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Replacement Management in Cattle | Growth Diets
Growth Diets R E James, Virginia Tech, Blacksburg, VA, USA ª 2011 Elsevier Ltd. All rights reserved.
Introduction Dairy heifers should be fed and managed to achieve 55% of their mature weight at first breeding and 82–85% of their mature weight at first calving. These principles enable the establishment of growth goals regardless of breed. In addition, heifers should have a body condition score after calving of 3.5 and be free of disease. Probably, no factor other than the feeding program influences achievement of these goals. The feeding program also comprises 50–70% of the cost of rearing heifers to first calving. Therefore, profitable heifer-rearing enterprises must concentrate on economical feeding programs. The purpose of this article is not to provide a ‘how to’ description of heifer-feeding programs because available feed resources and facilities vary to a great extent. This article will focus on a discussion of decision-making areas with considerable importance to the financial success of the heifer-feeding programs. Managing the feeding program of the heifer enterprise is not unlike that of any other decision made on the farm. Good heifer managers maximize benefits, control expenses, and manage risk well. This article will concentrate on the major goals the heifer grower needs to achieve during the rearing period: 1. successful weaning from liquid diets to forage- and concentrate-based feeding programs with minimal stress and loss of weight, and transition to group housing management systems; 2. controlling the rate of gain during the prepubertal period to enable early breeding (12–13 months) while assuring desired mammary development; 3. sustained growth after breeding and optimization of economy of feeding; and 4. preparing the heifer for eventual calving. The development of the feeding program should consider that approximately 50% of the total gain in height occurs during the first 6 months of life with 25% occurring from 7 to 12 months and the remaining 25% during the 12 months before calving. Feed cost is generally lowest per unit of gain during the first 6 months of life and then increases at a decreasing rate during the remaining 18 months. The proportion of body weight to wither height increases linearly and the increase in wither height as a proportion of total height is greatest during the first 6 months. This demonstrates that assuring adequate growth during the first 6 months is critical to success in growing
the dairy heifer and is where nutrition and management must be optimal. Poor growth prior to puberty cannot be compensated for later in the rearing period. After puberty and when the heifer has attained early growth goals, opportunities for considerable economy of feeding exist. Profitable heifer management requires labor-efficient systems and the ability to evaluate ration dry matter intake (DMI) and animal performance. Periodic weighing of heifers with comparison to established growth goals is critical to achieving desired performance. Heifer-feeding programs vary widely depending on the environment and available forage resources. In tropical and more temperate areas of the world, pasture-based systems are more popular because they provide nutrients at the lowest cost and promote excellent animal health. In other areas where land resources are more valuable, or the length of the grazing season is limited, confinement systems may be more conducive to economical heifer growth. In many areas of the world, a combination of systems where heifers are raised on pasture during the warmer months and moved to confinement during the winter is commonly practiced. Basic principles of nutritional management using pasture-based and confinement systems will be discussed.
Managing the Transition Calf This stage refers to the time between 2 weeks prior to and 2 weeks after weaning. Success during this phase is dependent upon excellent housing and health programs. Regardless of the rearing system, it is assumed that the calf is consuming adequate amounts of a high-energy calf starter grain prior to weaning. When preweaned calves have been housed individually, it is recommended that calves be placed into small groups of 4–6 calves several weeks after weaning to allow them to adjust to competition for feed. However, when the environment is optimal, the author has observed newly weaned calves reared in groups of 20–30 with great success. Under this scenario, ventilation is outstanding, bedded pens are cleaned frequently, and calf starter grain is fed often to keep the feed fresh. Calves that have been fed their liquid diet in groups from mob or robotic feeders adapt to weaning quite well as there is no social stress associated with adapting to the group housing and feeding environment. Calf starter grains can vary widely, but should be highly palatable and digestible,
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404 Replacement Management in Cattle | Growth Diets Table 1 Desired nutrient levels in a calf starter grain
Nutrient
Amount recommended
Crude protein (% of DM) Fat (% of DM) TDNs (% of DM) Metabolizable energy (Mcal kg Calcium (% of DM) Phosphorus (% of DM) Vitamin A (IU kg 1) Vitamin D (IU kg 1) Vitamin E (IU kg 1)
18.0–22.0 3.0 80 3.1 0.60 0.40 2200 300 24
1
DM)
DM, dry matter; TDNs, total digestible nutrients.
with nutrient concentrations as shown Table 1. Under more intensive liquid-feeding programs for calves, protein levels may be increased to 22% of dry matter (DM). For calves that have been housed individually prior to weaning, Morrill suggests three transition pens after weaning. The first pen has 4–8 calves with 2.8 m2 per calf and a starter the same as they had been receiving prior to weaning. Two weeks later, the calves are moved to a larger pen with more calves and with the same starter and about 15% chopped alfalfa hay added to the ration. In the next transition pen, the amount of chopped alfalfa is increased to 20% of the mixture. By the time the calves are moved to the last transition pen, they can be switched to a more economical grower concentrate mixture, with examples shown in Table 2.
