DOI: 10.1111/jpn.12230
ORIGINAL ARTICLE
Effects of essential oils, yeast culture and malate on rumen fermentation, blood metabolites, growth performance and nutrient digestibility of Baluchi lambs fed high-concentrate diets M. Malekkhahi1, A. M. Tahmasbi1, A. A. Naserian1, M. Danesh Mesgaran1, J. L. Kleen2 and A. A. Parand3 1 Department of Animal Science, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran 2 CowConsult, Uplengen, Germany, and 3 Dairy Cow Veterinary Consult, Khorasan Razavi, Iran
Summary The experiment was conducted to evaluate the effects of dietary supplementation with a mixture of essential oils (MEO), yeast culture (YC) and malate on performance, nutrient digestion, rumen fermentation and blood metabolites of lambs fed high-concentrate growing diets. For this purpose, twenty Baluchi lambs (17.3 0.5 kg body weight and 3 months old) were randomly assigned to four dietary treatments in a completely randomized design with five lambs per treatment. The treatment groups were as follows: (i) control: basal diet without any additive, (ii) basal diet plus 400 mg/day MEO (thymol, carvacrol, eugenol, limonene and cinnamaldehyde), (iii) basal diet with 4 g/day YC and (iv) basal diet plus 4 g/day malate. No differences between the dietary treatments were observed in dry matter intake, average daily gain or feed conversion ratio (p > 0.05). Compared with control and malate treatment, lambs fed MEO and YC had an improved crude protein digestibility (p < 0.05). Yeast culture significantly increased (p > 0.05) cell wall digestibility compared to the other treatments. No differences were observed between treatments with respect to nitrogen balance or ruminal pH and ammonia concentrations (p > 0.05). No differences were observed between treatments with respect to ruminal total volatile fatty acid concentration and molar proportions of acetate, butyrate and valerate. Molar proportion of propionate was higher (p < 0.05) for YC and malate compared to control and MEO. Plasma glucose concentration was higher (p < 0.05) in lambs fed YC and malate than in lambs fed the control or the MEO diet. Blood concentration of triglycerides significantly decreased when feeding the MEO and YC diets (p < 0.05). It was concluded that YC may be more useful as a feed additive for manipulation of rumen fermentation in lambs fed with high-concentrate diets than MEO and malate, because YC enhanced crude protein and cell wall digestibility, ruminal molar proportion of propionate and plasma glucose concentration. Keywords lamb, digestibility, mixture essential oils, yeast culture, malate Correspondence M. Malekkhahi, Department of Animal Science, Faculty of Agriculture, Ferdowsi University of Mashhad, P.O. Box: 91775-1163, Mashhad, Iran. Tel: +989151744289; Fax: +985118796545; E-mail: [email protected] Received: 31 October 2013; accepted: 30 June 2014
Introduction Intensive lamb fattening systems require highconcentrate diets to assure high productivity and fast growth (Mungoi et al., 2012) which causes ruminal acidosis and affects the ruminal microbial population (Gonzalez-Momita et al., 2009). Calsamiglia et al. (2012) referred such adversity as ‘high-concentrate syndrome’ and suggested to adopt strategies to modulate pH and fermentation pathways in the rumen with yeast, organic acids or essential oils (EO) to ameliorate the rumen environment. Essential oils are naturally occurring, secondary plant metabolites that can be
steam-volatilized or extracted using organic solvents. Limited literature exists that highlights the potential of EO to manipulate ruminal microbial fermentation and increase feed efficiency in ruminants (Calsamiglia et al., 2007). By providing growth factors including organic acids, B vitamins and amino acids that stimulate microbial growth in the rumen, Saccharomyces cerevisiae may stabilize ruminal fermentation (Chaucheyras-Durand et al., 2008). Callaway and Martin (1997) and Brossard et al. (2006) suggested that the yeast effects were due to the nutrients and/or soluble growth factors provided to the ruminal microbes. Unlike ionophores that
