A little afterbirth snack

Potential motices of the placenta-eating cow   

Placentophagia, the act of eating placenta, is observed in many placental animals including cows. There is no single, definitive reason known for why cows eat their placenta but in searching for the answer we came across four main theories: bonding, hunger, predator avoidance, and instinct. After taking a closer look at the possible reasons why cows eat their placenta we contacted a number of producers, not only cattle but also swine, horse, and sheep producers to discuss what is done with the placenta on the farm and if placentophagia has ever caused any problems.

The idea that a cow eats her placenta as a means of bonding with her calf can probably be rejected. The placenta is released a few minutes to a few hours after the calf is born and it is not usually in contact with the calf. The idea of bonding may have arisen from confusing amniotic fluid which the newborn calf is covered in with the placenta. “Most cows will pay attention to the calf while eating their placenta”, says Murray Warnke, a beef cattle producer from Wetaskiwin, AB. “But some become focused on the placenta and ignore the calf.” In these cases, removing the placenta causes the cow to return her attention to her calf. This, in conjunction with the fact that the placenta is generally not in contact with the calf, opposes the idea of bonding as a reason for cows to eat their placenta.

The second theory, hunger, is divided into two categories: general and specific hunger. General hunger indicates that the cow is just plain hungry after calving. The fact that the placenta is edible, and generally in close proximity to the calf, makes it a convenient meal.

Specific hunger refers to a craving. This theory suggests that there may be something in the placenta, for example nutrients or hormones, that the cow craves post-partum. When asked if he had ever encountered a problem as a result of a cow eating her placenta, Alberta dairy farmer, Alex Beattie, responded that he had never encountered any problems but “some people believe that eating the placenta relaxes the cow and is good for the cow”. If we take into consideration the belief that placentophagia in humans helps prevent post-partum depression, placentophagia in cows may be beneficial to their psychological health and specific hunger may help them to obtain this benefit.

The third and most popular theory for why cows eat their placenta is predator avoidance. Veterinarian Dr. Jennifer Dodd admits that it is not a definite reason but describes it as “a defensive mechanism to ensure that there is no evidence of the birthing in order to protect against predators.”

The idea is that the cow eats her placenta so that the smell does not attract predators towards her and her very vulnerable calf.

The final theory concerning why cows eat their placenta, instinct, is mostly self-explanatory. They just do it, it’s instinctive. Remember, cows were not always domesticated and it is a fact that virtually all placental mammals eat their placenta with the exception of camels, Cetaceans (an order of aquatic mammals including whales and dolphins), and Pinnipeds (an order of semi-aquatic mammals including seals and walruses). Cows eating their placenta are not unique among placental mammals.

 

We corresponded with 16 livestock producers to discuss reasons for leaving or removing the placenta and potential problems resulting from allowing placentophagia. Compared with 17% of cattle producers who said they remove the placenta, 43% of other livestock producers (swine, horses, and sheep) said they remove the placenta; both for similar reasons. Overall, 11 of the producers indicated that they leave the placenta to be eaten for reasons including nutritional value, because it is natural for the animal, and/or because it is impractical to remove. The five producers who do remove the placenta said that they are doing so either to prevent attracting predators, prevent the animal from choking, and/or promote cleanliness and sanitation in the birthing area. Over 80% of the producers indicated that they have never encountered a problem as a direct result of an animal consuming her placenta (note that some of these animals were never exposed to a placenta). However, the remainder indicated encountering problems involving animals choking. In two of these cases, nothing came of the choking, it either righted itself or the producer was there to assist the animal; in the third case, two animals actually choked to death.

Weighing the costs and benefits of allowing a cow to eat her placenta comes down to the producer’s individual situation and experiences. In free-range operations for example it may not be practical to be out monitoring each and every calving in order to remove the placenta. Dr. Dodd says that “there may be some minor nutritional value including proteins in the placenta but the cow will survive well without eating it.” So for those who are choosing to- and able to- regularly remove the placenta, there are no detrimental effects associated with disallowing placentophagia.

So, why do cows eat their placenta? By eliminating bonding as a possible reason we have narrowed it down to three main theories; hunger, predator avoidance, and instinct. Each has its own appeal and all seem equally probable not only as a reason for cows but also for why other mammals eat their placenta. Suffice it to say that some combination of hunger, predator avoidance, and instinct drives cows to partake of the afterbirth snack.