News & Advice

Monitoring nutrition during mating

Oct 3, 2018 | Dairy, Dairy Farm Reproduction, Farm systems, Milk Quality

Katrina Roberts, Herd Health Veterinarian, Anexa Vets

The most commonly asked questions we get from now until December are: 

  • How do I make sure I am feeding my cows well during the mating period without wasting pasture? 
  • How do I manage the dilemma of managing pasture quality and quantity without impacting Incalf rates? 

Well this is a very long discussion which cannot be solved here, as the decisions made on each farm are quite farm specific (NB: think that sounds like a non-committal consultant’s answer if I ever heard one!). However, here we will aim to give you some tips around making informed decisions with respect to feeding during the mating period. Incalf recommends that the overall nutritional aim for the herd during mating  is cows maintain or gain BCS from the commencement of mating.  However, small changes in BCS are hard to measure (even with whole herd BCS monthly). Once you have measured a loss in BCS during the mating period it is likely some negative impact on submission and conception rates has occurred, and it will take some time to turn the cows around. From our experience and data (from hundreds of herds BCSed at Anexa FVC over the past few years) we also know that the young cow mob pretty much doesn’t gain BCS during mating, the best they do is hold!

If you use liveweight monitoring you will be able to use the average weekly weight trends to monitor groups of cows (heifers for example), ensuring they are gaining weight slowly during the mating period. If they are losing weight, you are in a position to be able to take early action (separate into their own mob, change the feeding amount/type, milk OAD). If you need help making use of your liveweight data please talk to your vet.

As well as your pasture and any supplement measurements, your daily bulk tank parameters are the best way to monitor your herd’s nutritional status during the mating period. Most of the milk companies have great phone Apps to make checking in on your bulk tank trends very simple, but the key is deciphering this information!

Daily variation in protein and fat % is normal  when cows are eating a diet that is in the majority (>50%) pasture. The pasture composition will vary (species, time since last grazing, palatability); the exact amount consumed will vary; and cow maintenance will vary with walking distances, contour of the paddock, and climatic conditions. Therefore, daily variations are not good indications of how well cows are fed. Incalf recommends using a 10 day average protein % and fat % to monitor your herd performance.
You cannot compare your bulk tank milk protein and fat % with your neighbours or with your old share-milking job. Most of the time the absolute figures are less important than the changes over time.

Milk protein % is an indicator of cow energy status. The higher the milk protein, the higher the energy status. NZ and overseas research has shown that milk protein % is positively related to in-calf rates. That is within herds cows with a higher milk protein % have on average better in-calf rates than cows with lower milk protein %. There is a normal decline in milk protein % in early lactation, which you will see in the bulk tank measurements, however once the herd has hit peak production, you should see a slow but steady average increase in 10 day milk protein %. From your Planned Start of Mating (PSM) until the end of mating you will want a slow but steady increase in your bulk tank protein %, indicating a positive energy balance.

If your cows and calving pattern are consistent,  bulk tank protein % is reasonably comparable between seasons. Therefore, when looking at your bulk tank protein %, you want to compare the previous 10 day period (is it higher or lower), and the same period last year (is it higher or lower). A drop of more than 0.2% requires action. This may include; reviewing your grazing management; looking at the supplements being offered; interpreting the other bulk tank parameters (has milk fat % increased, has production dropped or has milk urea dropped?)
Consider the example (graphed) where we are tracking 10 day protein % (blue) and kgMS (orange) over the mating period (PSM early October) until the end of mating (Early December).

Protein % increases over the first 8 weeks of mating from 3.7 to 3.9 %. The slight blip in late October is too small to be of any concern. However, from early December onwards the protein % slowly decreases, only 0.1% over 3-4 weeks, but a change in pattern. The protein test trend, when considered with the milk production trend (cows held production until mid-late November and then declined through late November/December) suggests that energy intakes from Early December dropped, and cows were possibly losing BCS during this period. For those that remember last December, the average temperature for the month was 2oC above normal and the second warmest December on record (NIWA)! Therefore, these unusually high temperatures most likely had a negative impact on pasture quality and cow intakes. The herd in the example starts and finishes mating early, and has an above average 6 week in-calf rate, therefore, the majority of the cows were in calf by the time the energy intakes dropped, and there was minimal impact of this feed pinch on the final not in calf rate.

For a herd that has less cows pregnant at the time of a feed pinch (quality or quantity), there is potentially a bigger impact i.e. the cows that are not in calf are the ones that will potentially stop cycling and/or have reduced conception rates.

Most of our Fonterra clients have given their Anexa Vets 3rd party access to their bulk tank data. This means that we can help you monitor your energy status during the mating period. If you are an OCD or Tatua supplier we can also sort out 3rd party access. So, if would like us to help you keep your herd on track during mating, or help deciphering the data, please get in touch.

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