Fat continues to be an important consideration in the diet of dairy cows. Recognizing its role as a key macronutrient is essential, and the requirements to meet the needs of animals for optimal milk production have long been established, as stated in a study cited by DairyGlobal.

The Importance of Amino Acids

However, just as amino acids are a key element of protein nutrition, fatty acids are the key element in "fat" nutrition, and the industry continues to be informed by research data regarding the specific effects of individual fatty acids when supplemented in the diets of dairy cows and how to implement these findings on the farm.

In this regard, a new batch of research data on various aspects of fatty acid nutrition was presented at the recent annual conference of the American Dairy Science Association, which took place this year in Ottawa, Canada.

There continues to be a primary interest in developing knowledge and understanding the use and effects of palmitic acid (C16:0) and oleic acid (C18:1) and their mixtures when included in milk diets, as well as a continuous focus on potential mechanisms to improve fat digestibility.

Other areas that received attention included recognizing the role and potential benefits of omega-3 fatty acids and using fatty acid supplements to modify the functionality of dairy products. A summary of some key findings from the conference is presented below.

Research on Palmitic Acid

High-C16:0 supplements are among the most commonly used in the industry, and research in recent years has increased our understanding of how this fatty acid influences production and metabolism, especially by stimulating milk fat production and altering nutrient partitioning. These findings have led to more specific recommendations for use in lactation diets.

• The effects of a high-C16:0 supplement included at 2% of dry matter (DM) in the diet and a diet lowering milk fat were evaluated in Professor Harvatine's laboratory at Penn State University. No dietary treatment altered milk production compared to cows provided the Control diet; however, milk fat increased by 0.3% with the addition of C16:0, compared to a decrease of 1.35% when cows were given the milk fat-depressing diet.
• The seasonal effect on the response to high-C16 (included at 1.45% of DM fed) supplements was evaluated in a meta-analysis study from Professor Lock's laboratory at Michigan State University and Dairy Australia. Overall, C16:0 supplementation increased milk production by 1.18 kg/day, milk fat by 0.08 kg/day, and milk fat concentration by 0.10%.

However, a significant seasonal response was recorded, with milk production increasing by 3.02 kg/day and milk fat-corrected with 3.63 kg/day in the summer period, compared to the control diet (unsupplemented). These data provide clear evidence of beneficial responses to production through C16:0 supplementation, but highlight specific benefits to milk production and milk fat when used in warmer weather periods.

• The increase in C16:0 supplements has been linked to increased ceramide production in previous studies, which can modify insulin resistance in adipose tissue and influence nutrient partitioning in dairy cows.

Another study from Penn State University reported that including C16:0 in a milk diet at 1.95% of DM significantly increased plasma ceramide concentration and milk fat increased by 0.5%, while the inclusion of stearic acid (C18:0) had no significant effects on these parameters.

These data support the concept that differences in nutrient partitioning, milk fat production, and body weight gain associated with C16:0 supplementation may be influenced by ceramide signaling modifications.

• The short-term effects of palmitic and stearic acid supplementation with an increased supplement feeding rate every 4 days from 0 to 150, 300, 500, and 750 g/day were the subject of further study at Penn State University. Neither C16:0 nor C18:0 increased milk production, but the increase in C16:0 progressively increased milk production and fat concentration, being 0.37% higher than the control group at the 500 g/day supplement level.

No fatty acid treatment seemed to reach a plateau response even at the highest supplement addition level, indicating the potential for cows to continue to respond to increasing doses of C16:0 beyond those evaluated.

• Increasing the concentration of C16:0 in calcium salt supplements from 35 to 50, 65, and 80%, with constant oleic acid and variable stearic acid, was evaluated in a study at the University of Illinois, Urbana, with supplements added at 2% of DM diet. The highest milk production was recorded with the 65% C16:0 supplement, and milk fat corrected linearly with increasing C16:0 concentration. Milk fat concentration was highest at the 65% C16:0 concentration (4.34% compared to 3.95% in the control group).
• Supplementing dairy cows with fat supplements containing 59 to 73% palmitic acid increased milk yield of multiparous cows from 41.1 to 43.3 kg/day and milk fat yield from 1.44 to 1.52 kg/day regardless of parity, compared to low-fat diets, in other data reported by Penn State University.

