Effect of dietary soyabean hulls and metal-amino acid chelated mineral supplementation on growth performance , nutrient digestibility and noxious gas emission in growing pigs *

A 2×2 factorial design Experiment 1 was conducted in order to characterize the effects of soyabean hulls (control or soyabean hulls diet) and metal-amino acid chelated minerals (MAC) (sulphate or MAC) on growth performance and nutrient digestibility in growing pigs. Forty eight pigs with the initial body weight (BW) 18.0±1.1 kg were assigned on the basis of weight and sex to one of four treatments (2 pigs/pen, 6 replication pens/treatment, 6 barrows and 6 gilts/treatment). Throughout the experimental period, growth performance was not shown to be affected by dietary treatments. The coeffi cients of the total tract apparent digestibility of dry matter (DM) and nitrogen (N) remained unaffected by soyabean hulls diets or MAC supplementation. In Experiment 2, four barrows were used in a 4×4 Latin square design, to determine the effects of soyabean hulls and mineral types on emission of faeces and slurry noxious gas, including ammonia (NH3), hydrogen sulphide (H2S) and mercaptans (R.SH), in growing pigs. Faeces and urine grab samples were collected, and the faeces (300 g) and slurry (faeces + urine = 150 + 150 g) were mixed, stored, and fermented for 5 d in order to evaluate noxious gas emission. Pigs fed diets with soyabean hulls tended to have lower NH3 emission from faeces (P=0.09) than those fed the control diet, but NH3 emission from the slurry was not affected by soyabean hulls diet (P=0.12). No signifi cant effects on the faeces or slurry NH3 emission were exerted in MAC supplementation treatment. A signifi cant level of interaction between soyabean hulls and MAC was observed both in the faeces and slurry NH3 emission (P=0.05, P=0.01). Pigs fed diets with soyabean hulls tend to exhibit lower H2S emission from the slurry (P=0.07), but signifi cantly lower levels of H2S emission both from faeces and slurry (P=0.004, P=0.02) was observed when pigs were fed on MAC diets. The emission of R.SH from faeces signifi cantly decreased (P=0.02) in MAC supplementation treatments, but not from slurry, and no soyabean hulls effects or interaction were observed in relation to R.SH emission. * Supported by the Rural Development Administration of Korea 1 Corresponding author: e-mail: inhokim@dankook.ac.kr Journal of Animal and Feed Sciences, 17, 2008, 171–181 172 SOYABEAN HULLS AND MAC IN GROWING PIGS We conclude that the interaction between dietary soyabean hulls and MAC may have an effect on noxious gas emission. The emission of NH3 from pig faeces could be substantially reduced by diets enriched with soyabean hulls and emission of H2S both from pig faeces and slurry could be reduced by MAC supplementation.


INTRODUCTION
A great deal of concern in recent years has focused on potential environmental hazards and pollution.Emission of noxious gases from pig facilities is one of the principal sources of environmental pollution in pork production, and several kinds of odours have been implicated, including NH 3 , H 2 S, R.SH, and volatile organic compounds (Schiffman, 1998).With increasing pressure to sustain and improve the environment, many producers and researchers are currently looking for methods to minimize the environmental impacts of meat production.In the past, a lot of researches have shown that the addition of non-starch polysaccharides (NSP) exerts a positive impact on slurry odour, particularly the production of NH 3 , without hindering growth performance (DeCam et al., 2001).Ferket et al. (2002) reviewed the nutritional strategies for the reduction of negative emission from nonruminants.They suggested that the noxious gas emission from animals is ultimately associated with nutrient utilization and the intestinal microbiota ecosystem.The addition of NSP source supplementation in the diet was proposed as a method to improve the intestinal microbiota ecosystem and to alter excreta pH, thereby reducing pollution.
Hydrogen sulphide and methyl mercaptan are frequently identifi ed as pig waste constituents and are quantitatively the most important S-containing volatile constituents (Spoelstra, 1980).The reduction of inorganic sulphate to sulphide occurs to a limited extent in nonruminants (Kline et al., 1971).Therefore, it seems that the majority of the production of hydrogen sulphide and other volatile sulphurcontaining gases occurs as the consequence of microbial fermentation during slurry storage.Replacement with non-sulphate minerals has been suggested as another feasible way by which the production of animal sulphur-based gases can be reduced.Therefore, we hypothesized that a high NSP content soyabean hulls diet coupled with non-sulphate minerals (metal-amino acid chelated mineral) could reduce both NH 3 and sulphur-based gas production from pig faeces and slurry.
The present study was conducted in order to assess the effects of soyabean hulls diet and MAC supplementation on growth performance, DM and N digestibility, and faecal and slurry noxious gas emission in growing pigs.

