Hot topic: how to maximise the heat detection rate in seasonal calving herds
George Ramsbottom of Teagasc summarises some of the key findings from the recent Teagasc/ICBF week of events on the latest research in dairy breeding
The Teagasc and ICBF breeding week ran from March 15-18. During the week we identified the following reproductive targets as being critically important in seasonal calving dairy herds:
■A 90pc 6-week calving rate;
■A 365-day calving interval;
■A planned empty rate of less than 8pc at the end of a 12-week breeding season.
While all of the video releases, podcasts and supporting material is available on the Teagasc and ICBF websites, a sample of some of the content delivered is presented in this article.
HEAT ACTIVITY IN PASTURE BASED DAIRY COWS
Efficient heat detection is fundamental to achieving the reproductive targets outlined above.
A missed heat can cost almost €150 when it occurs during a 12-week breeding season. Failure to correctly identify cows in heat and inseminating them at the incorrect time are major limitations to achieving excellent reproductive performance.
Research conducted by Stephen Moore and colleagues at Moorepark summarising the heat activity of dairy cows at pasture has recently been published.
On average increased activity associated with heat lasted for 17.2 hours, while mounting activity lasted for an average of 8.7 hours. However, there was considerable variation between cows in the duration of both heat activity and standing heat as shown in Figure 1.
The most important message coming from the study was that the duration of standing heat was for less than eight hours in 55pc of the cows.
The implication of this finding is that the use of heat detection aids is absolutely critical to achieving a high heat detection rate.
Old research from the 1990s supports this finding in that compared to three times daily heat detection, the use of an aid increased heat detection rate by 20pc.
Stephen said that a variety of heat detection aids are available for use on dairy cows and maiden heifers. When used correctly, all are effective at increasing heat detection rate.
■Tai• paint should be applied as a narrow strip (50mm wide and 200mm long) and topped up at least once weekly. The biggest mistake that’s made with it is that it’s not topped up regularly enough. ■Scratch cards are well proven particularly with maiden heifers. Cards can be lost if excess winter hair at the tail head is not removed before sticking them on. ■E•ectro■ic activity monitors can be used to maintain the efficiency while reducing the labour required in heat detection.
Irrespective of the aids used, Stephen recommended that farmers should start heat detection three to four weeks before breeding actually begins to establish which cows are cycling and which will require further intervention.
SPRING 2021 BREEDING GUIDELINES
Andrew Cromie, ICBF, detailed the guidelines that have been developed by a DAFM-led dairy calf welfare working group, consisting of key industry stakeholders. These are: ■K■ow your herd’s strengths and weaknesses. Refer to your ICBF Herd EBI Scorecard to help establish what these are.
■Se•ect a team of high EBI AI bulls when breeding your dairy herd replacements. For a typical 100 cow dairy herd, a minimum of eight bulls should be used on your herd, with no more than 15pc mating’s to any one bull.
■Target high EBI females (typically maiden heifers, first and second calvers) to breed your next generation of dairy herd replacements. Lower EBI cows should be bred to beef AI from the start of the breeding season.
■Use the Dairy Beef Index to select suitable beef AI sires for your dairy herd. A team of bulls should be selected that suits the various dams in your herd (i.e., maiden heifers, young cows and mature cows) and the number of these that are selected for beef AI. Bulls with higher beef merit figures should be selected for older animals. Consider the use of vasectomised bulls in conjunction with beef AI as an alternative to beef stock bulls. Avoid using dairy ‘sweeper’ bulls.
■Use the ICBF HerdPlus Sire Advice Tool to help manage your breeding programme and simplify the process of sire selection. It will allocate your bulls to cows based on their strengths and weaknesses, as well as manage inbreeding.
Cows designated for beef AI should be flagged to ensure that only the best animals are used to breed dairy herd replacements. For more information on this tool contact ICBF HerdPlus, your Teagasc advisor and/or your AI company.
■If using sexed semen, only use high EBI sires and ensure that all sexed-semen inseminations occur early in the breeding season. Any inseminations with Jersey or crossbred bulls should be conducted using sexed semen only.
Pay careful attention to straw handling and AI procedures, as sexed semen contains fewer sperm, and these sperm are more fragile after the sorting process.
MANAGING LATE CALVING COWS
Stuart Childs, Teagasc, addressed the issue of managing late calving cows. On average almost 390,000 dairy cows (or more than one quarter of spring calving Irish dairy cows) calved after April 1st in 2019 and 2020 with almost as many calving in May and June as in April.
Because the reproductive cycle of the cow requires a period of rest and recovery after calving before she can go back in calf again, she requires a rest period of approximately 30 days after calving before commencing a treatment programme.
Cows calving within four weeks of the start of the breeding season warrant special attention to help ensure that they go back in calf. Stuart detailed two approaches that can be taken to shorten the interval between calving and breeding in such cows.
The Once-A-Day (OAD) milking approach This approach is typically used on low SCC, late calving or thin (BCS <2.5) cows. It works on the principle that once a day milking reverses the trend towards body condition loss in early lactation because of the reduced milk yield (typically 30pc lower volume) compared to cows milked twice daily.
Milking them once a day from calving speeds up the resumption of their reproductive cycle and such cows also have a higher conception rate to first service. Using the once a day milking approach, cows are typically AI’d within 50 days of calving. The loss in milk yield for a cow milked once a day for 40 to 60 days is approximately €55-75. Speaking at one of the breeding week webinars, Kerry dairy farmer William Dennehy strongly advocated this approach saying that he uses it every year on the few cows that calve on his farm after the first of April.