Efficiency and survival traits key to once-a-day herds

category Genetics

Once-a-day (OAD) dairy farming systems have been around for many years and have understandably increased in popularity in the last few years.

The upshot of this has been an increase in demand for AB companies to undertake breeding programmes producing bulls with genetics tailored for OAD systems.  This is nothing new to CRV Ambreed and we have continued to market bulls with the attributes most suited to OAD farming.

However, the specific requirements of the “OAD cow” and “OAD herd” are perhaps less understood, which I will address below.

It seems widely accepted that cows milked in OAD systems produce about 10% less milk solids per lactation than they would in traditional twice-a-day (TAD) regimes. On the other hand, they maintain better body condition and have better in-calf rates; they have fewer veterinary interventions; and less labour is required for the OAD system.

Compared to TAD cows, OAD cows are less likely to be culled as empty, but are more likely to be culled for high somatics or collapsed udders. Under OAD, high component – low volume cows tend to dry off earlier than desired.

The fact that OAD cows produce 10% less per lactation than under TAD farming in itself creates a problem which is likely to increase as environmental considerations receive more focus: without going into detail, the OAD cow producing 10% less per lactation is producing more methane per kilo of milk solids than her TAD contemporary.

But it’s not all bad for OAD. This is where the whole farm system needs to be considered.

While the OAD cow might be lower producing, she is also likely to stay in the herd longer than the TAD cow, providing her udder and somatics are desirable.

The OAD herd with greater longevity may require only say 16% replacement rate, while the average TAD replacement rate is around 22%. This means that in the OAD system, a lower proportion of the total feed resource is required by replacement stock and, conversely, a higher proportion is available for the milking herd.

The lower efficiency with which feed is used for milk production (and higher emissions per kilo of milk solids) by the OAD cow is balanced by the lower feed resource (and lower emissions) required for growing her replacement.

In summary, the OAD cow needs to be an efficient converter of feed to milk – the key component of New Zealand’s breeding indexes – but with more emphasis on the key survival traits for OAD, which are udder support and low somatic cells.

At CRV Ambreed, we have discussed OAD breeding with many farmers over the years. The consensus is that rather than have a specific breeding programme that would be relatively small and costly to run, OAD farmers favour using high indexing bulls which have favourable breeding values for udder support and (low) somatic cells. Farmers with herringbone sheds should also use bulls with positive milking speed.

CRV Ambreed uses a specific OAD index for identifying which of our high Breeding Worth (BW) or New Zealand Merit Index (NZMI) bulls are most suited to OAD. That index puts equal weight on protein, udder support and somatic cells.

When used year upon year, we believe our OAD bulls will breed productive, long-lasting OAD cows that will rival their twice-a-day contemporaries for overall herd efficiency and environmental compliance.

By Phil Beatson, Genetic Strategist CRV Ambreed

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