Various levels of copra meal supplementation with β-Mannanase on growth performance, blood profile, nutrient digestibility, pork quality and economical analysis in growing-finishing pigs

A total of 100 crossbred pigs ([Yorkshire × Landrace] × Duroc) with an average body weight of 31.02 ± 2.04 kg were used for 12 week feeding trial in experimental farm of Seoul National University. Pigs were grouped by body weight and sex, and assigned to five treatments according to RCB design. Each treatment had 5 replicates with 4 pigs per pen. Pigs were housed in growing pen (1.40 × 2.50 m²) and finishing pen (1.70 × 2.50 m²) that were easy to supply feed and water by ad libitum and control room temperature and ventilation. Body weight and feed intake were recorded at every 3 weeks to calculate the average daily gain (ADG), average daily feed intake (ADFI) and gain to feed ratio (G:F ratio) of the pigs.

The treatments included 1) Control: 5% of copra meal + 0.1% of β-mannanase (800 IU), 2) CM10: 10% of copra meal + 0.1% of β-mannanase (800 IU), 3) CM15: 15% of copra meal + 0.1% of β-mannanase (800 IU), 4) CM20: 20% of copra meal + 0.1% of β-mannanase (800 IU), 5) CM25: 25% of copra meal + 0.1% of β-mannanase (800 IU). Mainly corn, SBM and wheat bran were replaced by the CM. The diets were formulated to contain 3,265 kcal of ME/kg for the all phases. Experimental diets were mixed mainly with corn and SBM and nutrients of experimental diets were met or exceeded the requirement of NRC [13]. β-mannanase (patent, 10-0477456-0000; CTCbio® Inc., Seoul, Republic of Korea) in dry form was supplemented in basal diet.

The feeding program was composed with four phases; growing I (week 1–3), growing II (week 4–6), finishing I (week 7–9) and finishing II (week 10–12) respectively. Formula and chemical composition of diet were presented in Tables 1, 2, 3 and 4. Expeller CM from Philippines was used in this experiment, and the analyzed composition was shown in Table 5.

Blood samples were collected from anterior vena cava of 6 pigs per each treatment at 0, 3, 6, 9 and 12 week for analyzing concentration of glucose and blood urea nitrogen (BUN) in serum. Collected blood samples were centrifuged for 15 min at 3,000 rpm in 4 °C (Eppendorf centrifuge 5810R, Germany). Serum was carefully removed to microtubes and stored at −20 °C until analysis. Glucose and BUN concentration were analyzed using a blood analyzer (Ciba-Corning model, Express Plus, Ciba Corning Diagnostics Co.).

A total of 15 crossbred barrows, average body weight 34.73 ± 0.24 kg, were allocated to the each five treatment with three replicates in metabolic cages in a completely randomized design (CRD). The experimental diets were provided twice daily by 2.0% of body weight (on 1% of in each feeding) at 7:00 and 19:00, and water was provided by ad libitum. After 5 days of adaptation period, feces and urine were collected for further 5 days by the method of Hong et al. [14]. The feces and urine collected from each pig during these 5 days were stored at −20 °C until they were analyzed. After collecting period, the excreta were dried in an air-forced drying oven at 60 °C for 72 h and ground to 2 mm of diameter by a Wiley mill for chemical analysis [15]. Feed, feces and urine were chemically analyzed by the method of AOAC [15].

At the end of experiment, four pigs from each treatment group were selected and slaughtered at average 117.8 ± 1.06 kg for the carcass analysis. Pork samples were collected from nearby 10th rib on right side of carcass. Because of chilling procedure, 30 min after slaughter was regarded as initial time. The pH and pork color were measured at 0, 3, 6, 9, 12 and 24 h, respectively. The pH was measured using a pH meter (Bechman Coulter Φ 500 Series, USA) and pork color was determined by CIE color L*, a*, and b* values using a CR300 (Minolta Camera Co., Japan). Chemical analysis of pork samples were conducted by the method of AOAC [15].

