Where is Your Milk Fat Coming From…Your Ration or her back?
As seen in Progressive Dairy
A few years ago, when the high palmitic fat options were relatively new, I had a client that decided to swap the type of fat supplement that was being fed to their fresh cows. They were feeding ½ pound of a traditional calcium salt and replaced it with an equal amount of a high palmitic prill. Over the next three months, they utilized their Afi monitoring system to not only measure changes in milk and milk fat, but also in body weight since cows got weighed every time they left the parlor after milking. In short, the cows responded well with higher ECM but with no change in dry matter intake. Therefore, it came at the expense of extra body weight loss…to the tune of almost 100 pounds in the three-week post-fresh period.
While this may not be how all herds respond, this experience certainly engrained in my mind just how important it is to not only feed enough fat, but also to feed a balance of specific fatty acids in the transition period. You may be wondering what exactly is that balance we are trying to achieve? To give you the answer up front, it’s aiming for a combination of fatty acids that supports all her essential needs after calving, not just one or two of them. Those include high ECM of course, but also metabolic health, minimize body weight loss, and strong immune health that leads to high fertility and reproductive efficiency. Let’s walk through some of the most common ways that fatty acids can be fed out of balance, what the consequences may look like, and what to look for in monitoring your herd for feedback.
Heavy on Palmitic
When high palmitic fat supplements initially entered the market, they were often fed as a replacement to a calcium salt. Today, most dairies that choose to feed high palm products are feeding them in combination with a calcium salt, which results in feeding a more balanced profile of palmitic and oleic. As a review, palmitic preferentially goes to the mammary gland to make more milkfat, whereas oleic is important for improving digestibility of total fatty acids and supporting body condition. Palmitic and oleic fatty acids both have unique roles…they are not interchangeable.
Let’s walk through a couple of key studies on feeding Palmitic alone in early lactation and the subsequent impact on body condition. First, de Souza and Lock (2019) from Michigan State compared feeding high palmitic to no supplemental fat in the fresh period. While there was no difference in DMI or milk yield in the fresh period, the increase in ECM (+10.3 lb.) was driven by a substantial increase in milkfat percent (+0.41%). At the same time, the high palmitic treatment decreased body weight by 46 pounds, reduced body condition score by 0.09 units and increased body weight loss by 1.67 pounds per day. Sound familiar?
A follow-up study by de Souza and Lock (2021) tested the differences between feeding varying levels of palmitic and oleic by feeding blends of high palmitic prills and traditional ca salts. The three treatments with various palmitic to oleic ratios (80:10, 70:20, 60:30) were compared to a no added fat control diet in the fresh period, followed by all treatments being fed a common diet from day 25 to 63 days postpartum to measure any carryover effects. While there was no significant difference between the fat supplemented treatments on ECM, there were differences in impact on body weight and body condition score. Specifically, increasing oleic and lowering palmitic (from 80:10 to 60:30) had a linear effect of increasing dry matter intakes and decreasing body weight and body condition score losses (figure 1). Interestingly, the carryover data showed that the differences in bodyweight and BCS persisted out into the peak lactation period, despite being on a common diet after the first three weeks.
Figure 1: de Souza, 2021. Effects of timing of palmitic acid supplementation on production responses of early lactation dairy cows
Light on Oleic
Next, let’s talk about oleic…the lesser-known sister fatty acid to palmitic. (I call them sister fatty acids because they are the two main fatty acids in calcium salt fat supplements and have synergistic effects from feeding both). What happens when there’s not enough oleic in early lactation diets? The answer is two-fold: lower digestibility of total fatty acids at the small intestine (aka less energy for the cow) and fewer fatty acids deposited into adipose tissue stores. Let’s first talk about oleic’s digestibility effects and why this matters…
Oleic, which is primarily found in calcium salts and high oleic soybeans, is known for its unique ability to improve digestibility of saturated fatty acids at the small intestine. Specifically, it helps increase the uptake of the less digestible saturated fatty acids (stearic 18:0 and palmitic 16:0) at the small intestine, making more fatty acids and energy available to the cow. While this is important throughout the lactation (for improved feed efficiency), it is critically important in the post-fresh period when cows are often in a caloric deficit and in negative energy balance.
