DHI Notes...

May 07| Bennet Cassell

State DHI averages for important management areas in April 2007

Management area	April 2007	Change from last year
Rolling herd average milk	21592	-115 lbs.
Peak yield in heifers	74	0 lbs.
Days to first breeding	94	-2 days
Days open	162	0 days
Net Merit of proven service sires	$310	*
Herd turnover less dairy sales (%)	29%	-1%
Monthly average SCS	3.0	-0.1
Feed cost per cwt. (milking cows)	$5.54	$0.44
Milk blend price	$15.80	$0.451

*Net Merit changed in August 2006 and averages are not comparable.

The May 2007 bull proofs have been out for a few weeks now, but many producers probably aren’t aware that those proofs came from an “all breed” comparison. After all, the proofs look much like they always have. However, the calculations were made without regard to the breed of the cows involved. Jerseys (and cows of other breeds) were compared to Ayrshires, Holsteins, crossbreds – whatever cow stood next to them in the barn. Crossbred and purebred cows were used, as long as identification met the USDA standards. The proofs were first calculated using a single genetic base, but converted to individual breed bases for publication. The Virginia Tech herd received the first USDA genetic evaluations on the cows in our crossbreeding project in our last PCDART “download” following the May DHI test. We have both HJ and JH crosses and they aren’t evaluated the same, though they share the same breed composition. Crossbred cows sired by Holstein bulls are compared to the Holstein base, while cows sired by Jersey bulls are compared to the Jersey base. I compared PTA’s on eight JH and six HJ cows now in second lactation. PTA’s for milk on the JH cows ranged from +2109 to +2957 lbs. The HJ cows ranged from -1657 to +43 lbs. JH cows have much higher proofs for milk, but aren’t really that different genetically from their HJ herd mates.They are compared to a Jersey base, and are superior, genetically, in milk yield to that base because they have 50% Holstein genes for milk. The HJ animals, on the other hand, don’t compete genetically with the Holstein base for milk, as only one cow, the animal with the +43 lb. PTA, was better (barely) than the Holstein base. These cows have proofs for fat, somatic cell score, productive life, and pregnancy rate as well, and different breed bases are used for those traits, too. If your herd includes crossbred cows, they have genetic evaluations in the system if the cows are properly identified and sired by a purebred bull. If your herd is a mix of purebreds, say Holsteins and Jerseys, there may be changes in PTA’s on those purebreds because the contemporary groups now include cows of the “other” breed. The all breed animal model makes better use of available information than the single breed system it replaced and gives producers genetic evaluations of any properly identified crossbred cows they may be milking.

Bennet Cassell
Genetics and Management