Nejc Valcl

1. Sufficient dietary protein flow is critical for high‑producing cattle. Soybean meal (SBM) is a common protein feed for beef and dairy cows, with a high crude protein (CP) content and a favourabl...

In dairy ruminant nutrition high producing animals require an adequate flow of protein post-rumen to achieve optimal milk production. Rapeseed meal (RSM) is a protein feed used in dairy ruminant nu...

Optimizing dietary protein utilization is essential for improving ruminant nutrition, and tannins can reduce the ruminal degradability of soybean meal (SBM) proteins through tannin–protein complex formation, a process enhanced by water. This study evaluated three water levels (1:0.625, 1:1.25, 1:2.5 w/v) combined with chestnut or quebracho tannins at 50 and 100 g/kg on in vitro dry matter (DM) and crude protein (CP) degradability and digestibility of SBM. Increasing water levels significantly reduced crude protein degradability (p < 0.05), with the greatest decline observed for chestnut tannins at 100 g/kg, decreasing from 640 g/kg at the lowest water level to 423 g/kg at the highest. Post-ruminal crude protein digestibility increased slightly with water for this treatment (from 977 to 984 g/kg). Bypass protein content ranged from 138 g/kg (quebracho 100 g/kg, low water) to 563 g/kg (chestnut 100 g/kg, high water), with increases of 20.7% and 22.6% for chestnut tannins at 50 and 100 g/kg, respectively. Bypass protein digestibility improved by up to 4.4%. Dry-matter degradability decreased by 6.8% to 23.5% depending on treatment. These findings demonstrate that water greatly enhances tannin efficacy and highlight its potential for improving protein utilization.

Soybean meal is a widely used protein source for ruminants, but its high ruminal degradability can limit its nutritional value. Tannins reduce ruminal crude protein degradability by forming tannin-protein complexes, which are facilitated by water addition and heat during drying. The study evaluated the effects of drying methods (freeze-dried, 50 °C, 80 °C) combined with two tannin types (chestnut and quebracho) at two concentrations (50 and 100 g/kg) on the in vitro degradability and digestibility of soybean meal dry matter and crude protein. Tannins combined with drying methods effectively reduced ruminal degradation of soybean meal protein. The drying at 80 °C combined with chestnut or quebracho tannins at both concentrations (except 100 g/kg chestnut tannins) showed the largest reduction in ruminal crude protein degradability without negatively affecting post-ruminal digestibility. The most effective combination for reducing crude protein (-42.3%) degradability compared to the control was 50 g/kg chestnut tannins with drying at 80 °C without affecting in vitro dry matter and crude protein digestibility. This combination also increased by-pass protein content (431 g/kg DM) and improved its digestibility by 21%.

Gas production from thirty samples of feedstuffs (10 samples of corn silage, grass silage, and grass hay, respectively) was assessed in vitro using two methods: the Hohenheim gas test (HGT) and the ANKOM RF Gas Production System (ANKOM). Samples were incubated in buffered rumen fluid. Gas kinetic parameters were calculated using the Gompertz model. Results revealed significantly lower gas production with the ANKOM compared to the HGT. Significant differences were observed between the HGT and ANKOM in the specific gas production rate (parameter C), maximum fermentation rate (MFR) and gas produced after 24 h of incubation (Gas24) for each feed group. High coefficients of determination (R2) were calculated between the methods for the gas kinetic parameters MFR, Gas24, total potential gas production (parameter B), decrease in the specific gas production rate (parameter A), moderate R2 for C, and low R2 for time of maximum fermentation rate (TMFR). Despite the lower quantities of gas generated with the ANKOM, there are strong correlations in the parameters of gas kinetics that promise the possibility of developing correction models. Future development of such models could position the ANKOM as a viable alternative to HGT, particularly for calculating metabolizable energy and net energy for lactation in feedstuffs.

Background: Accurate dosing of feed additives is often required to evaluate their effects on rumen fermentation. This can be done using soluble but nonfermentable hydroxypropyl methylcellulose (HPMC) hard capsules.Objectives: The aim of the study was to evaluate the effect of HPMC hard capsules on the extent and rate of in vitro gas production in eleven feeds.Methods: Six high‐fibre feeds and five concentrates, were weighed into syringes either directly or into HPMC capsules and incubated anaerobically in 30 mL buffered rumen fluid at 39°C. Data obtained from gas production measurements were fitted using the Gompertz model to obtain kinetic parameters for gas production.Results: HPMC hard capsules had no effect on the gas production of the blank sample and concentrate feeds. In contrast, high‐fibre feeds weighed in HPMC showed a significant decrease (p < 0.05) in total gas production and gas produced within 24 h of incubation.Conclusions: The use of HPMC hard capsules was found to be inappropriate for determining gas production kinetics because fermentation subsides at a certain point when peak fermentation is reached (at TMFR), resulting in a decrease in both total potential gas production and gas production within 24 h of incubation. This is particularly evident when high‐fibre feeds are incubated.