Higher protein rations proven to increase finishing time and slaughter weights.
Harper Adams University research suggests feeding bulls a 14 per cent crude protein (CP) ration, compared to 12 per cent CP, could be more profitable.
The trial paper states the current recommendation for CP content of cereal-based rations for bulls from three-seven months old is 140g CP/kg (14 per cent), saying it can be reduced to 12 per cent through to slaughter for Holstein bulls.
The study was carried out last year at the university, involving 36 British Blue cross Holstein bulls weighing about 320kg at seven months old.
|12% crude protein||14% crude protein|
|Daily liveweight gain (kg)||1.33||1.42|
|Slaughter weight (kg)||587||596|
|Carcase weight (kg)||320.7||328.2|
|Feed conversion rate (kg feed: kg liveweight gain)||6.24||5.82|
It assessed measures of performance, including financial effects of the two rations, along with feed intakes and conversion rates through to slaughter.
It is suggested feeding a 14 per cent CP ration generates a higher gross margin per animal of £335, compared to £296 for those on the 12 per cent CP diet.
The group of bulls on the higher CP ration also took six fewer days to reach the point of slaughter.
Feed intakes were down by 60kg, but daily liveweight gains increased from 1.33kg to 1.42kg, and carcase weights increased by 7.5kg, making the feed conversion rates more favourable.
Carcase characteristics nor liver damage scores were affected by the protein content of the feed. But bulls fed higher levels of protein were numerically recorded to have lower liver damage scores.
Carcase values increased by £43 and, although ration costs increased by £13 per tonne, when feeding 14 per cent CP, margin over feed increased by £39 per bull.
Feed conversion ratios seem relatively high compared to the targeted 5:1 for cereal fed continental cross Holstein bulls, but the trial did not include the period of growth from 110kg to 320kg.
12 per cent CP
Ad-libitum (140g CP/kg DM) concentrates based on:
14 per cent CP
Ad-libitum (163g CP/kg DM) concentrates based on: