OAK AS A FEED INGREDIENT FOR RUMINANTS: A REVIEW

Mesopotamia Journal of Agriculture, Vol. 51, No. 4, 2023 (86-105) Mesopotamia Journal of Agriculture https://magrj.mosuljournals.com OAK AS A FEED INGREDIENT FOR RUMINANTS: A REVIEW Hoger M. Kh. Hidayet 1 , Jalal E. Alkass 2 , Kamal N. S. Mustafa 3 Department of Pathology and Microbiology, College of Veterinary Medicine, University of Duhok, Duhok, Iraq 1 Dept. of Animal Production, College of Agricultural Engineering Sciences, University of Duhok, Duhok, Iraq 2,3 Article information Article history: Received: 14/09/2023 Accepted: 18/12/2023 Published: 31/12/2023 Keywords: Oak Acorn, Ruminants, goat, sheep. DOI: http://10.33899/mja.2023.143326. 1275 Correspondence Email: [email protected] ABSTRACT The influences of oak inclusion into the diet of ruminants on performance, feed digestibility, milk production and blood metabolites are reviewed herein. Oak as an alternative and available feed are being utilized in many parts of the world, especially in areas suffering from shortage of feed ingredients. It is evident that different oak species have different impacts on various animal species. Oak fed at low levels in the diet may not affect digestibility, but when they are fed at high level may lead to lessen the digestibility of dry matter. Adding oak products may improve the daily milk yield of goats. Feeding oak acorns and leaves to growing goat kids might not been accompanied by significant improvement in daily weight gain and feed conversion ratio, while when feeding adult sheep on high level of dietary oak, it may result in lowered daily weight gain. Different oak species produce different amounts of tannins, which after ingestion by animals, act to form complexes with the proteins of diet, this may lead to lower digestibility of nutrients or may beneficially affect to positive flow of amino acids into abomasum and small intestine by reducing the protein degradability in the rumen. Thus, the extent of the impact of dietary oak on ruminants’ performance depends on the species of both animals and oak, and the level of oak being used in the diet. College of Agriculture and Forestry, University of Mosul. This is an open access article under the CC BY 4.0 license (https://magrj.mosuljournals.com/ ). INTRODUCTION The Quercus genus is considered one of the indigenous species in Iraq, where it is the dominant tree covering in the northern and northeastern region of Iraq (Almaroof, 2005). Oak is a woody perennial plant that belongs to the genus Quercus (Pourhashemi et al., 2018), has a big impact on the ecosystem of the world and possess the ability to prevent soil erosion, preserve water resources and provide a rich environment for wildlife. The fruit produced by the trees are edible for many animals and insects which rely on these trees to get their feed for survival. Acorns as a cheap and available plant material, supplies a potential source of biologically active compounds, which is applicable in many industries including food and pharmaceutical industries (Rakić et al., 2005). Tannins are found throughout the oak plant, with higher levels in the leaves, buds, twigs, and acorns (Bausch and Carson, 1981) they decrease the degradability of dietary protein in the rumen through making complexes with proteins and increase the efficiency in nitrogen recycling. The formed tannin-protein complexes may be dissociated in the abomasum, leading to an 86 Mesopotamia Journal of Agriculture, Vol. 51, No. 4, 2023 (86-105) increase the amount of by-pass dietary amino acids available for absorption in the intestine (Patra and Saxena, 2011). The increase in amino acids availability could enhance energy partitioning toward milk production (Frutos et al., 2004), and improve milk, fat and protein yield of sheep and Meriz goat ( Alkass, et al., 2018; Dosky et al. 2012). Moujahed et al., (2007) concluded that inclusion of oak acorns in diets to more than 50% of concentrate diet as a replacement of barley changed fermentation pattern including reduction in in vitro gas production that is used as an indication to lowered microbial activity in the rumen. In rabbits, boiled extract of oak leaves resulted in an improvement in lipid profile and continuous significant decrease in glucose for 24 hrs. (Abdul-Rahman, 2008). Depending on the low cost of oak acorns, Al Jassim, et al., 1998 have suggested that substitution of 25% of barley with oak acorns would be economically beneficial for feeding Awassi lambs. Similarly, Kaya and Kamalak, (2012) suggested that inclusion of oak acorns in the concentrate mixtures of goats can be economically advantageous particularly in autumn and winter when scarcity of feedstuffs happens. This paper reviews the impact arisen upon feeding oak products to ruminant animals in terms of animal performance including diet digestibility, rumen fermentation, milk yield, milk composition and growth performance. Composition of oak acorns The proximate analysis and active compounds of different species of oak acorns