management system and fasting period on physiological indicators and meat quality traits of lambs

Meat Science 116 (2016) 67–77

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Effects of pre-slaughter diet/management system and fasting period on physiological indicators and meat quality traits of lambs Serhat Karaca ⁎, Sibel Erdoğan, Dilek Kor, Aşkın Kor Department of Animal Science, Faculty of Agriculture, Yuzuncu Yıl University, 65080, Van, Turkey

a r t i c l e

i n f o

Article history: Received 7 September 2015 Received in revised form 21 January 2016 Accepted 25 January 2016 Available online 28 January 2016 Keywords: Pre-slaughter stress Carcass Muscle glycogen Cortisol Barley

a b s t r a c t This study determined the effects of pre-slaughter diet/management system on blood and rumen parameters and meat-quality traits of Norduz lambs. Eighty lambs were divided into two groups according to diet (AH: alfalfa hay; BAH: alfalfa supplemented with 500 g/head barley) for 21 days. Following this period, lambs from each group were distributed among four groups according to pre-slaughter fasting period as 0, 12, 24 or 48 h. Cortisol concentrations were found to be significantly higher in the 24 h and 48 h groups when compared to the 0 h group (p b 0.01). Diet and fasting period had limited effect on muscle glycogen content and ultimate pH·L*, WHC and moisture decreased in line with increases in the fasting period (p b 0.01). In conclusion, carcass conformation and some meat quality traits were better in BAH lambs. Fasting had a negative effect on some meat quality parameters, with significant increases in some physiological stress indicators after fasting periods of 24 h or longer. © 2016 Elsevier Ltd. All rights reserved.

1. Introduction Farm animals are exposed to various levels of stress during certain periods of the production process, such as the short period of time in which they are transferred to the slaughterhouse. Stress factors related to certain management practices during this time can have a considerable effect on both animal welfare and meat quality. Feeding management is one of the most important factors to affect animal welfare and meat quality prior to slaughter. Animals are sometimes fasted for over 48 h between transport and slaughter. The combined effect of pre-slaughter diet, fasting and additional stress factors may considerably reduce muscle glycogen reserves. Pre-slaughter factors such as feeding system and fasting period have also been found to negatively affect meat quality by increasing serum cortisol and ultimate meat pH levels (Kannan et al., 2014; Zimerman, Domingo, Grigioni, Taddeo, & Willems, 2013). A linear relationship has been found between muscle glycogen levels and metabolic energy levels of rations (Jacob, Pethick, & Chapman, 2005; Pethick & Rowe, 1996), with a number of studies reporting that feeding high-energy rations for several weeks in cattle (Gallo, Apaoblaza, Pulidoa, & Jerez-Timaurec, 2013; Immonen, Ruusunen, Hissa, & Puolanne, 2000) and high level feed intake in longer periods in sheep (Pethick & Rowe, 1996) before slaughter may help prevent stress-related problems such as dark cutting meat. However, the majority of research on this subject has involved yearling or older sheep, with few comprehensive studies conducted with young animals (Edwards & Babiszewski, 2013). ⁎ Corresponding author. E-mail address: [email protected] (S. Karaca).

http://dx.doi.org/10.1016/j.meatsci.2016.01.014 0309-1740/© 2016 Elsevier Ltd. All rights reserved.

Therefore, this study evaluated the effects of pre-slaughter fasting period on blood, rumen, slaughter and carcass characteristics and meat-quality parameters in male lambs fed with only roughage and those fed a barley-supplemented diet for 21 days prior to slaughter. The effects of pre-slaughter fasting periods of different lengths were also examined. The findings of this study may be used in the development of pre-slaughter management practices aimed at reducing animal stress and economic loss. 2. Materials and methods 2.1. Animal material and feeding management Animal research procedures were conducted with the approval of the Local Animal Ethics Committee of Yuzuncu Yıl University in Van, Turkey (Decision No. 2015/03). The animal material used in the study consisted of 80 7-month-old male Norduz lambs. Lambs were kept in the pens (1.6 m2 per lamb) in the outdoor sheepfold until slaughter. Following a 15-day period during which lambs were fed ad-libitum alfalfa hay in order to determine average feed consumption values, they were divided into two groups (n = 40) according to feed content based on NRC (1985) during finishing, as follows: AH: alfalfa hay (1750 g/lamb/day); BAH: barley-supplemented alfalfa hay (1250 g alfalfa hay + 500 g barley/lamb/day). Nutrient contents of alfalfa hay and barley used in the experiment are presented in Table 1. The difference in energy intake between diets was intended to be minimal, so as to avoid any effect of diet on carcass characteristics and meat quality being confounded by differences between treatments for live weight at the commencement of fasting. Lambs were fed according to these

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S. Karaca et al. / Meat Science 116 (2016) 67–77

2.5. Carcass characteristics and meat quality analysis

Table 1 Nutrient contents (%) of feed. Nutrient matter

Alfalfa hay

Barley

Dry matter (DM) Crude ash Crude protein Ether extract Crude cellulose Neutral detergent fiber (NDF) Acid detergent fiber (ADF) Energy, kcal/kg DM

95.88 11.87 13.51 0.44 28.03 43.82 31.67 2486.13

97.19 2.61 11.68 1.74 5.71 27.69 6.38 2895.67

regimes for a 15-day adjustment period that allowed the animals in the BAH group to adjust to the barley supplementation, followed by a 21day finishing period. At the end of the finishing period, feed was removed for 12 h then lambs were weighed to determine final body weight. To determine weight loss during fasting all lambs' full weighs and their fasted weigh were recorded prior to slaughter. After weighing, equal numbers of lambs from both groups were randomly placed into 1 of 4 groups (0, 12, 24 and 48 h) according to the length of pre-slaughter fasting period. However, three animals were removed due to reasons unrelated to treatment. Lambs were housed in the same pens which used for the finishing period until slaughter. Animals were allowed ad-libitum water during fasting.

2.2. Feed analyses Dry matter, crude ash, crude protein and ether extract analyses of hay and barley were performed based on the AOAC (2000). NDF and ADF contents were determined according to Van Soest and Robertson (1979).

2.3. Blood sampling and analyses Blood samples were taken from the vena jugularis of 20 lambs from each group at days 0, 11 and 21 of the finishing period and from all lambs immediately before slaughter. Samples were centrifuged at 5000 rpm for 10 min within 1 h of collection, and serum was stored for further analysis at −80 °C. Serum glucose (glucose oxidase method), triglyceride (glycerol phosphate dehydrogenase test method), blood urea nitrogen (BUN) (urease test method), lactate dehydrogenase (LDH) (IFCC method), total protein (biuret method) and creatine kinase (CK) (adenosine triphosphate method) levels were measured using Bioanalitik™ kits with an Olympus AU400 chemical analyzer. Serum cortisol, insulin, T3, and T4 levels were measured by chemiluminescence microparticle immunological analysis using Abbott™ kits with an Architect c8000 (Burtis, Ashwood, & Bruns, 2013).

