Nutrient Requirements for Dairy Cattle of the National Research Council Versus Some Commonly Used Ration Software

Abstract

The first edition of the Nutrient Requirements of Dairy Cattle was published by the National Research Council (NRC) in 1945. The current document is the sixth revised edition, published in 1989, and it appears that we are a few years from another edition being in print. Software designed to evaluate and formulate rations for dairy cattle commonly determine nutrient requirements using the NRC as a standard. However, the generation of new knowledge in dairy nutrition occurs more rapidly than the release of the NRC publication, and the developers of the software often modify the requirements based on more recently published research, geographical peculiarities, or factors not explicitly considered by NRC. The first step in evaluating or formulating rations is the prediction of dry matter intake (DMI). The primary variables used by NRC to predict DMI are body weight (BW) and fat-corrected milk (FCM) yield; however, developers of software programs often use different equations based on personal preference, availability of research data with given equations, and incorporation of other factors in addition to BW and FCM yield. The additional factors are included to provide a more dynamic estimation of DMI and, therefore, reduce the difference between predicted and actual DMI. Nutrients required for maintenance, lactation, and growth must be consumed in adequate quantities (e.g., kilograms or calories), but the dietary concentration of nutrients for a given animal group may differ because of DMI. Even when nutrients are fed above the requirements, dietary concentrations of nutrients may be important in some situations to minimize the risk of underfeeding caused by variability in the nutrient composition of feedstuffs and to account for interactions of certain nutrients (e.g., minerals). New research discoveries need to be incorporated into ration formulation strategies promptly, and the strategies used for ration formulation need to be dynamic.

Heat production, eating behavior and milk yield of lactating cows fed two rations differing in roughage content and digestibility under heat load conditions

“…Voluntary DMI can decrease by as much as 6% when ambient temperatures rise above 30°C (Eastridge et al, 1998). Accordingly, Miron et al (2003) suggested that the NRC (2001) recommendation of 18-19% minimal content in diets of neutral detergent fiber (NDF) from roughage might be too high.…”

Heat production and retained energy in lactating cows held under hot summer conditions with evaporative cooling and fed two rations differing in roughage content and in vitro digestibility

“…Voluntary DMI can decrease by as much as 6% when ambient temperatures rise above 308C (Eastridge et al, 1998). Therefore, under hot weather conditions during the summer, most of the dairy farms in Israel cool the lactating cows by 'evaporative cooling', namely an arrangement whereby first the cows are made wet using sprinklers and then exposed to fans to promote evaporation (Flamenbaum et al, 1986;Berman, 2005).…”

Factors affecting dry matter intake prepartum in relationship to etiology of peripartum lipid-related metabolic disorders: A review

“…Researchers have suggested that minimizing DMI depression or increasing nutrient density of the diet during the prefresh transition period would be an essential strategy to alleviate severity of negative energy balance, maintain body reserves, increase nutrients available for rapid fetal growth, ease metabolic transition from pregnancy to lactation, and acclimate rumen microorganisms to lactation diets (Grummer 1995;Nocek 1995;Van Saun 1991). Eastridge et al (1998) compared nutrient density recommendations for dairy cattle published in the previous edition of NRC (NRC 1989) to those generated by commonly used diet formulation programs. These programs computed greater nutrient densities than those recommended by the previous edition of NRC (NRC 1989).…”