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Animal Science Journal (2015) 86, 428–434
doi: 10.1111/asj.12314
ORIGINAL ARTICLE The influences of weaning age and weight on carcass traits and meat quality of pigs Kyung Bo KO1,*, Gap-Don KIM2,*, Dong-Geun KANG1, Yeong-Hwa KIM1, Ik-Dong YANG1 and Youn-Chul RYU1 1
Division of Biotechnology, College of Applied Life Sciences, Jeju National University, Jeju and 2Department of Food Science and Biotechnology, Kyungnam University, Changwon, Republic of Korea
ABSTRACT The purpose of this study was to establish the effects of weaning age and weight on pigs, and their interaction with carcass traits and meat quality. A total of 468 piglets were obtained from 57 sows and four boars and grouped by age at weaning (D21, 18–24 days; D28, 25–32 days). Each weaning group was subdivided into three weight groups (L, M and H) according to weaning weight. The D28 group had heavier carcass weight, redness and yellowness, but had lower marbling scores and less drip loss than the D21 group (P < 0.05). The pigs with a light weight at weaning had higher carcass weights and lower yellowness than did pigs with a medium or heavy weight at weaning (P < 0.05). Weaning age was found to have a negative correlation with drip loss, while weaning weight was negatively correlated with carcass weight and drip loss (P < 0.05). We concluded that carcass and meat quality traits in pigs were significantly related to their age and weight at weaning. Therefore, we find that piglet weaning age and weight are no less important than post-weaning growth performance and behavior, with regard to carcass traits and meat quality.
Key words: carcass trait, meat quality, pig, weaning age, weaning weight.
INTRODUCTION The weaning of piglets is accompanied by stressors, including maternal separation, relocation to new housing, introduction into a new social group, and change of diet (van der Meulen et al. 2010). Thus, reduction of feed intake and inhibition of piglet growth rate often occur (McCracken et al. 1995). In the conventional weaning system, the range of weaning age is from 17 days to 21 days; however, piglets are weaned at 12–14 days in the early weaning system (Dantzer & Mormede 1981; Maxwell & Carter 2000). In Europe, weaning before 28 days of age is prohibited (ECCD 2001). Some studies have suggested that a decrease in weaning age could improve feed efficiency and growth rate while lowering the transfer of growth-depressing pathogens to offspring (Patience et al. 2000). However, the early weaning system has disadvantages in wean-to-finish average daily gain (ADG), mortality rate and aggressive behaviors (Main et al. 2004). The other contributing factor to post-weaning growth is the weaning weight of piglets. The growth rate tends to be higher in large pigs than small pigs, and the weaning weight and its variation are influenced by the birth weight and its variation in piglets (McConnell et al. 1987; Allen et al. 2010). In previous © 2014 Japanese Society of Animal Science
studies, the heavy weaning weight for piglets weaned at 28 days was 8.5 kg or over, and pigs with a heavy weaning weight had a higher growth rate between weaning and 20 weeks of age than those with a light weaning weight (Mahan et al. 1998; Lawlor et al. 2002; Magowan et al. 2011). The effects of weaning age and weight on postweaning behavior and growth performance have been well established, but published research on their effects on meat quality is lacking. Therefore, the aim of this study was to compare the meat quality of finishing pigs classified by various ages and weights at weaning and to establish the interaction effect of weaning age and weight on pork quality.
MATERIALS AND METHODS Animals and samples Piglets (n = 468; 252 female and 216 male) were obtained from 57 sows and four boars. The sows and sire line semen Correspondence: Youn-Chul Ryu, Division of Biotechnology, College of Applied Life Sciences, Jeju National University, 66 Jejudaehakro, Jeju 690-701, Republic of Korea. (Email: [email protected]) *These authors contributed equally to this work. Received 30 May 2014; accepted for publication 17 July 2014.
EFFECT OF WEANING AGE AND WEIGHT IN PIG
Table 1
429
Ingredients and nutrient composition of the diets
Item Ingredient composition (%) Corn Soybean meal Wheat bran Wheat Rapeseed meal Molasses Limestone Tricalcium phosphate NaCl Vitamin† Mineral‡ L-Lysine HCl DL-Methionine Antibiotic Analyzed nutrient and energy content Crude protein (%) Lysine (%) Methionine (%) Digestible energy (Mcal/kg)
Starter diet
Grower diet
Finisher diet
49.7 32.6 – 14.2 – 0.5 0.5 1.6 0.1 0.1 0.1 0.2 0.2 0.3
65.3 27.7 – – – 4.0 0.4 1.9 0.3 0.1 0.1 0.1 – 0.1
69.3 15.7 5.7 – 3.0 4.0 1.0 0.8 0.3 0.1 0.1 0.1 – –
19.5 1.2 0.4 3.5
16.0 0.9 0.3 3.4
14.0 0.8 0.2 3.3
†Supplied per kg of diet: 8100 IU of vitamin A, 1200 IU of vitamin D3, 45 IU of vitamin E, 2.25 mg of vitamin K, 1.5 mg of thiamin, 0.6 mg of riboflavin, 2.55 mg of pyridoxine, 0.03 mg of vitamin B12, 19.5 mg of pantothenic acid, 39 mg of niacin, 0.09 mg of biotin, and 0.75 mg of folic acid. ‡Supplied per kg of diet: 102.7 mg of FeSO4, 0.4 mg of CoSO4, 67 mg of CuSO4, 54,2 mg of MnSO4, 69 mg of ZnSO4, 0.5 mg of CaIO3, and 0.3 mg of Na2SeO3.
