Theriogenology – Problems of Pregnancy Practice Test

When a dairy cow is late in gestation, the fetus has a very high energy demand. If the cow’s intake doesn’t meet this need, she goes into negative energy balance and starts mobilizing body fat. This fat mobilization raises circulating non-esterified fatty acids and ketone bodies. These metabolic byproducts can cross to the fetus and create an energy shortfall for fetal tissues, leading to fetal growth restriction or fetal death, which raises the risk of abortion. Ketosis is a marker of this energy shortfall and can also impair immune function and placental efficiency, further increasing abortion risk.

Improving nutrition during late gestation lowers the extent of lipolysis, reduces NEFA and ketone levels, and stabilizes blood glucose and insulin. With a more favorable energy balance, the fetus is exposed to less metabolic stress, growth proceeds more normally, and the likelihood of abortion decreases.

Notes on the other options: negative energy balance does not cause fat to accumulate; it drives fat mobilization. Ketosis does not improve fetal growth; it signals energy deficit and can harm the fetus. And energy balance certainly influences abortion risk, so saying it has no effect isn't correct.