By Michelle Arnold, Louis L. 'Lucky' Pittman
Near the end of most winters, diagnosticians at both the Murray State University - Breathitt Veterinary Center and the UK Veterinary Diagnostic Laboratory frequently receive diagnostic submissions for necropsy of aged beef cows - often broken-mouthed or toothless - that are heavily pregnant or are in peak milk production, 1-3 months after calving. These older cows are frequently in poor body condition (BCS 2-3) with no body fat stores and frequently have a rumen full of forage material (hay). These cows may be described as "bloated" by the producer. Despite having had access to free choice hay, these old girls have just 'run out of gas' with a belly full of hay and green grass just around the corner.
However, this winter, we have been encountering these 'malnutrition' cases on a much more frequent basis, at a much earlier date, and are seeing young cows and pre-weaning/weaning age calves also affected, with some of the first cases fitting this description arriving at MSU-BVC in late December, and the UKVDL in February and continuing through the present time.
The winter of 2013-14 has presented long periods of colder temperatures and greater snow/ice cover than most Kentucky beef producers have encountered in the past 15-20 years. It is likely that winter feeding programs on many farms have been inadequate for pregnant/lactating cows and growing calves. We have observed increased submissions and telephone consultations with veterinarians and producers who are experiencing animals losing excessive body condition and/or dying of apparent malnutrition.
Numerous university studies have demonstrated that the lower critical temperature for cows with dry, heavy winter coat is 18F. If cows are wet, the lower critical temperature is surprisingly high, at 59F. For every degree that the environmental temperature drops below the low critical temperature, a cow must expend 2% more calories in order to maintain body heat and condition. Wind-chill effects due to wind speeds will further increase energy expenditure.
During extended periods of low ambient temperature (as we have experienced this winter), if producers are not supplementing cattle with adequate energy and protein sources, hay alone may not provide sufficient nutrition to meet the animals' needs. This will result in depletion of body fat stores, breakdown of muscle protein, and death due to insufficient nutrition.
The Spring/Summer of 2013 presented good growing conditions with greater hay production than in recent years. However, poor cow performance in herds where winter feeding consists of hay only suggests that the hay produced was of poor nutritional content. Although hay may look good, unless a producer has had their hay tested for nutritional content, they do not know what the true feed value is.
Producers need to realize that cattle can actually 'starve to death' while consuming all the hay they can eat, especially if crude protein levels are 3-4% and TDN is <30%. Remember, in the last 60 days of gestation, an adult cow (1200 pounds eating 2% of her body weight) requires at least 54-56% TDN and 8-9% available crude protein while an adult beef cow in the first 60 days of gestation requires 59-60% TDN and 9-10.5% available crude protein.
We have also received numerous calls and diagnostic submissions associated with 'weak calf syndrome' or full-term calves which were presumed to have been born dead. Almost without exception, these calves have been born alive, but never stood or nursed, and there have been no gross or microscopic lesions or pathogens identified in fetal tissues or placenta, which would indicate an infectious cause of mortality.
Dietary protein levels during the last trimester of pregnancy have been well-documented to play an important role in calf survivability. Calves born to protein-deficient dams are less able to generate body heat and are slower to stand and nurse compared to calves whose dams had received adequate dietary protein during the last 100 days of pregnancy (for more detailed information: http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1151&context=rangebeefcowsymp).
Calves born during unseasonably cold weather, with ice or snow on the ground, are at risk of chilling and death if they do not gain their feet and nurse soon after birth; inadequate energy and protein nutrition in the dam often leads to higher calf mortality in these conditions. Additionally, colostrum quality and quantity from protein- and energy-deficient dams may be less than optimal for best calf survival and performance.
It is evident that some producers in Kentucky have not provided adequate mineral supplementation to their cattle this winter, as copper and selenium levels in liver samples analyzed from a number of animals have been far below acceptable levels. Many of these cases have died of malnutrition and/or herd-wide outbreaks of respiratory disease (including pneumonia in pre-weaned calves). Additionally, we have seen a number of grass tetany/hypomagnesemia cases in early-lactation beef cattle consuming only hay suggesting that 2013 hay supplies may also be low in magnesium content.
It is important to understand that the winter of 2013-2014 has been exceptionally difficult for cattle in Kentucky and cows are "pulled down" much more than we typically see in late winter. This fact is why we are seeing an increase in death loss across Kentucky due to malnutrition in all ages of cattle and many stillborn and weak calves that do not survive. What has normally worked in years past (feeding cattle hay exclusively throughout the winter) will not necessarily work this year. Consider supplemental feed to help your cattle through the next month to 6 weeks until grass is growing and is past the "watery" stage.
Energy AND protein are both crucial; protein tubs will not be sufficient in most cases to fulfill energy requirements. Contact a nutritionist or your herd veterinarian to review your feeding program. Adequate nutrition is not just important today but also down the road. Continued milk production, the return to estrus and rebreeding, and overall herd immunity are also impacted over the long term. Continue to offer a trace mineral mix high in magnesium in order to prevent hypomagnesemia or "grass tetany" at least through the first of May. Remember the old adage regarding the effect of winter on cattle, "February breaks them, March takes them." Unfortunately, that could not be truer in the aftermath of the severe winter of 2013-2014.
Source:osu.edu