“Effect of dry-off management on milking behaviour, milk yield and somatic cell count of dairy cows milked in automated milking systems.”Journal of Dairy Science Vol. 105, No. 4, 2022.
This article, from researchers from Ontario, Quebec and Alberta, investigated the effect of dry-off management of cows milked in automated milking systems on milk yield, milking behaviour and somatic cell count (SCC). The authors explain that milk production may be reduced before dry-off to decrease the risk of cows developing intramammary infections during the dry period, and that such reductions in milk may be possible in an automated milking system, where milking frequency and feed allocation at the automated milking system can be controlled at the cow level.
The authors used data from 445 cows from five commercial dairy farms in Quebec. The treatments were applied from day 14 to day 1 before dry-off and consisted of a combination of altering the feed allocations and the number of milkings: reduced feed [allowed a maximum of 0.75 kilogram per day of pellet in the automated milking system for the first week (14 to eight days before dry-off) of treatment, and 0.50 kilogram per day for the second week (seven to one days before dry-off) of treatment], or non-reduced feed (allowed up to 2 kilograms per day of pellet in the automated milking system) and either reduced milkings (2X milking or as many times as required to yield 17 kilograms), or non-reduced milking (allowed up to 6X milking and no maximum production).
The authors, citing several other authors, indicate that from the weeks after dry-off, when the mammary gland undergoes involution, to the onset of the next lactation with the proliferation of mammary epithelial cells and milk production, the cow is most susceptible to the occurrence of new intramammary infections (IMI). Thus, management of the mammary gland is particularly important to properly set cows up for the next lactation and limit the occurrence of new cases of mastitis. They say that one of the strategies identified for reducing the risk of new IMI before dry-off and through the dry period is to reduce milk yield in the weeks leading up to dry-off. Milk yield before dry-off is a key factor affecting not only the susceptibility to IMI but also the potential for increased pain and discomfort around dry-off. They refer to studies demonstrating that milk yield can be reduced up to 33% during the final week of lactation when milking frequency was reduced to 1X milking compared with 2X milking, and that no study to date has demonstrated any negative effects by reducing from 2X milking to 1X milking on cow health and behaviour, implying the benefits of reducing milk production before dry-off through reducing milking frequency is more beneficial than harmful. Another method they indicate to reduce milk yield before dry-off is to reduce dietary nutrient intake, ideally without inducing any level of hunger in cows, which could negatively affect cow welfare.
The study concluded that cows with reduced automated milking system feed allocation and reduced milking permissions for the two-week period before dry-off had the greatest decline in milk yield over that time period and the least milk yield at dry-off. They also demonstrated that reducing either the milking allowance or the feeding allocation at the automated milking system alone were also efficient at decreasing milk yield before dry-off, but to a lesser extent than using both strategies. These reductions in milk yield to facilitate dry-off were achieved without having a negative effect on milking behaviour, SCC or milk yield in the early weeks of the subsequent lactation.
“Selective dry cow therapy effect on milk yield and somatic cell count: A retrospective cohort study.” Journal of Dairy Science Vol. 105, No. 2, 2022. This study – from researchers from the University of Helsinki, Finland – compared milk yield and SCC between antibiotic dry cow therapy (aDCT)-treated and untreated cows in herds that used selective aDCT, considering risk factors for reduced yield and high SCC. Selective dry cow therapy means that only infected or presumed infected cows are treated, instead of aDCT being used as a blanket treatment for all cows. To this effect, they used data from DHI, from 2015 to 2017, with 4,720 multiparous cows from 172 Finnish dairy farms. They evaluated the test-day milk (kilograms per day) and the SCC during the first 154 days in milk (DIM).
The authors explain that mastitis is the most common disease in dairy cows, causing significant economic effects on milk production and compromising animal welfare. They add that aDCT is an effective way to control mastitis, as cows are susceptible to new IMI at the time of drying off and again during the periparturient period. They cite different sources saying that several countries use a blanket DCT approach, in which intramammary antibiotics are infused at dry-off into all quarters of all cows. They refer that this treatment recommendation is based on the five-point plan created in the 1960s and has since been a tool to reduce mastitis. Since then, antibiotic resistance has become a serious global health threat. The authors say that because the most essential methods for controlling antibiotic resistance are by restricting the use of antibiotics and improving hygiene, optimizing all antibiotic therapy use is crucial.
The authors explain that in the selective aDCT approach, only infected or presumed-infected cows receive treatment, and that recent results suggest selective aDCT succeeds without compromising udder health even if implemented only for infected quarters. They also mention that an alternative means to avoid antibiotic treatment is by administering intramammary teat sealants to healthy quarters. In high-yielding cows, the formation of a protective keratin plug may be delayed or deficient, and the sealant effectively mimics this natural defence mechanism.
The study found that the SCC on the last test day prior to dry-off affected post-calving milk yield differently in aDCT-treated cows than in untreated cows. A higher SCC prior to dry-off correlated with a greater daily yield difference after calving between cows treated and untreated. The majority of cows had SCC less than 200,000 cells per millilitre before dry-off, and as SCC before dry-off decreased, difference in yield between aDCT-treated and untreated cows decreased. Post-calving SCC was lower for aDCT-treated cows compared with untreated cows. To clarify this point, the authors give an example: For cows with an SCC of 200,000 cells per millilitre before dry-off, compared with untreated cows, aDCT-treated cows produced 0.97 kilogram per day more milk and, at 45 days in milk, had an SCC that was 20,000 cells per millilitre lower.
Overall, the authors conclude saying that a missed aDCT treatment for a high-SCC cow has a negative effect on subsequent lactation milk yield and SCC, which emphasizes the importance of accurate selection of cows to be treated.
This column brings you information regarding some of the research being done around the world and published in the Journal of Dairy Science. The objective is to bring to light areas of research that may have an immediate practical application on a dairy farm, as well as research that, even though it may not have a practical impact now, could be interesting for its future potential application. The idea is to give a brief overview of select research studies but not go into detail on each topic. Those interested in further in-depth reading can use the citations to find each study.
