Friday, March 29, 2024

In-calf focus for profit

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When farmers increase their six-week in-calf rate they increase their overall milk production, get more artificial breeding (AB) replacements, have fewer empties, and have a decreased mating period.
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Dr Tom Brownlie, a veterinarian and research scientist with LIC, carried out a national herd fertility study, supported by Cognosco, and his findings showed that the six-week in-calf rate had the greatest effect on profit – more so than focusing on submission rate, conception rate, or empties.

His comprehensive study considered the risk factors for herd fertility and how to improve it by identifying key areas that he discussed with farmers through a series of seminars.

Herds that achieved more than 70% for the six-week in-calf rate –the top quartile of herds – gained a week more at peak production a cow than the herds achieving the average 66% and 15 more days a cow than the lower quartile of the herds, which had a six-week in-calf rate lower than 61%. For a 500-cow herd, that added up to 3500 additional days at peak lactation for the herds in the top quartile compared with those in the lowest.

Those top quartile herds also averaged 10% more AB calves compared with the average herds and 20% more than the bottom quartile herds. Using those figures for a 500-cow herd, that's 50 more AB calves and about 25 more heifer replacements in the higher six-week in-calf herds than those at the other end of the scale.

There were about half the empty rates in a top quartile herd with highest six-week in-calf rates than those in the bottom quartile. In the 500-cow herd, that equated to 15 fewer empty cows.

Achieving good six-week in-calf rates was a race against time though, Brownlie said, with cows pregnant for 282 days of the year, then needing a recovery period post-calving before mating. The average interval between calving and mating start date of cows in the study was 63 days.

“There's a lot she has to fit in, in a very short amount of time,” he told farmers at the Murchison seminar recently.

“Biology means she will need 42 days recovering from calving – start to get some feed in and condition improve. Then she starts to ovulate.”

The study assessed herds from four major dairy regions around the country and results showed there was no difference in six-week in-calf success rates between regions, with good performers and poor performers in each. Likewise, herd size made no difference.

When questioned about the effect of management such as owner/operator versus sharemilkers, Brownlie said a small sample of lower-order sharemilkers had good results, but the number was too small to judge. Likewise, there was insufficient data to assess the effect of once-a-day milkings.

The study did confirm information already accepted by the industry, such as that crossbred cows had better productive performance, Jerseys had better submission rates than Friesians, and Friesians in turn had better conception rates than Jerseys. The in-calf rate declined after five years, while late calvers were harder to get in-calf.

“Each week they don't get in-calf, the probability of getting back in-calf drops. We do need early-calving cows and we need to improve both submission rates and conception rates to improve it. And lose those late-calving animals.

“When buying animals in, check they are in-calf in the first six weeks. Know when they conceived.”

Young animals were a big issue for cow fertility. Data showed they would get in-calf easier and then back in-calf quickly if they achieved their target liveweight at 22 months.

The top quartile of herds in the study calved 80% of their heifers in the first three weeks of calving and produced approximately 80kg milksolids more in their first lactation than those heifers in the bottom quartile.

For all the herds, condition and nutrition played a big part in fertility. As part of his study, Brownlie body condition scored (BCS) a random 70 cows from each of the herds which added up to 40,000 cows. The average herd in the study had a pre-calving BCS of 4.6 – less than DairyNZ's in-calf target of five, or 5.5 for two- and three-year animals. Data showed a pre-calving BCS of five or 5.5 had the highest likelihood of being in-calf by week six. However, herd averages had limited use and Brownlie said the greater concern was the proportion of the herd not meeting the BCS target.

Heat detection was a job not done well on dairy farms, Brownlie said. There was an obvious drop in heat detection after the first three-week period that he believed was caused by ‘heat detection fatigue’ and the lower proportion of cows left to cycle.

“Plan for it. Have the right people on the job with the right training and tools. Be tail-painting five weeks out for pre-submission rates and identify non-cycling cows early.”

Non -cyclers were more likely to be young, Friesian, late calvers, have a BSC closer to three than five, or have had calving difficulty. Only 55% of cows that had calving difficulties got back in-calf within the six-week in-calf period.

“If you do decide to treat them, treat them early. They're never going to be early calving cows.”

Good record-keeping about sick animals, a good understanding of the vaccination policy, ensuring staff knew what to look for, and using advisors all helped to get cows back in calf quicker, he said.

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