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Managing Heat Stress in Transition Cows: How X-Zelit Can Help Your Herd Succeed

As temperatures climb, so do the challenges dairy cows must confront, especially during the transition period. This critical window, spanning three weeks before and after calving, sets the stage for a cow’s future health, productivity, and fertility. Add heat stress to the picture, and you magnify potential risks.

Today, our industry has many tools in our toolbox that allow dairy producers to fine-tune their management and nutrition strategies to help transition cows remain healthy and productive, even during the hottest months of the year.

Why Heat Stress Hits Transition Cows Hard

Heat stress occurs when cows can’t dissipate enough body heat to maintain a normal core temperature. Once the Temperature-Humidity Index (THI) rises above 68, cows begin to experience stress. For transition cows, who are already managing major hormonal and metabolic shifts, this added pressure can lead to:

· Reduced dry matter intake (DMI)

· Compromised immune function

· Increased risk of subclinical and clinical hypocalcemia

· Increased risk of retained placentas and metritis, resulting in other metabolic diseases

· Elevated core body temperatures, which can lead to other health and productivity challenges

In short, it becomes a perfect storm of metabolic stress, occurring when cows need to perform at their best.

The Calcium Connection

Calcium might not be the first thing that comes to mind during a heatwave, but it’s something that’s also impacted. Cows require calcium for muscle contractions, immune responses, and milk production. During the transition period, calcium demand increases dramatically, just as pre-fresh DMI intake drops. Now add heat stress, additional feed intake reduction, and a weakened immune system with the normal physiological and metabolic challenges at calving – clearly, the transition cow has a lot to deal with!

During these times of additional stress, the silent and costly issue of subclinical hypocalcemia, or low blood calcium without visible symptoms, can intensify. Subclinical hypocalcemia affects up to 40 to 50 percent of second-lactation and older cows. When combined with heat stress, the negative effects of this insidious problem become even more pronounced.

X-Zelit and New Casta Liquid: A Novel Approach to Calcium Management

X-Zelit and new Casta Liquid offer an innovative way to help reduce the stress associated with summer heat in both a dry (X-Zelit) and a liquid (Casta Liquid) form. These products work by inducing a mild hypophosphatemia through binding dietary phosphorus. This triggers bone calcium mobilization, significantly improving blood calcium levels during and after calving.

Why Is Proactively Managing Hypocalcemia Especially Helpful During Heat Stress?

– Helps Maintain Dry Matter Intake

X-Zelit and Casta Liquid allow more flexible pre-fresh diets because dietary K does not interfere with blood calcium response. This means more palatable forages like haylage and other small-grain forages can make their way back into the diet rather than having to rely heavily on straw. Through feeding more palatable forages, this helps maintain DMI through heat events and makes for a smoother transition from close-up to fresh diet.

– Supports DINCU and Stocking Density Management

X-Zelit and Casta Liquid are recommended for use 14 to 21 days in close-up (DINCU). Pre-fresh cows generate significant metabolic heat, so it’s critical to help control the heat load in the close-up period. By using these proven pre-fresh milk fever prevention strategies, you can also manage stocking density more effectively, maintaining lower pen populations that decrease excess body heat, support feed intake, and reduce stress from overcrowding.

– Promotes a Smooth Transition

More stable intakes through the transition period and less social and metabolic stress lead to greater metabolic stability. This leads to fewer veterinarian interventions, better transitions, and overall healthier fresh cows.

– Helps Maintain Stable Blood Calcium

X-Zelit and Casta Liquid are a novel pre-fresh hypocalcemia management strategy that robustly improves blood calcium by inducing a mild hypophosphatemia and triggering bone mobilization. This lowers the risk of both clinical and subclinical hypocalcemia and the metabolic disorders that follow.

Heat Stress Management is a Team Effort

While the diet is a powerful tool, it works best as part of a complete heat stress mitigation strategy. It’s critical to also provide:

· Proper ventilation and shade

· Fans and sprinkler systems

· Constant access to clean, cool water

· Consistent delivery of a properly mixed & stable TMR

Together, these strategies can significantly reduce the toll that heat stress takes on not only your transition cows, but also your entire herd.

Final Thoughts

Heat stress is more than just discomfort for cows. It impacts health, productivity, and your bottom line. Transition cows are especially vulnerable, so proactive planning is essential for lactation success.

Everyone Loves the Golden Girls

Dairy cow longevity reflects the overall health and welfare of your herd, plus it is a key component of farm profitability and sustainability. There are several ways to improve herd longevity — with one option being improving transition cow performance.

