|Herd Hierarchies and Their Effect on Reproduction|
It is natural in the wild for the dominant female and dominant male to mate to ensure the survival of the species. Cattle are no different, they're social animals that operate in large, highly organized groups. Cattle social organizations are shown by two types of relationships, dominance-subordination and preferential. Human reproductive management today is planned resulting in less of a natural hierarchy, but effects of an instinctual hierarchy can still be seen. The purpose of this section is to look at how herd hierarchies effect reproduction in cattle herds.
How is herd hierarchy established and what does it entail?
Cattle have a very strong herd instinct, so their social structure is established at a young age. Young calves develop preferential relationships soon after they are grouped at weaning. Preferential relationships are expressed through positive interactions such as mutual grooming. Preferential relationships are responsible for the cohesion of the group and help to calm social tensions. These relationships are key to the herd instinct, which in the wild is important to the success of each member of the herd.
The characteristics of the dominance relationship are also developing when calves are very young. The calves create a hierarchy of that is expressed through agonistic interactions, which are offensive and defensive. This is very noticeable during feeding times. The older and bigger animals tend to be the ones who get the preferred spot at the bunk and eat the most. This will lead to increase growth rate of the animals that are dominant and will lead to more dominance because they are gaining a size advantage.
The behavior of dominant versus subordinate individuals
The animals that have raised themselves high to social standing get to the feed first and use brute force to do that. To be able to maintain dominance, the animal requires an advantage in size, usually attributed to age. The older, larger animals are the ones that dominate the herd. These animals can physically move smaller animals. The smaller animals are forced to move to another part of the bunk. They often move down the line moving animals that are lower than them on the social structure until the lowest animal is forced to move to a vacant part of the bunk.
If a new animal is added to the current herd, you see the highly ranked animals test the new animal until the new animal finds a spot in the hierarchy. In relation to reproduction, when an animal is in estrus they will exhibit a “heat”. They often butt heads and ‘fight' with other animals. The animal in estrus is trying to compare her self against the other cows in effort to attract a bull. In a natural setting, the dominant male breeds the dominant female. Thus, the cows in estrus attempt to show their dominance.
As individuals show heat they try to increase their standing, but this is not permanent. After an animal becomes pregnant and as pregnancy progresses they decrease their aggressiveness toward other animals. They still are part of the hierarchy, but are much more mild mannered and exhibit fewer aggressive actions.
There also are many factors that affect how dominant an animal is. Dominance has a lot to do with genetics and how dominant the dam was, but not entirely. With genetics comes attitude and size, which might be the two biggest determiners of dominance. These two traits are important and could help predict the dominance of a calf. There are other factors that can play a roll if present. First, cattle with horns tend to be more aggressive and dominant. The animal learns to use the horn, in turn becoming more aggressive and dominant.
Human effect on dominance
In cattle there are a lot of hierarchical interactions to observe, even though humans interfere with natural social hierarchy formation quite a bit. Over the years there has been such high selection intensity for bulls that almost all dairy farms don't even have a bull. Most dairy cows will never even see a bull in their lifetime, which could lessen there expression of dominant characteristics. Many beef farms still have the impact of a bull, but they usually don't let them interact normally. They used planned breeding and the animals are not penned together for most of the year. The herd hierarchy can effect how animals show estrus. For example, the dominant animals may show more signs of estrus because they are the dominant head of the herd. The more submissive animals may not show heat as strongly or in the presence of more dominant females, because the dominant animal intimidates and stresses the animal from showing normal signs of heat.