Protein deficiency in cows common in early lactation

We have always been led to believe that cows in a New Zealand pasture-based system are flooded with protein throughout early lactation and up until the summer dry spell. However, often in early lactation the opposite is true and many cows are forced to strip weight in an attempt to ‘mine’ their own protein reserves.

This common perception of protein being in abundance arises from the fact that in pastoral based systems such as ours, where protein rich ryegrass makes up the majority of a cow’s diet, protein is always sufficient. In most cases this is true providing cows are fully fed and high quality ryegrass makes up the majority of feed on offer. 

But here lies the problem. As we all know, there are a number of situations where cows are not fully fed. Early spring is one such time as farmers carefully monitor covers and set round length to match pasture growth rates. In these situations, it is not uncommon to find milking cows being offered 60 - 80 square meters per day (stocked at 125 – 170 cows/ha). 

Even assuming an optimistic pasture harvest of 1500 kgDM/ha, pasture intake at this stocking rate equates to a meagre 9.0 – 12.0 kgDM pasture! At this level of feeding most farmers would agree a definite need to provide additional supplementary feed to avoid the wheels falling off. The real question is, what feed is best suited?

Running this type of scenario through ration evaluation software helps answer this question. Modelling predicts a cow’s diet in this situation is lacking in excess of 1000g of protein, meaning in order to maintain and ramp up production she will need to make up the shortfall from her own protein reserves. Many cows unfortunately do exactly this to the detriment of body condition, milk production and reproduction.

For this reason, protein rich feeds such as DDG, canola and soy meal become very useful when grazing areas are restricted to milking cows in early lactation and while these feeds may be perceived as expensive, a little tends to go a very long way. 

So if you are still contemplating your cows’ dietary requirements and choice of supplements in early lactation, spare a thought for protein. Farmers that attempt to meet dry matter requirements as well as addressing specific nutrient deficiencies like protein generally reap the rewards overall.

Have a chat to your farm advisor, nutritionist or veterinarian about early lactation feeding and choice of supplements before spring arrives – if it hasn’t already!

• Greg Jarratt is a vet and director of Matamata Veterinary Services. 

This article is brought to you by J. Swap Stockfoods.