Maniçoba for sheep and goats - forage yield, conservation strategies, animal performance and quality Maniçoba for sheep and goats - forage yield, conservation strategies, animal performance and quality of products

: In dry regions worldwide, providing feed for ruminants has been a great challenge, with a need to use plants which contribute to the resilience of production systems. Maniçoba is seen as a potential forage resource in the Brazilian semiarid, being used as hay or silage to feed ruminants. This review summarized results regarding forage production of maniçoba, in addition to dry matter (DM) intake, productive performance, and quality of animal products obtained providing maniçoba based diets, when compared to diets composed by other roughages for goats and sheep. Considering the evaluated studies, the average yield of maniçoba varied from 367 to 1,592 kg DM ha -1 , enhancing the forage yield by increasing plant fertilization and planting density. Diets based on maniçoba promoted similar or higher intake of DM and productive performance for goats and sheep, when compared to diets comprising other forage resources. The quality of animal products was also similar to the ones obtained with diets based on traditional roughages, such as Tifton 85 hay or spineless cactus. Therefore, maniçoba allows a forage production that may contribute to ruminant production systems in semiarid environment and promote productive performance and animal product quality compatible to the ones provided by traditional forage plants.


INTRODUCTION
Food security for herds has been an important challenge for livestock production in arid and semiarid regions (MLAMBO & MAPIYE, 2015) and there is great concern about food production to meet the demands of the world's growing population, with drylands playing a relevant role in this scenario (TARRASÓN et al., 2016). In this sense livestock systems need to improve land use by using adapted forage plants that are inserted in the socioeconomic context of the population and contribute to new strategies for supplying nutrients for ruminants, reducing production losses and increasing animal yield and farm income.
Maniçoba comprises plants (wild species) of the genus Manihot, including Manihot glaziovii Müll. Arg., Manihot catingae Ule and Manihot carthaginensis (Jacq.) Müll. Arg, all native to the Brazilian semiarid, showing genetic and Gomes et al. morphoagronomic diversity (CAMPOS et al., 2020). The plants are perennial, tolerant to cuttings and long periods of drought, with morphological adaptation related to water retention (NASSAR et al., 2010), and physiological mechanisms via control of stomatal aperture to maintain a positive carbon balance even in drought conditions (MORGANTE et al., 2020). In ruminant feeding, maniçoba is used exclusively as hay or silage to reduce the toxicity of hydrocyanic acid, thus allowing a safe feeding for animals (MATOS et al., 2005;SOARES, 2000;SOUZA et al., 2006).
Productive and qualitative characteristics of the plant must be considered, along with its potential to constitute diets that provide a proper productive performance to the animal. In this sense the evaluation of yield and quality of maniçoba forage, as well as the assessment of dry matter (dM) intake, productive performance of goats and sheep, and its influence on animal product quality, are important aspects to understand the potential of this plant as an alternative for livestock production systems in semiarid environments.
The present review summarized the results of forage yield of maniçoba in the semiarid region of Brazil, the dM intake and productive performance of goats and sheep fed maniçoba-based diets, and the quality of animal products.

