Effect of crossbreed on the physical meat indicators in Yun-ling Black goats

Twenty castrated male goats each of Yun-ling Black goats (YLB goat), NY(Nubian ♂ × YLB goats♀) hybrid goats and BY(Boer♂× YLB♀) hybrid goats were used to evaluate the effect of crossbreeding on the meat quality in the YLB goats of China. There were no signifi cant difference for tenderness, fl avour and overall acceptability for the three types of goats. The meat from BY hybrid goat had signifi cantly higher (P<0.05) CIE (Commission Internationale de l’Eclairage) L* and a* values of L. dorsi muscle (LD) while the YLB goats had signifi cantly higher (P<0.05) b* value in loin muscle and rump muscle (B. femoris, BF). No signifi cant differences among the breeds were measured for water holding capacity (WHC) of LD muscle. However, WHC of BF muscle in NY hybrid goat was the highest among the breeds (P<0.05). The hybrid goats had higher pH values than YLB goats (P<0.05) in both types muscle at 45 min and 24 h of post-mortem. In contrast, YLB goat had a signifi cantly higher juiciness, cooking rate, shear force value and connective tissue compared to BY and NY hybrid goats (P<0.05) and no signifi cant difference was measured between the two types hybrid goats. The muscle fi bre diameter were signifi cantly higher (P<0.05) in the YLB goats than the hybrid goats both in the two types of muscles and the converse results were observed for the muscle fi bre density (P<0.05) and no signifi cant difference for muscle fi bre characteristics were observed between the hybrid goats.


INTRODUCTION
There is also a worldwide tendency for rapid increase in demand for goat meat (Stankov et al., 2002) due to goats depositing more internal fat and less subcutaneous and intramuscular fat compared with sheep (Kirton, 1988).Therefore, consumers are interested in goat meat as a source of relatively lean meat, especially in developed countries with a high incidence of cardiovascular diseases (Banskalieva et al., 2000).There are many local pure-bred goat breeds in the P.R. China, especially in Yunnan Province.YLB goats are an important, largest goat breed and main distribution in mountain area in the Yunnan Province.The goats are both used for leather and meat and are main husbandry economic income in poor rural area of Yunnan Province.Like other goat breed, YLB goats are well adapted to the harsh environment and limited feed, utilize marginal land and digest feed with high effi ciency to produce high protein products, and are disease resistant (Anonymus, 1999).However, there was very little information on the meat quality for YLB goats.Therefore, the present study is to evaluate effect of crossbreeding on the meat quality in YLB goats.

MATERIAL AND METHODS
Twenty castrated male kids each of YLB goats, NY hybrid goats (Nubian ♂ x YLB goats♀) and BY hybrid goats (Boer♂ x YLB goats♀) were randomly selected at birth with the average birth weight 2.86 kg for YLB goat, 2.95 kg for NY hybrid goats and 3.13 kg for BY hybrid goats.These kids were castrated with elastrators at 2 week of age (TRT) and weaning at the age of 90 days.Three breed groups were fed in nature grazing grass land to 24 months to study effect of crossbreed on the meat quality -physical composition.The goats were slaughtered by stunning electrically prior to exsanguination with the average liveweight at 37.6 kg for YLB goats, 40.0 kg for NY hybrid goats and 42.8 kg for NB hybrid goats.The carcass was eviscerated and the head, feet and tail were removed.Samples of the loin muscle (LD) and the rump muscle (BF) were obtained within 30 min of slaughter for analyses of meat quality.
The procedures described in Anonymus (2000) were used to measure for water holding capacity (WHC), cooking rate, water drip loss and characteristics of muscle fi bres.The pH was measured at 45 min and 24 h after slaughter using a pH meter (Hanna-HI9025, Italy) at the 11 th rib on the exposed surface of the freshly-cut LD and BF muscle.Meat colour was measured at 45 min and 24 h after slaughter for BF muscle and LD muscle on the freshly-cut surface of the 7 th rib.A colorimeter (Model CR-400, Japan) was used and two observers assessed lightness (L*), redness (a*) and yellowness (b*).The tenderness of loin muscle was measured using a tenderness analyser (CLM25 Tenderness PRC).
Data were subjected to variance (ANOVA), using Duncan's post-hoc test (SPSS11.0). 1.There were no signifi cant differences for tenderness, fl avour and overall acceptability for the three types of goats.YLB goat had signifi cantly higher (P<0.05)juiciness, shear force value and connective tissue and lower drip loss (P<0.05)compared to BY and NY hybrid goats.NY hybrid goats had a signifi cantly higher cooking rate (P<0.05)across the breed groups of goats.The meat colour, pH value, water holding capacity and muscle fi bre characteristics are summarised in Table 2.They were measured both in LD and BF muscles.The meat from BY hybrid goat had signifi cantly higher (P<0.05)a* values of LD muscle while the YLB goats had signifi cantly higher (P<0.05)b* value in both types of muscle.The b* value signifi cantly increased and a* signifi cantly decreased in both types of muscle and all breeds with post-mortem ageing (P < 0.05).No signifi cant differences among the breeds were measured for water holding capacity (WHC) of LD muscle.However, WHC of BF muscle in NY hybrid goat was the highest among the breeds (P<0.05).The pH values for YLB goats were lower than the hybrids (P<0.05) in both types muscle at 45 min and 24 h of post-mortem.The muscle fi bre diameter was signifi cantly higher (P<0.05) in the YLB goats than the hybrid goats both in the two types of muscles and the converse results were observed for the muscle fi bre density (P<0.05) and no signifi cant difference for fi bre diameter and density characteristics were observed between the hybrid goats.

