Effect of stoned olive cake on milk yield and composition of dairy cows

Studies carried out with olive cake (OC) as feed generally addressed to small ruminants, and the knowledge including OC to the diets of high productivity dairy cows is scarce. This study investigated the effect of partly substituting roughages or concentrate with stoned olive cake (SOC) on milk yield and composition of Holstein dairy cows. Twelve high yielding dairy cows were equally assigned to one of two dietary treatments either containing SOC or not (C, control), and were fed ad libitum for 22 d. Pellet form of SOC substituted 8% of roughage and 5% of concentrate in the total mixed ration (TMR) of cows. The cows that were fed SOC TMR consumed (P<0.01) more dry matter than those were fed C TMR (C, 28.1; SOC, 32.8 kg/d). The SOC had no (P>0.05) effect on either the milk (C, 47.5; SOC, 50.9 kg/d) or 3.5% fat corrected milk yield (FCM: C, 45.7; SOC, 44.5 kg/d). The cows in the C group appeared to have higher (P = 0.08) milk fat content, but daily milk fat production did not differ (P>0.05) between groups. Feeding SOC decreased (P<0.05) the feed efficiency when expressed as either milk or 3.5% FCM yield per dry matter intake. It is concluded that SOC could safely substitute concentrate rather than roughage components of the TMRs of high yielding dairy cows.