I was talking to a dairy farmer who had recently purchased boluses he was planning to use for aiding dry off. He asked me if I had any experience with them, and I admitted that I did not. However, this topic piqued my interest so I dug into what literature was out there. With the Miner Institute herd, dry off is often brought up as a topic of concern because of the level of productivity of our animals, not an uncommon issue with farms that have increased milk yield in recent years, but also increased persistence in lactation. Normally, high milk production would not be something to complain about but when we transition these cows into the dry period it can be a challenge to maintain cow health and welfare.
Conventional methods of dry off may include a reduction in the number of milkings, a change of feed quality or amount, or abrupt cessation of milking. Managing the number of milkings or a diet change could be challenging depending on the farm size and ability to manage these different methods. Likely the most common method would be abrupt cessation of milking along with a diet change as they move to a far dry or dry diet. The challenge with abrupt dry off comes with high producing cows that might not be as prepared for dry off. When abruptly dried off, high-producing cows can be at greater risk of intramammary infections, clinical mastitis in early lactation, and higher somatic cell count (SCC) in the next lactation. For a time after dry off cows continue to produce milk which increases the intramammary pressure, results in milk leakage, increases pain and discomfort, alters lying behavior, and can also delay the teat plug formation which puts cows at risk of intramammary infection. Are there other methods that could help dry these cows off?
Two studies have evaluated using acidogenic bolus in cows and the impact on milk production, udder health, and behavior of cows around dry off and their health in the subsequent lactation. Acidogenic bolus use ammonium chloride and calcium chloride which are strong acidifying agents that induce metabolic acidosis and reduce feed intake. In the first study in a series of three conducted in Spain (Maynou et al., 2018; https://doi.org/10.3168/jds.2018-15058), 84 cows were bolused either a sham (control), one 20-gram bolus, or two 20-gram boluses five days before dry off. In this study they gave the bolus five days before drying off the cows so that they could record milk production in response to the treatments. Cows started out at 62 lb/d (28 kg/d) before the treatments were administered. The milk production of cows given two boluses dropped steadily over the next three days to ~54 lb/d (24.5 kg/d) or about a 4.5 lb/d (2 kg/d) decrease.
In the second study, the researchers followed the initial project to determine the impact of two boluses on dry matter intake in lactating cows. After the two boluses were administered the researchers observed a decrease in dry matter intake of 5.7 lb/d (2.6 kg/d) during the first three days. This decrease in dry matter intake from anionic salts had previously been well-documented. Of interest with the bolus, the salts are fat-coated and thus should not impact palatability like they would potentially be in acidified close-up diets. This reduction is likely related to the metabolic acidosis induced by the pulse dose from the bolus. After the initial three days after the bolus, the intake of the cows returned to levels similar to that observed before the bolus.
The third study from this research group used 152 cows that were either given a control or two boluses 8-12 hours before dry off. On average the cows in the control group were producing 60.4 lb/d (27.4 kg/d) of milk and 19.2 lb (8.7 kg) in the last milking (3x/d milking schedule) before dry off, while the cows given the two acidogenic bolus averaged 58.0 lb/d (26.3 kg/d) and 18.5 lb (8.4 kg) in the last milking before dry off. There was no difference between these two treatment groups for production before dry off. In this study, they measured udder pressure in the days after dry off, which decreased with time and was more marked in cows given the two bolus. Cows had lower udder pressure 24 and 48 hours after dry off, and tended to be lower at 72 hours compared to control cows. Interestingly, cows given the bolus spent 85 more minutes per day lying down compared to control cows, which might be due to lessened pressure and discomfort as a result of the bolus. There was no difference noted in milk leakage, and it was highest in the first one to two days after dry off for both groups. When these cows entered lactation, there was no difference in milk production.
A more recent project, published in 2024 (Florentino et al., 2024; https://doi.org/10.3168/jds.2023-23757), followed up on this work to evaluate the rate of intramammary infection, milk production, SCC, clinical mastitis, and herd removal in the subsequent lactation after cows received either a control or two acidogenic bolus. This study enrolled 901 cows across three commercial farms. They had 458 cows on the control and 443 cows that received two bolus at dry off. The results from this study included no difference on intermammary infections, fat corrected milk production, or protein or fat yield in the subsequent lactation between the two groups. They researchers did observe a lower SCC in the first two months after calving for cows who received the bolus and the presence of high SCC in the first 30 days was 9.1% lower than the control. Furthermore, cows that got the bolus at dry off had a reduced risk of clinical mastitis and removal from the herd.
This information supports the potential for acidogenic boluses to assist the dry off process of high-producing cows. There doesn’t appear to be any negative impact on the cow from the short-term metabolic acidosis induced from the bolus and there could be reduced risk of mastitis in the next lactation. Have you used this on your farm or seen places it’s been effective?
— Sarah Morrison