DISCUSSION
YLB goat had a signifi cantly higher shear force value and connective tissue compared to BY and NY hybrid goats.The difference in shear force values between the breed groups may be due to the greater connective tissue content (Light et al., 1985).The data from shear force values are consistent with the muscle fi bre characteristics.It has been shown that the muscle fi bre diameter were signifi cantly higher in the YLB goats than the hybrid goats both in the two types of muscles and the converse results were observed for the muscle fi bre density.It has been reported previously that tenderness of beef (Ashmore, 1974) and pork (Sheng and Xu, 1984) improves as the density of muscle fi bres increases.
BY hybrid goats had a signifi cantly lower cooking rate across the breed groups of goats.This data were consistent with WHC.Increased cooking loss percentage is refl ection of the decreased WHC (Kadim et al., 2006) and cooking loss is more dependent on the ultimate pH value (Trout, 1988).
The present study indicated that meat from BY hybrid goat had signifi cantly higher a* values of LD muscle while the YLB goats had signifi cantly higher b* value in both types of muscle.The b* value signifi cantly increased and a* signifi cantly decreased in both types of muscle and all breeds with post-mortem ageing.These results supports the fi ndings that the meat colour was affected more by breed, ageing and ultimate pH (Kadim et al., 2003(Kadim et al., , 2006)).The meat colour from Omani goat breed was lighter and less red than other reported goat breeds thus being similar to lamb meat colour.The difference may be due mainly to the different intramuscular fat content (Kadim et al., 2003).Fat colour became more yellow with increase in age, which is evident from higher subjective scores and b* values (Dhanda et al., 1999).The present data from meat colour are consistence with the meat chemical composition, in which the crude fat content was the highest in YLB goat meat compare with the hybrid goats (Jia et al., 2007).
The data for WHC are in agreement with Han et al. (1996) where they reported that there are no WHC differences among LD muscle.The pH value of muscle is regarded as one of the important parameters affecting meat quality (Dutson, 1983).NY hybrid and BY hybrid goats had higher pH values than the YLB goats in both types muscle at 45 min and 24 h of post-mortem.The present data for pH values were broadly consistent with the meat colorimetric values.The increasing a* value of muscle could due to elevated pH value (Kadim et al., 2003).In the present study, the meat pH value of YLB goat was the lowest between the three breed groups and with the highest WHC.In agreement with the previous reports, that goat meat pH value was related to properties such as better colorimetric values (Simela et al., 2004).

CONCLUSIONS
The crossbreeding signifi cantly improved in shear force value, muscle fi bre characteristics and connective tissue as well.On the other hand, the crossbreeding had negative effect on the meat quality of Yun-ling Black goats, such as change in water holding capacity, meat colour, pH value and drip loss.

Table 1 .
Physical indicators of the loin muscle a,b,c means with different letters in the same row are signifi cantly different, P<0.05

Table 2 .
Physicochemical properties of loin and rump muscle a,b,c means with different letters in the same row are signifi cantly different, P<0.05