22 November 1996


By Jessica Buss

WHEN farm manager Vic Boysey decided that increased yields were the future for the 170-cow dairy unit at Upton Farm, Banbury, the herds PIN was £5 – that was in 1992.

Now, four years later, the most recent calves born averaged £85 PIN, this years calf crop £70 PIN, and the milking herd has an average PIN of £26.

Genetic progress was achieved using embryo transfer, top quality semen and the purchase of 10 cows, Mr Boysey told visitors at a Genus run ET open day.

Initial success with purchased embryos was poor resulting in few calves on the ground. Flushing programmes were begun on-farm and over the past four years 10 cows have been bought to introduce new cow families to the herd. Flushing these cows has increased their influence in the herd.

Mr Boysey maintains that ET is an investment and can be costly. He estimates the cost of each heifer calf at £800, with the farms average success rate at 0.75 heifers for each flush.

Flushes average four embryos for the 29 carried out over three years, though there is a wide variation between cows, and the pregnancy rate achieved is 41%. But more recently pregnancy rates have increased to 46% – closer to that achieved by AI, he says.

According to Genus ET vet Peter Townley successful flushing re-quires care of the donors nutrition for six months before the flush to ensure a good number of follicles develop. That means careful nutrition must start three months before they calve.

"Donor cows should be dried off in the correct body condition and fed long fibre to keep the rumen well developed," he says. They should be introduced to the post-calving ration two weeks before calving and after calving fed well to avoid weight loss. The post-calving diet should comprise 17.5 to 18% crude protein, for excess protein can be detrimental to fertility.

Minerals are also important. He advises offering chelated mineral sources and trace elements for the whole of the calving period.

This advice should also be followed for embryo recipient cows, he adds.

Maiden heifer donors and recipients should be fed to grow at 0.75kg a day from puberty at 10 months of age. Then one month before flushing or transferring embryos Mr Townley advises stepping up feeding for a growth rate of 0.85%.

"Keep this diet the same for six weeks after embryo transfer," he says. "Good results are achieved from heifers fed straw and 3kg of a 22% crude protein concentrate."

Mr Townley believes silage-based diets can be harder to manage and on high quality grass silage heifers can grow too fast and get too fit.

"Regular ET users really begin to get to grips with the management of donors and recipients to achieve their potential," he says. Embryos a flush and pregnancy rates, therefore, often improve as management improves.n

ETvet Peter Townley says successful flushing requires care of the donors nutrition for six months before the flush to ensure plenty of follicles develop.