Determination of some digestibility of nutrients, rumen and blood
metabolites of Akkaraman rams fed low-tannin sorghum and other
conventional feeds
Halit İMİK1, Şakir Doğan TUNCER2, Aylin AYLANÇ3, Melik AYTAÇ3
1 Departments of Animal Nutrition and Nutritional Disorders, Atatürk University, 25700 Erzurum; 2 Departments of Animal Nutrition and Nutritional Disorders, Ankara University, 06110 Ankara; 3Agriculture Minister, Lalahan Live stock Research Institute
Ankara.
Summary: In this study, some blood and rumen metabolites and digestibility of sorghum and other feedstuffs were determined. Four Akkaraman rams weighing 55 kg were fed barley (1200g barley +800 g clover), corn (1200 g + 800 g clover), sorghum (1200 g + 800 g clover), and low quality clover (1200 g) in a 4x4 Latin square design experiment. Each period consisted of 10-day of an adaptation phase and 14-day of a sample collection phase. Blood and rumen samples were collected at the end of sample collection periods. One-way ANOVA with Duncan’s Multiple Range Test was used in data analyses. pH values were 6.62, 6.80, 6.74, and 7.22 and NH3 levels were; 4.38, 3.12, 9.61 and 14.46 mg/dL for rams fed for sorghum, barley, corn and clover, respectively (p<0.05 for both). Nitrogen levels of blood serum were determined were 14.90, 8.55 10.00 and 18.70 mg/dL, respectively, in the same order (p<0.05). There was no significant difference in serum glucose and total protein levels. Apparent digestibilities were 83.06, 85.33, 69.01, and 59.34% for OM and 73.92, 67.92, 31.92, and 63.52 for CP in rams fed sorghum, barley, corn and clover, respectively (p<0.05 for both). There was no difference in digestibility of NDF, ADF and crude ash. In conclusion, due to presence of tannin, sorghum may not be suitable alternative to other grains as sole grain source for small ruminants.
Key words: Digestibility, rams, Sorghum vulgare, tannins
Düşük tanen içeren sorgum ve diğer konvansiyonel yem maddeleri ile beslenen Akkaraman koçlarda, bazı kan ve rumen metabolitleri ile besinlerin toplam sindiriminin belirlenmesi
Özet: Bu çalışmada arpa (1200 g arpa + 800g yonca), mısır (1200 g mısır + 800g yonca), düşük tanen kapsayan (%0.7) Sorgum vulgare (1200 g sorgum + 800g yonca), ve düşük kaliteli yoncanın (1200 g yonca) bazı kan ve rumen parametreleri ile toplam besin maddelerinin sindirilme oranları belirlenmiştir. 4x4 Latin kare metodu ile yapılan klasik sindirim denemesinde ortalama 55 kg canlı ağırlığında 4 adet Akkaraman koç kullanılmıştır. Denemenin her periyodu 10 günü alıştırma 14 günü yedirme ve numune toplama olmak üzere toplam 96 gün devam etmiştir. Kan ve rumen numuneleri araştırma peryotlarının sonunda alınmıştır. Rumen pH’sı ve NH3 düzeyleri arpa, mısır, sorgum ve yoncanın sırasıyla, 6.62, 6.80, 6.74, 7.22; 4.38, 3.12, 9.61, 14.46 mg/dl olarak belirlenmiştir. Her iki parametrede de yoncanın değerleri diğer yemlerden; NH3 değerinde ise sorgumun arpa ve mısırdan yüksek olduğu görülmüştür (p<0.05). Kan serumu nitrojen oranı ise aynı sırayla 14.90, 8.59, 10.00 ve 18.70 mg/dl olarak belirlenmiştir (p<0.05). Glukoz ve total protein arasında önemli bir farklılığın olmadığı görülmüştür. Gübre numunelerinden hayvanların besin maddelerini sindirme dereceleri hesaplanmıştır. Bu besin maddelerinden organik maddenin, ham proteinin ve ham yağın sindirilme dereceleri yukarıdaki sırayla % 83.06, 85.33, 69.01, 59.34; 73.92, 67.92, 31.92, 63.52; 73.34, 90.19, 69.49, 67.06 olarak tespit edilmiştir (p<0.05). Düşük düzeyde tanen içeren sorgumun ham protein sindiriminin önemli derecede düşük olduğu belirlenmiştir (p<0.05). NDF, ADF ve ham kül sindirimleri arasında önemli bir farklılığın olmadığı görülmüştür. Sonuç olarak düşük düzeyde tanen içeren sorgumun ham besin maddelerinin sindirimini olumsuz yönde etkilediği kanısına varılmıştır.