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inhibit microbial fermentation, malate supplementation appears to increase the utilization of ruminal lactate, especially by the predominant bacteria Selenomonas ruminantium (Nisbet and Martin, 1994). In fermentation studies using mixed rumen microorganisms, malate increased propionate and total volatile fatty acid (VFA) concentrations (Martin and Streeter, 1995), as well as ruminal pH levels in animals fed soluble starch and cracked corn (Martin et al., 1999). Limited information exists on possible effects of mixtures of essential oils (MEO), yeast culture (YC) and malate salts on performance, nutrient digestibility, ruminal fermentation and plasma parameters in growing lambs. The present study was therefore designed to evaluate the effects of MEO, YC and malate salts in fast-growing Baluchi lambs. Experimental procedures Animals and treatments
The experiment was conducted at the Research Farm of the Faculty of Agriculture, Ferdowsi University of Mashhad (Iran), in 2012. The experimental protocols were reviewed and approved by the Animal Care Committee of the university. Twenty Baluchi male lambs [17.3 kg body weight (BW); 3 months of age] were randomly assigned to four dietary treatments in a completely randomized design with five lambs per treatment. The basal diet consisted of concentrate, maize silage and wheat straw as described in Table 1. The
treatments were as follows: (i) control: basal diet without additives; (ii) basal diet supplemented with 400 mg/day MEO with main components being thymol (C10H14O), carvacrol (C6H3CH3(OH)(C3H7)), eugenol (C10H12O2), limonene (C10H16) and e, Terssac, France), cinnamaldehyde (C9H8O) (Phod (iii) basal diet supplemented with a live YC providing 20 9 109 CFU/day of S. cerevisiae (Yea-Saccâ1026; Alltech, Nicholasville, KY, USA) and 4) basal diet supplemented with 0.64 g/of disodium malate (Na2(C2H4O(COO)2) and 3.36 g/day of calcium malate (Ca(C2H4O(COO)2) (Rumalatoâ; Norel & Nature Nutrition, Madrid, Spain). Levels of MEO and YC were based on manufacturer’s recommendations for sheep, and malate level was chosen based on the results reported in previous in vivo studies (Gonzalez-Momita et al., 2009; Mungoi et al., 2012). Feed additives were mixed directly with the concentrate at the time of feeding. Management and sample collection
*Containing per kg: 20 g Mg, 50 g K, 30 g Zn, 20 g Mn, 30 g Fe, 3 g Cu, 0.01 g Se, 0.1 g Co, 0.1 g I, 500 000 IU vitamin A, 100 000 IU vitamin D, and 1000 IU vitamin E.
Lambs were randomly assigned and confined to individual pens (2.5 9 5 m) where fresh drinking water was available at all times. The study started with an adaption period (14 day) which was followed by a 50-day period during which weight changes and dry matter intake (DMI) were recorded. In the final part of the experiment, animals were moved to metabolism cages (0.6 9 1 m, 0.8 m high) equipped for separate, quantitative collection of faeces and urine. After 3 day of adaptation, faeces and urine voided by each lamb in 24 h were quantitatively collected for 6 day. A 10% aliquot of total faecal output was collected each day to determine digestibility and subsequently dried to constant weight before analysis. Urine was collected in 10% H2SO4 (v/v) to keep pH below 3. The daily volume of urine was determined, from which a subsample (20%) from each lamb was isolated daily and frozen. Rumen fluid was collected from each lamb via a stomach tube 2 h after the morning feeding, and pH was measured immediately using a glass electrode pH-meter (Model 691; Metrohm, Herisau, Switzerland). Samples were also taken and preserved for the analyses of NH3-N (5 ml mixed with 5 ml of 0.2 N HCl) and VFA [5 ml added to 1 ml of 25% (w/v) meta-phosphoric acid]. Blood samples were collected by jugular vein puncture using EDTA-coated tubes (BD Vacutainerâ; Becton Dickinson and Company, Franklin Lakes, NJ, USA) 2 h after the morning feeding on day 60. Blood samples were centrifuged at 3500 g for 15 min at 4 °C, and plasma was immediately frozen at 20 °C for the analysis of glucose, urea-N, cholesterol, triglycerides and total protein.
