Guidelines for small ruminant production systems under climate emergency in Europe

1 Guidelines for small ruminant production systems under climate emergency in Europe G. Pardoa, A. del Pradoa aBasque Centre for Climate Change (BC3), Edificio Sede Nº 1, Planta 1ª, Parque Científico de UPV/EHU, Barrio Sarriena s/n, 48940 Leioa (Bizkaia) Corresponding author: Agustin del Prado. Email: [email protected] Short title: Small ruminants under climate change in Europe Abstract Projected climate change will involve an additional threat for the sustainability of small ruminant production systems in Europe. Aiming to understand its implications, we conducted a literature review on climate change interactions with sheep and goat systems. The review first identifies the main potential impacts on productivity at the animal level (heat stress effects) and at the forage level (quantity and quality). Results from analysed studies suggest that heat stress thresholds for small ruminants could be higher than previously indicated, although they still will be affected during projected heatwaves. At the forage level, the potential positive effect of CO2 fertilization will probably be counteracted in most of the cases due to extreme weather events and other limitations. Based on that findings, the review analyses the most suitable adaptation strategies on animal heat stress and pasture production. Particular attention is paid to integrated approaches, providing co-benefits at This document is the Accepted Manuscript version of a Published Work that appeared in final form in: G.Pardo, A. del Prado 2020. Guidelines for small ruminant production systems under climate emergency in. SMALL RUMINANT RESEARCH. 193. DOI (10.1016/j.smallrumres.2020.106261). © 2020 Elsevier B.V. This manuscript version is made available under the CC-BY-NC-ND 3.0 license http://creativecommons.org/licenses/by-nc-nd/3.0/ 2 different levels. Finally, structural and practical challenges affecting small ruminants’ sustainability in a climate change context are discussed, together with potential synergies and trade-offs among different policies and/or strategies. According to the information reviewed, small ruminant systems could be particularly vulnerable to environmental changes, as they are often produced in harsh areas under already severe circumstances. At the same time, they have particular features that could involve advantages against other livestock systems to cope with –and fight againstfuture climatic conditions. Consequently, they should play a important role for the climate change adaptation and mitigation options within the livestock sector. Keywords: global warming; sheep; goats; climate change Introduction Future climate projections for Europe indicate a general warming trend and more variable patterns of precipitation, with an increase in frequency and length of dry periods and droughts (Jacob et al., 2014). Consequently, other abiotic variables will also be influenced, including increased likelihood and intensity of fires and floods and alteration of nutrient cycles. Such changes will inevitably affect livestock production, both the animals directly and the production system more widely. In this context, small ruminant systems are subject to specific challenges regarding their future. On one hand, they could be particularly vulnerable to environmental changes, as a large share of the production is held in marginal lands and/or semiarid conditions. Yet on the other hand, small ruminants have features (e.g. weather 3 resistance, grazing/browsing abilities) that can involve competitive advantages and opportunities against other livestock species in the face of a changing climate. Aiming to understand the potential influence of climate change (CC) in small ruminant farming in Europe, we here conduct an analysis of information available on CC interactions and weather effects on sheep and goat systems, involving direct impacts on animal productivity mainly, but also indirectly, via feed resources availability and disease occurrence. Other important aspects, e.g. welfare, although superficially mentioned, are beyond the scope of this study. The main objective of this study is to estimate the general expected impacts of CC in the sheep and goat systems, but also to provide guidelines about how the sector could adapt to –or exploitthem. Accordingly, a set of guidelines including main CC adaptation strategies, but also synergies with CC mitigation, are discussed, both at practical and strategic level (i.e. policy), so the future role of European small ruminants in the context of CC can be adequately considered. Climate change effects on small ruminant systems: animal