J. Anim. Sci. 2006. 84:162-170
© 2006 American Society of Animal Science
Effect of refined coconut oil or copra meal on methane output and on intake and performance of beef heifers1
E. Jordan2,
D. K. Lovett,
F. J. Monahan3,
J. Callan,
B. Flynn and
F. P. O’Mara
Department of Animal Science, University College Dublin, Lyons Research Farm, Newcastle, Co. Dublin, Ireland
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Abstract
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An experiment was conducted to establish the effect of feeding either refined coconut oil (CO) or copra meal containing CO to beef heifers on DMI, animal performance, enteric CH4 emissions, diet digestibility, and the fatty acid profile of the resulting meat. Forty-one Charolais and Limousin crossbred beef heifers (474 ± 29 kg; 661 ± 89 d of age) were blocked by BW before being assigned in a randomized complete block design to 1 of 3 experimental treatments (n = 12) or to a pretrial slaughter group (n = 5) used to determine the initial carcass weight. The experimental period lasted for 93 d. Enteric CH4 output was recorded for 2 periods of 5 consecutive days from d 14 to 18 and from d 70 to 74. The 3 dietary treatments were 1) control, a barley/soybean meal-based concentrate with 0 g of CO/ d; 2) RCO, a barley/soybean meal-based concentrate with 250 g of CO/d from refined coconut oil; and 3) CM, a copra meal-based concentrate with 250 g of CO/d from copra meal. Each diet had a 50:50 forage:concentrate using grass silage as the forage source. There was no effect of diet on DMI (P = 0.734) or GE intake (P = 0.486). The addition of RCO increased ADG (P < 0.05) compared with the control treatment. The CM treatment decreased (P < 0.05) average daily carcass gain compared with the RCO treatment only. There was a decrease (P < 0.05) in the digestibility of the DM, OM, CP, and GE fractions of the diet only with the CM treatment. Both the RCO and CM concentrates decreased (P < 0.001) daily enteric CH4 output when expressed in terms of liters per day, liters per kilogram of DMI, percentage of GE intake, liters per kilogram of ADG, and liters per kilogram of average daily carcass gain. The RCO treatment produced the greatest numerical response for all measures. Ruminal protozoa numbers on the RCO treatment were lower (P < 0.05) than on the control treatment. The concentrations of the fatty acid methyl esters, lauric (P < 0.001) and myristic (P < 0.002) acids, were increased in muscle when either of the CCO treatments was compared with the controls, but the differences were of a magnitude unlikely to influence human health status. Although the CM concentrate decreased CH4 comparable with the RCO concentrate, decreased performance resulted in an extended finishing time with implications for lifetime CH4 emissions.
Key Words: beef heifer • coconut oil • copra meal • enteric methane • fatty acid profile
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INTRODUCTION
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There is new and stronger evidence that most of the warming observed over the last 50 yr is attributable to human activity (IPCC, 2001
). This increase in the earth’s temperature is considered one of the most important global environmental issues. Enteric CH4 contributes approximately 33% of the European Union’s agricultural greenhouse gas emissions (EEA, 2003) and 27% of US agriculture’s emissions (EPA, 2003). Literature records various CH4 mitigation strategies (Van Nevel and Demeyer, 1996; Ushida et al., 1997; McCrabb et al., 1998); the process of defaunation has particular merit. Fats and oils have been used to defaunate the rumen (Dong et al., 1997). The decrease in CH4 output is source-dependent, and coconut oil (CO) is particularly effective (Machmüller et al., 1998). Our institution identified decreases of 26% in enteric CH4 output from beef heifers when 350 g of CO/d were fed (Lovett et al., 2003); however, a decrease in DMI also was noted. Further work (Jordan et al., 2004) establishing the response to increasing levels of CO within a fixed for-age:concentrate for similar animals identified that a level of 250 g of CO/d produced decreases (P < 0.001) in CH4 output and did not adversely affect DMI. Refined coconut oil is a high-cost feed ingredient; thus, the use of alternative sources of CO such as copra meal could decrease costs. A consideration when feeding CO is that its principal SFA, lauric and myristic, have been associated with increased levels of low density lipoprotein (LDL) cholesterol in humans (Grundy, 1994). The aim of this experiment, using a 50:50 forage:concentrate and ad libitum feeding conditions, was to establish the response to 250 g of CO/d, contained within a barley/ soybean- or copra meal-based concentrate, on DMI, enteric CH4 output, animal performance, diet digestibility, and the fatty acid composition of the meat produced under large-scale production conditions.
