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Archives of Animal Nutrition Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/gaan20
Energy metabolism and methane production in llamas, sheep and goats fed high- and low-quality grass-based diets a
b
a
Mette O. Nielsen , Ali Kiani , Einstein Tejada , Andre Chwalibog
a
c
& Lene Alstrup a
Department of Veterinary Clinical and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Copenhagen, Denmark b
Animal Science Group, Faculty of Agricultural Sciences, Lorestan University, Khoramabad, Iran c
Department of Animal Science, Faculty of Science and Technology, Aarhus University, Aarhus, Denmark Published online: 29 May 2014.
To cite this article: Mette O. Nielsen, Ali Kiani, Einstein Tejada, Andre Chwalibog & Lene Alstrup (2014) Energy metabolism and methane production in llamas, sheep and goats fed high- and low-quality grass-based diets, Archives of Animal Nutrition, 68:3, 171-185, DOI: 10.1080/1745039X.2014.912039 To link to this article: http://dx.doi.org/10.1080/1745039X.2014.912039
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content.
Downloaded by [Karolinska Institutet, University Library] at 18:48 23 June 2014
This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/termsand-conditions
Archives of Animal Nutrition, 2014 Vol. 68, No. 3, 171–185, http://dx.doi.org/10.1080/1745039X.2014.912039
Energy metabolism and methane production in llamas, sheep and goats fed high- and low-quality grass-based diets Mette O. Nielsena*, Ali Kianib, Einstein Tejadaa, Andre Chwaliboga and Lene Alstrupc
Downloaded by [Karolinska Institutet, University Library] at 18:48 23 June 2014
a
Department of Veterinary Clinical and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Copenhagen, Denmark; bAnimal Science Group, Faculty of Agricultural Sciences, Lorestan University, Khoramabad, Iran; cDepartment of Animal Science, Faculty of Science and Technology, Aarhus University, Aarhus, Denmark (Received 12 January 2014; accepted 1 April 2014) This study aimed to test whether the digestive and metabolic characteristics of pseudo ruminants provide superior ability to utilise low-quality diets compared to true ruminants. A total of 18 mature, non-pregnant, non-lactating female animals, including six llamas (Lama glama), six Danish Landrace goats and six Shropshire sheep, were used in a crossover design study. The experiment lasted for two periods of three weeks. Half of the animals were fed either high-quality grass hay (HP) or low-quality grass seed straw (LP) during each period. Animals were placed in metabolic cages during the last 5 d, and gaseous exchange was measured by open-circuit indirect calorimetry for 22 h. Metabolisable energy for maintenance (MEm) and fasting energy expenditure (FEExp) were estimated by regression approach. Dry matter (DM) intake per kg0.75 was substantially reduced in llamas and sheep, but not in goats, on the LP compared to HP diet. Llamas had lower daily energy expenditure (324 kJ · kg−0.75) than sheep (416 kJ · kg−0.75) and goats (404 kJ · kg−0.75) on the LP diet. Llamas in comparison with sheep and goats had lower methane emission (0.83 vs 1.34 and 1.24 l · d−1 · kg−0.75, p < 0.05), lower MEm (328 vs 438 and 394 kJ · d−1 · kg−0.75, p < 0.05) and lower FEExp (246 vs 333 and 414 kJ · d−1 · kg−0.75, p < 0.05), respectively. In conclusion, llamas had lower basal metabolic rate and hence maintenance requirements for energy. Keywords: digestibility; energy expenditure; goats; llamas; methane production; nitrogen metabolism; sheep
1. Introduction The South American camelids (SAC) are a group of herbivorous animals consisting of llamas, alpacas, guanacos and vicuñas. SAC have an expanded foregut with substantial microbial fermentation; they perform rumination of ingested feed and have similar microorganisms and end products of fermentation as observed in other ruminant animals. Despite these similarities, the digestive tract in SAC differs from that of true ruminants both anatomically and functionally (Rübsamen and von Engelhardt 1979). SAC have three distinct stomach compartments (termed C1, C2 and C3), whereas true ruminants have four stomach compartments (rumen, reticulum, omasum and abomasum). Additionally, SAC have small saccules in both C1 and C2, which may have secretory function suggested to provide higher buffering capacity (Eckerlin and Stevens 1973; Dulphy et al. 1997). SAC have high absorptive capacity for end products of fermentation (i.e. volatile fatty acids) in their foregut (Heller et al. 1984). It has been reported that *Corresponding author. Email: [email protected] © 2014 Taylor & Francis