Table 2 Examples of calf starter grain mixtures Feed
Grower 1
Grower 2
Cracked corn Rolled oats Rolled barley Molasses Soybean meal Canola meal Limestone Dicalcium phosphate Salt Trace mineral mix Vitamin E mix Vitamin ADE mix Additives
63.8 9.9
53.23
3.5 20.4 1.2 0.27 0.18 0.09 0.09 0.07 0.50
20.48 2.97 21.33 1.08 0.18 0.09 0.09 0.07 0.46
Values are percentage of total mixture on an as-fed basis. Composition of trace mineral mixture (%): Co, 0.01; Cu, 1; Fe, 5; I, 0.06; Mn, 4; Se, 0.03; Zn, 4. Composition of vitamin ADE mixture, per kg: A, 44 000 KIU; D, 990 KIU; E, 17 600 IU. Vitamin E supplement contains 44 000 IU kg 1. Grower grain mixture should contain coccidiostat or other additive as desired. Reproduced from Morrill J (1999) Proceedings of the Third Conference of the Professional Dairy Heifer Growers Association, p. 26. Minneapolis, MN. Savoy, IL: Professional Dairy Heifer Growers Association.
Workers at North Carolina State University have successfully developed a self-fed calf starter grain utilizing cottonseed hulls to limit intake. Calves are offered the starter from birth through 4–6 months of age. Cottonseed hulls represent a uniform, consistent source of more slowly digested fiber that helps limit intake in the older heifers. Critical to success of the system is maintaining a reliable source of clean cottonseed hulls, keeping the selffeeders clean, and providing plenty of water. Nutrient content of these starter mixtures on a DM basis is 16–18% crude protein (CP), 76% total digestible nutrients (TDNs), 0.66% calcium, and 0.42% phosphorus. The ingredient composition is 493 kg ground corn, 300 kg cottonseed hulls, 184 kg soybean meal, 9 kg calcitic limestone, 5 kg tricalcium phosphate, and 5 kg white salt, ionophore, and a vitamin–trace mineral mixture. Although apparently successful, these starters are lower in energy and require higher intakes to meet the energy requirements for acceptable growth.
Managing Growth of the Heifer from Weaning to Breeding Once the heifer has been successfully weaned and has transitioned to group housing, control of rearing rate is of primary concern. If one assumes that a goal of age at first calving of 22–24 months is desirable, breeding should be initiated at 12–13 months. Animals must be of adequate weight and body condition to accomplish this objective. Table 3 demonstrates the challenges faced in feeding the large-breed heifer prior to breeding. It also demonstrates the difficulty in attaining ages at first calving below 20 months. Based upon these assumptions, it is assumed that rations for the large-breed heifers should foster a gain of 750–900 g day 1. Smaller breed heifers require gains of 500–650 g day 1. Excessive gains may increase the risk for problems with mammary development, particularly if protein is limiting in the ration. Pasture-based systems
In many areas of the world, the greatest forage asset is the availability of abundant, low-cost land suitable for pastures. The best example for pasture systems exists in Table 3 ADG necessary to achieve suggested 360 kg weight at breeding and postcalving body weight of 570 kg at varying ages Age at calving goal (months) Age at breeding goal (months) ADG birth–breeding (g) ADG breeding–calving (g)
20 11 953 884
22 13 800 884
24 15 680 884
Assumes 39 kg birth weight, 45.4 kg loss of weight at calving, and 280 days of gestation. ADG, average daily gain.
Replacement Management in Cattle | Growth Diets
Ireland, New Zealand, southern Chile, and Argentina, and similar climes that have cool temperatures with frequent, moderate rainfall during a large portion of the year. Less desirable examples of grazing systems are range management systems in arid areas, which require extensive land bases exceeding 20 hectares per animal and they support little more than maintenance nutrient requirements. In many areas of the world, the role of pasture in heifer-feeding systems is probably in between these extremes. It is important to evaluate realistically the advantages and liabilities of pasture systems and determine how best to optimize their benefits and minimize the risk of their shortcomings. The biggest challenge faced in the pasture system is reliably estimating the carrying capacity of the land. If land is to be utilized for pasture, its use during the year must be maximized to provide the best compromise of yield of animal growth and forage nutrient yield. Figure 1 shows the effect of grazing pressure on production per animal and per acre. Note that optimal growth per head is not the same as optimal growth per acre. Optimum growth per animal occurs at a point less than optimum for land utilization. When grazing pressure is low to medium, heifers graze on only the best quality forage. When pasture output is optimized at higher stocking rates, heifers are forced to consume some of the less nutritious forage and animal performance declines. This represents a challenge for the heifer grower or dairy producer. Extremes in stocking rate are undesirable. Long periods of low grazing pressure lead to a loss of legumes in a stand and increased growth of weeds and less desirable species. Long periods of high grazing pressure result in temporary or long-term decreases in forage production as nutrient reserves of desirable forage species are depleted and plants become less dominant in the sward. For optimum grazing, one should maintain available forage at
Production
High
Output per head
Output per acre
Medium
Available pasture
Low
Neg
High
Medium
Low
Very low
Low
Medium
High
Very high
Stocking rate
Figure 1 Effect of grazing pressure on production per animal and per acre. Reproduced from Hall MH (2009–2010) The Agronomy Guide. University Park, PA: Department of Crop and Soil Sciences, The Pennsylvania State University.
