Comparing Bulls Finished on Grass With Concentrates to Indoor Intensive Bull Finishing12 May 2015
Finishing late-maturing, spring born bulls on grazing after winter can reduce production costs but intensive feeding is required.
Food and Agriculture Development Board (Teagasc) specialists in Ireland have scrutinised finishing bulls on concentrate rations in the early grazing season by comparing it to indoor concentrate diets.
Teagasc writes that here may be scope to finish late-maturing breed autumn-born bulls at the same age, but off high nutritive value ‘spring grass’, as they are more ‘mature’ at turnout, and thus should have a greater tendency to lay down fat compared with their springborn counterparts.
The objective of this study was to determine the effects of concentrate supplementation level in the first part of the grazing season (89 days) on growth and carcass characteristics of late-maturing breed autumn-born suckler bulls compared with a high concentrate indoor finishing system.
Eighty Limousin and Charolais sired bulls (mean initial weight 554kg) were assigned to one of four treatments: 1. grass only (G0); 2. grass plus 25 per centdaily dry matter intake (DMI) offered as concentrates (3kg fresh weight) (G25); 3. grass plus 50 per cent DMI offered as concentrates (6kg fresh weight) (G50); and, 4. indoor ad libitum concentrates (ALC) with grass silage to appetite.
Grazing treatments were turned out to pasture on April 7, 2014, and were rotationally grazed in paddock systems. Average pre- and post-grazing sward heights were 11.8 and 4.8cm, respectively.
Animals offered ALC had a greater daily live weight gain (1.83kg), carcass weight (406kg) and carcass fat score (8.2/~3=) than the grazing groups.
Daily live weight gain was significantly lower for G0 (0.97kg) versus G50 (1.22kg), with G25 (1.07kg) being intermediate.
Carcass weight was 20kg heavier (387kg) for G50 than G0 and G25 (367kg). Carcass fat scores (scale 1-15) for G0, G25 and G50 were 5.0 (~2=), 5.6 (~2=/2+) and 5.4 (~2=/2+), respectively.
Supplementation reduced grass intake for G25 and G50 by 0.67 and 0.94kg DM per kg DM concentrate offered, respectively. Supplementation with 3kg concentrates daily during the first half of the grazing season had little effect on animal performance.
Increasing concentrate level to 6kg daily increased carcass weight, but may not be economical. With average fat scores of 5.0 to 5.6 (2=/2+), the grazing treatments struggled to achieve an adequate carcass finish.