Effect of gender and body condition score on meat quality in Kundi buffalo

Meat is used as a major source of animal protein in the world. Out of the total beef produced in Pakistan 65% comes from buffaloes while the rest is shared by cattle. Majority of buffaloes are slaughtered after they have completed their productive life. Meat obtained from such animals is of compromised quality making it undesirable to the consumers (Naveena et al., 2011). Kundi is a buffalo breed of Pakistan and its meat is preferred over cattle meat in most parts of the country (Bilal et al., 2006). Meat quality attributes such as pH, water holding capacity (WHC), muscle fiber number (MFN) and muscle fiber diameter (MFD) are influenced by gender (Weglarz 2010). Physical characteristics such as weight and maturity levels of the animal being slaughtered affect meat quality (Patten et al., 2008). It has also been reported that the animals with body condition score (BCS) 6 had good carcass quality (Apple et al., 1999).
        
Meat with a pH range of 5.4 to 5.6 has the most desirable properties for table cuts (Young et al., 2004). There is a considerable drop in pH of meat after slaughter. Deviation of pH from normal values indicates stress to animal before slaughter or improper handling of carcass post slaughter (Lapitan et al., 2007). Water holding capacity (WHC) is important financially as meat having low WHC has unattractive appearance that affects consumer acceptance which ultimately leads to loss in sale (Otto et al., 2004). It also influences sensory quality of meat, as high water loss during cooking will make meat less juicy and tougher (Bertram et al., 2000).
        
Muscle fiber number is an important determinant of muscle mass (Velotto et al., 2014) and has importance regarding animal selection for beef production (Dwyer et al., 1994). It is determined prenatally and improvements in MFN are observed when maternal feed is increased during gestation (Musser et al., 2006). The most important organoleptic criteria regarding meat selection for consumers is tenderness as they are ready to pay a higher price for meat if it’s tenderness is ensured (Chambaz et al., 2003). Numerous studies have been conducted on the relationship of tenderness and meatiness with MFD and large differences in longissimus dorsi’s MFD were found in animals of same weight and grade (Swanson et al., 1965). A close relationship exists between MFD and total musculature (An et al., 2010). Muscle mass and growth rates are more closely associated with MFN than with MFD (Miller et al., 1975).
        
Effect of gender on physical attributes of meat has been described in many species, but to the best of our knowledge no data is documented regarding the influence of BCS on such attributes. So it was hypothesized that the physical attributes of meat are affected by gender and BCS in Kundi buffaloes. Therefore the aims of the current study were (i) to investigate the effects of gender and BCS on selected physical attributes of meat in buffalo; (ii) to study variations in physical characteristics among different muscles from same animals.

Sampling and grouping of animals
 
Forth Kundi buffaloes having an age of 28 months were divided into four equal groups. The first group was having male animals with BCS 1-4, the second group had male animals with BCS > 4, third and fourth groups had female animals with BCS 1-4 and female animals with BCS > 4 respectively. Body condition scoring was done using a scale of 1-9 as described by Mokantla et al., (2004). Animals were slaughtered and samples of 3 muscles i-e trapezius cervicalis (TC) (from below the joint between 3^rd and 4^th cervical vertebrae), longissimus dorsi (LD) (above the thoracolumbar joint) and semitendinosus (ST) (from the midpoint i-e between the tuber ischii and tuber calcis) (Sisson and Grossman 1985) were collected 24 hours post mortem. A one centimeter cube part of meat was removed from each sample and fixed in 10% neutral buffered formaldehyde and processed for paraffin sectioning (Kuru et al., 2017). These samples were processed according to the conventional method of hematoxylin and eosin as described by Nagarjuna and Doss (2009) for measuring MFN and MFD.
 
Measurement of pH and WHC
 
pH of the meat was measured as described by Young et al., (2004) by using a digital pH meter (Portable pH meter PH-013 Eutech Instruments Singapore). Three readings from the same sample at the same point were taken and the average of the results was reported as the pH of that sample. The WHC of the meat sample was measured by using Honikel’s gravimetric bag method as described by Joo et al., (1999). The results were indicated in percentage showing the WHC of that sample.
 
Measurement of muscle fiber number and muscle fiber diameter
 
The slides obtained were observed under bright field microscope at 4 X for counting MFN and at 10 X for measuring MFD of that sample. Both the MFN and MFD were calculated by using the Morphometry Program (Progress Capture Pro 2.7.7. Labomed USA). Muscle fiber number was counted in three randomly selected fascicles which were having an almost circular shape. Diameter of each fascicle was measured and divided by two for getting the radius r - D/2 , where D is the diameter (Grossman et al., 1975). The area of the fascicle was measured by using the equation A = pr² (Tilmanet_al1997). Total number of muscle fibers in each fascicle was counted and muscle fibers per unit area were calculated. The average of the results was reported as the MFN per cm² of that sample. Diameter of 5 muscle fibers from 3 fascicles each, of all the samples were measured and average of the results were reported.
 