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Table 1 Ingredients and chemical composition of the diet used in experiment g/kg DM Ingredient Maize silage Wheat straw Barley grain Cotton seed meal Wheat brown Urea Vitamin/Mineral premix* Limestone Salt Chemical composition Ash CP Starch Neutral detergent fibre ACid detergent fibre Ether extract
280 20 450 136 97 7 8.5 14.5 3 92 150 320 360 270 30
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Sample analyses
Feeds offered and rejected as well as total faeces collected were dried individually in an air draft oven at 60°C for more than 48 h until a constant weight was reached (AOAC, 1997). All feed and faecal samples were then ground and passed through a 2-mm screen using a Cyclotec 1883 Sample Mill. Ash content was obtained after combustion in a muffle furnace at 550°C for 3 h. The micro-Kjeldahl method was used to determine the nitrogen (N) content in feed, faeces and urine. The N balance (g/day) was calculated by subtracting faecal and urinary N excretions from total N intake. Retained N (%) was determined by dividing N balance by total N intake (g/day). Ether extract (EE) was determined by the Soxhlet method (AOAC, 1997). Fibre fractionation was performed according to the methods described by Van Soest et al. (1991). Neutral detergent fibre (NDF), using a heat stable amylase, and acid detergent fibre (ADF) were expressed including residual ash. Starch was determined calorimetrically according to the procedure of Hall (2000). Ammonia concentration was analysed by the phenol hypochlorite method of Weatherburn (1967). Ruminal fluid samples for VFA analysis were thawed at room temperature and centrifuged (Eppendorf AG, Hamburg, Germany) at 3000 g for 20 min at 4 °C. In the supernatant, VFA concentrations were measured using a gas chromatograph (YL6100 GC; Young Lin Instrument, Anyang, South Korea) equipped with a 50-m (0.32 mm ID) silica-fused column (CP-Wax Chrompack Capillary Column; Varian, Palo Alto, CA, USA). Helium was used as the carrier gas, and initial and final oven temperatures were set at 55 and 195 °C respectively. Detector and injector temperatures were set at 250 °C. Crotonic acid (1 : 7 v/v) was used as the internal standard. Cholesterol, triglyceride, blood urea-N (BUN), total protein and glucose concentrations were determined by an automated biochemical analyser (Alcyon 300i; Abbott Labs, Abbott Park, IL, USA) using commercial kits (Pars Azmoon, Tehran, Iran) according to the manufacturer’s instructions. Statistical analysis
Data were statistically analysed according to a completely randomized design using the general linear model (GLM) procedure of SAS 9.1.3 (2001) (M/s SAS Institute, Cary, NC, USA). Significant differences between means of treatments were assessed by the Journal of Animal Physiology and Animal Nutrition © 2014 Blackwell Verlag GmbH
Essential oils, yeast and malate for growing lambs
Duncan’s test, and the differences between treatments were declared significant at p < 0.05. Results Dry matter intake and lamb performance
Addition of MEO, YC and malate affected neither DMI (p = 0.21) nor average daily gain (ADG) (p = 0.4) (Table 2). Final BW (p = 0.95) and feed conversion ratio (FCR) (p = 0.07) were also not affected by dietary treatment. Apparent total tract digestibility and N retention
Results of apparent total tract digestibility are shown in Table 3. Crude protein (CP) digestibility was higher (p < 0.05) in lambs fed MEO and YC than in lambs fed the control or malate diets. NDF digestibility for YC was higher (p < 0.05) compared to other treatments. Differences in DM, OM, ADF and starch digestibility were not significant between the treatments. N intake, N excretion and N balance were unaffected with MEO, YC or malate supplementation. N retention tended to be higher in lambs on the YC-supplemented diet (p < 0.06) than on the other diets. Rumen fermentation parameters
None of the experimental treatments affected ruminal pH and NH3-N concentration. Supplementing YC and malate increased the molar proportion of propionate (p < 0.05), whereas the concentration of total VFA, and the molar proportions acetate, butyrate, valerate and ratio of acetate to propionate were similar for all treatments (Table 4). Table 2 Effect of dietary supplementation with a mixture essential oil (MEO), yeast culture (YC) and malate (M) on performance of growing lambs Treatment Item
Control
MEO
YC
M
SEM*
Pvalue†
Dry matter intake (DMI), g/day Initial body weight (BW), kg Final BW‡, kg Feed conversion ratio§
885
822
796
881
33.1
0.22
17.0
17.4
17.1
17.8
1.02
0.92
29.6 4.22
29.4 4.19
29.5 3.83
30.3 4.27
0.31 0.35
0.72 0.74
*Standard error of mean. †Level of significance. ‡Feed and water were withdrawn for 8 h before lambs were weighed. §Total DMI/average daily gain.
