Good management of cows in the dry period will reap benefits for their calves

Prioritising dry cow management in this important stage of a dairy cow’s production cycle will ensure the best outcomes for the dam and calf.

As her due date approaches, there can be many challenges for the cow, not least a compromised immunity, especially in the final three weeks.

By meeting all her needs in this stressful and high-risk period, there is a greater likelihood that everything from calving to post-birth health and performance will be positive, says Dr Amanda Dunn, of Bonanza Calf Nutrition.

Dry cow nutrition

The nutritional needs of the dry cow are complex.

Feeding influences many factors including colostrum formation, the health and growth of the unborn calf, calving, and metabolic diseases that can occur post-calving and in early lactation.

Research by Mann et al., (2016) found that feeding dairy cows a diet that met their energy and protein requirements during the dry period increased colostrum immunoglobulin (IgG) content compared to cows receiving 150% of their energy requirements, and there was no difference in colostrum yield.

Getting the right balance of energy and protein during this time also affects the cow’s own body condition score (BCS) and the size of the foetus, both which dictate calving ease.

In the Mann et al., (2016) study, better calf health was linked to cows being in optimum BCS, 3 – 3.75 on a five-point scale; this was attributed to the effects of pre-calving BCS on colostrum IgG content.

In 2012, Gao et al. reported that low maternal energy intake during the last three weeks of pregnancy reduced calf birthweight and size, and immune system function.

Recently published research (Wachter et al., 2021) found that restricting phosphorus levels to 0.16% dry matter (DM) in the last four weeks of the dry period had a positive effect on calcium homeostasis, with less risk of milk fever in freshly calved dairy cows and no negative effects on DM intakes, milk production, or metabolic issues in the subsequent lactation.

A good option for forage is to set aside higher fibre grasses which haven’t been exposed to too much slurry or fertiliser to make dedicated silage for dry cows.

It is best practice to avoid feeding dry cows silage harvested later in the year, to minimise the risk from high levels of potash.

As well as a diet low in potassium, supplying the cow with adequate magnesium is a must during the dry period as this will help her avoid common metabolic issues such as milk fever.

Interestingly, not only does feeding too much phosphorus in the dry period affect cow health, but current research (Sohrabi et al., 2024) has highlighted that the proportion of calves with failure of transfer of passive immunity (FTPI) is significantly greater in calves born from hypo calcaemic cows, especially those with low calcium status in the first four days of life and beyond.

These calves also had a higher incidence of diarrhoea during the first ten days, probably because of poorer IgG absorption or perhaps a change in intestinal structure, making the calf more vulnerable to diarrhoea (Hunter, 2015) and respiratory disease (Wilhelm et al., 2017).

Dairy cows supplemented with organic trace elements had significantly higher colostrum IgG content compared to cows supplemented with inorganic minerals in most (Kincaid and Socha, 2004; Formigoni et al., 2011; Roshanzamir et al., 2020) but not all studies (Juniper et al., 2019). This suggests a role for trace elements in colostrogenesis – the transfer of IgG from the blood to mammary secretions – specifically the synthesis of IgG.

Correspondingly, organic sources of some trace elements fed to dairy cows pre-calving can increase calf blood antioxidant capacity and Ig concentrations and health parameters (Roshanzamir et al., 2020).

Housing and general management

Feed space: Making sure cows have adequate space to feed and lie down is beneficial to their performance. The cow is naturally bigger when she is heavily pregnant, and crowding can cause pushing and result in injury and pain. High stocking rates can often reduce feed intakes and should be considered when grouping dry cows according to calving date.

Far off and close up period: An up-to-date calving list with due dates is useful for ensuring cows get their correct feed and adequate minerals and vitamins to support the needs of the developing foetus and to promote colostrogenesis.

Heat stress

Research (Dahl., 2016) has shown that feed intakes reduce during times of extreme heat. These conditions can also lead to premature calving before the calf is fully developed and prevent optimal mammary gland development, leading to less milk being produced by the cow’s daughters and granddaughters over their lifetimes. These calves are often born earlier and will have lighter birth weights. Having fans and water sprayers on standby or providing extra ventilation at times of extreme heat is of the utmost importance for avoiding unnecessary stress to both the cow and unborn calf.

Vaccination

Dry cows are often vaccinated against common scour-causing pathogens, with antibodies passing to her newborn calf via colostrum.

Managing vaccine programmes and getting the timing correct has a huge impact on the success of an inoculation.

Colostrogenesis usually begins five to six weeks before calving so it is important to allow time for the cow to respond to the vaccination, with antibodies passing firstly into her own bloodstream before entering the mammary tissue and colostrum.

It is important to bear in mind that the cow’s immune response is suppressed from around three weeks before she calves and that means she won’t respond as well to a vaccine at this time because of a steady decrease in lymphocyte populations (Kehrli et al., 1989; Kimura et al., 1999).