and fodder level Animal level Heat stress In addition to warming trends, future climate scenarios predict an increase in the frequency and duration of heat waves in Europe (Jacob et al., 2014), particularly in south-central regions. As a consequence, heat stress (HS) will be one of the most important factors affecting sheep and goat production. The general responses to HS in small ruminants include a number of metabolic, physiological and behavioural changes, such as raised respiration rate and rectal temperature, sweating, panting, increase drinking and reduction of feed intake (Marai 4 et al., 2007). Nevertheless, sheep and goats are considered less susceptible to HS than other domesticated species (Lu, 1989), which could provide them a competitive advantage under future CC scenarios. The literature describes thermoneutral zone (TNZ) for sheep between 12ºC and 25ºC. A higher HS threshold (28-30ºC) can be expected for goats, due to specific adaptation mechanisms (Lu, 1989; Al-Dawood, 2017). Still, these ranges are often exceeded during heat waves in Europe, and that situation will become more frequent in the future. The risk of HS is often estimated by the temperature-humidity index (THI), which accounts for the combined effects of ambient temperature and relative humidity (RH). Based on this index, the following thresholds have been proposed for small ruminants (THI<22.2=absence of HS; 22.2 to <23.3 = mild HS; 23.3 to <25.6 = moderate HS; >25.6 severe HS) (Marai et al., 2007). In the present work, a revision of literature involving small ruminants and HS has been conducted. Detailed methodology is described in the Supplementary Material S1. First, we selected studies monitoring ambient conditions and animal-based indicators related to signs of HS, namely respiration rate and rectal temperature. THI was applied as an indicator for the degree of HS caused by weather conditions. The formula proposed by Marai et al 2007 was used: THI = db ◦C −{(0.31 − 0.31 RH)(db ◦C − 14.4)} where db ◦C is the dry bulb temperature (◦C) and RH is the relative humidity (RH%)/100. Relationship of both parameters, respiration rate and rectal temperature, with THI followed a quadratic function (Figure 1 and 2), indicating that at high THI values, an increased response of the mechanisms to cope with HS is triggered. Results agree 5 generally with the ranges reported by Marai et al. (2007), although they show a higher HS threshold. According to Figures 1 and 2, early signs of HS would appear at a THI range among 23 to 25, which would suggest that small ruminants would be capable to cope with hotter conditions than previously estimated. Figure 1 Relationships between respiration rate and THI from reviewed studies on small ruminants Nevertheless, ultimately the vulnerability of sheep and goats to HS will be determined not only by ambient conditions, but also by other factors like the animal’s physiological stage (e.g. pregnancy, lactation) (Hamzaoui et al., 2013), or the specific breed (Brown et al., 1988). Analysed datasets indicate that dairy animals tend to be more susceptible to HS than those from meat systems. While both groups would trigger a similar level of response (i.e. increase in respiration rate) to cope with HS (Figure S1), in the case of dairy animals a higher increase in rectal temperature 6 is observed (Figure S2). This would suggest that cooling mechanisms activated are less capable to dissipate the body heat produced by dairy animals, which would be in accordance with several authors pointing out milk production as an important metabolic heat strain (Hamzaoui et al., 2013; Carabaño et al., 2017). Figure 2 Relationships between rectal temperature and THI from reviewed studies on small ruminants Effects of heat stress on production Decreased productivity under HS has traditionally been attributed to the feed intake (FI) reduction observed in animals exposed to a high thermal load (Salama et al., 2014). However, recent studies have pointed out that feed intake and production can sometimes have dissimilar responses to HS, indicating that different mechanisms could be involved in the productivity reduction associated to HS (Mahjoubi et al., 2014). 7 While a number of studies have analysed the FI decrease in ruminants under HS, ranges for sheep and goats are still unclear. A specific review of the literature about this topic was conducted (Supplementary Table S2). As a result, a relationship between THI and FI was established (Figure 3), showing a gradual response which leads to significant FI reductions (10-25%) at severe HS conditions (THI>25.6), contrasting with previous linear approaches for this issue. Figure 3 Relationship between feed intake decline (%) and THI from reviewed studies on small ruminants Studies with lambs show that HS impairs growth rate, reducing daily gain (Darcan and Cankaya, 2008; Mahjoubi et al., 2014) but also affects pregnancy stage, decreasing the birth weight while increasing the embryo mortality rate (Romo-Barron et al., 2019), thus leading to a efficiency loss at farm level. 