As we move into spring and early summer with green pastures ahead, cattle will begin to get a fair amount of their nutrients from these forage diets. Depending on the pasture makeup and maturity, there is potential that the diet provided is not balanced in a manner to allow efficient production of milk or meat. Commonly, pastures go through 3 main phases of quality – early spring growth, maturity, and then regrowth. While early growth and regrowth have adequate protein and energy concentrations, regrowth can lack total tonnage to meet animal needs. On the other hand the middle phase tends to have adequate yield, yet it can lack essential nutrients as fiber content increases with maturity. Due to this growth pattern, commonly it is energy and protein that can become limited in cattle diets when on pasture. It is important to understand the stage of growth and the grass / legume component of pastures and the energy requirement of the livestock before implementing a supplementation program.
Traditionally, cattle are grazing pasture during the hotter months (late spring, summer, and fall) and this is typically when cattle are lactating and gestating or being backgrounded for feedlots. These three stages (lactation, reproduction, and growth) have overall greater energy requirements additionally, cattle on pasture can require higher amounts of energy for maintenance. Maintenance requirement on pasture is greater since cattle are eating greater amounts of fiber (a more energy intense digestion process), walking further for food and water, and utilizing energy to maintain lower body heat.
In many cattle diets, non-fiber carbohydrates (NFC) are the major source of energy and are most commonly found in concentrates and grains. Typically NFCs can be in short supply in strictly pasture systems and supplementation through energy dense concentrates can help increase animal productivity. Additionally, plant protein that is available to the microbes (Rumen Degradable Protein -RDP) is degraded to nitrogen and utilized to support microbial protein synthesis. Rumen microbes are composed of upwards of 85% protein; therefore RDP is directly correlated to microbe growth, which influences overall ruminal fermentation and digestion of all nutrients. Rumen Undegradable Protein (RUP) and the microbial protein (produced by rumen microbes) are metabolized and used by the ruminant as a source of amino acids. Supplementation of RDP or non-nitrogen sources can give rumen microbes the nitrogen necessary for adequate growth and increase feed utilization on lower quality forage diets.
Whether you plan on cattle utilizing pastures as the main diet or strictly for roughage portions, it is important to know the nutrient makeup of the forages and supplement as required.
Written by: Kara Riccioni, MBA, MS, PAS, SEEDWAY Forage & Grain Nutrition Specialist
Reference Articles:
https://beef.unl.edu/documents/2016-RBCSymposium/RBCS-2015-Cow-Supplementation.pdf
https://fyi.extension.wisc.edu/forages/supplementing-stockers-on-pasture/