2.4. Rumen fluid sampling and analyses In addition to blood samples, approximately 250 mL of rumen fluid was collected by oral probe from 20 randomly selected lambs in each group 5 h after feeding (Nordlund & Garrett, 1994) on days 0, 11 and 21 of the finishing period and from all lambs before slaughter. Rumen pH was measured using an Orion 720 digital pH meter accurate to 0.01. Ammonia content in rumen fluid was determined according to Akkan (1983). Rumen volatile fatty acids (VFA) analysis was conducted using a high-pressure liquid chromatography (HPLC) with a Schimazdzu UV detector and an Alltech IOA-1000 HPLC column (column length: 3000 mm; inner dia.: 7.8 mm) using 0.004 M sulfuric acid 50 °C as an isocratic mobile phase. Total HPLC working time was 50 min (Peu, Béline, & Martinez, 2004).

Lambs were slaughtered at the experimental abattoir unit in research farm without transportation. Hot carcass and offal weights were determined at slaughter. Following slaughter, carcasses were stored at 4 °C for 24 h, after which carcasses were measured based on Bonvillani et al. (2010) and cut into pieces according to Colomer-Rocher, Morand-Fehr, & Kirton (1987). Meat quality characteristics were assessed using samples taken from the m. longissimus thoracis [LT] (between the 6th and 13th ribs). Color and water-holding capacity were analyzed within 2 h after sampling, and the samples were then placed on polystyrene trays, overwrapped with an oxygen-permeable PVC film and stored at 4 °Cfor 72 h. Samples were then placed in vacuum bags to be kept until texture analysis and stored at −18 °C for a month. Meat pH measurements were obtained at 45 min (pH45 min), 8 h (pH8 h) and 24 h (pH24 h) from left half-carcasses and at 72 h (pH72 h) from LT samples (the 12th–13th ribs) using a pH meter (Hanna HI 99163) with the probe inserted into the muscle to a depth of approximately 3 cm. Meat color was evaluated with a CIELAB-illuminant D65/10° movable spectrophotometer (Lovibond RT-300) using samples taken from the left half-carcass (the 11th–12th ribs). The measurements were performed on a freshly cut surface of 2.5 cm thick samples after allowing the muscle surface to bloom in the chiller at 4 °C for 30 min L*(luminosity), a*(redness), and b*(yellowness) were measured at 3 fat-free areas on the surface of each sample, and the average measurements were calculated and recorded. Chroma value and hue angle were calculated using the equations C* = [(a*)2 + (b*)2]1/2 and h* = tan− 1(b*/a*), respectively. Meat water-holding capacity was determined using the filter-paper press method (Wierbicki & Deatherage, 1958). Texture analysis was performed on samples (aging for 72 h at 4 °C after slaughter) taken from the left half-carcass LT(the 6th–11th ribs) that had been stored at −18 °C for 1 month and then allowed to thaw overnight (~ 12 h) at 4 °C. Samples were weighed and placed in thin, heat-resistant plastic bags that were then sealed and placed in a water bath at 75 °C for 1 h (Hoffman, Muller, Cloete, & Schmidt, 2003). After cooking, the bags were cooled under running tap water for 1 h. Samples were removed from the bags, the meat surfaces were dried with paper towels, and the meat samples were reweighed in order to calculate cooking losses (%). Following weighing, the cooked meats were again stored overnight (~12 h) at 4 °C until texture analysis. A coring device was used to obtain 3 cores per sample (1-cm dia. × 1.5 cm) taken parallel to the direction of the muscle fibers. Shear force values were analyzed using a texture analyzer (TA. XT plus) equipped with a Warner Bratzler V-slot blade. Shear testing was performed with a 50-kg load cell, a cross-head speed of 200 mm/min and a blade-penetration depth of 20 mm (Kannan, Kouakou, Terrill, & Gelaye, 2003), with the average of the 3 core values calculated and recorded for each sample. Nutrient analysis was performed on LT samples taken from the right half-carcass (the 6th–12th ribs) that had been stored at − 18 °C for 1 month and then thawed overnight (~12 h) at 4 °C. Thawed samples were homogenized, and dry matter (950.46), ash (920.153), fat (960.39-ether extract) and protein (928.08-Kjeldahl) contents were measured according to AOAC (2000). 2.6. Glycogen concentrations Glycogen concentrations were evaluated from samples taken from the right half-carcass LT (the 12th–13th ribs) and the middle of the central liver lobe during the first 30 min post-slaughter and immediately transferred to a liquid nitrogen tank for storage at −80 °C until glycogen analysis (~1 month). The amounts of glycogen in muscle and liver tissue were quantitatively assessed (Carroll, Longley, & Roe, 1956; Roe, Bailey, Gray, & Robinson, 1961).

S. Karaca et al. / Meat Science 116 (2016) 67–77

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Table 2 Least square means for live weight changes of lambs during the experiment, by diet and fasting period. Diet (D)

IBW, kg FBW, kg ADG, g WBF, kg SW, kg FL, %

Fasting periods (F)

p value

BAH (n = 39)

AH (n = 38)

SEM

0h (n = 20)

12 h (n = 20)

24 h (n = 19)

48 h (n = 18)

SEM

D

F

DxF

35.02 36.92 90.66 39.38 37.21 7.37

35.26 35.94 32.33 38.17 35.89 7.90

0.741 0.729 9.580 0.790 0.755 0.332

35.62 36.64 48.57 38.50 38.50a –

34.66 36.49 87.14 39.10 37.47a,b 4.17c

34.99 36.34 64.23 38.64 35.35a,b 8.54b

35.29 36.26 46.03 38.88 34.89b 10.19a

1.048 1.031 13.545 1.118 1.067 0.406

0.601 0.346 b0.001 0.245 0.220 0.272

0.831 0.994 0.125 0.985 0.046 b0.017

0.941 0.997 0.749 0.998 0.998 0.893

a,b

Different superscript letters in the same row represent significant differences (p b 0.05). BAH: Barley + alfalfa hay; AH: Alfalfa hay. IBW: initial body weight; FBW: final body weight; ADG: average daily gain; WBF: weight before fasting; SW: slaughter weight; FL: fasting loss.

2.7. Sensory panel testing Sensory panel testing was performed on samples taken from the right half-carcass LT (the 6th–12th ribs) that had been stored at −18 °C and thawed overnight (~12 h) at 4 °C. Samples were wrapped in aluminum foil and cooked in an electric oven set at 180 °C until the internal temperatures reached 80 °C according to Testo 175-T3 datalogger (equipped with thermocouples) placed in the sample geometric midpoint. Cooked samples were cut into 1-cm3 pieces, wrapped in aluminum foil and kept at 60 °C until evaluation (Ekiz et al., 2009). Samples were evaluated by 26 semi-trained panelists and rated on a scale of 1 to 9 for tenderness, juiciness, flavor and overall liking (Adnoy et al., 2005). A total of 8 samples were used in the evaluations, with unsalted crackers and water provided to panelists between samples. 2.8. Statistical analysis Data were analyzed using the MINITAB 13.1 program with one-way analysis of variance (ANOVA). Tukey's Multiple Comparison Test was used to identify any significant differences between more than two groups. The Kruskal–Wallis test was used to evaluate the sensory analysis. With the exception of sensory characteristics, all characteristics in the study were examined using the mathematical model yijk = μ + ai + bj + (ab)ij + eijk, where yijk = the value of the examined characteristic for the kth animal in the jth fasting-period group from the ith diet group; μ = overall mean; ai = the fixed effect of diet (i = barley + alfalfa, barley); bj = fixed effect of fasting period (j = 0,12,24,48 h); (ab)ij = interaction of the effects; and eijk = residual random error. 3. Results and discussion 3.1. Body weight, rumen and blood parameters The group fed with barley-supplemented alfalfa (BAH) had significantly higher average daily gain (ADG) than the group fed with alfalfa only (AH) (p b 0.001) (Table 2). This can be attributed to the higher