8 In dairy sheep and goats, a number of studies have reported decreases on milk production associated to HS conditions. However, in other cases, the effect has resulted on a decline on milk quality, like fat or protein content. A review of the available trials about this topic was conducted (Details described in Supplementary Material S1 and Table S3). The collected data were normalized into fat and protein corrected milk (FPCM) to capture together the effects on milk production and quality (Figure 4). Results indicate a gradual decline of the FPCM productivity, in the range of 2-5% at mild HS levels, up to 20% at severe HS conditions. Figure 4 Relationship between fat and protein corrected milk (FPCM) production decline (%) and THI from reviewed studies on small ruminants This involves a decline of about 1.5% in milk yield for every increase in one point of THI, comparatively higher than previous estimates (Salama et al., 2014). 9 Further negative effects of HS on product quality has also been observed in sheep and goat meat (Devine et al., 1993) and milk (Sevi and Caroprese, 2012), affecting, for example, milk coagulating properties, and consequently, the cheese-making process and control operations (Albenzio et al., 2004). Effects of heat stress on fertility and reproduction Heat stress impacts negatively fertility in small ruminants. For male animals, both the quantity and quality of sperm is reduced and the libido and fertilization capacity are significantly impaired (Kukovics, 2016). In female, it affects the ovarian function, by reducing the oestrous duration and delaying the oestrous cycle, thus affecting conception probability (Romo-Barron et al., 2019). Different factors will determine the specific response to HS at animal level, such as physiological status, breed or HS exposure time. Nutrition, for example, has been identified as one of the main factors affecting ovulation rate and sexual activity, and modulating reproductive endocrine functions (Forcada and Abecia, 2006). Changes in feed and forage (quantity and quality) due to CC may therefore add their own impacts on small ruminants’ systems, playing an important role not only on productivity, but also on reproduction issues. Effects of heat stress on disease occurrence Extreme events (e.g. heat waves or flooding) can severely weaken the animal immunity and udder health and speed up the development rates of pathogens and prevalence of infectious diseases (Escarcha et al., 2018). Moreover, climate change, indirectly, has been found to also increase persistence and abundance of disease vectors and parasites and host resistance to infectious agents (Escarcha et al., 2018). 16 Use of specific supplements can also provide benefits. Whole flaxseed has been shown to help immune function and physiological responses of sheep (Caroprese et al., 2012). Some nutraceuticals (e.g. mineral and antioxidant supplementation) may also be beneficial against the negative effects of HS in sheep (Chauhan et al., 2014) and to improve productive and reproductive functions (Sitzia et al., 2015). Genetic selection and adoption of heat resistant breeds Those breeds that originate in tropical and arid areas are considered to cope better with HS, partly due to anatomical and morphological traits better adapted to hot conditions, such as long ears, large body surface, skin thickness, length of hair and high sweating capacity of sweat glands, among others. Moreover, their low body mass and low metabolic requirements allows them to minimise their water and maintenance requirements. Hair sheep and fat-tailed sheep tend to tolerate heat better than wooled and thin-tailed sheep, while goats with loose skin or floppy ears tend to be most heat tolerant. Animals with light coloured hair/wool and pigmented skin are also better adapted to hot conditions (Al-Dawood, 2017). In contrast, the shorter legs and bodies; short, thick ears, tight skin and dense fleeces of most Northern European breeds makes them comparatively poor at resisting HS. Although swapping to more resistant breeds is one option, this can have its own problems. Breeds native from hot and arid regions often show low productivity. This is due to adaptation to harsh environments, but also to the lack of selection programmes in these regions. In many cases, the large productivity gap with European populations may not justify the introduction of breeding stock from hot areas in crossbreeding programs, although this might be an alternative to selection under more extreme conditions (Al-Dawood, 2017). 