Fungal feed additives offer a potential avenue to enhance dairy cattle health and productivity. This narrative review examines and consolidates literature investigating the effects of products containing, or derived from, anaerobic fungi (AF), obligately aerobic filamentous fungi and yeasts. There is a sparsity of research investigating supplemental AF in cattle, but existing literature demonstrates that AF can consistently increase the digestibility of feeds. Anaerobic fungal additives are limited by their oxygen vulnerability, although characterization of the resting stage of their lifecycle would aid in the development of products which could be used on farm. The majority of research investigating aerobic fungi in dairy cattle is based upon their fermentation products. These products often enhance digestibility variables in cattle, which sometimes benefits growth and production. Inconsistent responses, which are attributed to heterogenous product composition and rumen stability, hinder the industry utility of these additives, and further research is required to define the conditions required for efficacy. A large body of research exists examining the effects of active yeast and yeast derivatives in mature cattle and calves. In-depth examination of this research is beyond the scope of this review, but substantial evidence suggests that supplementing dairy cattle with yeast can be advantageous for gut health and development, production and stress tolerance. This review highlights the pathways through which exogenous fungi can enhance dairy production, and that further research is required to define the causes of inconsistent responses from treatments. This will increase the value of fungal additives to the dairy sector.

This Research Communication addresses the hypothesis that calf faeces can be used as a microbial inoculum in the in vitro gas production (GP) technique to model rumen digestibility in calves. In vitro GP is a valuable method of screening dietary interventions in ruminants. However, the technique requires a microbial inoculum, typically obtained from the rumens of fistulated animals. Using faecal inocula that can be collected non-invasively would be ethically and economically preferable, if it provided equivalent results. The aim of this pilot study was to compare in vitro GP from faecal and ruminal inocula obtained from dairy calves that were killed either pre-weaning or post-weaning. Ruminal content and faeces were collected from calves aged 4, 7 and 13 weeks old, and incubated with calf starter concentrates in the ANKOMRF system. A weak relationship between inocula was seen for all modelled GP kinetic parameters (R2 < 0.53), although modelling indicated that incubations using faecal and rumen inocula from pre-weaned calves had similar lag times and rates of degradation. In weaned calves, aged 13 weeks, faecal incubations produced less gas, lag times were longer, and the rate of degradation of the slowly degradable fraction of calf starter was slower, compared to rumen incubations. Weak relationships, and kinetic differences, between rumen and faecal inocula would likely hinder the use of faeces to model calf rumen fermentation.

This Research Paper tested the hypothesis that the dietary inclusion of a fermentation product of Aspergillus niger (ANP), alone, or in combination with a mannan-rich fraction (MRF) derived from Saccharomyces cerevisiae cell wall, would enhance dairy calf performance and rumen variables. Thirty Holstein-Friesian bull calves (age 19 ± 5 days) were obtained from a single farm and randomly assigned according to days of age to one of three dietary treatment groups and one of two cull dates, experimental day 27 (immediately prior to weaning) or experimental day 70. Dietary treatment groups were: CTRL, no treatment; ANP, 3 g/day ANP; MRF, 3 g/day ANP and 2 g/day MRF. Calves were housed and fed individually and had ad libitum access to starter concentrates, water, and straw. Throughout the trial, ANP calves consumed a greater quantity of solid starter feed than CTRL and MRF calves. Body weight, average daily gain, apparent total tract dry matter digestibility and faecal scores were unaffected by treatment. Calves fed ANP and MRF had improved feed conversion efficiency compared with CTRL in some weeks, but this was not consistent throughout the pre-weaned and weaned periods. Calves fed MRF had a decreased acetate to propionate ratio compared with CTRL pre-weaning, and ANP had a lower acetate to propionate ratio and higher propionate proportion of total VFA compared with CTRL post-weaning. At both culling timepoints, ANP and MRF had thicker stratum basale, stratum spinosum and stratum granulosum in their rumen papillae compared with CTRL. The inclusion of ANP and ANP + MRF could favourably alter rumen fermentation and increase the metabolic and absorptive capacity of papillae in transition stage dairy calves but no consistent effects of treatment on calf growth or feed efficiency were observed in this trial.

