EFFECTS OF CALCIUM SALT SUPPLEMENTATION ON DAIRY-COW PERFORMANCES IN EARLY LACTATION - INFLUENCE OF THE NATURE OF CONCENTRATES

Two feeding trials were carried out on dairy cows for the first 12 wee ks of lactation. Diets were based on grass silage and ensiled beet pul ps and distinguished by the nature of concentrates: rich in starch (S) , starch + lipids (SL), and fibre + lipids (FL1) for trial 1; fibre (F ) and fibre + lipids (FL2) in trial 2. The lipid supplement used was c alcium salts of palm oil fatty acids. Lipid-supplemented diets contain ed ca 6% fatty acids in dry matter. Results were analysed for the firs t 6 weeks of lactation (period 1) then for the following 6 weeks (peri od 2). Whatever the basal diet, calcium salt supply did not modify mil k yield (30.7 and 29.6 kg on average for trials 1 and 2, respectively) . In trial 1, lipid supply did not modify protein content during weeks 1-6 but decreased it during weeks 7-12 (31.5, 32.1 and 31.4 g/kg duri ng weeks 1-6, 28.8, 27.2 and 26.4 g/kg during weeks 7-12 for diets S, SL and FL1, respectively). Although non-significant, the same trends w ere observed in trial 2 (31.4 and 30.7 g/kg during weeks 1-6, 29.4 and 27.5 g/kg during weeks 7-12 for diets F and FL2, respectively). In tr ial 1, during weeks 7-12, lactose content was lower for diet FL1 than for diet SL (48.0 vs 49.4 g/kg). For the 2 trials and the 2 periods, b utterfat content did not vary (45.2, 47.4, 45.2, 44.6, 47.0 g/kg durin g weeks 1-6, 40.5, 40.4, 38.2, 38.1, 39.0 g/kg during weeks 7-12 for d iets S, SL, FL1, F and FL2, respectively). Lipid supply decreased the proportion of short- and medium-chain fatty acids (6-14 carbons) in bo th trials and both periods, increased C16:0 in both trials during week s 1-6 only, and did not modify C18:0 and increased C18:1 during the 2 periods in trial 1 and during weeks 7-12 in trial 2. No difference in proportion of these fatty acids was observed between diets SL and FL1.