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approximately 1122–1685 kg DM per hectare. This is the equivalent of a 7–10 cm high stand of bluegrass/ white clover or 15–20 cm of tall grasses and legumes. Continuous or rotational grazing?
Historically, continuous grazing has been the most popular grazing system since it is simple and requires little labor. Grazing pressure is adjusted by adding or subtracting animals or temporarily fencing off areas for hay harvest. However, continuous grazing is a land extensive system, and low production of gain per hectare makes it inefficient. In contrast, rotational grazing can dramatically increase animal performance and forage DM yield per hectare. In heifer feeding systems, intensive rotational grazing systems are probably not as important. Improvements in nutrient quality of forage accrued from more daily movement of fences or shifting heifers to new paddocks daily do not offset the labor and fencing expense and convenient provision of water. Many heifer growing systems include some combination of both continuous and rotational systems. A continuously grazed paddock may be used to house animals during the winter or during periods of drought to enable other areas to recover forage growth. Other paddocks are designed to enable movement of fences on less frequent interval of 3–14 days. Supplemental nutrition of pasture systems
For many areas of the world, dairy heifers cannot be reared without significant nutrient supplementation during some portion of the year. The nutrient variation of grazed forage species represents one of the greatest challenges of grazing, particularly for animals less than 1 year of age. In the more temperate areas of the world, protein concentrations of pasture can vary from 6% to levels exceeding 20%, while the growing dairy heifer may require levels ranging from 12 to 18%. Similarly, energy values will range from those similar to corn silage to levels that more nearly resemble straw. Although heifer rearing regimes might tolerate some variation in growth, in today’s economic climate it is important that heifers calve at an early age and with desired body size and condition. When forage availability is adequate, but quality is lacking, provision of supplemental energy and protein through concentrate feeding is advised. At other times such as winter months or during severe drought, heifers require supplementation with both forages and concentrates. It is beyond the scope of this article to address adequately the supplemental nutrient needs of pasturereared heifers. Pasture-reared heifers require more energy than those in confinement due to their increased activity and exposure to environmental conditions, particularly during the winter. Research at Virginia Tech has shown that
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confinement-reared heifers require 12–25% less energy than indicated by National Research Council (NRC). They are also less influenced by severe cold and wet weather. Therefore, managers of pasture-reared heifers must make adjustments in nutritional strategies when environmental conditions are less than perfect. Factors such as cold weather, nonthermal resting areas, wind, rain, and snow increase demand for energy for maintenance thereby reducing that available for growth. Environmental conditions for heifers raised without housing may become so severe that it is not possible to maintain sufficient growth, even with substantial energy and protein supplementation. Supplementation of rations with energy must be based upon observed growth of heifers during inclement weather. Similarly, supplementation can often be reduced at considerable savings when pasture growth and environment are optimal. The greatest challenge of pasture systems lies in the establishment of pastures that enable maximal grazing throughout the season and provisions for supplementation when pasture nutrients are insufficient to promote desired growth. Depending upon the climate and resources, successful growers utilize a mixture of swards containing cool and warm season perennial grasses and legumes. Young calves readily adapt to pasture systems as they provide ample opportunity for exercise, excellent air quality, and when pasture growth is young and rapid, a plentiful supply of energy, protein, mineral, and vitamins. However, it is important to note that calves weighing less than 150 kg require nutrients at least as high as that for the lactating cow (>16% CP and >2 Mcal of metabolizable energy (ME) per kg of DMI). An additional consideration for younger calves is their susceptibility to parasitism. Aggressive parasite control programs are recommended because the young animals have not developed sufficient immunity more common in animals in their second grazing season. By 300 kg body weight, concentration of nutrients is less important as adequate intake (7 kg DM per day) of forage providing 12% protein and 2 Mcal ME per kg DMI is adequate for 700 g of gain per day. It is uncommon to formulate rations for grazing dairy heifers. Rather the manager assesses pasture quality and availability, and heifer growth to determine if supplemental nutrition is needed. Confinement rearing systems