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Table 3 Effect of dietary supplementation with a mixture essential oil (MEO), yeast culture (YC) and malate (M) on apparent digestibility coefficients and N balance of growing lambs Treatment Item
Control
MEO
Apparent digestibility coefficient, % Dry matter 76.6 79.0 Organic matter 77.6 80.6 Crude protein 76.6b 80.3a Neutral detergent 52.3c 54.2b fibre Acid detergent 46.0 48.6 fibre Starch 84.0 87.1 Nitrogen balance N intake, g/day 20.5 21.0 Faecal N, g/day 6.76 6.34 Urinary N, g/day 5.94 6.15 N balance, g/day 8.17 8.55 Retained N, % 39.1 40.6
YC
M
SEM*
Pvalue†
81.0 83.0 82.6a 61.0a
76.0 87.0 76.0b 53.3b
0.010 0.010 0.009 0.005
0.18 0.14 0.05). Compared with control and malate treatment, lambs fed MEO and YC had an improved crude protein digestibility (p < 0.05). Yeast culture significantly increased (p > 0.05) cell wall digestibility compared to the other treatments. No differences were observed between treatments with respect to nitrogen balance or ruminal pH and ammonia concentrations (p > 0.05). No differences were observed between treatments with respect to ruminal total volatile fatty acid concentration and molar proportions of acetate, butyrate and valerate. Molar proportion of propionate was higher (p < 0.05) for YC and malate compared to control and MEO. Plasma glucose concentration was higher (p < 0.05) in lambs fed YC and malate than in lambs fed the control or the MEO diet. Blood concentration of triglycerides significantly decreased when feeding the MEO and YC diets (p < 0.05). It was concluded that YC may be more useful as a feed additive for manipulation of rumen fermentation in lambs fed with high-concentrate diets than MEO and malate, because YC enhanced crude protein and cell wall digestibility, ruminal molar proportion of propionate and plasma glucose concentration. Keywords lamb, digestibility, mixture essential oils, yeast culture, malate Correspondence M. Malekkhahi, Department of Animal Science, Faculty of Agriculture, Ferdowsi University of Mashhad, P.O. Box: 91775-1163, Mashhad, Iran. Tel: +989151744289; Fax: +985118796545; E-mail: [email protected] Received: 31 October 2013; accepted: 30 June 2014
Introduction Intensive lamb fattening systems require highconcentrate diets to assure high productivity and fast growth (Mungoi et al., 2012) which causes ruminal acidosis and affects the ruminal microbial population (Gonzalez-Momita et al., 2009). Calsamiglia et al. (2012) referred such adversity as ‘high-concentrate syndrome’ and suggested to adopt strategies to modulate pH and fermentation pathways in the rumen with yeast, organic acids or essential oils (EO) to ameliorate the rumen environment. Essential oils are naturally occurring, secondary plant metabolites that can be
steam-volatilized or extracted using organic solvents. Limited literature exists that highlights the potential of EO to manipulate ruminal microbial fermentation and increase feed efficiency in ruminants (Calsamiglia et al., 2007). By providing growth factors including organic acids, B vitamins and amino acids that stimulate microbial growth in the rumen, Saccharomyces cerevisiae may stabilize ruminal fermentation (Chaucheyras-Durand et al., 2008). Callaway and Martin (1997) and Brossard et al. (2006) suggested that the yeast effects were due to the nutrients and/or soluble growth factors provided to the ruminal microbes. Unlike ionophores that
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acids supply on their absorption and on water kinetics in the rumen of sheep sustained by intragastric infusions. Journal of Animal Science 81, 2609–2616. Martin, S. A., 2004: Effects of DL-malate on in vitro forage fiber digestion by mixed ruminal microorganisms. Current Microbiology 48, 27–31. Martin, S. A.; Streeter, M. N., 1995: Effect of malate on in vitro mixed ruminal microorganism fermentation. Journal of Animal Science 73, 2141–2145. Martin, S. A.; Streeter, M. N.; Nisbet, D. J.; Hill, G. M.; Williams, S. E., 1999: Effects of dl-malate on ruminal metabolism and performance of cattle fed a high-concentrate diet. Journal of Animal Science 77, 1008–1015. Mir, Z.; Mir, P. S., 1994: Effect of the addition of live yeast (Saccharomyces cerevisiae) on growth and carcass quality of steers fed high-forage or high-grain diets and on feed digestibility and in situ degradability. Journal of Animal Science 72, 537–545. Montano, M. F.; Chai, W.; Zinn-Ware, T. E.; Zinn, R. A., 1999: Influence of malic acid supplementation on ruminal pH, lactic acid utilization, and digestive function in steers fed high-concentrate finishing diets. Journal of Animal Science 77, 780–784. Mungoi, M.; Flores, C.; Casals, R.; Caja, G., 2012: Effect of malate and starch source on digestibility and nutrient balance of growing- fattening lambs. Animal Feed Science and Technology 22, 