Table 2 The number of pigs, weaning age and weight in pig groups
Weaning age Weaning weight
21 L
M
28 H
L
M
SEM H
Number of pigs 65 52 59 63 85 144 Weaning age (day) 21.5 21.8 22.0 29.0 28.9 28.3 0.3 Weaning weight (kg) 5.9 7.3 9.0 5.8 7.4 9.2 0.1 Data are means.
used were Jeju black pigs (a native Korean breed). Sows were artificially inseminated with unfrozen semen from four boars. The mean, maximum and minimum of piglets per sow were 8.2, 11 and four, respectively. The mean age and weight at weaning were 26.6 days and 7.3 kg, respectively. All pigs were allocated randomly to wean-to-finish pens (12 pigs per pen) within a block. The feed and pig production program followed the Korean feeding standard for swine (RDA 2007). The composition of diet is presented in Table 1. The piglets were classified into two groups by their weaning age: D21 (18–24 days) and D28 (25–32 days), as shown in Table 2. The pigs from each weaning age group were then sorted into three blocks based on weaning weight: L, M and H. For D21, the weights were 5.9 ± 0.1 kg (L), 7.3 ± 0.1 kg (M) and 9.0 ± 0.3 kg (H). For D28, the weights were 5.8 ± 0.1 kg (L), 7.4 ± 0.1 kg (M) and 9.2 ± 0.1 kg (H). When the penned pigs ranged from 190 days to 210 days, the pigs were slaughtered at a commercial slaughtering house over 3 days: 156 pigs (13 pens) were slaughtered on each day. Immediately after slaughtering, carcass weight and backfat thickness (at the midline of 4th–5th thoracic vertebrae) were measured. National Pork Producers Council (NPPC) marbling score and meat quality traits were analyzed after 24 h chilling in a cold Animal Science Journal (2015) 86, 428–434
room at 5°C. After chilling, Longissimus thoracis muscles from the left sides of each carcass were taken to analyze meat quality traits, including meat color, water-holding capacity and texture properties.
NPPC marbling score Marbling score was assessed by laboratory staff using the NPPC marbling standard (NPPC 2002). The scales were 1 (being devoid of marbling), 2, 3, 4, 5, 6 and 10 (being abundant in marbling).
pH Muscle pH was measured directly on the Longissimus thoracis (7th–8th thoracic vertebrae) muscle using a portable pH meter (PH27-SS; IQ Scientific Instruments Inc., Loveland, CO, USA) at 45 min and 24 h post mortem.
Meat color Meat color was measured with a chromameter (CR-300; Minolta Co., Tokyo, Japan) at 45 min and 24 h post mortem after exposing the surface to the air for 30 min at 4°C. The chromameter was standardized with a white plate (Y = 93.5, x = 0.3132, y = 0.3198).
Water-holding capacity (WHC) To evaluate WHC, filter-paper fluid uptake (FFU), drip loss and cooking loss were measured. Drip loss was determined by suspending muscle standardized for surface area in an inflated plastic bag for 48 h at 4°C (Honikel 1987). For cooking loss, muscle samples were cooked to 70°C internal temperature and cooking loss was expressed as a percentage of the initial sample weight. FFU was measured according to Kauffman et al. (1986). © 2014 Japanese Society of Animal Science
430 G.-D. KIM et al.
Table 3 The effects of weaning age and weight on carcass weight, backfat thickness and NPPC marbling score
Weaning age
21
28
SEM
Weaning weight
L
M
H
L
M
H
Carcass weight (kg) Backfat thickness (mm) NPPC marbling score
78.68 22.64 1.96
74.22 21.61 2.14
73.10 23.80 2.55
81.19 22.92 1.77
78.61 22.39 1.77
77.12 21.53 1.93
1.31 0.97 0.12
Level of significance† wa
ww
**
**
***
**
wa × wg
**P < 0.01; ***P < 0.0001. †wa, weaning age; ww, weaning weight. Data are means. NPPC, National Pork Producers Council.
Texture property analysis (TPA) TPA was performed using a rheometer (Compac-100; Sun scientific Co., Tokyo, Japan) and force-time deformation curves were obtained with a 20 kg load cell applied at a cross-head speed of 2 mm/s. Hardness, cohesiveness, springiness, adhesiveness, gumminess and chewiness were quantified as described previously (Bourne 1978).
