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The objective of this study was to evaluate fermentation characteristics and associative effects by replacing maize silage (MS) with red clover silage (RCS) using in vitro techniques. Treatments included total mixed rations (TMR) containing forage (MS and RCS) and concentrates (0.75:0.25) with targeted proportions of RCS in TMR of 0.15 (RCS 15 ), 0.30 (RCS 30 ), 0.45 (RCS 45 ), and 0.60 (RCS 60 ) on a dry matter (DM) basis. The Hohenheim gas test (HGT) was used to describe the kinetic of gas production. The modified HGT was used to estimate the utilizable crude protein at the duodenum (uCP). Effective uCP was calculated according to passage rates of 2, 5 and 8%/h (uCP 2 , uCP 5 and uCP 8 , respectively). Associative effects were defined as the differences (%) between the observed values of TMR and the sum of the observed values of the individual components of the TMR. The gas production from incubation time 8 to 72 h, the potential gas production (A), organic matter digestibility (OMD), and metabolizable energy (ME) decreased with increasing levels of RCS. The effective uCP 2 content was similar between TMR (average 93.7 g/kg DM). However, uCP 5 and uCP 8 were reduced with increasing level of RCS (from 145 to 136 g/kg DM, and from 172 to 157 g/kg DM). Positive associative effect was found for cumulative gas production. But this effect was reduced when increasing incubation time and when increasing levels of RCS. Associative effects of gas production at 24 h of incubation averaged 1.35%. Consequently, those of ME (−0.09 to 1.01%) and OMD (1.60 to 2.76%) were of minor relevance as well. Associative effects on uCP depended on rate of passage and on level of RCS. Within TMR, associative effects on uCP increased with increasing rate of passage (e.g. for RCS 15 ; 3.67 and 5.39% for 2 and 8%/h, respectively). Within rate of passage, associative effect was reduced with increasing level of RCS (e.g. for uCP 8 ; 5.39 and −0.95% for RCS 15 and RCS 60 , respectively). Based on associative effects of fermentation characteristics and estimated uCP content, this study suggests that incrementing levels of RCS may lead to a reduction on the feed value of diets, and that the optimal proportion of RCS:MS in TMR to achieve beneficial effects was 0.15:0.60 on DM basis. Therefore, caution should be taken before introducing high levels of RCS in rations of high-yielding dairy cows. However, these results should not be directly extrapolated to in vivo conditions. [ABSTRACT FROM AUTHOR]

The objective of this study was to characterise the variation of utilisable crude protein at the duodenum (uCP) of dried distillers’ grains with solubles (DDGS) for ruminants using a modified gas test and to predict the uCP in DDGS based on chemical composition. Thirteen samples originating from wheat, maize, barley or blends of different substrates were studied. Thein vitrouCP was estimated using the modified Hohenheim gas test (moHGT). Samples were incubated in rumen fluid for 8 h, 24 h and 48 h followed by ammonia distillation. The obtained values were compared to reference values of uCP (based on the contents of crude protein (CP),in situundegraded CP and metabolisable energy). The reference andin vitrovalues of uCP were calculated according to passage rates of 2, 5 and 8%/h (i.e., uCP2, uCP5and uCP8, respectively). The in vitrouCP8ranged from 214 to 320 g/kg DM and reference values from 158 to 302 g/kg DM. The in vitrouCP2was on average lower (by 7 g/kg DM) andin vitrouCP8was higher (by 56 g/kg DM) than their respective reference values. Thein vitrouCP5and uCP8were correlated with reference values and the correlations were improved with increasing passage rates. When the differences of uCP content betweenin vitroand reference values were related to CP fractions, they increased with increasing content of CP fraction A and decreasing content of CP fraction B3 for uCP8. The prediction of uCP values from chemical composition was not reliable. It was concluded that uCP can be predicted on the basis of the moHGT method and CP fractions. The accuracy of prediction improved upon the inclusion of CP fractions and neutral-detergent insoluble nitrogen. The present study revealed a significant variation in the uCP content of DDGS, which should be considered when formulating rations for dairy cows. [ABSTRACT FROM AUTHOR]

The objective of this study was to characterise variations in the composition and nutritive value of dried distillers’ grains with solubles (DDGS) for ruminants, and to estimate the undegradable crude protein (UDP) in DDGS. Thirteen samples originating from wheat, corn, barley and blends of different substrates were studied. The rumen degradation of crude protein (CP) was determined using the nylon bag technique. Samples were incubated for 0, 1, 2, 4, 8, 16, 32 and 72 h, and in situ degradation kinetics were determined. The UDP was estimated using a passage rate of 8%/h. In vitro gas production was measured to estimate the metabolisable energy (ME), net energy for lactation (NEL) and in vitro digestibility of organic matter (IVDOM). Chemical profiles varied among samples [in g/kg dry matter (DM) ± standard deviation]; the values were 310 ± 33 CP, 86 ± 37 ether extract, 89 ± 18 crude fibre, 408 ± 39 neutral detergent fibre, 151 ± 39 acid detergent fibre and 62 ± 31 acid detergent lignin, as well as in protein fractions according to the Cornell Net Carbohydrate and Protein System [in g/kg CP]; the values were for fractions A, 161 ± 82; B1, 24 ± 11; B2, 404 ± 105; B3, 242 ± 61; and C, 170 ± 87. The ME, NEL [MJ/kg DM] and IVDOM [%] also varied among samples: 12.1 ± 0.59, 7.3 ± 0.39 and 72.5 ± 4.30, respectively. The in situ rapidly degradable CP fraction (a) varied from 10.2% to 30.6%, and the potentially degradable fraction (b) averaged to 66.8%. The UDP varied from 8.6% to 62.6% of CP. The present study suggests significant variations in composition and nutritive value among different sources of DDGS. The UDP could be predicted on the basis of analysed CP fractions, but the accuracy of UDP prediction improved upon the inclusion of neutral-detergent insoluble nitrogen, explaining 94% of the variation in the UDP values. We conclude that chemical protein fractions may be used to predict the UDP values of DDGS and that the variability in the protein fractions of DDGS should be considered when formulating diets for dairy cows. [ABSTRACT FROM AUTHOR]