154–162. Nisbet, D. J.; Martin, S. A., 1994: Factors affecting l-lactate utilization by Selenomonas ruminantium. Journal of Animal Science 72, 1355–1361. Paryad, A.; Rashidi, M., 2009: Effect of yeast (Saccharomyces cerevisiae) on apparent digestibility and nitrogen retention of tomato pomace in sheep. Pakistan Journal of Nutrition 8, 273–278. Petit, H. V.; Flipot, P. M., 1992: Feed utilization of beef steers fed grass as hay or silage with or without nitrogen supplementation. Journal of Animal Science 70, 876–883. SAS Institute, 2001: SAS/STAT User’s Guide: Version 9.1. SAS Institute, Cary, NC. Stella, A. V.; Paratte, R.; Valnegri, L.; Cigalino, G.; Soncini, G.; Chevaux, E.; DellOrto, V.; Savoini, G., 2007: Effect of administration of live Saccharomyces cerevisiae on milk production, milk composition, blood metabolites and faecal flora
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ammonia. Analytical Chemistry 89, 971– 974. Williams, P. E. V., 1989: The Mode of Action of Yeast Culture in Ruminal Diets. A Review of the Effect on Rumen Fermentation Patterns. Biotechnology in the Feed Industry. Alltech Tech. Publishers, Nicholasville, KY, USA, pp. 65. Yang, W. Z.; Benchaar, C.; Ametaj, B. N.; Beauchemin, K. A., 2010: Dose response to eugenol supplementation in growing beef cattle: ruminal fermentation and intestinal digestion. Animal Feed Science and Technology 158, 57–64.
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ORIGINAL ARTICLE
Effects of essential oils, yeast culture and malate on rumen fermentation, blood metabolites, growth performance and nutrient digestibility of Baluchi lambs fed high-concentrate diets M. Malekkhahi1, A. M. Tahmasbi1, A. A. Naserian1, M. Danesh Mesgaran1, J. L. Kleen2 and A. A. Parand3 1 Department of Animal Science, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran 2 CowConsult, Uplengen, Germany, and 3 Dairy Cow Veterinary Consult, Khorasan Razavi, Iran
Summary The experiment was conducted to evaluate the effects of dietary supplementation with a mixture of essential oils (MEO), yeast culture (YC) and malate on performance, nutrient digestion, rumen fermentation and blood metabolites of lambs fed high-concentrate growing diets. For this purpose, twenty Baluchi lambs (17.3 0.5 kg body weight and 3 months old) were randomly assigned to four dietary treatments in a completely randomized design with five lambs per treatment. The treatment groups were as follows: (i) control: basal diet without any additive, (ii) basal diet plus 400 mg/day MEO (thymol, carvacrol, eugenol, limonene and cinnamaldehyde), (iii) basal diet with 4 g/day YC and (iv) basal diet plus 4 g/day malate. No differences between the dietary treatments were observed in dry matter intake, average daily gain or feed conversion ratio (p > 0.05). Compared with control and malate treatment, lambs fed MEO and YC had an improved crude protein digestibility (p < 0.05). Yeast culture significantly increased (p > 0.05) cell wall digestibility compared to the other treatments. No differences were observed between treatments with respect to nitrogen balance or ruminal pH and ammonia concentrations (p > 0.05). No differences were observed between treatments with respect to ruminal total volatile fatty acid concentration and molar proportions of acetate, butyrate and valerate. Molar proportion of propionate was higher (p < 0.05) for YC and malate compared to control and MEO. Plasma glucose concentration was higher (p < 0.05) in lambs fed YC and malate than in lambs fed the control or the MEO diet. Blood concentration of triglycerides significantly decreased when feeding the MEO and YC diets (p < 0.05). It was concluded that YC may be more useful as a feed additive for manipulation of rumen fermentation in lambs fed with high-concentrate diets than MEO and malate, because YC enhanced crude protein and cell wall digestibility, ruminal molar proportion of propionate and plasma glucose concentration. Keywords lamb, digestibility, mixture essential oils, yeast culture, malate Correspondence M. Malekkhahi, Department of Animal Science, Faculty of Agriculture, Ferdowsi University of Mashhad, P.O. Box: 91775-1163, Mashhad, Iran. Tel: +989151744289; Fax: +985118796545; E-mail: [email protected] Received: 31 October 2013; accepted: 30 June 2014
Introduction Intensive lamb fattening systems require highconcentrate diets to assure high productivity and fast growth (Mungoi et al., 2012) which causes ruminal acidosis and affects the ruminal microbial population (Gonzalez-Momita et al., 2009). Calsamiglia et al. (2012) referred such adversity as ‘high-concentrate syndrome’ and suggested to adopt strategies to modulate pH and fermentation pathways in the rumen with yeast, organic acids or essential oils (EO) to ameliorate the rumen environment. Essential oils are naturally occurring, secondary plant metabolites that can be
