����ֱ��

DULUTH, Ga. (Aug. 29, 2024) —��While clinical cases of hypocalcemia, also known as milk fever, have declined, thanks to improvements in transition cow protocols, subclinical hypocalcemia (SCH) continues to be one of the toughest challenges facing transition cows. As many as 73% of dairy cows on third or greater lactations are reported to be impacted by SCH.¹��Yet, by definition, SCH doesn’t present with any physical signs of disease, making it difficult to detect.

“That’s why a lot of dairymen and -women don’t realize there’s a problem — they may not see clinical signs associated with hypocalcemia, but it is impacting the cow,” said Joe Gillespie, DVM, Boehringer Ingelheim.

SCH occurs when blood calcium levels are just below what’s considered normal for fresh cows (8.5–10.5 mL/dL). These cows have enough calcium to avoid the more severe symptoms of clinical hypocalcemia, but are still deficient.

“With subclinical hypocalcemia, you’re losing milk production because the cow is putting so much calcium into the milk that she doesn’t have enough calcium left over for the important body functions such as immune function, muscle function and overall health,” explained Dr. Gillespie.

But there are things producers can do to keep cows healthy and productive after freshening.

While many producers provide calcium supplementation immediately after calving, Dr. Gillespie said it’s not enough. “Hypocalcemia doesn’t just happen on Day 1; it can be a problem over several days.”

To help further define this challenge, recent research categorized the types of SCH, based on the timing and duration of blood calcium–level drops:^2,3

Cows with��persistent��or��delayed��SCH are more likely to develop subsequent early-lactation diseases, be removed from the farm and have reduced milk yield compared to cows with��normal��blood calcium levels or cows with��transient��SCH.³

“The goal is to maintain blood calcium levels throughout the entire transition period,” said Dr. Gillespie. “Providing a second calcium bolus on Day 2 helps maintain calcium levels more effectively.”

Providing a calcium supplement that’s easily absorbed and used by the body is important to ensure cows’ calcium needs are met after calving.

“If you have an insoluble salt, it just passes right through the animal’s system,” noted Dr. Gillespie. “You need to provide the right kind of salt that’s going to be absorbed quickly and work effectively.”

Of the three main types of calcium salts, acidogenic salts are the most appropriate. Providing a calcium bolus supplement containing calcium chloride and calcium sulfate (both considered acidogenic) allows for more available calcium in the blood during the fresh period.

“Calcium chloride and calcium sulfate are absorbed and available in the blood stream, which helps cows maintain blood levels without negatively impacting calcium utilization from the body,” continued Dr. Gillespie. “Adding calcium early and the ability for the body to make calcium available provides a more efficient transition.”

Supporting feed intake and reducing stress can lessen the impacts of SCH and start cows on the path to a successful lactation.

“Because cows are diverting so much calcium to milk production, some of the basic body functions are compromised, and what’s compromised the most is muscle function,” said Dr. Gillespie. “Depressed muscle function, especially the smooth muscles important for digestion, means animals may not get as many nutrients into their body.”

Evaluating nutrient availability and digestibility in the close-up and fresh cow rations and not overcrowding the fresh pen can help manage stress and encourage feed intake.

“At the end of the day, we want to make sure fresh cows have an acceptable diet, are comfortable and have enough calcium to maintain normal body functions,” concluded Dr. Gillespie. “If we do all those things in balance, we have the opportunity for those cows to have a more productive lactation.”

A successful fresh cow program is a team effort. Dr. Gillespie encourages producers to work with a nutritionist and veterinarian to make a comprehensive fresh cow program unique to your herd’s needs.