Why Not to Factor in Body Weight Loss in Your Diets for Fresh Calvers
As we head into winter its currently my busiest time of year as I set up winter diets for group members, nutrition clients and am also being asked to look at more and more non-clients’ diets, being that I am independent nutritionist with no ties to any feed manufacturer.
My main aim, wherever possible, is to ensure all my base diets have a minimum 65% forage, as this is to optimise rumen fermentation for butterfat production.
I recently reviewed a diet and saw something that I hadn’t seen for a little while in a diet, that I considered a little old fashioned and out of date.
It was a diet that showed an expected body condition loss, or fat mobilisation, of minus half a kilo a day or 1 BCS point in 30 days.
We all know that cows lose body condition post calving, because their DMI (dry matter intake) lags energy required for the rapid increase in milk yield. Research shows cows with excessive negative energy balance (NEBAL) in the first 30 days of lactation are associated with delayed ovulation and have poor fertility. The goal is to keep BCS (body condition score) loss in 0 - 30 DIM at less than half a point.
In an ideal world cows should be back in positive energy by 45 DIM (days in milk), and this is more than possible as I have clients with cows back into positive energy by 35 DIM post calving. You can measure this by reviewing the milk fatty acid profiles from your milk recording data, specifically by looking at the results for C18:1 & MUFAs (Mono Unsaturated Fatty Acids) as these are an indication of body loss.
These are diets where I am specifying no body weight loss, and therefore no negative energy balance post calving. I know this isn’t true because I know the cow will be in negative balance until she fully regains her appetite post calving etc.
However, I don’t want to make the situation worse by saying that this is happening. By telling the rationing program that I am expecting the body weight loss, I am telling it that the cow will be providing some of the energy she requires from her own reserves, or “off her back” as we used to say, which therefore says her requirements are actually less than they are in reality. This means she is receiving less energy than she actually requires and so draws even more from her own body reserves, thus increasing her NEBAL.
For example, the ration program I use shows that for an 8,000 cow, at 4.0% butterfat & 3.3% protein, 40 days post calving requires approximately 295MJ of energy per day.
f I instead have a ration set up for a cow with the same criteria but losing half a kilo of body weight a day, her requirements are only 280MJ of energy.
That’s 15MJ less energy, or roughly 3 litres of milk, that the ration program is expecting the cow to have to provide for her expected level of production.
So, she’s already going to lose condition, but you are now expecting her to make up a further energy deficit to achieve the desired production levels and so compounding the problem further!
We then need to look at the work by Prof Jon Huxley, formerly of Nottingham University, “Does a lame cow go thin or does a thin cow go lame?” This showed that a thin cow, loosing condition too quickly post calving is more likely to go lame. This is because the C18:1 that I mentioned earlier is being lost from the fat pad in a cow’s foot, between the sole & pedal bone, which will lead to more lameness, particularly sole ulcers. So, if your herd suffers a large number of sole ulcers then it suggests that your cows are losing too much weight, too quickly, post calving.
Therefore, if you want to reduce NEBAL in your cows, shorten the period that it takes for her to get back into positive energy, reduce the chance of lameness, improve their chance of getting back incalf quickly, don’t let your rations factor in body weight loss, that we know is going to happen, because it will only compound the problem and make matters worse!
If you’d like a review of your proposed winter diet, then please call FAR registered Dairy Nutritionist & CowSignals® Master Andrew Jones on 07717 442888 or email email@example.com
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