Water holding capacity of pork was measured by centrifuge method (Ryoichi et al., 1993). Longissimus muscles were ground and sampled in filter tube, then heated in water bath at 80 °C for 20 min and centrifuged for 10 min at 2,000 rpm and 4 °C (Eppendorf centrifuge 5810R, Germany). After that, to calculate the cooking loss, longissimus muscles were packed with polyethylene bag and heated in water bath until core temperature reached 70 °C and weighed before and after cooking. After heated, samples were cored (0.5 in. in diameter) parallel to muscle fiber and the cores were used to measure the shear force using a salter (Warner Bratzler Shear, USA). Shear force, cooking loss and water holding capacity of pork were analyzed by National Institute of Animal Science.

As the experimental pigs were reared in the same environmental condition, economical efficiency was calculated by considering only the feed cost. The feed cost per body weight gain (won/kg) was calculated using total feed intake and feed price. The days to reaching market weight (115 kg) was estimated from the body weight at the end of feeding trial and ADG of 9–12 week.

All data were analyzed using the general linear model (GLM) procedure of SAS [16]. RCB design was adopted in feeding trial and pen was the experimental block unit. CRD was adopted in digestibility trial, blood and carcass analysis and individual pig was the experimental unit. Statistical differences were considered significant at the level of P < 0.05 and highly significant at the level of P < 0.01, with a trend between P ≥ 0.05 and P ≤ 0.10 for Control group and CM treated group. Statistical differences were considered to be linear or quadratic at the level of P < 0.05 and highly linear or quadratic at the level of P < 0.01 for CM treated group.

The effect of CM supplementation with β-mannanase on growth performance during 12 weeks was presented in Table 6. In growing phase, the level of CM did not affect the body weight (BW), ADG and ADFI. However, G:F ratio tended to increase when CM level was increased in growing I phase (linear, P = 0.05). In finishing I phase, tendency of quadratic response was observed on CM20 treatment (quadratic, P = 0.06). During finishing II period, the ADG and ADFI tended to decrease when CM level increased (linear, P = 0.08, P = 0.06, respectively). Also, a linear response on the ADG (linear, P = 0.02) and tendency of decreasing in G:F ratio (linear, P = 0.08) were observed as increasing level of CM in diet during the whole finishing period.

Nunes and Malmlof [17] reported that high level of mannan in swine diet interfered with the insulin and IGF-I secretion and affected negatively on growth performance. But, in current experiment, CM25 showed similar growth performance to CM5 without statistical difference in growing period and the whole experimental period. This can be explained by result of Khanongnuch et al. [18] that exogenous mannanase which degraded mannan in CM was sufficient even in CM25, so that they had enough transit time to digest ingesta including CM. Petty et al. [19] also reported adding β-mannanase to diets had a positive influence on pigs and improved the G:F ratio (P < 0.01).

Similarly, supplementation of mannan degrading enzyme to growing-finishing pig diet has increased G:F ratio and lean gain [20, 21]. However, in finishing II phase and during whole finishing period, ADFI was decreased in agreement with Jaworski et al. [22] who demonstrated that supplementation of diet with CM lowered feed intake. Also, reduction of ADFI by CM inclusion may affect the ADG and G:F ratio in finishing period [22]. It is considered to be due to rancidity after prolonged storage [23] or the lower density and more swelling (high crude fiber) of CM [18].

This result demonstrated that palatability was affected by level of 20% CM in finishing phase. However, ADFI in growing phase was not affected, and there was an improvement of feed efficiency by increasing level of CM in early growing phase. These observations were supported by the result of former researchers [22, 23].

Consequently, during the whole experimental period, there were no significant differences in growth performance when fed up to 25% of CM with 0.10% of β-mannanase.

Blood profiles parameters during feeding trial were presented in Figs. 1, 2 and 3. During the whole experimental period, there was no significant difference in glucose concentration when pigs were fed diet with increasing level of CM. Mannans and galactomannans in CM might reduce the absorption of glucose and decrease the production of insulin [17, 24]. But, Kim et al. [25], demonstrated that the concentration of blood glucose in pigs fed diet with β-mannanase was greater than pigs fed diet without β-mannanase (P = 0.03). The result of this study was considered as due to the reduced negative effects of anti-nutritional factor by added dietary β-mannanase [26]. At 6 week, linear increasing of BUN was observed as CM supplementation level increased (linear, P = 0.02). The BUN has been known to a good indicator for evaluation in protein quality, protein intake [27] and nitrogen retention [28] by pigs. Münchow and Bergner [29] reported that there was a highly negative correlation between the biological value of feed and BUN content. Increase of BUN concentration indicated that excessive amino acids are inefficiently metabolized and circulated in the blood before excretion [30, 31]. Although a linear response by CM supplementation level was observed at 6 week, the BUN value of all treatments were in normal range (10.0 – 30.0 mg/dL). Consequently, CM inclusion with β-mannanase did not negatively affect the blood glucose and BUN.