MATERIAL AND METHODS
The experimental protocols were approved by the Animal Care and Use Committee of Dankook University.

Experiment 1. Growth performance experiment
Experimental design, animals, housing and diets.A total of 48 pigs (initially 18.0±1.1 kg of BW) were used in a 5-week experiment to evaluate the effect of feeding soyabean hulls and MAC on growth performance and nutrient digestibility in growing pigs.The pigs were allotted to treatments by weight with sex ratios equalized in accordance with a completely randomized design, with 2 pigs per pen and 6 replications per treatment.All pigs were housed in environmentallycontrolled rooms with plastic, slatted fl oors.Each of the pens was equipped with a one-sided self-feeder and a nipple waterer to allow ad libitum access to feed and water throughout all the experimental periods.The target room temperature and humidity were maintained at 25°C and 60%, respectively.The dietary treatments included: 1. basal diet + sulphate minerals, 2. basal diet + metal-amino acid chelated minerals, 3. soyabean hulls diet + sulphate minerals and 4. soyabean hulls diet + metal-amino acid chelated minerals.All diets were formulated to meet or exceed the NRC (1998) recommendations for all nutrients (Table 1) and were fed in meal form.
Sampling and measurements.Individual pig weights were measured at the beginning and end (5 weeks) of the experimental period; feed consumption was also recorded in terms of gain/feed on a pen basis.Growth performance, including average daily gain (ADG), average daily feed intake (ADFI) and gain/feed, was determined at the conclusion of the feeding trial.
The coeffi cients of total tract apparent digestibility for DM and N were determined at the end of 5 weeks.Chromic oxide (Cr 2 O 3 ) was used as an indigestible marker.Pigs were fed on 0.2% chromic oxide-containing diets for 7 days prior to the collection day, and fresh faecal grab samples were acquired from each pen at d 35.All of the faecal samples, as well as the feed samples, were stored in a refrigerator at -20°C until they could be further analysed.Prior to chemical analysis, the faecal samples were thawed and dried for 72 h at 70°C and subsequently ground in order to pass them through a 1-mm screen.All of the feed and faecal samples were analysed for DM and N according to AOAC procedures (1995).Chromium was analysed via UV absorption spectrophotometry (Shimadzu, UV-1201, Japan) according to the methods described by Williams et al. (1962).Nitrogen levels were assessed using a Kjeltec 2300 Analyzer (Foss Tecator AB, Hoeganaes, Sweden).diets (control or soyabean hulls diet) were supplemented with: sulphates (10, 90, 100 and 12.5 mg/kg of supplemental Cu, Fe, Zn and Mn, respectively, from sulphate forms); or chelated (6, 25, 38 and 10 mg/kg of supplemental Cu, Fe, Zn and Mn, respectively, from metal-amino acid chelated forms); both in sulphate and chelate minerals 0.3 mg Se (as NaSeO 3 ) and 0.2 mg I (as KI) were provided per kg of complete diet 3 non-starch polysaccharides (NSP) was calculated as organic matter -(crude protein + crude fat + starch + sugar)

Experiment 2. Metabolism experiment
Experimental design, animals, housing and diets.Four barrows (initially 25.6±0.1 kg of BW) were used in a 4×4 Latin square design experiment to assess the effects of soyabean hulls and MAC on noxious gas emission from faeces and slurry.The pigs were housed in individual elevated solid-sided stainless steel metabolism cages (1.6×0.8 m 2 ) equipped with plastic slatted fl oors, stainless steel feeders, and low-pressure, automatic water nipple drinkers.Temperature was maintained at approximately 25°C with thermostatically controlled heaters and exhaust fans.
Sampling and measurements.During each experimental period, pigs were fed experimental diets for the fi rst 7 d, thereafter the collection of urine and faeces was initiated at 08.00 on d 8. Urine and faeces samples were collected for 24 h and stored immediately after collection at -20°C.There is a 6-d (from d 9 to d 14) convalescent period before introducing new experimental diets to pigs.During this convalescent period, all the pigs were fed control diets.At the conclusion of the experiment, urine and faeces samples were thawed, pooled within pig and period, and well-mixed.According to the method of Cho et al. (2008), subsamples of faeces (300 g) and slurry (150 g faeces and 150 g of urine were mixed well, 1:1, wt/wt; wet weight basis) were taken and stored in 2.6 l plastic boxes in duplicate.Each box had a small hole in the middle of one side wall, which was sealed with adhesive plaster.The samples were permitted to ferment for 5 d at room temperature (25°C).After the fermentation period, a Gastec (model GV-100) gas sampling pump was utilized for gas detection (Gastec Corp., Gastec detector tube No. 3M and 3La for NH 3 ; No. 4LL and 4LK for H 2 S; No. 70 and 70L for R.SH, Gastec Corp, detector tube, Japan).Prior to the measurements, slurry samples were shaken manually for approximately 30 s in order to disrupt any crust formation on the surface of the slurry sample and to homogenize them.The adhesive plasters were punctured, and 100 ml of headspace air was sampled approximately 2.0 cm above the faeces or slurry surface.The gas emission of the sample within pig and period was averaged by measurements of two duplicate boxes.

