Dairy heifers represent a large expense of resources, including feed, buildings and labor, yet they return no money to the farm until they calve. Overall management of dairy heifers must be handled in a manner that yields the best quality heifer, with a high potential to be productive, and at minimal cost to the farm and the environment.
Feed represents the largest cost associated with heifer production; thus, controlling feed cost is a major way to control the total costs of raising the heifer. Feed efficiency (lb. milk/lb. feed) is an important management concept for lactating dairy cows; however, the concept is seldom mentioned for the growing heifer. Feed efficiency for a growing animal is measured as pounds of gain per pound of feed. There are several factors that can greatly impact feed efficiency in the dairy heifer, such as genetics, forage quality (digestibility), growth rate or stage of growth, body condition or gain in body composition, gestation, heat or cold stress (environmental stresses) and exercise level.
Several of the factors affecting feed efficiency are affected by management, such as housing, types of feed and nutritional system used for the heifers. An important nutritional aspect related to feed efficiency that has been researched in growing ruminants for several years is the concept of precision feeding, which promotes greater efficiency of nutrient utilization and allows nutrient requirements to be met more precisely. Feeding high-concentrate, high-energy diets as opposed to traditional high-forage diets has also been an area of recent study. Each of these concepts can improve the heifer’s feed efficiency, and research has shown that they are additive and can be used together in a single heifer feeding scenario without negatively impacting future productivity. The concept of precision-fed, high-concentrate feeding has been the subject of several recent research trials and continues to be studied.
The following is an overview of the important concepts that are part of precision feeding systems for dairy heifers, including example rations. Nutritional and management aspects of implementing precision feeding and precision feeding with high levels of concentrate are discussed. This system uses highly digestible feed sources in a controlled feeding environment with an emphasis on feed efficiency, reducing daily ration costs and minimizing manure output.
Feed a Balanced Diet
Feeding dairy heifers a balanced diet is always important. In the case of precision feeding, no additional free-choice forages are fed, and the balanced diet is likely fed in the form of a TMR or mixture of forage and grain, fed once daily. Based on current published research for precision-fed dairy heifers, nutrient specifications as currently understood are as follows:
Balance primarily for crude and soluble protein.
• 14% to 15% CP for prepubertal heifers based on 2.15% BW DMI/d.
• 13% to 14% CP for postpubertal heifers based on 1.65% BW DMI/d.
• Maintain at least 30% to 35% soluble CP in the rations at all times.
• Rumen undegradable CP levels in excess of 25% to 30% are not required; use only standard feed sources based on price and availability and not feeds specifically designed for high-bypass protein.
Heifers require a specific amount of crude protein daily, and for heifers, total protein has been shown to be equally as important as the various protein fractions. Research has shown that added rumen undegradable protein (RUP) is of limited value to the heifer beyond what is found in common feedstuffs. In situations where high RUP feedstuffs are more economical than lower RUP feeds, they may be used; however, they should not be used for the added RUP. Soluble (SP) and rumen degradable crude protein (RDP) are efficiently utilized by dairy heifers. In studies with SP added as urea, improved nitrogen retention in rations with SP approaching 40% has been observed. It appears that nitrogen utilization in the precision-fed dairy heifer is efficient, allowing for efficient rumen microbial protein production throughout the day despite feed access being limited to a few hours. In various published research trials, maximum protein efficiency has been demonstrated when heifers are fed diets containing 14% to 14.5% CP.
The energy requirement of the heifer will be influenced by the size, growth rate and environment of the heifer. There are two feeding strategies to meet the energy requirements of growing dairy heifers. First, diets can be formulated at variable energy densities and fed ad libitum to allow the heifer to select her energy consumption. In the second strategy, heifers’ diets can be formulated at a fixed (generally higher) energy content and precision fed to specifically meet the heifers’ energy requirement. Regardless of feeding strategy, heifers should be fed energy to allow 1.75 to 2.00 lb. of average daily gain or approximately 130 kcal of metabolizable energy per pound of metabolic body weight (BW0.75).
FIBER (NDF OR ADF):
The current NRC levels for fiber for dairy heifers may not be warranted based on recent precision feeding experiments. Traditionally, high levels of fiber or low-quality forage were fed to dairy heifers to control dietary energy; however, precision feeding high-concentrate, low-fiber diets effectively accomplishes the same goal. The NDF requirements for growing heifers are not well established and research has yet to find a detrimental lower limit, but some prudence is required. Heifers fed diets as low as 19% NDF have done very well and have not acquired metabolic or lameness problems under routine management, undoubtedly due to the limitations placed on DMI. Diets lower than 19% NDF have not been studied. The NDF values presented below are generally lower than recommended by NRC. These levels are expected to provide an amount in excess of requirements for adequate rumen function but at a level expected to be approximately 60% to 70% of voluntary DMI due to limitations of gut fill. It is important to note that in all experiments with dairy heifers where low NDF concentrations have been fed, the heifers have been precision fed. Thus, if low NDF concentrations are fed, the heifers must be fed with controlled intakes.
VITAMINS AND MINERALS:
In precision feeding systems, balance for current NRC specifications. At present there are no data to suggest vitamin and mineral requirements are altered when heifers are precision fed higher-concentrate diets.
Feed Ingredient Selections
Given the diversity of feed ingredients available for ration formulation, a comprehensive set of recommendations is not available at this time. Feed ingredients for dairy heifers should be selected on cost, availability and nutrient composition. There are, however, a few observations in regard to feed ingredients for precision feeding that are pertinent.
Much of the dairy heifer precision feeding research conducted to this point has utilized corn and soybean meal as standard concentrate sources to provide energy and protein. These and other ingredients can vary substantially in price, however. There is opportunity to incorporate numerous byproduct ingredients into precision feeding systems. As the concentrate proportion of the ration increases, there is greater opportunity and flexibility for including these cost-effective ingredients.
The forage component of the ration is an important consideration for precision-fed heifers. Using high levels of corn silage in precision-fed heifer rations is possible; however, it requires careful monitoring of the heifers because a considerable proportion of the corn silage is corn grain. Many of the rations used in precision feeding research have used corn silage as the principal forage, and no detrimental effects have been observed – even when corn silage was used as the only source of forage. As another alternative, a precision-fed, high-forage diet that is high in corn silage may be used to replace a more traditional diet based on lower-quality hay and fed for ad libitum intake.
When feeding high levels of grain to heifers, limiting the amount of alfalfa hay may be required because this combination of feeds may promote the development of chronic, frothy bloat in heifers that are predisposed to this condition. Frothy bloat is the only metabolic or ruminal abnormality that has been observed when heifers have been precision fed high-concentrate diets. Frothy bloat appears to occur in about 10% to 15% of Holstein heifers when the concentrate level is very high (about 75% of DM).
Straw or other extremely high-fiber forages can be incorporated into precision-fed heifer diets, but it is not recommended as greater excretion of fecal matter will result with little additional benefit associated with this forage source to the exclusion of others. With the exception of limiting the inclusion of alfalfa hay, we are not aware of any forage source that should be specifically avoided or included in a precision feeding system.
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Originally published in May 2016 by Jud Heinrichs with Penn State and Geoff Zanton with U.S. Dairy Forage Research Center
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