Statistical analysis The experiment was designed as a 2 (D21 and D28 weaning ages) × 3 (L, M, and H weaning weights) factorial. Data were analyzed using a general linear model (SAS 2002) testing for effects of weaning age and weight, and their interactions. Pearson correlation coefficients were evaluated to describe the relationship of weaning age and weight with significant (P < 0.05) carcass and meat quality traits, such as carcass weight, NPPC marbling score, meat color at 24 h and drip loss. All data are presented as means (SE).
weight (L group in D21) did not show the significant differences in backfat thickness from the other groups (P > 0.05) (Table 3). Rather, NPPC marbling score was significantly higher in the H group of D21 (P < 0.05) and the D21 group had higher NPPC marbling score than did the D28 group, regardless of weaning weight (P < 0.0001) (Table 3). Correa et al. (2006) reported that pigs with a slower growth rate had a higher lean and lower fat proportion compared to pigs with a faster growth rate, and a negative relationship between growth rate and carcass quality was reported by McGloughlin et al. (1988). However, in the present study, a conflicting result was found. The pigs with a heavy weight at weaning (H groups) showed lower carcass weight than did the other groups. In particular, group H in D21 had the highest growth rate until weaning; however, it showed the slowest growth rate (the lowest carcass weight) and the highest NPPC marbling score.
RESULTS AND DISCUSSION Carcass weight, backfat thickness and NPPC marbling score
Muscle pH and meat color
The carcass weight of the pigs was influenced by weaning age and weight (P < 0.01). The L group in D21 had significantly higher carcass weight than that from the M and H group (P < 0.05) (Table 3). However, in D28, no significant difference was seen among the weaning weight groups (P > 0.05). The D28 pigs also had higher carcass weight than did the D21 pigs (P < 0.01). These results show that light piglets grow faster than medium or heavy piglets, regardless of weaning age, and weaning at 28 days increases the carcass weight of pigs. In the previous reports, piglets weaned at 42 days were better able to adapt to weaning than were younger piglets, as a result of them having a more developed digestive system (Hay et al. 2001; Jarvis et al. 2008). Wean-to-finish growth performance, including ADG, mortality and weight, improved as weaning age increased from 12 days to 21 days (Fangman et al. 1996; Main et al. 2004). In the present study, older piglets at weaning showed higher carcass weight than did younger piglets, but the piglets of L in D28, which had the slowest growth rate until weaning, showed the highest carcass weight. Other studies reported that backfat thickness and intramuscular fat content increased with an increase in carcass weight (Galián et al. 2009; Kim et al. 2013). However, in the present study, the pigs that had higher carcass
The results for muscle pH and meat color are presented in Table 4. The ranges of muscle pH at 45 min and 24 h post mortem were from 6.29 to 6.45 and from 5.62 to 5.70, respectively. No significant effects of weaning age and weight, or their interaction effect, on muscle pH was seen (P > 0.05). Muscle pH is used to determine the glycolytic rate during the post mortem period (Honikel & Fischer 1977). Muscles with fast glycolysis show low pH at 45 min post mortem (i.e. < 5.80) and are accompanied with muscle protein denaturation in relation to low WHC (Joo et al. 1999; Ryu et al. 2005). In the present study, normal pH values (≥ 5.80) at 45 min post mortem were found. The age and weight of piglets at weaning did not affect meat color at 45 min post mortem (P > 0.05), whereas significant differences in meat color were seen at 24 h post mortem. Lightness (L*) was affected by weaning weight (P < 0.01), whereas redness (a*) was influenced by weaning age (P < 0.05). Yellowness (b*) was affected by both age (P < 0.01) and weight (P < 0.05) at weaning. Pork with too high or low L* values at 24 h post mortem is considered as an abnormal meat, for example, the meats with L* lower than 43 are considered as DFD (dark, firm and dry) but the meats with L* higher than 50 are considered as PSE (pale, soft and
© 2014 Japanese Society of Animal Science
Animal Science Journal (2015) 86, 428–434
EFFECT OF WEANING AGE AND WEIGHT IN PIG
Table 4
431
The effects of weaning age and weight on pH and meat color of porcine Longissimus thoracis muscle
Weaning age
21
Weaning weight
L
pH 45min pH 24h Meat color at 45 min postmortem Lightness (L*) Redness (a*) Yellowness (b*) Meat color at 24h post mortem Lightness (L*) Redness (a*) Yellowness (b*)
28
M
H
L
SEM
M
H
Level of significance† wa
6.45 5.68
6.41 5.66
6.38 5.62
6.32 5.70
6.37 5.63
6.29 5.63
0.06 0.04
37.91 6.06 1.78
37.58 5.76 1.56
37.96 5.52 1.70
37.87 5.54 1.60
37.93 5.27 1.48
38.47 5.61 1.71
0.70 0.26 0.18
46.38 6.80 2.68
44.51 6.51 2.75
46.64 7.35 3.55
46.27 6.28 2.24
44.23 6.44 2.45
45.86 6.49 2.72
0.67 0.28 0.23
ww
wa × wg
** * **
*
*P < 0.05; **P < 0.01. †wa, weaning age; ww, weaning weight. Data are means.