has been carried out by many workers throughout different regions of the world as shown in Table (1) and they vary considerably in their chemical composition, especially in ether extract and tannin contents. Generally, the DM content in oak acorns varies from 530 to 910g kg-1 and by comparing to other wildlife foods, the CP content of acorns is relatively low, which ranges between 28.4 and 79 g kg-1 (Kirkpatrick and Pekins, 1989), such variation in the chemical composition of the oak acorns could be expected due to difference in oak species, stage of oak maturity, as well as the production site ( Gasmi-Boubaker et al.,2007). Oak contain tannins, which are found throughout the oak plant, with higher levels were found in the leaves, buds, twigs, and acorns (Bausch and Carson, 1981). Tannins are chemically diverse group of water soluble phenolics which bind proteins to form soluble or insoluble complexes (Hagerman and Buttler, 1989; Mueller-Harvey et al., 2019) and occur primarily in condensed and hydrolysable forms (Min et al., 2003; Makkar, 2003). Acorns contain both types of tannins; condensed and hydrolysable (Łuczaj et al., 2014). It was demonstrated that condensed tannins are more effective than hydrolysable form on animal performance (Makkar et al., 1995) as the condensed form is usually nor broken down, neither absorbed in the intestine, and is able to make complexes with proteins of feed, mucosa and digestive enzymes. Therefore, they primarily act to decrease protein digestibility causing animals to be in negative nitrogen balance, when animals lose more nitrogen than they ingest (Makkar, 2003). When a forage containing condensed tannin is consumed, complexes are formed and 87 Mesopotamia Journal of Agriculture, Vol. 51, No. 4, 2023 (86-105) then condensed tannin in the rumen become bound to cell coat polymers of bacterial cells (Jones et al., 1994), thus affecting the proteolysis in the rumen (Frutos et al., 2004). Differently, hydrolysable tannins are broken down in the gastro-intestinal tract into smaller phenols, some of these phenols are absorbed into the bloodstream, detoxified and excreted from the body (Kirkpatrick, and Pekins, 1989). Table (1): The composition of oak acorns of different species (g kg-1DM). Acorn’s species Q. aegilops Q. coccifera Q. coccifera DM OM CP EE CF NDF TPh TT CT Reference 530 537 - 976 972 978 39 29 39 25 23 - 236 253 - 516 498 362 - - - Q. suber 715 971 79 - 118 274 - - - Q. ithaburensis Q. calliprinos Q. persica 910 967 28.4 7.6 342 - - - - Al Jassim et al., (1998) Moujahed et al., (2007) GasmiBoubaker et al., (2007) Rababah et al., (2008) 982 980 49.4 23.1 131 54.5 - 231 5.36 4.68 1 Q. coccifera 648 977 42.3 45 - 284 - Q. persica 920 971 40.5 60.5 - 280 12.79 8.79 2.01 Q. aegilops 593 968 42 - 94.61 - 87.7 73.2 - 3.68 3.76 Aghamohamadi et al., (2014) Kamalak et al., (2005) Jafari et al., (2018) Hidayet and Mustafa, (2020a) Q.: Quercus, DM: dry matter, OM: organic matter, CP: crude protein, EE: ether extract, CF: crude fiber, NDF: neutral detergent fiber, TPh: Total Phenolics, TT: Total Tannins, CT: Condensed Tannins. Effect on feed intake Studies on the effect of different species of oak (Quercus spp.) acorns and leaves on voluntary feed intake in different species are given in Table (2). It seems from the table that feeding acorns has resulted in either to increase dry matter intake ( Froutan et al., 2015) or has no effect on dry matter intake in goats ( Gasmi-Boubaker et al, 2007) or a reduction of dry matter intake was noticed ( Jafari et al., 2018). Also, a significant increase in dry matter intake was indicated when feeding calves on oak leaves (Sharma et al., 2008). 88 Mesopotamia Journal of Agriculture, Vol. 51, No. 4, 2023 (86-105) Table (2): Effect of dietary oak leaves or acorns on dry matter intake. Species No. Treatments DMI Finding Reference -1 kg d 0.975 a Feeding acorns at levels of 1.018 80, 170 or 250g kg-1 feed to Froutan et al., b growing goat kids caused a (2015) 1.058 significant increase in daily b DMI as compared to that of 1.059 control group. Goat kids 24 Male calves 15 Control Oak acorns 80g kg-1 feed Oak acorns 170g kg-1 feed Oak acorns 250g kg-1 b feed P value 0.004 Control 2.05 a -1 Oak leaves 220g kg 2.83 b feed Oak leaves 400g 2.90 b kg-1 feed P value <0.05 Heifers Boer goat 6 10 Control Oak leaves 425g feed Oak leaves 636g feed P value Control Oak acorns 753 g DM P value Control Oak acorns 200 g DM Oak acorns 400 g DM P value kg -1 2.96 3.11 kg-1 3.52 A significant increase in daily DMI in growing calves was noticed inclusion of oak leaves in the diet at the levels of 220 and 400g kg-1 feed. No effect of feeding oak leaves on DMI was found in heifers when fed to the level up to 636g kg-1 feed. Sharma et al., (2008) Paswan and Sahoo, (2012) >0.05 0.891 0.868 No effect of consuming Gasmiacorns was noticed in goats Boubaker et fed on acorn to the level of al., (2007) >0.05 753 g kg-1 DM. Goat 24 1.75 a In goats fed on acorns at 200 Jafari et al., kg-1 1.63 a g kg-1 DM no effect