Downloaded by [Karolinska Institutet, University Library] at 18:48 23 June 2014
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llamas are able to digest plant cell walls more efficiently than sheep, especially when fed low-quality forage (Lemosquet et al. 1996). Higher buffer capacity (Eckerlin and Stevens 1973; Dulphy et al. 1997) combined with low passage rate of solids (San Martin and Bryant 1989) could potentially result in a more acetogenic and methanogenic environment. Consequently, llamas could be expected to release relatively larger amounts of the greenhouse gas methane from enteric fermentation. This study aimed to test the hypothesis that digestive and metabolic characteristics of llamas provide superior adaptability to low-quality diets over that of the true ruminants, but associated with greater emission of methane. To test this hypothesis, a comparative experiment was conducted with llamas, sheep and goats fed a high-quality diet consisting of artificially dried grass hay (14.8% crude protein [CP]) or a low-quality diet consisting of grass seed straw (6.2% CP).
2. Materials and methods 2.1. Animals and treatments The experiment was conducted at the experimental facility for large animals (Rørrendegård, Faculty of Health and Medical Sciences, University of Copenhagen, Hoeje Taastrup, Denmark). All experimental procedures were approved by the National Committee on Animal Experimentation, Denmark. Details regarding the experimental design, feeding and feed analyses have previously been published by Jalali et al. (2012). In short, a total of 18 animals including 6 llamas (Lama glama), 6 Danish Landrace goats and 6 Shropshire sheep were used. All animals were mature, nonpregnant, non-lactating females. Initial body weights of llamas, sheep and goats were 135 ± 20, 75 ± 6 and 45 ± 5 kg (mean ± SD), respectively. Prior to the onset of the experiment, all animals were given an anthelmintic treatment. The experiment consisted of two consecutive periods (Period I and Period II). Each period lasted three weeks, in which animals were fed to obtain approximately 10% refusals. The daily ration was divided into two equally sized meals given at 07:30 and 15:30 h. During each period, half of the animals within each species were fed high-quality dried green grass hay with 14.8% CP (Diet HP) and the other half was fed low-quality red fescue grass seed straw with 6.5% CP (Diet LP) content. Samples of different batches were taken and thoroughly mixed for nutrient content analysis (Table 1). Table 1. Dry matter (DM) contents and composition of high-quality green grass hay (HP) and lowquality grass seed straw (LP).*
Dry matter [%] Composition [% of DM] Crude protein Ether extract Ash Neutral detergent fibre Acid detergent fibre Acid detergent lignin
HP (n = 3)
LP (n = 2)
90.6 ± 0.6
91.8 ± 0.7
14.8 3.1 7.5 57.7 32.2 3.7
6.5 1.0 3.5 80.9 47.7 8.0
Note: *Values are expressed as mean ± standard deviation.
± ± ± ± ± ±
0.8 0.3 0.7 5.7 1.6 0.3
± ± ± ± ± ±
0.4 0.1 0.6 0.7 0.7 0.3
Archives of Animal Nutrition
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2.2. Balance and respiratory measurements Balance trials and respiratory measurements were conducted during the last 7 d of each period. Each balance trial lasted for 7 d, where the first 2 d served as an adaptation period without any collection, followed by 5 d of daily faeces, urine (collected in 60 ml 10% sulphuric acid and 10 ml citric acid) and feed residue collection. Each day, 10% of the total amounts of collections (faeces, urine and feed residue) were kept in plastic bags and stored in the freezer at –18°C for chemical analyses. An open-air circuit system (temperature 15– 18°C, humidity 65–75%, 12-h light–dark cycle) consisting of two respiration chambers was used to measure 22 h of respiratory gaseous exchange in the middle of each balance trial. Outgoing air was analysed every 3 min for the concentration of O2 using a paramagnetic analyser (Magnos 4G, Hartmann & Braun AG, Frankfurt, Germany) and for the concentrations of CO2 and CH4 using an infrared gas analyser (Uras 3, Hartmann & Braun AG). Respiration measurements could only be performed on four of the six llamas, as two llamas were too tall to enter the chambers. One goat became ill during respiration measurements in Period 2, and respiration data from this goat were excluded from both periods.
