Supplementation of Ascophyllum nodosum meal and monensin: Effects on diversity and relative abundance of ruminal bacterial taxa and the metabolism of iodine and arsenic in lactating dairy cows

Abstract

Previous research has shown that the brown seaweed Ascophyllum nodosum (ASCO) has antimicrobial and antioxidant properties and also increases milk I concentration. We aimed to investigate the effects of supplementing ASCO meal or monensin (MON) on ruminal fermentation, diversity and relative abundance of ruminal bacterial taxa, metabolism of I and As, and blood concentrations of thyroid hormones, antioxidant enzymes, and cortisol in lactating dairy cows. Five multiparous ruminally cannulated Jersey cows averaging (mean ± standard deviation) 102 ± 15 d in milk and 450 ± 33 kg of body weight at the beginning of the study were used in a Latin square design with 28-d periods (21 d for diet adaptation and 7 d for data and sample collection). Cows were fed ad libitum a basal diet containing (dry matter basis) 65% forage as haylage and corn silage and 35% concentrate and were randomly assigned to 1 of the following 5 dietary treatments: 0, 57, 113, or 170 g/d of ASCO meal, or 300 mg/d of MON. Supplements were placed directly into the rumen once daily after the morning feeding. Diets had no effect on ruminal pH and NH 3 -N concentration, which averaged 6.02 and 6.86 mg/ dL, respectively. Total volatile fatty acid concentration decreased linearly in cows fed incremental amounts of ASCO meal. Supplementation with ASCO meal did not change the ruminal molar proportions of volatile fatty acids apart from butyrate, which responded quadratically with the lowest values observed at 56 and 113 g/d of ASCO supplementation. Compared with the control diet or diets containing ASCO meal, cows fed MON showed greater molar proportion of propionate. Diets did not affect the α diversity indices Shannon, Simpson, and Fisher for ruminal bacteria. However, feeding incremental levels of ASCO meal linearly decreased the relative abundance of Tenericutes in ruminal fluid. Monensin increased the relative abundance of the CAG: 352 bacterial genus in ruminal fluid compared with the control diet. Linear increases in response to ASCO meal supplementation were observed for the concentrations and output of I in serum, milk, urine, and feces. Fecal excretion of As increased linearly in cows fed varying amounts of ASCO meal, but ASCO did not affect the concentration and secretion of As in milk. The plasma activities of the antioxidant enzymes and the serum concentrations of thyroid hormones did not change. In contrast, circulating cortisol decreased linearly in diets containing ASCO meal. The apparent total-tract digestibilities of dry matter, organic matter, and crude protein increased linearly with ASCO meal, but those of neutral and acid detergent fiber were not affected. In summary, feeding incremental amounts of ASCO meal decreased serum cortisol concentration, and increased I concentrations and output in serum, milk, feces, and urine.

Feeding incremental amounts of ground flaxseed: effects on diversity and relative abundance of ruminal microbiota and enteric methane emissions in lactating dairy cows

“…Samples were then filtered through 4 layers of cheesecloth into volumetric flasks to a final volume of 250 mL and preserved on dry ice until transported to the laboratory. Next, aliquots of 0.6 mL of ruminal fluid from each day were pooled per cow into 2-mL cryovials (1.8 mL total) and stored at −80 °C until shipped in dry ice to MR DNA Laboratory (Shallowater, TX) for DNA extraction and MiSeq sequencing as reported in detail by Silva et al (2022) . In brief, microbial DNA (prokaryotes) was extracted from ruminal fluid samples using the PowerSoil DNA isolation method (kit #12888–100; MO BIO Laboratories Inc., Carlsbad, CA) and quantified via spectrophotometry (2000 UV-VIS, NanoDrop spectrophotometer; Thermo Fischer Scientific, Waltham, MA).…”

“…Amplification of the V4 variable region of 16S rRNA genes was carried out with the primer pairs 515F (5ʹ- GTGCCAGCMGCCGCGGTAA) and 806R (5ʹ-GGACTACHVHHHTWTCTAAT) as reported previously ( Caporaso et al, 2012 ). The HotStarTaq Plus Master Mix DNA polymerase kit (QIAGEN, Hilden, Germany) was used for PCR amplifications following conditions and elongation steps shown in Silva et al (2022) . Purified PCR products were utilized to prepare a sequencing library following the Illumina TruSeq (Illumina Inc., San Diego, CA) protocol, with sequencing analysis performed on a MiSeq (Illumina Inc.) following the manufacturer’s guidelines.…”

“…Diversity of ruminal microbiota (prokaryotes) in response to diets was evaluated using the α-diversity indices OTU, Shannon, and Faith. The β-diversity principal coordinate analysis ( PCoA ) was performed using the Bray–Curtis method for unweighted (qualitative) UniFrac distances for each treatment as detailed in Silva et al (2022) .…”

Maine organic dairy producers’ receptiveness to seaweed supplementation and effect of Chondrus crispus on enteric methane emissions in lactating cows

“…According to the European Food Safety Authority (33), milk iodine concentrations should remain below 500 μg/L to minimize toxicity risks. However, as recently summarized by Brito (34), milk iodine concentrations above the 500-μg/L threshold have been reported in response to dietary supplementation of A. nodosum (12,27), A. taxiformis (2), and C. crispus (35) to dairy cows. Consequently, it is imperative to develop technologies that enable dairy producers to feed safe and predictable algal-based feeds to decrease the risk of excess iodine intake by cows and humans.…”

“…Iodine concentration is typically greater in brown versus red seaweeds (26). However, lower iodine values were reported for A. nodosum [mean = 654 ± 212 mg/kg of DM (12,16,27)] relative to A. taxiformis [2,270 mg/kg of DM (8)]. This discrepancy may be attributed to intrinsic species differences, effects of seasonality, geographical location, and harvesting and processing methods (28).…”