of of (2018) acorns on DMI was found, -1 kg 1.41 b but in the other group when the level of acorns was <0.01 elevated to 400 g kg-1 DM, a dignificant reduction in DMI happened. DMI: Dry matter intake, No.: Number of animals studied. Different letters within the column of each reference show significant difference. kg-1 It is known that there is a difference in the ratio of tannins in different oak species and oak plant parts, therefore, the increase in dry matter intake in goat kids consumed diets containing acorns might be a result of the low concentration of hydrolysable tannins in the oak acorn diets or it might be due to the higher efficiency of goat ruminal microbes in degradation or detoxification of the tannins (Froutan et al., 2015). The decrease in DM intake in goats fed oak acorns can be attributed to the decreasing palatability due to bitter or astringent taste of tannins (Becker and Makkar, 1999). 89 Mesopotamia Journal of Agriculture, Vol. 51, No. 4, 2023 (86-105) Digestibility In vitro digestibility Is well known that in vitro techniques have been widely used to establish assessment of animal diets, supplemented herbs and their extractives as feed components. In vitro gas production technique has been commonly used to determine the metabolizable energy and organic matter digestibility of feeds (Kamalak et al., 2005). In an in vitro work, Aghamohamadi et al., (2014) found that the produced methane volume was unaffected by inclusion of Quercus persica acorns at the level of100g kg-1 feed, while when the level of acorns in the diet was increased to 300g kg1 feed, a significant reduction in methane produced from fermentation of diet was observed as shown in Table (3). Furthermore, Moujahed et al., (2007) indicated a lag time represented by negative values (-0.5, -1.0, -1.3) respectively by replacing 50, 75 and 100% of diet barley with Quercus coccifera acorns. The finding had been supported by a significant reduction in immediate in vitro gas production of diets followed replacing 50, 75 and 100% of the barley with oak acorns. The same authors found that replacing 75% or 100% of diet barley with acorns, also caused a significant (P<0.01) reduction in total in vitro gas production, while the researches noticed no change in lag time, methane and total gas production of fermentation after replacing 25% of diet barley with acorns in vitro. The authors documented that Quecus coccifera acorns could not replace diets barley over than 50% of concentrate with an oat hay basal diet, beyond this level, there is a significant reduction of in vitro gas production which may indicate a decrease in microbial activity. Similarly, it has been demonstrated that the increasing level of oak acorns in the diet to 300g kg-1 feed might be responsible for the reduction in methane production due the inhibitory impact of oak acorns on rumen protozoa population (Aghamohamadi et al., 2014). Experimenting oak leaves, Doce et al., (2007), reported a negative impact of oak Quercus pyrenaica leaves on in vitro ruminal fermentation of conventional feeds (hay) depending on the dose administrated to the animals. The same authors suggested an adaptation to tanniniferous feeds by the rumen microbial population in Brown Swiss bulls consuming oak leaves, which may be beneficial for cattle being fed on tannin-rich forages. They concluded these findings when they noticed a significant decrease in lag time and a significant increase in in vitro DM disappearance of oak leaves incubated for 24h in rumen fluid from bulls fed on either 2.5Kg or 5.2 Kg of oak leaves per day (51.62 and 51.16%) respectively as compared to in vitro DM disappearance in rumen fluid from bulls fed on control diet (43.12%). In vivo digestibility Studies on the effect of feeding oak acorns or leaves on digestibility of dry matter, organic matter and crude protein have yielded different results Table (4). A significant reduction was noticed by Al Jassim et al., (1998), Gasmi-Boubaker et al., 90 Mesopotamia Journal of Agriculture, Vol. 51, No. 4, 2023 (86-105) (2007) and Hidayet and Mustafa (2020a). While, Jafari et al., (2018) found a significant increase in digestibility of dry matter as shown in Table (4). Likewise, (Narjisse et al., 1995) reported that using tannin methanol extract of acorns as infested intraruminally at a rate of 0.1% of live body weight caused no effect on in vivo dry matter digestibility coefficient of Moroccan Timahdit rams and Moroccan native goats which were being fed ad libitum on chopped hay. It has been reported that the dry matter digestibility coefficient of several oak acorn species ranges between 5789% (Kirkpatrick, and Pekins, 1989). Concerning the digestibility coefficient of crude fiber, no significant differences had been reported. Table (3): Effect of oak acorns or leaves on in vitro total gas production. DM: dry matter, OM: organic matter. Different letters within the column of each reference show significant difference. Sharma et al., (2008), suggested that the higher amount