System wide risks with "starving a profit" out of the cow herd
As all segments of the cattle industry are affected by the ethanol industry, rising feed and fuel costs, limited irrigation water and increasing weather variability, the immediate response to a challenging year is to limit additional costs for the beef herd.
One viable approach to reducing feed costs is to more closely evaluate calving season, and to better synchronize calving and early lactation with the availability of high quality green grass. This management strategy certainly has the ability to reduce overall costs. But newer research, along with a closer evaluation of studies conducted in the 70’s and 80’s suggests that management of the cow, especially during mid to late gestation and early lactation, may not only impact the initial calving and breed back of the cow herd, but have longer-term impacts on the quality and performance of the subsequent calves produced from those pregnancies.
For decades, we have discussed the importance of cow nutrition during late gestation and the importance of cow body condition scores (BCS) during weaning and calving – using BCS as a barometer to breeding success. Thanks to some mid 70’s research from UW, as well as 80’s research at CSU, we also know the impact of cow nutrition on calf survivability and health. More recently, researchers at Wyoming, Nebraska and North Dakota have taken a closer look at the long term impacts of pregnant and early lactation cow management, and its effect on the calves produced from those pregnancies.
A team of researchers at the University of Wyoming has been investigating the long term impacts of cow management during early to mid-gestation (day 30 through 120), and how it impacts calf development and feedlot performance. Although the size of the fetus is relatively small during this period, it is an important phase, as many of the internal organs, the digestive system and the endocrine system are developed during this period. Current UW studies have been designed to nutritionally stress the pregnant cow during this early stage of gestation, but then allow her to regain lost weight before calving, essentially isolating her nutritional stress to mid-gestation only.
Initial results suggest that steer calves that were stressed during early gestation are born at similar weights to normally managed cows, but closer evaluation shows that gestationally stressed calves have a reduced number of kidney tubules, critical for the blood filtering function of the kidneys. Additionally, similar sheep research indicates that stressed lambs ultimately have higher blood pressure, and higher blood glucose levels suggesting the initial stages of diabetic symptoms.
In cattle, feedlot steers that were gestationally stressed show early signs of cardiac stress through increased heart ventricular weights, as well as initial genetic markers that indicate early stages of cardiac stress. For high altitude producers in WY and CO, this may have potential impacts on pulmonary arteriole pressure (PAP scores) and the incidence of brisket disease. Additionally, muscle biology work suggests that gestational stress may impact future eating quality of the beef through increased calpastatin (an enzyme involved with muscle break down) as well as muscle fiber development.
Studies at the University of Nebraska have evaluated herd management and supplementation programs during late gestation. Adult cows exposed to slightly more nutritional stress during late gestation (cows that were not supplemented prior to calving) appeared to breed back similarly to their supplemented herd mates, but the heifer calves born to unsupplemented cows reached puberty at a later age and had reduced conception rates.
The importance of this information directly relates to the calving date discussion. While we may be able to reduce costs by shifting our calving dates back to late spring, this potentially may impact the quality and longevity of the calves we produce, as well as the longevity and fertility of the heifers generated from these pregnancies. Working backward, a May 1st calving cow would have had to conceive approximately July 23rd. This means that mid-gestation would occur during early September through early December, a period of time with low, and continually decreasing, forage quality. If those May calving cows also have calves at their side during December and January, we are further stressing that cow during mid gestation. If we continue to rough that cow through the winter months of January and February, assuming that although she is thin, she will regain her weight and rebreed during the summer months, we may be also affecting the quality and fertility of the heifer calves she is carrying at that time.
The main idea is another over-used phrase – “there’s no such thing as a free lunch.” While it may be possible to reduce costs in the short term, the longer term consequence for this decision may be felt through subsequent steer performance via retained ownership programs, or through heifer development and breeding success in the younger cows. However, these gestational effects discussed may be overcome in the long term through herd adaptation and herd selection decisions. In the very least, this new research reinforces the idea that environment can have a large impact on the quality and uniformity of the cattle produced, and that many of the performance and fertility differences that we see on a year to year basis may not only be influenced by current conditions, but also by the previous gestational environment of those animals.
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