Emerging microalgal feed additives for ruminant production and sustainability

The global demand for animal-derived foods has led to a substantial expansion in ruminant production, which has raised concerns regarding methane emissions. To address these challenges, microalgal species that are nutritionally-rich and contain bioactive compounds in their biomass have been explored as attractive feed additives for ruminant livestock production. In this review, we discuss the different microalgal species used for this purpose in recent studies, and review the effects of microalgal feed supplements on ruminant growth, performance, health, and product quality, as well as their potential contributions in reducing methane emissions. We also examine the potential complexities of adopting microalgae as feed additives in the ruminant industry.

Algae as Feedstuff for Ruminants: A Focus on Single-Cell Species, Opportunistic Use of Algal By-Products and On-Site Production

There is a wide range of algae species originating from a variety of freshwater and saltwater habitats. These organisms form nutritional organic products via photosynthesis from simple inorganic substances such as carbon dioxide. Ruminants can utilize the non-protein nitrogen (N) and the cell walls in algae, along with other constituents such as minerals and vitamins. Over recent decades, awareness around climate change has generated new interest into the potential of algae to suppress enteric methane emissions when consumed by ruminants and their potential to sequester atmospheric carbon dioxide. Despite the clear potential benefits, large-scale algae-livestock feedstuff value chains have not been established due to the high cost of production, processing and transport logistics, shelf-life and stability of bioactive compounds and inconsistent responses by animals under controlled experiments. It is unlikely that algal species will become viable ingredients in extensive grazing systems unless the cost of production and practical systems for the processing, transport and feeding are developed. The algae for use in ruminant nutrition may not necessarily require the same rigorous control during the production and processing as would for human consumption and they could be grown in remote areas or in marine environments, minimizing competition with cropping, whilst still generating high value biomass and capturing important amounts of atmospheric carbon. This review will focus on single-cell algal species and the opportunistic use of algal by-products and on-site production.

Effect of adding Spirulina platensis algae to small ruminant rations on productive, reproductive traits and some blood components

This experiment conducted using 20 Rahmani ewes at the last third of pregnancy in two equal groups. One group served as control, while the other group received Spirulina platensis (SP) at the rate of 0.5 gm 10 kg-1 live body weight. The objective was to find out the effect of adding Spirulina platensis algae to small ruminant rations on reproductive and productive traits and blood components of sheep. The experiments lasted for 120 days for both dams and their lambs after weaning. The findings proved that adding SP in ewes' diets had no effect on the average of live body weight change. Average milk yield was significantly (p <0.01) higher in the treatment group than the control. Lamb's birth weight and daily body gain of the treated group were significantly (p <0.01) higher than the control. Blood and serum picture profile of ewes were significantly higher when fed SP additive than the control. It could be concluded that the addition of SP to the ration of sheep positively preserved their health, productive and reproductive status as well as their lambs' growth rate. Also the additive improved the economic efficiency of treated animals by about 53.13%.

Modulation of rumen bacterial community and feed utilization in camel and sheep using combined supplementation of live yeast and microalgae

The combination of live yeast and microalgae as feed supplementation could improve rumen fermentation and animal productivity. This study aimed to investigate the impact of a mixture of (YA) yeast (Saccharomyces cerevisiae) and microalgae (Spirulina platensis and Chlorella vulgaris) as feed supplementation on feed intake, rumen disappearance of barley straw, bacteria, and fermentation, blood parameters of camels and sheep. Three fistulated camels and three fistulated rams were fed a concentrates mixture and ad libitum barley straw as a basal diet alone or supplemented with YA mixture. The dietary supplementation improved the feed intake, rumen disappearance of barley straw nutrients, and the blood immunity parameters. The YA supplementation affected rumen fermentation as well as the composition and diversity of rumen bacteria; however, the response to the supplementation varied according to animal species. Principle Coordinate Analysis (PCoA) separated bacterial communities based on animal species and feeding treatment. Phylum Bacteroidetes and Firmicutes dominated the bacterial community; and the dominant genera were Prevotella, RC9_gut_group, Butyrivibrio, Ruminococcus, Saccharofermentans, Christensenellaceae_R-7_group, and Succiniclasticum. Our results suggest positive impacts of YA supplementation in rumen fermentation and animal performance.