Table 5 The effects of weaning age and weight on water-holding capacity and texture property analysis of porcine Longissimus thoracis muscle
Weaning age
21
Weaning weight Water-holding capacity Filter paper fluid uptake (mg) Drip loss (%) Cooking loss (%) Texture property analysis Hardness Cohesiveness Springiness Adhesiveness Gumminess Chewiness
28
SEM
L
M
H
L
M
H
34.69
31.11
30.70
26.65
32.75
30.44
2.87
2.92 27.93
2.61 27.86
2.23 28.36
2.45 27.46
1.76 28.22
2.08 28.38
0.26 0.69
33.73 0.41 0.71 −3.49 13.80 10.90
33.76 0.38 0.65 −3.17 12.96 9.96
31.80 0.46 0.78 −2.34 15.55 12.42
32.67 0.46 0.78 −2.85 15.17 12.19
30.76 0.42 0.74 −2.67 13.31 11.24
32.00 0.42 0.73 −2.98 14.34 11.30
1.28 0.02 0.03 0.35 0.88 0.69
Level of significance† wa
ww
wa × wg
*
*P < 0.05. †wa, weaning age; ww, weaning weight. Data are means.
Table 6
Pearson correlation coefficient (r) of weaning age and weight with carcass and meat quality traits
Weaning age Weaning weight
Weaning weight
Carcass weight
NPPC marbling score
Lightness at 24 h
Redness at 24 h
Yellowness at 24 h
Drip loss
0.26*
0.09 −0.20*
−0.17* 0.13
0.02 0.02
−0.07 −0.04
−0.05 0.15
−0.26** −0.22*
*P < 0.05; **P < 0.01. NPPC, National Pork Producers Council.
exudative) (Joo et al. 1999). In the present study, although the M group had a lower L* value than did the other groups, regardless of weaning age, all the pig groups were under the normal pork quality. The D21 group had higher a* and b* values than did the D28 group. These results are likely related to carcass weight. According to previous reports (Galián et al. 2009; Kim et al. 2013), pigs with higher carcass weight showed lower a* and b* values. The D21 group had lower carcass weight than the D28 group, regardless of weaning weight; therefore, lower a* and b* values were found in the D21 group. Moreover, the L group in D21, which had higher carcass weight than did the M and H groups, showed lower b*, regardless of weaning age. However, no interaction effect of Animal Science Journal (2015) 86, 428–434
weaning age and weight on meat color was seen at 45 min and 24 h post mortem (P > 0.05).
WHC and TPA The results for WHC, including FFU, drip loss and cooking loss are presented in Table 5. Drip loss was affected by weaning age (P < 0.05), but the other WHC measurements were not influenced by weaning age and weight (P > 0.05). In addition, the interaction effect of weaning age and weight was not found in WHC (P > 0.05). Although drip loss was higher in the D21 group than in the D28 group (P < 0.05), the ranges of drip loss were from 1.76% to 2.92%. In general, if the meat shows higher drip loss (i.e. > 6.0%), it is considered as an abnormal meat, such as © 2014 Japanese Society of Animal Science
432 G.-D. KIM et al.
Figure 1 Relationship of weaning age and weight with carcass weight, National Pork Producers Council marbling score, and drip loss.
PSE (Warner et al. 1997; Joo et al. 1999). However, in the present study, all groups presented a lower drip loss than 6.0%. The effects of weaning age and weight and their interaction were not found in any TPA traits (P < 0.05), as shown in Table 5. Texture of meat, especially tenderness, is significantly related to intramuscular fat (IMF) content (Blanchard et al. 1999) and the © 2014 Japanese Society of Animal Science
meat from heavy pigs have high content of IMF and low shear force, in accordance with Kim et al. (2013) and Galián et al. (2009). However, tenderness did not significantly differ among the groups (P > 0.05). We expected that there were effects of weaning age and weight on hardness, because higher carcass weights were found in the L groups and D28 group than found in the M and H groups and D21 group, respectively, as Animal Science Journal (2015) 86, 428–434
EFFECT OF WEANING AGE AND WEIGHT IN PIG
433
Figure 2 Relationship of weaning age and weight with meat color (lightness, redness and yellowness).
shown in Table 3. Considering the result for NPPC marbling score, the D21 group should show lower hardness, but there was no effect of weaning age on hardness (P > 0.05).
Correlation of weaning age and weight with carcass and meat quality traits Pearson’s correlation coefficients (r) were calculated to assess the relationship of weaning age and weight with Animal Science Journal (2015) 86, 428–434
carcass and meat quality traits (Table 6, Figs 1,2). Weaning weight increased with an increase of weaning age (r = 0.26, P < 0.05); however, carcass weight showed a negative correlation with weaning weight (r = −0.20, P < 0.05). Late weaning was related to a decrease in NPPC marbling score (r = −0.17, P < 0.05). A positive relationship between weaning weight and NPPC marbling score (r = 0.13) was seen, but significance was not found (P > 0.05). Drip loss © 2014 Japanese Society of Animal Science
434 G.-D. KIM et al.
showed negative correlations with both age and weight at weaning (r = −0.26, P < 0.01 and r = −0.22, P < 0.05, respectively). Although the effects of weaning age or weight were observed from meat color at 24 h post mortem (Table 4), no significant correlations was found between them (P > 0.05).
ACKNOWLEDGMENTS This work was supported by IPET (the Korea Institute of Planning and Evaluation for Technology in Food, Agriculture, Forestry and Fisheries, No. 112148-3), Republic of Korea.
