The nutritive value of hemp meal for ruminants

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1 The nutritive value of hemp meal for ruminants A. F. Mustafa, J. J. McKinnon, and D. A. Christensen Department of Animal and Poultry Science, University of Saskatchewan 72 Campus Drive, Saskatoon, Canada S7N 5B5. Received 24 March 1998, accepted 23 December Mustafa, A. F., McKinnon, J. J. and Christensen, D. A The nutritive value of hemp meal for ruminants. Can. J. Anim. Sci. 79: Hemp meal (HM) is derived from the processing of hemp (Cannabis Sativa L.) seeds. The objective of this study was to determine the nutritive value of HM for ruminants. Two ruminally fistulated cows were used in a randomized completeblock design to estimate in situ ruminal dry matter (DM) and crude protein (CP) degradability of HM relative to canola meal (CM), heated canola meal (HCM) and borage meal (BM) meal. Intestinal availability of rumen undegraded CP was estimated using a pepsin pancreatin in vitro assay. Twenty growing lambs were utilized in a completely randomized design to determine total tract nutrient digestibility coefficients of diets in which HM replaced CM at 0, 25, 50, 75 and 100% as a protein source. Results of the in situ study showed that the soluble-cp fraction of HM was similar to that of HCM and lower (P < 0.05) than those of CM and BM. Rate of degradation of the potentially degradable CP fraction and effective CP degradability of HM was higher (P < 0.05) than HCM and lower (P < 0.05) than CM and BM. Rumen undegraded CP and intestinal digestibility of RUP were highest (P < 0.05) for HM and HCM (average and g kg 1 of CP, respectively), intermediate for CM (473.9 and g kg 1 of CP, respectively) and lowest for BM (401.5 and g kg 1 of CP, respectively). However, total available CP was similar for the four protein sources (average g kg 1 of CP). Feeding up to 200 g kg 1 HM did not affect voluntary intake or total-tract nutrient digestibility coefficients for sheep fed a barley-based diets. Hemp meal is an excellent source of RUP, with high post-ruminal availability, and may be used to replace CM with no detrimental effects on nutrient utilization by sheep. Key words: Hemp meal, nutritive value, ruminants Mustafa, A. F., McKinnon, J. J. et Christensen, D. A Valeur nutritive du tourteau de chanvre pour les ruminants. Can. J. Anim. Sci. 79: Nous avons cherché à établir la valeur nutritive pour les ruminants du tourteau de chanvre (TCh), qui est le résultat de la trituration des graines de cette plante, Cannabis sativa L. Deux vaches munies d une fistule ruminale ont servi, selon un dispositif expérimental en blocs aléatoires complets, à évaluer la dégradabilité ruminale in situ de la matière sèche (m.s.) et des protéines brutes (PB) du tourteau de chanvre, en regard de celle du tourteau de canola ordinaire (TC) ou chauffé (à 125 C pendant 10 min) TCC ainsi que du tourteau de bourrache (TB). La disponibilité intestinale des PB non dégradées dans le rumen était dosée au moyen d un test in vitro à la pepsine-pancréatine. Vingt agneaux en croissance étaient utilisés selon un dispositif expérimental complètement aléatoire, pour déterminer les coefficients de digestibilité des nutriments sur l ensemble de l appareil digestif des régimes alimentaires dans lesquels TCh remplaçait TM comme composant protéique dans les proportions de 0, 25, 50, 75 et 100 %. Les résultats de l expérience in situ montrent que la fraction de PB soluble du TCh était semblable à celle du TCC et était inférieure à celle mesurée pour TC et pour TB. Le taux de dégradation de la fraction des PB éventuellement dégradables et la dégradabilité effective des PB de TCh étaient plus élevés (P < 0,05) que chez le tourteau de canola chauffé, mais inférieurs (P < 0,05) aux valeurs obtenues pour TC et pour TB. La fraction de PB non dégradée dans le rumen (PNDR) et sa digestibilité dans l intestin atteignait les valeurs les plus fortes (P < 0,05) pour TCh et TCC (moyenne respective de 782,5 et 644,5 g kg 1 de PB) intermédiaires pour TC (473,9 et 342,9 g kg 1 de PB) et les plus faibles pour TB (401,5 et 242,3 g kg 1 PB). En revanche, la quantité de PB disponible totale était la même pour les quatre tourteaux, soit en moyenne 857,8 