17 Selection goals in Europe have mainly focused on high productivity, which have resulted in animals increasingly more susceptible to HS. In fact, when analysing historical milk records, genetic antagonism has been found between productivity and heat tolerance, even for local breeds of dairy sheep and goats (Carabaño et al., 2017). Inclusion of heat tolerance traits in the current selection programs of small ruminants may provide a useful tool to establish climate-oriented farming systems in Europe. However, difficulties for defining heat tolerance criteria and quantifying adequate levels for the chosen traits, may challenge the development of selection programs. Overall, an equilibrium between productivity and adaptation to high heat loads in selection or crossbreeding programs have to be valued for each system of production. Adaptation to increased disease occurrence With the increasing problem of anthelmintic resistance to drugs in recent decades (Van Dijk et al., 2010), more emphasis is required to limit the level of parasitism below acceptable limits while delaying the emergence of drug resistance. This will require an integrated approach which do not intend to lead to parasite-free animals but rather, prevent clinical disease and production losses. Measures will be required at different levels of the farm management including other alternatives to commercial anthelmintic drugs, such as vaccines (Morand-Fehr and Boyazoglu, 1999), host resistance, and grazing management. Good pasture management, in fact, is one of the major means to limit the intake of infective larvae by animals, for example, by the use of parasite-free fields, pasture rotations, and alternation of grazing animals (Morgan et al., 2018). Also, using alternative forages with anthelmintic value (e.g. rich-tannin forages) appear to be a promising option (Morgan et al., 2018). Other 18 measures include using resistant breeds, genetic selection for resistance and resilience to parasite infection (Joy et al., 2020) and early or out-of-season lambing/kidding. The development of cheap and efficient methods of animal identification, registration and control of movements which would allow timely preventive measures in daily operations will also be helpful (Durmus et al., 2019). Adapting pastures/forages to a changing climate Enhancing diverse pastures Biodiversity acts as a safeguard of ecosystem functioning, thus promoting a more stable and resilient ecosystem against fluctuations of climatic conditions. Accordingly, studies indicate that multi-species mixtures contribute to the resistance of grassland yields to extreme events (e.g. droughts), which are expected to become more frequent and severe in most European regions (Hofer et al., 2016). Increasing mixed legume-grass pastures is also a good measure to adapt to potential shortages of global protein sources in Europe, or to face the expected decreased of protein content in non-leguminous plants under CC conditions (Dellar et al., 2018). Consistent yield benefits of mixed grass-legume swards have been reported across a wide range of climatic conditions and fertilization levels, generally outperforming monocultures (Kirwan et al., 2007). Moreover, legumes, when they are grown in pasture-crop rotations, can also reduce weed populations and break the life cycles of pests and diseases (Howieson et al., 2000). Beyond the effects on grassland production, forages from mixed swards may also lead to a positive response at the animal level. Increased herbage voluntary intake has been observed in sheep when more diverse forage mixtures were provided (Niderkorn et al., 2015). The big challenge for legume-based grassland systems will 19 be, however, persistence of legumes. Their relative abundance in mixed swards tends to decrease over time, especially under high N fertilisation levels (Lüscher et al., 2014), but other practices, in particular sheep grazing, also appear to have a detrimental effect on the legume proportion of mixed grasslands (Dumont et al., 2011). Different strategies have been shown to prevent this decline, such as: adjusting fertilisation dosages, increasing defoliation/cutting frequency, or through an adequate pre-selection of species for enhancing more diverse mixed grass-legume swards, considering their competitive abilities relative to each other (Lüscher et al., 2014; Brophy et al., 2017). Reducing tillage Implementing changes in tillage practices