Fig. 1. Effect of dietary levels of copra meal with β-mannanase on blood glucose in growing-finishing pigs

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Fig. 2. Effect of dietary levels of copra meal with β-mannanase on blood urea nitrogen (BUN) in growing-finishing pig

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Fig. 3. Effect of dietary levels of copra meal with β-mannanase on pH at slaughtering

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The effect of CM supplementation with β-mannanase on nutrient digestibility was presented in Table 7. The digestibility of crude protein in growing pigs was linearly declined with increasing inclusion of CM (linear, P = 0.02), and the tendency of decrease was found when over 15% of CM was supplemented (P = 0.07). The digestibility of dry matter, crude fat, and crude ash showed no significant difference among treatments. Nitrogen retention tended to be decreased (linear, P = 0.08) as CM level increased in pig diet, leading to the tendency of increasing in fecal nitrogen (linear, P = 0.05).

During heating process of CM, the Maillard reaction occurred between mannose and amino group which alleviated total nutritional value of CM [32]. Also, Kim et al. [3] demonstrated that lowered digestibility was observed when pigs were fed CM because of the higher crude fiber level in CM than in SBM. The negative effect of fiber might be from the effect of fiber on transit time, water-binding capacity of fiber, mechanical erosion and absorption of nutrients on the fiber [33].

Consequently, increasing level of CM caused lower crude protein (CP) digestibility by higher fiber which was the reason of increased fecal nitrogen and reduced nitrogen retention.

The effect of CM supplementation with β-mannanase on pH of pork was presented in Fig. 3. In this study, increasing level of CM did not affect the pH levels change and the pH value at 0, 24 h.

The pH change of pork is a very important factor that determines the quality of pork and has an influence on freshness, tenderness, meat color and texture [34].

It is also an important factor for the storage [35]. In fact, the initial pH is regarded as an indication of PSE (pale, soft and exudative) pork and the final pH is acknowledged as an estimation of DFD (dark, firm and dry). In general, pH decline is accelerated as time goes by, and ultimate pH is reduced because of creation of lactic acid from glycogen [36–38]. In this study, since the CM level in diet did not affect pH of pork, it is considered that inclusion of CM did not have adverse effect on pork quality which was correlated with pH.

The results of pork color were presented in Table 8. There was no significant difference among treatments in L*, a* and b* value at 0, 3, 6, 9, 12, 24 h after slaughter. In pork color, decreasing in redness and increasing in yellowness had a negative influence on the freshness of pork [39]. But, there was no change in redness or yellowness by CM level in diet. These findings were in accordance with those of Hong [40], who had demonstrated that a* and b* values were not affected by CM inclusion level when 0.10% of β-mannanase supplemented.

The effects of on the carcass characteristics of growing-finishing pigs fed with increasing level of CM with β-mannanase were noted in Table 9. In current study, the level of CM did not affect the cooking loss, shear force, water holding capacity (WHC) and proximate analysis of the pork after slaughter. The result of fat content contrasted with those of Creswell and Brooks [2] who demonstrated that the relationship between dietary CM and fat composition of carcass and CM additions resulted in increased fatty acids in the backfat. When crude fat content increases in longissimus muscles, WHC is increased and shear force and cooking loss are decreased [41].

The effects of dietary CM levels with 0.10% of β-mannanase on feed cost were presented in Table 10. There was a tendency in feed cost per weight gain in growing I phase (linear, P = 0.06), growing II phase (linear, P = 0.09). During overall period, there was decreasing in (linear, P = 0.02) feed cost per weight gain according to effect of dietary CM levels increasing, either. Also, total feed cost per pig was reduced by dietary CM levels in growing I phase (linear, P = 0.03) and during overall period (linear, P = 0.04). Decreasing feed cost of high content of CM was mainly caused by the replacement of SBM. There was no significant response in days to market weight. Total feed cost in whole days to market weight was reduced up to 6.56% when fed diets with increasing level of CM. Also, feed cost (won/kg) reduction of 1.01 won was observed when each 1% CM inclusion level increased.