g kg 1 de PB. Un taux d inclusion de TCh dans la ration allant jusqu à de 200 g par kilo n influait pas sur le taux d ingestion libre ni sur les coefficients de digestibilité totale des nutriments chez les moutons recevant des aliments à base d orge. Le TCh est une excellente provenance de PNDR, dotée d une forte disponibilité post-ruminale. Il pourrait donc remplacer le TC sans effet adverse sur la valorisation des nutriments par les moutons. Hemp (Cannabis sativa L.) is an annual herbaceous plant belonging to the family Cannabinaceae (Turner et al. 1980). Traditionally, hemp is grown as a fiber crop in areas with temperate climates. Hemp seeds are also a valuable commodity. The seed contains 30 to 35 g kg 1 oil, 80% of which is polyunsaturated fatty acids (Deferne and Pate 1996). Hemp-seed oil can be used in cooking or in industrial products such as paint, detergents and lubricants. As with other oilseeds, mechanical or solvent extraction of hemp seed produces a meal that is high in protein and low in oil, relative to the seed. On a DM basis, HM contains 345 g kg 1 CP, 26.8 g kg 1 CF, 89 g kg 1 ash and 96 g kg 1 ether extract Mots clés: Tourteau de chanvre, valeur nutritive, ruminant 91 (Gohl 1993). If an oil-extraction industry is to be economically viable, a market must be found for the residual meal. The relative high fiber of the meal indicates that it may be Abbreviations: ADF, acid detergent fiber; ADL, acid detergent lignin; BM, borage meal; BW, body weight; CM, canola meal; CP, crude protein; DM, dry matter; DMI, dry matter intake; EDDM, effective degradability of DM; HCM, heated canola meal; HM, hemp meal; NDF, neutral detergent fiber; OM, organic matter; RUP, rumen undegraded CP; SEM, standard error of the mean

2 92 CANADIAN JOURNAL OF ANIMAL SCIENCE used most efficiently as a protein supplement for ruminants. Very little research has been conducted, however, on the nutritive value of HM for ruminants. The objectives of this study were to determine ruminal nutrient degradability of hemp meal relative to common protein sources and to determine the total-tract nutrient digestibility of diets containing graded levels of HM. MATERIALS AND METHODS In Situ Study Hemp meal was obtained from the Western Grower Seed Corporation, Saskatoon, Saskatchewan. Samples of CM, HCM and BM were included for comparison. The HCM (heated at 125 C for 10 min) and the BM were those used in a previous study (Mustafa et al. 1997a). Samples of the four protein sources were analyzed for moisture, ash, ether extract, CP, ADF and ADL according to the procedures of the Association of Official Analytical Chemists (AOAC 1990). Neutral detergent fiber was determined according to the procedure of Van Soest et al. (1991). Neutral and acid detergent insoluble CP were determined on NDF and ADF residues, respectively (AOAC 1990). Soluble CP and nonprotein nitrogen were determined as described by Licitra et al. (1996). Two non-lactating Holstein cows fitted with flexible rumen fistulae were used. The cows were fed a 50:50 barley silage/concentrate diet twice daily at 1.5% BW (DM basis). The concentrate diet contained 755 g kg 1 barley, 170 g kg 1 CM, 20 g kg 1 corn gluten meal, 5 g kg 1 canola oil, 6 g kg 1 dicalcium phosphate, 3 g kg 1 cobalt-iodized salt, 1 g kg 1 ground limestone and 30 g kg 1 mineral vitamin mix. Seven grams of each protein meal was weighed in duplicate into nylon bags (9 21 cm; 41-µm pore size). The bags were then placed into polyester mesh bags (25 33 cm) and incubated in the rumen of each cow for 4, 8, 12, 18, 24, 48, 72 and 96 h. Incubations commenced prior to the morning feeding with bags inserted at the appropriate time, such that all were removed with bags incubated for 96 h. Following removal from the cows, the bags were washed and handled as described by McKinnon et al. (1991). Bags containing unincubated samples of the four protein meals were washed at the same time to estimate zero-hour disappearance. The washed bags were then dried in a forced-air oven at 55 C for 48 h and allowed to air equilibrate for 3 d. Ruminal DM and CP disappearance at each incubation time were calculated from the DM and CP content of the original samples and the residues following rumen