Derek E. Wasson

The objective of this study was to evaluate the effects of individual AA on ruminal fermentation and N utilization in vitro. Four, 24-h batch-culture incubations were conducted with rumen fluid from 3 (2 per incubation run) donor lactating dairy cows as inoculum and a standard TMR (16.5% CP, 30.9% NDF, and 25.5% starch of DM) as the basal substrate. Nitrogen-15 labeled ammonium sulfate (165 mg/L; 15 mg ¹⁵N/L) was used as a tracer to determine microbial ammonia-N incorporation in all treatments. Amino acids were supplemented individually (at 155 mg/L) as follows: His, Leu, Lys, Met, Phe, Trp, Val (EAA1; incubations 1 and 2), and Arg, Asp, Asn, Cys, Glu, Gln, Gly, Ile, Pro, Ser, Thr, and Tyr (EAA2 and NEAA; incubations 3 and 4). Each incubation included treatments with ammonium sulfate (AS; 101 mg/L) as a negative control and hydrolyzed CN (Amicase; 177 mg/L) as a positive control. Incubation medium samples were collected at 24 h and analyzed for VFA and ammonia-N concentrations, as well as NDF degradability. A subset of samples was processed for determination of ¹⁵N enrichment (i.e., atom percent excess) of 3 rumen N pools: solids, bacterial, and ammonia pools, respectively. For statistical analysis, the individual AA treatments were grouped and analyzed by set of incubations: EAA1 (incubations 1 and 2), EAA2 and NEAA (incubations 3 and 4) versus Amicase and AS. Additionally, responses to Amicase and individual AA treatments were compared expressed as the percent difference from AS (negative control). In incubations 3 and 4, compared with AS and EAA2 treatment groups, Amicase and NEAA had a greater total gas production. Total VFA was greatest for Amicase, while the molar proportion of acetate and acetate-to-propionate ratio were lowest and isovalerate was greatest for the EAA1 group. On an individual AA basis and relative to AS (negative control) acetate-to-propionate ratio decreased for Cys, Asp, Tyr, Gln, Met, Asn, Ile, and Thr by 4.5% to 12.5%. Furthermore, the isobutyrate molar proportion increased by 98.2% with Val, whereas Pro increased valerate by 84.1%, and Ile and Leu increased isovalerate by 71.1% and 61.1%, respectively. Nitrogen-15 enrichment of the bacterial-N pool in incubations 1 and 2 was greater for the EAA1 group compared with AS and Amicase, and the incorporation of ammonia-N into bacterial-N was greater for the EAA1 group, and tended to be greater for Amicase, versus AS. Incorporation of ammonia-N into bacterial-N was greater for Leu, Tyr, Met, Ile, Val, Trp, Gly, Phe, His, Pro, Cys, and Arg, ranging from 9.9% to 23%, relative to AS, but the proportion of bacterial-N in solids-N (i.e., a proxy for microbial protein synthesis) was not affected. Overall, supplemental AA (supplied at a dose of 155 mg/L) had minor effects on in vitro fermentation variables and fiber degradability, but supplementation of branched-chain AA and Pro increased molar proportions of their respective branched-chain VFA. Data demonstrated that 9 EAA and 3 NEAA supplemented individually improved the incorporation of ammonia-N into bacterial-N, indicating that some AA can enhance N utilization in the rumen.

A meta-analysis was performed to investigate the effects of capsaicin (CAP) on lactational performance and blood chemistry and cell counts in dairy cattle. The database comprised 11 peer-reviewed studies published between 2011 and 2024. The overall effect of CAP, challenge (e.g., ketosis, glucose tolerance, LPS), and dose were considered explanatory variables in the analysis. Lactation performance response variables included DMI, milk yield (MY), ECM yield, feed efficiency (FE), milk components, and BW. Hematological response variables included red and white blood cell counts and blood BHB, total fatty acids, insulin, and glucose concentrations. Data were analyzed using random- and mixed-effect models in the "robumeta" package in RStudio. Milk yield was increased by 2.9% by CAP when compared with control. Capsaicin supplementation increased FE by 3.4% compared with control. Milk fat concentration and yield were also increased by CAP compared with control by 2.6% and 4.0%, respectively. Blood glucose concentrations were decreased 2.5% by CAP supplementation, whereas insulin levels were unaffected. Cows fed CAP during a challenge had higher MY and FE and tended to have lower blood glucose than their control counterparts. Overall, this analysis suggests that CAP supplementation may be directly affecting host physiology by altering glucose metabolism, but further research to define the mechanism is warranted.

