Picking the perfect bull team

It’s a hard job to pick a bull, or even a team of bulls, that has all of the desirable traits that farmers want. While breeding is subjective, and every farmer has their own preferences for the ideal cow, there are some ground rules or constants that shouldn’t change when breeding cows for Irish conditions.

Fertility

The importance of good fertility cannot be overstated and the impact this will have on milk solids production is massive. This is because cows that calve early in the season will achieve high days in milk and will have high annual production. The opposite is also true; no matter how high a cow’s potential is for milk yield, if she doesn’t calve in time, the end of the season will come too quickly for her to realise that milk solids potential. This is especially true for herds that dry off in November.

Looking at the AI catalogues, there is very little point of difference between young genomic bulls on fertility sub-index. Furthermore, the fertility figure on EBI is probably wrong, as it’s overstated by genomics.

Therefore, I’m not sure how much weight someone should place on a bull with an EBI for fertility of €160, versus a bull with an EBI for fertility of say €130. Back 10 or 15 years ago that €30 difference would have been massive, and would likely have been the difference between choosing a bull and not.

So, while fertility is important, any young bull on the active bull list, or in Gene Ireland, is almost certain to have good fertility and so it is not the differentiation that it once was.

Milk

Production as a trait is a very contentious subject, with a lot of grey areas. I think myself that these grey areas suit the AI companies, because people who have different preferences will buy bulls with different traits.

This kind of ambiguity is a marketeers dream, but farmers need to be rooted in reality when it comes to picking bulls. Firstly, farmers are paid in A+B-C, where A is kilos of protein, B is kilos of fat and C is volume in litres. So the more litres produced, the greater the deduction will be.

When looking at the EBI, the predicted transmitting ability (PTA) for milk in kilos is the volume of milk that bull will pass on in his offspring.

In my view, farmers place way too much emphasis on this when picking bulls and, as a result, pass over really good bulls which may be closer to zero or negative for milk volume.

This doesn’t make sense when one considers that volume is a penalty on the milk payment system. So farmers that place a lot of emphasis on milk volume are breeding for something that they get penalised on.

Furthermore, the base cow on which the index is based on produces 6,044kg of milk annually. So if a herd has a PTA for milk volume of zero, it means it has the genetic potential to deliver 6,044kg of milk.

The question is often asked, what happens if I continue to use bulls with minus for milk, will my herd end up with very little volume? This is often asked in the context of using Jersey bulls. While the PTA for milk volume could be as low as -300kg, if these are being used on cows with say -300kg for milk volume, the resultant offspring will be -600kg for milk volume, but will have a PTA themselves of -300kg, because PTA reflects how much they will pass on.

So a herd with a PTA for milk volume of -300kg, would be expected to deliver 600kg less milk volume than the base cow, which is at 6,044kg, meaning the -300kg herd would deliver just under 5,500kg of milk, all else being equal.

At an extreme level, continuously using bulls with the same -300 for milk volume on cows with -300kg for milk volume won’t result in cows with a PTA for milk any lower than -300kg. In the same way, using bulls that are plus 300kg for milk volume on cows that are also plus 300kg, won’t make their PTA higher than plus 300kg.

Solids

Focusing on milk solids makes far more economic sense than focusing on milk volume. The milk sub-index within EBI is based on milk solids yield at the A+B-C payment system, so a high EBI for milk is the best indicator of a bull with good traits for milk.

However, it’s important to look at where the milk solids are coming from. If it’s largely from increased volume at relatively low percentages of solids, then the costs of making those milk solids will be high as producing volume is very energy intensive for dairy cows.

It could also push herds into a higher nitrates band.

For me, focusing on the percentages of fat and protein is very important, as opposed to just looking at the kilos of fat and protein. It’s important to look at this in the context of the herd the bulls are being used on.

Picking a team of bulls with a PTA for fat and protein percent lower than the herd average means that the fat and protein percent of the offspring will be lower. This means the herd is going backwards for percentages.

Now, it might be that the overall kilos of milk solids from the offspring will be higher, but if the solids are driven by volume and not percentages it’s a very inefficient way of producing extra milk solids, requiring more feed inputs to support the extra volume.

Maintenance/beef

There is an antagonistic relationship between the maintenance and beef sub-index within the EBI. Maintenance is largely related to the size of the cow and so too is beef, although age at slaughter is also a key part of the beef sub-index.

In the main, bulls that are plus €15 for maintenance will very often be -€15 for beef sub-index, so they usually cancel each other out, but that doesn’t mean they are not important. Maintenance is a reflection of cow size, so from a core dairy perspective smaller cows are more efficient, because they require less feed for maintenance compared to larger cows.

The conflict is that when cows are small, the value of their calves can be affected because the small carcase size follows through to their progeny. The only way of overcoming that, is to use high beef value beef bulls on these cows to improve the calf crop.

The beef value of bulls is outlined in the Dairy Beef Index (DBI). The lower the beef value of the dairy cows, the higher the beef value of the bulls will need to be in order to generate a four-or-five star calf in Commercial Beef Value (CBV) terms.

In other words, if the dairy cows have a higher beef value, lower beef value bulls can be used to generate the same four-or-five star CBV calves.

This means that these herd owners can focus more on calving traits and still breed very good CBV calves, whereas herds that have a low beef value will have to sacrifice some calving ease and gestation length in order to get high-CBV calves.

The question then is does the benefits of having a smaller cow outweigh the disadvantages of having potentially harder calvings?

Health

The health sub-index is increasing in importance in the eyes of many farmers. With renewed focus on TB in particular, the inclusion of TB in the health sub-index gives it added prominence. Up until recently, TB and liver fluke were sitting outside of the core EBI, but now the figures are incorporated into it. Lameness, SCC and mastitis is all hereditary and so this is included in the health sub-index also. The national average figure for the health sub-index within the EBI is €7 with the top 10% of herds achieving a value of €10. Looking at the Active Bull List published on page 51, there are still a significant number of bulls on the list with a below-average or negative value for health, and this is concerning. A bit like maintenance or fat and protein percent, farmers need to select a cut-off point for health, below which they will not use a bull.