Oleic Acid

Unlike the effects of C16:0, recent research data suggest that oleic acid promotes insulin sensitivity in adipose tissue and reduces lipolysis.

• Further evidence of the lipogenic effects of oleic acid was presented by Michigan State University in a study using adipocytes cultured with palmitic and/or oleic acids, concluding that increased lipid accumulation and adipogenesis observed with certain fatty acid cultures provide justification for using oleic acid during the periparturient period to enhance lipid accumulation.

Palmitic/Oleic Mixtures

In recent years, there has been increased interest and research activity in supplementing variable mixtures of palmitic and oleic fatty acids, and this theme continued in the current conference findings.

• Michigan State University evaluated the response of cows offered a calcium salt supplement of 70% C16:0 – 20% C18:1, evaluated at 22 or 28% dietary starch concentration, from days 1 to 24 of lactation. The study reported higher milk yield as a response to increased starch concentration and higher milk fat concentration as a response to fat supplementation, the latter increasing by 0.26% and 0.23% in low-starch and high-starch diets, respectively.
• The effects of a calcium salt formulation of 60% C16:0 – 30% C18:1 offered to peak-producing dairy cows were reported by Michigan State University in a parity comparison under warm weather conditions. Supplementing diets with 1.8% fatty acids per kg of body weight increased milk production by 2.1 kg/day and increased milk fat production in multiparous cows but not in primiparous cows.

A similar formulation was evaluated in a study at the University of Hiroshima, reporting a milk production response of up to 5.1 kg/day for cows early supplemented with 300 g/day of fat supplement.

• Increasing the concentration of C16:0 in calcium salt supplements was the subject of Israeli work comparing milk production of cows offered a more traditional calcium salt formulation (45% C16:0 – 35% C18:1) with that of cows offered 60:30 palmitic-oleic mixtures and 70:20 palmitic-oleic mixtures. This study reported the highest milk yield in the more traditional supplements and higher milk fat yields in the higher C16:0 supplements (3.55, 3.94, and 3.87%, respectively).

Lecithin/Lysophospholipids

The potential to increase fatty acid digestibility using natural emulsifiers was also a theme at the conference.

• A study from Ohio State University evaluated the effect of lysophospholipids added to diets containing high palmitic or high stearic acid supplements, reporting improvements in total fatty acid digestibility in diets where a high stearic acid supplement was used. The study also provided additional support for the beneficial effect of palmitic acid on NDF digestibility (+2.6%).
• A study from Cornell University using abomasal infusions of soy or sunflower lecithin sources did not report significant effects on fat digestibility in the diet, although cows treated with sunflower lecithin produced more milk.

Omega-3 Fatty Acids

Interest in the effects of essential omega-3 fatty acids continues in the industry.

• Research from the University of Guelph reported a small beneficial effect on the inflammatory response when dairy cows were exposed to a lipopolysaccharide challenge when provided a calcium salt supplement of fish oil after calving.
• Dr. Moallem from the Volcani Institute in Israel summarized a series of studies highlighting the selective absorption of omega-3 fatty acids in ovarian compartments and sperm, exerting a positive influence on fertility. The presented data also concluded that beneficial effects could be obtained from α-linolenic acid (C18:3), typically found in flaxseed and grazed pasture, and not just from long-chain omega-3 from fish oil.

Cottonseed

• The Michigan State group presented data from studies evaluating the increasing inclusion of whole cottonseeds in the diet from 0 to 8, 16, and 24% of DM fed. Increases in milk production (up to 2.0 kg/day) and milk fat (up to 0.11 kg/day) were reported with up to 16% cottonseed inclusion, but dry matter intake and milk production were reduced at a 24% inclusion rate.

This extensive body of research on fatty acid nutrition adds to our developing knowledge of the effects and roles of different fatty acid formulations in dairy product nutrition and, more importantly, helps guide our thinking and advice to producers at the farm level.