could be another adaptation measure applicable across different climatic regions and systems. Reduced tillage increases resilience to CC through improved soil fertility and increased capacity for water retention in the soil, and should generate improvement in the long-term productivity potential. Reduced tillage at pasture reseeding has been observed to prevent the deterioration of pasture quality and promote C sequestration and preservation in pastures, plus is considered to be more effective under conditions of water deficit. Plant breeding Longer term adaptations can also be developed through improved plant breeding. New forage resources are required that are adapted to higher temperatures, increased [CO2] and drought periods (Hopkins and Del Prado, 2007). This might be achieved through exploitation of traits for dehydration tolerance and summer dormancy, either in novel species or for introducing traits into existing widely used 20 grasses and legumes (Volaire et al., 2014). Particular emphasis should be also on targeting plant traits that can deal with more than one abiotic stressor (e.g. grasses that can both tolerate drought and flooding: (Loka et al., 2016)). Dealing with scarcity of feed resources Smart grazing and forage management For small ruminant systems largely reliant on grazing, CC in Europe will require livestock managers to deal with increased inter and intra-annual variability in forage availability dynamics. In rainy areas, ability to manipulate forage quantity and quality through grazing management, fertilisation and use of seeded forages will become very important. Spring plant growth, provided sufficient water availability, and winter production is likely to benefit from mild climate conditions. For southern, drier areas, adjusting the match-up between seasonal nutrient demand and supply through manipulation of an animal´s physiological state or through different mobility patterns will be more appropriate (Martin et al., 2014). In fact, forage resources usually stored for over-wintering livestock could be partially redistributed in summer to deal with increased risk of forage deficit. The benefits from management-intensive grazing strategies, like rotational and multipaddock grazing, will become especially relevant in future scenarios. These practices not only lead to increased pasture yield and utilisation, but they also reduce livestock selectivity towards more palatable foods, thus enabling sustainable sward diversity in the long term (i.e. legume persistence) and providing advantages in terms of animal nutrition (Provenza et al., 2003). Likewise, mixed grazing (i.e. mixing sheep and/or goats with cattle) has also been shown to provide specific advantages 21 to small ruminant systems in terms of pasture utilisation, animal weight gain and control of parasite burdens (D’Alexis et al., 2014). Alternative feed resources A number of by-products from agricultural, food processing, forestry and bioenergy activities could be used for feeding small ruminants as an adaptive response to forage supply seasonal constraints (Salami et al., 2019). Large volumes of agroindustrial by-products are produced in Europe every year which are not always adequately valorised. Among them, olive cake, citrus pulp and tomato pomace have been shown to be particularly suitable for small ruminant feeds (Table 1). Other agrifood by-products have also been successfully tested and its potential use deserves to be further explored (Supplementary Table S4). Table 1 Alternative feed sources suitable for small ruminants and estimated availability in Europe Alternative feed sources Availability in Europe (kTon/yr) References in small ruminants1 Olive cake 8190 Abbeddou et al 2011, Arco-Pérez et al 2017, Cabbidu et al 2004, Chiofalo et al 2004, Hadjipanayiotou et al 1999, MolinaAlcaide et al 2010, Ben Salem and Znaidi 2008 Tomato byproducts 2601 Abbeddou et al 2011, Arco-Pérez et al 2017, Di Francia et al 2004, Razzaghi et al 2015, Romero-Huelva et al 2013; Romero-Huelva et al 2013b; Romero-Huelva et al 2017, Ben Salem and Znaidi 2008, Denek and Can 2006 Citrus pulp 1073 Fegeros et al 1995, Romero-Huelva et al 2013; RomeroHuelva et al 2017, Bueno et al 2002, Caparra et al 2005, Lanza et al 2001, Scerra et al 2001 Other fruit byproducts 1301 Razzaghi et al 2015, Sedighi-Vesagh et al 2014, Volanis et al 2004, Eliyahu et al 2015, Pirmohammadi et al 2006 Other vegetable by-products 3189 Nudda et al 2006, Romero-Huelva et al 2013; Romero-Huelva et al 2013b 1The complete reference list is provided in the supplementary material (Table S4) 22 Despite this, poor nutrient balance, seasonality and difficulty for handling and longterm