What is the number one aspect of nutrition that will affect reproduction?
How much energy does it take to maintain am average cow's normal metabolism and body function?
~10Mcal/day (the remainder of the NEL goes for lactation)
Describe fetal growth during gestation.
- growth of fetus increases more as gestation gets later; fetus growth the most within the final trimester
- more than 50% of the gestation period elapses before the fetus weighs as much as its membranes
When do we usually see the greatest problems with reproductive efficiency on a farm? Why?
- we usually see a drop in conception/ pregnancy rate in the early fall
- 1. cows that were bred in the summer are coming up for preg check and diagnosed open (summer is hard breeding d/t heat stress)
- 2. new forages or the end of last years forages are being fed- end of the storage period and mycotoxins; beginning of storage period and incomplete fermentation or haven't adjusted ration for new forages yet
Describe the effects of heat stress. (5)
- decreased intake
- metabolic adaptations that prevent glucose-sparing mechanisms that normally prevent severe reductions in milk during periods of decreased DMI
- drop in milk
- weight loss
- elevated NEFAs
What are feeding guidelines to minimize the impact of heat stress? (4)
- adequate cooling and ventilation in housing and over feed bunk (don't get the feed wet)
- increase dietary energy density: increase grain while maintaining adequate fiber and particle size, +/- feed supplemental fat
- increase mineral concentrations (K, Na, Mg)
- feed additives: buffers, yeast (to keep rumen pH up while on added grain)
What are nutritional ways to increase dietary energy density in the summer? (4)
- ******getting them to eat more DMI
- improve forage quality and digestibility
- increase concentrate/ grain in the diet
- supplemental fat
How is energy balance important in reproduction?
cows are usually in negative energy balance for 6-8 weeks after calving; cow will start cycling ~10 days after nadir energy balance
What is the goal for days in milk at first breeding?
we want 80% of the cows bred by 81 days in milk
__________ negative energy balance leads to __________ days to first ovulation.
Describe how we monitor body condition.
BCS: should not lose more than 1 BCS in early lactation
What are sources of linoleic acid in common feeds? What are some other sources of linoleic acid? (5)
- soybeans!!!!- and have high fat!
- corn- low fat :(
- safflower oil
- sunflower oil
What and how do long chain fatty acids affect repro in the pre-breeding period? (3)
- [linoleic acid- omega-6]
- sparing glucose--> positive effects on energy signaling to the hypothalamus--> LH--> ovulation
- increased prostaglandin--> uterine involution
- long chain fatty acids in pre-breeding period to increase conception
What and how do long chain fatty acids affect repro in the breeding period? (4)
- [EPA, DHA- omega-3s]
- anti-inflammatory, reduce lutelytic peaks to maintain CL
- inhibit estradiol production, which plays a role in making the CL sensitive to prostaglandin (maintain CL after breeding)
- CL is cholesterol enriched, LCFA may help maintain CL
- feed post-breeding to decrease EED
What is a potential downside to feeding supplemental fat?
- feeding too much unsaturated fat can limit fiber digestibility, reduce rate of passage, and reduce intake
- supplemental fats are also more expensive (it's more cost effective to improve forage quality and increase grain)
What type of fats has been proven to be effective when fed in the breeding period?
fish oil= omega-3's (EPA, DHA)
What type of fats has been proven to be effective when fed in the pre-breeding period?
linoleic acid= omega-6
How can we gauge protein absorption by the animal?
- measure blood/plasma urea nitrogen or milk urea nitrogen
- we feed a lot of degradable protein, leading to high rumen ammonia, which is absorbed by the liver--> liver metabolized it to urea, which is secreted in the milk or urine
How do you calculate protein in feed?
N x 6.25 <-- this is crude protein
Define rumen degradable protein.
- degradable protein is used by rumen microbes to convert feed nutrients to microbial protein
- comes in the form of Non-protein Nitrogen or True protein
- supplies the rumen microbes with amino acids or peptides
A deficiency in RDP would result in...
- reduced carbohydrate digestion, VFA and microbial protein production.
- This would decrease animal performance.
Define rumen undegradable protein.
the portion of intake protein that escapes rumen degradation and is digested directly in the small intestine.
Describe the effects high CP has on reproduction. (3)
- local toxic effect on sperm, ova, or embryo (high MUN--> high ammonia in the uterine body)
- reduce LH binding to ovarian receptors, leading to a decrease is serum progesterone
- immune suppression
How does protein differ in grazing herds?
MUN will be higher because the degradability of the protein in pasture is really high; you just have to tolerate this
What are desirable MUN levels, and why?
- Goal MUN around 10-12
- MUN> 14 means we are spending too much on protein, not getting enough benefit from it, and potentially having negative reproductive side effects (she's just peeing it all out, putting it in her milk etc)
Describe the relationship between MUN and blood/ plasma UN.
good correlation- you an use either one to gauge protein usage; plasma/ blood UN will always be a little higher than MUN
What are the % of Ca, K, Mg, Cu in typical lactating diets?
- Ca 0.8-1%
- K 1.2-1.5%
- Mg 0.25-0.3%
- Cu 15-20ppm
How much Se can we legally supplement?
- Se-yeast- pre-fresh
- selenite/selenate- lactating
***What is the recommended daily Vit E in a fresh/ lactating cow diet? In a dry cow diet?
- Fresh/ lactating- ~500IU/d
- Dry- 1000-2000IU/d
Why do we care about vitamins and minerals for reproduction?
affect smooth muscle function- uterine involution, passage of the placenta, etc
What is the optimum urine pH on a DCAD diet for Holsteins? For Jerseys?
- Holsteins 6-6.5
- Jerseys 5.8-6.2
What minerals are given as part of a DCAD diet?
- Calcium chloride
- Calcium sulfate
- Magnesium chloride
- Magnesium sulfate
- Ammonium chloride
- Ammonium sulfate
What should the Ca:P ratio be in feed? What is an appropriate % of Ph in a diet?