Feeding barley grain steeped in lactic acid modulates rumen fermentation patterns and increases milk fat content in dairy cows

Abstract

The objectives of the present in vivo and in situ trials were to evaluate whether feeding barley grain steeped in lactic acid (LA) would affect rumen fermentation patterns, in situ dry matter (DM) degradation kinetics, and milk production and composition in lactating dairy cows. The in vivo trial involved 8 rumen-fistulated Holstein cows fed once daily a total mixed ration containing rolled barley grain (27% in DM) steeped for 48 h in an equal quantity of tap water (CTR) or in 0.5% LA (TRT) in a 2 x 2 crossover design. The in situ trials consisted of incubation of untreated rolled barley grain in cows fed CTR or TRT diets and of incubation of 3 different substrates including CTR or barley grain steeped in 0.5% or 1.0% LA (TRT1 and TRT2, respectively) up to 72 h in the rumen. Results of the in vivo trial indicated that cows fed the TRT diet had greater rumen pH during most intensive fermentation phases at 10 and 12 h post-feeding. The latter effect was associated with a shorter duration in which rumen pH was below 5.8 for cows fed the TRT diet (2.4 h) compared with CTR diet (3.9 h). Furthermore, cows fed the TRT diet had lower concentrations of volatile fatty acids at 2 and 4 h post-feeding. In addition, concentrations of preprandial volatile fatty acids were lower in the rumen fluid of cows fed the TRT diet. Results also showed that molar proportion of acetate was lower, whereas propionate tended to increase by feeding cows the TRT diet. Cows fed the TRT diet demonstrated greater rumen in situ lag time of substrate DM degradation and a tendency to lower the fractional degradation rate. Other in situ results indicated a quadratic effect of LA on the effective rumen degradability of substrates whereby the latter variable was decreased from CTR to TRT1 but increased for TRT2 substrate. Although the diet did not affect actual milk yield, fat-corrected milk, percentages of milk protein, and lactose and concentration of milk urea nitrogen, cows fed the TRT diet increased milk fat content and tended to increase fat:protein ratio in the milk. In conclusion, results demonstrated that treatment of barley grain with LA lowered the risk of subacute rumen acidosis and maintained high milk fat content in late-lactating Holstein cows fed diets based on barley grain.

Influence of barley grain particle size and treatment with citric acid on digestibility, ruminal fermentation and microbial protein synthesis in Holstein calves

“…Treating cereals with organic acids may contribute to modulate ruminal tolerance of grain feeding and alleviate the digestive disorders (Iqbal et al, 2009;Humer et al, 2015), thus improving ruminant performance and health. The increased weight gain with a similar feed intake observed in calves fed the TRT diet compared with the CTR diet resulted in a better feed efficiency.…”

“…Treating cereals with other organic acids (LA) also decreased starch degradation in the rumen, shifting the digestion of starch to the intestine in dairy cows (Iqbal et al, 2009). Ruminal NH 3 -N concentration was increased with CA-treated barley grain.…”

“…In the control (CTR) barley, 1 kg of barley was soaked in an equal volume (1 l) of tap water. In both cases, ground barley was soaked for 48 h before being incorporated into the TMR, following the approach described by Iqbal et al (2009). The batch size for the preparation of treated and control barley was 80 kg.…”

“…One alternative chemical treatment to increase RRS is the addition of organic acids (Deckardt et al, 2016) to cereal grains. The addition of lactic acid (LA) to barley grain increased RRS and decreased ruminal fermentation rate of barley starch, with a subsequent decrease of rumen VFA concentrations preventing a drop in pH, thus enhancing the productivity and health of dairy cows (Iqbal et al, 2009). Treatment of barley grain with other organic acids, such as citric acid, also increases RRS (Harder et al, 2015a and2015b).…”

Metabolomics reveals unhealthy alterations in rumen metabolism with increased proportion of cereal grain in the diet of dairy cows

“…These VFA observations were made using traditional analytical methods such as GC and HPLC (Iqbal et al 2009). Previous research has indicated that feeding cattle with diets rich in readily degradable carbohydrates, such as barley grain, is associated with increased concentration of VFA in the rumen fluid.…”