Higher cull rates in early lactation result from metabolic disorders and management challenges during the transition period. These transition challenges are highly correlated with reduced productive life of your dairy herd. Identifying and focusing on transitional risk factors allows you to minimize fresh cow challenges, which is a critical management tool to help retain those “Golden Girls,” who are often the biggest contributors to the bulk tank.

The transition period has a huge influence on herd longevity due to the many risk factors that are associated within this timeframe – ketosis, metritis, retained placenta, DA, hypocalcemia…the list goes on. One of our classic metrics to evaluate whether we’re losing excess cows during this timeframe and having transition period struggles is the “<60 DIM Cull Rate.”

Elevated <60 DIM Cull Rates (>6%) impact farm profitability, sustainability and morale. Older cows make more milk, so by minimizing cull rates and aging the herd, there’s opportunity to increase pounds shipped, along with a secondary benefit of reducing your herd’s replacement costs. Collectively, to improve profitability, it’s important to focus on how to maintain more of these mature cows that are doing what they’ve been bred for – making milk. In order to achieve solid transition metrics and a low <60 DIM Cull Rate, we need to continually identify and manage the numerous on-farm and individual cow risk factors involved in achieving transition success.

One of the most detrimental fresh cow risk factors is hypocalcemia, a metabolic disorder also known as milk fever. Hypocalcemia, both clinical and subclinical, has been well established as the gateway disease leading to a higher probability of other metabolic disease(s), lower milk production, reduced reproductive efficiency, compromised immune function and a subsequent higher cull rate.

Why do dairy cows get hypocalcemia?

At the onset of lactation, there’s a drastic increase in calcium demand for colostrum and milk synthesis. This increased demand exceeds the cow’s ability to maintain optimal blood calcium levels from diet alone, so she needs to rely on additional systems to pull from – such as bone. Bone is an important reservoir for both calcium and phosphorus during times where both calcium and phosphorus are in high metabolic demand.

There are multiple ways to proactively mitigate hypocalcemia through the close-up diet. The two most common methods are feeding a negative DCAD (dietary cation anion difference) diet or feeding a phosphorus binder, such as X-Zelit. These two strategies activate calcium bone reserves by different mechanisms to maintain higher blood calcium levels during this critical fresh cow window.

1. Negative DCAD diets work through inducing a mild metabolic acidosis through feeding supplemental anions in the diet. This results in an acidification of the cow, which stimulates parathyroid hormone (PTH) and vitamin D to release calcium from the bone and increase calcium absorption at the gut level.

2. Phosphorus binders, like X-Zelit, work by binding dietary phosphorus, which results in a mild hypophosphatemia. This reduction in blood phosphorus influences fibroblast growth factor-23 (FGF23) and vitamin D, which causes bone to mobilize phosphorus (and thus calcium) to replenish blood phosphorus. When bone is built, it’s built at a 2:1 ratio (2 Ca: 1 Phos), so when the cow mobilizes phosphorus, twice as much calcium is mobilized. This results in higher blood calcium levels at calving and significantly reduces the risk of both clinical and subclinical hypocalcemia.

Both dietary options provide practical strategies to help improve blood calcium at calving and reduce transition disorders. However, a recent study done at the University of Wisconsin – Madison showed that cows fed X-Zelit had significantly higher blood calcium concentrations relative to cows fed a negative DCAD diet during the close-up period. Not only did the study show a large benefit to blood calcium, but dietary DCAD was highly positive, which suggests that feeding X-Zelit doesn’t require the low potassium (K) forage-based diets to achieve enhanced blood calcium levels.

Herd longevity conversations are critically important to maintain profitability and sustainability. As an industry, we need to continually improve productive life. This goal starts in the transition period by identifying the nutritional, management and environmental risk factors. By eliminating bottlenecks, you can minimize fresh cow diseases, lower cull rates and boost the number of Golden Girls making a positive difference in your herd.

Much of our discussions at Protekta center around preventing fresh cow milk fever. However, fresh cows aren’t the only ones who can experience milk fever-like symptoms, such as down cow syndrome.

In a recent Progressive Dairy article, Protekta dairy nutritionist Rod Martin discussed mid-lactation milk fever (MLMF), which resembles traditional milk fever but can occur throughout the lactation cycle.

MLMF cows can appear fine one milking but then abruptly go down and not make the next trip to the parlor.

While the term “milk fever” is used for both challenges, it can be misleading since the causes for traditional low calcium milk fever are different than MLMF. Unlike hypocalcemia, MLMF can be due to low magnesium levels. In the article, Rod and co-author Neil Michael, a nutritional consultant with Progressive Dairy Solutions, outline how nutrition and inflammation can lead to MLMF.

