INFLUENCE OF MILKING FREQUENCY AND STAGE OF LACTATION ON COMPOSITION AND YIELD

Cheddar cheese was made from milk collected from two groups of cows mi lked either two or three times daily during early, mid, and late lacta tion. Milk from cows in late lactation had lower casein as a percentag e of true protein and a higher acid degree value than did milk from co ws in early lactation. Milk from cows milked three times daily had low er concentrations of milk fat and casein and higher acid degree values than did milk from cows milked twice daily, and thus this milk would be expected to result in decreased cheese yield. Cheese composition wa s not affected by milking frequency. Stage of lactation effects on che ese composition were confined to differences in salt content and a tre nd for higher moisture in cheese made from milk of cows in late lactat ion. Stage of lactation influenced the pH and degradation of alpha(s), -casein, in cheese during aging. Fat and protein losses in whey at dra ining were higher for milk from cows in late lactation than from milk from cows in early lactation. The typical differences in fatty acid co mposition of milk from cows in early lactation that cause lower meltin g point may have caused higher fat loss in press whey. Fat loss in whe y at draining was higher in cheese made from milk from cows milked thr ee times daily than in cheese made from milk from cows milked twice da ily, but the protein loss was not influenced. The ADV of milk was posi tively correlated to the fat loss in whey. Lower recoveries of fat and protein in cheese from milk of cows in late lactation were observed a nd may cause small but economically important decreases in cheese yiel d. Low SCC of milk from cows in late lactation may have minimized the changes in cheese composition and yield from stage of lactation.