Young heifers, less than 150 kg body weight, require diets of high forage quality to enhance rumen function and promote economical growth. Forages must be free of mold and spoilage to ensure adequate ration intake. Fermented feeds and a wide variety of by-product feeds are readily accepted by heifers more than 150 kg body weight. Forage quality, as defined by nutrient content, becomes less important for the heifer over 150 kg body
weight as intake is usually not the limiting factor in nutrition. Professional heifer growers have been especially aggressive in seeking ways to provide nutrients at the lowest possible costs. This strategy requires the grower to ‘think outside the box’ when it comes to selecting ration components. Rations are presented to demonstrate the possibilities for utilization of by-product feeds. They are based upon those used by several large heifer growers in Colorado and Texas as well as conventional rations used in heifer feeding trials at Virginia Tech. Each ration was evaluated using the Cornell Penn Minor (CPM) program to determine expected gains based on ME and metabolizable protein (MP). Ration I relied heavily on by-products from vegetable processing, wet brewer grains, and low-cost alfalfa silage, which were of insufficient quality for lactating dairy cattle or export. Frequent weighing of heifers revealed growth of 800 g day 1, while the CPM model indicated that ME supplied by the ration should provide for only 690 g of gain per day and sufficient MP for 1.17 kg of gain per day. Ration II used an exceptional array of by-product feeds. Alfalfa was of lower quality, as was the whole cottonseed. Outdated dairy products (ice cream, cottage cheese, yogurt, and other products) were also used as available in this ration. In comparison to ration I, this ration contained an abundance of protein of a very degradable nature. Sufficient ME and MP were present to support gains in excess of 1 kg day 1, which supported observations on the feedlot of rapid gains, and heavy body condition. Ration III represents the traditional ration fed to dairy heifers in Virginia. MP and ME were present in sufficient amounts to support daily gains in excess of 900 g. These rations demonstrate the ability of heifers to grow at rates that support early calving at recommended body sizes at very low ration costs. The greatest limitation involved in the successful use of by-product feeds is personal prejudices and preconceived ideas of what will be successful. Once it has been determined that by-products contain no harmful substances and that product quality is predictable, many by-products serve as economical ingredients for heifer rations (Table 4). Feeding the Breeding Age Heifer and Bred Heifer Growers should not need to increase nutrient levels for the breeding age heifer, since she should already be on a high plane of nutrition promoting 750–900 g of average daily gain (ADG) for large-breed heifers or 500–650 g of ADG for small-breed heifers. Once the heifer is bred, it is important to maintain these growth rates, although it is possible to tolerate some variation as long as goals for growth are attained at calving. As shown earlier, attaining a breeding weight of 363 kg at 13 months of age requires an ADG exceeding 800 g. However, attaining
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Table 4 Example rations for growing a 225 kg heifer at an average daily gain of 815 g
Ration I
kg DM
CP (%)
RUP (% of CP)
TDNs (%)
ME (Mcal lb 1)
NDF (%)
Cost ($ day 1)
6.0
11.2
45.4
66
2.2
46
0.72
Ground wheat straw, 1.45 kg; wet brewers’ grain, 2.9 kg; carrots, 1.8 kg; wet beet pulp, 1.8 kg; corn screenings, 1.1 kg; alfalfa silage, 3.6 kg; Rumensin was included in the mix. Ration II
5.85
17.2
29.4
68
2.6
35.91
74
Cotton gin trash, 730 g; rolled corn, 1.27 kg; distillers’ grains, 454 g; whole cottonseed, 363 g; alfalfa hay, 1 kg; wheat midds, 1.63 kg; cottonseed meal, 363 g; sorghum silage, 1.27 kg; waste dairy products, 1.82 kg. Ration III
13.6
12.0
33.9
67
2.44
41.3
90
Corn silage, 6.82 kg; soybean meal, 454 g; ground shelled corn, 1.6 kg; orchard grass hay, 2.27 kg. All rations were fed as total mixed rations for ad libitum intake, with prevailing feed prices as of August 2009. DM, dry matter; CP, crude protein; RUP, rumen-undegradable protein; TDNs, total digestible nutrients; ME, metabolizable energy; NDF, neutral detergent fiber.
the postcalving weight of 570 kg requires heifers to continue to gain 750–900 g day 1. Opportunities to utilize by-product feeds in total mixed rations continue. These heifers can tolerate variations in gain, and rapid compensatory growth prior to calving is well tolerated provided that heifers do not become overconditioned.