of non-structural carbohydrates in mature oak leaves may be supportive in supplementing degradable Part of Treatments oak used Acorns Control 100g kg-1 feed 300g kg-1 feed P value Acorns Control (hay+ barley) Hay+25%acorns +75%barley Hay+50%acorns +50%barley Hay+75%acorns +25%barley Hay+ acorns Leaves Total production gas Findings 452.62ml g-1 OM 463.40ml g-1 OM 455.70ml g-1 OM 0.48 69.6aml 300 mg-1 DM 68.6aml 300 mg-1 DM 69.8aml 300 mg-1 DM 66.2bml 300 mg-1 DM 64.5bml 300 mg-1 DM <0.01 (grass 221.9 ml g-1 OM P value Control hay) 333g kg-1 DM 500g kg-1 DM Reference No effect of including Aghamoham oak acorns up to 300g adi et al., kg-1 feed on in vitro (2014) total gas production. No effect of replacing Moujahed et barley in ration with al., (2007) acorns up to 50%, but when 75% or 100% of barley in the diet was replaced by acorns, a significant reduction was noticed in in vitro total gas production. No effect of inclusion Doce et al., of oak leaves in the (2007) 227.2 ml g-1 OM diet up to 500g kg-1 231.4 ml g-1 OM DM on in vitro total gas production. energy source for microbial protein synthesis in the rumen. It is documented that oak leaves and acorns contain tannins by both types; hydrolysable and condensed tannins. 91 Mesopotamia Journal of Agriculture, Vol. 51, No. 4, 2023 (86-105) Table (4): Digestibility of oak acorns included diets by ruminant animals. Species Part of oak fed No. Level of acorns in diet Digestibility coefficient g kg-1 DM DM OM CP Finding Goats Acorn 21 Control 100 g kg-1 DM without polyethylene glycol 100 g kg-1 DM and 20 g/d polyethylene glycol P value 440 a 360 a No effect of feeding acorns at the level of 100g kg-1 DM on DM and OM digestibility in goats was found, but addition of 20g of polyethylene glycol on the same level of acorns significantly increased both mentioned parameters. A significant reduction in CP digestibility was noticed due to the treatment without polyethylene glycol. A significant increase in OM digestibility was found after feeding goats on acorns at the level of 400g kg-1 DM, while a significant decrease in CP digestibility was noticed by feeding acorns at the levels of 200 or 400g kg-1 DM. A significant reduction in digestibility of DM, OM and CP was reported in goats upon feeding them on 600g of acorns/head/day. A significant reduction in digestibility of DM, OM and CP was shown in sheep consuming acorns at the level of either 250 or 500g kg-1 feed. Goats Goats Sheep Sheep Sheep Goats Acorn Acorn Acorn Acorn Acorn Leave 50 10 30 8 15 410 a 340 a 650a 470b 510 b 490 b 700a <0.01 <0.01 <0.01 673a 694a 725a 694b 584b 451b 0.07 <0.01 Control 200g kg-1 DM 400g kg-1 DM P value Control 600g head-1 P value 680a 567b <0.05 707a 579b <0.05 667a 532b <0.05 Control 250g kg-1 feed 500g kg-1 feed P value Control 50g kg-1 feed 100g kg-1 feed 150g kg-1 feed P value 787a 717b 810a 737b 740a 690b 660c 683c 633c <0.01 805a 762ab 710bc <0.01 834 795 753 <0.01 774 735 693 727bc 766 726 0.05 0.08 0.37 Control 100g kg-1 feed 300g kg-1 feed P value 750 720 739 602 604 492 691 540 356 >0.05 >0.05 >0.05 Control 250g kg-1 feed 500g kg-1 feed 750g kg-1 feed P value 647 575 654 579 538 542 566 572 >0.05 >0.05 A significant decrease in DM digestibility was found in sheep fed on acorns by the levels of 100 and 150g kg-1 feed, while there was no effect of feeding acorns by levels of 50, 100 and 150g kg-1 feed on the digestibility of OM and CP. A numerical decline could be noticed in the digestibility of DM, OM and CP in sheep fed on acorns at the level of either 100 or 300g kg-1 feed, but the decline is statistically insignificant. There was no effect of replacing 250, 500 or 750g of control diet (hay) with same quantity of oak leaves on DM and OM digestibility in goats. Reference Alipanahi et al., (2019) Jafari et (2018) GasmiBoubaker al., et al., (2007) Al Jassim et al., (1998) Hidayet Mustafa, (2020a) and Aghamohamadi et al., (2014) Sevim and Sarı (2014) >0.05 No.: Number of animals in the study, DM: Dry matter, OM: Organic matter, CP: Crude protein. Different letters within the column of each reference show significant difference. Silanikove et al., (1994), demonstrated that the decline in the apparent digestibility coefficient of dry matter in sheep consuming tannin-containing leaves 92 Mesopotamia Journal of Agriculture, Vol. 51, No. 4, 2023 (86-105) may be due to the hydrolysable tannins that act to reduce the cell wall digestibility through inhibiting the activity of rumen microorganisms and their enzymes and/or making indigestible complexes with cell wall carbohydrates. Tannins make complexes with proteins in which prevent the degradation of proteins in rumen leading to increase in the flow of proteins to the intestine and eventually, leading to lower apparent digestibility of crude protein (Patra and Saxena, 2011; McNabb et al., 1996). In other words tannins act to protect the substrate from hydrolysis in rumen in addition to the direct inhibitory effect of tannins on digestive enzymes may explain the negative effects