Review: Alternative and novel feeds for ruminants: nutritive value, product quality and environmental aspects

Ruminant-based food production faces currently multiple challenges such as environmental emissions, climate change and accelerating food-feed-fuel competition for arable land. Therefore, more sustainable feed production is needed together with the exploitation of novel resources. In addition to numerous food industry (milling, sugar, starch, alcohol or plant oil) side streams already in use, new ones such as vegetable and fruit residues are explored, but their conservation is challenging and production often seasonal. In the temperate zones, lipid-rich camelina (Camelina sativa) expeller as an example of oilseed by-products has potential to enrich ruminant milk and meat fat with bioactive trans-11 18:1 and cis-9,trans-11 18:2 fatty acids and mitigate methane emissions. Regardless of the lower methionine content of alternative grain legume protein relative to soya bean meal (Glycine max), the lactation performance or the growth of ruminants fed faba beans (Vicia faba), peas (Pisum sativum) and lupins (Lupinus sp.) are comparable. Wood is the most abundant carbohydrate worldwide, but agroforestry approaches in ruminant nutrition are not common in the temperate areas. Untreated wood is poorly utilised by ruminants because of linkages between cellulose and lignin, but the utilisability can be improved by various processing methods. In the tropics, the leaves of fodder trees and shrubs (e.g. cassava (Manihot esculenta), Leucaena sp., Flemingia sp.) are good protein supplements for ruminants. A food-feed production system integrates the leaves and the by-products of on-farm food production to grass production in ruminant feeding. It can improve animal performance sustainably at smallholder farms. For larger-scale animal production, detoxified jatropha (Jatropha sp.) meal is a noteworthy alternative protein source. Globally, the advantages of single-cell protein (bacteria, yeast, fungi, microalgae) and aquatic biomass (seaweed, duckweed) over land crops are the independence of production from arable land and weather. The chemical composition of these feeds varies widely depending on the species and growth conditions. Microalgae have shown good potential both as lipid (e.g. Schizochytrium sp.) and protein supplements (e.g. Spirulina platensis) for ruminants. To conclude, various novel or underexploited feeds have potential to replace or supplement the traditional crops in ruminant rations. In the short-term, N-fixing grain legumes, oilseeds such as camelina and increased use of food and/or fuel industry by-products have the greatest potential to replace or supplement the traditional crops especially in the temperate zones. In the long-term, microalgae and duckweed of high-yield potential as well as wood industry by-products may become economically competitive feed options worldwide.

Nitrate supplementation has marginal effects on enteric methane production from Bos indicus steers fed Flinders grass (Iseilema spp.) hay, but elevates blood methaemoglobin concentrations

This experiment has quantified the methane abatement potential of nitrate in the context of extensively managed cattle. The experimental protocol consisted of two, 4 × 4 Latin square design using eight rumen fistulated Bos indicus steers fed Flinders grass (Iseilema spp.) hay ad libitum. The treatments were Control (nil nitrogen supplement), urea (32.5 g/day urea) and two levels of calcium nitrate: CaN1 and CaN2 (to provide 4.6 g and 7.9 g NO3/kg DM equivalent to ~0.46% and 0.80% of DM, respectively). Complete supplement intake was ensured by dosing any supplement that had not been voluntarily consumed, through the rumen fistula, 1 h after feeding. Enteric methane production was measured using open circuit respiration chambers. Methane yield (g/kg DM intake) from the CaN2 treatment tended to be lower (P < 0.07) than either the Control or urea treatments. There were no significant differences in methane yield between Control, urea or CaN1 treatments. Mean blood methaemoglobin concentrations were significantly (P < 0.001) higher for CaN2 animals compared with the Control, urea or CaN1 treatments. In addition, a significant time effect after dosing (P < 0.001) and a significant interaction between treatment and time after dosing (P < 0.001) was apparent. Overall mean total volatile fatty acid concentration was 74.0 ± 1.53 mM with no significant treatment effect, but a significant effect for both time of sampling (3 h vs 6 h) within days and among 7 sampling days. The inclusion of calcium nitrate as a non-protein-N source significantly reduced the molar proportions of butyrate (P < 0.001), iso-butyrate (P < 0.05) and iso-valerate (P < 0.001) compared with the Control. The provision of nitrate supplements, providing both a NPN and an alternative sink for H that would otherwise support enteric methanogenesis, has some potential. In extensive grazing systems effective methane abatement strategies are required. The elevated concentration of MetHb using CaN2 suggests that the strategy of replacing urea with nitrate in supplements fed to extensively managed cattle in the northern rangelands may be inappropriate where supplement intake cannot be controlled on an individual animal basis and forage quality is seasonally variable.