Research done by Prom (2021) showed that increasing the grams of oleic at the small intestine had a linear effect on improving total fatty acid digestibility by +8.4%, with similar increases for both the 18-carbon (+8.6%) and 16-carbon (+8.3%) fatty acids (figure 2). Given these results and other oleic research, a good rule of thumb for calculating target oleic levels at the small intestine is to aim for 60 to 90 grams of oleic or .9 gram/lb. of ECM (absorbed column in ration software).
Figure 2: Prom, 2021. Abomasal infusion of oleic acid increases fatty acid digestibility and plasma insulin of lactating dairy cows.
Secondly, oleic is a bioactive fatty acid that signals for adipose tissue growth…helping cows to maintain more bodyweight post calving. While the dynamics of adipose tissue loss after calving is a hot topic of leading research, what we clearly know is that more is not better! Work done by Carvalho (2014) showed negative impact on embryo development and subsequent pregnancy rates in cows that lost weight after calving vs. those that maintained or gained during that period (figure 3). There’s also recent work by Bradford and Contreras (2023) reviewing the mechanisms of adipose tissue inflammation…resulting from rapid body condition loss post-calving. In essence, rapid loss in adipose tissue sets off a cascade of inflammatory responses that can make cows more insulin resistant, has negative effects on embryo development, and puts cows in a riskier health status with lower immune function.
Figure 3: Carvalho, 2014. Relationships between fertility and postpartum changes in body condition in lactating dairy cows.
Low on EPA/DHA Omega-3
Beyond palmitic and oleic, the third fatty acid group that should be in focus in the fresh period is EPA/DHA omega-3, since it is an essential nutrient for pregnancy and the resolution of inflammation. Consequences of low EPA/DHA are lower conception rates, higher abort rates and a higher <60-day turnover rate. EPA/DHA is directly involved in early embryo growth and elongation, as well as is important for maintaining healthy pregnancies. The latest research from University of Guelph by Madureira (2024) showed that feeding EPA/DHA via calcium salt had direct effects on postpartum inflammation, specifically in the uterine tissue. The results were enhanced endometrial repair and remodeling when cows were fed EPA/DHA from day 2-35, which likely contributed to the increase in first service conception rate.
Earlier work by Freret (2019) showed that just a few grams of EPA/DHA delivered to the small intestine resulted in doubling the blastocyst growth rate of a day-7 embryo, reinforcing the reason it is categorized as essential. EPA/DHA is also responsible for resolving inflammation, thus cows with adequate levels are more resilient to stressors and can recover more quickly.
Practical Guidelines for Fatty Acid Balance
Let’s revisit my client who saw his fresh cows lose more body weight after he switched to feeding 100% palmitic prills in his fresh ration. Thanks to his technology investment, he didn’t have to rely on having a keen eye for body condition changes, rather he had hard numbers to prove it. For the rest of us that don’t have that technology on hand, there are still plenty of ways to monitor early lactation performance to help us better understand the impact of the specific fatty acids we are feeding. Specifically, body condition scoring from pre-fresh to fresh, monitoring NEFAs or BHBAs, and tracking 1st butterfat trends in your herd management software to detect any significant changes in fat mobilization.
Ultimately, feeding the ‘right balance’ of fatty acids for your transition cows requires both science and a bit of art. The ration software models and ChatGPT are not quite good enough to tell us the exact answer, but there’s plenty of science to give us ‘solid rules to balance by’ when it comes to fatty acids.
- Palmitic + Oleic. Feed palmitic and oleic together…always. That is the way nature intended! More palmitic gets absorbed when there’s adequate oleic. And oleic significantly improves total digestibility of stearic too, which is the primary fatty acid the cow relies on for energy.
- Oleic Rule of Thumb. A good rule of thumb for calculating target oleic levels at the small intestine is to aim for between 60 to 90 grams of oleic, or .9 gram/lb. of ECM (absorbed column in ration software).
- Essential Rate of EPA/DHA. EPA/DHA omega-3 should be fed to deliver a minimum of 4.5 grams to the small intestine, which would translate to .066 to .1 lb. of a ca salt with EPA/DHA to meet her essential needs.
- Rumen First! Lastly, if more milk fat is what you’re after, don’t forget that the most important lever you can pull to drive milk fat production is better rumen function. Palmitic certainly has its place, but it cannot meet all the needs of the early lactation cow alone. It is just one of the team of fatty acids that are needed to make milk fat and help your cows thrive in this lactation and the next.