Statistical analyses
In Experiment 1, the data were analysed as a 2×2 factorial using the General Linear Model Procedure of the SAS (1996).The model utilized included the effects of soyabean hulls and metal-amino acid chelated mineral, as well as the associated two-way interaction.The individual pen served as the unit.In Experiment 2, the data were analysed as 4×4 Latin square design using the General Linear Model Procedure of the SAS (1996).The variability of all the data was expressed as the standard error (SE) and a probability level of P<0.05 was considered to be statistically signifi cant, whereas P<0.10 was considered to represent a tendency.

RESULTS
Table 2 provides the results of supplemental soyabean hulls and MAC on growth performance in growing pigs.No soyabean hulls or MAC effects, as well as interaction between soyabean hulls and MAC were found on ADG, ADFI and gain/feed in our data.Apparent digestibility coeffi cients of supplemented diets are given in Table 3.We noted no signifi cant soyabean hulls or MAC effects, as well as their interaction on DM and N digestibilities.2 The effects of dietary soyabean hulls and MAC supplementation on faecal and slurry noxious gas emission are shown in Table 4. Pigs fed on soyabean hulls diets tend to evidence lower faecal NH 3 emission (P=0.09) as compared to those fed on control diets, however, slurry NH 3 emission was unaffected by soyabean hulls diets (P=0.12).Metal-amino acid chelated mineral supplementation had no effect on NH 3 emission from faeces and slurry.A signifi cant level of interaction between soyabean hulls and MAC was observed in the NH 3 emission from both the faeces and slurry (P=0.05,P=0.01).Pigs fed on soyabean hulls diets tend to exhibit lower levels of H 2 S emission in slurry (P=0.07),but evidenced lower levels of H 2 S emission from both faeces and slurry (P=0.004,P=0.02) when pigs were fed on a MAC-supplemented diet.The observed interaction between soyabean hulls and MAC was not observed in the H 2 S emission.Metal-amino acid chelated mineral supplementation treatments resulted in a signifi cant reduction (P=0.02) of mercaptans (R.SH) emission from faeces but did not from slurry, and no soyabean hulls effects as well as their interaction were observed in relation to R.SH emission.2 3 faeces 300 g kept in sealed box fermented 5 d, using Gastec detector measure noxious gas emission 4 faeces 150 g and urine 150 g kept in sealed box fermented 5 d, using Gastec detector measure noxious gas emission 5 soyabean hulls effect, P<0.10 6 MAC effect, P<0.05 7 soyabean hulls × MAC interaction, P<0.05 DISCUSSION Previous reports regarding different NSP supplementation methods in pig diets have presented a variety of results.Radar matrix (1996) and Van Oeckel (1998) detected no effects on pig performance when 5 and 15% soyabean hulls as the primary NSP resource were added into the diets of growing and fi nishing pigs, respectively.Our results verifi ed their fi ndings.On the contrary, studies conducted by DeCamp et al. (2001) indicated that the addition of 10% soyabean hulls (the main NSP resource) with the addition of animal fat in the diets of fi nishing pigs could improve ADG and gain/feed characteristics.They explained that this might be attributable to the elevated fat in the soyabean hulls diet, thereby possibly augmenting growth for those pigs fed on diets containing soyabean hulls.Varel and Yen (1997) reviewed that the fermentation of NSP and dietary fi bre take place in the caecum and colon of monogastric animals, and the produced VFA reduced the pH of the slurry.The effects of MAC on growth performance were assessed by a host of researchers.Creech et al. (2004) previously reported that trace mineral sources exerted no effects on performance during the growing or gilt development phase.Coffey et al. (1994) and Zhou et al. (1994) previously reported that additions of Cu from copper-lysine complexes resulted in improved pig performance as compared with copper sulphate.Other researchers, however, have noted no differences in growth-promoting activity between the two Cu sources (van Heugten and Coffey, 1992).
Both DM and N digestibilities were not affected in soyabean hulls treatments as compared to control treatments in the current study.However, in a previous study conducted by O'Connell et al. (2005), it was reported that the DM and N digestibilities were apparently reduced in their soyabean hulls treatment as compared to the control treatment.Another study conducted by Dilger et al. (2004) also reported that the apparent ileal digestibility of DM decreased in a linear fashion with increasing levels of added soyabean hulls (3 to 9%), whereas N digestibility remained unaffected in 35-kg barrows.These different results might be attributable to two possible factors.Firstly, slowed gastrointestinal emptying may occur in response to dietary fi bre content and types as well as viscous material (Guérin et al., 2001).Secondly, gastrointestinal pH may be increased as the result of the buffering capacity of NSP, with the indirect result of reduction in gastrin secretion in response to the more alkaline environment (Dilger et al., 2004).Metalamino acid chelated mineral has been shown to evidence better absorption, which has been reported by many researchers to enhance the effi ciency of its use (Yu et al., 2000;Guo et al., 2001).However, our data evidenced no improvements in the MAC treatments, the different supplemented level and mineral type from that utilized in other experiments may be a reasonable explanation for the differences observed in the current study.