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MATERIALS AND METHODS
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Animals, Experimental Design, and Treatments
The experiment used 41 crossbred (Charolais and Limousin) beef heifers (474 ± 29 kg; 661 ± 89 d of age) that were blocked by BW. Animals were then assigned in a randomized complete block design to 1 of 3 experimental treatments (n = 12) or to a pretrial slaughter group (n = 5) used to determine the initial carcass weight. The experimental period lasted for 93 d; enteric CH4 output was recorded for 2 periods of 5 consecutive days from d 14 to 18 and from d 70 to 74. The 3 dietary treatments were 1) control, a barley/soybean meal-based concentrate with 0 g of CO/d; 2) barley/soybean meal-based concentrate (RCO) with 250 g of CO/d from refined coconut oil; and 3) copra meal-based concentrate (CM) with 250 g of CO/d from copra meal, all contained within a 50:50 forage:concentrate diet using grass silage as the forage source (Table 1).
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Table 1. Ingredient composition (g/kg, as-fed basis) and chemical analyses (g/kg of DM unless otherwise stated) of the diets
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Housing, Feeding Regimen, and Slaughter
During the CH4 measurement periods, animals were housed individually in 3' x 8' tie-stalls. At all other times during the experimental period, the animals were group-penned in a slatted-floor house and fed individually using a Calan Broadbent Feeding System (American Calan, Northwood, NH). For the entire experimental period, animals were fed 50:50 forage:concentrate ad libitum. Four concentrates were formulated: 3 treatment concentrates (control, RCO, and CM) and a balancer concentrate to maintain the 50:50 forage:concentrate ratio on a DM basis. The 3 treatment concentrates were formulated so that the target level of CO was contained within a daily 3.5-kg allowance, and the balancer concentrate was fed as required to maintain the 50:50 forage:concentrate. All concentrates were formulated to be isonitrogenous and to contain Ca, P, and Na at a rate of 8, 6, and 2 g/kg (as-fed basis), respectively. Grass silage was fed once daily using a Calan Data Ranger feeder (American Calan), whereas concentrates were fed in three equal feedings between 0900 and 1730. The ingredient proportions of the four concentrates are shown in Table 1
. Twelve hours before slaughter, the animals were transported to a commercial slaughter facility and slaughtered immediately the following day. Each carcass side was hung conventionally by the Achilles tendon and chilled for 48 h at 4°C before meat sampling.
Measurements and Sampling
Intake.
Dry matter intake was determined by daily weighing in and weighing out feed offered, separating forage and concentrate components as required, and correcting for the DM content of each dietary component. Feedstuffs offered were sampled daily; weekly composites of silage and concentrate samples were stored at –20°C. Silage orts were sampled twice weekly and bulked per treatment. Silage DM, oven-dried at 55°C for 72 h, and silage pH, measured using a Mettler Toledo pH meter (MP 200; Mason Technology, Dublin, Ireland), were determined daily for fresh silage, whereas oven DM concentration was determined twice weekly for silage orts. Feed samples collected daily during the experimental period were pooled to provide three samples for subsequent chemical analysis: d 1 to 42, d 43 to 72, and d 73 to 93.
Enteric Methane Output and Ruminal Protozoal Population.