Feeding Management Considerations Grouping heifers is a challenging issue to resolve, as it is a compromise between facilities, labor, and nutrient efficiency. Heifers should be placed in as many groups as is efficient from a labor standpoint. Suggested grouping are transition heifers, 4–8 months, 9–12 months, breeding-age heifers, and pregnant heifers. If possible, place heifers in groups within a range of 50 kg. Group heifers by size and body condition, paying close attention to note heifers significantly older within a group that may need to be culled. When multiple breeds are present in a herd, it is important to remember that smaller breeds mature more rapidly than larger breeds. If heifers are grouped by size, smaller breed heifers such as Jerseys will frequently become overconditioned. It is recommended that Jerseys and other earlier-maturing breeds are housed with slightly larger and older large-breed heifers. Provision of sufficient feed bunk space is an important consideration in such situations. Factors influencing growth and feed efficiency of dairy heifers
A common misconception regarding dairy heifer nutrition is that published nutrient requirements provide sufficient nutrients to assure the stated rate of gain under a wide variety of environments. One must
remember that these recommendations are based on the assumption that replacement heifers are clean, dry, fed ad libitum, free of disease and parasites, unbred, and raised at moderate temperatures. A survey of Wisconsin dairy herds showed that much of the variation in gains could be attributed to environment rather than feeding programs. Net energy maintenance requirements were 12–24% higher for fall/spring and winter as compared to summer. Failure to adjust for these added nutrient needs could decrease ADG by 90–180 g or more. Cold stress is especially problematic for smaller heifers or when the animal has lost insulating capacity of its coat due to excess mud or moisture. Temperature has an influence on DMI. However, it was found that although temperature had a statistically significant influence on intake, it is of less importance than for lactating dairy cattle. In heifers, intake does not increase appreciably unless the temperature is less than – 10 C for more than several days. Likewise, heifers are not as prone to experiencing a meaningful depression in daily DMI during hot weather as they delay eating during the day and consume the majority of their ration during the cooler hours of the evening. Housing type has a strong influence on growth and feed efficiency. Heifers housed in well-designed confinement systems are not subjected to wind, rain, snow, or solar radiation. Nutrient expenditures for exercise are also reduced compared to pasture or more open housing systems. Several studies at Virginia Tech conducted in a counter-sloped heifer barn have demonstrated that heifers reared in housing systems with a resting area of 4.2 m2 per head had 10–20% higher feed efficiency than expected according to published nutrient requirements. This is attributed to lower maintenance costs and
408 Replacement Management in Cattle | Growth Diets
less exercise. Similarly, housing can have a dramatic influence on animal performance in heifers changing from confinement systems to systems that are more extensive, such as might happen when heifers reared in confinement during the winter are moved to a pasture system. Research at Virginia Tech has shown that when Holstein heifers reared in a counter-sloped heifer barn with 4.2 m2 or less per heifer were moved to a pasture system, they lost between 500 and 1000 g day 1 for the first 30 days. This was primarily due to increased activity of the heifers. This experience has demonstrated the need for transition housing under these circumstances and the need for substantial increases in energy in the diet during the transition. The latest version of Nutrient Requirements of Dairy Cattle (2001) has included adjustments for environmental conditions in its estimates of nutrient requirements for growth. In addition to expected growth, the user is requested to enter estimates for previous temperature, coat condition, hair depth, and evidence of heat stress and nighttime cooling. These factors are considered when estimating maintenance requirements for the growing heifer and represent a significant improvement. In addition, the program may be used for grazing animals as it includes distance animals are expected to walk and the topography of the land being grazed in estimating energy requirements. Unlike the high-producing dairy cow, the nutrient requirements of the growing heifer can be met at less than the animal’s intake capacity. Recent research has demonstrated that feeding dairy heifers at less than ad libitum intake results in reduced fecal output and improvements in feed efficiency. Diets are formulated to provide adequate nutrients for the desired rate of gain at 80–90% of ad libitum intake using higher-quality forages and/or more-concentrate-type ingredients. Since these diets are typically consumed within a relatively short period of time, the limit-fed systems require that feeding facilities have sufficient feed bunk space for all animals to eat simultaneously and that the bedding used is not edible. In contrast, the advantages of balancing rations for ad libitum intake are that less expensive by-products and high-fiber feeds can be utilized to reduce ration cost. Growers and producers believe that it also encourages body development, but research has not confirmed this anecdotal observation. The economic advantages of either system depend upon ingredient costs and existence of facilities with sufficient feed bunk space. A significant negative side effect of limit feeding is that heifers become bored quickly and will readily consume fences and housing facilities if they are constructed of wood. Probably one of the most important components of the heifer-feeding program is the implementation of a system to weigh and measure heifers on a routine basis. For the lactating herd, the dairy herd improvement (DHI)
program has provided a valuable decision-making tool for herd management. Similarly, heifer weights and heights are essential to successful heifer growing systems. Scales should be electronic with facilities to enable weighing animals easily with minimal stress to the animal or grower. Such management information is necessary if the grower is to respond in a timely manner to the environmental and health-related factors that might impair heifer growth or lead to overfattening. An excellent example of the effectiveness of routine body weight monitoring is the management system of the New Zealand Grazing Company that has contract raised over 300 000 heifers on pasture-grazing systems. All heifers are weighed (monthly up to 10 months of age and subsequently bimonthly) by a technician using electronic scales. Using an internet management system, the company is able to analyze the performance of each heifer compared to predetermined benchmarks, which means that the data are quickly translated into management information for the grower and enables a meaningful report to the owner of the heifers. This has enabled the New Zealand Grazing Company to guarantee performance of heifers and build a business that raises 5000–10 000 heifers annually. By 2009, the New Zealand dairy industry has widely accepted the principle of regular monitoring and reporting heifer growth performance, and consequently most dairy farmers outsource their dairy replacement growing allowing increased profitability from their dairy herd. Feeding programs for heifers must first achieve the ultimate goal of providing an animal capable of expressing her genetic potential at a reasonable age. Current research indicates that this is somewhere between 22 and 24 months of age and a body weight of 550 kg after calving for Holsteins and 350 kg after calving for Jerseys. Future research may yield ways in which age at calving may be reduced without significant risk to mammary development. At the present time, average ages of first calving below 22 months are not advisable for large-breed heifers. The second requirement for success involves aggressively seeking out low-cost ingredients, which will enable attainment of growth goals. Profitable heifer-growing operations will thrive in locations adjacent to sources of by-products or low-cost pasture, which will enable economical feeding programs. The third requirement for success involves monitoring body weights of the growing heifers. Facilities must be incorporated into heifer management system that enable weighing and measuring animals.
