Validation of protein evaluation systems by means of milk production experiments with dairy cows

Abstract

Protein evaluation systems (crude protein (CP), digestible crude protein (DCP), protein digested in the intestine (PDI), amino acids truly absorbed in the small intestine (AAT), absorbed protein (AP), metabolizable protein (MP), crude protein flow at the duodenum (AAS) and digestible protein in intestine (DVE)) were validated using data from 15 production experiments with dairy cows, carried out in the Netherlands. Only treatments that were deficient in protein according to at least one system were selected. Average yield was 31.2 kg of fat and protein corrected milk daily and 989 g of milk protein daily. The observed milk protein production was compared with milk protein production predicted from the protein supply and requirements in each system. The difference between observed and predicted milk protein production expressed as the absolute and relative prediction error was smallest for the DVE-system (-2 g/day; 5.7%) and increased in the order CP (-22 g/day; 6.7%), PDI (-19 g/day; 7.8%), DCP (-44 g/day; 8.8%), AP(-37 g/day; 9.3%), AAS (100 g/day; 11.7%), AAT (112 g/day; 13.4%) and MP system (204 g/day; 22.9%). Predictions can be improved when a variable efficiency of milk protein production is used. In the DVE-system the observed efficiency decreased with increasing protein to energy ratio in the diet and milk production level. It was concluded that under Dutch conditions the prediction of milk protein production decreased in the order DVE, CP, PDI, DCP, AP, AAS, AAT and MP system.

Update of the Dutch protein evaluation system for ruminants: the DVE/OEB2010system

“…Furthermore, such models enable the assessment of diet adequacy under a range of management and feeding situations (Fox et al 2004). Some other, older, studies (Van Straalen et al 1994;Tuori et al 1998) have reviewed and/or compared different protein evaluation systems. Therefore, in this section, model comparisons have been limited to two other recently published protein evaluation systems, the CNCPS in the USA (Fox et al 2004) and the FiM system in the UK (Offer et al 2002;Thomas 2004).…”

“…Some other, older, studies (Van Straalen et al . 1994; Tuori et al . 1998) have reviewed and/or compared different protein evaluation systems.…”

Simulation of digestion in cattle fed sugarcane: prediction of nutrient supply for milk production with locally available supplements

“…In our calculations, as in all protein evaluation systems, a constant efficiency of synthesis of milk protein from absorbed amino acids (0-716 g milk protein/g absorbed amino acid; ARC 1980) was adopted. However, diminishing returns of milk protein with increasing amino acid flow to the duodenum have been reported (MacRae et al 1988) and low ratios of absorbed amino acids to energy are related to high efficiencies of utilization of absorbed amino acids to milk protein (Van Straalen et al 1994). In view of this variable efficiency, the severity of amino acids limiting milk protein production might be less remarkable.…”

Effects of Rumen Undegradable Protein and Minerals Proteinate on Early Lactation Performance and Ovarian Functions of Dairy Cows in the Tropics

“…The biological value of protein for dairy cows is directly related to the energy status of the dairy cows and the balance of absorbed amino acids relative to their requirement (Van Straalen et al, 1994). Reduced energy consumption and increased energy maintenance requirement during heat stress often results in considerably more protein being metabolized to meet energy requirements of dairy cows (Beede and Collier, 1986).…”