Effect of quantity and source of rumen nitrogen on the efficiency of microbial protein synthesis in steers consuming tropical forage

Low values for the efficiency of microbial protein synthesis (EMPS) in cattle consuming tropical forages are related to low rumen degradable crude protein (RDP) intakes. This study examined the effect on the EMPS of the quantity and source of nitrogen (N) supplied to the rumen of eight entire and four rumen-fistulated Brahman steers consuming mature tropical grass hay (57.3 g crude protein/kg DM). Four treatment diets were fed in a Latin square design and included a basal diet of mature pangola grass (Digitaria eriantha) hay (control) and hay plus supplements estimated to provide 150 g RDP/kg digestible organic matter intake (DOMI), as urea or casein, or 300 g RDP/kg DOMI as casein. The EMPS was only increased (P < 0.05) above that for the control diet (167 vs 123 g microbial crude protein (MCP)/kg DOMI) when RDP was provided at the highest rate of 293 g/kg DOMI. This increase was also associated with an ~4-fold increase in the concentration of NH3-N (277 vs 73 mg/L) and of branched-chain volatile fatty acids (44 vs 10 mmol/mol of total volatile fatty acids) in rumen fluid of the steers. However, the source of rumen degradable N (urea or casein) had no effect on the EMPS (109–115 g MCP/kg DOMI) when supplied at ~150 g RDP/kg DOMI. There was no effect of treatment on in vivo neutral detergent fibre digestibility (599 g/kg DM) or the rate (0.037/h) or extent (potential degradable fraction: 636 g/kg OM) of in sacco disappearance of pangola grass hay. In addition, rumen particle dilution rate was unaffected by treatment (0.022/h) and rumen fluid dilution rate, although showing some treatment differences (0.048–0.062/h), was poorly correlated with EMPS. It was concluded that only high amounts of RDP supply to the rumen, in the form of true protein, resulted in increased EMPS whereas at the lower intakes of RDP formulated to achieve EMPS in the range suggested in the feeding standards (130–170 g MCP/kg DOMI) there was no difference in providing the RDP as non-protein N or degradable-protein.

Supplementation of cattle fed tropical grasses with microalgae increases microbial protein production and average daily gain

A series of 3 experiments were conducted to evaluate the use of microalgae as supplements for ruminants consuming low-CP tropical grasses. In Exp. 1, the chemical composition and in vitro protein degradability of 9 algae species and 4 protein supplements were determined. In Exp. 2, rumen function and microbial protein (MCP) production were determined in steers fed speargrass hay alone or supplemented with , , , or cottonseed meal (CSM). In Exp. 3, DMI and ADG were determined in steers fed speargrass hay alone or supplemented with increasing amounts of NPN (urea combined with ammonia sulfate), CSM, or . In Exp. 1, the CP content of and (675 and 580 g/kg DM) was highest among the algae species and higher than the other protein supplements evaluated, and sp. had the highest crude lipid (CL) content (198 g/kg DM). In Exp. 2, supplementation increased speargrass hay intake, the efficiency of MCP production, the fractional outflow rate of digesta from the rumen, the concentration of NHN, and the molar proportion of branched-chain fatty acids in the rumen fluid of steers above all other treatments. acceptance by steers was low and this resulted in no significant difference to unsupplemented steers for all parameters measured for this algae supplement. In Exp. 3, ADG linearly increased with increasing supplementary N intake from both and NPN, with no difference between the 2 supplements. In contrast, ADG quadratically increased with increasing supplementary N intake from CSM. It was concluded that and may potentially be used as protein sources for cattle grazing low-CP pastures.

