RELATIONSHIP OF MEAT PRODUCTION CHARACTERISTICS TO STRESS SUSCEPTIBILITY IN YOUNG BULLS

In an attempt figures on the relationship between performance traits s uch as average daily weight gain (ADWG), amount and quality of meat pr oduced and physiological response to exogenic ACTH challenge in the in itial phase of fattening an experiment has been conducted with 25 Blac k and Red Holstein-Friesian bull calves under loose housing conditions using roughage based fattening diets. Basal values were determined in jugular blood samples collected prior to i.m. administration of 60-12 0 IU ACTH (0.313-0.628 IU/kg LW, EXACTHIN inj. Richter G. Vegyeszeti G yar Rt, Budapest). Repeated samples were collected after 2 and 4 h res pectively. Even though positive relationship was found between the cha nge in plasma cortisol level and ADWG in the rearing period (r=0.35) t he correlation coefficient did not seem to reach significant level of probability (P>0.05). Response in cholesterol suggested also close and significant relation (r=0.61, P<0.01) with the growth rate of calves. Out of physiological parameters response of glucose to ACTH challenge correlated significantly with the ADWG in fattening (r=0.60, P<0.01). The same connection was found for AWG per day (r=0.53, P<0.01). Findi ngs reveal closer connection of growth performance to the response of cortisol and/or cholesterol at young age being changed for that of glu cose later on In terms of meat production traits both daily carcass ga in and lean production were found to show positive relationship with t he response to ACTH challenge characterised by the change of cholester ol (r=0.52, P<0.01, r=0.38, P<0.01, resp.). As far as the carcass comp osition is concerned negative and significant associations were establ ished between the fat ratio and glucose, or the percentage of bone and cholesterol (r=-0.38, P<0.05 and r=-0.70, P<0.001, resp.). Close and positive relationship was established between the cholesterol response and muscle eye area (r=0.73, P<0.001). In meat quality traits moderat e or close and significant correlation were calculated between the ult imate pH of longissimus dorsi (LD) and longus colli (LC) muscles and c hange of plasma free fatty acids or glucose levels, as well as the ult imate pH of LD and semimembranosus (SM) muscles and the response in pl asma cholesterol (r=0.38, P<0.05 and r=0.45, P<0.05 as well as r=0.65, P<0.001 and r=0.59, P<0.001, resp.). Negative and significant relatio nship was present between drip loss and plasma free fatty acids or cho lesterol level only in LD muscle (r=-0.38, P<0.05 and r=-0.42, P<0.05, resp.). Red colour correlated positively and significantly with gluco se in LD and LC muscles (r=0.39, P<0.05 and r=0.45, P<0.05, resp.), as well as the yellow one and plasma glucose in LD (r=0.63, P<0.001). Da rkness proved to be positively associated with plasma cholesterol in L D (r=0.48, P<0.05) and with the response of glucose in LC (r=0.52, P<0 .05).