Katrina Roberts, Herd Health Veterinarian, Anexa Vets
By Katrina Roberts, Herd Health Veterinarian, Anexa Vets
There are two parts to this answer:
1. Am I getting it right for the cows (achieving target pasture quality and quantity) and
2. Am I getting it right for the farm (achieving target residuals to maximise harvest this round and growth in subsequent rounds)?
InCalf recommends that the overall nutritional aim for the herd during mating is maintaining or gaining Body Condition Score (BCS) from the start of mating. However, small changes in BCS are hard to measure (even with whole herd BCS monthly). By the time you have measured a loss in BCS during the mating period it is likely some negative impact on submission and conception rates has already occurred, and it will take time to turn the cows around. From our experience and data (from hundreds of herds BCS’d at Anexa over the past few years) we also know that the young cow mob 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 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 assessments, your daily bulk tank parameters are the best way to monitor your herd’s nutritional status during the mating period. With many farms having a pasture surplus in early lactation due to the exceptional winter growth, in some instances residuals left by the milkers may have been well above target (1500-1700kgDM/ha) during the first round (or two). If cows are forced to graze into these residuals during mating (due to a feed deficit or to get back on top of quality) energy intakes will be affected. How you deal with this situation will be farm dependent but dropping paddocks for silage or topping pasture are two potential options.
Daily variation in protein and fat % is normal when cows are eating a diet that is mostly (>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 perfect indicators of how well cows are fed. InCalf recommends using a 10-day average bulk tank protein and fat % to monitor herd performance.
You cannot compare your bulk tank milk protein and fat % with your neighbours or with a previous farm. 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 better the energy status. New Zealand 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 as milk volume increases toward peak, 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 the herd is in positive energy balance.
If your cows, calving pattern and type and amount of supplement being fed are fairly consistent, bulk tank protein % is reasonably comparable between seasons. Therefore, when looking at your bulk tank protein %, you want to compare it to the previous 10-day period (is it higher or lower), and to the same 10-day 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?).
Fortunately, when you are getting it right for the cows, you are also getting it right for your farm!
Most of our Fonterra clients have given their Anexa Vets third 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, Tatua or Synlait supplier we can also sort out third party access. So, if would like us to help you keep your herd on track during mating, or need some help deciphering the data, please speak to your vet.