feeding DMP_EE resulted in a similar energy supply compared with AMP_AE, although MP supply has been effectively reduced. This resulted in a maintained milk and milk component yields and improved the efficiency of utilization of N, MP, and essential AA. The DMP diets decreased total N excretion, whereas DMP_AE and DMP_EE diets also decreased milk urea-N concentration. Reducing MP supply without negative effects on dairy cow performance is possible when energy, dHis, dLys, and dMet requirements are met. This could reduce N excretion and decrease the environmental impact of milk production.Keywords
This publication has 61 references indexed in Scilit:
- TRIENNIAL LACTATION SYMPOSIUM: Mammary metabolism of amino acids in dairy cows1,2Journal of Animal Science, 2012
- Review: Ammonia emissions from dairy farms and beef feedlotsCanadian Journal of Animal Science, 2011
- Impacts of manipulating ration metabolizable lysine and methionine levels on the performance of lactating dairy cows: A systematic review of the literatureLivestock Science, 2010
- Protection of fatty acids against ruminal biohydrogenation in cattleEuropean Journal of Lipid Science and Technology, 2007
- Emissions of ammonia, nitrous oxide and methane from different types of dairy manure during storage as affected by dietary protein contentThe Journal of Agricultural Science, 2001
- Relation between nutrition, performances and nitrogen excretion in dairy cowsAnimal Research, 2000
- Cell Wall Structural Foundations: Molecular Basis for Improving Forage DigestibilitiesCrop Science, 1999
- Effect of growth and cultivar on alfalfa digestibility in a multi-site trialAgronomy for Sustainable Development, 1997
- The effect of dietary N onin vitrolipolysis and fatty acid hydrogenation in rumen digesta from sheep fed diets high in starchThe Journal of Agricultural Science, 1983
- Influence of Soil Moisture and Ambient Temperature on Yield and Quality of Alfalfa Forage1Agronomy Journal, 1971