Conclusion Heifer feeding management requires a different mindset than feeding cows. Heifer performance is not monitored well enough and we are not sure of the effects of
Replacement Management in Cattle | Growth Diets
heifer management decisions on the heifer’s ability to lactate. 1. The importance of forage quality declines in importance as the heifer ages. Significant opportunities for economy exist for growers willing to consider unusual by-product feeds and forages of insufficient quality to use in the lactating herd rations. 2. Transition to group housing requires well-designed facilities that permit easy accommodation of outliers from the average. 3. Control of the rate of gain from weaning to onset of puberty is critical. Too much energy and too rapid a rate of gain enhance the onset of puberty, but at the risk of impaired mammary development. Increasing protein avoids overfattening to a point, but still may not result in normal udder growth. Too little energy and protein or poor environmental conditions reduce gains and delay breeding and calving, resulting in significant increases in rearing costs. 4. Bred heifers offer significant opportunities for economizing feeding as nutrient density of rations is more moderate. 5. Feeding systems should be labor efficient, enable monitoring of intake and growth of heifers, and permit documentation of rearing expenses.
See also: Replacement Management in Cattle: Breeding Standards and Pregnancy Management; Growth Standards and Nutrient Requirements; Health Management; Pre-Ruminant Diets and Weaning Practices.
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Further Reading Bethard GL, James RE, and McGilliard ML (1997) Effect of rumenundegradable protein and energy on growth and feed efficiency of growing Holstein heifers. Journal of Dairy Science 80: 2149. Bickert WG (1990) Feed manger and barrier design. In: Dairy Feeding Systems, NRAES-38: Proceedings of the Dairy Feeding Systems Symposium. Harrisburg, PA, USA, 10–12 January. Ithaca, NY: NRAES. Hall MH (2009–2010) The Agronomy Guide. University Park, PA: The Department of Crop and Soil Sciences, Pennsylvania State University. Hoffman PC (1999) Protein requirements of dairy replacement heifers. In: Proceedings of the Four State Applied Nutrition and Management Conference, pp. 97–103. Dubuque, IA, 3–4 August. Hoffman PC, Brehm NM, Howard WT, and Funk DA (1994) The influence of nutrition and environment on growth of Holstein replacement heifers in commercial dairy herds. The Professional Animal Scientist 10: 59. Hoffman PC, Simson CR, and Wattiaux M (2007) Limit feeding of gravid Holstein heifers: Effects of growth, manure nutrient excretion, and subsequent early lactation performance. Journal of Dairy Science 90: 946–954. Kertz AF, Barton BA, and Reutzel LF (1998) Relative efficiencies of wither height and body weight increase from birth until first calving in Holstein cattle. Journal of Dairy Science 81: 1479–1482. Moody ML, Zanton GL, Daubert JM, and Heinrichs AJ (2007) Nutrient utilization of differing forage-to-concentrate ratios by growing Holstein heifers. Journal of Dairy Science 90: 5580–5586. Morrill JL (1999) Managing the calf from weaning through four months of age. In: Proceedings of the Third Annual Conference of the Professional Dairy Heifer Growers Association, pp. 23–30. Savoy, IL: FASS. National Research Council (2001) Nutrient Requirements of Dairy Cattle, 7th edn. Washington, DC: National Academy Press. Quigley JD, III, James RE, and McGilliard ML (1986) Dry matter intake in dairy heifers: 1. Factors affecting intake of heifers under intensive management. Journal of Dairy Science 69: 2855–2862. Wickham IW (1997) Marketing a custom heifer business. In: Proceedings of the First Conference of the Professional Dairy Heifer Growers Association, pp. 13–22. Savoy, IL: FASS.
Relevant Websites http://www.nzgrazing.co.nz – New Zealand Grazing Company Limited.
