Improved beef quality by better utilization of pasture and optimized carcass handling

I dette prosjektet har vi studert hvordan ulike beiteforhold påvirker kjøttkvalitet og tilvektsthastighet for storfe. Kviger og kastrater gikk på kulturbeite og gjødslet beite, mens oksene ble foret i fjøs. Som forventet hadde oksene høyere tilvekst enn de to andre gruppene, mens det var minimal vektforskjell mellom kvigene og kastratene. Det var unormalt mye nedbør i beitesesongen, som muligens påvirktet tilveksthastighetene, men resultatene viste ingen signifikant forskjell mellom beitegruppene. Seks ulike muskler fra hvert dyr ble tatt ut etter slakting. Det var forventet at kvigene og kastratene skulle ha vesentlig bedre mørhetsnivå sammenlignet med oksene, men det var bare en av de 6 musklene hvor oksene var seigere enn kvigene. Aktivitet av flere naturlige mørningsenzymer har blitt undersøkt i de utvalgte musklene. Calpain bidrar sterkt til å forbedre spisekvaliteten, men også metalloproteaser har en viktig funksjon, spesielt når det gjelder nedbryting av bindevevsstruktur i musklene. I denne studien var Infraspinatus den møreste muskelen til tross for at den hadde lavest aktivitet for begge disse proteasegruppene. Alle de utvalgte musklene hadde bedre, eller likt mørhetsnivå som ytrefilet, som igjen betyr at musklene har potensial som biff.

The main objective for this project is to improve the eating quality of beef produced in Norway. At the moment there is a decrease in domestic beef production which means Norway has to import beef. By nature our country has large areas of natural land of low alternative value which can be utilized by ruminants to produce meat. Bulls, which dominate beef production today, are not allowed to utilize pasture while steers and heifers are well adapted to grass in these areas. A main objective for this project is to compare meat quality (tenderness) for steers and heifers which have utilized pasture with bulls raised traditionally indoors. Although bulls have better growth performance than steers and heifers, the meat seems to be tougher. Today the loin muscles are highly priced in the retail market while muscles from chuck and round obtain lower prices although they seem to be more tender. A sub-goal will be to up-grade these tender muscles. Proteomics will be applied to study degradation of structural protein s from muscles located in chuck and round. So far the majority of proteomic studies have focused on enzymes from loin muscles, less attention have been paid to other muscles. However, more studies are needed to learn which proteins are affected during ten derisation. Another main objective for this project is to make economic models which estimates cost-benefit for different beef production systems. If carcasses from steers and heifers have a higher proportion of tender muscles than bulls these carcasses s hould get a corresponding increase in retail price. However, it still remains unknown whether this value-addition compensates for the increase in production cost. Hopefully this project will show that steers and heifers, which utilize pasture, can be an i mportant source of high quality tender beef.