Daily CH4 emissions were measured from d 14 to 18 and from d 70 to 74 using a modification of the SF6 (sulfur hexafluoride) tracer gas technique of Johnson et al. (1994), as previously described by Lovett et al. (2003). The ruminal contents were sampled immediately after slaughter and strained through 2 layers of cheesecloth. This ruminal fluid sample was preserved in methyl green formalin solution in a 1:10 ruminal fluid:preservative solution for subsequent ruminal protozoa population enumeration. A second sample was preserved in HgCl2 (70 mM) in a 1:20 preservative solution:ruminal fluid and subsequently used for determination of VFA concentration.
Diet Digestibility.
Diet digestibility was determined by use of the chromic oxide tracer technique (Williams et al., 1962). Six animals per dietary treatment were chosen at random and dosed twice daily (1 g of Cr2O3 contained within gelatin boluses) from d 70 to 74 inclusive. Fecal grab samples were taken at 6-h intervals on d 73 and 74 of the experimental period. Fecal samples were stored at –20°C and subsequently thawed and pooled on a fresh basis to have one sample per animal in each period for analysis of Cr concentration.
Animal Performance.
Average daily gain was calculated as the difference between the initial and final BW divided by the total number of days of feeding (n = 93). Live BW measurements were the average of 2 weights taken before feeding on consecutive days. Average daily carcass gain (ADCG) was calculated as the difference between the initial carcass weight (determined as 48% of the initial BW, based on the pretrial slaughter group) and the final cold carcass weight, divided by the total number of days feeding. Gain efficiency was calculated as daily kilograms of gain/kilogram of DMI, and carcass G:F was calculated as ADCG/daily DMI. Cold carcass weight (98% of HCW), carcass conformation and fat score (based on the European Union beef classification system with 5 carcass classification grades [E, U, R, O, and P, where E is best and P is poorest] and 6 fat grades [1, 2, 3, 4L, 4H, and 5, where 1 is leanest and 5 is fattest] determined subjectively by an official of the Dep. of Agriculture and Food), and dressing percentage (cold carcass weight/final BW) were determined immediately after slaughter. The kidney and channel fat was removed from the animal at slaughter and weighed.
Meat Sampling.
Carcass sides were split (pistola cut) into fore and hindquarters. A strip loin sample (approximately 2.5-cm thickness taken between the 11th and 12th rib junction) was taken from the right side of each carcass 48 h after slaughter. Strip loin samples were vacuum-packed and stored at –20°C for subsequent fatty acid analysis.
Laboratory Analyses
Dried feed and fecal samples were ground in a hammer mill fitted with a 1-mm screen before being analyzed in duplicate. Crude protein concentrations of concentrates and feces were determined as N x 6.25 using a Leco FP 528 instrument (Leco Instruments UK Ltd., Cheshire, UK) according to the method of Dumas (AOAC, 1990). Crude protein concentration of fresh grass silage was determined in duplicate as Kjeldahl N x 6.25 using a Buchi 435 digestion unit and a Buchi 323 distillation unit (Buchi, Postfach, Flawil/Schweiz, Switzerland) according to AOAC (1990). Crude fiber of the concentrates was determined by the Weende method (AOAC, 1990), whereas NDF, ADF, and ADL were determined using a Fibertec system (Tecator, Hoganas, Sweden) according to the methods of Van Soest (1973) and Van Soest et al. (1991). Ash concentration was determined after ignition at 550°C for 4 h in a muffle furnace and used to calculate OM. The GE of concentrates and feces was determined using a Parr 1201 oxygen bomb calorimeter (Parr, Moline, IL), and the GE of the grass silage was determined according to the method of Porter (1992). Ether extract within the concentrates was measured using a Soxtec instrument (Tecator). The buffering capacity of the fresh grass silage was determined by the method of Playne and Mc-Donald (1996), and NH3 N concentrations were determined using a modification of the 5.5.2 distillation method (EEC, 1985). Dry matter concentrations of the