Introduction Dairy heifers should be fed and managed to achieve 55% of their mature weight at first breeding and 82–85% of their mature weight at first calving. These principles enable the establishment of growth goals regardless of breed. In addition, heifers should have a body condition score after calving of 3.5 and be free of disease. Probably, no factor other than the feeding program influences achievement of these goals. The feeding program also comprises 50–70% of the cost of rearing heifers to first calving. Therefore, profitable heifer-rearing enterprises must concentrate on economical feeding programs. The purpose of this article is not to provide a ‘how to’ description of heifer-feeding programs because available feed resources and facilities vary to a great extent. This article will focus on a discussion of decision-making areas with considerable importance to the financial success of the heifer-feeding programs. Managing the feeding program of the heifer enterprise is not unlike that of any other decision made on the farm. Good heifer managers maximize benefits, control expenses, and manage risk well. This article will concentrate on the major goals the heifer grower needs to achieve during the rearing period: 1. successful weaning from liquid diets to forage- and concentrate-based feeding programs with minimal stress and loss of weight, and transition to group housing management systems; 2. controlling the rate of gain during the prepubertal period to enable early breeding (12–13 months) while assuring desired mammary development; 3. sustained growth after breeding and optimization of economy of feeding; and 4. preparing the heifer for eventual calving. The development of the feeding program should consider that approximately 50% of the total gain in height occurs during the first 6 months of life with 25% occurring from 7 to 12 months and the remaining 25% during the 12 months before calving. Feed cost is generally lowest per unit of gain during the first 6 months of life and then increases at a decreasing rate during the remaining 18 months. The proportion of body weight to wither height increases linearly and the increase in wither height as a proportion of total height is greatest during the first 6 months. This demonstrates that assuring adequate growth during the first 6 months is critical to success in growing
the dairy heifer and is where nutrition and management must be optimal. Poor growth prior to puberty cannot be compensated for later in the rearing period. After puberty and when the heifer has attained early growth goals, opportunities for considerable economy of feeding exist. Profitable heifer management requires labor-efficient systems and the ability to evaluate ration dry matter intake (DMI) and animal performance. Periodic weighing of heifers with comparison to established growth goals is critical to achieving desired performance. Heifer-feeding programs vary widely depending on the environment and available forage resources. In tropical and more temperate areas of the world, pasture-based systems are more popular because they provide nutrients at the lowest cost and promote excellent animal health. In other areas where land resources are more valuable, or the length of the grazing season is limited, confinement systems may be more conducive to economical heifer growth. In many areas of the world, a combination of systems where heifers are raised on pasture during the warmer months and moved to confinement during the winter is commonly practiced. Basic principles of nutritional management using pasture-based and confinement systems will be discussed.
Managing the Transition Calf This stage refers to the time between 2 weeks prior to and 2 weeks after weaning. Success during this phase is dependent upon excellent housing and health programs. Regardless of the rearing system, it is assumed that the calf is consuming adequate amounts of a high-energy calf starter grain prior to weaning. When preweaned calves have been housed individually, it is recommended that calves be placed into small groups of 4–6 calves several weeks after weaning to allow them to adjust to competition for feed. However, when the environment is optimal, the author has observed newly weaned calves reared in groups of 20–30 with great success. Under this scenario, ventilation is outstanding, bedded pens are cleaned frequently, and calf starter grain is fed often to keep the feed fresh. Calves that have been fed their liquid diet in groups from mob or robotic feeders adapt to weaning quite well as there is no social stress associated with adapting to the group housing and feeding environment. Calf starter grains can vary widely, but should be highly palatable and digestible,
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404 Replacement Management in Cattle | Growth Diets Table 1 Desired nutrient levels in a calf starter grain
Nutrient
Amount recommended
Crude protein (% of DM) Fat (% of DM) TDNs (% of DM) Metabolizable energy (Mcal kg Calcium (% of DM) Phosphorus (% of DM) Vitamin A (IU kg 1) Vitamin D (IU kg 1) Vitamin E (IU kg 1)
18.0–22.0 3.0 80 3.1 0.60 0.40 2200 300 24
1
DM)
DM, dry matter; TDNs, total digestible nutrients.
with nutrient concentrations as shown Table 1. Under more intensive liquid-feeding programs for calves, protein levels may be increased to 22% of dry matter (DM). For calves that have been housed individually prior to weaning, Morrill suggests three transition pens after weaning. The first pen has 4–8 calves with 2.8 m2 per calf and a starter the same as they had been receiving prior to weaning. Two weeks later, the calves are moved to a larger pen with more calves and with the same starter and about 15% chopped alfalfa hay added to the ration. In the next transition pen, the amount of chopped alfalfa is increased to 20% of the mixture. By the time the calves are moved to the last transition pen, they can be switched to a more economical grower concentrate mixture, with examples shown in Table 2.
Table 2 Examples of calf starter grain mixtures Feed
Grower 1
Grower 2
Cracked corn Rolled oats Rolled barley Molasses Soybean meal Canola meal Limestone Dicalcium phosphate Salt Trace mineral mix Vitamin E mix Vitamin ADE mix Additives
63.8 9.9
53.23
3.5 20.4 1.2 0.27 0.18 0.09 0.09 0.07 0.50
20.48 2.97 21.33 1.08 0.18 0.09 0.09 0.07 0.46
Values are percentage of total mixture on an as-fed basis. Composition of trace mineral mixture (%): Co, 0.01; Cu, 1; Fe, 5; I, 0.06; Mn, 4; Se, 0.03; Zn, 4. Composition of vitamin ADE mixture, per kg: A, 44 000 KIU; D, 990 KIU; E, 17 600 IU. Vitamin E supplement contains 44 000 IU kg 1. Grower grain mixture should contain coccidiostat or other additive as desired. Reproduced from Morrill J (1999) Proceedings of the Third Conference of the Professional Dairy Heifer Growers Association, p. 26. Minneapolis, MN. Savoy, IL: Professional Dairy Heifer Growers Association.
