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The Winter Of Mud: Consequences Of The Wettest Year On Record
DR. MICHELLE ARNOLD
LEXINGTON, KY.
Record rainfall in 2018 has had major impacts on cattle health in KY. Despite relatively mild temperatures this winter, submissions at the UKVDL and telephone conversations with veterinarians and producers confirm cattle are losing body condition and some are dying of malnutrition. The very prolonged cloudy, wet weather with regular bouts of rain has resulted in muddy conditions that require substantially more energy in feeds just to maintain body heat. In addition, the hay quality is exceptionally poor this year as much of it was cut very ripe (late stage of maturity), rained on while curing, and baled with enough moisture to support mold growth. Many cows presented to the laboratory for necropsy (an animal “autopsy”) revealed a total absence of fat and few, if any, other problems. This indicates winter feeding programs on many farms this year are not adequate to support cattle, especially cows in late pregnancy or early lactation, or their newborn calves, even though bitter cold has not been a factor.
The body of the animal has several defenses against cold. The first is the hair coat which grows longer in winter and offers considerable help in conserving heat and repelling cold. Under winter conditions, if an animal’s coat cover is wet and muddy, then energy requirements for maintenance can easily double, particularly if the animal is not protected from the wind. Energy from intake of hay that is adequate for maintenance in normal years is falling far short of the requirement this year. Cold conditions are not too difficult for cattle but when rain and wind are added, heat loss is multiplied several times by the effects of conduction and evaporation. Under these circumstances the “wind chill factor” referred to by the weatherman has real meaning to a cow. If producers are not supplementing cattle with adequate energy AND protein sources, hay of unknown nutritional quality often does not provide sufficient nutrition to meet the animal’s basic requirements. This will result in depletion of body fat stores, followed by breakdown of muscle protein, and finally death due to insufficient nutrition.
Typically, near the end of most winters, both veterinary diagnostic laboratories in KY receive older beef cows for necropsy. These cows often are broken-mouthed or toothless due to their advanced age, are heavily pregnant or in peak milk production and in poor body condition (BCS 2-3). However, this winter, ‘malnutrition’ cases include young cows and pre-weaning/weaning age calves, indicating serious nutritional deficiencies in the feedstuffs, especially the hay produced last summer. The producer may first notice a cow getting weak in the rear end. Later she is found down and is unable to stand. Death follows within a day or two after going down. Multiple animals may die within a short period of time.
At necropsy, the pathologist finds a thin animal with no body fat stores but the rumen is full of bulky, dry forage material (poor quality hay). Even the small seam of fat normally found on the surface of the heart is gone, indicating the last storage area in the body for fat has been used up. Despite having had access to free choice hay, these cattle have died from starvation. Although hay may look and smell good, unless a producer has had the hay tested for nutritional content, he or she does not know the true feed value of that harvested forage. It is often difficult for producers to bring themselves to the realization that cattle can actually starve to death while consuming all the hay they can eat – especially if crude protein levels are in the 3-4 percent range, and TDN is <40 percent – as is not uncommon in some late-cut, overmature, rained-on hay.
Inadequate crude protein in the hay (below 7-8 percent) means there is not enough nitrogen for the rumen microflora (“bugs”) to do their job of breaking down fiber and starch for energy. Digestion slows down and cattle eat less hay because there is no room for more in the rumen. Cattle are expected to eat roughly 2.5 percent of their body weight in dry matter but this may fall to 1.5 percent on poor quality hay. Many producers purchase “protein tubs” varying from 16-30 percent protein to make up for any potential protein deficiencies but fail to address the severe lack of energy in the diet. In the last 60 days of gestation, an adult cow (1200 pound seating 2 percent of her body weight) requires feedstuffs testing at least 54-56 percent TDN (energy) and 8-9 percent available crude protein while an adult beef cow in the first 60 days of lactation requires 59-60 percent TDN and 9-10.5 percent available crude protein.
In addition to malnutrition in adult cattle, inadequate nutrition and weight loss severely affect the developing fetus in a pregnant cow. Maternal nutrition during the last trimester of pregnancy – particularly dietary protein level – has been well-documented to play an important role in calf survivability. A weak cow may experience dystocia (a slow, difficult birth) resulting in lack of oxygen to the calf during delivery, leading to dead or weak (“dummy”) calves. 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 received adequate dietary protein during the last 100 days of pregnancy. Colostrum quality and quantity from protein and energy deficient dams is frequently not adequate for calf survival and performance. One study looking at diets during pregnancy found at weaning, 100 percent of the calves from the adequate energy dams were alive compared to 71 percent from the energy deficient dams. The major cause of death loss from birth to weaning was scours, with a death loss of 19 percent due to this factor.
Mineral supplementation this winter is another area of concern, as copper and selenium levels in liver samples analyzed from a large number of cases have been far below acceptable levels. Copper and selenium are vital nutrients for immune system function and the absence of these nutrients is a major factor in development of disease. Selenium deficiencies in adult cows will lead to later reproductive problems of delayed conception, cystic ovaries and retained placentas. Additionally, grass tetany/hypomagnesemia will occur in late February and March in lactating beef cattle consuming only poor quality hay if high magnesium mineral is not made available now.
The best advice for producers is to become expert judges of forage quality by testing hay. Testing is simple, inexpensive and results are easy to interpret. Contact your local cooperative extension service if you need assistance to get this accomplished. If cows are losing weight, consider supplemental feed to help them through the rest of winter until grass is growing and is past the “watery” stage. Contact your nutritionist to review your feeding program. Energy AND protein are both crucial; protein tubs will not be sufficient in most cases to fulfill energy requirements. Adequate nutrition is not just important today but also down the road. 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.
It is important to understand that the winter of 2018-2019 has been exceptionally easy temperature-wise but for cattle in Kentucky. Cows of all ages are losing weight now at levels typically seen in late winter. If this problem is not addressed, the expectation is for many stillborn and weak calves that do not survive to be born this spring. Feeding hay exclusively throughout the winter will not necessarily work this year but supplemental feed can fill the nutritional gap. Check out the UK Beef Cow Forage Supplement Tool at
http://forage-supplement-tool.ca.uky.edu/. Enter the values from your hay test and stage of production of your cows (gestation or lactation) to find a supplement that will work for you. The UK Beef Cow Forage Supplement Tool was produced by Kevin Laurent, Jeff Lehmkuhler and Roy Burris in the University of Kentucky Department of Animal and Food Sciences and serves only as a tool to estimate forage intake and supplementation rates. Remember actual feed/forage intake and body condition should be monitored throughout the winter and cattle should also have access to a complete mineral supplement and clean drinking water at all times. ∆
DR. MICHELLE ARNOLD: DVM (Ruminant Extension Veterinarian, UKVDL)
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