of tannin-containing feeds on the apparent digestibility coefficients of dry matter, organic matter and crude protein ( GasmiBoubaker et al., 2007). In parallel, Wangi et al., (1994) showed that high tannin concentration reduces digestibility of proteins. In goats, there is a superiority for dealing with tannins as compared to sheep and this might be due to the greater ability of microbial population of goats' rumen to degrade tannins (Grenet et al., 1977). Rumen fluid pH and ammonia-nitrogen concentration The rumen fluid pH and ammonia-nitrogen concentration are being used as reliable indicators of nutrient degradation in rumen. The effect of oak on pH value and ammonia-nitrogen levels in rumen fluid is shown in table (5). Alipanahi et al., (2019) concluded that the value of rumen fluid pH was unaffected in lactating multiparous Kurdish goat does being fed on extruded soybean and acorns of Quercus persica at a level of 100g Kg1 DM Table (5). Comparably in sheep, feeding acorns of Quercus persica to Sanjabi rams at levels of 100g kg-1 feed and 300g kg-1 feed did not cause a difference in the value of rumen fluid pH at times before feeding and at 2, 4, 6 and 8 hours post feeding, the pH values ranged from 5.85 to 5.89 (Aghamohamadi et al., 2014). Likewise, no effect of feeding acorns of Quercus aegilos at levels of 50, 100 and 150g kg-1 feed on rumen fluid pH has been noticed in sheep and goats at 2,4 and 6hours following morning feeding (Hidayet and Mustafa, 2020a). Feeding acorns of Quercus persica at a level of 100g Kg-1 feed to lactating multi-parous Kurdish goats breed added to extruded soybean diet exhibited a significant decline in rumen ammonia- nitrogen concentration that was 7.22mg/dL whereas that of control was 10.58mg/dL Alipanahi et al., (2019). Also, goat does in late pregnancy exhibited a significant lessening in rumen ammonia-nitrogen level following consumption of diets containing acorns at rate of either 200g Kg1 feed or 400g Kg1 feed (Jafari et al., 2018). In addition, a significant decline in rumen ammonia-nitrogen concentration was found by Aghamohamadi et al., (2014), when Sanjabi rams were fed on acorns of Quercus persica at rates of 100 g Kg1 feed or 300 g Kg1 feed. In contrast, Hidayet and Mustafa, (2020a) documented a significant increase in rumen ammonia-nitrogen level in bucks consuming a feed containing acorns of Quercus aegilos at the level of 150g kg-1 feed as compared to rams fed on 93 Mesopotamia Journal of Agriculture, Vol. 51, No. 4, 2023 (86-105) either 50 or 150g kg-1 feed after 4hours of morning meal. The same authors revealed that after 6hours post morning feeding, a significant elevation happened in rumen ammonia-nitrogen concentration of bucks fed on acorns at levels 50 and 100g kg-1 feed as compared to that of rams fed on same levels of acorns, and rams fed on 150g kg-1 feed showed a significant elevation as compared to that fed control at 6 hours post morning feeding. Table (5): Effect of oak acorns on pH value and ammonia-nitrogen concentration in rumen fluid. Species No. Level of acorns in diet Goats 21 Control 100g kg-1DM without polyethylene glycol 100g kg-1 DM and 20 g d-1 polyethylene glycol P value Goats 50 Control Time of sampling (h after morning feeding) 3 3 pH NH3N (mg-1 dL) Finding 6.92 6.72 10.58a 7.22b Addition of acorns in the diet of goats to the level of 100g kg-1 DM with or without adding polyethylene glycol by 20g d-1 caused a significant reduction in rumen fluid NH3-N concentration at 3 hours post morning feeding without effect on rumen fluid pH. Addition of acorns at both levels of 200 and 400g kg-1 DM significantly reduced rumen NH3-N concentration in goats at 3 hours post morning feeding. 6.84 9.98a 0.42 <0.01 - 10.61 a 200g kg-1 DM 400g kg-1 DM P value - 7.18 b 5.86 c <0.01 Sheep 15 Control 100g kg-1 DM 300g kg-1 DM P value 8 5.85 5.89 5.85 0.13 8.06a 2.63b 1.54b <0.01 Sheep 8 Control 50g kg-1 feed 100g kg-1 feed 150g kg-1 feed P value 6 6.21 6.24 6.55 6.53 0.1 3.50 a 3.50 a 5.01 b 3.15 a 0.02 In sheep, addition of acorns at both levels of 100 and 300g kg-1 DM significantly reduced rumen NH3-N concentration at 8 hours post morning feeding, while not affecting rumen fluid pH. The rumen NH3-N concentration was reduced when sheep fed on acorns at the level 100g kg-1 feed at 6 hours post morning feeding, while all dietary treatments did not have effect on rumen fluid pH. Reference Alipanahi et al., (2019) Jafari et (2018) al., Aghamohamadi et al., (2014) Hidayet Mustafa, (2020a) and No.: Number of animals in the study, DM; Dry matter, NH3-N: ammonia-nitrogen concentration. Different letters within the column of each reference show significant difference. Milk yield and composition Oak acorns and leaves as available and alternative feedstuffs are used considerably for feeding lactating animals in many regions of the world. Limited literature is available about the effect of oak on milk yield and composition in ruminants. In goats, Alipanahi et al., (2019) demonstrated no effect of feeding