concentrates were determined in an oven at 104°C for a minimum of 16 h. The Cr concentration of the feces was determined using an inductively coupled plasma emission spectrophotometer (Varian Liberty 200; Varian, Australia Ltd., Mulgrave, Victoria) after extraction according to the method of Williams et al. (1962). The digestibilities of DM, OM, CP, NDF, ADF, and GE were subsequently calculated. Concentrations of CH4 and SF6 in breath were determined by gas chromatography using a Varian 3800 gas chromatograph (Varian BC, Middelburg, The Netherlands) as described by Lovett et al. (2003). The relative molar concentrations of the VFA (acetic, propionic, and butyric) in the ruminal fluid were determined by gas chromatography (Varian 3800) using a CP-wax 58, 25-m x 0.53-mm capillary column (Varian BC) according to the method of Porter and Murray (2001). Ruminal ciliate protozoa numbers were determined using a 0.1-mm depth Bürker counting chamber (Rudolf Brand, Wertheim, Germany); duplicate counts were measured for each sample. To determine the fatty acid concentration of the concentrate and muscle tissue samples, the fat was extracted according to the method of Folch et al. (1957). Fatty acid methyl esters (FAME) were then prepared according to the method of Slover and Lanza (1979). Gas chromatographic analysis of the FAME was then performed using a Unicam ProGC+ (Thermo Onix, Cambridge, UK) instrument; FAME were separated on a 30-m x 0.53-µm i.d. capillary column coated with Carbowax 20M to a film thickness of 1.0 µm. The initial column temperature was 120°C, which was then ramped at 6°C/min to 220°C and held at that temperature for 10 min. The carrier gas was H2, and the instrument was operated in constant pressure mode at a pressure of 0.4 kg/cm2 (5 lb/in2). Integration of individual peaks was carried out using Chromquest version 3.0 software (Thermoquest Corporation, Cambridge, UK). Individual peaks were identified by comparison with standard fat samples (beef tallow, fish oil, linseed oil, olive oil, sunflower oil, and CO); results were expressed as a percentage of total identified FAME.
Statistical Analyses
The treatment effect of feeding RCO or CM on CH4 output (L/d), DMI (kg/d), and CH4 (L/kg of DMI; L/kg of ADG; L/kg of ADCG; and as percentage of GE intake [GEI], MJ/d) was estimated by REML. The fixed effects in the model included day, period, and diet. Two- and 3-way interactions in the fixed model were not tested for. The random effects in the model included animal, animal x period, and animal x period x day. Response variables with no period effect, DMI for total experiment, GEI for total experiment, percentage of forage in diet, ADG, ADCG, dressing percentage, carcass fat score, carcass confirmation score, kidney channel fat weight, G:F, carcass G:F, ruminal VFA, protozoa numbers, digestibility coefficients, and FAME were analyzed according to a randomized complete block design, and animal, block, and diet were included in the model. All analyses were conducted using Genstat (Version 6; Lawes Agricultural Trust, Harpenden, Rothamsted Experimental Station, Hertfordshire, UK, 1999).
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RESULTS
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The composition of the experimental feeds is shown in Table 1. The concentrates ranged in CP concentration from 215 to 225 g/kg of DM. The NDF fraction of the RCO concentrate was lower than the balancer or control concentrates because CO replaced barley in the diet. The CM concentrate had greater NDF and ADF fractions because of the high NDF (649 g/kg of DM) and ADF (331 g/kg of DM) concentrations in copra meal. The RCO and CM concentrates also had a greater mean GE value (19.82 MJ/kg of DM) than the balancer or control concentrates because of the higher oil concentrations.
There was no effect of diet on DMI (P = 0.92, P = 0.73) or GEI (P = 0.71, P = 0.49) during either the CH4 measurement periods or over the entire experimental period, respectively (Table 2). The observed forage:concentrate was greater (P = 0.01) for the CM-fed animals, but this difference was small. For all treatments, the forage:concentrate was close to the target value.