steam-volatilized or extracted using organic solvents. Limited literature exists that highlights the potential of EO to manipulate ruminal microbial fermentation and increase feed efficiency in ruminants (Calsamiglia et al., 2007). By providing growth factors including organic acids, B vitamins and amino acids that stimulate microbial growth in the rumen, Saccharomyces cerevisiae may stabilize ruminal fermentation (Chaucheyras-Durand et al., 2008). Callaway and Martin (1997) and Brossard et al. (2006) suggested that the yeast effects were due to the nutrients and/or soluble growth factors provided to the ruminal microbes. Unlike ionophores that
Journal of Animal Physiology and Animal Nutrition 99 (2015) 221–229 © 2014 Blackwell Verlag GmbH
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inhibit microbial fermentation, malate supplementation appears to increase the utilization of ruminal lactate, especially by the predominant bacteria Selenomonas ruminantium (Nisbet and Martin, 1994). In fermentation studies using mixed rumen microorganisms, malate increased propionate and total volatile fatty acid (VFA) concentrations (Martin and Streeter, 1995), as well as ruminal pH levels in animals fed soluble starch and cracked corn (Martin et al., 1999). Limited information exists on possible effects of mixtures of essential oils (MEO), yeast culture (YC) and malate salts on performance, nutrient digestibility, ruminal fermentation and plasma parameters in growing lambs. The present study was therefore designed to evaluate the effects of MEO, YC and malate salts in fast-growing Baluchi lambs. Experimental procedures Animals and treatments
The experiment was conducted at the Research Farm of the Faculty of Agriculture, Ferdowsi University of Mashhad (Iran), in 2012. The experimental protocols were reviewed and approved by the Animal Care Committee of the university. Twenty Baluchi male lambs [17.3 kg body weight (BW); 3 months of age] were randomly assigned to four dietary treatments in a completely randomized design with five lambs per treatment. The basal diet consisted of concentrate, maize silage and wheat straw as described in Table 1. The
treatments were as follows: (i) control: basal diet without additives; (ii) basal diet supplemented with 400 mg/day MEO with main components being thymol (C10H14O), carvacrol (C6H3CH3(OH)(C3H7)), eugenol (C10H12O2), limonene (C10H16) and e, Terssac, France), cinnamaldehyde (C9H8O) (Phod (iii) basal diet supplemented with a live YC providing 20 9 109 CFU/day of S. cerevisiae (Yea-Saccâ1026; Alltech, Nicholasville, KY, USA) and 4) basal diet supplemented with 0.64 g/of disodium malate (Na2(C2H4O(COO)2) and 3.36 g/day of calcium malate (Ca(C2H4O(COO)2) (Rumalatoâ; Norel & Nature Nutrition, Madrid, Spain). Levels of MEO and YC were based on manufacturer’s recommendations for sheep, and malate level was chosen based on the results reported in previous in vivo studies (Gonzalez-Momita et al., 2009; Mungoi et al., 2012). Feed additives were mixed directly with the concentrate at the time of feeding. Management and sample collection
*Containing per kg: 20 g Mg, 50 g K, 30 g Zn, 20 g Mn, 30 g Fe, 3 g Cu, 0.01 g Se, 0.1 g Co, 0.1 g I, 500 000 IU vitamin A, 100 000 IU vitamin D, and 1000 IU vitamin E.
Lambs were randomly assigned and confined to individual pens (2.5 9 5 m) where fresh drinking water was available at all times. The study started with an adaption period (14 day) which was followed by a 50-day period during which weight changes and dry matter intake (DMI) were recorded. In the final part of the experiment, animals were moved to metabolism cages (0.6 9 1 m, 0.8 m high) equipped for separate, quantitative collection of faeces and urine. After 3 day of adaptation, faeces and urine voided by each lamb in 24 h were quantitatively collected for 6 day. A 10% aliquot of total faecal output was collected each day to determine digestibility and subsequently dried to constant weight before analysis. Urine was collected in 10% H2SO4 (v/v) to keep pH below 3. The daily volume of urine was determined, from which a subsample (20%) from each lamb was isolated daily and frozen. Rumen fluid was collected from each lamb via a stomach tube 2 h after the morning feeding, and pH was measured immediately using a glass electrode pH-meter (Model 691; Metrohm, Herisau, Switzerland). Samples were also taken and preserved for the analyses of NH3-N (5 ml mixed with 5 ml of 0.2 N HCl) and VFA [5 ml added to 1 ml of 25% (w/v) meta-phosphoric acid]. Blood samples were collected by jugular vein puncture using EDTA-coated tubes (BD Vacutainerâ; Becton Dickinson and Company, Franklin Lakes, NJ, USA) 2 h after the morning feeding on day 60. Blood samples were centrifuged at 3500 g for 15 min at 4 °C, and plasma was immediately frozen at 20 °C for the analysis of glucose, urea-N, cholesterol, triglycerides and total protein.