incubation. Ruminal DM and CP disappearance data were used to estimate DM and CP kinetic parameters using the equation of Ørskov and McDonald (1979): P = a + b (1 e ct ) where P is DM or CP disappearance at time t (h), a is the rapidly soluble fraction (g kg 1 ), b is the potentially degradable fraction (g kg 1 ) and c is the rate of degradation (% h 1 ) of the b fraction. The constants a, b and c were estimated by an iterative least-square method using the nonlinear regression procedure of the SAS Institute, Inc. (1989) with the constraint that a + b 100. Intestinal Digestibility of Rumen Undegraded Protein Rumen undegraded CP was calculated as the ratio of residual CP from the 12 h rumen incubation to the original CP (Ham et al. 1994). Post-ruminal availability of RUP was determined following the in vitro three-step procedure of Calsamiglia and Stern (1995). Sample residues from the 12- h rumen incubation containing 15 mg N were incubated for 1 h in a 10 ml solution (0.1 N HCl) containing 1 g L 1 of pepsin (Sigma P7012, Sigma Chemical Co., St. Louis, MO). Following incubation, 13.5 ml phosphate buffer (ph 7.8) containing 37.5 mg pancreatin (Sigma P7545, Sigma Chemical Co., St. Louis, MO) was added and the samples were incubated for 24 h at 38 C. Undigested CP was precipitated using 100% trichloroacetic acid (3 ml). The supernatant was analyzed for soluble CP, using the Kjeldahl method (AOAC 1990). Intestinal digestibility of CP was calculated as trichloroacetic acid-soluble CP divided by amount of residual CP. Post-ruminal available CP was then estimated by multiplying intestinal CP digestibility by RUP. Sheep Digestibility Trial Five test diets were formulated in which HM replaced canola meal at 0, 25, 50, 75 and 100%, as a protein source. The HM addition rate (DM basis) was 0, 50, 100, 150 and 200 g kg 1, respectively. Diets were formulated to contain 160 g kg 1 CP (DM basis). Urea was added as necessary to keep diets isonitrogenous. Diets were pelleted (4.8-mm diameter) and fed twice daily in equal portions at 08:00 and 15:00 h. Each animal was fed 10 g of a trace-mineral salt mixture containing, per kilogram, 160 g Ca, 160 g P, 1.5 g Zn, 25 mg I, 100 mg Fe, 640 mg Mn, 14 mg Co, 3 g F, IU vitamin A, IU vitamin D and 500 IU vitamin E. Diets were evaluated through a 21-d feeding period. Voluntary feed intake and digestibility of the test diets were determined using 20 growing Suffolk ram lambs (initial weight 84.3 ± 7.0 kg). Lambs were housed in individual crates and randomly allocated to one of the five diets (four animals per diet). Animals were adapted to dietary treatments through a 7-d adaptation period followed by a 7-d period during which voluntary intake was determined. During this period, the animals were fed to leave 10 to 15% orts. The voluntary intake period was followed by 3 d of restricted feeding (85% of ad libitum intake) and 5 d of total fecal collection. Feces were collected once daily, subsampled (10% of total fecal output) and dried in a forced-air oven at 55 C for 72 h. The guidelines of the Canadian Council on Animal Care (1980) were followed for both the in situ and sheep trials. Fecal samples were composited by animal over the 5-d collection period and processed through a 1-mm screen using a Christie-Norris mill. Feed samples were collected simultaneously, dried and processed similar to fecal samples. Feed and fecal samples were analyzed for moisture, NDF, ADF, and CP as described above. Feed samples were also analyzed for ADL. Gross energy content was deter-

3 MUSTAFA HEMP MEAL FOR RUMINANTS 93 Table 1. Chemical composition of HM relative to other protein sources (DM basis) Protein source Hemp Borage Canola Heated canola meal meal meal meal Ash (g kg 1 ) Ether extract (g kg 1 ) NDF (g kg 1 ) ADF (g kg 1 ) ADL (g kg 1 ) CP (g kg 1 ) Soluble protein (g kg 1 of CP) Nonprotein nitrogen (g kg 1 of CP) Neutral detergent-insoluble protein (g kg 1 of CP) Acid detergent-insoluble protein (g kg 1 of CP) Table 2. In situ ruminal DM and CP kinetic parameters and effective degradability of HM relative to BM, CM and HCM Protein source Heated canola Hemp meal Borage meal Canola meal meal SEM Dry matter (DM) Soluble (g kg 1 DM) 82.4d 253.6b 269.4a 194.0c 3.36 Degradable (g kg 1 DM) 505.9c 483.1d 586.6b 786.3a 6.21 Degradation rate (% h 1 ) 2.4c 3.7b 5.4a 1.8d 0.08 Effective degradability (g kg 1 ) z 247.7d 459.7b 573.1a 400.7c 2.81 Crude protein (CP) Soluble (g kg 1 CP) 65.3c 318.4a 182.5b 77.4c 6.28 Degradable (g kg 1 CP) 900.9a 518.1c 807.3b 893.4a 3.33 Degradation rate (% h 1 ) 2.9c 6.0a 4.4b 2.0d 0.17 Effective degradability (g kg 1 ) z 393.8c 600.2a 554.4b 329.0d 6.26 Rumen-undegraded CP (g kg 1 CP) 774.2a 401.5c 473.9b 790.8a 9.47 Intestinally available CP (g kg 1 CP) 653.8a 242.3c 342.9b 635.1a Total available CP (g kg 1 CP) z Calculated assuming rumen flow rate of 5% h 1. a d Means in the same row followed by different letters are different (P < 0.05). mined on feed and fecal samples using an adiabatic oxygenbomb calorimeter. Statistical Analysis Data from the in situ nylon bag and in vitro intestinaldigestibility trials were analyzed as a randomized complete block design using cows as blocks. Data from the total tract digestibility trial were analyzed as a completely randomized design (five treatments and four replicates). Mean separation was carried out using the Student Newman Keuls test (Steel and Torrie 1980) when the effect of treatment was significant (P < 0.05). RESULTS AND DISCUSSION Chemical Composition The chemical composition of HM relative to the other protein sources is shown in Table 1. Statistical comparisons were not possible because each protein meal was obtained from one source. However, the chemical analysis showed that HM had higher NDF, ADF and ADL than the other protein sources. The CP content of HM was similar to that of the BM and lower than that of CM and HCM. Hemp meal had a soluble CP level comparable with that of HCM, but lower than that of BM and CM. Neutral detergent insoluble CP in HM was higher than in BM and lower than in unheated and heated CM. However, the proportion of total CP associated with ADF was similar for the four protein sources. Rumen Incubation The in situ soluble DM fraction was lowest (P < 0.05) for HM and highest (P < 0.05) for CM (Table 2) whereas potentially degradable DM was highest (P < 0.05) for HCM and lowest (P < 0.05) for BM. The rate of degradation of potentially degradable DM followed the order CM > BM > HM > HCM (P < 0.05). Effective degradability of DM differed (P < 0.05) for all four protein sources tested and was highest (P < 0.05) for CM and lowest (P < 0.05) for HM, and was higher (P < 0.05) in BM than HCM. The high EDDM of CM is well documented (De Boer et al. 1987; Khorasani et al.

4 94 CANADIAN JOURNAL OF ANIMAL SCIENCE Table 3. Ingredients and chemical analysis of diets used in the digestibility trial Hemp-meal inclusion rate (% of canola meal) Ingredients (g kg 1 DM basis) Hemp meal Canola meal Brome hay Barley Tallow Urea Limestone Chemical analysis (g kg 1 ) Ash CP NDF ADF ADL Gross energy (MJ kg 1 ) Table 4. Effect of HM inclusion rate on nutrient utilization by sheep Hemp-meal inclusion rate (% of canola meal) Effect of hemp meal z SEM L Q C Feed intake DM intake (g d 1 ) NS NS NS DM intake (g kg 0.75 ) NS NS NS Digestibility coefficient DM (g kg 1 ) NS NS NS OM (g kg 1 ) NS NS NS NDF (g kg 1 ) NS NS NS ADF (g kg 1 ) NS NS NS CP (g kg 1 ) NS NS NS Gross energy (kj MJ 1 ) NS NS NS Digestible energy (MJ kg 1 ) NS NS NS z NS, not significant. 1994). The EDDM of CM in this study is in good agreement with that reported by Boila and Ingalls (1992) and Kirkpatrick and Kennelly (1987). However, little information on EDDM of BM and HCM meal is available in the literature. Hemp meal and HCM had the lowest (P < 0.05) soluble CP fraction and the highest (P < 0.05) potentially degradable CP fraction relative to CM and BM (Table 2). Borage meal had a higher (P < 0.05) soluble CP fraction and lower (P < 0.05) potentially degradable CP fraction than CM. The rate of degradation of the potentially degradable CP fraction and effective degradability of CP followed the order BM > CM > HM > HCM (P < 0.05). The lower effective CP degradability of HM relative to CM and BM is likely a combination of a lower soluble CP fraction and a slower rate of degradation of the potentially degradable CP fraction. Such a combination also resulted in a lower ruminal CP degradability of HCM