Potential of solubility, enzymatic methods and NIRS to predict in situ rumen escape protein

Abstract

The percentage of feed protein escaping rumen degradation was measured by the in situ method (%EPsitu) for 29 compound feeds, untreated and formaldehyde-treated soyabean meal and 12 forages: 3 grass silages, 2 maize silages, fresh grass, grass hay, fodder beets, fresh potatoes, ensiled beet pulp, chopped ear-maize silage and brewers' grains. Loss of particles through bag pores was determined by the difference between the washable fraction (W) and the fraction soluble in borate-phosphate buffer at pH 6.7 (S). W - S was most pronounced for compound feeds (on average 14.4 percentage units), for brewers' grains and maize silages. A correction of %EPsitu, assuming that W - S degrades like the potentially degradable fraction, was not appropriate. Solubility in borate-phosphate buffer after 1 h, enzymic degradability by protease from Streptomyces griseus or ficin after 1, 6 and 24 h and near infrared reflectance spectroscopy (NIRS) (for compound feeds alone) were examined as a routine method to predict %EPsitu. With the buffer and S. griseus the effect of pH (6.7 vs. 8.0) and at pH 8.0 the effect of amount of substrate (500-mg sample vs. 20 mg N) were tested. With ficin, 500-mg samples were incubated at pH 6.7. Predictions were better when compound feeds and forages were considered separately. However, the best in vitro method was different for the 2 feed categories, being solubility in buffer for the compound feeds and enzymic degradation of a constant amount of protein with S. griseus at pH 8.0 for forages. NIRS showed potential to predict %EPsitu of compound feeds, but needs more reference samples. The Dutch feed tables appeared more accurate than the best in vitro method for compound feeds, but was too inaccurate for some forages like fodder beets, maize silage and ear-maize silage.

In vitro gas production profile and the formation of end products from non‐ washable, insoluble washable and soluble washable fractions in some concentrate ingredients

“…Much information is available on the degradative behaviour in the rumen of starches, proteins and cell walls present in the D fraction, but this is not the case for these components in the W fraction. It has become apparent that part of the W fraction may in fact consist of small insoluble particles and their degradative behaviour is likely to be more similar to the D fraction than to the W fraction 3, 4. The combination of feed fractionation that separates the W fraction into an insoluble washable (ISWF) and a soluble washable fraction (SWF), and in vitro gas and VFA production techniques is considered a promising method to characterise the degradative behaviour of these fractions in feedstuffs 5–7.…”

Effect of Rice Wine Distillers By-Product on Digestibility and Nitrogen Retention in Pre-Pregnant Bach Thao Goats

“…Animal nutritionists have started to use NIRS to evaluate feed digestion and animal performance. De Boever et al (1997) assessed application of NIRS for predicting ruminal in situ degradability of feeds and reported favourable prediction potential of NIRS. Efforts have also been made to develop calibration equations for measuring kinetic parameters of nutrients by using in vitro methods as a reference (Herrero et al, 1996;Andres et al, 2005).…”

La spectrométrie dans le proche infrarouge pour la caractérisation des ressources alimentaires

“…Les minéraux n'absorbent pas dans la région du proche infrarouge mais les complexes que peuvent former les minéraux avec des composés organiques peuvent être détectés par la SPIR et servir de base à la prédiction. En pratique, plusieurs études ont présenté des résultats avec des succès contrastés (Clark et al, 1987 ;Ward et al, 2011 Boever et al (1997) reportent des erreurs de prédiction (SEP) de 2 % pour la prédiction de la digestibilité de la matière organique (dMO) du maïs fourrager, tandis que Coelho et al (1988) sur des foins et Barber et al (1990) sur des ensilages d'herbe rapportent des étalonnages avec des SEP compris entre 2 et 4 %. La prédiction des valeurs de dMO obtenues in vivo par la SPIR n'est pas évidente.…”