California net energy system for Bos taurus indicus
Mario Luiz Chizzotti1, Sebastião de Campos Valadares Filho1, Pedro Del Bianco Benedeti2
1Department of Animal Science, Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil.
Translational Animal Science
|July 25, 2020
Summary
This study compares beef cattle energy requirement systems, NASEM and BR-CORTE. BR-CORTE better estimates energy needs for Zebu cattle, particularly during pregnancy, while both systems align on lactation energy needs.
Area of Science:
- Animal Science
- Nutritional Physiology
- Ruminant Metabolism
Background:
- The California net energy system (CNES) influenced global beef cattle energy requirement models.
- Key models include the Nutrient Requirements of Beef Cattle (NASEM) and Brazilian Nutrient Requirements of Zebu and Crossbred Cattle (BR-CORTE).
- Differences in methodology between NASEM and BR-CORTE warrant comparative analysis for accurate energy estimation.
Purpose of the Study:
- To compare the energy requirement estimation methods of NASEM and BR-CORTE for beef cattle.
- To evaluate discrepancies in net energy for maintenance (NEm), gain (NEg), pregnancy (NEp), and lactation.
- To assess the suitability of each system for different cattle types, particularly Zebu and crossbreds.
Main Methods:
- Comparative analysis of NASEM and BR-CORTE methodologies for estimating beef cattle energy requirements.
- Evaluation of NEm based on empty body weight (EBW) in BR-CORTE versus shrunk body weight (SBW) in NASEM.
- Comparison of NEg, NEp, and lactation energy requirements under defined gain and physiological states.
Main Results:
- BR-CORTE's NEm estimation is more appropriate for *Bos taurus indicus* breeds due to lower requirements compared to *Bos taurus taurus*.
- Both systems predicted similar NEg for 1.8 kg/day gain, but NASEM underestimated empty body gain with equivalent metabolizable energy.
- BR-CORTE estimated lower NEm and NEp for Zebu cows than NASEM, with NEp differences increasing with pregnancy progression.
Conclusions:
- BR-CORTE provides more accurate energy requirement estimates for Zebu and crossbred cattle, especially concerning maintenance and pregnancy.
- NASEM and BR-CORTE show similar predictions for lactation energy requirements per kilogram of milk.
- Systematic differences highlight the importance of breed-specific considerations and weight basis (EBW vs. SBW) in energy requirement models.
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