Breeding Worth (BW) and Breeding Values (BV) are presented as the difference between an animal’s genetic merit and the ‘genetic base cow’.
The previous genetic base was the average of a group of well recorded 2000 born cows.
On 19 June 2016, the genetic base cow, which is the genetic reference point for all dairy cattle in New Zealand, became younger, as we moved from a 2000 to a 2005 born genetic base cow.
The genetic base increased by about $50 causing Breeding Worth (BW) to be scaled-back by an equivalent amount across all animals and herds. This change did not cause any re-ranking among bulls or herds nor was it an indication of a change in the value of an animal.
Every year we see genetic improvement in the national herd; which leads to each group of heifers coming through having a higher BW than those cows before them. A genetic base cow update, usually every five years, prevents the gap between the today’s animals and the genetic base becoming too large, keeping the scale of Breeding Worth relevant.
2005 Born Genetic Base Cow: Characteristics
In June 2016, the genetic base used for calculating Breeding Worth (BW) and breeding values became "the average of a group of well recorded cows born in the year 2005". BW and Breeding Values (BVs) are now expressed relative to this genetic base.
The genetic base consists of 21,585 cows with the following breed breakdown:
Holstein-Friesian (6002 cows; 28% of cows)
Jersey (4462; 21%)
Ayrshire (706; 3%)
HF x J (10,336; 48%)
Other (79; 0.4%)
Breeding Worth Traits Trait Phenotype Previous BV* Protein 174kg 5.12 Fat 218kg 6.08 Volume 4595L 68.21 Liveweight TBC -3.22 Fertility TBC 0.49 Somatic Cell Score 208 0.04 Residual Survival TBC 15.12 Body Condition Score 4.11 0.00 Traits other than Production (TOP) Trait Average TOP score Previous BV* Adaptability 6.12 0.01 Temperament 6.28 0.02 Milking Speed 6.33 0.03 Overall Opinion 6.57 0.04 Stature 5.75 -0.03 Capacity 6.34 0.04 Rump Angle 4.79 -0.02 Rump Width 6.17 0.01 Legs 6.18 0.03 Udder Support 6.02 0.04 Fore Udder 5.7 0.05 Rear Udder 5.76 0.06 Front Teats 4.53 0.03 Rear Teats 5.84 0.03 Udder Overall 5.71 0.08 Dairy Conformation 6.45 0.05 Other Traits Trait Phenotype Previous BV* Gestation Length 281.2 days -0.95
*Previous BVs are calculated using the 2000 born genetic base. These BVs are indicative of the rescaling for each trait. For example, The previous Protein BV of the new genetic base is about 5.12kg. All Protein BVs were rescaled backwards by 5.12kg following the base cow update on June 19.
2000 Born Genetic Base Cow: Characteristics
Previously the genetic base used for calculating Breeding Worth (BW) and breeding values was "the average of all cows born in the year 2000". BW and breeding values were expressed relative to this genetic base.
The 2000 born genetic base consisted of 38,684 cows with the following breed breakdown:
Holstein-Friesian (17,103 cows; 44% of cows)
Jersey (9,739; 25%)
Ayrshire (1,296; 3%)
HF x J (8,563; 22%)
Other (1,983; 5%)
Production levels:Reported as the mixed average of their 270-day lactation yields.
Volume: 4406 litres
Reported as mature liveweight
The average raw TOP scores of the genetic base (2000 born cows) were as follows:
Trait Average TOP score Adaptability 6.04 Temperament 6.20 Milking Speed 6.22 Overall Opinion 6.44 Stature 5.63 Capacity 6.23 Rump Angle 4.87 Rump Width 6.12 Legs 6.19 Udder Support 5.87 Fore Udder 5.66 Rear Udder 5.60 Front Teats 4.43 Rear Teats 5.70 Udder Overall 5.64 Dairy Conformation 6.36