2.3. Chemical analysis Chemical analyses of feeds, feed refusals, faeces and urine samples from the experiment have been described in detail by Jalali et al. (2012). In short, dry matter (DM) content in feed and faeces was determined by drying at 60 and 105°C for 24 h, respectively, according to standard laboratory procedures, and ash was determined by combustion at 525°C for 16 h. The gross energy (GE) contents in feed and faeces were determined using an adiabatic bomb calorimeter (System C700, IKA Analysentechnic GmbH, Heitersheim, Germany). The nitrogen (N) contents in feed, faeces (NF) and urine (NU) were determined by a micro-Kjeldahl method using the Tecator-Kjeltec system 1026 (Tecator AB, Höganäs, Sweden). Ether extract was analysed by petroleum ether extraction after HCl hydrolysis using a Soxhlet system and according to AOAC (2004). Acid detergent fibre (ADF) was determined (ash free) according to AOAC (2004) and acid detergent lignin (ADL) in forage was determined (ash free) according to Van Soest et al. (1991). Neutral detergent fibre (NDF) concentration in forage was determined using the FibreCap system (FOSS Tecator AB, Höganäs, Sweden) and in faeces using the Ankom system (ANKOM Technology Co., Fairport, NY, USA) with heatstable α-amylase, but without sodium sulphite according to Mertens (2002).
2.4. Calculations CP, digestible energy (DE), energy excreted in urine (UE), energy loss in methane (MetE), metabolisable energy (ME) and N retention were calculated as: CP ½g ¼ N ½g 6:25; DE ½kJ ¼ GE ½kJ FE ½kJ; UE ½kJ ¼ UN ½g 139 ðHoffmann and Klein 1980Þ; MetE ½kJ ¼ CH4 ½l 39:6; ME ½kJ ¼ GE ½kJ FE ½kJ UE ½kJ MetE ½kJ; N retained ½g ¼ N intake ½g N excreted in faeces ½g N excreted in urine ½g:
174
M.O. Nielsen et al.
Energy expenditure (EExp) was calculated from the daily gaseous exchange and mean NU according to Brouwer (1965), as follows: EExp ½kJ ¼ 16:18 O2 ½l þ 5:02 CO2 ½l 2:17 CH4 ½l 5:99 NU ½g: Retained energy (RE) and respiratory quotient (RQ) were calculated as follows: RE ½kJ ¼ ME ½kJ EExp ½kJ;
Downloaded by [Karolinska Institutet, University Library] at 18:48 23 June 2014
RQ ¼ CO2 ½l=O2 ½l: Linear regression approaches were used to estimate the metabolisable energy for maintenance (MEm) and fasting energy expenditure (FEExp). MEm for each species was derived from these regressions as the ME corresponding to a RE = 0, and FEExp for each species was derived from regressions as the intercept when ME = 0.
2.5. Statistical analysis The data were statistically analysed using SAS/STAT® software, version 9.2 of the SAS system for windows, copyright © 2008 SAS Institute Inc., Cary, NC, USA. Data were initially checked for normal distribution using Shapiro–Wilk test, and homogeneity of variance was evaluated by visual inspection of residual plots. Data were analysed as a crossover design with two forages (D: HP and LP) and three species (S: llama, sheep and goat) studied in two different periods (P: 1 and 2) and allocated to treatments in two different sequences (SEQ: HP followed by LP or LP followed by HP). The MIXED procedure was used for statistical analysis, where the main effects of S, D, SEQ, P and interaction of S × D were included as fixed effects and ANIMAL as random effect. Interaction means are presented if the interactions were significant; otherwise the means of main effects are presented. Effects were declared significant at p < 0.05 in the F-test. Paired t-test (PDIFF option of MIXED) was used to examine simple treatment effects when interactions existed. The linear regression between ME intake and RE was analysed by the REG procedure, and regression coefficients were compared across the three species according to Bruin (2006).