oak 94 Mesopotamia Journal of Agriculture, Vol. 51, No. 4, 2023 (86-105) acorns on milk yield and milk components. Differently a significant increase in daily milk yield was reported by Hidayet and Mustafa (2021) and Sameh, et al., (2022) in goats consuming oak acorns within diet Table (6). Table (6): Effect of feeding different levels of acorns on milk yield and constituents. Species No. Level of Milk acorns yield in diet Kg-1 day Milk components (g kg-1 milk) Fat Protein Lactose SNF Finding Goats 21 36.30 33.30 38.10 37.90 55.80 55.60 102.10 101.60 0.45 0.96 0.98 0.87 No effect of feeding Alipanahi goats on acorns at the et al., level of 100 g kg-1 DM (2019) on daily milk yield and milk fat, protein, lactose and SNF components. Goats Goats 24 40 Control 0.26 100 g 0.32 kg-1 DM P value 0.81 Control 50g kg-1 feed 100g kg-1 feed 150g kg-1 feed P value 0.46 a 43.4 0.64ab 37.2 54.9 a 45.1 49.2 ab 44.7 0.51 a 50.7 47.3 ab 44.2 0.86 b 31.6 44.8 b 44.4 0.03 0.2 0.05 0.15 Control 100g kg-1 feed 200g kg-1 feed 250g kg-1 feed P value 0.79 a 1.28 a 30.7 32.4 27.1 28.8 46.7 47.5 1.43 b 37.3 31.4 47.7 2.34 b 39.5 34.5 50.8 0.01 0.30 <0.001 0.46 108.5 a No effects of feeding 101.9 ab acorns at the levels of 50 and 100 g kg-1 feed ab on daily milk yield and 99.1 milk components, but at the dietary level of 150g kg-1 feed a 96.7 b significant increase the daily milk yield was found in goats, with a s 0.05 significant reduction in milk SNF component. There was significant increase in daily milk production in goats fed on rations containing acorns at levels either of 200g kg-1 feed or 250g kg-1 feed. The daily yield of milk fat and lactose and protein components remained unaffected by the treatments. Reference Hidayet and Mustafa, (2021) Sameh et al., (2022) DM: Dry matter, SNF: Solid non-fat. Different letters within the column of each reference show significant difference. Regarding milk composition, a significant reduction was found by Hidayet and Mustafa (2021) in milk solid non-fat component, while no effect of acorns was found by Alipanahi et al., (2019) and Sameh et al., (2022). It was shown by Min et al., (2003) that condensed tannins may increase milk production in ruminants, probably due to their action in increasing essential amino acids absorption in small intestine and due to their inhibitory effects on internal parasites activity. In addition, it was stated by Alipanahi et al., (2019) that feeding 95 Mesopotamia Journal of Agriculture, Vol. 51, No. 4, 2023 (86-105) lactating goats on acorns caused no effect on the concentration of both of acetate and butyrate in rumen fluid and on plasma triglycerides level and these may partly explain why milk fat content is unaffected by dietary acorns, depending on the findings of Mansbridge and Blake, (1997) who demonstrated that milk fat is derived from de novo synthesis using circulatory acetate and butyrate that originate from the rumen and uptake of plasma lipids . Furthermore, it is found that milk protein percentage was not changed by feeding or supplementing oak acorns, this may be attributed partly to the absence of effect of acorns on plasma protein concentrations (Alipanahi et al., 2019). Growth performance The effects of oak on growth rate are demonstrated in Table (7). It has been revealed by Froutan et al., (2015) that rearing Markhoz male goat kids for 105 days of growth period on different levels of acorns (80,170 and 250 g Kg 1 feed), showed no impact of feeding acorns on dressing percentage which ranged between 39.79 and 40.53%, average daily weight gain (152.15g/day), feed conversion ratio (6.41). While it has been noticed in the same study that goat kids fed on dietary levels of containing 170 and 250 g Kg1 feed exhibited a significant lessening in 12th rib fat thickness (2.22 and 2.23mm respectively) as compared to that of control (2.89mm). In another growth trial by Gasmi-Boubaker et al., (2007), a significant reduction was reported in daily weight gain of Boer goat kids that received 600g of Quercus suber acorns and 500g oat hay/head/day resulted as compared to goat kids consuming 600g barley and 500g oat hay/head/day (43g/d vs. 80g/d). In sheep, through an experiment of growth that lasted for 105 days, it is shown that there were no effects of feeding green acorns of Quercus ilex on daily weight gain, while a significant decrease in dressing percentage in Ouled Djella lambs kept on a diet consisting of acorns at level 500g Kg1 feed as compared to those fed on a diet consisting of barley at level 500g Kg1 feed (Keddam, et al., 2010). Comparably, Al Jassim et al., (1998) stated that feeding Awassi growing lambs on a concentrate diet composing of Quercus aegilops acorns at the level of 250g Kg1 feed did not affect the daily weight gain (187.61g/d on average) and feed conversion ratio (4.73 Kg DM/ Kg live body weight gain) Figure (1). Whereas in the same study, the lambs of the other treatment that fed on dietary level of 500g Kg1 feed, exhibited a significant reduction in daily weight gain and