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Animal Science Journal (2015) 86, 428–434
Animal Science Journal (2015) 86, 428–434
doi: 10.1111/asj.12314
ORIGINAL ARTICLE The influences of weaning age and weight on carcass traits and meat quality of pigs Kyung Bo KO1,*, Gap-Don KIM2,*, Dong-Geun KANG1, Yeong-Hwa KIM1, Ik-Dong YANG1 and Youn-Chul RYU1 1
Division of Biotechnology, College of Applied Life Sciences, Jeju National University, Jeju and 2Department of Food Science and Biotechnology, Kyungnam University, Changwon, Republic of Korea
ABSTRACT The purpose of this study was to establish the effects of weaning age and weight on pigs, and their interaction with carcass traits and meat quality. A total of 468 piglets were obtained from 57 sows and four boars and grouped by age at weaning (D21, 18–24 days; D28, 25–32 days). Each weaning group was subdivided into three weight groups (L, M and H) according to weaning weight. The D28 group had heavier carcass weight, redness and yellowness, but had lower marbling scores and less drip loss than the D21 group (P < 0.05). The pigs with a light weight at weaning had higher carcass weights and lower yellowness than did pigs with a medium or heavy weight at weaning (P < 0.05). Weaning age was found to have a negative correlation with drip loss, while weaning weight was negatively correlated with carcass weight and drip loss (P < 0.05). We concluded that carcass and meat quality traits in pigs were significantly related to their age and weight at weaning. Therefore, we find that piglet weaning age and weight are no less important than post-weaning growth performance and behavior, with regard to carcass traits and meat quality.
Key words: carcass trait, meat quality, pig, weaning age, weaning weight.
INTRODUCTION The weaning of piglets is accompanied by stressors, including maternal separation, relocation to new housing, introduction into a new social group, and change of diet (van der Meulen et al. 2010). Thus, reduction of feed intake and inhibition of piglet growth rate often occur (McCracken et al. 1995). In the conventional weaning system, the range of weaning age is from 17 days to 21 days; however, piglets are weaned at 12–14 days in the early weaning system (Dantzer & Mormede 1981; Maxwell & Carter 2000). In Europe, weaning before 28 days of age is prohibited (ECCD 2001). Some studies have suggested that a decrease in weaning age could improve feed efficiency and growth rate while lowering the transfer of growth-depressing pathogens to offspring (Patience et al. 2000). However, the early weaning system has disadvantages in wean-to-finish average daily gain (ADG), mortality rate and aggressive behaviors (Main et al. 2004). The other contributing factor to post-weaning growth is the weaning weight of piglets. The growth rate tends to be higher in large pigs than small pigs, and the weaning weight and its variation are influenced by the birth weight and its variation in piglets (McConnell et al. 1987; Allen et al. 2010). In previous © 2014 Japanese Society of Animal Science
studies, the heavy weaning weight for piglets weaned at 28 days was 8.5 kg or over, and pigs with a heavy weaning weight had a higher growth rate between weaning and 20 weeks of age than those with a light weaning weight (Mahan et al. 1998; Lawlor et al. 2002; Magowan et al. 2011). The effects of weaning age and weight on postweaning behavior and growth performance have been well established, but published research on their effects on meat quality is lacking. Therefore, the aim of this study was to compare the meat quality of finishing pigs classified by various ages and weights at weaning and to establish the interaction effect of weaning age and weight on pork quality.
MATERIALS AND METHODS Animals and samples Piglets (n = 468; 252 female and 216 male) were obtained from 57 sows and four boars. The sows and sire line semen Correspondence: Youn-Chul Ryu, Division of Biotechnology, College of Applied Life Sciences, Jeju National University, 66 Jejudaehakro, Jeju 690-701, Republic of Korea. (Email: [email protected]) *These authors contributed equally to this work. Received 30 May 2014; accepted for publication 17 July 2014.
EFFECT OF WEANING AGE AND WEIGHT IN PIG
Table 1
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Ingredients and nutrient composition of the diets
Item Ingredient composition (%) Corn Soybean meal Wheat bran Wheat Rapeseed meal Molasses Limestone Tricalcium phosphate NaCl Vitamin† Mineral‡ L-Lysine HCl DL-Methionine Antibiotic Analyzed nutrient and energy content Crude protein (%) Lysine (%) Methionine (%) Digestible energy (Mcal/kg)
Starter diet
Grower diet
Finisher diet
49.7 32.6 – 14.2 – 0.5 0.5 1.6 0.1 0.1 0.1 0.2 0.2 0.3
65.3 27.7 – – – 4.0 0.4 1.9 0.3 0.1 0.1 0.1 – 0.1
69.3 15.7 5.7 – 3.0 4.0 1.0 0.8 0.3 0.1 0.1 0.1 – –
19.5 1.2 0.4 3.5
16.0 0.9 0.3 3.4
14.0 0.8 0.2 3.3
†Supplied per kg of diet: 8100 IU of vitamin A, 1200 IU of vitamin D3, 45 IU of vitamin E, 2.25 mg of vitamin K, 1.5 mg of thiamin, 0.6 mg of riboflavin, 2.55 mg of pyridoxine, 0.03 mg of vitamin B12, 19.5 mg of pantothenic acid, 39 mg of niacin, 0.09 mg of biotin, and 0.75 mg of folic acid. ‡Supplied per kg of diet: 102.7 mg of FeSO4, 0.4 mg of CoSO4, 67 mg of CuSO4, 54,2 mg of MnSO4, 69 mg of ZnSO4, 0.5 mg of CaIO3, and 0.3 mg of Na2SeO3.