3. Results 3.1. Dietary intakes, dry matter and protein digestibility The body weight of llamas was almost twice as high as that of sheep, which in turn weighed almost twice as much as goats, which obviously impacted the ad libitum feed intake of the animals (Table 2). To allow comparisons between species independently of the body weight differences, other data were expressed either as percentages (e.g. digestibility values) or relative to the metabolic body weight [kg0.75] of the animals. Intakes of DM [g/kg0.75] and GE [kJ/kg0.75] were significantly higher (p < 0.01) on the HP compared to the LP diet for llamas and sheep (Table 2). Sheep had significantly higher (p < 0.01) DM, CP and GE intake [g/kg0.75] than both llamas and goats on the HP diet. On the LP diet, llamas had lower DM and GE intakes [g/kg0.75] than sheep and goats (Table 2). The DM digestibility (62.3 vs 41.2%, p < 0.001) and GE digestibility (61.2 vs 39.3%, p < 0.001) were markedly higher for the HP diet compared to the LP diet, but no
0.89b 0.36d 0.28bc 0.25a 5.0b 0.97bc 31.1bc
37.4bc 5.5b 706 bc 441 b 364 a
44.4e 17.2e
Goat n=6
0.28c 0.39cd 0.14d −0.25c 11.2a 0.52c 51.6ab
25.0d 1.7c 475 d 189 c 131 b
132.3b 38.9b
Llama n=6
0.40c 0.49ab 0.13d −0.22c 6.7b 0.68bc 30.8bc
35.9c 2.5c 682c 244c 184b
71.8d 24.7d
Sheep n=6
Diet LP
0.40c 0.43bc 0.20cd −0.23c 5.7b 0.60bc 50.3abc
35.8c 2.5c 681c 288c 219b
44.9e 17.3e
Goat n=6
0.05 0.03 0.03 0.06 1.2 0.20 10.8
5.7 0.7 44 37 45
4.95 1.10
SEM*
Archives of Animal Nutrition Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/gaan20
Energy metabolism and methane production in llamas, sheep and goats fed high- and low-quality grass-based diets a
b
a
Mette O. Nielsen , Ali Kiani , Einstein Tejada , Andre Chwalibog
a
c
& Lene Alstrup a
Department of Veterinary Clinical and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Copenhagen, Denmark b
Animal Science Group, Faculty of Agricultural Sciences, Lorestan University, Khoramabad, Iran c
Department of Animal Science, Faculty of Science and Technology, Aarhus University, Aarhus, Denmark Published online: 29 May 2014.
To cite this article: Mette O. Nielsen, Ali Kiani, Einstein Tejada, Andre Chwalibog & Lene Alstrup (2014) Energy metabolism and methane production in llamas, sheep and goats fed high- and low-quality grass-based diets, Archives of Animal Nutrition, 68:3, 171-185, DOI: 10.1080/1745039X.2014.912039 To link to this article: http://dx.doi.org/10.1080/1745039X.2014.912039
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content.