The early-life rumen microbiome is highly dynamic, shaped by dietary transitions and maternal influences. Several dietary additives have been studied during the pre- and post-weaning periods to improve animal welfare, growth performance, and farming efficiencies. This study investigated microbial community assembly and growth performance of lambs provided with a mannan-rich fraction (MRF) supplement, either through maternal supplementation, directly, or via a combination of both. Using metagenomic sequencing and gas chromatography, we found differences in rumen microbial alpha and beta diversity related to both sampling time point and MRF supplementation (p < 0.05). At week 8, lamb microbiomes showed greater variance in their Shannon alpha diversity, with direct MRF supplementation only to the lamb resulting in a significantly greater diversity (p < 0.05). At week 20, combined maternal and lamb supplementation resulted in the highest Shannon diversity and was different compared to all other groups (p < 0.05). Beta diversity analyses combined with differential abundance analyses revealed that microbial community structures are driven by both diet and time, with maternal MRF supplementation associated with enrichment of taxa involved in carbohydrate fermentation and succinate metabolism, including Succiniclasticum ruminis, Succinovibrio dextrinosolvens, and Fibrobacter succinogenes. Generalized linear modeling identified significant associations between microbial alpha diversity metrics and total volatile fatty acids in lambs, particularly butyrate and valerate. Furthermore, at week 8, there was a significant positive correlation between alpha diversity metrics and propionate and valerate. In this study, lambs receiving MRF through maternal and direct supplementation had the highest growth performance, measured as the median average daily gains (kg) and final weights (kg) of lambs. These findings suggest that MRF supplementation, especially when provided both maternally and directly, may influence the lamb rumen microbiome and alter its metabolic potential with potential implications for optimizing early-life nutrition strategies in ruminant production systems.

The aim of this review is to quantify the strength of evidence for the efficacy of exogenous enzymes (EE) in dairy calf rearing, by systematically identifying, consolidating and discussing existing research on the subject. This review identified 17 articles that measured the effect of EE alone or in combination with another treatment on indicator variables for calf performance, behaviour, health or environmental output; 15 studies realised a positive effect of enzyme supplementation on at least one variable, and one study realised a negative effect of treatment on body parameters. Inconsistent results were noted for effects of EE on growth and feed efficiency. Studies that combined EE with another treatment, did not tend to find performance improvements compared to stand-alone treatments. However, several studies were underpowered which could have limited their ability to detect effects on primary response variables. All papers that measured digestibility found an increase in fibre digestibility from enzyme treatment; however, this did not always result in improved feed efficiency or growth. Reductions in non-nutritive oral behaviour, increased resting time and rumination, were observed in studies measuring calf behaviour, as were enhanced rumen development and reduced cost of calf rearing; suggesting that EE could enhance calf health and welfare, whilst having additional advantages for rearing economics. Future research into the efficacy of EE in dairy calves is worth pursuing. However, a targeted and evidence-based approach to experimental design is required, with due consideration given to enzyme actions and interactions, as well as robust power analysis for sample size.

This Research Paper addresses the hypothesis that the dietary inclusion of an Aspergillus niger fermentation product will alter the degradation kinetics and rumen fermentation patterns of feeds in dairy cattle. Fungal fermentation products often contain a suite of bioactive compounds and secondary metabolites, which can influence the microbial environment in the rumen and act as digestibility enhancers. As the cattle sector is under increasing pressure to enhance its sustainability, the investigation of dietary interventions that could improve the efficiency of production is warranted. In a previous experiment, Synergen®, a product of the solid-state fermentation of Aspergillus niger (ANP) containing residual enzyme activities, significantly increased the in vitro digestibility of a grass silage-based dairy total mixed ration (TMR), suggesting that in vivo studies would be valuable. Hence the present study aimed to quantify the effects of this ANP on rumen fermentation measures in cattle. Using a 4 × 4 Latin square design, the effect of four doses of ANP (0, 5, 10, 15 g/day) in four cannulated Jersey heifers was measured on the in sacco degradation of dry matter (DM), organic matter, crude protein and neutral detergent fibre in steam-flaked barley, grass silage and a grass silage-based TMR formulated for dairy cattle. Treatments had no significant effect on the rate, or extent, of degradation of any component in any feed investigated. Rumen volatile fatty acid concentrations and proportions, and rumen pH, were quantified at seven timepoints during each 48-h sampling period and were unaffected by treatment, as was the apparent total tract digestibility of DM. Under the conditions of this trial, ANP did not influence rumen fermentation kinetics; indicating that supplementing mature, non-lactating Jersey cattle with this fungal fermentation product is not an advantageous strategy to enhance feed digestibility.