Productivity and factors that affect the forage yield
The results of five experimental trials (n = 50 treatments) in the Brazilian semiarid evaluated the forage production of maniçoba, considering single-crop and rainfed conditions. These studies were carried out in the states of Pernambuco and Paraíba, with cutting intervals varying from 152 to 1,095 days and accumulated rainfall in the period varying from 321 to 1,163 mm. The average forage yield reported for maniçoba ranged from 367 to 1,592 kg dM -1 ha -1 (Table 1), considering different cutting intervals of the plant, reaching 3,733 kg dM -1 ha -1 regarding the sum of the production of two consecutive harvests, performed after up to fifteen months (SOARES, 1989).
Several factors influence the production of maniçoba forage. ARAÚJO FILHO et al. (2011) verified that organic fertilization increased the yield by up to 80%, in comparison to non-fertilized maniçoba, due to the nutrient supply to the crop. The increase in plant density also increased the forage yield, with plant densities reaching 6,667 (ARAÚJO FILHO et al., 2011) or 10,000 plants ha -1 (SOARES, 1989), indicating that maniçoba can respond favorably to intensive crop management.
Soil management using ridges and the cutting heights of the plants (MOREIRA FILHO et al., 2008), the water depths and the nitrogen (N) fertilization (ARAÚJO FILHO et al., 2013) are also factors that affect the plant growth and increase the forage yield. Presumably, the ridges increase the accumulation and availability of nutrients in the soil, favoring the development of the plant root system. The increase in productivity with N fertilization suggested that maniçoba has efficient metabolic responses to the use of this nutrient.
Beyond the forage yield, BELTRÃO et al. (2008) pointed out the proportion of leaves on the plant, reporting that approximately 50% of the produced forage (kg dM -1 ha -1 ) corresponds to this component, which may still be incremented by management practices, as for instance organic fertilization.
These results denoted that maniçoba allows forage yield compatible with the semiarid environment. Therefore, it contributed to the forage input for ruminant production systems, while management factors may increase the productive efficiency of the crop.
It is important that there should be a greater number of studies evaluating this forage resource, especially including diverse locations in the semiarid region, thus enlarging the database on crop yield, above all regarding long-term studies.
Crude protein levels ranged from 90.8 to 227.5 g kg -1 , and NdF varied from 355.0 to 586.0 g kg -1 ( Table 2). The offered forms of maniçoba (fresh, hay or silage) did not result in great differences on main parameters of chemical composition. On average, fresh maniçoba showed 173.8 g kg -1 for CP, while as hay and silage CP levels were 141.1 and 154.7 g kg -1 . Additionally, NdF for fresh maniçoba was 449.8 g kg -1 , while as hay and silage it was 475.5 and 494.8 g kg -1 , respectively ( Table 2). The authors attributed changes in chemical composition mainly to the proportion of leaf/stem (FRANÇA et al., 2010), as well as genotype and development stage of the plant (MOREIRA FILHO et al., 2009), indicating the conservation process of maniçoba as an important tool to maintain the nutrients.
Maniçoba exhibited high lignin levels, which may reduce the forage digestibility. Conversely, this forage also showed high CP and low NdF, compatible with or higher than the ones presented by other forage resources used to feed ruminants in the Brazilian semiarid. High CP and low NdF are positive aspects in roughage for feeding ruminants. SANTOS et al. (2017) evaluated different forages in natura and observed 208.0 g kg -1 CP and 434.0 g kg -1 NdF Table 1 -Mean and maximum forage yield (kg dM ha -1 ) of maniçoba, cutting intervals (days), municipality, and rainfall (mm/period) from studies carried out in Brazilian semiarid in rainfed condition.
Mean productivity ---Maximum productivity---  Table 2 -Crude protein (CP), ash, ether extract (EE), neutral detergent fiber (NdF), acid detergent fiber (AdF), hemicellulose (HEM), cellulose (CELL) and lignin (LIG) of maniçoba (in natura, hay and silage).  In a study carried out by PARENTE et al. (2007), maniçoba in natura showed 13.91% CP when supplied with 100 kg N ha -1 , while without nitrogen fertilization the CP content was 8.58%, According to MENEZES et al. (2012), the potential dM degradability of maniçoba hay was 70%, while the effective degradability (5%/h) was 57.4%. The potential degradability of CP was 92.5% and the effective one (5%/h) was 80%. SOUZA et al. (2006) reported a potential degradability of NdF varying from 52.12 to 54.45%, with an effective degradability (5%/h) varying from 32.41 to 32.55%. FRANÇA et al. (2010) observed that the dM degradability is related to a great participation of leaves in the produced biomass, presenting tissues with less thickened walls and lower lignification, promoting higher degradability than the stem part. These authors also reported that the main factor promoting low degradability of NdF was the thickening and lignification of cell walls, especially in stem tissues.
Macromineral levels in maniçoba are shown in table 3. Nitrogen and potassium presented the greatest contents, followed by calcium and magnesium. According to ANdRAdE et al. (2014), N and K levels of maniçoba are influenced by the stage of leaf development and the plant location. They observed N and K differences in the leaves at the beginning of the senescence process compared with expanding or completely expanded leaves, attributed to the nutrient translocation, especially N from old to new leaves. In addition, N and K contents differed according to the municipality of origin of the maniçoba sample, associated with soil and climatic characteristics.
Sodium, iron, zinc, and manganese were the main microminerals presented by maniçoba (Table 4). Mineral elements exert an important role in the plant, including structural functions and metabolic process, and they are also essential for animals. The insufficiency of even one element may negatively affect animal growth, as well as health and reproductive functions. In the Brazilian semiarid the main source of minerals for ruminants is forage, and the supply of minerals through maniçoba forage contributes to meeting the requirements for these elements.
Furthermore, the knowledge of mineral contents in maniçoba enables the comprehension of extraction and exportation of nutrients by the plant, and determines the mineral reposition, according to the forage yield.
As secondary compounds, da SILVA (2016) reported the presence of steroids, saponins, tannins and flavonoids in maniçoba leaves, with differences in concentration among evaluated accessions and leaf maturation stages. In addition, BELTRÃO et al. (2015) reported total tannins varying from 0.2 to 5.3% dM and HCN ranging from 97.2 to 291.6 mg kg -1 dM in maniçoba, while FRANÇA et al. (2010) observed tannin levels of 1.58 and 1.87% dM, respectively for maniçoba in natura or hay, and reported an important antinutritional action when they exceeded 5% dM in Table 3 -Content of macrominerals in maniçoba in natura, subject to fertilization, pruning and different planting spacings.