Downloaded by [Karolinska Institutet, University Library] at 18:48 23 June 2014
This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/termsand-conditions
Archives of Animal Nutrition, 2014 Vol. 68, No. 3, 171–185, http://dx.doi.org/10.1080/1745039X.2014.912039
Energy metabolism and methane production in llamas, sheep and goats fed high- and low-quality grass-based diets Mette O. Nielsena*, Ali Kianib, Einstein Tejadaa, Andre Chwaliboga and Lene Alstrupc
Downloaded by [Karolinska Institutet, University Library] at 18:48 23 June 2014
a
Department of Veterinary Clinical and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Copenhagen, Denmark; bAnimal Science Group, Faculty of Agricultural Sciences, Lorestan University, Khoramabad, Iran; cDepartment of Animal Science, Faculty of Science and Technology, Aarhus University, Aarhus, Denmark (Received 12 January 2014; accepted 1 April 2014) This study aimed to test whether the digestive and metabolic characteristics of pseudo ruminants provide superior ability to utilise low-quality diets compared to true ruminants. A total of 18 mature, non-pregnant, non-lactating female animals, including six llamas (Lama glama), six Danish Landrace goats and six Shropshire sheep, were used in a crossover design study. The experiment lasted for two periods of three weeks. Half of the animals were fed either high-quality grass hay (HP) or low-quality grass seed straw (LP) during each period. Animals were placed in metabolic cages during the last 5 d, and gaseous exchange was measured by open-circuit indirect calorimetry for 22 h. Metabolisable energy for maintenance (MEm) and fasting energy expenditure (FEExp) were estimated by regression approach. Dry matter (DM) intake per kg0.75 was substantially reduced in llamas and sheep, but not in goats, on the LP compared to HP diet. Llamas had lower daily energy expenditure (324 kJ · kg−0.75) than sheep (416 kJ · kg−0.75) and goats (404 kJ · kg−0.75) on the LP diet. Llamas in comparison with sheep and goats had lower methane emission (0.83 vs 1.34 and 1.24 l · d−1 · kg−0.75, p < 0.05), lower MEm (328 vs 438 and 394 kJ · d−1 · kg−0.75, p < 0.05) and lower FEExp (246 vs 333 and 414 kJ · d−1 · kg−0.75, p < 0.05), respectively. In conclusion, llamas had lower basal metabolic rate and hence maintenance requirements for energy. Keywords: digestibility; energy expenditure; goats; llamas; methane production; nitrogen metabolism; sheep
1. Introduction The South American camelids (SAC) are a group of herbivorous animals consisting of llamas, alpacas, guanacos and vicuñas. SAC have an expanded foregut with substantial microbial fermentation; they perform rumination of ingested feed and have similar microorganisms and end products of fermentation as observed in other ruminant animals. Despite these similarities, the digestive tract in SAC differs from that of true ruminants both anatomically and functionally (Rübsamen and von Engelhardt 1979). SAC have three distinct stomach compartments (termed C1, C2 and C3), whereas true ruminants have four stomach compartments (rumen, reticulum, omasum and abomasum). Additionally, SAC have small saccules in both C1 and C2, which may have secretory function suggested to provide higher buffering capacity (Eckerlin and Stevens 1973; Dulphy et al. 1997). SAC have high absorptive capacity for end products of fermentation (i.e. volatile fatty acids) in their foregut (Heller et al. 1984). It has been reported that *Corresponding author. Email: [email protected] © 2014 Taylor & Francis
Downloaded by [Karolinska Institutet, University Library] at 18:48 23 June 2014
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M.O. Nielsen et al.
llamas are able to digest plant cell walls more efficiently than sheep, especially when fed low-quality forage (Lemosquet et al. 1996). Higher buffer capacity (Eckerlin and Stevens 1973; Dulphy et al. 1997) combined with low passage rate of solids (San Martin and Bryant 1989) could potentially result in a more acetogenic and methanogenic environment. Consequently, llamas could be expected to release relatively larger amounts of the greenhouse gas methane from enteric fermentation. This study aimed to test the hypothesis that digestive and metabolic characteristics of llamas provide superior adaptability to low-quality diets over that of the true ruminants, but associated with greater emission of methane. To test this hypothesis, a comparative experiment was conducted with llamas, sheep and goats fed a high-quality diet consisting of artificially dried grass hay (14.8% crude protein [CP]) or a low-quality diet consisting of grass seed straw (6.2% CP).
