Long-term reticuloruminal pH dynamics and markers of liver health in early-lactating cows of various parities fed diets differing in grain processing

Abstract

The present study aimed to investigate the long-term effect of feeding barley grain steeped in lactic acid (La) with or without thermal treatment on reticuloruminal pH dynamics and metabolic activity of the liver in 12 primiparous and 18 multiparous early-lactating dairy cows. All cows were included on d 21 postpartum and sampled until d 90 postpartum. Cows were fed a diet based on differently processed ground barley grain: untreated grain (control diet, CON), or grain treated with 1% La alone for 24 h before feeding (La), or with an additional oven-heating at 55°C for 12 h (LaH). The reticuloruminal pH and temperature were measured via indwelling sensors that allowed for continuous (every 10min) and long-term measurement from d 21 to 80 postpartum. Blood samples were taken on d 21, 40, and 90 of lactation and analyzed for liver enzymes aspartate aminotransferase (AST), gamma-glutamyltransferase, and glutamate dehydrogenase, as well as bilirubin, bile acids, and serum amyloid A. Dry matter intake was higher in multiparous cows (20.7±0.27 kg/d) compared with primiparous cows (18.2±0.33 kg/d), but was not affected by dietary treatment. Overall, the relatively short duration (51±5min/d) of reticuloruminal pH <5.8 suggests low risk of subacute ruminal acidosis throughout the experiment. Results indicated that La treatment of barley, with or without heat, lowered the time duration of pH <5.8 compared with CON, but only in primiparous cows (from 118±13 to 46±11 and 25±11min/d for CON, La, and LaH, respectively). In multiparous cows, the opposite effect of feeding the La-treated barley on time duration of pH <5.8 (11±8 vs. 46±9 vs. 57±9min/d for CON, La, and LaH, respectively) was observed. Multiparous cows generally showed higher pH readings and shorter periods in which the ruminal pH dropped below the threshold of pH 5.8. The reticuloruminal temperature was not affected by dietary treatment, whereas parity affected the time duration of reticuloruminal temperature >39.5°C, being 60±19min/d shorter in primiparous cows. The measured activities of the liver enzymes AST, gamma-glutamyltransferase, and glutamate dehydrogenase, as well as bilirubin, bile acids, and the acute phase protein serum amyloid A, were not affected by grain feeding. Additionally, only one small effect of parity on investigated serum variables was noticed, showing slightly but significantly higher values of AST in multiparous (80.5±1.4 U/L) compared with primiparous cows (76.0±1.7 U/L). In conclusion, our results indicate greater risk for primiparous cows to develop subacute ruminal acidosis-like conditions during early lactation than multiparous cows. The study also suggests limited benefits of feeding processed barley grain with La with or without thermal treatment to modulate ruminal tolerance of grain feeding, whereby differing effects in primiparous cows were observed compared with multiparous cows.

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.…”

Effects of meeting the requirements in energy and protein, and of systemic inflammation on the interval from parturition to conception in dairy cows

“…All procedures involving animal handling and treatment were in accordance with national regulations for animal use in research and the national authority approved the study according to §9ff of Law for Animal Experiments (GZ FA10A-78Gu-19/2012). The study was conducted as longitudinal trial, as part of a larger research project (Humer et al 2015;Gruber et al 2017) which involved 30 dairy cows (25 Holsteins and 5 Simmentals; 12 primiparous and 18 multiparous) that were housed in a free stall.…”

“…As protein source, the PMV contained soybean and rapeseed meals. The cows were fed different barleys (Humer et al 2015;Gruber et al 2017), but as these did not affect feed intake and overall intake of nutrients, only the specific energy and nutrient composition of barley and not barley treatment was considered in this study. Detailed information regarding the nutrient composition of all dietary ingredients is provided in Supplementary Table S1 in Supplementary Online Material (SOM).…”

Metabolic adaptation and reticuloruminal pH in periparturient dairy cows experiencing different lipolysis early postpartum

“…Serum samples were stored at −20°C until analyses. Concentrations of serum amyloid A (SAA) and haptoglobin (Hp) were determined by commercially available ELISA bovine kits (Tridelta Development Ltd., Greystones Co. Wicklow, Ireland) according to the methods described previously (Humer et al, 2015b). In brief, serum samples for SAA were initially diluted 1 : 200, and samples with optical density values above the range of the standard curve were diluted further (1 : 400 or 1 : 250) and reanalyzed.…”

“…These wireless pH-transmitting units (3.5 cm i.d., 12 cm long and weighing 210 g), validated previously (Klevenhusen et al, 2014), were manually inserted into the reticulorumen via the esophagus on day 17 postpartum (Humer et al, 2015b). Before their use, the units were calibrated by a two-point calibration using a buffer of pH 4.0 and one of pH 7.0 following the company's instruction protocol.…”