Mineral
- diets, indicating there is no negative effect of tannin levels presented by maniçoba on dM digestibility. The high presence of cyanogenic glycosides in maniçoba, when hydrolyzed, release hydrocyanic acid (HCN) through the action of enzymes such as ß-glucosidase (linamarinase), which may be poisonous to animals, depending on the ingested quantity. Ingestion greater than 2.4 mg of HCN/kg of body weight may cause several disorders (SOARES, 2000). SOUZA et al. (2006) verified 972 mg kg -1 of HCN in maniçoba in natura (% dM) and 162 mg kg -1 in silage (% dM), while SOARES (2000) reported a reduction in HCN by over 65% in maniçoba silage after the first 29 days of ensilage, reaching a reduction of up to 78% after 174 days. According to MATOS et al. (2005) the enzyme linamarinase is inactivated by heat and the ensiling process also contributes to the fermentation of glycosides by anaerobic microorganisms, reducing HCN concentration.
Maniçoba silage can be made without using additives promoting a proper fermentation process to the ensiling mass, showing aerobic stability for up to 14 days after silo opening (SOUZA et al., 2006); although, the use of additives, such as corn meal, can contribute to the quality of the silage (BACKES et al., 2014).
Similarly, FRANÇA et al. (2010) reported HCN values of 512.83 and 86.34 mg kg -1 dM for maniçoba in natura or hay, respectively. during the haying process, the plant is chopped and dehydrated promoting the HCN volatilization by the action of sunlight and wind (ARAÚJO et al., 2004). The use of maniçoba silage or hay did not affect the DMI and the average daily gain of sheep (MACIEL et al., 2019). Therefore, both conservation strategies (hay or silage) can be offered to ruminants, seeing that they are also important to reduce HCN levels in the forage, providing safe feed.
The chemical composition of maniçoba offers opportunities to perform studies aiming the evaluation and selection of genotypes with lower concentrations of hydrocyanic acid and lignin, and greater degradability of fiber, as well as the evaluation of crop management practices that increase the degradability of the fibrous fraction.