Nutritional Factors

According to the authors, multiple nutritional factors can lead to hypomagnesemia, including soil types, plant mineral content, and magnesium antagonists that can inhibit nutrient absorption. They recommend working with a nutritionist and testing forages for major mineral content. In addition, other solutions to consider include increasing magnesium in your ration and evaluating magnesium sources, since some are less available for absorption by the animal.

Inflammation Factors

Rod and Neil detailed how inflammatory challenges can cause problems and result in down cows in the mid-lactation group. From leaky gut to pen overcrowding, the authors discussed inflammatory events and on-farm stressors and their role in MLMF. They recommend working with your management team to identify risks and minimize any potential threats.

Read the full Progressive Dairy article to better understand MLMF and for a list of actions you can take to identify and solve potential sources of mid-lactation issues.

What does spring mean to you? Longer days, more sunlight, flowers blooming, planting time, or a favorite of many producers: Letting the cows out onto fresh green grass after a long winter indoors?

For cows, it means the start of higher colostrum production.

According to a 2022 Michigan State University study, researchers recorded the following average first-milking, per-head colostrum output per season from three commercial Michigan herds:

• Winter (4.5 quarts)
• Spring (5.7 quarts)
• Summer (6.2 quarts)
• Fall (5.7 quarts)

Washington State University researchers confirmed that May and June have the highest colostrum production and December has the lowest.

Maureen Hanson, author of the Dairy Herd Management article Fall Brings Low Tide for Colostrum Output, turned to experts for answers. Our Protekta dairy nutritionist Rod Martin shared his insights and offered some nutritional and management measures to support higher colostrum production. “Dial into pre-fresh nutrition by examining the factors that affect dry-matter intake like bunk management, particle size, moisture, and forage fermentation consistency,” said Rod. He also noted, “The popularity of adding bulk to pre-fresh rations via straw and grass hay may lead to a higher incidence of ration sorting and introduce antagonists that interfere with the hormonal changes required for colostrum synthesis.”

Read the Dairy Herd Management article for more details and also check out another blog on this topic that Rod wrote back in November 2023, Low Colostrum Production: Lots of Questions…Not as Many Answers. There he provides on-farm checkpoints to review when colostrum production is challenged.

Michael Steele, PhD, and his lab colleagues are asking questions and offering answers for all of you calf raisers. We were happy to sponsor Dr. Steele’s webinar addressing new developments in calf nutrition. Listen as he pinpoints common practices ripe for reevaluation and where to challenge the status quo. His lab is passionate about studying early life programming. They believe you have tremendous opportunities to raise healthier calves by fine-tuning nutrition to enhance both performance and health. You’ll hear about the research behind calf-rearing practices surrounding colostrum feeding, milk composition, feeding planes and weaning nutrition. We hope you enjoy New Developments in Calf Nutrition: Challenging the Dogma.

In a recent study done at the University of Wisconsin-Madison by Frizzarini et al. (2024)*, researchers compared three close-up diets and their implications on blood calcium and performance. The three diets included one diet with X-Zelit, one with negative dietary cation-anion difference (-DCAD), and one with a positive DCAD (control).

The study, which resulted in two publications published in the Journal of Dairy Science, showed that cows fed the diet with X-Zelit had higher blood calcium concentrations and lower blood phosphorus concentrations during the transition period relative to the other treatments. In addition, cows fed X-Zelit had higher colostral IgG concentrations, plus cows in their third or greater lactation fed X-Zelit produced the most milk.

X-Zelit is a dietary phosphorus binder that naturally stimulates a cow to mobilize her calcium reserves for effective milk fever prevention. This novel approach capitalizes on manipulating phosphorus homeostasis, rather than calcium homeostasis. X-Zelit should be fed 14 to 21 days pre-fresh to prevent milk fever and subclinical hypocalcemia.

“Despite the vast improvements made in the industry to manage milk fever, subclinical hypocalcemia and “milk fever breaks” remain a challenge on dairy operations. This challenge has resulted in continuing research of pre-fresh nutrition strategies to mitigate clinical and subclinical hypocalcemia,” says Dr. Meghan Connelly, Protekta dairy research and technical services.

The University of Wisconsin study included 121 multiparous Holstein cows, blocked by lactation number and expected due date. Cows were randomly assigned to one of the three prepartum diets: control (+190 mEq/kg; n = 40), -DCAD (−65 mEq/kg; n = 41), or the control diet supplemented with X-Zelit (synthetic zeolite A; +278 mEq/kg, fed at 3.3% DM, 500 g/day; n = 40).

In Part 1 of the study, researchers evaluated the effects of the three diets on peri-partal mineral metabolism. Some of the mineral metabolism metrics Dr. Frizzarini and colleagues analyzed were blood calcium, blood phosphorus, and fecal phosphorus. The results showed that cows fed X-Zelit exhibited the highest blood calcium concentrations prepartum and during the first few days following calving relative to cows fed -DCAD or control diets.

