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Research review: What’s new in the revised edition of the Nutrient Requirements of Dairy Cattle (2001) of the NRC? – Part 2

Contributed by Hélène Lapierre Published on 28 July 2022

Prediction of milk protein yield

The NRC (2001) prediction of milk protein yield was based on metabolizable protein (MP) requirements and supply and a fixed efficiency of utilization of 67% of this supply.

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A multivariate equation including digestible energy supply, five individual essential amino acids (EAAs), the sum of the other amino acids, neutral detergent-soluble fibre and live weight was developed using a large database. In addition, the inclusion of a quadratic factor in the equation indicates that, with high EAA supplies, a production plateau is reached. The prediction of milk protein yield is also adjusted according to the rolling herd rolling average of milk protein (kilograms per 305 days).

Essential amino acid recommendations

The proposed multivariate equation does not, however, make it possible to detect whether there is an imbalance in certain EAAs. To determine the recommendations for the individual EAA and to verify if the rations meet these recommendations, the concept of efficiency of utilization of MP and of each EAA was developed.

For a given ration and production level, the same efficiency of utilization is attributed to the MP or to each EAA for all functions involving protein secretion. These functions, the same as in NRC (2001), are the scurf, metabolic fecal protein and milk protein. This same efficiency is also used for growth (protein component) of the lactating cows. An efficiency of 100% was assigned to urinary endogenous losses. Using the database created for the milk protein yield prediction equation, the efficiency of utilization of MP and EAA was calculated for each of the treatment means (more than 800 data points). The efficiencies calculated using that method were highly variable. A target efficiency was determined to estimate the recommendations for MP and each EAA. This target efficiency is valid if the energy supply adequately meets the requirements.

Therefore, the recommendations for MP and EAA are calculated as follows (grams per day): [(true protein or EAA in scurf + metabolic fecal protein + milk protein + growth) / target efficiency] + urinary endogenous losses. These recommendations for each EAA make it possible to verify whether the supply predicted for one or more EAAs with the proposed ration might be limiting for the desired production level.

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The benefits of the revision

This revised model better reflects the biological mechanisms underlying protein and EAA supply and utilization. Recommendations are now given for all EAAs. An additional advantage of such a model is that its structure will facilitate incorporation of new knowledge in the future. end mark

Hélène Lapierre, agr., Ph.D., is with Agriculture and Agri-Food Canada, Sherbrooke Research and Development Centre.

Dairy Farmers of Canada (DFC) invests in scientific research to foster innovation in the Canadian dairy sector. DFC supports research initiatives that benefit all Canadian dairy farmers and works in collaboration with its members and other sector partners to address priorities outlined in the National Dairy Research Strategy. The goals of this strategy are to increase farm efficiency and sustainability, enhance animal health, care and welfare practices, and strengthen the role of dairy in human nutrition and health, as well as in sustainable diets. Visit Dairy Farmers of Canada - Dairy Research for more information.

Dairy Farmers of Canada’s 2021-22 Research Highlights now available

Dairy Farmers of Canada’s (DFC) 2021-22 Research Highlights is now available for download on DFC’s website (Dairy Farmers of Canada - Dairy Research). The publication contains relevant information on DFC’s investments in dairy production and human nutrition and health research, its research funding partners, ongoing research projects as well as some of the key outcomes resulting from research and knowledge translation and transfer (KTT) activities.

Excerpts from the 2021-22 Research Highlights

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Investments in research

  • In 2021-22, DFC invested $2 million in dairy production and human nutrition and health research, which was boosted to a total of $11 million by leveraging investments through grant programs and partnerships. DFC and 30 partners support scientific research to drive innovation in the Canadian dairy sector.

  • 45 research projects are in progress at 34 research institutions across Canada.

  • More than 140 scientists and 135 graduate students and postdocs are conducting studies in dairy production and human nutrition and health.

  • More than 1,000 dairy farmers from coast to coast are investing their time as part of several research projects to help drive innovation in the Canadian dairy sector.

Key outcomes from DFC investments in research and KTT

  • In-barn water use and heat stress indicators were measured on Canadian dairy farms instrumented to measure barn water use and environmental conditions inside and outside the barns. With these data, the team developed water use benchmarks and equations relating outdoor weather conditions to in-barn conditions.

  • A web application to help dairy farmers explore correlations between production traits for Canadian Holstein dairy animals (Estimated genetic parameters for all genetically evalusted traits in Canandian Holsteins).

  •  Bulk tank fatty acid profile as a tool to monitor and adjust management and housing in automated milking system farms.

  • A training and integration tool for dairy production workers: Let’s test your knowledge. Cow … me on! The kit, available in English, French and Spanish, was developed by AGRICarrières in collaboration with the Mastitis Network, Lactanet and the Canadian Dairy Commission. (AGRICarrières)

  • A training tool for graduate students, dairy veterinarians, teachers and interested individuals, the Bovine Mastitis MOOCs series, developed by the Mastitis Network with the collaboration of experts from more than 20 countries (Mastitis Network - Online open courses MOOCs).

  • A large Canadian study of 7,945 Canadian participants demonstrated a beneficial role for dairy foods in cognitive health of older adults.

  • A landmark study, including 7,195 residents in 60 Australian aged care facilities, has reinforced the role of milk products in bone health.

  • A randomized controlled trial of 58 Canadian adults consuming dairy two hours before a meal, showed a decrease in appetite, blood glucose and later food intake compared to water.

  • Videos, podcasts and infographics from DFC’s first online competition for graduate students to engage students in creating innovative content for research users.

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