Much of the strong demand for SGL semen is a direct result of excellent technological progress in genetics over the past five years.
Since 2000, reduction in gestation length is an area LIC has, on behalf of the industry, specifically targeted for improvement but, in the past five years, that focus has intensified as progress was starting to be of real benefit on-farm.
"A few years ago farmers could expect to condense their calving by up to six days through use of short gestation length bulls," says Ariane Bailey, LIC genetics business manager.
"This was recognised by a small number of farmers, who bought short gestation length semen for AB, largely to gain days in milk.
"But recent advances mean farmers can now shorten their gestation interval by up to 10 days with targeted use of SGL semen.
"And days in milk is not necessarily the only motivating factor nowadays. Many farmers are using SGL semen as a way of offsetting the no-induction rules, while others are wanting to reduce the pressure, and reliance on, natural mating bulls."
Others are cleverly using it as a means to reduce empty rates, by adding extra weeks of AI to their mating plan.
Bull acquisition manager Malcolm Ellis says a four-week AB programme on a 500-cow farm would typically result in about 213 cows still to be bred on the day the bulls went out, meaning the bulls have to service an average of 10.15 cows a day (as shown in Table 1).
"Even with a bull-to-cow ratio of 1:25 cows, the demand on bulls from that kind of cycling activity could easily be described as excessive."
Ellis said an expected drop-off in bull performance, because of such heavy demand, "could quite conceivably" account for a 20 per cent reduction in conception rate.
"I would argue that the pressure put on the bulls is the biggest individual contributing factor (of many) to today's unacceptable empty rates on New Zealand dairy farms."
A total of 70 empty cows was a distinct possibly by the end of mating, giving an all too common empty rate of 14 per cent, he said.
By comparison, with AI lasting seven weeks, the number of cows the bulls had to service could fall to as low as 4.2 cows per day.
The principle of restarting AB for a 10-day period in week 11 would allow a bonus 11 late pregnancies without extending the following season's calving spread and reducing the final empty rate to just 4.6 per cent.
"To me, that model is savvy use of a variety of tools -- excellent replacement AB semen, natural mating bulls, and SGL semen."