energy of the BAH ration and is consistent with Mushi, Safari, Mtenga, Kifaro, & Eik (2009). Daily feed consumption during the finishing period was 1.63 ± 0.074 kg/lamb for the BAH group and 1.56 ± 0.084 kg/lamb for the AH group. Therefore, BAH lambs have 10.0 ± 0.91% more energy than AH lambs (4099 ± 187 vs 3727 ± 200 kcal/lamb/day DM). Significant differences were also found among the fasting-period groups in terms of slaughter weight (p b 0.05) and live weight loss (p b 0.001), with live weight loss significantly increasing as a result of increases in the length of the fasting period (Table 2). A considerable part of the difference in live weight losses between fasting groups can be accounted for by decreases in rumen content as well as other bodypart weights (Table 5). Previous research has indicated a rapid loss in live weight for the first 12–24 h of fasting before slaughter (Fisher, Muir, & Gregory, 2011), with fasting for 24 h and longer resulting in live weight losses of 7%–10% in sheep (Cole, 1995; Kannan et al., 2014). Researchers noted that such losses might be related to gastrointestinal secretions and diversity of their contents as well as catabolism and dehydration. Fisher et al. (2011) reported that live weight loss was faster among the lambs fed with feed with high digestibility. However, in this study, weight changes did not vary significantly between BAH and AH lambs with the same fasting periods. While volatile fatty acids (VFA) did not change significantly, rumen pH increased significantly over the course of the experiment (p b 0.01) (Table 3). It is possible to suggest that barley consumption led to a gradual increase in rumen buffer capacity of the BAH lambs that would account for the difference between rumen pH at the beginning and end of the experiment. Whereas rumen pH (p b 0.01) and NH3-N contents (p b 0.001) were higher for AH lambs when compared to BAH lambs, VFA content was higher for BAH lambs when compared to AH lambs (p b 0.01). Moreover, the interaction of diet and sampling day was not significant for rumen parameters. These findings are in line with a previous study reporting that an addition of 600 g grain feed (e.g. barley, wheat) per sheep per day to a roughage-based ration reduces the pH of the rumen environment (du Toit, Van Niekerk, Hassen, Rethman, & Coertze, 2006). Similarly, the present study's findings that BAH lambs had higher propionic and butyric acid ratios and lower acetic acid ratios when compared to AH lambs (p b 0.001) (Table 3) is also

Table 3 Least square means for rumen parameters and volatile fatty acid profile of lambs, by diet and days of finishing. Days of finishing (T)

Diet (D)

pH NH3-N, mg/100mL Acetic acid, % Butyric acid, % Propionic acid, % VFA, mmol/L

p value

BAH (n = 20)

AH (n = 20)

SEM

1 (n = 40)

11 (n = 40)

21 (n = 40)

SEM

D

T

DxT

6.69 149.3 60.59 13.53 25.84 121.5

6.81 204.4 66.03 10.63 23.35 118.3

0.026 5.68 0.240 0.239 0.247 0.810

6.67b 179.2 64.10a 11.66b 24.22 120.3

6.76a,b 179.7 63.50a 11.92a,b 24.58 119.3

6.83a 171.7 62.33b 12.66a 24.99 120.1

0.032 6.96 0.294 0.293 0.302 0.992

0.003 b0.001 b0.001 b0.001 b0.001 0.006

0.004 0.664 b0.001 0.047 0.202 0.764

0.582 0.927 0.125 0.164 0.068 0.179

a,b,c Different superscript letters in the same row represent significant differences (p b 0.05). BAH: barley + alfalfa hay; AH: alfalfa hay.

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S. Karaca et al. / Meat Science 116 (2016) 67–77

Table 4 Least square means for serum hormone and metabolites of lambs, by diet and days of finishing. Days of finishing (T)

Diet (D)

Glucose, mg/dL Trigliseride, mg/dL BUN, mg/dL Total protein, g/dL Insuline, Pmol/L

p value

BAH (n = 20)

AH (n = 20)

SEM

1 (n = 40)

11 (n = 40)

21 (n = 40)

SEM

D

T

DxT

57.39 32.65 22.22 6.34 5.94

53.30 34.56 25.31 6.50 5.29

1.453 1.130 0.721 0.098 0.318

54.30a,b 28.44b 22.77 6.03b 4.82b

51.93b 34.90a 23.40 6.51a 5.52a,b

60.10a 37.48a 25.13 6.72a 6.51a

1.780 1.385 0.883 0.120 0.390

0.039 0.234 0.003 0.241 0.153

0.005 b0.001 0.153 b0.001 0.010

b0.001 0.081 0.099 0.064 0.203

a,b

Different superscript letters in the same row represent significant differences (p b 0.05). BAH: barley + alfalfa hay; AH: alfalfa hay.

in line with earlier studies (Fimbres, Kawas, Hernández-Vidal, PicónRubio, & Lu, 2002; Steele, AlZahal, Hook, Croom, & McBride, 2009). The NH3-N increase observed in the rumens of AH lambs could be attributed to a lack of energy in the environment available to rumen microorganisms. Table 4 shows the changes in certain blood parameters over the course of finishing for both feed groups. Serum glucose concentrations were significantly lower in the AH group when compared to the BAH group (p b 0.05). Increases in the amounts of butyric and propionic acid in the rumen are known to increase blood glucose levels and stimulate insulin production leading to increases in blood insulin levels (Sano et al., 1999). As Table 4 shows, serum insulin and glucose concentrations in this study reached their highest levels at the end of finishing (p b 0.05). Serum BUN was also found to be significantly higher in the AH lambs when compared to the BAH lambs. This difference might be attributable to an increase in NH3-N amounts in the rumen as a result of decreases in microorganism activity in the AH lambs (Table 4). Rumen parameters at slaughter, by diet and fasting period, are presented in Table 5. While AH lambs were found to have higher pH and acetic acid levels in comparison to BAH lambs (p b 0.05), BAH lambs had higher butyric acid and total VFA levels (p b 0.001). Moreover, the interaction between diet group and fasting was found significant, with percentages of acetic acid increasing and butyric acid decreasing in the BAH lambs that were fasted, whereas no significantly change in these percentages were observed in AH lambs (p b 0.05). In line with similar studies (Galyean, Lee, & Hubbert, 1981; Gregory, 1998), rumen pH exhibited an expected increase to near neutral pH (p b 0.001), and VFA content decreased (p b 0.001) as expected with increases in the fasting period; however, the effect of fasting on VFA changes was greater for the AH group than for the BAH group (p b 0.01). NH3-N rose to its highest level in the 12-h fasting group, but it decreased with longer fasting periods, as concentrations of fermentation end-products decreased in the rumen following the cessation of feed intake (p b 0.001). Prolonged fasting periods cause changes in ruminal fermentation, electrolyte balances and hormonal and metabolite adaptations (Squires, 2010). The effects of diet and fasting periods on some blood parameters are presented in Table 6. Pre-slaughter fasting and feed limitations may have an effect on serum cortisol, catabolism-related blood metabolites

