Dairy producers need to focus on numerous objectives when effectively managing the transition period. Successfully managing this life stage means there is no trade-off between cow health and milk production.
The transition period is best viewed as an opportunity to increase production and enhance reproductive health.
“It’s always been kind of a disease focus,” Thomas Overton, Ph.D., professor of dairy management and director of the Pro-Dairy program at Cornell University, said. There is a need to “shift our mindset” and to understand that the changes inherent in the transition stage are adaptive.
The transition period is characterized by decreased immune function, increased nutritional demand and increased production of reaction oxygen species. These factors all work together in an integrated system.
Each aspect itself, as well as all of them combined, need to be balanced in order to maintain health and productivity.
The transition phase’s changes in immune system functioning can be difficult to manage. During the transition period, balancing energy, immune system reaction and the production of reaction oxygen species is “critical,” Overton said. But overproduction of reaction oxygen species, which occurs as a stress response, becomes detrimental.
Implementing both nutritional and non-nutritional strategies can have a positive impact on individual cows as well as overall herd health. Cows under stress will exhibit physiological changes, and changes in dry matter intake will occur. Poor nutrition, whether a result of stress or of less-than-optimal feed management, will cause immune function changes.
Poor energy status results in suppressed immune functioning, no matter which life stage the cow is in. But during the transition phase, energy and nutrient demands increase dramatically to prepare the cow for lactation. Close monitoring of energy intake to prevent excessive negative energy balance during transition is warranted, Overton said.
If feed intake is depressed below what is needed to meet nutritional needs, a negative energy balance – leading to metabolic and infectious disease – can result. Non-esterified fatty acids (NEFA) in the blood are important sources of energy, but increased blood NEFA lowers immune functioning, and fatty liver and ketosis can result.
If energy is not balanced, blood NEFA levels will rise. Increased NEFA levels will further suppress the immune system, leading to metabolic and disease issues.
Protein and amino acids, vitamin E, selenium and calcium are all needed to maintain immune function, but the exact impact of each of the trace elements isn’t yet known. Close management of macrominerals during transition is required.
Research hasn’t “really focused on all trace elements and nutrients which can have an impact on cow immune function,” Overton said.
Endometritis is also a concern when there is a negative energy balance. The development of endometritis two to three weeks post-calving has been shown to coincide with lower dry matter intakes prior to calving. Dry matter intake of around 33 pounds per day in transition cows has been shown to be preventative.
An increase in haptoglobin post-calving is also associated with more severe endometritis, as well as decreased milk yield. Haptoglobin levels indicate increased inflammation. Cows with levels of this protein produced in the liver greater than 1.3 g per L at one week after calving have shown a significantly lower rate of conception than those with lower levels.
Nutritional management strategies
Energy control is important in both far-off and close-up groups. Closely managing dietary cation-anion differences (DCAD) of dry cows, particularly in the last two weeks pre-calving, can help prevent metabolic problems from arising during lactation.
DCAD feeding strategies during the close-up period include feeding low-potassium (K) and low-sodium (Na) forages and feeds. Supplementation of anions – partial or full – as well as calcium (Ca) may be needed depending on K levels when feeding forages. Magnesium (Mg) supplementation will be needed.
Maintaining a ration with a low (less than +5 meq per 100 grams of dietary dry matter) or negative DCAD can reduce the risk of hypocalcemia and clinical milk fever, as well as other associated metabolic issues. Monitoring urine pH will ensure that the DCAD is within the desired range for the feed regimen.
Controlled energy diets can help moderate any potential energy issues. Consistent feed intake, minimizing the sorting of rations, macromineral control as cows approach calving and ration fermentability during the fresh period are all important aspects of transition cow nutrition, Overton said. Fresh cow diets play a role in maintaining transition period health, too.
But nutrition is only one part of the puzzle. Stress during transition impacts dry matter intake, milk production and milk nutritional content as well as immune functioning and overall health. It is thought that stress hormones result in an inflammatory response, which has a negative impact on immune system functioning.
Stress comes in many forms. During transition, it is important to keep stocking density low. Separating cows from heifers can reduce stress. Limiting group changes or pen moves and alleviating heat stress will also positively impact transition cow well-being.
Environmental stress from crowded pens during close-up has been shown to correlate with decreases in milk production. Overstocking has the greatest impact on heifers. Commingling heifers and multiparous cows is believed to cause increases in heifer NEFA levels to the degree that they are “really struggling,” Overton said.
“Heifers need more time to eat,” so anything that limits access to their feed at all is stressful, he said.
Heat stress during transition is another controllable concern. Consistent increase in milk yields has been seen when cooling of dry pens has been implemented. Heat stress also decreases birthweight.
Herd-level monitoring by periodic weekly testing of representative cows can provide managers with a “barometer” of herd health. Urine pH, NEFA levels, blood ketone and haptoglobin levels are all indicators that can provide valuable herd-level data.
“As an industry, we’re used to looking at averages,” but with herd monitoring, “we’re not trying to look at every fresh cow,” Overton said.
Herd monitoring looks at variability. When using herd monitoring, a variation above 15 percent of the animals sampled is the “alarm.” This indicates there is something occurring at the herd level.
Successful management during the transition stage includes nutritional and non-nutritional approaches. Successful transition stage management will lower the rate of metabolic disorders and infectious diseases. It will also positively impact reproduction, increasing days to ovulation and enhancing fertility. And it will have a positive effect on milk production.
Transition stage management is still being studied, with “a lot of things we’re kind of learning all the time,” Overton said. The key to success is “implementation at the farm level of the things we know need to happen. High-performing dairies do all these things and do them consistently.” PD
Thomas Overton presented “Managing Metabolism and Immune Function of Transition Dairy Cows,” at the 2015 Penn State Dairy Cattle Nutrition Workshop.
Tamara Scully, a freelance writer based in northwestern New Jersey, specializes in agricultural and food system topics.