‘Green Book’ Guidelines No Longer Suitable for Estimating Net Energy Requirements for Beef Production

The Swiss ‘Green Book’ feeding recommendations for fattening cattle are no longer suitable for today’s animals and current production conditions. An updating of datasets for system calibration is essential.

In Switzerland, cross-bred bull calves from dairy herds, finished on fattening farms, account for 35% of beef meat production. In order to improve the economic and environmental performance of these herds, feed autonomy must be maximised whilst mitigating emissions (greenhouse gases, nitrogen efflux). At the scale of the individual animal and its production system, this improvement is largely based on increased feed efficiency. This requires precise feeding requirements systems which take the aforementioned challenges into account.

Evolution of the beef production sector

In Switzerland, the feeding requirements system developed by Agroscope is documented in the chapter of the ‘Green Book’ entitled Apports alimentaires recommandés pour le bovin à l’engrais (‘Recommended Feed Requirements for Beef Cattle’). Only the data on dry-matter intake were adapted in 2018. The remaining ‘Green Book’ recommendations are essentially based on the French INRA feeding system, validated and adapted for Swiss rearing conditions in the 1970s and ’80s. In terms of e.g. animal genetics, production systems and the political/economic context, however, the Swiss beef cattle sector has evolved on numerous levels over the past 50 years. Today, the ‘Green Book’ recommendations for fattening bulls must be evaluated according to current production managements that are representative of national production conditions, in order to enable the recommendation or otherwise of current use, and to plan an upgrading of the system if need be.

Experimental observations vs. ‘Green Book’ estimates

This study compared experimental observations and ‘Green Book’ estimates for intake quantities of net energy for meat production (NEm) and absorbable proteins in the intestine (API) for three groups of bulls fattened on rations of variable energy density. The choice of feedstuffs and energy content of the three rations was made on the basis of current bull-fattening practices in Switzerland. Together with animal performance (feed-intake level and body-weight kinetics), parameters of a physiological (body composition) and behavioural nature (feeding behaviour and physical activity) were gathered in order to explain presumed differences between experimental observations and ‘Green Book’ predictions. A deviation of the order of 20% for energy requirements and 2% for absorbable proteins was recorded between the ‘Green Book’ estimates and the experimental observations. For energy, differences in body weight at the end of the trial, average daily gain, body composition and physical activity of the bulls may partially account for these differences.