Intensively finished bulls fed 14% CP ration left £32 per head better margin than bulls fed at 12% CP

26Feb2016

Evaluation of 12% and 14% crude protein rations for 300kg intensively finished Continental dairy-bred bulls

Simon P. Marsh, Principal Lecturer, Harper Adams University

Animal Science Research Centre - Beef Unit Trial Results – 2015 (a)

Introduction and Objective:

There is increasing concern that the stated energy and protein requirements for beef cattle (AFRC, 1993) are now underestimated for today’s modern high genetic merit beef cattle, especially for young fast growing intensively fed bulls.

The current recommendation for the crude protein (CP) content of cereal based rations for young bulls from 3 to 7 months old is 140g CP/kg (14%) which can then be reduced to 12% through to slaughter for Holstein bulls (EBLEX, 2012, Marsh et al., 2009).

In the study by Marsh et al., (2009) 285kg Holstein bulls were intensively finished on cereal based rations containing 12%, 14% or 16% CP. There was no response to feeding elevated levels of CP. However genetic improvement and sire selection for higher productivity and lean tissue deposition may have substantially increased the protein requirement with Continental bred cattle.

With the increased costs of protein feedstuffs relative to cereals and the requirement to determine the optimum protein content of finishing rations for continental bred beef cattle the objective of this experiment was to evaluate different protein levels for intensively finished Continental cross Holstein bulls from 7 months old to slaughter.

Animals & Timing:

36 Sept-Oct 2014 born British Blue x Holstein bulls weighing approximately 320kg at 7 months old randomized according to live weight to the following treatments:

Comparison:

  • 12% CP Ad libitum 12% CP (140g CP/kg DM) concentrates based on 75% rolled barley, 7.5% soyabean meal, 10% molassed sugar beet feed, 5% molasses and 2.5% minerals. 
  • 14% CP Ad libitum 14% CP (163g CP/kg DM) concentrates based on 70% rolled barley, 12.5% soyabean meal, 10% molassed sugar beet feed, 5% molasses and 2.5% minerals. 

Straw was offered ad lib to both groups of bulls from racks. The 12% and 14% rations were analysed to contain 35.8 and 37.6% starch (as fed).

Discussion & Conclusions: 

  • Overall performance of the bulls was good with the 14% CP fed bulls being slaughtered at 13.5-13.7 months old with carcase weights of 328kg exceeding the EBLEX (2012) targets for intensive cereal beef production. 
  • There was an improvement in DLWG (P=0.097) and carcase gain (P=0.073) with bulls fed the 14% CP ration. 
  • The bulls fed the 14% CP ratrion were sold 6 days earlier. Feed intakes were reduced by 60kg compared to the 12% fed bulls and with an increased DLWG this resulted in an improvement in FCR (kg feed: kg live weight gain) from 6.24 to 5.82. 
  • There were no significant differences in carcase characteristics or liver damage scores. However the bulls fed the 14% CP ration recorded numerically lower liver damage scores. Liver abseesss are associated with acidosis and it must be noted that the 14% CP ration had a relatively lower starch content. 
  • Based on the costs prevailing at the time of the study increasing the CP of the ration to 14% with Continental x dairy-bred bulls increased the carcase value by £43. There was an increase in ration cost of £13/t with the 14% CP ratrion so the margin over feed was increased by £32 per bull. 

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