relative to CM. Other experiments have shown that the rate and extent of ruminal degradation of canola meal are reduced by heat treatment (Moshtaghi Nia and Ingalls 1992; Mustafa et al. 1997b). The higher effective CP degradability of BM relative to CM, as reported in this study, is not in agreement with our previous study (Mustafa et al. 1997a), which showed higher effective degradability of CP for CM than BM. This discrepancy may be a result of differences in processing conditions for the two canola batches during oil extraction. Kendall et al. (1991) reported that effective degradability of CM CP ranged from 443 to 593 g kg 1 for samples obtained from five processors in western Canada. These authors attributed such variation to differences in processing technique between canola crushing plants. The results of this study do, however, suggest that HM is highly undegraded in the rumen compared with CM and BM and is closer to HCM in its rumen degradability characteristics. Intestinal Digestibility of Rumen Undegraded Protein Rumen undegraded protein, as estimated from 12 h of rumen incubation, was higher (P < 0.05) in HM and HCM than in CM, which in turn was higher (P < 0.05) than in BM (Table 2). These results are consistent with those for effective degradability of CP, which showed lower ruminal degradability of HM and HCM meal relative to CM and

5 BM. Our estimates of RUP content for CM and HCM are similar to values reported by McKinnon et al. (1991). Intestinal availability of RUP, as estimated by pepsin pacreatin assay, was higher (P < 0.05) for HM and HCM than for CM and was higher (P < 0.05) in CM than BM (Table 2). This is likely a reflection of the low ruminal CP degradability of HM and HCM relative to the other two protein sources, which resulted in more CP being available for post-ruminal digestion. These results agree with those reported by McKinnon et al. (1995), who found that heat treatment of CM at 125 C for 10 min increased the amount of protein available for post-ruminal digestion from 304 to 595 g kg 1 of CP. Total available CP was similar for the four protein sources (average g kg 1 of CP). These results indicate that HM can be considered a good source of rumen escape protein, equivalent to heat-treated canola meal. Sheep Digestibility Trial The chemical analysis of the diets used in the digestibility trial indicated that the progressive inclusion of HM increased NDF, ADF and ADL (Table 3). There was no change in CP level as diets were formulated to be isonitrogenous. Dry matter intake (Table 4) was not influenced by HM inclusion rate, averaging g d 1 and g kg Mustafa et al. (1997b) reported a similar DMI level (123.9 g kg 0.75 ) for sheep fed diets containing 25, 50 and 75% CM (DM basis). These results indicate that feeding HM to sheep at levels up to 20% (DM basis) of the diet will not depress DM intake. Total tract DM and OM digestibility were similar across treatments (Table 4). These results suggest that DM and OM digestibility of HM meal is equal to that of CM. Substituting HM for CM had no effect on the digestibility coefficients of NDF, ADF, CP and gross energy (Table 4). The average values were g kg 1, g kg 1, g kg 1 and kj MJ 1, respectively. Nutrient digestibility coefficients comparable to those reported in this study were previously reported for a dehydrated alfalfa based diet containing 250 g kg 1 (DM basis) CM (Mustafa et al. 1997b). Digestible energy content was not affected by dietary treatments and averaged 12.1 MJ kg 1. These results suggest that in isonitrogenous diets, HM protein can replace CM as a protein supplement up to 200 g kg 1 of the diet DM. CONCLUSIONS Hemp meal is an excellent natural source of RUP that is equivalent to heat-treated canola meal. When substituted for CM, as a protein source in isonitrogenous diets (up to 200 g kg -1 of DM), HM had no detrimental effects on feed intake or nutrient utilization by sheep. Further studies are required to determine the effects of including HM in beef and dairy rations as a RUP source. ACKNOWLEDGMENT The authors would like to thank Dr. Dave Hutcheson, president of the Western Grower Seed Corporation for providing the hemp meal. 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