Anahtar sözcükler: Sindirim, Sorghum vulgare, tanen, toklu.
Introduction
Tannins are polyphenolic compounds of plant-origin feedstuffs and are present in two distinct types: hydrolysable tannins and condensed tannins. Tannins that are present in different levels in fodder (0.07-12.53 %) decrease digestibility of feeds (4, 18). Tannins make strong chemical complexes with proteins, sugars and starches that are stable over a pH ranging from the neutral environment of the rumen to acidic conditions in
the stomach. Moreover, tannins directly affect digestibility of plant cell walls by binding to microbial enzymes in the rumen. Tannins may further reduce digestibility of cell wall carbohydrates by forming indigestible complexes with cellulose and hemicellulose (3, 5, 7, 17, 18).
Sorghum may be suitable for animal nutrition. Crude protein, crude fat, crude cellulose, crude ash, total sugar and starch contents of sorghum (Sorghum vulgare)
were reported be to 12.4, 3.2, 2.7, 2.1, 79.6 and 1.5%, respectively (24). In another report (21), chemical composition of Africa sorghum was reported to contain 70% carbohydrate, 12 % protein, 3% fat, 2 % fiber and 1.5 % ash. A similar analytical chemistry conducted on sorghum in Turkey estimated crude protein, crude cellulose, crude fat and ash levels of 11.32, 7.14, 5.61 and 3.25%, respectively (14).
Effects of tannin on rumen metabolism differ among animal species. Maximum tannin tolerance level is 9, 3, and 1% for goats, cows, and chickens, respectively (8). Guar and Taparia (12) fed sorghum to cows, goats, and sheep ad libitum and reported that average daily dry matter intake per 100 kg body weight gain for cows, goats and sheep was 2.85, 3.17 and 4.41 kg, respectively. Moreover, they reported that digestibilities were 31.10, 33.52, and 28.12% for dry matter and were 1.08, 3.23, and 1.28% for crude protein in cows, goats, and sheep, respectively. The rumen retention period for sorghum was 110.7, 117.5 and 102.7 h for the animals, accordingly. The aim of this study was to compare the effects of low-tannin sorghum (0.7%) with barley and corn on some blood rumen parameters and nutrients digestibility.
Material and Methods
This experiment was conducted in Lalahan Animal Research Institute, Ankara. Four Akkaraman rams at age of 2,5 years old and having an average of 55 kg live weight were used. Animals were fed four different rations in a 4*4 Latin square design. Each experimental stage lasted 24 days. Each stage consisted of 10 days of the adaptation period and 14 days of the sample collection period. Thus, total experimental duration was 96 days.
Sorghum, barley, and maize given a concentrate portion of ration and clover a roughage portion of ration were analyzed for nutrient contents. Dry matter, organic matter, crude protein, crude fat and crude ash contents of feeds were determined according to A.O.A.C (2). Neutral detergent fiber and ADF values were determined using methods outlined by Van Soest and Robertson (33). Additionally, sorghum was subjected to tannin analysis using spectrophotometer by Folin-Denis solutions (2).