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Table 2. Effect of refined coconut oil or copra meal supplementation on DMI, GE intake, and percentage of forage in the diet
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Mean ADG for animals receiving no CO was 1.08 kg/d (Table 3). Following individual treatment comparisons, the addition of RCO to the diet increased ADG (P = 0.03) compared with the control treatment, and the inclusion of CM in the diet decreased ADCG (P = 0.05) compared with the RCO treatment. Gain efficiency was less (P = 0.02) for the control treatment than for the RCO treatment, reflecting the lower ADG for the RCO treatment. The addition of dietary RCO or CM had no effect (P = 0.06 to P = 0.89) on dressing percentage, kidney and channel fat weight, confirmation score, and fat score (Table 3).
There was a decrease (P < 0.05) in the digestibility of the DM, OM, CP, and GE fractions of the diet for the CM treatment only (Table 4). There was no treatment effect (P > 0.20) observed for any of the remaining dietary fractions.
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Table 4. Digestibility coefficients (g/kg) and DE content for control, refined coconut oil, and copra meal treatment diets
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Mean daily CH4 output for animals receiving no CO was 334 L/d. The inclusion of RCO or CM within the diet resulted in a decrease (P < 0.001) in daily enteric CH4 output when expressed as both liters per day and liters per kilogram of DMI. A period effect (P = 0.01) was observed when CH4 output was expressed in terms of liters per kilogram of DMI, whereas no period effect was observed for CH4 output in liters per day. The addition of RCO or CM decreased (P < 0.001) CH4 output expressed as a percentage of GE, liters per kilogram of ADG, and liters per kilogram of ADCG; RCO produced the greatest numerical response for all measures. Period effects (P < 0.001) also were observed for CH4 output expressed as a percentage of GEI (Table 5).
The addition of dietary RCO or CM decreased (P = 0.02) the total molar concentrations of acetic, propionic, and butyric acid; however, no effects on the proportions of acetic (P = 0.19), propionic (P = 0.22), and butyric (P = 0.51) acids were observed across treatments. Ruminal protozoa numbers also were not (P < 0.06) affected by treatment, but when individual treatment comparisons were considered, protozoa numbers on the control diet were greater (P = 0.05) than those on the RCO diets (Table 6).
Analysis of the FAME identified significant differences in the level of C12:0 (P < 0.001) and C14:0 (P = 0.002) between the muscle of the control and the RCO and CM treatments. No other fatty acids were affected by diet (Table 7).
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DISCUSSION
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Intake
A decrease in DMI from the inclusion of CO has been widely reported (Sutton et al., 1983; Machmüller and Kreuzer, 1999; Lovett et al., 2003); however, no significant difference in DMI was observed in this experiment. This maintenance of DMI is in agreement with previous work at this institution (Jordan et al., 2004) using daily CO levels of 250 g fed to similar animals. We observed that feeding CO up to 250 g/d produced significant decreases in daily enteric CH4 emissions and also maintained DMI. Based on those results, we chose the level of CO fed in the current experiment. The lower levels of CO (2.6% of DM) used in these experiments compared with levels of 
7% of DM in the experiments of Sutton et al. (1983) and Machmüller and Kreuzer (1999) might account for this contrast. Gross energy intake also was unaffected by the inclusion of CO in the diet, even though the 2 concentrates containing CO, RCO (19.9 MJ/kg of DM), and CM (19.7 MJ/kg of DM) had greater GE values than the control (18.5 MJ/kg of DM) concentrate. This result can be attributed to animals receiving only 3.5 kg of their daily concentrate intake from the treatment concentrates and the remainder from the balancer concentrate. This absence of a significant difference in GEI is in agreement with previous work using similar levels of CO (Jordan et al., 2004). The significant difference observed in forage:concentrate (P < 0.001) was of a magnitude unlikely to reach biological significance and, therefore, should have no effect on animal performance.
