Lactating Dairy Cow Nutrition and Energy Balance

Question 1

describe the symbiosis between cow and rumen microbes?

Answer 1

rumen microbes get a home and food, cow gets to eat microbes and use their waste products for energy

Question 2

what are the 4 products of ruminal fermentation?

Answer 2

1. volatile fatty acids: acetate, proprionate, and butyrate, absorbed across rumen wall and provide energy
2. dead bacteria: enter small intestine and provide protein
3. vitamins: B1 and B12
4. gasses: CO2, CH4, NH3, H2S

Question 3

describe the 3 VFAs

Answer 3

1. acetate: the primary VFA produced by digestion of fiber, used for milk fat synthesis
2. proprionate: a 3 carbon VFA good for making glucose, converted to glucose in the liver and then lactose in the mammary gland
3. butyrate: energy source for GI mucosa, but excess leads to hyperketonemia (beta-hydroxybutryic acid)

Question 4

what are the 4 options for feeding dairy cattle?

Answer 4

1. grazing: mainly low energy and protein
2. component feeding: feed ingredients separately (forage and grain)
3. TMR: total mixed ration, every bite should be the same, most commonly used on commercial dairies, doesn’t let cows make bad choices and matches nutritional needs of cows in a GROUP
4. PMR: partial mixed ration, example is use of robotic milkers to feed grain pellets during milking

Question 5

how is a TMR formulated? (3)

Answer 5

1. by hand, calculator, or a model (model is best)
2. mix ingredients to achieve right blend of nutrients by consulting NRC
3. adjust based on nutritionist recommendation

Question 6

what is necessary knowledge when formulating a TMR? (2)

Answer 6

1. who are we feeding? nutrient needs change across age and stage of lactation
2. how big is the dinner plate? must fit all nutrients within her feed intake (DMI)

Question 7

what are the 5 steps to formulating a ration/feeding the rumen?

Answer 7

1. make a home for the bacteria: support rumen stability with fiber and support acetate production
2. feed the bacteria energy: with non-fiber carbohydrates like starches and sugars to support proprionate production
3. give bacteria protein so they can reproduce
4. add fats if the cow needs more energy: but not too much! rumen hates fat
5. adjust minerals and vitamins: Ca, P, microminerals, etc.

Question 8

what are the 4 sources of energy for a cow?

Answer 8

1. glucose: ruminants do not absorb glucose!! must be synthesized in the liver to be used by the cow, using proprionate as the primary ingredient
2. fat oxidation
3. ketone bodies
4. muscle breakdown

Question 9

describe the transition to the peripartum period (4)

Answer 9

1. occurs 60 days before calving and 30 days after calving
2. from lactating and pregnant
3. to non-lactating and pregnant
4. to lactating and not pregnant

Question 10

what are challenges associated with the transition period in cattle?

Answer 10

parturition, social change, hormonal change, diet changes, and metabolic changes can result in a negative energy, calcium, protein, and vitamin balance

Question 11

what happens to feed intake right before a cow calves in? what can this result in?

Answer 11

there is a natural drop in feed intake because the baby is so big that the rumen doesn’t have room to expand; this can lead to a negative energy balance, causing the cow to melt fat for energy

Question 12

what happens to nutrient requirements right before a cow calves in?

Answer 12

there is a rapid and extreme increase in nutrient requirements, which paired with her decreased food intake can cause increased fat mobilization to support metabolic needs

Question 13

describe fat mobilization (4)

Answer 13

1. fat is stored as triglycerides (glycerol + 3 NEFAs)
2. fat is broken down by hormone sensitive lipase
3. the NEFAs travel to the tissues for energy, to the mammary gland for milk fat synthesis, and are exported as VLDLs to the liver, where they can either be stored, resulting in fatty liver disease if excess, or used for energy, either via beta-oxidation OR by incomplete beta-oxidation, which results in accumulation of ketones
4. basically too much fat mobilization can result in fatty liver and increased ketones (some is normal and adaptive, too much is bad)

Question 14

what does serum NEFA represent? what is higher pre-partum serum NEFA correlated with? (4)

Answer 14

mobilized fat

higher pre-partum serum NEFA correlated with
1. higher post-partum serum NEFA
2. higher post-partum serum ketones
3. more disease
4. lower milk production

Question 15

describe the risks of overconditioned animals periparturition?

Answer 15

overconditioned animals have a larger drop in feed intake around parturition, so must mobilize more fat; they also have more omental fat, and venous drainage of the GI tract goes through the portal vein to the liver, putting them at greater risk for hepatic lipidosis

Question 16

what are 5 ways to prevent metabolic disease in cows around parturition

Answer 16

1. prevent obesity with a controlled long term energy balance
2. proper diets pre and post partum
3. proper feed availability and access
4. manage other risk factors like calcium balance and dystocia
5. early intervention