Dairy cows lameness represents a significant welfare issue for the dairy industry. The aim of this study was to investigate metabolic and hormonal parameters associated with lameness in cows. The study included two treatment groups of 10 multiparous Holstein–Friesian dairy cows each. The control group consisted of cows with locomotion score 1 and in the experimental group cows with locomotion scores 3 and 4 were included. Milk, urine and blood samples were collected to determine the fat, protein, urea, creatinine, electrolytes and copeptin vasopressin (AVP) content. The milk fat, protein and energy-corrected milk (ECM) levels were higher in lame animals compared with non-lame cows. The blood urea nitrogen (BUN) and BUN/serum creatinine ratio were lower at the start of the trial in lame animals suggesting a metabolic acidosis state. There were significantly lower serum Na levels in the lame cows, from the start until the end of the trial (p < 0.011), as well as between lame and non-lame groups at the end of the trial (p = 0.041). A lower copeptin AVP was detected in lame compared with non-lame cows at the end of the trial (p = 0.004). The decrease of serum Na levels as the comfort improves indicates that the animals started to recover from the effect of cortisol on mineralocorticoid receptors. Our data also indicates that the BUN and BUN/serum creatinine ratios are associated with lameness. Further investigations involving a larger number of cows would be recommended to confirm these results and to evaluate these parameters in the early stages of lameness.

This study addresses the effect of using animal excreta on the nutritional content of forages, focusing on macro- and micro-element concentrations (nitrogen; N, phosphorus; P, sulphur; S, copper; Cu, zinc; Zn, manganese; Mn, selenium; Se) from animal feed to excreta, soil, and plants. Data were collected from pot and field trials using separate applications of sheep or cattle urine and faeces. Key findings indicate that soil organic carbon (SOC) and the type of excreta significantly influences nutrient uptake by forages, with varied responses among the seven elements defined above. Although urine contributes fewer micronutrients compared to faeces (as applied at a natural volume/mass basis, respectively), it notably improves forage yield and micronutrient accumulation, thus potentially delivering positive consequences at the farm level regarding economic performance and soil fertility when swards upon clayey soil types receive said urine in temperate agro-climatic regions (i.e., South West England in the current context). In contrast, faeces application in isolation hinders Se and Mn uptake, once again potentially delivering unintended consequences such as micronutrient deficiencies in areas of high faeces deposition. As it is unlikely that (b)ovine grazing fields will receive either urine or faeces in isolation, we also explored combined applications of both excreta types which demonstrates synergistic effects on N, Cu, and Zn uptake, with either synergistic or dilution effects being observed for P and S, depending largely on SOC levels. Additionally, interactions between excreta types can result in dilution or antagonistic effects on Mn and Se uptake. Notably, high SOC combined with faeces reduces Mn and Se in forages, raising concerns for grazed ruminant systems under certain biotic situations, e.g., due to insufficient soil Se levels typically observed in UK pastures for livestock growth. These findings underscore the importance of considering SOC and excreta nutritional composition when designing forage management to optimize nutrient uptake. It should be noted that these findings have potential ramifications for broader studies of sustainable agriculture through system-scale analyses, as the granularity of results reported herein elucidate gaps in knowledge which could affect, both positively and negatively, the interpretation of model-based environmental impact assessments of cattle and sheep production (e.g., in the case of increased yields [beneficial] or the requirement of additional synthetic supplementation [detrimental]).

Abstract High yielding dairy cattle are typically fed a total mixed ration (TMR) to meet their energy requirements. However, inadequate mixing can lead to feed selection and dietary imbalance, negatively affecting rumen metabolism and the microbiome. To investigate the effect of TMR mixing, four dairy cows were fed a partial mixed ration with dietary concentrates (4 kg/cow/day) added separately in even and uneven patterns of allocation (CA) with a Saccharomyces cerevisiae yeast supplement (YS) (1 g/cow/day). Rumen digesta samples were taken to measure microbial metabolism and microbiome using16S rRNA amplicon sequencing. No effect of CA on rumen metabolism was detected. YS inclusion tended to increase rumen pH ( P = 0.088) reduce total VFA concentration ( P = 0.033) and propionate concentration ( P = 0.016). Clustering of the rumen microbiome was observed with YS supplementation, driven by a decrease in abundance of Gammaproteobacteria and Prevotellaceae OTUs respectively and an increase of a Christensenellaceae OTU. Pattern of concentrate allocation had no detectable effect on alpha diversity or Bray Curtis dissimilarity. However, reduction in relative abundance of a Prevotellaceae OTU biomarker was associated with uneven pattern of concentrate allocation . Pattern of concentrate allocation and YS supplementation did not adversely affect milk yield or composition.