Animal Performance
Although no overall significant difference was observed, the RCO treatment improved ADG and G:F compared with both control and CM treatments in ADG and compared with the control treatment for G:F. This improvement in ADG and G:F can be attributed to the maintenance of DMI, a decrease in CH4 energy loss, and the greater energy content of the diet after the inclusion of CO in the concentrate (DE = 13.9 vs. 13.0 MJ/kg of DM for the control). The CM treatment resulted in a significant decrease in ADCG compared with both the control and RCO treatments. The lower dressing percentage recorded when feeding CM (512 g/kg), which has been previously observed (Mulligan et al., 2001), might have contributed to this effect of ADCG; dressing percentage was numerically lowest for the CM treatment. When low digestibility by-products were fed to steers on high-concentrate diets, higher gut fills also have been recorded (Moloney and O’Kiely, 1995), which might explain the observed increase in live weight measures with a parallel decrease in carcass measures.
Digestibility
Decreases in digestibility have been recorded after the addition of CO to the diet (Sutton et al., 1983; Dong et al., 1997); however, we observed a significant effect on digestibility only for the CM treatment. Although this finding contrasts with the literature, it agrees with previous work carried out at this institute (Jordan et al., 2004). Jordan et al. (2004) reported a linear decrease in digestibility in response to increasing levels of CO; however, no significant effect on digestibility was observed up to and including 250 g of CO/d (2.7% DMI), which was replicated in the current experiment for the RCO treatment (2.7% DMI). The observed decrease in digestibility of the DM, OM, CP, and GE fractions of the CM treatment can be attributed to the lower proportion of barley in this treatment (11%) compared with control (37%) and RCO (36%) treatments. These decreases in digestibility agree with those previously recorded for copra meal (Woods et al., 1999), and decreased digestibility may account for some of the poorer carcass growth observed in the CM treatment.
Methane Output and Ruminal Population
The decreases observed in CH4 output agree with those previously reported (Dohme et al., 1999; Lovett et al., 2003; Jordan et al., 2004). The reductions observed in CH4 output (L/d, L/kg of DMI, or percentage of GEI) using RCO are of a similar magnitude with those previously measured at our institute. When CM was added to the diet, the decreases in CH4 for the same measures were numerically smaller, which may be attributed to the CO present in the CM being less available in the rumen. This idea is supported by previous literature, in which oilseeds were fed as a means of partially protecting lipids in the rumen (Machmuller et al., 2000). A decrease in NDF digestion (Dohme et al., 1999) and a decrease in protozoa numbers (Lovett et al., 2003; Machmüller et al., 2003) have been identified as explanations for the reduction in CH4 emissions after the inclusion of CO in the diet. We observed no decrease in NDF digestibility across all treatments. Thus, the decreased CH4 output can be attributed to the decrease in protozoa numbers on both the RCO and CM treatments. Ruminal ciliate protozoa rely on an H2-producing fermentation process that is inhibited by a high concentration of H2. A symbiotic relationship with ruminal methanogens (Finlay et al., 1994) has been established to allow an interspecies H2 transfer, thereby lowering the concentration of H2 for the ciliate protozoa. Therefore, less H2 is available for the formation of CH4 after defaunation, and there is a decrease in symbiotic methanogen numbers; however, a corresponding increase in free-living methanogens has been reported (Sharp et al., 1998). The observed decrease in total ruminal VFA molar concentration also may explain some of the decrease in CH4. A decline in ruminal VFA molar concentration is most likely the result of decreased ruminal VFA production, which has been linked with lower ruminal CH4 output because of the decreased availability of H2 in the rumen (Dohme et al., 1999). Although not measured in this experiment, a direct toxic effect of CO on methanogens has been reported (Dohme et al., 1999; Machmüller et al., 2003), which would be expected to contribute to the decrease in CH4 output. The improvements in animal performance observed in terms of ADG compared with the control treatment resulted in both the RCO and CM treatments lowering CH4/kg of ADG. Nonetheless, the poor carcass growth for the CM treatment resulted in only the RCO treatment producing a significant decrease in CH4 output in terms of ADCG. Given that improved animal performance has been reported as one strategy to decrease CH4 (McCrabb et al., 1998), the lower carcass performance observed for the CM treatment might have implications for overall CH4 emissions. The animal performance data indicated that finishing animals on the CM treatment would require a longer time to reach a common carcass weight and would lessen the effects on total CH4 emissions.
