Performance of late maturing beef x dairy cattle finished on grass silage plus concentrate or all-concentrate diets

Crossbred progeny of Simmental (S), Belgian Blue (B) and Piemontese (P) sires out of Holstein-Friesian dams were used in two experiments. Experiment 1 involved 90 entire males (30 per sire breed) and Experiment 2 used 90 heifers (30 per sire breed). In each experiment animals were assigned from within breed type to one of three rations: 1) concentrate ad libitum (C), 2) grass silage ad libitum supplemented with 3.0 kg concentrate per head daily (S3) and 3) grass silage ad libitum with a variable level of concentrate (SV; 3 rising to 5 kg/day in Experiment 1, 0 rising to 3 kg/day in Experiment 2). The comparisons were from approximately 4.5 months of age to slaughter at 13 to 16 months of age. Animals were selected individually for slaughter, when judged to be at similar levels of fatness. In Experiment 1 the progeny of S sires had the highest rate of daily live-weight gain (1.38, 1.29 and 1.31, s.e.d. 0.032 kg for S, B and P progeny, respectively). Increasing concentrate level from 3.0 to 5.0 kg / head daily (SV) increased live-weight gain from 1.24 to 1.31 (s.e.d. 0.032) kg/day, but the highest rate of gain (1.43 kg) was achieved on C. Days on experiment were 293, 328 and 312 (s.e.d. 13.1) for C, S3 and SV, respectively. Cold carcass weights of bulls ranged from 327 and 335 kg. For heifers (Experiment 2) daily rates of live-weight gain were similar for progeny of S and B sires, but P progeny had a lower rate of gain (0.99, 1.00 and 0.91, s.e.d. 0.026 kg for S, B and P progeny, respectively). Days on experiment were 252, 304 and 355 (s.e.d. 10.3) for treatments C, S3 and SV, respectively; corresponding daily gains were 1.12, 0.97 and 0.83 (s.e.d. 0.026) kg. Cold carcass weights of heifers ranged from 229 and 242 kg. There was no ration x breed interaction in either experiment. It is concluded that across both genders mean growth rate was in the order S > B > P.