Table 2 The number of pigs, weaning age and weight in pig groups
Weaning age Weaning weight
21 L
M
28 H
L
M
SEM H
Number of pigs 65 52 59 63 85 144 Weaning age (day) 21.5 21.8 22.0 29.0 28.9 28.3 0.3 Weaning weight (kg) 5.9 7.3 9.0 5.8 7.4 9.2 0.1 Data are means.
used were Jeju black pigs (a native Korean breed). Sows were artificially inseminated with unfrozen semen from four boars. The mean, maximum and minimum of piglets per sow were 8.2, 11 and four, respectively. The mean age and weight at weaning were 26.6 days and 7.3 kg, respectively. All pigs were allocated randomly to wean-to-finish pens (12 pigs per pen) within a block. The feed and pig production program followed the Korean feeding standard for swine (RDA 2007). The composition of diet is presented in Table 1. The piglets were classified into two groups by their weaning age: D21 (18–24 days) and D28 (25–32 days), as shown in Table 2. The pigs from each weaning age group were then sorted into three blocks based on weaning weight: L, M and H. For D21, the weights were 5.9 ± 0.1 kg (L), 7.3 ± 0.1 kg (M) and 9.0 ± 0.3 kg (H). For D28, the weights were 5.8 ± 0.1 kg (L), 7.4 ± 0.1 kg (M) and 9.2 ± 0.1 kg (H). When the penned pigs ranged from 190 days to 210 days, the pigs were slaughtered at a commercial slaughtering house over 3 days: 156 pigs (13 pens) were slaughtered on each day. Immediately after slaughtering, carcass weight and backfat thickness (at the midline of 4th–5th thoracic vertebrae) were measured. National Pork Producers Council (NPPC) marbling score and meat quality traits were analyzed after 24 h chilling in a cold Animal Science Journal (2015) 86, 428–434
room at 5°C. After chilling, Longissimus thoracis muscles from the left sides of each carcass were taken to analyze meat quality traits, including meat color, water-holding capacity and texture properties.
NPPC marbling score Marbling score was assessed by laboratory staff using the NPPC marbling standard (NPPC 2002). The scales were 1 (being devoid of marbling), 2, 3, 4, 5, 6 and 10 (being abundant in marbling).
pH Muscle pH was measured directly on the Longissimus thoracis (7th–8th thoracic vertebrae) muscle using a portable pH meter (PH27-SS; IQ Scientific Instruments Inc., Loveland, CO, USA) at 45 min and 24 h post mortem.
Meat color Meat color was measured with a chromameter (CR-300; Minolta Co., Tokyo, Japan) at 45 min and 24 h post mortem after exposing the surface to the air for 30 min at 4°C. The chromameter was standardized with a white plate (Y = 93.5, x = 0.3132, y = 0.3198).
Water-holding capacity (WHC) To evaluate WHC, filter-paper fluid uptake (FFU), drip loss and cooking loss were measured. Drip loss was determined by suspending muscle standardized for surface area in an inflated plastic bag for 48 h at 4°C (Honikel 1987). For cooking loss, muscle samples were cooked to 70°C internal temperature and cooking loss was expressed as a percentage of the initial sample weight. FFU was measured according to Kauffman et al. (1986). © 2014 Japanese Society of Animal Science
430 G.-D. KIM et al.
Table 3 The effects of weaning age and weight on carcass weight, backfat thickness and NPPC marbling score
Weaning age
21
28
SEM
Weaning weight
L
M
H
L
M
H
Carcass weight (kg) Backfat thickness (mm) NPPC marbling score
78.68 22.64 1.96
74.22 21.61 2.14
73.10 23.80 2.55
81.19 22.92 1.77
78.61 22.39 1.77
77.12 21.53 1.93
1.31 0.97 0.12
Level of significance† wa
ww
**
**
***
**
wa × wg
**P < 0.01; ***P < 0.0001. †wa, weaning age; ww, weaning weight. Data are means. NPPC, National Pork Producers Council.
Texture property analysis (TPA) TPA was performed using a rheometer (Compac-100; Sun scientific Co., Tokyo, Japan) and force-time deformation curves were obtained with a 20 kg load cell applied at a cross-head speed of 2 mm/s. Hardness, cohesiveness, springiness, adhesiveness, gumminess and chewiness were quantified as described previously (Bourne 1978).