feed conversion ration as compared to control (144 vs. 186g/d) and (6.01 vs. 4.68 Kg feed/Kg live body weight gain). conversion ratio. It has been indicated by Hidayet and Mustafa, (2020b) that Awassi lambs fed on dietary treatments of Quercus aegilops acorns at levels of 50, 100 and 150g kg-1 feed, caused in no impact of acorns on dry matter intake, daily weight gain, feed conversion ratio, in addition to carcass characteristics, the shrinkage and dressing percentages were not affected. The authors found a significant increase only in rib96 Mesopotamia Journal of Agriculture, Vol. 51, No. 4, 2023 (86-105) eye area of lambs fed on the treatment 50g kg-1 feed and the group fed on 150g kg-1 feed tended to have a lower feed conversion ratio. Daily weight gain g/d 250 200 Control 150 250g/kg feed 100 500g/kg feed 50 0 Level of acorns in the diet Figure (1): Effect of different levels dietary acorns on daily weight gain of growing Awassi lambs (Al-Jasim et al., 1998) In cattle, Sharma et al., (2008) showed that feeding Zebu calves on a diet consisting of leaves 0f Quercus incana at the ratio of 500g Kg1 feed resulted in a significant increase in average daily gain (386g/d) as compared to that of control group (136 g/d). Also it was reported by Paswan and Sahoo, (2012) that heifers fed on diets composing of grass hay plus oak leaves at levels of either 425 or 630 g Kg1 feed oak led to a significant decline in average daily weight gain as compared to control group heifers which were kept on grass hay solely. It was stated by Froutan et al., (2015), that there are differences among animals species in terms to response among tannin-containing feeds. Morever, Alipanahi et al., (2019) demonstrated that in addition to oak species, different kinds or doses of tannins and interactive effects between tannins and other feed ingredients might be the reasons of differences among the findings of studies. The variation in chemical composition of oak acorns is expected due to species, growing site and stage of maturity ( Gasmi-Boubaker et al., 2007). Blood metabolites The impact of oak on blood metabolites as provided by literature is summarized in Table (8). It is documented in multi-parous lactating Kurdish goat does fed on extruded soybean along with Quercus persica acorns at a level of 100g Kg-1 DM, do not cause a differences in plasma glucose, protein, albumin, cholesterol, and triglycerides levels (Alipanahi et al., 2019). 97 Mesopotamia Journal of Agriculture, Vol. 51, No. 4, 2023 (86-105) Table (7): Effect of dietary oak acorns and leaves on growth performance of goat kids and lambs. Species No. Goats 24 Goats 10 Sheep 10 Sheep 30 Sheep Cattle Cattle 24 15 6 Part of Level in oak diet Acorn Control 80g kg-1 feed 170g kg1 feed 250g kg1 feed P value Acorn Control 600g-1 head P value Acorn Control 400g head-1 P value Acorn Control 250g kg1 feed 500g kg1 feed P value DWG g d-1 146.52 149.02 FCR Finding 6.33 6.52 155.95 6.39 There was no effect of feeding Froutan acorns at the levels of 80, 170 (2015) and 250g kg-1 feed on DWG and FCR in goat. 157.14 6.43 0.17 80.26 43.21 0.97 Acorn Leave Leave Control 50g kg-1 feed 100g kg1 feed 150g kg1 feed P value Control 325g kg1 feed 500g kg1 feed P value Control (Grass hay) 430g kg1 feed 640g kg1 feed P value Reference et al., There was no effect of feeding Gasmi-Boubaker et 600g of acorns to each goat kid al., (2007) on DWG. <0.05 97.28 92.85 There was no effect of feeding Keddam 400g of acorns to each lamb on (2010) DWG. >0.05 186a 189 a 4.68 a 4.79 a 144 b 6.01 b <0.01 <0.01 94.4 117.6 11.44 11.59 99.4 12.26 124.4 8.24 0.39 136 a 300 ab 0.07 - 386 b - 0.04 -50 a - 142 b - 306 c - No effect of feeding acorns at the level of 250g kg-1 feed on DWG and FCR in lambs, but feeding acorns at the level 500g kg-1 feed significantly decreased the DWG, while caused a significant increase in FCR. The were no effects of feeding acorns at levels of 50, 100 and 150g kg-1 feed on DWG and FCR in lambs. et al., Al Jassim et al., (1998) Hidayet and Mustafa, (2020b) Consuming oak leaves at the Sharma level of 325g kg-1 feed had no (2008) effect on DWG in calves, but the level 500g kg-1 feed significantly raised the DWG. et al., Feeding calves on oak leaves on Paswan and Sahoo, both levels of 430 and 640g kg-1 (2012) feed significantly increased the DWG as compared to that of control. <0.001 No.: Number of animals in the study, DWG: Daily weight gain, FCR: Feed conversion ratio. Different letters within the column of each reference show significant difference. 