2. Materials and methods 2.1. Animals and treatments The experiment was conducted at the experimental facility for large animals (Rørrendegård, Faculty of Health and Medical Sciences, University of Copenhagen, Hoeje Taastrup, Denmark). All experimental procedures were approved by the National Committee on Animal Experimentation, Denmark. Details regarding the experimental design, feeding and feed analyses have previously been published by Jalali et al. (2012). In short, a total of 18 animals including 6 llamas (Lama glama), 6 Danish Landrace goats and 6 Shropshire sheep were used. All animals were mature, nonpregnant, non-lactating females. Initial body weights of llamas, sheep and goats were 135 ± 20, 75 ± 6 and 45 ± 5 kg (mean ± SD), respectively. Prior to the onset of the experiment, all animals were given an anthelmintic treatment. The experiment consisted of two consecutive periods (Period I and Period II). Each period lasted three weeks, in which animals were fed to obtain approximately 10% refusals. The daily ration was divided into two equally sized meals given at 07:30 and 15:30 h. During each period, half of the animals within each species were fed high-quality dried green grass hay with 14.8% CP (Diet HP) and the other half was fed low-quality red fescue grass seed straw with 6.5% CP (Diet LP) content. Samples of different batches were taken and thoroughly mixed for nutrient content analysis (Table 1). Table 1. Dry matter (DM) contents and composition of high-quality green grass hay (HP) and lowquality grass seed straw (LP).*
Dry matter [%] Composition [% of DM] Crude protein Ether extract Ash Neutral detergent fibre Acid detergent fibre Acid detergent lignin
HP (n = 3)
LP (n = 2)
90.6 ± 0.6
91.8 ± 0.7
14.8 3.1 7.5 57.7 32.2 3.7
6.5 1.0 3.5 80.9 47.7 8.0
Note: *Values are expressed as mean ± standard deviation.
± ± ± ± ± ±
0.8 0.3 0.7 5.7 1.6 0.3
± ± ± ± ± ±
0.4 0.1 0.6 0.7 0.7 0.3
Archives of Animal Nutrition
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2.2. Balance and respiratory measurements Balance trials and respiratory measurements were conducted during the last 7 d of each period. Each balance trial lasted for 7 d, where the first 2 d served as an adaptation period without any collection, followed by 5 d of daily faeces, urine (collected in 60 ml 10% sulphuric acid and 10 ml citric acid) and feed residue collection. Each day, 10% of the total amounts of collections (faeces, urine and feed residue) were kept in plastic bags and stored in the freezer at –18°C for chemical analyses. An open-air circuit system (temperature 15– 18°C, humidity 65–75%, 12-h light–dark cycle) consisting of two respiration chambers was used to measure 22 h of respiratory gaseous exchange in the middle of each balance trial. Outgoing air was analysed every 3 min for the concentration of O2 using a paramagnetic analyser (Magnos 4G, Hartmann & Braun AG, Frankfurt, Germany) and for the concentrations of CO2 and CH4 using an infrared gas analyser (Uras 3, Hartmann & Braun AG). Respiration measurements could only be performed on four of the six llamas, as two llamas were too tall to enter the chambers. One goat became ill during respiration measurements in Period 2, and respiration data from this goat were excluded from both periods.
2.3. Chemical analysis Chemical analyses of feeds, feed refusals, faeces and urine samples from the experiment have been described in detail by Jalali et al. (2012). In short, dry matter (DM) content in feed and faeces was determined by drying at 60 and 105°C for 24 h, respectively, according to standard laboratory procedures, and ash was determined by combustion at 525°C for 16 h. The gross energy (GE) contents in feed and faeces were determined using an adiabatic bomb calorimeter (System C700, IKA Analysentechnic GmbH, Heitersheim, Germany). The nitrogen (N) contents in feed, faeces (NF) and urine (NU) were determined by a micro-Kjeldahl method using the Tecator-Kjeltec system 1026 (Tecator AB, Höganäs, Sweden). Ether extract was analysed by petroleum ether extraction after HCl hydrolysis using a Soxhlet system and according to AOAC (2004). Acid detergent fibre (ADF) was determined (ash free) according to AOAC (2004) and acid detergent lignin (ADL) in forage was determined (ash free) according to Van Soest et al. (1991). Neutral detergent fibre (NDF) concentration in forage was determined using the FibreCap system (FOSS Tecator AB, Höganäs, Sweden) and in faeces using the Ankom system (ANKOM Technology Co., Fairport, NY, USA) with heatstable α-amylase, but without sodium sulphite according to Mertens (2002).
2.4. Calculations CP, digestible energy (DE), energy excreted in urine (UE), energy loss in methane (MetE), metabolisable energy (ME) and N retention were calculated as: CP ½g ¼ N ½g 6:25; DE ½kJ ¼ GE ½kJ FE ½kJ; UE ½kJ ¼ UN ½g 139 ðHoffmann and Klein 1980Þ; MetE ½kJ ¼ CH4 ½l 39:6; ME ½kJ ¼ GE ½kJ FE ½kJ UE ½kJ MetE ½kJ; N retained ½g ¼ N intake ½g N excreted in faeces ½g N excreted in urine ½g:
174
M.O. Nielsen et al.