In clover-based diet, animals were offered to consume clover alone 1200 g/day, in the other experimental diets, sorghum, barley and maize was given 1200 g/day plus 800 g/day clover. During the adaptation period, feed consumptions of animals were determined at 80% of given ration during the sample collection period. The digestion level of this nutritive substances was found by determining the difference.
The contents of vitamin-mineral mixture added into animal rations: Per 5 kg of vitamin-mineral premix (Tarvan Katık SB-5) contained; vitamin A, 6667 IU;
vitamin D3, 667 IU; vitamin E, 5.0 mg; Ca, 0.9 g; P, 0.6 g; Mg, 0.15 g; Se, 125 mg; I, 0.4 g; Co, 0.3 g; Fe, 25.0 mg; Cu, 5.0 mg; Zn, 30.0 mg; Mn, 25.0 mg, and S, 36.0 mg.
Fresh and clean water was offered all times during the experimental period. Each of fecal samples were collected daily via special bags and their weights were recorded during the sample collection period. Then, 10% of fecal samples were collected in polyethylene bags to store in freezer for further analyses. After sorting samples by animal, they were mixed by period and group in a large basin. Following homogenization, samples were dried at 65oC for dry matter level and then used for
determinatio of nutrient concentrations. At the end of each period, rumen fluids were collected at 0, 2, 4, and 6h
hours post-feeding relative to feeding for determination of pH using a digital pH meter (Orion Research model Sa 210) and ammonia concentration using a commercial kit (Sigma Co, 640B) by the spectrophotometric method (Shimadzu UV 2100). On times rumen samples harvested, blood samples obtained for analyses of glucose, total protein, and BUN.
Data were analyzed as a 4x4 Latin square design experiment using one-way ANOVA of SPSS (30). The linear model included the effect of ram, diet, and period. In comparison of the effects of feedstuffs, Duncan Multiple range option was applied to attain statistical significance (p<0.05).
Results
Chemical composition of sorghum and other conventional feedstuffs are present in Table 1.
Table 1: Chemical composition of sorghum and conventional feedstuffs (% of dry matter basis).
Tablo 1. Sorghum ve konvansiyonel yemlerin kimyasal bileşimleri (% kuru maddede)
Variable1 Barley Corn Sorghum Alfaalfa
OM 88.8 86.85 88.47 91.31 CP 12.45 8.61 12.59 10.46 NDF 37.5 16.35 37.47 62.49 ADF 10.13 6.63 18.83 59.49 EE 2.38 2.44 3.83 1.6 Ash 2.44 1.36 2.74 6.0 Total tannin - - 0.7 -
1Variable: OM= organic matter; CP= crude protein; NDF= neutral detergent fiber; ADF= acid detergent fiber, EE= ether extract. OM: organik madde, HP:ham protein, NDF: nötral detergent fibre, ADF: asit detergent fibre, HY:ham yağ, HK: ham kül,
The rumen pH values were higher for the clover diet than for the barley, maize and sorghum diets (p<0.05). There was no significant difference in pH values of rams fed sorghum, barley, and maize (p>0.05;Table 2). Different fodder used in the present study affected the rumen pH value according to time (p<0.05). The rumen pH decreased quickly in two hours after feeding, decrease slowed down between 2-4th, and
Figure 1. Changes in rumen pH of sheep fed barley (♦), corn (■), sorghum (▲), and alfalfa (●)-based diets. Probability of significance for time and treatment by time interaction were 0.0001 and 0.61. SEM was 0.125.
Şekil 1: Koyunlara verilen arpa (♦), mısır (■), sorghum (▲), ve yoncanın (●) rumen pH sı üzerine etkisi. Zamanın etkisi (P < 0.0001), interaction: 0.61, SEM:1.25.