Dry matter intake and productive performance of goats and sheep
dry matter intake (dMI) data for goats and sheep fed on maniçoba based diets (hay or silage) were obtained from 13 studies (n = 46 treatments). In four of them maniçoba was compared to other roughages (Table 5), while in nine increasing levels of this forage in diets were evaluated, replacing roughages (MENdONÇA JÚNIOR et al., 2008;MOURA et al., 2020) or concentrates (CASTRO et al., 2007;ARAÚJO et al., 2009a) (Table 6).
Maniçoba diets promoted similar dMI compared to diets composed by others roughages offered to goats and sheep, and even higher DMI when compared to feed based on hay from feijão-bravo (Capparis flexuosa L.) and gliricidia (Table 5), which might be associated to the presence of anti-nutritional factors, such as tannins and coumarins, respectively, impairing the acceptance of the feed by the animals (LIMA JÚNIOR et al., 2014;MOREIRA et al., 2008). In addition, MACIEL et al. (2019) reported greater dMI by sheep fed maniçoba hay based diets compared to a Tifton 85 based diet (Table 5).
In one of those studies, comparing maniçoba hay with Tifton 85 in diets for Moxotó goats, LIMA JÚNIOR et al. (2015a) reported that animals fed with this roughage had -9 g day -1 of body weight variation, while the Tifton 85 based diet (control diet) promoted 10 g day -1 of weight gain (Table 7), without statistical difference for diets. The authors attributed the low AdG promoted by both diets to a lack of adaptation of the animals to the feedlot management, because they had come from an extensive production system, in addition to the advanced age of the animals, and the low dMI presented by goats.
The productive performance of animals receiving maniçoba diets was similar when compared to the other roughages or increasing levels of this roughage in diets in all studies, except MOREIRA et al. (2008), who observed greater AdG for goats fed on a diet based on maniçoba hay compared to a gliricidia based diet, due to the greater dMI (Table 7). The food consumption of animals fed maniçoba diets is an important factor influencing the productive performance, seeing that dMI determines the supply of nutrients. diets composed of maniçoba provided up to 290 g day -1 of weight gain for feedlot sheep, including 20 to 40% dM (CASTRO et al., 2007) or 30% dM of this roughage (CARTAXO et al., 2008). In addition, one study evaluated milk yield of goats fed increasing levels of maniçoba in diets (30 to 60% dM) (ARAÚJO et al., 2009b).
The results for productive performance of sheep and goats fed maniçoba diets demonstrate weight gain compatible to the one promoted by diets comprising traditional roughages, and enable the inclusion of considerable levels of this plant in animal diets. In addition, other research fronts are important to be pursued, providing a better understanding of the maniçoba based diets for ruminants, regarding the methane emission and the interactions of nutrition and immunological or reproductive responses.

Quality of animal products
Using maniçoba for sheep did not result in changes in carcass traits (LIMA JÚNIOR et al., 2014;MACIEL et al., 2015) and non-carcass components yield (MACIEL et al., 2015) when compared to Tifton 85 hay based diets, neither were there changes in the yield of "buchada" and "panelada" (typical dishes using organs and viscera) (LIMA JÚNIOR et al., 2015a).
Increasing maniçoba in diets (35 -70%) for Moxotó and Canindé goats did not alter the centesimal composition, final pH and color of the meat (LISBOA et al., 2010), evincing proper digestive and metabolic responses. The replacement of spineless cactus by maniçoba in sheep diets did not change the physicalchemical composition of the meat, its color or the weight loss in cooking (MOURA et al., 2020).  An inclusion of maniçoba of up to 60% dM in diets for lactating goats did not modify the physical-chemical composition (proteins, fat,  lactose, dry extract, density and acidity) of the milk (ARAÚJO et al., 2009b;COSTA et al., 2008), nor the fatty acid contents (saturated, monounsaturated and polyunsaturated) (MESQUITA et al., 2008), or the sensorial parameters (odor, taste and overall appearance) (COSTA et al., 2008). Therefore, the use of maniçoba for goats and sheep has not promoted changes in qualitative parameters of animal products, especially meat and milk, compared to traditional roughages. Further studies are important to increase the database for this forage plant on quality of animal origin products.

CONCLUSION
Maniçoba presents forage productivity that may contribute to livestock production systems in the Brazilian semiarid, besides providing forage with adequate nutritional value. Its use in diets for sheep and goats has allowed dry matter intake, productive performance, and quality animal products similar to the ones provided by traditional forage resources, such as Tifton 85 or spineless cactus, reinforcing the possibility of its use in the sheep and goat production systems. Table 7 -Productive performance (weight gain or milk yield) of sheep and goats fed on diets comprising maniçoba compared to others roughages or increasing maniçoba levels in diets. -