Fatty Acid Profile of Muscle Produced
Meat is seen as one of the primary sources of fat, especially saturated fat, in the diet and has been implicated in the occurrence of some diseases of the developed world (e.g., coronary heart disease). Many health organizations have recommended a decrease in the intake of SFA to lower the risk of coronary heart disease (Grundy, 1994). The inclusion of RCO or CM in the diet led to a significant increase in the concentrations of the SFA lauric and myristic in the LM. Average serum cholesterol concentrations are strongly influenced by the inclusion of these fatty acids in the human diet (Kromhout et al., 1995). Kromhout et al. (1995) also reported a strong positive association between death rates from coronary heart disease and average intake of the 4 main SFA, lauric, myristic, palmitic, and stearic acids. Data on the hypercholesterolemic effects of myristic are conflicting, but based on the available studies, it must be regarded at least as hypercholesterolemic as palmitic acid (Grundy, 1994). Grundy (1994) noted, however, that given the low proportions of myristic acid in most diets, its practical importance as a cholesterol-raising fatty acid is much lower than that of palmitic acid. Lauric acid also has been shown to raise LDL cholesterol but only by a factor of 75% compared with palmitic acid (Grundy, 1994). It should be noted that the inclusion of CO in the diet had no significant effect on the palmitic acid concentration. Although the literature suggests that the inclusion of CO in the diet may be detrimental to human health, the increases in lauric and myristic observed in the current experiment were from a low base level. The concentrations of lauric and myristic observed for the RCO and CM treatments were marginally above those recorded in a survey of 50 retail samples of beef in UK supermarkets and below those recorded for lamb (Enser et al., 1996). Denke (1994) suggested that lean beef is no more hypercholesterolemic than chicken or fish and thus need not be eliminated from a cholesterol-lowering diet. Therfore, it can be assumed that the inclusion of CO in the diet at 250 g/d will have no noticeable detrimental effect on the fatty acid profile of lean beef in terms of its LDL cholesterol-enhancing properties.
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IMPLICATIONS
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Including 250 g/d of refined coconut oil in the diet decreased (18%) CH4 output, maintained intake, and improved animal performance. The resulting shift in the fatty acid profile of the beef was of a magnitude unlikely to have health implications for humans. The increase in performance enhances the CH4 reduction because of a shorter finishing time. This shorter finishing time and improved performance may balance the cost of including refined coconut oil in the diet, depending on constantly changing market prices. Copra meal gives comparable decreases in CH4 to refined coconut oil; however, decreased performance with copra meal would result in an extended finishing time, which has implications for CH4 emissions and production economics because of a longer animal lifetime. Further research is required to determine the effects of coconut oil on the ruminal bacterial population and the potential of other oils to decrease CH4 emissions and also to consider the effect on the resulting fatty acid profile of meat.
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Footnotes
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1 This work was funded by the Environmental RTDI Programme 2000–2006, financed by the Irish Government under the National Development Plan, and administered on behalf of the Dep. of the Environment and Local Government by the Environmental Protection Agency. The provision of an IRSCET post-graduate scholarship also is acknowledged. 
3 Dep. Food Sci., Univ. College Dublin, Belfield, Dublin 4, Ireland.
2 Corresponding author: edward.jordan{at}ucd.ie
Received for publication March 9, 2005.
Accepted for publication August 15, 2005.
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Abstract
INTRODUCTION