Statistical analysis The experiment was designed as a 2 (D21 and D28 weaning ages) × 3 (L, M, and H weaning weights) factorial. Data were analyzed using a general linear model (SAS 2002) testing for effects of weaning age and weight, and their interactions. Pearson correlation coefficients were evaluated to describe the relationship of weaning age and weight with significant (P < 0.05) carcass and meat quality traits, such as carcass weight, NPPC marbling score, meat color at 24 h and drip loss. All data are presented as means (SE).
weight (L group in D21) did not show the significant differences in backfat thickness from the other groups (P > 0.05) (Table 3). Rather, NPPC marbling score was significantly higher in the H group of D21 (P < 0.05) and the D21 group had higher NPPC marbling score than did the D28 group, regardless of weaning weight (P < 0.0001) (Table 3). Correa et al. (2006) reported that pigs with a slower growth rate had a higher lean and lower fat proportion compared to pigs with a faster growth rate, and a negative relationship between growth rate and carcass quality was reported by McGloughlin et al. (1988). However, in the present study, a conflicting result was found. The pigs with a heavy weight at weaning (H groups) showed lower carcass weight than did the other groups. In particular, group H in D21 had the highest growth rate until weaning; however, it showed the slowest growth rate (the lowest carcass weight) and the highest NPPC marbling score.
RESULTS AND DISCUSSION Carcass weight, backfat thickness and NPPC marbling score
Muscle pH and meat color
The carcass weight of the pigs was influenced by weaning age and weight (P < 0.01). The L group in D21 had significantly higher carcass weight than that from the M and H group (P < 0.05) (Table 3). However, in D28, no significant difference was seen among the weaning weight groups (P > 0.05). The D28 pigs also had higher carcass weight than did the D21 pigs (P < 0.01). These results show that light piglets grow faster than medium or heavy piglets, regardless of weaning age, and weaning at 28 days increases the carcass weight of pigs. In the previous reports, piglets weaned at 42 days were better able to adapt to weaning than were younger piglets, as a result of them having a more developed digestive system (Hay et al. 2001; Jarvis et al. 2008). Wean-to-finish growth performance, including ADG, mortality and weight, improved as weaning age increased from 12 days to 21 days (Fangman et al. 1996; Main et al. 2004). In the present study, older piglets at weaning showed higher carcass weight than did younger piglets, but the piglets of L in D28, which had the slowest growth rate until weaning, showed the highest carcass weight. Other studies reported that backfat thickness and intramuscular fat content increased with an increase in carcass weight (Galián et al. 2009; Kim et al. 2013). However, in the present study, the pigs that had higher carcass
The results for muscle pH and meat color are presented in Table 4. The ranges of muscle pH at 45 min and 24 h post mortem were from 6.29 to 6.45 and from 5.62 to 5.70, respectively. No significant effects of weaning age and weight, or their interaction effect, on muscle pH was seen (P > 0.05). Muscle pH is used to determine the glycolytic rate during the post mortem period (Honikel & Fischer 1977). Muscles with fast glycolysis show low pH at 45 min post mortem (i.e. < 5.80) and are accompanied with muscle protein denaturation in relation to low WHC (Joo et al. 1999; Ryu et al. 2005). In the present study, normal pH values (≥ 5.80) at 45 min post mortem were found. The age and weight of piglets at weaning did not affect meat color at 45 min post mortem (P > 0.05), whereas significant differences in meat color were seen at 24 h post mortem. Lightness (L*) was affected by weaning weight (P < 0.01), whereas redness (a*) was influenced by weaning age (P < 0.05). Yellowness (b*) was affected by both age (P < 0.01) and weight (P < 0.05) at weaning. Pork with too high or low L* values at 24 h post mortem is considered as an abnormal meat, for example, the meats with L* lower than 43 are considered as DFD (dark, firm and dry) but the meats with L* higher than 50 are considered as PSE (pale, soft and
© 2014 Japanese Society of Animal Science
Animal Science Journal (2015) 86, 428–434
EFFECT OF WEANING AGE AND WEIGHT IN PIG
Table 4
431
The effects of weaning age and weight on pH and meat color of porcine Longissimus thoracis muscle
Weaning age
21
Weaning weight
L
pH 45min pH 24h Meat color at 45 min postmortem Lightness (L*) Redness (a*) Yellowness (b*) Meat color at 24h post mortem Lightness (L*) Redness (a*) Yellowness (b*)
28
M
H
L
SEM
M
H
Level of significance† wa
6.45 5.68
6.41 5.66
6.38 5.62
6.32 5.70
6.37 5.63
6.29 5.63
0.06 0.04
37.91 6.06 1.78
37.58 5.76 1.56
37.96 5.52 1.70
37.87 5.54 1.60
37.93 5.27 1.48
38.47 5.61 1.71
0.70 0.26 0.18
46.38 6.80 2.68
44.51 6.51 2.75
46.64 7.35 3.55
46.27 6.28 2.24
44.23 6.44 2.45
45.86 6.49 2.72
0.67 0.28 0.23
ww
wa × wg
** * **
*
*P < 0.05; **P < 0.01. †wa, weaning age; ww, weaning weight. Data are means.
