Quality nutrition and good heat detection are at the heart of getting the most from sexed semen. Aly Balsom reports.
Dairy producers often report mixed results from using sexed semen, and Ayrshire farmer Robert Sloan is no exception. However, years of experience have enabled him to fine tune his system and get the most from artificial insemination.
Optimising heat detection rates, nutrition and cow health has helped him achieve 70%-plus conception rates to first service in all maiden heifers served to sexed semen – a figure that will help the farm expand cow numbers from 160 to 200 pedigree Holsteins in the next two years.
Although producing quality replacements is one of the drivers for using sexed semen on maiden heifers at Darnlaw Farm, Auchinleck, Mr Sloan sees health and production as one of the main benefits in these first calvers.
“A neighbour worked out that heifers that had heifer calves averaged 32 litres a day over their first lactation and the heifers that had bulls averaged 28 litres a day. It would be interesting to see the knock-on effect this also had on longevity and lifetime yield.”
According to Mr Sloan, who farms in partnership with his parents Bryce and Anne, nutrition is one of the most important factors influencing conception rates to sexed semen.
“Heifers are fed solely silage or grass in the summer between nine and 13.5 months, although we feed 50% first cut and 50% second cut silage through this stage and until PD+. We think this may be one of the most important factors as many farmers tend to feed poorer quality silages to youngstock.”
Heifers are vaccinated at 12 months for BVD and leptosporosis to have them covered in time for service. They are then given a copper and iodine bolus at 13.5 months and a concentrate is introduced at this stage to put them on a rising plane of nutrition until service at 15 months.
“We tend not to serve heifers during May and June as the protein rush from the grass upsets fertility,” explains Mr Sloan.
Heifers are grazed next to the steading on fields of first cut aftermath which are not given any more nitrogen and stock are allowed to come in for concentrates from July onwards when they start serving again.
The decision to use sexed semen varies according to fertility status and the natural dips that occur at certain points of the year. Mr Sloan explains they tend to see good results until mid-September, when the goodness goes out of the grass.”Fertility tends to take a dip at this stage, so we usually switch back to conventional semen,” he says.
The influence of diet and weather on conception rates to sexed semen was also marked two years ago when cattle were housed earlier. “We saw really good results from November onwards as they were on a well-balanced diet quicker.
“However, last year the weather was good and the heifers stayed out longer. As a result there were more repeats until January and conception to first service dropped to about 30-40%. After that they settled well. The cold weather last winter was also an added stress that doesn’t suit sexed semen.”
Automated heat detection for maiden heifers has also formed part of an overall strategy to use sexed semen effectively. Heatime was introduced in September 2009 after being installed with the cows in 2008 and has proved a massive help in timing artificial insemination.
“It is so accurate with timings, it was probably after it was installed we started using sexed semen on all maiden heifers,” he explains.
“In the summer, the heifers come in from outside and under the scanner to get concentrates, which is a massive aid in heat detection. With the best will in the world, you just can’t manually observe your maiden heifers enough for heat at this time of the year. It’s certainly not the answer to successful use of sexed semen but it definitely helps.”
According to Mr Sloan, conception rates started to get better when they started to treat heifers in the same way to embryo recipients and use Heatime. Before this, conception to first service sat at about 20-30%.
“The care and attention you have to observe when trying to get an ET pregnancy is similar to that of using sexed semen,” he says.
Mr Sloan emphasises that bull selection is crucial when choosing sexed semen.
“There is a tendency for AI companies to put their second-tier bulls into their sexing programmes. We wouldn’t tend to pick a bull unless we would also pick it when selecting conventional semen.”
Because cows are yielding 10,300 litres a cow a year, Mr Sloan believes they are under too much pressure to achieve desirable conception rates with sexed semen. “Everything needs to be spot on for sexed semen. If cows weren’t being pushed so hard we might try sexed semen, so we may consider using it when we move over to robotic milking from twice a day.