Nutrition Exam 1: Lipids

What is the structure of a lipid?

Lipids, or triglycerides, consist of a glycerol backbone attached to 3 fatty acids

These can be saturated (no double bonds) or unsaturated (with double bonds)
Lipase is the enzyme responsible for breaking down lipids by cleaving ester bonds between glycerol and fatty acids

Lipid digestion in monogastrics

Lipid digestion begins in the mouth with salivary lipase and continues in the stomach, where bile salts emulsify fats. Free fatty acids are absorbed in the small intestine, where micelles transport them into intestinal cells, and chylomicrons transport them into the lymphatic system

Lipid digestion in ruminants

Ruminants differ in their ability to digest fats. Rumen microbes don’t handle high levels of fat well, and excess fat can disrupt fermentation in the rumen

What is biohydrogenation?

Rumen microbes convert unsaturated fatty acids into saturated fatty acids by adding hydrogen, which reduces the availability of essential fatty acids like linoleic (Omega-6) and linolenic (Omega-3) acids

What are protected lipid sources?

To ensure essential fatty acids reach the small intestine without being altered by biohydrogenation, companies produce protected lipid supplements (i.e. “Mega-Lac” calcium salts)

These products ensure that animals, particularly cows, receive the needed essential fatty acids without rumen interference

What is lipid metabolism?

Lipogenesis (fat synthesis) and lipolysis (fat breakdown) are critical processes. Fat is stored in the body and broken down during energy-demanding periods, such as lactation or weaning in calves

Fatty acids are transported via albumin in the blood after being mobilized from fat tissue during stress or energy deficiency

What is ketosis?

A metabolic disorder in ruminants that occurs during periods of high energy demand, particularly early lactation or late pregnancy, when the animal cannot consume enough energy. This leads to excessive fat mobilization, resulting in high levels of ketone bodies in the blood

Symptoms include reduced appetite, lethargy, and the characteristic vinegar-like breath odor. Ketosis is treated with IV dextrose and propylene glycol

Practical application of lipids

Ruminants need balanced fat inclusion in their diets. Too much fat negatively impacts rumen fermentation

Lipid supplements are often added to meet the high energy needs of lactating animals, but fat inclusion must be carefully managed

Unique challenges of lipid digestion in ruminants

Ruminants have evolved to consume forages, which are low in fat, so their digestive system is less efficient at handling high-fat diets

Excess fat in the diet can negatively affect digestion in the rumen, limiting fat inclusion in ruminant diets

What are the two key essential fatty acids?

Linoleic Acid (18:2 Omega-6)- essential for animals but must be included in the diet

Linolenic Acid (18:3 Omega-3)- another essential fatty acid. Both can be converted to non-essential forms due to biohydrogenation

What are micelles responsible for?

Transporting fatty acids across the intestinal lining

Inside the cells, fatty acids are reassembled into triglycerides and transported by chylomicrons into the lymphatic system

What are chylomicrons responsible for?

Transport triglycerides from the intestine to the liver and the rest of the body

What is lipolysis?

(Fat Breakdown)

Stored fat (triglycerides) is broken down into glycerol and fatty acids during
periods of stress or energy demand, such as lactation or weaning in calves

Fatty acids released from fat tissues are transported in the blood via
albumin

Why is energy needed during lactation?

Lipids are added to diets to meet the high energy demands of lactating cows

Lipids provide more energy (9 kcal/g) compared to carbohydrates (4 kcal/g),
helping cows meet their energy needs despite reduced feed intake