Table 2. Effect of diets on rumen and blood parameters1. Tablo 2. Yemlerin rumen ve kan parametreleri üzerine etkisi1
Treatment2 Variable3 1 2 3 4 SEM4 Rumen pH5 6.62c 6.80b 6.74bc 7.22a 0.06 NH3, mg/dl6 4.38c 3.12c 9.61b 14.46a 0.65 Blood Glucose, mg/dl 67.94 64.35 65.18 56.58 4.63 BUN, mg/dl 14.90ab 8.59c 10.00bc 18.70a 1.98 Total protein, mg/dl 6.22 6.03 6.58 6.51 0.41 1 Differnt superscripts within the same rows differ (p< 0.05). 2 Treatment: 1 = barley-based diet, 2 = corn-based diet, 3 =
sorghum-based diet, 4 = alfalfa-based diet. 3Variable: BUN = blood urea nitrogen. 4Standard error of a mean. 5Time effect,
p <0.0001. 6Time effect, p<0.004.
Figure 2. Changes in rumen NH3 concentration of sheep fed barley (♦), corn (■), sorghum (▲), and alfalfa (●)-based diets. Probability of significance for time and treatment by time interaction were 0.0001 and 0.21. SEM was 1.31.
Şekil 2: Koyunlara verilen arpa (♦), mısır (■), sorghum (▲), ve yoncanın (●) rumen NH3 konsantrasyonundaki değişiklikler. Zamanın etkisi (P < 0.0001), interaction: 0.21, SEM:1.31.
Rumen NH3 concentration of rams fed clover was
greater found higher than the rams fed other fodders. Moreover, rams fed sorghum had greater ruminal NH3
concentration than those fed barley and maize (p<0.05; Table 2). Rumen NH3 value was the highest at 2 hours
after feeding and then gradually decreased (p<0.01; Figure 2).
There were no significant differences in serum total protein and glucose concentrations among rams fed low-tannin sorghum and other fodders (p>0.05). Blood urea nitrogen concentration of rams fed sorghum was lower than those fed clover, corn, and barley (p<0.05). However, difference in BUN concentrations of rams fed sorghum, barley, and corn were not significant (p>0.05) (Table 2).
The digestibilities of OM, CP, NDF, ADF, EE and ash are summarized in Table 3. OM digestibility of sorghum and clover was lower than barley and corn (p<0.05). There was no significant difference in OM digestibility values for barley and maize.
The apparent CP digestibility of sorghum was lower than that of barley, corn, and clover diets. Apparent CP digestibilities were 31.92, 73.92, 67.92, and 63.52 %, respectively. Neutral detergent fiber digestibility in total tract was not affected by the feedstuffs. Total tract ADF and ash digestibility were not different (p>0.05) across the feedstuffs, although the value for sorghum tended to be lower (Table 3).
Table 3. Effect of diets on digestibility of nutrients1. Tablo 3. Rasyondaki besin maddelerinin sindirilme oranları1
Treatment2 Variable 1 2 3 4 SEM3 OM 83.06a 85.33a 69.01b 59.34 b 3.71 CP 73.92a 67.92a 31.92 b 63.52 a 4.11 NDF 67.55 51.70 50.59 53.58 5.82 ADF 44.30 45.11 30.02 51.65 6.94 Ash 51.61 55.84 33.99 47.86 6.82
1 Differnt superscripts within the same rows differ (p<0.05). 2 Treatment: 1 = barley-based diet, 2 = corn-based diet, 3 =
sorghum-based diet, 4 = alfalfa-based diet.
3 SEM:Standard error of a mean. OM= organic matter; CP= crude protein; NDF= neutral detergent fiber; ADF= acid detergent fiber, EE= ether extract.
a,b,: Aynı satırda farklı harfi taşıyan değerler birbirinden farklı bulunmuştur (P < 0.05).
Gruplar: 1 =arpa, 2 = mısır, 3= sorghum, 4 =yonca.
Besin maddeleri: OM= organik madde; HP=ham protein; NDF= nötral detergent fiber; ADF= asid detergent fiber; HY= ham yağ.
