I am going to graze cows on alfalfa pasture for breeding. What problems may I encounter other than bloat?
When grazing alfalfa or other legumes, the first concern is obviously bloat. However, bloat can be limited through grazing management. In New Zealand and Australia where legumes are grazed intensively, the loss of cattle is only 0.3 to 1.2%.
Use of non-bloating legumes such as birdsfoot trefoil, sainfoin and cicer milkvetch can help. In addition, a reduced-bloat variety of alfalfa was recently developed in Canada.
Livestock management is the key to successfully grazing legumes. Feed animals good hay with plenty of water before turning them out on pasture. Gradually acclimate the animals by turning them out for several hours in the afternoon over several days. Observe them and remove chronic bloaters.
Maintaining a high density forces cattle to utilize the whole plant, not just the leaves. Avoid rotating to new pastures on days with heavy dew, rain or after a frost. In addition, provide plenty of water, minerals and utilize a bloat-guard product.
Fetal death loss and reduced conception rates can occur when alfalfa is grazed during breeding season. And, with no outward signs, the problem may not be readily apparent to the manager.
These problems are caused by an excess of highly digestible intake protein (DIP). Lush green alfalfa is high in DIP, but this problem may also be true of feeding any excess protein.
Ruminally degradable intake protein consumed in greater amounts than what rumen bugs can utilize is absorbed through the rumen wall. The excess protein then travels to the liver where it’s converted to urea, which leaves the liver via the bloodstream and concentrates in the kidneys for excretion.
Urea in the bloodstream is where the problem lies. The fetus receives all its nutrients from its dam’s blood via the umbilical cord. The cow, because of her size and her fully developed metabolic system, is better able to handle the excess urea, while the fetal calf is not. The urea is toxic to the calf, and it may die.
Excess protein also can adversely modify the uterus so that the normal processes leading to fertilization, embryo development and fetal implantation may be hampered. Because uterine development influences embryo development, cows on a high protein diet may be conceiving, but the embryos are not surviving.
Producers with cows on a high protein diet should supplement some energy – either carbohydrates or fats – to utilize more of the excess protein. Supplemental fat may also allow the cow to return to estrus earlier after calving. It also may help secrete more progesterone, which is necessary for implantation and nutrition of the newly formed embryo.
In addition, some fats inhibit the production or release of prostaglandin by the uterus. This prevents regression of the corpus luteum on the ovary so the newly formed embryo survives.
What’s your opinion of a.m. vs. p.m. cutting of alfalfa hay?
The main advantages of cutting alfalfa hay in the afternoon are a higher sugar and starch content and less fiber. Studies show dairy cows fed such hay produced 10% more milk. The effects on beef cattle, however, are harder to measure.
These trials were done on dry hay. When hay was harvested as haylage, there were no differences in sugars, neutral detergent fiber or in vitro digestibility.
A major concern for cutting hay in the afternoon is the extended drying time. Because hay won’t dry much overnight, this can delay baling by up to eight hours.
If the choice is between somewhat higher sugars or getting the hay put up as quickly as possible, we should get the hay up. The longer hay sits on the ground, the greater chance of weather damage and nutrient loss.
David Wieland is a nutrition consultant specializing in cow/calf, feedlot and horses. Based in Shepherd, MT, he also publishes a subscription newsletter. Contact him at 406/373-5512 or firstname.lastname@example.org.