Statistical analysis
 
Statistical analysis was conducted with SPSS version 20.0. Data was found to be normally distributed after checking with Shapiro-Wilk test. Effect of gender and BCS on the physical attributes of selected skeletal muscles was analyzed with two way analysis of variance. Differences were considered significant at P < 0.05 and were calculated by applying Duncan’s multiple-range test.

Table 1 shows a significant difference for selected skeletal muscles physical properties between male and female animals having BCS 1-4 and BCS > 4. It was observed that pH of TC, LD and ST between male and female animals having BCS 1-4 and BCS > 4 differ significantly, with male animals having higher pH than female animals. A significant difference was seen for pH between male animals with a BCS 1-4 and BCS > 4. Male animals with a BCS > 4 had higher pH values than male animals with BCS 1-4. No significant difference was observed for pH for the three selected muscles among female animals with BCS 1-4 and female animals with BCS > 4 however a significant difference was observed for pH between TC and LD of male animals with BCS > 4 and female animals with BCS 1-4. Moreover a significant interaction was observed for BCS × gender for pH as shown in Table 2. The pH values in our study for male and female buffaloes are higher than those reported by Kandeepan et al., (2009). pH of meat depends upon rate of glycogen breakdown to lactic acid after slaughter, storage conditions and health status of animal at the time of slaughter. Stress to animal before slaughter results in depletion of glycogen reserves that causes a higher pH (Lapitan et al., 2007). pH is influenced by weight of carcass as glycogen level is different for carcasses of different weights (Sanudo et al., 1996) and types of muscle fibers in present in every muscle (Hwang et al., 2004).
 

 

        
It was seen that male animals with BCS 1-4 and BCS > 4 had better WHC than female animals of BCS 1-4 and BCS > 4 respectively. A significant difference was observed for the WHC of TC and LD in male animals with BCS 1-4 and BCS > 4 but no significance for WHC was observed in ST of male animals with BCS 1-4 and BCS > 4 and TC, LD and ST for female animals having BCS 1-4 and BCS > 4. Significance was observed for WHC between TC and ST of male animals with BCS 1-4 and > 4. Similarly a significant difference was observed for TC and ST of female animals with BCS 1-4 and TC and LD of female animals with BCS > 4, with LD having better WHC than TC. Meat quality at commercial level is indicated by its WHC (Hamm 1986). Kandeepan et al., (2009) reported that male buffaloes have better WHC than female buffaloes which is similar to our results. Water is held between myofilaments and is bound to the proteins by electrostatic attraction (Miranda-de la Lama et al., 2009). Difference of WHC between different muscles is due to post mortem degradation of intermediate filament proteins called desmins (Melody et al., 2004).
        
A significant difference was observed for MFD and MFN in TC, LD and ST of male and female animals with BCS 1-4 and BCS > 4. It was found that female animals with BCS 1-4 and BCS > 4 had larger MFD but lower MFN than male animals with BCS 1-4 and BCS > 4 respectively. Similarly male and female animals with BCS 1-4 had larger MFD and greater MFN than male and female animals with BCS > 4. MFD and MFN differed in all the groups for the three selected skeletal muscles, with LD having least MFD and most number of muscle fibers whereas TC had the largest MFD and least MFN. Moreover a significant interaction of gender × muscles and gender × BCS × muscle was seen for MFD whereas a significant interaction of gender × muscle, muscle × BCS, gender × BCS and gender × BCS × muscle was seen for MFN as described in Table 2.
        
Muscle fiber number is determined prenatally and their increase is under the control of testosterone which explains why male animals in our study had more MFN compared to female (Kandeepan et al., 2009). Number and size of muscle fibers is different for different muscles for different mass and size (Naveena et al., 2011). Increase in muscle mass is a result of increased MFD and MFN (Whittemore et al., 2003). Muscle fiber diameter is related with tenderness of meat and a positive correlation exists between MFD and toughness of meat (Arguello et al., 2005). Female buffaloes have larger MFD than male which makes their meat less tender (Kandeepan et al., 2009). Increased MFD of female chicken is reported to be due to increased plasma creatinine kinase activity which indicates stress associated tissue dysfunction. However plasma creatinine kinase activity reflects protein turnover which is related to muscle growth rate (Berri et al., 2007).

It is concluded that physical attributes of meat are affected by gender and BCS. Male buffaloes and buffaloes with BCS > 4 have superior quality meat as compared to female buffaloes and buffaloes with BCS 1-4 respectively. Moreover, different muscles with in the same animal have different physical characteristics.