Discussion and Conclusion
In this study, rumen pH, ammonia, blood serum glucose, blood urea nitrogen, total protein values for sorghum, barley, maize and clover as well as digestibility of nutrients were determined. Jacob et al (15) evaluated
nutritive value of sorghum varieties and reported that they contained 71-107 g.kg-1 CP, 31-36 g.kg-1 EE, and
1.4-19 g.kg-1 ash. Streetere et al. (32) reported that CP
contents of sorghum varied between 10.3-13.2%. Similarly, Reddy and Rao (25) reported that sorghum varieties contained 10.0-14.1% CP, 1.8- 5.7% EE, and 1.77-3.60% ash. With respect to CP level, nutritive value of sorghum measured in the present study was greater than results reported by İmik and şeker (14), Jacob et al(15), NRS (21), Pond et al (24) but in agreement with those reported by Reddy and Rao (25) and Streetere et al (32 ). Food components of sorghum vary according to some factors including type, variety, country, and climate (9, 21, 24). As shown in Table 1, low-tanning sorghum could be replaced in ruminant diets as alternatives to barley and maize. Additionally, sorghum is more drought resistant than other grains, which could be crucial for semi-arid areas (21, 24).
Tannin content of sorghum is also highly variable particularly depending upon type and variety. Jacob et al (15) reported that tannin content in brown sorghum was 2.0-2.3 g/kg while tannin content in white sorghum lacked. Streetere et al (32) stated that waxy-bird resistant sorghum contained 1.24-catechin equivalent tannin, whereas normal-bird resistant sorghum contained no tannin. Lizardo et al (16) found tannin content of sorghum as 1.6-40.1 g/kg, whereas Al- Mamary et al (1) found tannin content of sorghum as 1.4-3.5%. Tannin is generally present in cortex of sorghum (24). Imik and Şeker (14) reported that tannin content of whole sorghum grain was 2.72%. Tannin content of sorghum fed in the present study (0.7%) was lower than that fed in some studies (1, 14, 16), but was greater than some other studies (15, 32).
Regarding rumen pH in responses (Table 2) to feedstuffs used in the present experiment, our results are in agreement with those reported by Stock et al (31) who used sorghum in rations at ratios of 0, 25, 50, 75%, obtaining decreased the pH values (6.21, 5.80, 5.75, 5.59). Low-tannin sorghum was not detrimental to rumen fluid pH value. Diurnal variation in rumen fluid pH observed in this study (Figure 1) is typical. Chiquette et al (10) fed ewes Lotus corniculatus 1,2 and 3,2% to tannin. They reported that rumen fluid pH was 7.4, 6.7 and 6.5 at 0, 3, and 6 hours past feeding.
Rumen NH3 values obtained in this study (Table 2)
are different from those reported in the literature. In cattle, Spicer et al (29) found that sorghum, corn, barley had 157.2, 148.5, and 148.6 g/d non-ammonia N and 6.5, 5.0, and 6.6 g/d ammonia N in abomasum, respectively. Differences could be resulted from the different animal species that used as research material. In a similar study, Chiquette et al (10) reported that rumen NH3 levels of
ewe’s fed high-tannin (3.2%) Lotus corniculatus were 9.8, 9.8, and 10.4 mM and of those fed low-tannin (1.2%) Lotus corniculatus were 9.5, 12.4 and 12.2 mM at 0, 3 and 6 hours after feeding, respectively. However, this could not be true when to feed low-tannin sorghum, suggesting that low-tannin may not interfere with ruminal fermentation.
