Massive genetic improvement within Greenmount’s Blackface flock

By Dr Steven Johnston, Senior Beef and Sheep Technologist, Greenmount Campus

The two heft approach to Blackface breeding at Greenmount’s Hill farm has been replaced with a five family breeding policy. By using the best performing homebred rams from each of the families the average carcase weight of entire male lambs improved by 1.4kg from 2004 to 2007. In addition the proportion of lambs grading R2, R3 and U3 markedly improved from 48percent to 87percent (see Table 1).

Table 1. Average Hill-2 index and slaughter data for entire male lambs

	Male Lambs	Signet Sheepbreeder Hill-2 Index*	Carcase Weight (kg)	%Male Lambs Grading R2,R3 and U3
2004	Entire	120	18.1	48
2005	Entire	145	18.7	53
2006	Entire	183	19.2	81
2007	Entire	203	19.5	87
2008	Castrate	226	18.4	78

*The Signet Sheepbreeder Hill-2 Index combines information on maternal, litter size, growth and carcase traits into a single figure using appropriate economic weightings.

The genetic improvement achieved in growth rate and grading encouraged the decision to castrate lambs in 2008 and reduce cost.

Castration resulted in the male lambs achieving market acceptable weights and fat covers from a predominantly grass based diet, reducing concentrate fed and thereby cost.

Table 2. The observed growth and carcase traits of the male lambs in Greenmount’s Blackface flock in 2004 and 2008.

	Sexual Status	Carcase Weight (kg)	Carcase Weight Range (kg)	%Grading R2,R3 and U3	Average Slaughter Date	Days to Slaughter
2004	Entire	18.1	10.6- 25.2	48	2/12/04	237
2008	Castrate	18.4	15.6- 23.1	78	7/11/08	214

Combining the physical performance information detailed in Table 2 with economic data it can be determined that the five years of cumulative genetic improvement which has occurred in Greenmount’s Blackface flock has delivered a benefit of £5.17 per male lamb.

0.3kg additional carcase weight @ £2.88 = £0.86
30 percent more lambs grading R and better 0.3 X 12p X 18.4 = £0.66
23 days less feed (3kg silage @2.5p/kg, 0.4kg conc.
@ 21p/kg = 16p/day X 23 days = £3.65

Total Benefit /lamb= £5.17

In this flock of 360 ewes which weaned 429 lambs in 2009 it is estimated that the grading, growth rate improvement and saving in feed cost in male lambs alone increased flock Gross Margin by over £1100.

In addition to improving growth and carcase traits the five family breeding policy has highlighted the importance of maternal traits to economic performance.

One family, capable of producing and rearing a higher number of lambs was identified. The improved productivity of this family resulted in an increase in income per ewe to the ram of £7.69. This improvement in financial terms was worth more than 16 times the output observed from improving conformation. This highlights the importance of basing selection decisions on recorded information.

Summary

Develop a breeding policy to minimise inbreeding and the need to purchase rams
Identify strengths and weaknesses within the flock
Select rams with the genes needed to complement the ewe flock by using performance information.

For further information on sheep production CAFRE have produced four new technical notes:

1. Ewe management – Pre-mating and early and mid-pregnancy

2. Ewe management – Late pregnancy and early lactation

3. Easier-care sheep production

4. Breeding ewe replacements

Contact CAFRE, Beef and Sheep Advisers for a copy or alternatively they can be downloaded from the website www.ruralni.gov.uk

Steven Johnston and Willie Warwick (Farm Manager) with one of the Blackface rams used within the five family breeding policy at Greenmount Hill farm.