Question

Spring calving herd. Using DIY AI for many years  Calving extending into May every year with some cows coming 3/4 times ,as a result ,too late to go in calf. Using tail paint + vec bull. Would I be better to use fr bulls to tighten up calving? Would bulls put more cows in calf at end of 12 week than AI?

Reply

I am going to answer your question in two ways, firstly looking at your problem in a simplistic manner and secondly considering it as the more complicated multifactorial problem it most likely is.

Simplistically, the answer to your question is YES, a bull or bulls will generally have a higher conception rate and will get a slightly higher percentage of cows in-calf, and slightly earlier in-calf, than the use of AI alone. Of course, this is very much dependent on the bull having good fertility and having the correct number of cows per bull so that over-working is not an issue.

The advantages of the bull are as follows:

(a) the bull continuously secretes male pheramones which stimulate ovarian activity in the cows and helps bring them into oestrus/heat earlier post-calving

(b) the bull will obviously detect all cows that are in heat and so there are no problems with missed heats (in your case with the use of the vasectomised bull and tail-painting, it is likely that your submission rate is also very good)

(c) the bull will stay with a cow and inseminate her on two or more occasions during her period of heat – therefore there will not be the same issues with the timing of insemination (with AI, if insemination is carried out too early or too late, this can lead to failure of conception)

(d) fresh semen from a fertile bull has a much greater longevity and a much higher sperm concentration than frozen semen used in AI

All of these reasons add together to mean that a bull or bulls used at the end of the breeding season or throughout the breeding season are more likely to get cows back in-calf easier and earlier and to bring on late calvers so that they are back cycling and ready for insemination 4 to 6 weeks post-calving.

It is my opinion from reading your question that it is very likely that there are a number of possible issues affecting your fertility each year. The issues of particular relevance that commonly affect fertility on many Irish farms include:

(i) energy balance and metabolic disease in the periparturient period;

(ii) diet and nutrition during the breeding season;

(iii) submission rates;

(iv) correct timing and administration of AI;

(v) management of the late-calving cows and

(vi) infectious causes of infertility. I will deal with these five issues separately.

i) Energy Balance and Metabolic Disease in the Periparturient period:

The periparturient period refers to the period from 3 weeks prior to calving to 6 weeks post-calving. The most important thing that any dairy farmer could concentrate on during the year is the minimisation of negative energy balance and metabolic disease (eg milk fever, retained placenta, metritis, displaced abomasum, ketosis) during this period. Negative energy balance (failure of energy intake to match energy demands from maintenance, milk production and growth in young heifers) will normally manifest as a loss of body condition during this period. All cows are in negative energy balance (NEB) after calving, especially in the first 2 weeks, and therefore some weight loss is acceptable (it is acceptable to lose up to but not more than a half of one body condition score (BCS) by 6 weeks post-calving). Where nutritional management is deficient, however, cows may be in significant NEB before calving and as a result will develop more metabolic disease and undergo a much more profound drop in feed intake post-calving resulting in serious weight loss and the loss of >0.5 BCS by 6 weeks post-calving. It has been conclusively proven that if cows lose 1 BCS or more post-calving (most common in fat cows eg dropping from a BCS of 3.75/4.0 at calving to BCS of 2.5 by 6 weeks post-calving), this leads to a severe drop in conception rates and in fact first service conception rates can be as low as 17 to 38%. Body condition scoring during the dry period and post-calving is critical so that problems can be detected and prevented.

(ii) Diet and Nutrition during the Breeding Season:

It is well known that lack of energy intake post-calving as well as during the breeding season will adversely affect fertility. Dairy cows are genetically programmed to transfer the majority of their energy intake and energy production from fat stores towards milk production primarily. Fertility and other bodily functions will be sacrificed in cases of NEB. NEB has been a significant problem in the last few years with poor grass growth and can most easily be seen by excessive BCS loss and low milk protein %. The other dietary influence that can lead to poor fertility during the breeding season is excessive dietary protein and non-protein nitrogen. Grass is naturally high in nitrogen and protein and, therefore, dairy nuts with >16% crude protein are not necessary. Excess protein must be excreted from the cow’s body which costs energy and may in fact exacerbate a NEB problem. In many herds mineral deficiencies can have a significant adverse affect on fertility. The main deficiencies of significance include copper, selenium and iodine deficiency. I would recommend that you get your vet to check mineral status prior to the breeding season each year and to supplement accordingly. It is also very important to feed a good dry cow mineral.

(iii) Submission Rates:

The submission rate refers to the amount of cows that were in heat that were actually detected by the farmer and presented for AI. In your case, with the use of tail-painting and a vasectomised bull, I would expect that your submission rates would have been good over the last few years.

(iv) Correct Timing and Administration of AI:

As a DIY AI technician, I am sure that you are very aware of the importance of proper storing and thawing of AI straws, as well as proper AI technique so as to increase the chances of conception. I would recommend that you attend a refresher course if it has been a long time since your initial training. The other important factor of course is the timing of AI. In general it is best to use the AM-PM rule, ie if the cow is bulling in the morning -AI in the evening and vice versa. In some herds where there are problems with NEB there may be delayed ovulation affecting a number of cows – this will mean that the egg that is ovulated is aged and is meeting sperm that has also been around for quite some time resulting in poor conception rates.

(v) Management of the Late-Calving Cows:

Apart from cows repeating, one of your main problems is that of late-calving cows and the difficulty of getting them back in-calf as early as possible. Certainly, if a high % of cows calve in May or June each year, it will be very difficult to tighten the calving pattern without some culling of these late calving cows and the introduction of early-calving heifers. In general, all cows not seen in heat by 6 weeks post-calving should receive a veterinary examination to check for dirty tracts, ovarian cysts and other reasons for anoestrus. Late calving cows and cows that had a difficult calving or retained placenta are most critical. In terms of the late calving cows, I would recommend that they are examined 4 weeks post-calving for evidence of infection (endometritis) and to check for evidence of involution of the uterus and the resumption of ovarian cyclicity. The cows can then be treated with the correct hormonal therapies to bring about oestrus and to maximise conception rates, thereby tightening the calving pattern for the following year. Adherence to this protocol over a 3 year period should ensure a nice tight calving pattern.

(vi) Infectious Causes of Infertility:

The most important infectious causes of infertility and cows repeating include leptospirosis, BVD and the respiratory viruses IBR, RSV and PI3. All cows should be vaccinated against leptospirosis on an annual basis prior to the breeding season (remember leptospirosis is a zoonosis – it can be contracted by humans and can lead to flu-like symptoms and occasionally meningitis). In terms of BVD, I would recommend that you contact your vet so that he/she can check via milk or blood sampling for the presence of persistently infected animals in the herd – these PI animals maintain infection in the herd and must be eliminated as they cannot be cured. Your vet will also be able to advise you on the need or otherwise for vaccination in your herd depending on the findings of the investigations, as well as your status as an open or closed herd. In the past few years in particular, the respiratory viruses IBR, RSV and PI3 have been implicated in fertility problems in herds. They have also led to milk drop syndrome in herds due to cows spiking temperatures and coming down with pneumonia. Often underlying immunosuppression due to NEB, mineral deficiencies or BVD can lead to disease due to these viruses. Recently also, the parasites lungworm, liver fluke and rumen fluke have caused serious disease in many herds and this would have knock-on affects on fertility.

I realise that there is a lot to take in here but I wrote it to emphasise the multifactorial, complicated nature of infertility problems in general. It is likely that you would benefit from a discussion and a fertility investigation from your vet as well as routine fertility visits during the breeding season each year.

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