Also, cows fed the diet with X-Zelit had lower blood phosphorus concentrations relative to all other treatments, which is consistent with previously published research results. In addition, these cows had decreased salivary phosphorus concentrations and increased fecal water extractable phosphate, collectively suggesting that feeding X-Zelit induces a mild hypophosphatemia.

In Part 2, the research team assessed the effects of feeding the same three close-up diets (X-Zelit, -DCAD, and the control diet) on dry matter intake (DMI), energy metabolism, and colostrum and milk production. In this companion paper, researchers measured daily prepartum DMI, daily rumination, colostrum quality and quantity, daily milk production, and supplemental blood work to evaluate energy metabolism.

The results showed that feeding a diet with X-Zelit reduced DMI and rumination prepartum compared to -DCAD and control diets, but no differences were observed in rumination postpartum. Despite the prepartum decrease in DMI and rumination in X-Zelit-fed cows, blood glucose, β-hydroxybutyrate (BHB) concentrations, and body fat mobilization postpartum were not different between treatments.

After analyzing colostrum samples, researchers determined that yield and BRIX score did not differ between dietary treatments; however, colostrum collected from cows fed X-Zelit had the highest IgG concentrations (91.10 ± 2.63 mg/mL for X-Zelit, 78.00 for control, and 78.90 for -DCAD). Results also showed that mature cows (third or greater lactation) fed X-Zelit had the highest milk production (51.0 ± 1.1 kg) during the first 49 days in milk compared to cows fed -DCAD or control diets.

“Overall, these results support that the improvement in blood calcium concentrations pre and postpartum from feeding X-Zelit is most likely regulated by a dietary phosphorus restriction,” said Dr. Connelly. “This research helps further validate the role that dietary phosphorus plays in hypocalcemia and corroborates the results nutritionists and producers are seeing on farms. X-Zelit poses an intriguing option for close-up cows as this mechanism appears to be independent of DCAD, which means the need to source low-potassium forages is reduced.

Consequently, the pre-fresh diet has a lot more forage flexibility and you can include homegrown forages higher in potassium.”

For more details, Feedstuffs highlighted the 2-part study in a feature story, plus Hoard’s and Bovine Veterinarian also covered the research.

References:

J Dairy Sci. (March 13, 2024) Mechanisms by which feeding synthetic zeolite A and a dietary cation-anion difference diets impact mineral metabolism in multiparous Holstein cows: Part 1 https://www.journalofdairyscience.org/article/S0022-0302(24)00546-0/fulltext

J Dairy Sci. (March 13, 2024) Mechanisms by which feeding synthetic zeolite A and a dietary cation-anion difference diets impact feed intake, energy metabolism and milk performance: Part 2 https://www.journalofdairyscience.org/article/S0022-0302(24)00547-2/fulltext

Rod Martin knows how efforts to mitigate milk fever have evolved over the years. He shared his decades of experiences in a recent Dairy Herd Management article and offered advice for the future.

Rod, a Protekta dairy nutritionist with more than 35 years of experience and unparalleled insights into managing hypocalcemia, says that back in the ‘80s the focus was on minimizing dietary calcium levels to address milk fever. But the daily calcium limits suggested by the research were not practical in the field.

In the early ‘90s, the correlation between high potassium diets and increased milk fever rates was discovered. Consequently, producers and nutritionists quickly adapted low-potassium diets utilizing forages such as grass hay and corn silage. As hypocalcemia research continued to advance through the next two decades, negative dietary cation-anion difference (DCAD) diets evolved. They not only incorporated potassium but also added sodium, chloride and sulfur to the dietary analysis.

Fast forward to the 2020s. Milk fever and subclinical hypocalcemia mitigation is focused on dietary phosphorus and practical strategies to minimize daily phosphorus intake.

All this progress over the years has led to a low incidence of clinical milk fever, but subclinical hypocalcemia is still unacceptably high. To continue on the right path to controlling this metabolic disorder, more attention needs to be paid to excess phosphorus, Rod says.

Read the full story about the evolution of milk fever mitigation in Dairy Herd Management.

After that, read our summary of the science behind the role of dietary phosphorus in improving blood calcium and preventing hypocalcemia. It details a recent presentation by Pat Hoffman, Professor Emeritus at the University of Wisconsin.

Rod Martin’s article first appeared in Dairy Herd Management. A presentation on the science behind the role of dietary phosphorus in improving blood calcium and preventing hypocalcemia was given by Pat Hoffman, Professor Emeritus, University of Wisconsin.