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).