Supplementing pig diets with high NSP sources coupled with the addition of amino acids has been suggested as a way to activate the intestinal microbiota ecosystem, and also alters excreta pH, thereby reducing the emission of NH 3 from the faeces.Our data indicated that NH 3 emission from both the faeces and slurry were reduced signifi cantly as the result of the addition of soyabean hulls (primary NSP resources).This result is consistent with the fi ndings of previous research.Mroz et al. (2000) determined that the addition of soyabean hulls (25%) and (or) sugar beet pulp (25%) reduced the ratio of urinary:faecal N, and thereby the emission of NH 3 from the slurry in fi nishing pigs.Hansen et al. (2007) observed 30% reduced NH 3 emission in 15% inulin (a known NSP resource) addition treatment in fi nishing pigs.The possible reasons for the reduction in NH 3 emission may be attributable to the benefi cial effects of NSP on the bifi dobacteria and lactobacilli populations present in the large intestine, as the inclusion of NSP in the diet promotes carbohydrate-fermenting bacteria (O'Connell et al., 2005).In the large intestine, these fi bre-degrading bacteria utilize NH 3 as a substrate for microbial protein synthesis and are subsequently excreted in the faeces.Such effects shift nitrogen excretion from volatile NH 3 in the urine to bacterial nitrogen in the faeces.This is desirable, as it limits the capacity for rapid NH 3 volatilization (Nahm, 2003).The interaction between soyabean hulls and MAC may be attributable to the fact that MAC exerts some additional effects on the activation of the intestinal bacteria ecosystem.Our current experiment was not designed to determine the changes of intestinal bacteria population.Further work should be conducted in order to investigate the clear relationship between soyabean hulls and dietary MAC supplementation.
Hydrogen sulphide and R.SH are crucial sulphur-containing volatile constituents (Spoelstra, 1980).Variations in sulpuric odorous compound concentrations in animal faeces are principally attributable to the differences in the sulphur composition of diets fed to pigs, and the metabolism of sulphur-containing amino acids (methionine, cystine and cysteine), which generate sulphuric odorous compounds including H 2 S and R.SH (Reviere et al., 1974;Kiene and Hines, 1995).Our data indicated that faecal H 2 S emission was increased as the result of soyabean hulls supplementation.Similarly, in our previous study, we detected a linear increase in H 2 S emission when increasing the level of soyabean hulls addition in the diets of growing pigs (unpublished).High dietary NSP levels resulted in a reduction in CP levels and enhanced microbial activities within the gut of the animal and in the slurry stores, which might be responsible for the higher observed slurry VFA concentrations and lower pH.Low slurry pH can inhibit H 2 S emission.Our data are inconsistent with the fi ndings of DeCamp et al. (2001), who reported that H 2 S emission in room air samples was decreased signifi cantly when fi nishing pigs were fed on a diet containing 10% soyabean hulls as compared with those fed on a control diet.The difference between our results and those of others may be attributable to the different cysteine and cystine levels in the diets.Metal-amino acid chelate mineral treatments resulted in lower sulphur compositions than were observed with sulphate mineral diets, due to the lack of SO 4 2-.Again, sulphuric odorous compound concentrations in animal faeces were found to be due principally to the differences in the level of sulphuric compositions in the diets fed to the pigs.Therefore, lower H 2 S emission in both faeces and slurry were obtained in the current experiment.

CONCLUSIONS
We conclude that the interaction between dietary soyabean hulls and MAC performs a function in noxious gas emission.Ammonia emission from pig faeces can be substantially reduced via the administration of a soyabean hulls to diet.Hydrogen sulphide emission from pig faeces and slurry could be reduced by MAC supplementation.The interaction observed in slurry NH 3 emission in the current experiment may be attributed to some additional urinary H 2 S emission lowering effects.The precise mechanisms underlying this interaction require further investigation.

Table 2 .
Effect of experimental treatments on growth performance in pigs 1

Table 3 .
Effect of experimental treatments on total tract apparent digestibility of DM and N in

Table 4 .
Effect of experimental treatments on noxious gas emission in pigs