This study investigated the effects of 67 species of macroalgae on methanogenesis and rumen fermentation in vitro. Specimens were analyzed for their effect on ruminal fermentation and microbial community profiles. Incubations were carried out in an automated gas production system for 24-h and macroalgae were tested at 2% (feed dry matter basis) inclusion rate. Methane yield was decreased 99% byAsparagopsis taxiformis(AT) when compared with the control.Colpomenia peregrinaalso decreased methane yield 14% compared with control; no other species influenced methane yield. Total gas production was decreased 14 and 10% by AT andSargassum hornericompared with control, respectively. Total volatile fatty acid (VFA) concentration was decreased between 5 and 8% by 3 macroalgae, whereas AT reduced it by 10%. Molar proportion of acetate was decreased 9% by AT, along with an increase in propionate by 14%.Asparagopsis taxiformisalso increased butyrate and valerate molar proportions by 7 and 24%, respectively, whereas 3 macroalgae species decreased molar proportion of butyrate 3 to 5%.Vertebrata lanosaincreased ammonia concentration, whereas 3 other species decreased it. Inclusion of AT decreased relative abundance ofPrevotella, Bacteroidales, Firmicutes and Methanobacteriaceae,whereasClostridium, AnaerovibrioandMethanobrevibacterwere increased. Specific gene activities forMethanosphaera stadtmaneandMethanobrevibacter ruminantiumwere decreased by AT inclusion. In this in vitro study,Asparagopsis taxiformiswas most effective in decreasing methane concentration and yield, but also decreased total gas production and VFA concentration which indicates overall inhibition of ruminal fermentation. No other macroalgae were identified as potential mitigants of enteric methane.

Botanical extracts have a potential to modify ruminal fermentation while enhancing metabolism and immunity in dairy cows. The objective of this study was to investigate the effects of a combination of Capsicum oleoresin and clove essential oil (botanicals; BTC) on lactational performance, nutrient utilization, enteric methane (CH₄) emissions, and blood parameters in dairy cows. Twenty Holstein cows (12 multiparous and 8 primiparous) averaging (±SD) 77 ± 28 d in milk in the beginning of the study were used in a replicated 4 × 4 Latin square design experiment with 4 periods of 28 d each. Cows were grouped into squares based on parity, milk yield and days in milk, and assigned to 1 of 4 treatments: control (CON), 150, 300, or 600 mg/cow per day of BTC. Cows received the same basal diet and BTC were top-dressed on the total mixed ration once daily. Dry matter intake, milk production, and milk composition were not affected by BTC supplementation, except for milk fat content that tended to be increased in BTC, compared with CON. Daily CH₄ emission (measured using the GreenFeed system) was linearly decreased by up to 7.5% with increasing doses of BTC. Treatment decreased CH₄ yield (kg of CH₄ ÷ kg of DMI) and tended to decrease CH₄ intensity (kg of CH₄ ÷ kg of milk or energy-corrected milk yields) by 5% in BTC, compared with CON. Supplementation of BTC resulted in a quadratic decrease of serum β-hydroxybutyrate in all cows, and a linear decrease of serum insulin concentration in primiparous but not in multiparous cows. Nutrient utilization and other blood parameters (e.g., blood cells count) were not affected by BTC in the current study. The reduction of enteric CH₄ emission demonstrates a moderate mitigation effect on carbon footprint of milk by BTC supplementation. These results must be further investigated and confirmed in longer-term experiments.