Table 5 The effects of weaning age and weight on water-holding capacity and texture property analysis of porcine Longissimus thoracis muscle
Weaning age
21
Weaning weight Water-holding capacity Filter paper fluid uptake (mg) Drip loss (%) Cooking loss (%) Texture property analysis Hardness Cohesiveness Springiness Adhesiveness Gumminess Chewiness
28
SEM
L
M
H
L
M
H
34.69
31.11
30.70
26.65
32.75
30.44
2.87
2.92 27.93
2.61 27.86
2.23 28.36
2.45 27.46
1.76 28.22
2.08 28.38
0.26 0.69
33.73 0.41 0.71 −3.49 13.80 10.90
33.76 0.38 0.65 −3.17 12.96 9.96
31.80 0.46 0.78 −2.34 15.55 12.42
32.67 0.46 0.78 −2.85 15.17 12.19
30.76 0.42 0.74 −2.67 13.31 11.24
32.00 0.42 0.73 −2.98 14.34 11.30
1.28 0.02 0.03 0.35 0.88 0.69
Level of significance† wa
ww
wa × wg
*
*P < 0.05. †wa, weaning age; ww, weaning weight. Data are means.
Table 6
Pearson correlation coefficient (r) of weaning age and weight with carcass and meat quality traits
Weaning age Weaning weight
Weaning weight
Carcass weight
NPPC marbling score
Lightness at 24 h
Redness at 24 h
Yellowness at 24 h
Drip loss
0.26*
0.09 −0.20*
−0.17* 0.13
0.02 0.02
−0.07 −0.04
−0.05 0.15
−0.26** −0.22*
*P < 0.05; **P < 0.01. NPPC, National Pork Producers Council.
exudative) (Joo et al. 1999). In the present study, although the M group had a lower L* value than did the other groups, regardless of weaning age, all the pig groups were under the normal pork quality. The D21 group had higher a* and b* values than did the D28 group. These results are likely related to carcass weight. According to previous reports (Galián et al. 2009; Kim et al. 2013), pigs with higher carcass weight showed lower a* and b* values. The D21 group had lower carcass weight than the D28 group, regardless of weaning weight; therefore, lower a* and b* values were found in the D21 group. Moreover, the L group in D21, which had higher carcass weight than did the M and H groups, showed lower b*, regardless of weaning age. However, no interaction effect of Animal Science Journal (2015) 86, 428–434
weaning age and weight on meat color was seen at 45 min and 24 h post mortem (P > 0.05).
WHC and TPA The results for WHC, including FFU, drip loss and cooking loss are presented in Table 5. Drip loss was affected by weaning age (P < 0.05), but the other WHC measurements were not influenced by weaning age and weight (P > 0.05). In addition, the interaction effect of weaning age and weight was not found in WHC (P > 0.05). Although drip loss was higher in the D21 group than in the D28 group (P < 0.05), the ranges of drip loss were from 1.76% to 2.92%. In general, if the meat shows higher drip loss (i.e. > 6.0%), it is considered as an abnormal meat, such as © 2014 Japanese Society of Animal Science
432 G.-D. KIM et al.
Figure 1 Relationship of weaning age and weight with carcass weight, National Pork Producers Council marbling score, and drip loss.
PSE (Warner et al. 1997; Joo et al. 1999). However, in the present study, all groups presented a lower drip loss than 6.0%. The effects of weaning age and weight and their interaction were not found in any TPA traits (P < 0.05), as shown in Table 5. Texture of meat, especially tenderness, is significantly related to intramuscular fat (IMF) content (Blanchard et al. 1999) and the © 2014 Japanese Society of Animal Science
meat from heavy pigs have high content of IMF and low shear force, in accordance with Kim et al. (2013) and Galián et al. (2009). However, tenderness did not significantly differ among the groups (P > 0.05). We expected that there were effects of weaning age and weight on hardness, because higher carcass weights were found in the L groups and D28 group than found in the M and H groups and D21 group, respectively, as Animal Science Journal (2015) 86, 428–434
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433
Figure 2 Relationship of weaning age and weight with meat color (lightness, redness and yellowness).
shown in Table 3. Considering the result for NPPC marbling score, the D21 group should show lower hardness, but there was no effect of weaning age on hardness (P > 0.05).
Correlation of weaning age and weight with carcass and meat quality traits Pearson’s correlation coefficients (r) were calculated to assess the relationship of weaning age and weight with Animal Science Journal (2015) 86, 428–434
carcass and meat quality traits (Table 6, Figs 1,2). Weaning weight increased with an increase of weaning age (r = 0.26, P < 0.05); however, carcass weight showed a negative correlation with weaning weight (r = −0.20, P < 0.05). Late weaning was related to a decrease in NPPC marbling score (r = −0.17, P < 0.05). A positive relationship between weaning weight and NPPC marbling score (r = 0.13) was seen, but significance was not found (P > 0.05). Drip loss © 2014 Japanese Society of Animal Science
434 G.-D. KIM et al.
showed negative correlations with both age and weight at weaning (r = −0.26, P < 0.01 and r = −0.22, P < 0.05, respectively). Although the effects of weaning age or weight were observed from meat color at 24 h post mortem (Table 4), no significant correlations was found between them (P > 0.05).
ACKNOWLEDGMENTS This work was supported by IPET (the Korea Institute of Planning and Evaluation for Technology in Food, Agriculture, Forestry and Fisheries, No. 112148-3), Republic of Korea.
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Animal Science Journal (2015) 86, 428–434
