We often hear the phrase that “change is just a part of life,” and indeed change is ever-present. “Transition is just a part of life,” however, may be more acceptable to some, as it seems less intimidating.
This is certainly the time of the year when transition is occurring all around us. The transition from winter to spring means it is now planting time. The transition of youth from high school moves students to college or the workforce. We could keep identifying more transitions. How does this relate to a dairy herd?
Our goal as farm managers should be to assist dairy animals through transitions within the herd by reducing health risks and promoting longevity and profitability. Healthy and productive cows will stay in the herd and not leave the herd.
Management system comparison
A group of researchers at the University of British Columbia published a review paper in the June 2022 issue of Journal of Dairy Science on the risk factors for transition diseases in herds that do and do not practice grazing. Although the number of herds were limited for the comparison, the data summarized reveal that disease risk is similar between the two management systems.
Some of the cow-level risk factors summarized by the authors included the following:
• Body condition score: Cows that are fatter (BCS ≥3.5) at the end of lactation eat less during the dry period and are more likely to lose BCS at calving and subsequently develop uterine diseases.
• Breed: Jerseys are more susceptible to hypocalcemia. Jerseys have been found to have higher risk for subclinical ketosis in some zero grazing and grazing herds compared to holsteins, but there is no difference in other studies.
• Parity: First lactation cows have a higher incidence of uterine disease and a lower incidence of metabolic disease during the transition period when compared with older cows.
• Age at first calving, gestation length and length of dry period: Heifers that calve at 25 months of age or older and cows having longer dry periods have higher prevalence of subclinical ketosis.
• Milk yield and components: Mastitis is consistently positively associated with milk production, both in grazing and zero-grazing herds.
Herd level. A couple of the herd level risk factors included the following:
• Management factors: Regrouping and overcrowding increase agonistic interactions, disrupting feeding and lying behavior in zero-grazing herds. Cows housed on pasture during the dry period benefit from rotational grazing, possibly by having cleaner lying surfaces, whereas cows kept indoors benefit from routine stall and calving pen cleaning.
Grazing cows may experience longer periods of negative energy balance after calving, explaining the relatively high prevalence of subclinical ketosis 3 to 5 weeks after calving in some grazing herds.
• Ambient factors: Season can be a risk factor for metritis, retained placenta, and subclinical ketosis. Rainfall at calving is associated with higher risk of clinical mastitis during the first 90 days postpartum in some grazing systems.
Regardless of the management system, nutritional strategies for mid- to late-lactation cows should try to avoid overconditioning of cows and following up on lameness cases occur frequently as a way of reducing lameness incidence and chronic cases during the dry period.
Management of the feeding system, including the grazing system, should focus on dry period management and mitigating environmental risks, including heat stress and wet conditions.
More focus on late lactation and the early dry period can avoid some of the predisposing conditions to transition diseases. Therefore, focus on management of cows prior to the close-up dry period and early lactation, typical time frame referred to as the transition period, can reduce the risk of transition diseases on dairy farms.
Most health events occur within the first 30 to 60 days of lactation, but prevention starts long before that as cows transition from declining milk yield to the dry period to lactation again. Transitions through these phases need to occur smoothly for them to stay healthy and productive.
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