AUTUMN CALVING
To autumn calve, or not By Cheyenne Nicholson
Dairy Trust Taranaki are gearing up to reveal the results of a trial comparing transitioning from one calving system to another.
D
airy Trust Taranaki will be revealing preliminary results of their autumn calving trial this month at an open day on their Kavanagh farm in Hawera. Operations manager Debbie McCallum says that the trial aims to identify implications of the transition period required to change the season of calving and compare an autumn calving system with a spring calving system. Many farmers are opting for wholeherd autumn calving or split calving to mitigate the risks of summer dry and capitalise on the greater winter pasture growth the region has been seeing for the past decade. “Autumn calving has become popular along coastal Taranaki,” McCallum says. “Summer dry is common. More often than not there’s a big soil moisture deficit. Low pasture growth rates in summer and autumn along, with increased pasture growth rates over winter make it a viable option for coastal farmers. “There’s a bit of a lifestyle perk about it, too. Rather than battle through milking in summer, many would rather milk in winter and have a break over the January through March period.” Calving in March and April when the weather is better is appealing for many with calf rearing easier in the dry, warmer weather. In 2017 the original 600-cow herd residing at Kavanagh farm were split into an official autumn-calving herd and a spring-calving herd. The herd was randomised on age, BW, PW, liveweight, previous production and calving date to create two equal herds for ease of data comparison. The farm was also split into two farmlets, randomised into location, soil fertility and distance from the shed. The first 18 months of the trial was dedicated to the new autumn-calving herd transition from spring to autumn calving. The first spring the autumn cows
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Debbie McCallum from the Dairy Trust Taranaki and Jake Jarman on one of the Trust farms where he had been researching the transition process to autumn calving for his thesis.
weren’t mated, but instead entered into an extended lactation through to the following winter and mated in winter 2018. During this extended lactation, the autumn-calving cows averaged 661kg MS/cow and 488 days in milk. Some cows competed 577 days in milk, and 50% of the herd were still milking at drying off. During the first autumn-calving lactation, the milk production curve flattened out and while they didn’t peak as high as the spring herd, they displayed greater persistence. “One of the biggest drawbacks is that loss of production in that second lactation. Per cow, production was negatively affected. This would be something for farmers to consider as it’s a financial cost,” she says. This hard-and-fast transition process comes with pros and cons. The two notable implications are
increased BCS and a subsequently higher risk of metabolic issues and higher reproductive performance for a season. By doing a whole-herd transition utilising an extended lactation, farmers can maintain their existing herd. On the downside, there will likely be cows who are unsuited for extended lactations, which can lead to cows gaining aboveoptimal body condition score post 300 days in-milk. “We found a fairly notable increase in BCS in the transition cows. They packed on the pounds. They’re being fed as a normal-producing in-milk cow, but their actual milk production drops so that extra energy goes into body fat,” she says. “We had some big variations in the herd, which indicates that we had some cows who were very well suited to extended lactations as their production was fairly good, and others who weren’t.”
DAIRY FARMER
February 2021