and other stress indicators (Fisher et al., 2011; Zimerman et al., 2013). This study found blood urea nitrogen (BUN), creatine kinase (CK), triglyceride (TG), and cortisol (CORT) levels increased while serum T3 and T4 concentrations decreased with increases in the length of the fasting period; these changes were especially notable among lambs in the 24 h and 48 h groups. In addition, a negative correlation was found between cortisol and total VFA content (r = −0.360; p b 0.001). However, the interaction between diet and fasting period did not have a significant effect on any of the above-mentioned blood parameters. Previous studies have also reported increases in cortisol concentrations in association with pre-slaughter fasting and feed limitations (Kannan et al., 2000; Murayama et al., 1986; Zimerman et al., 2013). Although serum cortisol concentrations were found to increase in connection with fasting stress in the 24 h and 48 h groups, preslaughter fasting was not found to have a significant effect on serum glucose concentrations. Similar blood glucose concentrations have been previously reported for sheep fasted for 24 h (Kannan et al., 2014) and for 30 h (Fisher et al., 2011). It is possible that increases in blood glucose levels due to fasting are more severe with longer fasting periods, but that these increases are masked by greater drops in blood glucose levels in connection with fasting itself, making it difficult to clearly evaluate the findings related to blood glucose levels. Serum triglyceride concentrations in the present study were similar for the BAH and AH lambs; however, lambs in the 24 h and 48 h fasting groups had significantly higher serum triglyceride levels when compared to the 0 h and 12 h fasting groups (p b 0.001) (Table 6). Once glycogen reserves have been exhausted in the liver, triglycerides are broken down into free fatty acids that are used as the main energy source of muscles (Gregory, 1998). A rise in triglyceride levels in line with increases in the length of the fasting period has been previously reported (Fisher et al., 2011). This study found significant differences in serum BUN concentrations at slaughter between both diet and fasting groups. BUN concentrations were higher in AH lambs when compared to BAH lambs (Table 6). Furthermore, serum BUN concentrations were significantly higher in the 24 h fasting group when compared to the 0 h and 12 h groups (p b 0.001); however, after 48 h fasting, these concentrations were found to have dropped to a level similar to that of the 12 h fasting group. Increases in BUN in sheep and goats have been previously

Table 5 Least square means for rumen parameters of lambs, by diet and fasting period. Diet (D)

pH NH3-N, mg/100 mL Acetic acid, % Butyric acid, % Propionic acid, % VFA, mmol/L

Fasting period (F)

p value

BAH (n = 39)

AH (n = 38)

SEM

0h (n = 20)

12 h (n = 20)

24 h (n = 19)

48 h (n = 18)

SEM

D

F

DxF

7.17 128.2 61.48 16.34 22.19 57.13

7.28 120.5 65.60 12.81 21.46 49.48

0.035 5.47 0.229 0.302 0.317 0.553

6.61c 102.0b 61.94c 15.12 22.68 117.18a

7.12b 217.2a 64.71a 14.15 21.14 52.03b

7.57a 90.83b 63.45b 14.77 21.78 29.40c

7.60a 87.33b 64.07a,b 14.25 21.69 14.61d

0.049 7.735 0.322 0.427 0.447 0.782

0.028 0.324 b0.001 b0.001 0.109 b0.001

b0.001 b0.001 b0.034 0.329 0.109 b0.001

0.504 0.903 0.003 0.022 0.216 0.001

a,b,c,d Different superscript letters in the same row represent significant differences (p b 0.05). BAH: barley + alfalfa hay; AH: alfalfa hay.

S. Karaca et al. / Meat Science 116 (2016) 67–77

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Table 6 Least square means for serum hormones and metabolites of lambs, by diet and fasting period. Diet (D)

GLU, mg/dL INSL, Pmol/L BUN, mg/dL TPRO, g/dL CK, U/L TG, mg/dL LDH, U/L CORT, nmol/L T3, ng/mL T4, ng/mL

Fasting periods (F)

p value

BAH (n = 39)

AH (n = 38)

SEM

0h (n = 20)

12 h (n = 20)

24 h (n = 19)

48 h (n = 18)

SEM

D

F

DxF

67.29 3.80 25.13 7.14 172.3 40.29 892.3 19.73 0.71 67.17

59.70 3.17 28.42 7.04 174.5 40.46 829.3 21.08 0.59 55.62

3.757 0.357 0.825 0.146 9.25 2.144 35.02 2.926 0.015 1.596

67.05 5.38a 18.98c 7.15 147.4b 32.90b 850.3 11.04b 0.68a,b 64.31a,b

60.25 4.50a 26.85b 6.73 151.7b 29.60b 849.7 15.45a,b 0.69a 65.46a

58.37 1.95b 36.84a 7.08 202.9a 45.62a 884.1 27.45a 0.62a,b 58.26a,b

68.31 2.13b 24.44b 7.41 191.6a,b 53.38a 859.2 27.67a 0.60b 57.56b

5.310 0.502 1.167 0.206 13.07 2.355 49.50 4.136 0.021 2.255

0.157 0.215 0.006 0.634 0.868 0.954 0.208 0.749 b0.001 b0.001

0.474 b0.001 b0.001 0.159 0.005 b0.001 0.955 0.009 0.022 0.028

0.990 0.598 0.757 0.408 0.120 0.465 0.403 0.885 0.871 0.996

a,b,c Different superscript letters in the same row represent significant differences (p b 0.05). BAH: barley + alfalfa hay; AH: alfalfa hay. GLU: glucose, INSL: insulin, BUN: blood urea nitrogen; TPRO: total protein; CK: creatine kinase, TG: triglyceride, LDH: lactate dehydrogenase, CORT: cortisol.

reported to occur as a result of long fasting periods (Kannan et al., 2000), possibly in connection with protein catabolism (Gregory, 1998; Liu, Zhong, Zhou, Sun, & Zhao, 2012). Serum CK activity is generally considered to be an indicator of skeletal-muscle injury due to trauma as well as muscle activity and myopathy related to feeding regimen (Hoffmann & Solter, 2008). In the present study, serum CK did not vary significantly between the BAH and AH groups; however, serum CK increased significantly with increases in the fasting period (Table 6). Liu et al. (2012) also reported high serum CK levels in sheep fasted for 24 and 48 h. However, other studies have reported neither pre-slaughter feeding regimen (Kannan et al., 2014) nor a 24-h fasting period (Kannan et al., 2014; Zimerman, Grigioni, Taddeo, & Domingo, 2011) to have a significant effect on CK activity. Stress occurring as a result of insufficient feeding significantly reduces thyroid activity and decreases production of T3 from T4 (Squires, 2010). The present study found significantly lower serum T3 and T4 levels in the AH group when compared to the BAH group (p b 0.01)(Table 6). Previous studies have similarly reported highenergy feeding to increase T3 and T4 hormone levels (Shetaewi & Ross, 1991). T3 and T4 levels were significantly lower in lambs fasted for 48 h when compared to lambs fasted for 0 and 12 h (p b 0.05). This is in line with previous studies reporting decreases in plasma T3 and T4 concentrations of sheep following limitations in feed intake (Ekpe & Christopherson, 2000). Wronska, Niezgoda, Sechman, and Bobek (1990) have suggested that the secretion of hormones that normally increase with stress, such as T3 and T4, may be suppressed by fasting, possibly in connection with a conservation of energy reserves.

