You cant go wrong
By Jessica Buss
with a reliable bull
BULL selection can be difficult despite the range of sires available, as Warwickshire Agricultural College farm manager Tom Cox has discovered.
He used a sire widely over the college herd five years ago which resulted in a daughter crop of 30 replacements for the 125-cow dairy herd. But by the time it came to serving the heifers, the bulls proof had dropped. The heifers failed to perform as well as their contemporaries.
Since then ADAS national dairy cattle consultant Helen Woolley has been advising the farm on its breeding policy.
"The decision to use high-index bulls at Warwickshire college has resulted in a dramatic increase in the genetic merit of youngstock," she says. "Last years heifers are outperforming those of previous years." (See graph opposite.)
She advises choosing bulls with a reliability above 70% to minimise risks. "A number of bulls on the market have a low reliability," she says. "There is a good chance that the proof of a low reliability bull will change, but it can go down as well as up.
"If young bulls are used they should be kept to less than 25% of the breeding herd," she adds. Using a team of bulls through the Cogent progeny-testing scheme or MOET Masters ensures only a few daughters from one bull enter the herd.
Although the genetic merit of the national herd is improving, high-production genetics from abroad are still needed, claims Mrs Woolley. ADAS produces a value-for-money list for its customers and only one UK-born and bred bull is listed in the top 30.
She advises selecting bulls initially on the index. But a bull with a high ITEM could have a low milk volume and high % of constituents. This may not suit the needs of a particular herd, so producers should make an initial short-list on ITEM and check the proof in detail before making a final selection. (See box.)
The college herd selection criteria is decided each year. Last year it was a minimum predicted transmitting ability of 900kg of milk and 25kg of protein. This is to meet the farm targets of higher milk yields and proteins to increase milk output profitably from leased quota.
Bulls used had to score positive on foot angle, but this was the only type trait selected for last year. "The fewer traits you select the faster the genetic progress," says Mrs Woolley.
She suggests a budget of £25/straw is enough to meet the herds breeding objectives, although some commercial herds can justify spending up to £40 a straw.
Attention to herd fertility has reduced semen use to 1.8 straws a calf born at the college.
"The amount you have to spend on semen is influenced by fertility status," says Mrs Woolley. "Sensible use of young bull semen can help spread costs."
The final selection of bulls was Bluff for use on heifers and Bluff, Nordkap and Aerostar for use on cows. Mrs Woolley believes using three bulls with reliable figures is acceptable, and two to four bulls is enough for commercial herds.
The top 50 cows in the herd are selected for breeding replacements, with the remainder going to Simmental AI. Initial cow selection is made on genetic merit or PIN value. Then the animals type is checked before it is used for breeding.
Mr Cox aims to continue to get 60% of the yield from forage and yields are forecast to increase to 7500 litres a cow by next autumn.n