Nitrogen (N) loss from livestock agriculture via ammonia and nitrous oxide can reduce feed efficiency, production and negatively affect the environment. One option to reduce N loss is to add dietary supplements such as Yucca schidigera extract which has ammonia-binding properties and contains antimicrobial steroidal saponins, or Saccharomyces cerevisiae yeast, which can stabilise rumen pH and promote fibre degradation, increasing microbial growth and demand for degradable N. To determine the effect of Yucca schidigera extract when fed alone or in combination with a live yeast on the performance, rumen metabolism, microbiome and N balance, six rumen cannulated dairy cows were fed a mixed ration (C), mixed ration with Y. schidigera extract (De-Odorase®, Alltech®; 5 g/cow/day; D), or mixed ration with Y. schidigera extract (5 g/day) and Saccharomyces cerevisiae (Yea-Sacc®, Alltech®, 1 g/cow per day; DY), in a 3 × 3 Latin rectangle design study with three periods of 49-day duration. Digesta samples were collected via the ruminal cannula during the final week of each period and separated into liquid (LPD) and solid (SPD) phases for microbiome analysis using 16S rRNA amplicon sequencing. DM intake was 0.8 kg/d lower (P < 0.05) in cows fed DY than C or D, with milk protein concentration 1.7 g/kg higher in C than D or DY. There was a beta diversity (Bray Curtis) clustering of the LPD in cows fed D or DY compared to C (P < 0.05), driven by an increase in Prevotella ruminicola-related operational taxonomic units (OTUs), and a decrease in P. brevis and P. bryantii OTUs. A methanogen OTU, Methanobrevibacter olleyae, was decreased in cows fed D or DY and an unclassified species of Gammaproteobacteria was increased in DY (LDA > 2.0, P < 0.05) compared to C. Rumen pH, ammonia and total VFA concentration were not affected by treatment (P > 0.05) but the concentration of propionate and iso-butyrate were lower at 1700 and 2000 h in cows fed DY compared to C (P < 0.05). Measurements of N balance were unaffected by supplementation with D or DY, and there was no effect of treatment on slurry pH. In conclusion, supplementing with an extract of Yucca schidigera either alone or in combination with a live yeast had only a small effect on performance, with Yucca schidigera altering species associated with carbohydrate and protein metabolism, and reduced Methanobrevibacter olleyae which is involved in methanogenesis.

Background and aims The intake of selenium, an essential element for animals and humans, in ruminants is largely determined by selenium concentration in ingested forages, which take up selenium mainly from soil. Ruminant excreta is a common source of organic fertilizer, which provides both nutrients and organic matter. This study aims to unentangle the unclear effect of applying different types of ruminant excreta in soils of different organic matter contents on selenium uptake by forage. Methods Perennial ryegrass (Lolium perenne) was grown in soils of different organic matter contents. Urine and/or feces collected from sheep fed with organic or inorganic mineral supplements, including selenium, were applied to the soils. The selenium in the collected samples were analyzed using ICP-MS. The associated biogeochemical reactions were scrutinized by wet chemistry. Results The application of urine and/or feces resulted in either the same or lower selenium concentrations in perennial ryegrass. The excreta type did not affect total selenium accumulation in grass grown in low organic matter soil, whereas in high organic matter soil, feces resulted in significantly lower total selenium accumulation than urine, which was attributed to a possible interaction of selenium sorption in soil and microbial reduction of Se. Conclusion This one-time excreta application did not increase, but further decrease in some treatments, selenium concentration and accumulation in the perennial ryegrass. Consequently, to increase ruminant selenium intake, supplementing selenium directly to animals is more recommended than applying animal manure to soil, which might drive selenium reduction and decrease selenium uptake by grass.