98 Mesopotamia Journal of Agriculture, Vol. 51, No. 4, 2023 (86-105) Table (8): Effect of oak acorns on blood metabolites of ruminants. Species No. Level of acorns in diet Goats 21 Control 100g kg-1 DM without polyethylene glycol OA 100g kg-1 DM and 20 g/d polyethylene glycol P value Control 200g kg-1 DM 400g kg-1 DM P value Goats 50 Goats 24 Goats 24 Control 80g-1 kg feed 170g-1 kg feed 250g-1 kg feed P value Control 50g kg-1 feed Blood metabolite (mg-1 dL) Gl TP Tr Ch 48.8 7.55 13.2 99.2 40.2 71.3 14.4 81.6 44.5 73.6 12.7 86.7 0.25 64.1 a 54.7 b 53.6b <0.01 0.10 71 66 68 0.17 0.66 36 a 22 b 27 b <0.01 0.20 92 100.8 101.1 0.13 70.1 66.4 60.2 60.9 >0.05 44.5 a 57.8 70.1 72.4 71.7 84.6 >0.05 68 74 29.3 23.5 20.8 22.3 >0.05 14 18 66.1 58.7 69.9 58.4 >0.05 - Finding Reference No effect of feeding acorns on the level 100g kg-1 DM with or without polyethylene glycol on blood Gl, Pr, Tr and Ch levels in goats. Alipanahi et al., (2019) In goats being fed on acorns on levels of 200 and 400g kg-1 DM significantly decreased blood Gl and Tr levels, without affecting the blood Pr and Ch concentrations. No effect of dietary acorns levels of 80, 170 and 250g-1 kg feed on blood Gl, Pr, Tr and Ch levels in goats. Jafari et al., (2018) Froutan et al., (2015) The oak acorns fed at Hidayet levels of 50, 100 and and ab 150g kg-1 feed had no Mustafa, effects on blood Gl, Pr, (2021) 100g kg-1 feed 49 b 74 16.2 -1 Tr and Ch levels in 150g kg feed 44.2 72 12.7 ab goats, except the blood Gl concentration P value 0.03 0.65 0.28 which was significantly lowered in goats fed on the oak level of 100g kg-1 feed. No.: Number of animals in the study, Gl: Glucose, TP: Total proteins, Tr: Triglycerides, Ch: Cholesterol. Different letters within the column of each reference show significant difference. Jafari et al., (2018) also reported that goat does at late pregnancy exhibited no effects of consuming acorns at levels of 200 and 400g Kg1 feed on plasma biochemical parameters except for plasma glucose and triglycerides concentrations. The plasma glucose levels of the does receiving acorns were significantly lower than that of control, it was 54.76 and 53.64mg/dL in does received 200 and 400g Kg1 feed respectively, while in does fed on control diet it was 64.18mg/dL. The plasma triglycerides level in does feed on dietary acorns level of 200 and 400g Kg1 feed were 22 and 27.02mg/dL respectively which were lower than that of control (36.06mg/dL). In a study on growing Markhoz male goat kids by, no effects 99 Mesopotamia Journal of Agriculture, Vol. 51, No. 4, 2023 (86-105) of feeding oak acorns at levels 80, 170 and 250 g Kg1 feed were found on plasma glucose, protein, triglycerides and cholesterol concentrations. Differently a significant elevation was found in the concentration of serum globulin (57.8 mg/dL) in lactating Black goats breed at the 10th week of lactation when compared to that of control (44.50mg/ dL) (Hidayet and Mustafa, 2021). Furthermore, no influence of feeding either Karadi rams or Black bucks on acorns of Quercus aegilops at levels of 50, 100 and 150g kg-1 feed were found by Hidayet and Mustafa, (2020a) on serum biochemical metabolites. CONCLUSIONS It could be concluded from the literature reviewed that it is possible to use oak acorns and leaves as feedstuffs in ruminant diets. The degree of the impact of oak consumption depends on the level of oak products in the diet, oak species, type and chemical structure of tannins present in the oak, in addition to animal species. It could be concluded also that goats are more capable than sheep on utilizing oak active materials. ACKNOWLEDGMENT The quality of this work has been enhanced by the authors from the Department of Animal Production at College of Agricultural Engineering Sciences, Department of Pathology and Microbiology at College of Veterinary Medicine, Duhok University. CONFLICT OF INTEREST The authors declare that there is no conflict of interests. ‫ كمال نعمان سيف الدين مصطفى‬، ‫ جالل إيليا القس‬، ‫هوكر مردان خليل هدايت‬ ‫تم في هـذه المراجعة للدراسات السابقة بيان تأثيرات إضافة البلوط في عالئق الحيوانات المجترة على‬ ‫ يستخدم البلوط كعلف بديل ومتوفر في العديد‬.‫األداء وهضم األعالف وإنتاج الحليب وصفات الدم الكيموحيوية‬ ‫ من الواضح ونظ ار الختالف أنواع البلوط‬.‫ وخاصة في المناطق التي تعاني من نقص مواد العلف‬،‫من دول العالم‬ ‫ إن تغذية البلوط بنسب قليلة في تغذية الحيوان قد ال تؤثر‬.‫فان تأثيراته مختلفة على أنواع الحيوانات المختلفة‬ ‫ ولكن عندما يتم تغذيتها بنسب عالية قد تؤدي إلى خفض نسب هضم المادة الجافة وقد‬،‫على عملية الهضم‬ ‫تبين بان إضافة منتجات البلوط قد تؤدي إلى تحسين إنتاج الحليب اليومي للماعز في حين لم تؤدي تغذية ثمار‬ ‫ بينما تغذية األغنام‬،‫البلوط وأوراقها لجداء الماعز الى تحسن في الزيادة الوزنية اليومية وكفاءة التحويل الغذائي‬ 100 Mesopotamia Journal of Agriculture, Vol. 51, No. 4, 2023 (86-105) ‫ ومن المعروف بان األنواع المختلفة‬.‫البالغة بنسب عالية من ثمار البلوط أدت إلى انخفاض الزيادة الوزنية اليومية‬ ‫ تعمل على تكوين بروتينات‬،‫ والتي بعد تناولها من قبل الحيوانات‬،‫من البلوط تنتج كميات مختلفة من التانينات‬ ‫ وقد يؤدي ذلك إلى انخفاض هضم العناصر الغذائية أو قد يؤثر بشكل‬،‫معقدة في الغذاء وبروتينات الجسم‬ .‫ايجابي على تدفق األحماض األمينية إلى المعدة الحقيقية واالمعاء عن طريق تقليل تحلل البروتين في الكرش‬ ‫ فإن مدى تأثير إضافة البلوط الى عالئق المجترات على أداء الحيوانات يعتمد على نوع الحيوان ونوع‬،‫وبالتالي‬ .‫ ونسبته في العليقة‬،‫والبلوط‬ .‫ الماعز‬،‫ األغنام‬،‫ المجترات‬،‫ ثمار البلوط‬:‫الكلمات المفتاحية‬ REFERENCES Abdul-Rahman, S. 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