Use of grass and red clover silage mixtures for milk production and whole-body N partitioning by dairy cows

Summary in the original language of the document

Twenty-four multiparous Holstein-Friesian dairy cows in mid lactation were used in a 44 Latin square changeover experiment with four 4-week periods to investigate the effect of altering the ratios of red clover (RC) and ryegrass silage (GS) in the forage component of their diet. Ratios (in the dry matter (DM)) were: R0, 0 RC:1 GS; R34, 0.34 RC:0.66 GS; R66, 0.66 RC:0.34 GS; R100, RC 1:0 GS. All cows received ad libitum access to their allocated forage with 4 kg of a standard concentrate per day. Results are presented in order of R0, R34, R66 and R100 respectively. Feed DM intakes (16.7, 17.8, 18.3, 19.0 kg d-1, s.e.d. 0.24, Plin<0.001) and milk yields (25.2, 26.1, 26.5, 26.1 kg d-1, s.e.d. 0.47, Plin<0.05, Pquad<0.05) increased as the proportion of RC in the forage increased. Nitrogen (N) intake and excretion of N in urine and faeces increased (P<0.01) with increasing proportion of RC in the diet, but milk N secretion as a proportion of diet N intake, decreased (P<0.01). It is concluded that the best balance of feed intakes, milk yields and efficiency of utilisation of dietary N was achieved when cows were offered a diet with RC silage as 0.66 of the forage.