Energy expenditure (EExp) was calculated from the daily gaseous exchange and mean NU according to Brouwer (1965), as follows: EExp ½kJ ¼ 16:18 O2 ½l þ 5:02 CO2 ½l 2:17 CH4 ½l 5:99 NU ½g: Retained energy (RE) and respiratory quotient (RQ) were calculated as follows: RE ½kJ ¼ ME ½kJ EExp ½kJ;
Downloaded by [Karolinska Institutet, University Library] at 18:48 23 June 2014
RQ ¼ CO2 ½l=O2 ½l: Linear regression approaches were used to estimate the metabolisable energy for maintenance (MEm) and fasting energy expenditure (FEExp). MEm for each species was derived from these regressions as the ME corresponding to a RE = 0, and FEExp for each species was derived from regressions as the intercept when ME = 0.
2.5. Statistical analysis The data were statistically analysed using SAS/STAT® software, version 9.2 of the SAS system for windows, copyright © 2008 SAS Institute Inc., Cary, NC, USA. Data were initially checked for normal distribution using Shapiro–Wilk test, and homogeneity of variance was evaluated by visual inspection of residual plots. Data were analysed as a crossover design with two forages (D: HP and LP) and three species (S: llama, sheep and goat) studied in two different periods (P: 1 and 2) and allocated to treatments in two different sequences (SEQ: HP followed by LP or LP followed by HP). The MIXED procedure was used for statistical analysis, where the main effects of S, D, SEQ, P and interaction of S × D were included as fixed effects and ANIMAL as random effect. Interaction means are presented if the interactions were significant; otherwise the means of main effects are presented. Effects were declared significant at p < 0.05 in the F-test. Paired t-test (PDIFF option of MIXED) was used to examine simple treatment effects when interactions existed. The linear regression between ME intake and RE was analysed by the REG procedure, and regression coefficients were compared across the three species according to Bruin (2006).
3. Results 3.1. Dietary intakes, dry matter and protein digestibility The body weight of llamas was almost twice as high as that of sheep, which in turn weighed almost twice as much as goats, which obviously impacted the ad libitum feed intake of the animals (Table 2). To allow comparisons between species independently of the body weight differences, other data were expressed either as percentages (e.g. digestibility values) or relative to the metabolic body weight [kg0.75] of the animals. Intakes of DM [g/kg0.75] and GE [kJ/kg0.75] were significantly higher (p < 0.01) on the HP compared to the LP diet for llamas and sheep (Table 2). Sheep had significantly higher (p < 0.01) DM, CP and GE intake [g/kg0.75] than both llamas and goats on the HP diet. On the LP diet, llamas had lower DM and GE intakes [g/kg0.75] than sheep and goats (Table 2). The DM digestibility (62.3 vs 41.2%, p < 0.001) and GE digestibility (61.2 vs 39.3%, p < 0.001) were markedly higher for the HP diet compared to the LP diet, but no
0.89b 0.36d 0.28bc 0.25a 5.0b 0.97bc 31.1bc
37.4bc 5.5b 706 bc 441 b 364 a
44.4e 17.2e
Goat n=6
0.28c 0.39cd 0.14d −0.25c 11.2a 0.52c 51.6ab
25.0d 1.7c 475 d 189 c 131 b
132.3b 38.9b
Llama n=6
0.40c 0.49ab 0.13d −0.22c 6.7b 0.68bc 30.8bc
35.9c 2.5c 682c 244c 184b
71.8d 24.7d
Sheep n=6
Diet LP
0.40c 0.43bc 0.20cd −0.23c 5.7b 0.60bc 50.3abc
35.8c 2.5c 681c 288c 219b
44.9e 17.3e
Goat n=6
0.05 0.03 0.03 0.06 1.2 0.20 10.8
5.7 0.7 44 37 45
4.95 1.10
SEM*