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Table 1 Ingredients and chemical composition of the diet used in experiment g/kg DM Ingredient Maize silage Wheat straw Barley grain Cotton seed meal Wheat brown Urea Vitamin/Mineral premix* Limestone Salt Chemical composition Ash CP Starch Neutral detergent fibre ACid detergent fibre Ether extract
280 20 450 136 97 7 8.5 14.5 3 92 150 320 360 270 30
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Sample analyses
Feeds offered and rejected as well as total faeces collected were dried individually in an air draft oven at 60°C for more than 48 h until a constant weight was reached (AOAC, 1997). All feed and faecal samples were then ground and passed through a 2-mm screen using a Cyclotec 1883 Sample Mill. Ash content was obtained after combustion in a muffle furnace at 550°C for 3 h. The micro-Kjeldahl method was used to determine the nitrogen (N) content in feed, faeces and urine. The N balance (g/day) was calculated by subtracting faecal and urinary N excretions from total N intake. Retained N (%) was determined by dividing N balance by total N intake (g/day). Ether extract (EE) was determined by the Soxhlet method (AOAC, 1997). Fibre fractionation was performed according to the methods described by Van Soest et al. (1991). Neutral detergent fibre (NDF), using a heat stable amylase, and acid detergent fibre (ADF) were expressed including residual ash. Starch was determined calorimetrically according to the procedure of Hall (2000). Ammonia concentration was analysed by the phenol hypochlorite method of Weatherburn (1967). Ruminal fluid samples for VFA analysis were thawed at room temperature and centrifuged (Eppendorf AG, Hamburg, Germany) at 3000 g for 20 min at 4 °C. In the supernatant, VFA concentrations were measured using a gas chromatograph (YL6100 GC; Young Lin Instrument, Anyang, South Korea) equipped with a 50-m (0.32 mm ID) silica-fused column (CP-Wax Chrompack Capillary Column; Varian, Palo Alto, CA, USA). Helium was used as the carrier gas, and initial and final oven temperatures were set at 55 and 195 °C respectively. Detector and injector temperatures were set at 250 °C. Crotonic acid (1 : 7 v/v) was used as the internal standard. Cholesterol, triglyceride, blood urea-N (BUN), total protein and glucose concentrations were determined by an automated biochemical analyser (Alcyon 300i; Abbott Labs, Abbott Park, IL, USA) using commercial kits (Pars Azmoon, Tehran, Iran) according to the manufacturer’s instructions. Statistical analysis
Data were statistically analysed according to a completely randomized design using the general linear model (GLM) procedure of SAS 9.1.3 (2001) (M/s SAS Institute, Cary, NC, USA). Significant differences between means of treatments were assessed by the Journal of Animal Physiology and Animal Nutrition © 2014 Blackwell Verlag GmbH
Essential oils, yeast and malate for growing lambs
Duncan’s test, and the differences between treatments were declared significant at p < 0.05. Results Dry matter intake and lamb performance
Addition of MEO, YC and malate affected neither DMI (p = 0.21) nor average daily gain (ADG) (p = 0.4) (Table 2). Final BW (p = 0.95) and feed conversion ratio (FCR) (p = 0.07) were also not affected by dietary treatment. Apparent total tract digestibility and N retention
Results of apparent total tract digestibility are shown in Table 3. Crude protein (CP) digestibility was higher (p < 0.05) in lambs fed MEO and YC than in lambs fed the control or malate diets. NDF digestibility for YC was higher (p < 0.05) compared to other treatments. Differences in DM, OM, ADF and starch digestibility were not significant between the treatments. N intake, N excretion and N balance were unaffected with MEO, YC or malate supplementation. N retention tended to be higher in lambs on the YC-supplemented diet (p < 0.06) than on the other diets. Rumen fermentation parameters
None of the experimental treatments affected ruminal pH and NH3-N concentration. Supplementing YC and malate increased the molar proportion of propionate (p < 0.05), whereas the concentration of total VFA, and the molar proportions acetate, butyrate, valerate and ratio of acetate to propionate were similar for all treatments (Table 4). Table 2 Effect of dietary supplementation with a mixture essential oil (MEO), yeast culture (YC) and malate (M) on performance of growing lambs Treatment Item
Control
MEO
YC
M
SEM*
Pvalue†
Dry matter intake (DMI), g/day Initial body weight (BW), kg Final BW‡, kg Feed conversion ratio§
885
822
796
881
33.1
0.22
17.0
17.4
17.1
17.8
1.02
0.92
29.6 4.22
29.4 4.19
29.5 3.83
30.3 4.27
0.31 0.35
0.72 0.74
*Standard error of mean. †Level of significance. ‡Feed and water were withdrawn for 8 h before lambs were weighed. §Total DMI/average daily gain.