Efficiency of rumen microbial protein synthesis in cattle grazing tropical pastures as estimated by a novel technique

The efficiency of microbial protein synthesis (EMPS) in cattle grazing a range of tropical pasture types was examined using a new method of intra-jugular infusion of chromium–EDTA to estimate urinary excretion of purine derivatives. Seven pasture types were studied in south-eastern Queensland, Australia, over a 13-month period. These included native tropical grass (C4) pasture (major species Heteropogon contortus and Bothriochloa bladhii) studied in the early wet, the wet–dry transition and the dry season; introduced tropical grass (C4) pasture (Bothriochloa insculpta) in the mid-wet season; two introduced tropical legume species (C3; Lablab purpureus and Clitoria ternatea); and the temperate-grass (C3) pasture, ryegrass (Lolium multiflorum). There was a large range in EMPS across pasture types, with a range of 26–209 g microbial crude protein per kilogram digestible organic matter intake (DOMI). Estimated rumen-degradable protein (RDP) supply (42–525 g/kg DOMI) was the major factor associated with EMPS across the range of pasture types studied. EMPS in steers grazing all tropical grass pastures was low (&lt;130 g/kg DOMI) and limited by RDP supply. Negative linear relationships (P &lt; 0.05) between EMPS and concentrations of both neutral detergent fibre and acid detergent fibre in extrusa were evident. However, non-fibre carbohydrate in extrusa, total non-structural carbohydrate concentration in plucked pasture leaf, rumen fluid and particle dilution rate, protozoal concentration in rumen fluid and rumen fluid pH were not correlated with EMPS. It was concluded that EMPS was well below 130 g microbial crude protein per kilogram DOMI when cattle grazed unfertilised, tropical grass pastures in south-eastern Queensland and that RDP was the primary limiting nutrient. High EMPS was associated with a very high RDP, vastly in excess of RDP requirements by microbes.

Effect of feeding forage characteristic of wet- or dry-season tropical C4 grass in northern Australia, on methane production, intake and rumen outflow rates in Bos indicus steers

Methane production (MP) from Bos indicus steers fed Chloris gayana hay characteristic of the ‘dry season’ (LQH), and a fresh Urochloa mosambicensis grass (PAS) or a C. gayana hay (HQH) characteristic of the ‘wet’ season was determined. A longitudinal feeding trial incorporated a 42-day covariate period (P1) in which Brahman steers (total n = 12) were fed ad libitum LQH (g/kg DM: crude protein (CP) 25; acid detergent fibre expressed exclusive of residual ash (ADFom) 487; DM digestibility (DMD) 380) followed by a 42-day treatment period where steers (n = 4 in each) were randomly assigned to PAS, HQH or remained on LQH (control). The diet composition in P2 was HQH (g/kg DM: CP 88; ADFom 376; DMD 590), PAS (g/kg DM: CP 90; ADFom 324; DMD 630) and LQH (g/kg DM: CP 31; ADFom 461; DMD 410). For each period, on Days 35–41, individual dry-matter intakes (DMI), rumen fermentation parameters and both fluid and particulate fractional rumen outflow rates were measured. On Days 41 and 42, MP was determined using open-circuit respiration chambers. There were diet effects on MP, DMI, volatile fatty acids, and ammonia-N. Both PAS- and HQH-fed steers had greater MP (g/day; P < 0.05) and DMI (P < 0.05) than did those fed LQH, but a lower MP per kilogram DMI digested. The use of predictive equations compared with measured data confirmed prior observations that MP from tropical grasses in the northern Australian rangelands may be overestimated using the current equations for greenhouse gas accounting.