Lecture 9: Reproductive Toxicants and induced abortion

- poison hemlock

- lupine

- tree tobacco

- skunk cabbage

What plants cause teratogenesis in cattle?

- nitrates (johnson, sudan, oat, wheat, corn)

- ponderosa pine

- locoweed

- broomweed

What plants cause abortions in cattle?

- locoweed

- fescue

What plants cause infertility in cattle?

- johnson grass

- sudan grass

- oats

- wheat

- corn

What are examples of plants that have high nitrate accumulation?

- in times of drought since not a lot of food available

When do you see problems with nitrate?

- fetal hypoxia and death

- late gestation abortion

- methemoglobinemia

What do you see when cattle consume plants with high levels of nitrates?

- produce isocupressic acid

- vasoconstriction at caruncles --> hemorrhagic placentitis

- 50% absorption rate in those that eat the needle

How does ponderosa pine impact cattle?

- locoweed

What toxic plant causes the most economic loss in cattle?

- neurologic signs

- abortion (up to 40% of them)

- fetal abnormalities - hydrops/arthrogryoposis

Locoweeds toxic agent is swainsonine. What is seen in cattle the digest this plant?

- abortion and retained fetal membranes commonly in the spring due to mono and di-terpenes

How does broomweed or snakeweed impact cattle?

- becomes infected with neotyphodium coenophialum, which produces ergovaline (toxic alkaloid)

Why is fescue toxic?

- peripheral vasoconstriction --> fescue foot

- decreased reproductive efficiency/infertility = summer slump

- fat necrosis

What are the impacts of ergovaline from fescue in cattle?

- embryo does not develop even when fertilized with semen

What is summer slump caused by fescue in cattle?

- rotate off fescue in the summer

- re-plant pastures

- avoid seedhead grazing = mow or heavily graze to avoid seed pod stage

How can you help prevent cows from eating fescue?

- accidental breeding of young heifer

- pregnancy in feedlot heifer

- fetal maceration

- fetal mummification

- hydrops conditions -> fluid associated with fetus placenta

Why would you induce abortions in cattle?

- corpus luteum from ovulation until term

- placenta from day 150 - 250 of gestation

What are the progesterone sources in cattle?

- progesterone, based on stage you can know where to target

What hormone do we want to target to induce abortion in cattle?

- Prostaglandin F2a like dinoprost and cloprostenol (rids CL and the progesterone source)

- corticosteroids like dexamethasone (placenta progesterone source)

What are therapeutic options for terminating pregnancies in cattle?

- causes luteolysis to get rid of CL and its production of progesterone

How does PGF2a lead to abortions in cattle?

- reduce placental progesterone production

How do corticosteroids cause abortions in cattle?

- single injection of PGF2a

(will occur in 5-7 days and fertile estrus = 3-5 days later)

How do you cause an abortion in a fetus that is from 5-150 days of gestation?

- manually disrupt preg by roughing up the fetus

- may take weeks and can be hard to do

How do you cause an abortion in a fetus that is from 30-120 days of gestation?

- corticosteroids (dexmeth) and PGF2a since need to remove both sources of progesterone

How do you cause an abortion in a fetus that is from 150-240 days of gestation?

- increase change of a retained placenta in 80% of cows

What can abortion after 120 increase?