3.2. Slaughter and carcass characteristics Although slaughter and carcass characteristics were affected by both diet and fasting, there was no significant interaction between diet and fasting group (Tables 7, 8 and 9). Carcass weights and dressing percentages were significantly higher and chilling loss significantly lower in the BAH group when compared to the AH group (p b 0.05). The heavier rumen contents found in the AH group when compared to the BAH group (approximately 1.3 kg, or 1.7%) had a considerable effect on the difference in dressing percentages between feed groups (p b 0.001). Similarly, Mahgoub, Lu, and Early (2000) and Papi, Mostafa-Tehrani, Amanlou, and Memarian (2011) reported contents of the digestive system to increase with increases in ration fiber content and decreases in energy content. Previous studies have also reported differences in fat deposition and organ weight related to feeding regimen to have an effect on dressing percentages (Diaz et al., 2002). In the present study, omental–mesenteric fat weights were found to be significantly higher in the BAH group when compared to the AH group (p b 0.05). With regard to fasting period, the present study found slaughter weight to vary significantly between the 0 h and 48 h groups (p b 0.05) (Table 7), whereas the effect of fasting period on hot and cold carcass weights was not significant. These findings are consistent with previous studies showing that carcass weights of sheep fasted for 16 h (Diaz et al., 2002), 30 h (Fisher et al., 2011) and 90 h (Edwards & Babiszewski, 2013) did not vary significantly. In contrast to these findings, Thompson, O'Halloran, McNeill, Jackson-Hope, & May (1987)

Table 7 Least square means for slaughter characteristics of lambs, by diet and fasting period. Diet (D) BAH (n = 39) Slaughter weight, kg Hot carcass, kg Dressing, % Offals Head, kg Four feet, kg Pelt, kg OMSF, g HLL, kg Spleen, g RR, kg RR content, kg

Fasting periods (F)

p value

AH (n = 38)

SEM

0h (n = 20)

12 h (n = 20)

37.21 17.51 47.05

35.89 15.72 43.74

0.755 0.416 0.393

38.50a 16.28 42.10a

37.47a,b 16.86 44.85b

35.35a,b 16.71 47.09c

34.89b 16.61 47.54c

2.33 0.83 3.52 106.7 1.43 95.9 1.24 4.17

2.20 0.80 3.12 74.5 1.33 83.0 1.21 5.48

0.047 0.016 0.091 8.76 0.255 0.257 0.027 0.211

2.46a 0.85a 3.65a 68.0 1.45a 89.8 1.29a,b 5.84a

2.23a,b 0.82a,b 3.32a,b 91.4 1.39a,b 94.8 1.36a 4.82b

2.18b 0.82a,b 3.19a,b 108.4 1.35a,b 87.8 1.20b,c 4.14b

2.19b 0.76b 3.12b 94.6 1.31b 85.6 1.08c 4.37b

a,b,c Different superscript letters in the same row represent significant differences (p b 0.05). BAH: barley + alfalfa hay; AH: alfalfa hay. OMSF: omental-mesenteric fat, HLL: heart + lung + liver, RR: reticulorumen.

24 h (n = 19)

48 h (n = 18)

SEM

D

F

DxF

1.067 0.589 0.556

0.220 0.003 b0.001

0.046 0.909 b0.027

0.998 0.986 0.571

0.066 0.022 0.128 12.38 0.361 7.90 0.038 0.295

0.056 0.170 0.003 0.012 0.007 0.107 0.469 b0.001

0.008 0.032 0.023 0.143 0.046 0.865 b0.021 0.027

0.962 0.866 0.813 0.507 0.997 0.141 0.793 0.313

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S. Karaca et al. / Meat Science 116 (2016) 67–77

Table 8 Least square means for carcass characteristics of lambs, by diet and fasting period. Diet (D)

Fasting periods (F)

p value

BAH (n = 39)

AH (n = 38)

SEM

0h (n = 20)

12 h (n = 20)

24 h (n = 19)

48 h (n = 18)

SEM

D

Cold carcass, kg Chilling loss, %

17.02 2.80

15.23 3.15

0.410 0.095

15.76 3.23a

16.41 2.72b

16.19 3.14a,b

16.14 2.81a,b

0.579 0.135

0.003 0.012

0.878 0.022

0.986 0.714

Proportion in cold carcass, % Testicles Kidneys KKCF Tail Left half carcass, kg

1.38 0.63 0.94 18.66 6.98

1.40 0.69 0.68 13.40 6.36

0.075 0.014 0.121 2.629 0.155

1.27 0.69 1.00 13.97 6.53

1.45 0.66 0.71 20.91 6.79

1.47 0.64 0.76 14.41 6.76

1.37 0.66 0.78 14.83 6.62

0.106 0.021 0.172 3.715 0.219

0.787 0.002 0.128 0.162 0.006

0.527 0.426 0.641 0.499 0.810

0.939 0.988 0.303 0.269 0.934

Carcass joints in left half carcass, % Fore leg (FL) 19.27 Hind leg (HL) 36.59 Neck (N) 9.57 Flank (F) 11.96 Back-loin (BL) 17.20 Shoulder (S) 5.18

19.73 36.71 9.54 11.56 16.77 5.28

0.172 0.252 0.121 0.195 0.193 0.114

19.82 37.22 8.74b 12.06 16.81 5.27

18.96 36.36 10.08a 12.08 16.75 4.96

19.59 36.27 9.68a 11.69 17.02 5.26

19.62 36.74 9.72a 11.22 17.35 5.42

0.243 0.355 0.171 0.275 0.272 0.161

0.064 0.736 0.884 0.156 0.121 0.509

0.071 0.217 b0.001 0.110 0.421 0.239

0.220 0.093 0.959 0.762 0.056 0.505

By categories 1st quality (BL + HL + S) 2nd quality (FL) 3rd quality (N + F)

58.77 19.73 21.11

0.262 0.172 0.201

59.31a,b 19.82 20.80b

58.08b 18.96 22.16a

58.56a,b 19.59 21.38a,b

59.52a 19.62 20.94b

0.371 0.243 0.285

0.590 0.064 0.146

0.027 0.071 0.005

0.899 0.220 0.711

58.97 19.27 21.53

F

DxF

a,b,c Different superscript letters in the same row represent significant differences (p b 0.05). BAH: barley + alfalfa hay; AH: alfalfa hay. KKCF: kidney knob channel fat.