Tannin affects utilization of nutrients in sorghum. Stock et al (31) reported that energy digestion for dry-rolled grain sorghum and dry-dry-rolled corn was 85.4 and 92.8%, respectively. In the present experiment, it appears that low-tannin has no effect on rumen and blood parameters, suggesting that ruminal fermentation of starch from barley, corn, and low-tannin sorghum was similar. Waghorn et al.(35) reported that energy digestion were significantly decreased by feeding 22g /kg CT consisting Lotus corniculatus to ewes. Metobolizable energy values were reported to range from 0.89-0.77 MJ/kg live weight in ewes fed diet containing lotus with 45.6-105.9 g/kg CT (6). High tannin forms non- digestible compound with starch and interferes with its digestion (7, 29, 35). Numerous researchers (6, 20, 35) concluded that presence of 2-10.5% tannin significantly decreased energy digestion, as seen in the present study, however differences could be related to differences in animals used (12).
Regarding BUN levels, sorghum had no effect (Table 2). Waghorn et al (34) reported that denaturation of tannin by polyethylene glycol (PEG) increased plasma NH3 level from 219 µg/ml to 310 µg/ml. In another study
(20) feeding alfalfa and oak browse control (alfalfa), 40% mature oak, 80% mature oak and 80% immature oak resulted in N digestibilities of 73.2, 60.2, 48.6 and 50.8%, respectively, indicating that presence of tannin adversely affect N utilization and may raise BUN concentration (20, 34). In the this study, a lack of change in BUN concentration could be due to presence of low-tannin in sorghum.
Anti-nutritive effect of tannin is related to its complexing with proteins and polysaccharides. Adaptation ability to sorghum differs among animal species (12). Barry and Duncan (6) stated that decreasing tannin content by PEG addition to Lotus pedunculatus increased digestibility from 0.547 to 0.627. In other study (5), PEG addition to Desmodium ovalifolium decreased CT content from 90 to 50 g/kg and increased OM digestion from 36.1 to 43.5% while total digestibility increased slightly. Possibly, due to low-tannin content, our results were in agreement with literature in terms of OM digestibility. Despite containing relatively high tannin (1.2-3.2%), OM digestibility was not affected in ewes fed Lotus corniculatus (about 70%) (10) and sorghum (about 80%) (29).
The ability of tannins to farm strong insoluble complexes with proteins that are resistant to stomach pH is the most important aspect of their nutritional and toxicological effects (13, 19). Tannins have a large number of free phenolic hydroxyl groups that form strong hydrogen bonds with proteins and carbohydrates. Tannins may also complex with proteins through hydrophobic bonding (19, 22). When animals forage on tannin-rich plants, tannin-protein complexes can reduce the digestion of forage protein. In agreement with the present study, Bell and Keith (9) found that protein from sorghum grain was less digestible than that from wheat and hulless barley (65.5, 78.9, and 76.5%, respectively). As compared with corn and barley, the total tract crude protein digestibility of sorghum grain is low (23, 27).
The effect of tannins on retarding fiber digestion is regarded as a secondary anti-nutritional effect as compared with nitrogen digestion (7, 18, 28). Tannins may reduce cell wall digestibility by binding bacterial enzymes and or forming indigestible complexes with cell wall carbohydrates (26). In this study, digestibility of, NDF ADF and ash was not affected by low-tannin (Table 3). Gaebe et. Al (11) found no significant differences in apparently digestibility NDF and ADF between corn and sorghum. Oliveria et al. (23) and Santos et al. (27), also showed that no significant differences in apparent digestibility NDF and ADF in cows fed steam-rolled corn and dry-rolled sorghum.
In conclusion, the present findings suggest that sorghum vulgare was a good feedstuff regarding its nutritive contents and also its low tannen content had no adverse effect upon ruminal pH, NH3, serum glucose,
total protein and BUN. However, as the digestion of feedstuff may be affected adversely when the content sorghum’s tannen content exceed 0.7 %, it is recommended that sorghum should not be used as the only conventional feedstuff instead of barley and corn.
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Geliş tarihi: 05.10.2007 / Kabul tarihi: 27.03.2008
Address for correspondance
Dr.Halit İmik Atatürk Üniversitesi Veteriner Fakültesi 25700 Ilıca/Erzurum e-mail: himik@atauni.edu.tr
