By Steve Boyles,
The goal is to have a winter feeding program meets the cow’s requirements and is economical. There is a biological priority for nutrients. The needs for maintenance, growth and milk production must be met before we can optimize reproduction.
The period from approximately 60 to 90 days prior to calving is affects the calf and the subsequent reproductive performance. Fetal growth is at its maximum and fat stores will be used for lactation. Nutrition during this time also affect colostrums quality. Underfeeding during this time period include:
- Lighter calf birth weights (although calving difficulty won’t be reduced).
- Lower calf survival.
- Lower milk production and calf growth.
- A longer period for cattle coming back into heat.
Cold Temperatures: The only adjustment in cow rations necessitated by weather is to increase maintenance energy. Protein, mineral and vitamin requirements are not changed by weather stress. The general rule of thumb is to increase winter ration energy 1 percent for each degree (F) below the lower critical temperature. Here are some examples.
|Effective Temperature||Extra TDN Needed||Extra Hay Needed (lbs./cow/day)||(or) Extra Grain Needed, (lbs/cow/day)|
|10 F||20%||3.5-4 lbs||2-2.5 lbs|
|-10 F||40%||7-8 lbs||4-6 lbs.|
Cold weather can affect cattle. While cold weather generally increases intake, windy or wet weather will reduce grazing time and intake. The cows would rather find shelter out of wind than eat.
Forage Quality and Intake: As forage quality decreases, forage intake also decreases.
Beef cattle selectively graze, eating the better-quality forage first. Providing protein supplementation to lower quality diets can increase the number of ruminal microorganisms to digest forage. Protein supplementation of poor quality forages will increase forage intake. Increased forage intake meets the cow additional energy intake. Thus, to maximize profitability, it is essential to optimize protein.
Protein Requirements in last 1/3 of pregnancy: Gestation has little effect on the cow’s protein requirement until about the seventh month of pregnancy. About two-thirds of the fetal growth occurs during this last one-third of pregnancy, and the protein intake of the cow should be increased during the last one-third of pregnancy to ensure the cow will be in good condition at the time of calving. The cow is programmed to take care of the fetus at the expense of her own body, and losses of body condition can occur in late pregnancy when protein or energy are not increased to match the needs of the pregnant cow. Adequate protein during this period also is essential for the cow to produce abundant, high-quality colostrum. Colostrum quantity and quality influences the newborn’s immune system.
Protein Supplementation & Partitioning Protein: Protein requirements are now including metabolizable protein (MP)so as to take into consideration the differences in rates of digestion and utilization of various protein sources and to account for requirements of rumen bacteria and those of the animal. This is a change over the established system of describing protein requirements as Crude Protein. While energy is the most commonly deficient nutrient in beef-cow diets, protein often represents the largest “out-of-pocket” expense. Protein can be divided into two components, degradable intake protein (DIP) and undegradable intake protein (UIP). The DIP fraction is available to the rumen microflora and can be used for their growth and digestion of dietary fiber. Supplementing low-quality forages with DIP has been shown to increase forage digestion and intake. The UIP is not available to the rumen microflora and has no effect on forage utilization. The UIP fraction can be a direct supply of amino acids to the cow or it can go undigested and be expelled.
Oil seed byproducts (soybean meal, cottonseed meal, sunflower meal) contain a high percentage of DIP while proteins derived from animal sources contain mostly UIP. Forage-based diets should be focused on the inclusion rates of DIP in the diet.
Generally, DIP can supply CP approximately 7% of the diet. If the required CP in the diet exceeds 7% of the DM, all CP above this amount should be UIP. In other words, if the final diet is to contain 13% CP, 7 of the 13 units should be UIP, or 54% of the CP and 6 of the 13 percentage units should be DIP, or 46% of the CP.
Non-Protein Nitrogen (NPN): Cattle can use “natural” protein such as that contained in feedstuffs or other nitrogen sources. Sources other than natural protein are generally referred to as nonprotein nitrogen (NPN) sources. Common NPN sources used include urea, biuret and ammonia hydroxide. Limited amounts of the DIP in supplements can be replaced by NPN. An inclusion level of 15 percent of the total crude protein (or 20 percent of the DIP) as NPN can be used without significantly jeopardizing livestock performance.
Previous research where supplement containing significant amounts of NPN indicates that, at best, 50 percent of the protein coming from NPN can be utilized by cows consuming low- to medium-quality roughages. However frequency of feeding may improve utilization.
Supplements containing high bypass protein sources are better utilized in combination with NPN than are lower bypass sources such as SBM. In general, producers can price high bypass compared to low-bypass protein sources on a pound-for-pound basis for use with beef cows. It should be pointed out, however, that high-bypass sources plus NPN can be used in growing/finishing programs.
Energy Supplementation with Grain: When the protein content of the forage is high (> 10% crude protein), grains or low protein supplements (< 20% CP) can be used. It hase been suggested that an energy supplement level that would minimally affect forage intake would be .7% of animal body weight. However, level of grain supplementation can vary with forage quality.
Digestible Fibers as Energy Sources: Studies with readily degradable fiber sources as energy supplements for grazing and forage-fed ruminants have yielded different responses than research with grains. Soybean hulls result in only a small decrease in forage intake. Other sources of readily degraded fiber such as wheat midds, beet pulp, and corn gluten feed have generally not decreased forage intake as much as grain-based supplements.
High protein supplements that do not contain urea or other nonprotein nitrogen sources do not need to be fed every day. Simply double the amount and feed every other day. Range cake or cubes (20% crude protein) can be utilized with intermediate quality forages. Altering body condition with supplements prior to cold weather may be more effective than waiting until cold weather occurs.
|Level of Protein in Supplement:||Low
|Forage CP Level:||10%||6-10%||6%||6-10%|
|When Feed:||Every Day||Every Day||Alternate Days|