reported variations in hot carcass weight loss of between 3.5% and 7.9% in sheep fasted for different lengths of time (24–96 h). In the present study, significant increases in dressing percentages were observed in line with decreases in digestive system contents according to fasting period (p b 0.05), whereas head, four feet, skin, heart+lung+liver and rumen weights decreased as a result of decreases in slaughter weights observed in connection with increases in the fasting period (p b 0.05). Ilian et al. (2001) reported significant decreases in liver and various muscle weights as fasting periods increased from 24 h to 72 h and 7 days. These findings indicate that decreases in various organ and other body-part weights as well as rumen content play important roles in the total weight loss observed due to fasting. Liu et al. (2012) also suggested that catabolism and tissue dehydration may play a role in weight-loss resulting from long-term fasting. Percentages of left half-carcass parts found in the present study are consistent with those previously reported for lambs slaughtered at live weights of 35–40 kg (Karaca, 2010; Majdoub-Mathlouthi, Saïd,

Say, & Kraiem, 2013) and were not found to vary significantly according to diet group (Table 8). However, as Table 9 shows, cold-carcass chest widths (CWs), shoulder widths (SWs), buttock depths (BDs) and buttock widths (BWs) varied significantly between diet groups as well as between fasting groups. When compared to AH lambs, BAH lambs also had higher values for carcass and leg compactness, which are criteria related to carcass conformation (Majdoub-Mathlouthi et al., 2013). These findings are in line with previous studies reporting conformation to improve in line with increases in ration energy, as expected (Majdoub-Mathlouthi et al., 2013; Mushi et al., 2009). 3.3. Muscle pH and meat quality Meat color, water-holding capacity, tenderness, shelf life and organoleptic characteristics can be considerably affected by ultimate carcass pH (Gregory, 1998). As stress levels and duration increase, muscle glycogen reserves are depleted, which may result in meat with a high

Table 9 Least square means for cold carcass measurements (cm) and indices of lambs, by diet and fasting period. Diet (D)

Buttock depth (BD) Buttock width (BW) Leg length (LL) Rump width (RW) Chest depth (CD) Chest width (CW) Shoulder width (SW) Int. carcass length (CL) Carcass compactness HCW/L, g/cm Leg compactness BW/LL, g/cm Chest roundness index CW/CD a,b

Fasting periods (F)

p value

BAH (n = 39)

AH (n = 38)

SEM

0h (n = 20)

12 h (n = 20)

24 h (n = 19)

48 h (n = 18)

SEM

D

F

DxF

8.99 7.02 23.49 19.05 27.92 17.01 17.71 62.86 277.8

8.98 6.87 23.67 18.85 27.41 16.56 17.10 63.10 248.4

0.107 0.087 0.174 0.179 0.252 0.159 0.178 0.388 5.426

8.95a,b 6.80a,b 23.60 19.10 27.73 16.35 17.00 63.85 253.9

9.35a 7.25a 23.63 19.05 27.73 16.78 17.45 62.73 268.0

8.97a,b 6.98a,b 23.73 18.96 27.68 16.79 17.38 62.39 266.8

8.66b 6.75b 23.36 18.69 27.53 17.22 17.81 62.94 263.8

0.151 0.123 0.246 0.253 0.356 0.224 0.252 0.549 7.672

0.949 0.237 0.487 0.453 0.162 0.048 0.019 0.671 b0.001

0.021 0.028 0.767 0.682 0.977 0.065 0.170 0.275 0.546

0.732 0.671 0.514 0.832 0.829 0.865 0.600 0.799 0.972

108.8

98.7

2.529

103.0

104.6

103.0

104.4

3.575

0.006

0.981

0.969

0.007

0.438

0.015

0.580

0.61

0.60

0.005

0.59

a

Different superscript letters in the same row represent significant differences (p b 0.05). BAH: barley + alfalfa hay; AH: alfalfa hay.

0.60

a,b

0.60

a,b

0.62

b

S. Karaca et al. / Meat Science 116 (2016) 67–77

ultimate pH. In the present study, an increase in the fasting period resulted in increases in serum cortisol concentrations in the 24 h and 48 h groups, and a positive relationship was detected between blood glucose and pH24 h levels (r = 0.418; p b 0.001). Despite the significant difference between serum cortisol concentrations of lambs in the 0 h (11.04 nmol/L) and 48 h (27.67 nmol/L) groups (p b 0.01), all serum cortisol values were below 42–82 nmol/L, which is considered to be the normal range for sheep (Jackson & Cockcroft, 2002). This indicates that the increases in cortisol occurring with increases in fasting period are not high enough to have a detrimental effect on meat pH. Other studies have also reported differences in lamb plasma cortisol concentrations according to feeding system (Aguayo-Ulloa et al., 2013; Carrasco, Panea, Ripoll, Sanz, & Joy, 2009) and fasting period (Zimerman et al., 2013), but these differences were considered too small to influence the ultimate pH of meat. As Fig. 1 shows, muscle and liver glycogen contents were similar for BAH and AH lambs, whereas increases in fasting period resulted in dramatic reductions in liver glycogen levels, with 95% of glycogen content depleted in the first 12 h of fasting (p b 0.001). In line with this finding, a positive relationship was found between liver glycogen content and total VFA (r = 0.808; p b 0.001). The interaction between diet and fasting groups was not significant. Hepatic glycogen reserves are quite sensitive to fasting, exercise and stress (Jacob, 2003). Compared to liver glycogen, which begins to break down to glucose immediately in order to balance decreases in blood glucose levels (Fisher et al., 2011), glycogen in muscles is only broken down to meet the needs of the muscles themselves (Berg, Tymoczko, & Stryer, 2002). Jacob, Pethick, et al. (2005) reported that the duration of preslaughter fasting did not significantly affect muscle glycogen concentrations unless animals were exposed to intense muscle activity or stress. Other studies (Daly, Gardner, Ferguson, & Thompson, 2006; Edwards & Babiszewski, 2013; Jacob, Pethick, et al., 2005) have similarly reported that muscle glycogen levels did not change significantly in sheep subjected to different pre-slaughter fasting regimens (0–96 h). Muscle glycogen levels have been found to increase in line with increases in the metabolic energy of rations (Immonen et al., 2000; Martin, Gardner, Thompson, & Hopkins, 2004). Immonen et al. (2000) found cattle fed low-energy rations for 17 days before transport to have lower muscle glycogen contents and higher post-transport glycogen loss when compared to cattle fed high-energy rations. Likewise, the ultimate meat pH of lambs fed in extensive conditions has been found to be higher than that of lambs subjected to intensive fattening; some researchers have attributed this difference to differences in muscle glycogen reserves and energy levels in connection with feeding systems (Perlo et al., 2008; Priolo, Micol, Agabriel, Prache, & Dransfield, 2002). By contrast, other studies have reported different feeding systems to have a limited effect on meat pH, water-holding capacity and

