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Importance of heat detection to tighten up calving blocks

PRE-MATING planning is key to achieving good non-return rates, with failure to meet first service targets highlighted as one of the major reasons for long calving intervals and high culling rates.

A team approach is needed for optimum cow fertility
A team approach is needed for optimum cow fertility

Block calving herds calving 90 per cent of cows in the first six weeks of calving outperform those with longer calving periods, according to expert research.


At a recent AHDB Dairy breeding management meeting, veterinary expert Kate Burnby said effective heat detection and observation was essential to achieving good submission rates when looking to meet first service targets.


She said: “It is a good idea to sit down at the start of a season, particularly if there are new members in a team, and go back to basics on the visual signs of heat detection.


“A lot of the time it is taken for granted everyone knows what a cow in heat is going to look like.


“Block calving herds should focus on the KPI’s of a six-week in-calf rate and 12-week empty rate when measuring performance.


“To maximise in-calf rates, herds need to focus on achieving high heat detection rates – aiming to serve 90 per cent of the herd within the first three-week cycle of mating.”


When striving to achieve tight calving periods as part of a block calving system, Ms Burnby said specific record-keeping and planning was important when considering heat detection management, alongside nutritional and other management considerations.


Getting the most from bulls

  • Buy around two to three months before putting with cows
  • Get a fertility test done on bulls around six weeks before using. Allow time to source a replacement in case there are any problems
  • Run odd numbers of bulls in teams. Of a similar age and breed from a group which has already been kept together
  • Generally bulls less than two should be run at a ratio of one to 15 cows and after that one to 30. If running two bulls, rotating every 24 hours will give each a chance to get back to full working capacity to reduce risk of drop in sperm counts

“I would encourage those who have not block calved before, or anyone looking to tighten their calving block, to experiment with a three-week breeding calendar,” she said.


“It is a good visual tool to see when cows are likely to be bulling and can also be used to quickly
assess heat detection rates being observed. These work best in herds of 250-300 cows and under.”


She added other chalk and tail paint were also valuable tools, alongside good husbandry practice.

“Chalk works well in systems where cows do not mount easily or often, as it rubs off more readily,” she said. “For cows which express heat well, paint works better.”


To improve first service rates, Ms Burnby said bull selection was also important to ensure easy calving and short recovery periods.


“Considering easy calving bulls across the herd can have a big impact on conception rates” she added.

“Short, easy calvings will improve recovery time and mean cows are more likely to get back in calf in fewer oestrus cycles.


“Pregnancy also needs to be achieved within three or four oestrus cycles on block systems, so later calving cows will have fewer opportunities to get back in calf.


“Some units run successfully without using bulls, but for those which are, considering bull maintenance and ratios is important to get maximum return on an investment.


“There are a surprising number of bulls meant to be working and not doing anything, which is especially hard to spot when a team of bulls is being used.


“If one in a team of two is infertile but happens to be the dominant bull, he may stop the fertile one serving cows.”

Healthy and well-grown cows and heifers

FOR block calving herds it is vital to get as many cows and heifers submitted and conceiving as possible, even with the season’s difficult weather conditions.


Joyce Voogt, LIC international technical manager, speaking at a recent event organised by the company, advised producers to focus on cow health and condition, as well as heifer growth rate targets, to help achieve the best results.


She said: “Getting body condition score (BCS) right at calving is crucial to getting cows back in calf. The aim is a score of 3.3 on the UK scale.


“Too fat, and cows are more susceptible to ketosis and metabolic disease, which will impact fertility. Too thin and they tend to be later cycling post-calving. There is a strong correlation between getting the right BCS and days to first cycle.”


She said it was important cows did not lose too much BCS between calving and mating, ideally no more than 0.3, but it needs to be kept under 0.6.


“When cows are mated, it is important they are not in negative energy balance,” she added. “Heifers on a rising plane of nutrition, gaining weight, have improved fertility. For cows this is not essential, but it is important their BCS does not drop.”


When it comes to heifers Ms Voogt advised youngstock needed to be well grown in order to reach liveweight (LW) targets for mating at 15 months, or 60 per cent of mature weight.


“This process begins with an easy birth and enough high-quality colostrum to give calves the best start, before focusing on nutrition and good monitoring of growth rates throughout the rearing period,” she said.


“Heifers need to be 90 per cent of mature liveweight (MLW) when they calve down, ideally between 22 and 24 months of age, in order to optimise their lifetime performance and put them on track fertility-wise for their second mating.”

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