conservation as fresh material are crucial issues that constrain their wider use as animal feed. Preservation through different techniques like pelleting, ensiling or manufacture of feed blocks can help to overcome these difficulties, expanding the potential for including a broader range of agro-industrial by-products in small ruminants diets (Ben Salem and Smith, 2008). Tree leaves and shrubs further offer an alternative forage supply, especially during periods when grassland growth is limited or dormant due to unfavourable weather conditions (summer/autumn). Various tree species have been identified of interest for small ruminants as a source of proteins and macroand micronutrients. According to reviewed studies, leaves from white mulberry (Morus alba), ash (Fraxinus excelsior), alder (Betula alba), robinia (Robinia pseudoacacia) and lime trees (Tilia platyphyllos) are especially suitable to be included in ruminants diet (Luske and Van Eekeren, 2015), although a number of fodder shrubs have also been identified for their potential in Mediterranean systems (Eichhorn et al., 2006). Integrated approaches Agroforestry systems Besides serving as an additional feed source, planting forage trees in grazing areas (introduction of silvo-pastoralism) can also provide shelter, as previously mentioned, preventing HS and improving animal welfare. Moreover, trees could involve important synergies for pasture production, especially in harsh environments, as they can extend the seasonality of the understory production by buffering the microclimate under the canopy and by enhancing an uneven distribution of nutrients. 23 Southern Europe already hosts several oak-based agroforestry systems (e.g. Dehesa-Montado in the Iberian Peninsula) that have been shown to be good examples of highly resilient, productive and biodiverse farmed landscapes (Hopkins and Del Prado, 2007). In parts of temperate Europe there are also wood pastures systems, that provides shelter for sheep in both, winter and summer. Similarly, hedgerow systems found in central Europe can be considered examples of the integration of trees with pastures for livestock production. Fire risk control Grazing with small ruminants has been proposed as a valuable tool for the prevention of fire risks in different landscapes and systems. They not only allow to control the accumulation of flammable vegetation, but they can also be managed for clearing and maintaining firebreaks, especially in remote areas or with steep slopes, where they can be an alternative to mechanical methods. If adequately valued, this activity could involve an additional income to the farm while providing an alternative source of feed. The role of small ruminant grazing for the preservation of a number of landscapes in Europe have been highlighted in several cases, like Atlantic heathlands (Jáuregui et al., 2009) or Mediterranean scrublands (Mancilla-Leytón et al., 2013). In these areas, arable farming is unfeasible and this system often represents the only way of productively using the land. In Southern Europe, where more severe fire events are expected with the prospect of warmer and drier summers, silvopastoral systems involving goats are particularly indicated, being a browser species well adapted to feed on shrubby vegetation and arid climatic conditions. Besides avoiding vegetation accumulation, it can also help to reduce the shrub encroachment that will be enhanced under CC conditions. In 24 contrast, in commercial forest plantations of Central/Northern Europe, sheep seem more suitable for controlling competing ground vegetation than other livestock ruminants, like cattle or goats, that may cause more damages to trees, by trampling or browsing respectively (Sharrow et al., 1989). Cover crops Cover crops are non-marketable plants grown to protect the bare soil, providing several benefits in terms of soil health, weeds control and nutrient balance. In the context of CC, they can help to increase adaptive capacity against extreme rain events (i.e. soil erosion) and droughts (Alonso-Ayuso et al., 2014) while mitigating climate warming through changes in biogeochemical processes and albedo. However, their use is often limited as they do not involve immediate revenue for farmers. Coupling cover crops and small ruminant systems can offer interesting opportunities for both sides, either as an additional source of forage and as grazing management tool for plant growth control. Structural and practical challenges affecting small ruminants’ sustainability in a climate change context The sector has been experiencing economic and structural changes in recent decades, mainly due to a decrease in livestock numbers (linked to changes in consumer trends and intensification of production), outbreaks of contagious diseases and policy changes. Climatic hazards are expected to add yet further challenges to this ongoing situation. 