73

tenderness in sheep and goats (Aguayo-Ulloa et al., 2013; Kannan et al., 2006; Sanudo, Campo, Olleta, Joy, & Delfa, 2007). Meat quality characteristics are closely associated with post-mortem carcass temperature, glycolysis and decreases in pH (Abdullah & Musallam, 2007; Geesink, Bekhit, & Bickerstaffe, 2000). High-energy rations have been reported to have a positive effect on glycolysis and post-mortem reductions in pH by increasing muscle glycogen reserves and fat thicknesses in sheep and cattle carcasses (Gardner, Daly, Thompson, & Pethick, 2005). Indeed, researchers (Mushi et al., 2009; Safari, Mushi, Mtenga, Kifaro, & Eik, 2009) have indicated postmortem carcass temperatures to decrease more slowly and pH to decrease more rapidly with increases in ration energy. In a study involving a shorter finishing period (4 days), Kannan et al. (2014) found the ultimate pH of lambs and kids fed roughage to be significantly higher when compared to those given concentrate feed. In contrast to these findings, some studies have reported similar post-mortem temperature and ultimate pH for lambs (Majdoub-Mathlouthi et al., 2013), kids (Abdullah & Musallam, 2007) and goats (Kannan et al., 2006) regardless of differences in feed-energy levels. Similarly, as Fig. 2 shows, this study found no significant differences in post-mortem pH between BAH and AH lambs. In terms of fasting period, pH8 h were lower in the 12 h and 24 h groups when compared to the 0 h and 48 h groups (p b 0.05). Although pH24 h was lower in the 24 h group when compared to the other groups (p b 0.001), pH72 h did not vary significantly between the groups (Fig. 2). Moreover, pH24 h and pH72 h values for both the BAH and AH groups and all the fasting groups were within the acceptable range (pH 5.6–5.8) for ovine animal carcasses. These findings are similar to those of previous studies (Daly et al., 2006; Edwards & Babiszewski, 2013; Jacob, 2003; Zimerman et al., 2013) reporting fasting periods of 24–96 h to have limited effect on the ultimate pH of meat. Color is one of the most important characteristics to influence consumer preferences for fresh meat (Priolo, Micol, & Agabriel, 2001). There are many reports showing feeding system to significantly affect meat luminosity (L*) (Minchin et al., 2009; Priolo et al., 2002), with increases in L* attributed to increases in reflectance values due to increases in marbleization resulting from greater fat deposition (Minchin et al., 2009). In the present study, L* values were similar for BAH and AH lambs, despite the significantly higher level of fattening in BAH lambs when compared to AH lambs (Table 10). It is in line with Priolo et al.’s (2001) suggestion that carcass fat deposition has only a limited influence on meat color, given that animals fed on pasture had darker meat color than animals fattened with concentrate feed, despite the higher levels of fat deposition in pastured animals. Abdullah and Musallam (2007) have also reported ration energy levels to have no significant effect on meat L* values.

Fig. 1. Muscle and liver glycogen content of lambs had different diet in 0 h (a) and fasting periods (b). a,b Different superscript letters for the same parameter in the same sub-graph represent significant differences (p b 0.001). BAH: barley + alfalfa hay; AH: alfalfa hay.

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S. Karaca et al. / Meat Science 116 (2016) 67–77

Fig. 2. Changes in post mortem pH and temperature of carcasses for lambs with different diets (a) and fasting periods (b). †p b 0.1; *p b 0.05; **p b 0.01; ***p b 0.001 (indicate the differences between treatments at the same time). BAH: barley + alfalfa hay; AH: alfalfa hay.

In terms of a* value, the present study found a* to be significantly higher in the AH group when compared to the BAH group (p b 0.05) (Table 10). This is in line with Carrasco et al. (2009) reporting a* value to be higher in lambs fattened on pasture in comparison to concentrate feed. Although increases in a* values are generally attributed to increases in muscle activity, age and live weight (Carrasco et al., 2009; Sanudo et al., 2007), given that these characteristics were similar for both diet groups in the present study, the observed differences in a* values can most likely be attributed to differences in the amount of roughage consumed by lambs. As a matter of fact, it was reported that not only the physical activity of animals fed on pasture, but also increasing carotenoid consumption might increase the redness of meat (Carrasco et al., 2009). Pre-slaughter stress factors may also have a significant effect on meat color, with a number of studies reporting meat color to darken in animals as a result of a long fasting period (Fisher et al., 2011; Greenwood, Finn, May, & Nicholls, 2010; Liu et al., 2012). However, other studies have reported pre-slaughter stress resulting from fasting to have limited influence on meat quality in sheep (Daly et al., 2006; Edwards & Babiszewski, 2013; Jacob, 2003; Zimerman et al., 2013) and goat (Zimerman et al., 2011). In the present study, L* values in the 48 h group were significantly lower when compared to groups with shorter fasting times (p b 0.001)(Table 10). There were no significant differences in a* between groups while, 12 h and 24 h groups have the highest *b, C* and h* values. There is no plausible explanation for why fasting affected on b*, C* and h*.

In addition to meat color, water-holding capacity (WHC) and chemical composition may be affected by rations (Guerrero, Valero, Campo, & Sañudo, 2013) and fasting period. The present study found that WHC were better in the BAH than the AH group. These findings are in line with previous studies reporting lambs fattened intensively with concentrate feed to have higher WHC than lambs fattened on pasture (Karaca, 2010; Santos-Silva et al., 2002). Juarez et al. (2009) reported WHC (%) of meat to increase with increases in live weight and fat deposition. Cooking loss (CL) in the present study varied between 29.30% and 32.11% (Table 10), which is within the range for sheep reported by various studies (Ekiz et al., 2009; Perlo et al., 2008). No significant difference was found between the BAH and AH groups in terms of CL. These findings are similar to the results of researchers reporting that feeding system did not have any significant effect on CL (Kannan et al., 2006; Lee, Kouakou, & Kannan, 2008; Madruga et al., 2008). A decline in meat water-holding capacity is known to have a negative effect on juiciness; however, in the sensory panel test, no significant difference was found between diet groups in terms of meat juiciness (Table 12), indicating that the difference was not large enough to be perceived sensorially. WHC has previously been reported to increase in meat with a high ultimate pH in connection with pre-slaughter stress. In the present study, WHC was found to be significantly affected by fasting, with WHC significantly higher in the non-fasted (0 h) group when compared to the fasted groups (12 h, 24 h, 48 h) (p b 0.01); however, CL of lambs in the non-fasting group did not vary significantly when compared to

Table 10 Least square means for meat quality traits of lambs, by diet and fasting period. Diet (D)

pH45 min pH24 h pH45 min–pH24 h L* a* b* C* h* WHC1, % Cooking loss, % WBSF, N

Fasting periods (F)

p

BAH (n = 39)

AH (n = 38)

SEM

0h (n = 20)

12 h (n = 20)

24 h (n = 19)

48 h (n = 18)

SEM

D

F

DxF

6.41 5.70 0.70 38.75 8.31 12.17 14.75 55.63 18.66 30.51 45.70

6.43 5.71 0.71 38.73 8.87 12.46 15.34 54.56 20.55 30.08 43.94

0.029 0.015 0.028 0.347 0.195 0.199 0.231 0.588 0.573 0.373 1.276

6.40 5.73a 0.67 40.78a 8.56 11.70b,c 14.52b 53.89b 16.64b 30.04a,b 42.65

6.41 5.75a 0.66 38.43b,c 8.45 12.77a 15.36a,b 56.59a 20.56a 32.11a 47.76

6.39 5.62b 0.77 39.13a,b 8.78 13.03a 15.73a 56.05a,b 20.20a 29.30b 42.27

6.46 5.73a 0.73 36.62c 8.57 11.76c 14.58a,b 53.85a,b 21.03a 29.72b 46.60

0.041 0.021 0.039 0.490 0.275 0.280 0.325 0.831 0.810 0.521 1.804

0.562 0.591 0.752 0.970 0.044 0.296 0.076 0.200 0.022 0.418 0.336

0.642 b0.001 0.174 b0.001 0.858 0.001 0.026 0.037 0.001 0.008 0.075

0.230 0.932 0.294 0.911 0.870 0.868 0.928 0.708 0.994 0.447 0.391

a,b,c Different superscript letters in the same row mean represent significant differences (p b 0.05). BAH: barley + alfalfa hay; AH: alfalfa hay. 1 Percentage of free water.

