LONG-TERM EFFECTS OF CONCENTRATE LEVEL IN DAIRY-COWS

Three experiments were carried out to study the long-term effects of four combinations of HIGH and LOW concentrate supplementation during the first and second lactation of 72 cows of the Norwegian Red breed: HIGH-HIGH (HH); HIGH-LOW (HL); LOW-HIGH (LH) and LOW--LOW (LL). Basal diets were 0-2 kg hay per cow daily and grass silage ad libitum. Compared with HIGH level supplementation, the LOW level cows consumed 0.4 kg DM more forage in the first lactation and 0.4-1.0 kg DM in the second lactation. Milk yield was lower, respectively 2.5 kg and 1.9 kg 4% FCM (fat-corrected milk) daily, between HIGH and LOW in the first and second lactation, with significant cumulative and residual effects from the first to the second lactation. The difference in daily yield was 3.1 kg 4% FCM between HH and LL vs. 1.8 kg between HH and HL. During weeks 1-4 and 5-14 of the second lactation the average daily production was 2.0 and 1.6 kg higher for HH and HL as compared to LH and LL. Milk protein percentage in the second lactation was negatively affected (p < 0.05) by LOW supplementation during the first lactation. The highest feed efficiency (kg 4% FCM per FEm) was obtained for LOW concentrate during the first lactation. For both lactations, including the dry period and corrections for body weight changes, efficiency was highest for the cows on HIGH supplementation during the first lactation.