2012-01-14 / Outdoors

‘Doe’ health affects antler growth, health of offspring

Last week I succeeded in getting a deer within my flintlock’s sights. The hunt was nothing too exciting to write about, but the physical condition of the old doe was noteworthy. Surprisingly, for a year with little food in the woods she was incredibly fat.

Fat layers were over an inch on her rump and around her ribs and belly. Inside her body, fat was packed around her organs. For a deer, this is a sign that she was incredibly healthy.

She was taken in a small agricultural area where a large group of does and fawns have been feeding nightly since August. They have had an abundant supply of clover that is intermixed throughout the hayfields. Additionally, they have been feeding heavily on cover crops of oats, winter rye, and groundhog radishes.

Unfortunately, in most areas I doubt the deer are in such excellent health this year. The good news is that thus far our winter has been extremely mild.

Nutritional health during pregnancy is especially important. Healthy, heavier does have higher fawn survival rates. Fawns born to nutritionally deficient mothers are normally small spikes as yearlings, while those born to healthy mothers often achieve small six- and eight-point racks as yearlings.

Recent research conducted in South Dakota is showing that whitetail bucks born to nutritionally deficient mothers will most likely never reach their genetic potential for antler growth, despite having excellent nutrition later in life.

The research was conducted by South Dakota State University and involved comparing fawns from the Black Hills, an area of poor habitat, with fawns from agricultural areas in eastern South Dakota.

Fawns were captured in the wild from both areas and raised their whole lives in the research facility while being fed high-nutrition forage on an unlimited basis. As a result, both study groups were in excellent nutritional condition.

The buck fawns from good habitat achieved antler sizes throughout their lives the same on average as buck fawns in the wild from this area. Bucks from the Black Hills also achieved on average the same-size racks as wild bucks of their age class in the Black Hills, despite achieving heavier body weights with the high nutrition diet.

On average, the antlers of the bucks from the good habitat area were about 27 percent larger than their counterparts, despite both groups being fed the same diet. Interestingly, the Black Hills bucks ceased their rapid antler growth forty-one days earlier than the bucks that had originated in eastern South Dakota.

Looking at these results, it would be easy to say that the difference was due to better antler genetics in bucks from eastern South Dakota. However, a surprise came while studying second-generation bucks.

Second-generation bucks were born to females that had also been captured as fawns in the wild from both areas. These females were raised in the research facility and bred by the first-generation bucks from each of their respective study areas. They had excellent nutrition and were in top physical health during their pregnancies.

There was not any significant change between the rack sizes of the second-generation eastern South Dakota bucks compared to the first generation and wild bucks from that area. However, the racks of second-generation bucks from the Black Hills achieved much larger racks than the first-generation and wild bucks from that area. The antler growth of these bucks caught up to those from eastern South Dakota. In the second generation, the two groups on average developed statistically similar large racks.

With all other factors being the same, the researchers determined that the main factor was the nutritional health of the buck’s mother during her pregnancy. Bucks born to does in poor nutritional condition will most likely never reach their genetic antler potential during their lives, even though they may experience excellent nutrition later in life.

This finding emphasizes the importance of nutrition, a direct result of the habitat quality.

Why do bucks born to nutritionally deficient does under-perform their entire lives, despite themselves having good nutrition? The researchers involved in this study believe that stress hormones in the doe’s body during gestation have lifelong consequences on her fawn’s hormone production, which can negatively affect its growth and reproduction.

Researchers found higher levels of the stress hormone cortisol in the bodies of the firstgeneration Black Hills whitetails throughout their lives.

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