Farm Ireland

Friday 21 October 2016

Rapid grass growth can increase stressors for dairy cows

Dan Ryan

Published 29/06/2016 | 02:30

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Current grass growth rates are excellent, which will optimise the opportunity for cost efficient milk production.

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However, rapid uptake of nitrogen with its consequential impact as a stressor on dairy cows will contribute to increased embryonic death. Caution should be exercised now with regard to your breeding programme.

Cows bred from now onwards will calve in April. Your primary focus has to be on minimising stress for the cow and maximising the opportunity for repeat breeders and late calvers to establish pregnancy over the next four weeks.

Forget about plans to reduce costs that ultimately depress competence of the immune system of your herd. Instead in an era of low milk prices, focus on maximising gain from beef calves sold from the dairy herd.

Significant stressors at farm level include mastitis, poor body condition and locomotion scores, infectious diseases such as stomach and liver fluke, IBR, Johne's and neospora.

Keep a close eye on your bulk milk collection figures for butterfat and protein percentages.

Poor percentages and differentials are an indication of background stress. We currently have many reported cases where butterfats have fallen below 3.5pc and proteins below 3.3pc.

You have to avoid the cumulative stress load that results in the immune system being compromised. With defence systems down, infectious diseases become clinical with a knock-on risk of embryonic death and poor reproductive performance.

In an effort to reduce the cost of production farmers are being advised to remove vaccination programmes for leptospiroisis, IBR and BVD. You should only consider removing vaccination programmes if you have a herd which is healthy.

This latter descriptor of herd status is difficult to achieve where herd size increases beyond 80 cows.

Cows have to walk further on the grazing platform, competition for grazed grass increases stress on the younger cows in the herd.

Grazing out paddocks with an emphasis on zero topping forces cows to graze too close to faeces. This in turn will increase the risk of Johne's infection.

Pregnancy scans currently reveal too many herds with cows below target body condition scores, along with clinical evidence of IBR, liver and stomach fluke.


This is evidence that correct management regimes have not been put in place during the dry cow period for stomach and liver fluke.

There is a carry-over effect in these herds whereby body condition scores decrease and secondary diseases such as IBR and Johne's become clinical.

Your herd is now in the final furlong of the breeding programme that will establish which cows stay or exit the milking herd for next year. Do not use the excuse that you have plenty of replacements. Replacements have a defined cost and do not leave a profit in their first lactation on a par with mature cows. You also reduce the opportunity for sale of beef calves from the herd by increasing replacement rate.

A pregnancy scan now will establish your six week calving rate for next spring. A lot of emphasis is placed on this figure with regard to optimisation of farm profit. However, there is an even greater opportunity to use this scan data to address cows with reproductive disorders and embryonic mortality.

In a bid to increase the value of calf sales from the dairy herd, there has been a significant increase in the use of beef sires both from AI and natural service. Natural service sires have been introduced at an earlier stage in breeding programmes this year. With an increased workload and farmers reluctant to spend money on extra bulls, the risk of injuries to bulls has increased. An injury to a stock bull not alone reduces his libido to breed cows, but also interferes with spermatogenesis resulting in either a sub-fertile or an infertile bull.

If there is more than three visible cows bulling on a daily basis relative to each bull available, it would be advisable to breed these cows on the following day with a beef sire from AI.

There is a logic to using beef sires to add value to the beef calf in the sale ring.

However, your priority at this stage of the breeding programme has to be an easy calving for your late calvers next year, which will optimise their chance of a pregnancy in a restricted window of opportunity next year.

Dr Dan Ryan is a bovine reproductive physiologist and can be contacted at

Dr. Dan Ryan is a Bovine Reproductive Physiologist and can be contacted at www.

Indo Farming


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