The form (organic versus inorganic) of minerals (Se, Zn, Cu and Mn), supplemented to sheep (Charolais × Suffolk-Mule (mean weight = 57 ± 2.9 kg) at two European industrial doses, on the return of micronutrients to pasture via nutrient partitioning and composition in sheep urine and faeces was investigated. This gave four treatments in total with 6 animals per treatment (n = 24). The form of the supplemented minerals did not influence the excretory partitioning of micronutrients (Se, Zn, Cu and Mn) between urine and faeces, nor on their concentrations in the excreta. The two doses trialed however, may influence the Se flux in the environment through altering the ratios of Se:P and Se:S ratios in the faeces and Se:S ratio in the urine. Administration of the mineral supplements also improved the retention of P in sheep reducing its excretion via urine. Although the concentrations of readily bioavailable micronutrients in the faeces were not affected by the mineral forms, there were differences in the more recalcitrant fractions of Se, Zn and Cu (as inferred via a sequential extraction) in faeces when different forms of supplemental minerals were offered. The potential impact of these differences on micronutrient flux in pasture requires further investigation.

This study investigated the effect of compaction, aeration and addition of a naturally mycotoxin contaminated ryegrass silage (MCS) containing 1803 µg/kg DM penicillic acid, on the nutritional value and mycotoxin content after ensiling and subsequent aerobic stability of ryegrass Lolium perenne silage (second-cut, June 2020, UK). Mini silos (30 L) were filled with differential compaction (500 kg FW/m 3 and 333 kg FW/m 3 ), aeration by injection of air (1L per 48h for 30d then 1L per 7d) and addition of MCS (1.5 g/kg FW ensiled forage) in a 2×2×2 factorial design. During ensilage, mean CO 2 % (kg FW) in the aerated silos increased with low compaction. Crude protein (CP) increased and ash decreased with aeration. Mean silage fermentation end products acetic (AA), lactic (LA) and propionic acid (PA) concentrations increased with MCS. PA concentration increased with aeration/low compaction. LA decreased and ethanol increased with low compaction. Mycotoxin profiles differed between the silages on opening and after 14-days incubation in aerobic conditions with disappearance of fusarenon X and penicillic acid and appearance of mycophenolic acid and roquefortine C (318 µg/kg DM and 890 µg/kg DM). Addition of MCS, increased the concentration of penicillic acid on opening with an interaction with aeration (80.6µg/kg DM MCS × aerated, 40.0 µg/kg DM in the MCS × sealed). Aerobic stability was affected by aeration and low compaction with reduced time taken to heat to +5°C and +10°C above ambient temperature, higher rate of increase in pH and higher cumulative temperatures to the first peak temperature. Higher mycotoxin concentration at opening had a similar effect increasing time to heat +5°C and +10°C above ambient temperatures in aerobic conditions. Regression analysis showed predominantly direct relationships between silage fermentation end-product concentrations and aerobic stability. This study revealed interactions between silage bacteria and fungi activity from the concentrations of fermentation end-products and mycotoxins during ensilage and subsequent aerobic spoilage. The results supported current best practice for silage making, promoting conditions for improved preservation and aerobic stability. The addition of MCS had unexpected positive effects. However, factors associated with the MCS benefiting aerobic stability were not determined.

The aim of the study was to investigate the impact of lameness on nitrogen (N) metabolism and excretion. Two treatment groups of 20 multiparous Holstein–Friesian dairy cows were included in study; the control group consisted of cows with locomotion score ≤2, while the experimental group consisted of cows with locomotion scores 3 and 4. Fodder, milk, feces, and urine were collected to determine nitrogen emissions. The milk yield, the energy-corrected milk, the fat and protein yield were higher for lame animals compare with non-lame cows. Differences were also detected in the milk urea nitrogen (MUN) between groups where lame cows had a 15% lower MUN than non-lame animals. Urine volume was lower (p < 0.008), while urinary creatinine concentration was higher (p < 0.05) in lame animals compare with those in the non-lame group. Consequently, the creatinine/urea ratio was significantly higher (p < 0.001) in the lame vs. no-lame animals. Nitrogen excretion in milk was higher (p = 0.008) and N in urine was lower (p < 0.001) in the lame compared to non-lame cows with lower urinary N emissions in lame animals. Taken together, our results show that urinary creatinine concentration and urinary creatinine/urea ratio have the potential to be used as a tool for lameness detection.