Research is increasingly directed towards decreasing the greenhouse gases contribution, specifically methane, from the livestock agriculture sector. Macroalgae supplementation has emerged as a promising tool to mitigate enteric methane emission in ruminants. The mode of action responsible for the mitigation effect centers around the content of volatile halogenated compounds, primarily bromoform. The sub-tropical red seaweed, Asparagopsis taxiformis, is the most well researched bromoform containing species. While several studies, both in vitro and in vivo, have demonstrated the effectiveness of A. taxiformis at reducing enteric methane emission (> 80% reduction), questions surrounding sustainability, animal productivity, animal product quality, and commercial practicality remain. These questions by no means disqualify the practice of feeding macroalgae to cattle to reduce methane emission, but they must be answered before implementing macroalgae as a feed additive commercially. Also, limiting scientific inquiry to a few species reduces the potential of discovering other compounds and modes of action that could produce the desired mitigation effect without the inherit drawbacks of the current options. Work conducted in both ruminant nutrition and human health fields have identified numerous bioactive compounds within plants that exhibit anti-microbial functions that could modify the rumen microbiome for beneficial outcomes. These compounds are also found in macroalgae. Phlorotannins, saponins, sulfonated glycans, other halocarbons and bacteriocins found within macroalgae have demonstrated antimicrobial activity in vitro. However, it is unclear what effect these compounds may have when used in vivo. Once identified, extracting these compounds for supplementation in lieu of feeding the entire plant may be a more practical solution. Dietary inclusion levels of macroalgae in ruminant diets can be limited by variation in active ingredient concentration, palatability to cattle, and excessive dietary mineral content. There are multiple in vitro studies that have demonstrated a methane reduction potential of non-bromoform containing species, but inclusion levels are often well above the effective levels of A. taxiformis (< 0.5% of dietary dry matter). In some animal studies, A. taxiformis supplementation has led to decreased dry matter intake and productivity and elevated mineral accumulation, such as iodine, in animal products. Therefore, methane mitigation by macroalgae will likely have to occur at low dietary concentrations to be practical. This review aims to highlight potential benefits and challenges that feeding macroalgae as a tool for methane reduction may have on animal production, the environment, animal and consumer health.

Intensive research in the past decade has resulted in a better understanding of factors driving enteric methane (CH₄) emissions in ruminants. Meta-analyses of large databases, developed through the GLOBAL NETWORK project, have identified successful strategies for mitigation of CH₄ emissions. Methane inhibitors, alternative electron sinks, vegetable oils and oilseeds, and tanniferous forages are among the recommended strategies for mitigating CH₄ emissions from dairy and beef cattle and small ruminants. These strategies were also effective in decreasing CH₄ emissions yield and intensity. However, a higher inclusion rate of oils may negatively affect feed intake, rumen function, and animal performance, specifically milk components in dairy cows. In the case of nitrates (electron sinks), concerns with animal health may be impeding their adoption in practice, and potential emission trade-offs have to be considered. Tannins and tanniferous forages may have a negative effect on nutrient digestibility, and more research is needed to confirm their effects on overall animal performance in long-term experiments with high-producing animals. A meta-analysis of studies with dairy cows fed the CH₄ inhibitor 3-nitrooxypropanol (3-NOP) at the Pennsylvania State University showed (1) a consistent 28 to 32% decrease in daily CH₄ emissions or emissions yield and intensity; (2) no effect on dry matter intake, milk production, body weight, or body weight change, and a slight increase in milk fat concentration and yield (0.19 percentage units and 90 g/d, respectively); 3-NOP also appears to increase milk urea nitrogen concentration; (3) an exponential decrease in the mitigation effect of the inhibitor with increasing its dose (from 40 to 200 mg/kg of feed dry matter, corresponding to 3-NOP intake of 1 to 4.8 g/cow per day); and (4) a potential decrease in the efficacy of 3-NOP over time, which needs to be further investigated in long-term, full-lactation or multiple-lactation studies. The red macroalga Asparagopsis taxiformis has a strong CH₄ mitigation effect, but studies are needed to determine its feasibility, long-term efficacy, and effects on animal production and health. We concluded that widespread adoption of mitigation strategies with proven effectiveness by the livestock industries will depend on cost, government policies and incentives, and willingness of consumers to pay a higher price for animal products with decreased carbon footprint.