Cogent has been trialling fresh sexed semen on farms to offer herds that can synchronise a large group of maiden heifers and serve on one day. This will suit block calving herds in particular. Independent breeding adviser Kevin Lane reports on the latest trial results.

Farmers are adopting sexed semen in greater numbers, partly due to pressure from milk buyers and retailers to cut the number of surplus dairy bull calves being produced. But some breeders still have reservations about conception rates compared to conventional semen— so Cogent has looked into fresh SexedULTRA 4M semen as an option.

The first batch was produced a year ago in spring 2019 using the same sorting and collection process as semen that would subsequently be frozen.

The bull team is increasing from five last year to ten bulls on offer this spring (see table). Most are Irish bulls with high €EBI and £SCI values that would appeal to a spring block calving herd. The autumn team offer high €EBI and £ACI indexes to ensure that genetic progress is being made with the highest genetic merit animals on the farm—the heifer crop.

Handling fresh semen

The bull stud procedure starts with a morning collection, with straws processed and packed by midday. The storage temperature is critical but with some leeway, ideally being between 15 and 18 degrees Celsius.

The quarter cc straws are usually dispatched during the afternoon, either to the local area Genetics Consultant who will deliver to farm the next morning or sometimes the semen goes straight to the farm. The insulated packing box has a thermometer inside and out with an alert to monitor temperature.

The straws are packed in tubes of 15 straws each inside an insulated pouch and the semen needs to be stored and temperature maintained when it arrives on farm until it is used. While the temperature is important, if it is kept within the correct range it will store for up to 48 hours if necessary, although the sooner it is used the better.

Cogent have around a dozen farms on the trial so far. Breeders who would like to consider using fresh sexed semen would need to give a month or two notice of interest. Cogent recommend its use with a heifer synchronisation plan or on cows showing natural heat (dependent on geographical area) and a minimum use of 50 doses. There is no charge for the carriage of the semen, just the cost of the straw itself.

Devon semen trials

Jack Munday, runs a 250 cow autumn calving herd of mainly Irish Holstein Friesians near Crediton in Devon where he calves within an eight week block. He has around a quarter of the cows bred by Norwegian Reds and sells his milk to Arla, with the herd averaging around 6,600kg at 4.6% fat and 3.6% protein.They used to achieve 9,000 litres from pure Holsteins but Jack switched to crossbreeding around ten years ago to address fertility, milk components and to breed a more robust cow.

He tried frozen sexed semen around six years ago and admits that he didn’t get on very well with it and so returned to conventional semen until autumn 2018 when he tried sexed again using Irish semen from Cogent. He tried 70 doses of frozen sexed on the cows along with some conventional semen and this gave him very good results.

Last autumn he was tempted to try the fresh sexed semen option as he has used a synchronisation programme on his maiden heifers as a matter of management routine. He used a CIDR synch with Receptal and served 63 animals to fresh sexed last November.

The semen was delivered by a Reproductive Specialist who helped him to inseminate the group that same day—loading the AI guns in the manner of a loader at a formal shoot!

This worked well for Jack as his heifers are off site and using fresh semen negates the need to transport a flask to the heifer unit. His conception rate on the heifer group was 63% which was comparable to his 2018 results when he used conventional semen with a CIDR sync programme, the same one he used last year.

Jack waited three or four days after serving the heifers before he put the bulls in to sweep up. But in hindsight he says that this year he will put them in the next day. He also used frozen sexed on the cows including 30 sexed Swedish Red, and has therefore moved from 100% conventional in 2017 to 100% sexed in 2019. Jack commented that although the bull team included just what he needed, he hopes that the number available will increase to offer a broader selection, something that Cogent will respond to as more herds look to the fresh semen option.

He found the whole process very simple, from discussing the plan last August, to placing his order for November delivery and the timing of the sync programme. Jack says he will definitely use fresh sexed semen on his heifers again this coming autumn.

Dorset semen trials

In Dorset George Holmes runs over a thousand cows over three dairy units near Dorchester with a 240 Friesian autumn block calving herd in Frampton, a 320 cow spring calving herd of New Zealand crosses in the same village and 420 autumn calving cows at Poxwell which is contract farmed by George’s son William.

George moved to sexed semen after considering the moral and ethical arguments of sending bull calves to slaughter, looking at the sustainability of his business and the wider dairy industry. This prompted him to sign up to an Arla and Cogent trial looking at the potential role of Sexed ULTRA 4M semen within a sexed and beef strategy. George was keen to use sexed semen in the spring calving herd not only because of the lack of value in the Jersey cross Friesian bull calves but having to deal with the challenges of being locked up with bTB.

George also notes that historically, they have had a high bull to heifer calf ratio at the spring unit. To get his 80 female replacements he would often have 100 to 120 bulls born as well. Therefore sexed semen was an obvious choice to breed just his dairy heifers with the dairy beef calves being reared on farm. Despite some moderate results in the past, with around 33% conception rates in the autumn herd and 40% in the spring herd, albeit on a sample of animals and not the entire herd, George was keen to see how improved sexing techniques would give him better results.

Conception rates are such a key element of block calving herds and a target six week in-calf rate of 75 to 80% seemed unlikely with sexed semen. But with SexedULTRA 4M available, George took the plunge. In 2018 all the heifers from the spring and autumn herds followed a synchronisation programme and were served to sexed semen from Cogent and achieved conception rates of 64% in the autumn herd and 52% in the spring herd. The milking cows were also served to sexed using some basic qualifying criteria with conception rates over 50% for both herds.

These results gave George the confidence to use sexed semen and he then took up the offer to go take part in the Cogent fresh sexed semen trial. Once the bulls had been selected and the synchronisation plan agreed with the farm vet, George received his shipment the night before serving and admits to being a bit nervous about keeping the package at the correct temperature overnight. Serving the next morning, he says it was easy to unpack and load the guns without any thawing, and after the subsequent PD session found that his results mirrored the frozen sexed semen used the previous year. George will continue to use the fresh sexed semen again this year, which he thinks is competitively priced and it ties in nicely with his synchronisation of heifers. And so far the results have been very encouraging.

National trial results

Nationally the trials in the south west, in Scotland and close to Cogent’s base in the north west have indicated that fresh semen is a great option for large herds looking to breed heifers using synchronisation and Cogent are looking to increase the number of herds involved.

The Cogent Spring 2020 bull team with €EBI, £SCI and £ACI values