Dr. Bill Weiss, Dairy Nutrition Specialist, The Ohio State University (top of page) pdf file
The risk that a cow will develop mastitis is a function of pathogen load at the teat end and the cow’s ability to prevent a bacterial infection from becoming established in the mammary gland. Practicing good cow hygiene (keeping stalls clean, frequent scrapping of allies, and following good milking procedures) will reduce teat end exposure, and good nutrition can improve immune function, thereby reducing infection rates and severity of mastitis. The highest rates of mastitis generally occur during early lactation, and early lactation is the time when most cows experience negative energy balance.
During early lactation, dry matter intake (DMI) by dairy cows is low, whereas nutrient demand is high, which leads to cows being in negative energy balance. Body fat is mobilized to provide the energy needed for maintenance functions and to produce milk. The energy deficient experienced by most cows usually starts a few days before calving and continues for several weeks after parturition. Normal, healthy cows lose 0.25 to 0.5 body condition score (BCS) units in early lactation and reach their BCS nadir by 4 to 7 wk of lactation. Some cows start losing body condition several days or even a few weeks before calving, continue losing condition after calving, and lose more than 1 BCS unit in early lactation. The concentrations of nonesterified fatty acids (NEFA) and beta-hydroxybutyrate (BHBA) in plasma increase as cows mobilize greater amounts of body fat, and experiments have shown that both high concentrations of NEFA and BHBA have direct negative effects on the functionality of certain immune cells in cattle. Other experiments have found that a statistical link exists between energy balance and the prevalence of mastitis; cows with more severe negative energy loss are at a higher risk for mastitis than cows that lose less body condition. However, during the peripartum period, negative energy balance and elevated concentrations of NEFA and BHBA coincides with numerous other events, including hormonal changes, hypocalcemia, and changes in vitamin status; therefore, it is not possible to determine unequivocally that energy balance has a direct effect on immune function. However, enough data are available to strongly suggest that excessive mobilization of body fat and the associated increase in NEFA and BHBA during the peripartum period contributes to immunosuppression. Management and dietary practices that should help reduce excessive body condition loss include:
Prevent cows from becoming too fat in late lactation and the dry period. This may require a pen dedicated to fat lactating cows so that they can be fed a low energy diet. Excess energy consumption is a common problem during the dry period because dry cows only require about 14 Mcal of NEL/day. To meet, but not exceed, the energy requirement, a diet based on less digestible feeds is needed so that the rumen gets full before overconsumption of NEL occurs.
- Avoid a large decrease in DMI during the prepartum period. The DMI can decrease by more than 20% during the last 1 to 2 weeks of gestation. This large drop in intake causes cows to mobilize fat which can infiltrate the liver, causing fatty liver and ketosis. The drop in intake can be mitigated by feeding a less digestible diet to far-off dry cows so that average DMI for a Holstein cow during the dry period is around 25 to 27 lb/day. Cows with high DMI during the early dry period tend to have a greater decrease in DMI during late gestation than do cows that have more moderate DMI during the early dry period. The peripartum decrease in DMI can also be moderated by feeding a well-balanced prefresh diet (e.g., good forage, 30 to 35% dietary NDF, and 30 to 40% concentrate). Intake by specific animals can be reduced when pens are overcrowded. Make sure pens containing prefresh animals have adequate bunk space and stalls.
- Promote a rapid increase in energy intake post calving which usually requires a rapid increase in DMI. Feeding excessive grain (i.e., starch) or fat to increase the energy density of diets (i.e., Mcal/lb) usually is counterproductive because it often reduces DMI. Feeding a well-balanced diet based on high quality forage that contains moderate concentrations of fiber (approximately 30% NDF) and starch (22 to 25%) and <5% total fat improves DMI. Overcrowding fresh cows greatly restricts intake of certain cows, putting them at greater risk of increased body fat mobilization and mastitis.