Why Transition Matters
Traditionally, transition period has been defined as three weeks pre-calving to three weeks post-calving. This may well be correct assuming adequate nutrition during the dry period. I far prefer to include the dry phase and even up to joining/conception. The job’s not done until she’s back in calf.
We will deal with the dry phase and springer phase in future articles, but suffice for now, the dry phase is where we, in Australian grazing based systems, create unprecedented grief to production and fertility even if actual calving was not troublesome. The non-visible issues often cost far more than the obvious, which draw our attention and response.
Our intent with this article is to begin thought and discussion on this subject well before the event to provoke some planning to the goal of more profitable lactations – minimal disease/improved production and reproduction. Apart from actual calving problems, many of which are related to sub-clinical milk fever and ketosis, the four most common metabolic diseases associated with calving are: 1) Milk Fever, 2) Ketosis, 3) Retained Placenta/Metritis, 4) Displaced Abomasum.
From any of these four, and they are commonly related or precipitated by the same nutritional deficiencies, and bring on each other, we can expect elevated mastitis incidence due to compromised immunity and low blood calcium. Mastitis, prior to six weeks post-insemination, has dramatic effects on conception and holding of pregnancies. The whole process is often described as a ‘cascade’ of metabolic disorders because they often precipitate each other, having profound negative impacts on cow profitability. The initial veterinary/drug or culling cost is only the beginning.
Cows are far more prone to disease around calving due to major metabolic and hormonal changes during this time. Starting a few days prior to calving, a change in activity from storing body fat to rapid mobilisation of body fat over just a couple of days; the sudden demand for energy to meet increased activity of the rumen, intestine, liver and kidney to support milk production. The metabolic demand of the mammary gland and the late term foetus all contribute to short-term, at least, immune deficiency. Any exposure to pathogens at this time, most frequently the udder, but not eliminating the uterus, has only added further infection risk to our calving cow.
The blood system also works overtime through this period. It is the transport system for nutrient changes and demands, hormonal agents to drive all necessary activity to give birth and have quality colostrum on hand for the newborn calf. Add to this, immune responses to sites of pathogen presence. The liver is also on overtime and very susceptible to fat overload when dietary energy is lagging behind.
Immunity often has impaired response from hormonal stress, insufficient energy intake/supply which in turn impairs glucose production. This is the precursor for ketosis as insulin levels rise and only further the blood glucose concentration problem. Reduced liver function then increases as fat load increases. Finally, calcium metabolism is reduced. An obvious issue to milk fever even if dietary calcium is adequate (but never is), and many other bodily functions that are calcium dependant including immunity. Even having gotten past calving, the impact of lactation demand still inhibits immunity. Calcium is by far the most critical component of transition nutrition; and the hardest to achieve in a grass based system!
Nobody doubts calcium’s role in milk fever. But that’s the tip of the iceberg. From there we see reduced feed intake from a lethargic cow – sub-clinical milk fever. Reduced intake has an obvious impact on rumination. From reduced rumination we move on to sub-optimal rumen pH (reduced saliva production) and the risk of acidosis to some degree of severity. Low blood calcium reduces muscle/ligament tension and combined with a rumen that is not full, the risk then moves to displaced abomasum.
The reduced feed intake also promotes negative energy balance increasing the degree of ketosis. A very high number of cows do have some degree of ketosis from body fat mobilisation, especially when suppressed feed intake induces negative energy balance. Additional body fat is mobilised attempting to meet this energy deficiency resulting in fatty liver syndrome, the precursor of ketosis. All this can be happening in the few days prior to calving which then sets our cow up for dystocia (long calving due to low energy).
While the cow is lying for an extended time calving, she is particularly prone to bacterial infection from pathogens entering both teat ends (weakened teat end muscle), and the uterus particularly when the birth canal is open.
Minimisation of stress on cows around calving and early lactation has several aspects: 1) Nutritional, much of which we’ve discussed above, and will elaborate on over the next few months 2) human induced stress. The dry cow often escapes human intervention for a few weeks, but this too often, is the cause of nutritional stress. For those who have rumination technology on their cows, leave the device on several dry cows and monitor rumination. I think you will get some surprises!
Cow handling stress can escalate around calving and good planning to avoid unnecessary intervention will pay dividends through feed intakes and stress’s impact on immunity. Shifting cows from dry groups to springer groups induce social stress. Larger herds can dry cows off and they stay in the same group until calved.
Research has some alarming data on potential risk increase as the various issues around calving increase. Perhaps, none so much as reduced feed intake. Disease risk factor increases by multiplier degrees.
Despite the daunting list of possible problems around calving, many can be avoided by sound nutrition: energy, protein, fibre and supplementary minerals. None of these are difficult to achieve; especially with a little early planning to ensure we have the necessary feed to meet these needs on hand.
Many years ago, my then veterinarian and great teacher, while performing a caesarean section on one of my cows, and in the depths of explaining everything to me, commented; “the most dangerous thing you can do in life is giving birth or being born”. At the time, my wife was only days off giving birth to our eldest son! The cow eventually went to the meat works, but the wife and son survived.
John Lyne is a dairy production specialist with Dairytech Nutrition
www.dairytechnutrition.com.au