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Table 3 Effect of dietary supplementation with a mixture essential oil (MEO), yeast culture (YC) and malate (M) on apparent digestibility coefficients and N balance of growing lambs Treatment Item
Control
MEO
Apparent digestibility coefficient, % Dry matter 76.6 79.0 Organic matter 77.6 80.6 Crude protein 76.6b 80.3a Neutral detergent 52.3c 54.2b fibre Acid detergent 46.0 48.6 fibre Starch 84.0 87.1 Nitrogen balance N intake, g/day 20.5 21.0 Faecal N, g/day 6.76 6.34 Urinary N, g/day 5.94 6.15 N balance, g/day 8.17 8.55 Retained N, % 39.1 40.6
YC
M
SEM*
Pvalue†
81.0 83.0 82.6a 61.0a
76.0 87.0 76.0b 53.3b
0.010 0.010 0.009 0.005
0.18 0.14 0.05). Compared with control and malate treatment, lambs fed MEO and YC had an improved crude protein digestibility (p < 0.05). Yeast culture significantly increased (p > 0.05) cell wall digestibility compared to the other treatments. No differences were observed between treatments with respect to nitrogen balance or ruminal pH and ammonia concentrations (p > 0.05). No differences were observed between treatments with respect to ruminal total volatile fatty acid concentration and molar proportions of acetate, butyrate and valerate. Molar proportion of propionate was higher (p < 0.05) for YC and malate compared to control and MEO. Plasma glucose concentration was higher (p < 0.05) in lambs fed YC and malate than in lambs fed the control or the MEO diet. Blood concentration of triglycerides significantly decreased when feeding the MEO and YC diets (p < 0.05). It was concluded that YC may be more useful as a feed additive for manipulation of rumen fermentation in lambs fed with high-concentrate diets than MEO and malate, because YC enhanced crude protein and cell wall digestibility, ruminal molar proportion of propionate and plasma glucose concentration. Keywords lamb, digestibility, mixture essential oils, yeast culture, malate Correspondence M. Malekkhahi, Department of Animal Science, Faculty of Agriculture, Ferdowsi University of Mashhad, P.O. Box: 91775-1163, Mashhad, Iran. Tel: +989151744289; Fax: +985118796545; E-mail: [email protected] Received: 31 October 2013; accepted: 30 June 2014
Introduction Intensive lamb fattening systems require highconcentrate diets to assure high productivity and fast growth (Mungoi et al., 2012) which causes ruminal acidosis and affects the ruminal microbial population (Gonzalez-Momita et al., 2009). Calsamiglia et al. (2012) referred such adversity as ‘high-concentrate syndrome’ and suggested to adopt strategies to modulate pH and fermentation pathways in the rumen with yeast, organic acids or essential oils (EO) to ameliorate the rumen environment. Essential oils are naturally occurring, secondary plant metabolites that can be
steam-volatilized or extracted using organic solvents. Limited literature exists that highlights the potential of EO to manipulate ruminal microbial fermentation and increase feed efficiency in ruminants (Calsamiglia et al., 2007). By providing growth factors including organic acids, B vitamins and amino acids that stimulate microbial growth in the rumen, Saccharomyces cerevisiae may stabilize ruminal fermentation (Chaucheyras-Durand et al., 2008). Callaway and Martin (1997) and Brossard et al. (2006) suggested that the yeast effects were due to the nutrients and/or soluble growth factors provided to the ruminal microbes. Unlike ionophores that
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