25 At the EU level, several policy instruments are already available for helping the sector in its capacity to deliver a broad range of ecosystem services. Nevertheless, due to the numerous challenges that the sector is likely to undergo in the future it is becoming clear that the current level of support (e.g. the Common Agricultural Policy (CAP) post-2020) is likely to be insufficient, especially for systems that are more extensive. Climate change in Europe, as previously mentioned, will require livestock managers to be more flexible in order to deal with increased variability in forage quality and productivity. One strategy may be to save forage in years that are more productive, which would demand for additional investment and costs for preservation technologies and storage. For pasture-based systems, the reduced grazing of animals in higher temperatures will necessitate provision of supplementary feed or reconciliation of the deficit with lower production levels. To guarantee future sustainability of small ruminant systems, farmers will therefore need coordinated support from different agents (e.g. regional to national governments, producers’ associations, research institutions) providing both the financial instruments (e.g. insurance plans, credits for investments) and the technical guidance (e.g. agroclimatic forecasts, heat-resistant breeds) to adopt the necessary adaptation measures. For optimising the role that policy instruments have on the sustainability of small ruminant systems, policies must be aligned with the strategies relating to a number of cross-cutting issues, including CC, environment, rural development, bio-economy, food security, research and public health. 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Regional availability of organic by-products from agri-food industries in Europe was obtained following the methodology described in Pardo et al., 2017 from FAOSTAT data. 51 Table S4 – Selection of reviewed studies involving utilisation of agri-food by-products in the diet of sheep and goats Reference Basal diet Alternative feed sources Supplement type Animal Breed Abbeddou et al 2011 Barley straw/concentrate Olive cake and leaves, tomato pomace - Dairy ewes Awassi Arco-Pérez et al 2017 Alfalfa hay/concentrate Olive cake, Tomato surplus Silage Dairy goats Murciano-granadina Ben Salem and Znaidi 2008 Wheat straw/concentrate Tomato pulp, olive cake Feed blocks Lambs Barbarine Bueno et al 2002 Grass hay/concentrate Citrus pulp - Kids Saanen Cabbidu et al 2004 Grass hay/concentrate Olive cake Silage Dairy ewes Sarda Caparra et al 2005 Oat hay/concentrate Citrus pulp Dried Lambs Merino Chiofalo et al 2004 Alfalfa hay/concentrate Olive cake - dairy ewe Comisana Denek and Can 2006 Wheat straw/wheat grain Tomato pomace Silage Rams Awassi Di Francia et al 2004 Oat hay/concentrate Tomato pomace Silage dairy ewe Comisana Eliyahu et al 2015 Wheat hay/concentrate Pomegranate pulp, grape pulp, avocado pulp Silage Lambs Assaf Fegeros et al 1995 Alfalfa hay/concentrate Citrus pulp Dried Dairy ewe Karagouniko Hadjipanayiotou et al 1999 Barley straw/concentrate Olive cake Silage Dairy ewes & goats Chios, Damascus Lanza et al 2001 Wheat straw/barley+maize Citrus pulp - Lambs Barbaresca Molina-Alcaide et al 2010 Alfalfa hay/concentrate Olive cake Feed blocks Dairy goats Murciano-granadina Nudda et al 2006 Alfalfa hay/concentrate Linseed cake Extruded Dairy goats AlpinexSarda Pirmohammadi et al 2006 - Apple pomace Silage, dried Rams Gezel Razzaghi et al 2015 Alfalfa hay/concentrate Pomegranate seed pulp, tomato pomace - Dairy goats Saanen Romero-Huelva et al 2013 Alfalfa hay/concentrate Tomato fruits, citrus pulp, brewer's grain and yeast - Dairy goats Murciano-granadina Romero-Huelva et al 2013 Alfalfa hay/concentrate Tomato and cucumber fruit wastes Feed blocks Dairy goats Murciano-granadina 52 Romero-Huelva et al 2017 Alfalfa hay/concentrate Tomato fruits, citrus pulp, brewer's grain and yeast - Dairy goats Murciano-granadina Scerra et al 2001 Oat hay/concentrate Citrus pulp Silage Lambs Merinizzata Sedighi-Vesagh et al 2014 Alfalfa hay/concentrate Pistachio by-products - Dairy goats Saanen Volanis et al 2004 Oat hay/concentrate Orange fruit waste Silage Dairy ewe Sfakian Volanis et al 2006 Oat hay/concentrate Citrus pulp Silage Dairy ewe Sfakian 53 References Supplementary Material S2: Abbeddou S, Rischkowsky B, Richter EK, Hess HD and Kreuzer M 2011. 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