Recently I was talking to a group of land stewards that were touring the ranch in Australia where I was a guest. The end of the tour found the group across the fence from a herd of two thousand cows with calves. The landowners asked me if I would spend a few minutes going over a few of the concepts that we had been talking about the previous two days.
I did not have much time; however, I wanted to touch on phenotype and hormonal activity and how they positively or negatively impacted fertility in the herd.
Starting off with phenotype (or shape) was easy with so many examples just across the fence. A “wedge” shape cow is the most fertile for many reasons. Starting with the shoulders (small part of the wedge), she should be shorter here on the topside than at the hook bones. Hmmm? Sex hormones shut off long-bone growth. The earlier in life and the more estrogen a heifer calf is producing, the more she should look like she is walking downhill while traveling on level ground. From the side view this would create the top part of the wedge.
On the bottom side, the heart girth (taken around the smallest circumference behind the front leg) should be equal to the topline (measured from pin bone to poll). To give the cow (or heifer) a wedge look, her flank circumference needs to be larger than the girth measurement by a minimum of two inches, but a plus four-inch, six-inch, or eight-inch flank is even better. Kenneth Redman of Sydney, Montana (406-480-2312) found in his analysis that old cows typically had larger flanks than the herd average, meaning that they could “digest enough for three” even during the poor, dry years. This larger flank gives the look of an ever-increasing wedge towards the rear of the cow from a side view.
Moving to the rump of the cow, she needs to have a rump at least two and a half inches wider than it is long. The length is measured from the back of the pin bones to the front of the hook bones. The width is measured at the widest part of the rump area (usually the stifle muscle on each side). Michael McDonald of Nebraska (God rest his soul) found that the best indicator of fertility in a cow or heifer was how much wider the rump was than its length. Kenneth Redman found that those old cows that had given us ten calves in a row had a wider rump than the average cow in the herd. With this wide rump, a view from the top of the cow is going to also give us a wedge-shaped look.
At that point the group had an idea of the shape of a replacement heifer that is in the ballpark with her phenotype. Next, my explanation turned to hormonal activity and butterfat. That short leg up front was created by high production of estrogen. Two other places we would see early estrogen expression is in hairs standing up in the adrenal whorl and the stifle muscle developing early. In most cases, higher hormonal activity is expressed in an early-shedding animal with a uniform haircoat. If your heifers all shed late and have hair sticking every which direction, it is time to take a serious look at the feed and mineral quality provided to your animals.
The bare backs I alluded to in the title is a reference to early shedding. Dr. Jan Bonsma said that if he could use only one of all of the indicators he knew for selecting which animal he would eat that year, it would be the one that shed its winter haircoat the earliest. That animal had the best glandular function in her environment and would be the most healthful for him to eat. We can use this to our advantage IF we start observing what we look at. That early-shedding heifer will typically have fewer flies than her herdmates. She will maintain body condition easier/better. One of the big keys to heifers and cows getting pregnant is the ability to gain weight between calving and breeding. That bred replacement heifer must be able to eat enough for two. Late shedding first calf heifers typically are the ones who breed back late or come up open in the fall. Part of this is glandular function, but in a number of cases it is related to a phenotype that hinders the heifers ability to gain weight during lactation before joining her with the bull.
Butterfat in the heifer can be observed in a number of ways the day she is born (These are not listed in order of importance): 1) an adrenal hair whorl located in the shoulder blade area or further forward, 2) extra teats, 3) an area around the teats that has shorter, nappy, lighter hair color than the rest of her body, a precursor to a bald udder later in life, 4) the correct outline of her escutcheon showing high butterfat when she is milking, 5) the presence of vertical folds in the hide, and 6) a small diameter cannon bone and a pointed poll. In the mature cow, a bald udder is the number one indicator of butterfat. The more of the previously enumerated characteristics we see, the more likely we are to have a high butterfat-producing cow.
I summarized my talk by saying, “you need a cow with a big belly, a wide butt, a bald udder and a bare back.”
Any one animal might “prove” these comments incorrect. However, one hundred cows with all of these traits will give you more and better-quality calves than one hundred cows that have few or none of these traits. If you have questions or comments, please contact me at 208-315-4726 or by email at firstname.lastname@example.org