S. Karaca et al. / Meat Science 116 (2016) 67–77

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Table 11 Least square means for nutrient contents (%) of lambs, by diet and fasting period. Diet (D)

Moisture Crude protein % of DM Ether extract % of DM Crude ash % of DM

Fasting periods (F)

p value

BAH (n = 39)

AH (n = 38)

SEM

0h (n = 20)

12 h (n = 20)

24 h (n = 19)

48 h (n = 18)

SEM

D

F

DxF

77.27 19.72 86.65 1.91 8.40 1.08 4.76

77.99 19.19 86.97 1.78 8.09 1.02 4.65

0.150 0.156 0.249 0.063 0.246 0.018 0.083

77.86a,b 19.17b,c 86.08 2.15a 9.66a 0.93b 4.19b

78.48a 18.83c 87.32 1.60c 7.43b 1.03b 4.79a

77.51b 19.62a,b 87.22 1.71b,c 7.62b 1.12a 5.01a

76.68c 20.20a 86.63 1.93a,b 8.26a,b 1.12a 4.83a

0.212 0.219 0.351 0.089 0.360 0.028 0.117

0.001 0.020 0.368 0.161 0.400 0.047 0.388

b0.001 b0.001 0.082 b0.001 0.001 b0.001 b0.001

0.968 0.975 0.558 0.554 0.496 0.460 0.349

a,b,c Different superscript letters in the same row represent significant differences (p b 0.05). BAH: barley + alfalfa hay; AH: alfalfa hay.

Table 12 Means for sensory characteristics of lambs, by diet and fasting period. Diet (D)

Tenderness Juiciness Flavor Overall liking SEQ score1

Fasting periods (F)

p value

BAH (n = 39)

AH (n = 38)

SEM

0h (n = 20)

12 h (n = 20)

24 h (n = 19)

48 h (n = 18)

SEM

D

F

DxF

4.51 4.78 5.62 5.51 5.25

5.01 4.80 5.61 5.72 5.44

0.163 0.148 0.119 0.126 0.115

5.19a 5.11 5.86 5.88 5.64

4.75a,b 4.86 5.50 5.51 5.30

4.82a,b 4.80 5.44 5.55 5.28

4.28b 4.40 5.66 5.50 5.19

0.228 0.207 0.166 0.179 0.162

0.101 0.558 0.599 0.279 0.433

0.066 0.586 0.824 0.611 0.356

– – – – –

a,b

Different superscript letters in the same row represent significant differences (p b 0.10). BAH: barley + alfalfa hay; AH: alfalfa hay. 1 SEQ score = juiciness × 0.1 + tenderness × 0.2 + flavor × 0.3 + overall liking × 0.4.

the fasting groups. CL in the 12 h group, however, was significantly higher when compared to the 24 h and 48 h groups (p b 0.001) (Table 10). It is possible that in cases where the effect of pH is limited, fat deposition, chilling and cooking may play a role in meat WHC, which would explain the findings of an earlier study (Madruga et al., 2008) showing differences between the WHC of meats with similar ultimate pHs. Tenderness of meat is a primary consumption characteristic and is affected by numerous pre-and post-slaughter factors. However, this study found neither diet nor fasting period had a significant effect on WBSF. This is in line with numerous studies reporting energy levels (Abdullah & Musallam, 2007; Kannan et al., 2006), feeding systems (Lee et al., 2008; Santos-Silva et al., 2002) and fasting periods (Edwards & Babiszewski, 2013; Liu et al., 2012) had no significant effect on WBSF. As seen in Table 11, meat moisture was significantly higher and protein content significantly lower in the AH group when compared to the BAH group (p b 0.05). Mahgoub et al. (2000) reported higher water as well as higher protein contents and lower fat contents in sheep with lower energy rations when compared to those with higher energy rations. Several other studies (Mushi et al., 2009; Priolo et al., 2002; Safari et al., 2009) have reported increases in meat moisture and decrease in meat fat content in line with decreases in ration energy and concentrate ratios. In the present study, an increase in the fasting period was also found to result in an increase in meat protein and ash content, but a decrease in meat moisture. Results of the sensory panel test are given in Table 12. In line with Jacob, Walker, et al. (2005), diet and fasting groups were found to have similar juiciness, flavor and general liking scores. However, tenderness scores varied significantly between the 0 h and 48 h groups. This may be attributed to a decrease in water content and an increase in perceived tenderness as a result of an increase in the fasting period. Shetaewi and Ross (1991) reported that in general, trained panelists as well as consumers consider meat annoyingly tough when WBSF values exceed 5.5 kg. However, as mentioned above (see Table 10), WBSF values were below 5.0 kg (49.03 N) for all groups in the present study.

4. Conclusion Provision of barley-supplemented roughage for a short time prior to slaughter had limited effect on live weight loss, physiological stress parameters and meat quality characteristics among lambs fasting for periods of up to 48 h prior to slaughter. However, short-term barley supplement promoted daily live weight gain, increased fat deposition and improved carcass conformation. Some physiological stress indicators such as serum cortisol increased in lambs fasted for 24 and 48 h before slaughter. Muscle glycogen and ultimate pH of meat were influenced only to a limited degree. The water-holding capacity of meat was higher in lambs supplemented with barley, and redness (a*) of meat was higher in lambs fed with only alfalfa (p b 0.05). Moreover, as fasting period increased, meat color (L*) became darker and water-holding capacity and water content decreased (p b 0.01). These findings demonstrate lambs to be capable of adapting to long fasting periods if their energy reserves are mobilized so that they do not substantially decrease prior to slaughter. However, since long fasting periods negatively affects certain meat-quality characteristics and increase physiological stress parameters in lambs, fasting periods longer than 24 h are not recommended. Acknowledgments The present study received support from the Yuzuncu Yıl University Scientific Research Project Fund (Project no: 2012-ZF-B015). References Abdullah, A.Y., & Musallam, H. S. (2007). Effect of different levels of energy on carcass composition and meat quality of male black goats kids. Livestock Science, 107(1), 70–80. http://dx.doi.org/10.1016/j.livsci.2006.09.028. Adnoy, T., Haug, A., Sorheim, O., Thomassen, M. S., Varszegi, Z., & Eik, L. O. (2005). Grazing on mountain pastures — Does it affect meat quality in lambs? Livestock Production Science, 94(1–2), 25–31. http://dx.doi.org/10.1016/j.livprodsci.2004.11.026. Aguayo-Ulloa, L. A., Miranda-de la Lama, G. C., Pascual-Alonso, M., Fuchs, K., Olleta, J. L., Campo, M. M., et al. (2013). Effect of feeding regime during finishing on lamb welfare, production performance and meat quality. Small Ruminant Research, 111(1–3), 147–156. http://dx.doi.org/10.1016/j.smallrumres.2012.09.011.

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