Last month, we discussed a common misconception among "environmentalists" - that only domestic livestock overgraze. That is most emphatically not true.
There is just so much grazing a rangeland will support, and it makes no difference what the grazing animal is. Exceed that limit and animals must either be removed, or they die. In national parks, where hunting or "cropping" is not allowed, many wild animals die of starvation.
Many environmentalists consider this as "natural." Most environmentalists also do not believe wild animals require supplementation. Indeed, within our own industry there are a great many ranchers who also believe this.
At one point, a famous range management consultant was even telling his clients to withhold supplementation as a means of developing their cattle herds in a manner similar to wild animals (that do not require supplementary nutrients). The result was 60% calf crops.
In tropical South America where cattle have been bred for over 100 years without supplementation, calf crops average about 50%. Breed-back on first calf heifers is only about 10%.
The reality is that it is not possible to breed cattle that do not require supplementation. Likewise, it is a myth that wild animals do not respond to supplementation.
In drought years, fawn crops can be only 20-30% of a normal year. When forage is dry and mature, it does not provide adequate energy (and in most cases phosphorous) for grazing animals to reproduce. It makes no difference whether the animal is wild or domestic, without adequate nutrition, reproduction will be impaired.
Fortunately, in terms of the total amount of supplement, it usually doesn't take very much. In most cases, a pound or two of a high protein supplement is all that's required.
What's interesting is that while energy is required to initiate estrus, in terms of supplementation, protein is the key. The reason is that whenever we feed a ruminant, there are two nutrient requirements to consider - the animal itself and the rumen microorganisms.
Dry mature forage will typically only have 5-7% crude protein. Rumen micro-organisms require roughly 10% in order to divide (reproduce) at an optimum rate. Unsupplemented, the rumen microorganism population declines. Since it is they, and not the animal that digest fiber, fiber digestion will decline as well.
A small amount of protein allows the microorganism to reproduce at a normal rate. In turn, fiber digestion is enhanced. This means that the animal can eat more forage, thereby increasing the amount of energy to the animal.
How much energy is required? For estrus to occur, it takes enough energy for the animal to be in what is known as a "positive energy balance." In other words, she must be gaining weight. For extremely coarse grasses, a small amount of grain may be necessary in addition to protein. It should still be realized, however, that the protein effect is by making more energy available.
Why energy has such a profound effect has been somewhat of a mystery. When the truth is known, I will bet it is a function of leptin.
As we discussed in a previous column, "Revolutionary Discovery" (BEEF, November 1998), leptin is a hormone secreted by fat cells (when they are growing). In that column, we discussed how T-cells (white blood cells which produce antibodies) will not function unless leptin is present.
Ultimately, I am convinced leptin receptor sites will be found on the ovary or pituitary, and will somehow be involved in triggering either GNRH (Gonadatropin Releasing Hormone), estrogen or estrus itself.
Until that is confirmed, we know as a practical matter what it takes to get an animal to cycle. It doesn't matter whether that animal is wild or domestic. It takes supplement.
Wild animals such as deer or elk require less supplement only in that they have the ability to jump fences and raid farmer's fields or hay stacks. Although wildlife agencies often tell us they prefer browse, the reality is that the preferred forage is alfalfa. The deer know what they need, even if environmentalists don't.