Workers at North Carolina State University have successfully developed a self-fed calf starter grain utilizing cottonseed hulls to limit intake. Calves are offered the starter from birth through 4–6 months of age. Cottonseed hulls represent a uniform, consistent source of more slowly digested fiber that helps limit intake in the older heifers. Critical to success of the system is maintaining a reliable source of clean cottonseed hulls, keeping the selffeeders clean, and providing plenty of water. Nutrient content of these starter mixtures on a DM basis is 16–18% crude protein (CP), 76% total digestible nutrients (TDNs), 0.66% calcium, and 0.42% phosphorus. The ingredient composition is 493 kg ground corn, 300 kg cottonseed hulls, 184 kg soybean meal, 9 kg calcitic limestone, 5 kg tricalcium phosphate, and 5 kg white salt, ionophore, and a vitamin–trace mineral mixture. Although apparently successful, these starters are lower in energy and require higher intakes to meet the energy requirements for acceptable growth.
Managing Growth of the Heifer from Weaning to Breeding Once the heifer has been successfully weaned and has transitioned to group housing, control of rearing rate is of primary concern. If one assumes that a goal of age at first calving of 22–24 months is desirable, breeding should be initiated at 12–13 months. Animals must be of adequate weight and body condition to accomplish this objective. Table 3 demonstrates the challenges faced in feeding the large-breed heifer prior to breeding. It also demonstrates the difficulty in attaining ages at first calving below 20 months. Based upon these assumptions, it is assumed that rations for the large-breed heifers should foster a gain of 750–900 g day 1. Smaller breed heifers require gains of 500–650 g day 1. Excessive gains may increase the risk for problems with mammary development, particularly if protein is limiting in the ration. Pasture-based systems
In many areas of the world, the greatest forage asset is the availability of abundant, low-cost land suitable for pastures. The best example for pasture systems exists in Table 3 ADG necessary to achieve suggested 360 kg weight at breeding and postcalving body weight of 570 kg at varying ages Age at calving goal (months) Age at breeding goal (months) ADG birth–breeding (g) ADG breeding–calving (g)
20 11 953 884
22 13 800 884
24 15 680 884
Assumes 39 kg birth weight, 45.4 kg loss of weight at calving, and 280 days of gestation. ADG, average daily gain.
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Ireland, New Zealand, southern Chile, and Argentina, and similar climes that have cool temperatures with frequent, moderate rainfall during a large portion of the year. Less desirable examples of grazing systems are range management systems in arid areas, which require extensive land bases exceeding 20 hectares per animal and they support little more than maintenance nutrient requirements. In many areas of the world, the role of pasture in heifer-feeding systems is probably in between these extremes. It is important to evaluate realistically the advantages and liabilities of pasture systems and determine how best to optimize their benefits and minimize the risk of their shortcomings. The biggest challenge faced in the pasture system is reliably estimating the carrying capacity of the land. If land is to be utilized for pasture, its use during the year must be maximized to provide the best compromise of yield of animal growth and forage nutrient yield. Figure 1 shows the effect of grazing pressure on production per animal and per acre. Note that optimal growth per head is not the same as optimal growth per acre. Optimum growth per animal occurs at a point less than optimum for land utilization. When grazing pressure is low to medium, heifers graze on only the best quality forage. When pasture output is optimized at higher stocking rates, heifers are forced to consume some of the less nutritious forage and animal performance declines. This represents a challenge for the heifer grower or dairy producer. Extremes in stocking rate are undesirable. Long periods of low grazing pressure lead to a loss of legumes in a stand and increased growth of weeds and less desirable species. Long periods of high grazing pressure result in temporary or long-term decreases in forage production as nutrient reserves of desirable forage species are depleted and plants become less dominant in the sward. For optimum grazing, one should maintain available forage at
Production
High
Output per head
Output per acre
Medium
Available pasture
Low
Neg
High
Medium
Low
Very low
Low
Medium
High
Very high
Stocking rate
Figure 1 Effect of grazing pressure on production per animal and per acre. Reproduced from Hall MH (2009–2010) The Agronomy Guide. University Park, PA: Department of Crop and Soil Sciences, The Pennsylvania State University.
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approximately 1122–1685 kg DM per hectare. This is the equivalent of a 7–10 cm high stand of bluegrass/ white clover or 15–20 cm of tall grasses and legumes. Continuous or rotational grazing?
Historically, continuous grazing has been the most popular grazing system since it is simple and requires little labor. Grazing pressure is adjusted by adding or subtracting animals or temporarily fencing off areas for hay harvest. However, continuous grazing is a land extensive system, and low production of gain per hectare makes it inefficient. In contrast, rotational grazing can dramatically increase animal performance and forage DM yield per hectare. In heifer feeding systems, intensive rotational grazing systems are probably not as important. Improvements in nutrient quality of forage accrued from more daily movement of fences or shifting heifers to new paddocks daily do not offset the labor and fencing expense and convenient provision of water. Many heifer growing systems include some combination of both continuous and rotational systems. A continuously grazed paddock may be used to house animals during the winter or during periods of drought to enable other areas to recover forage growth. Other paddocks are designed to enable movement of fences on less frequent interval of 3–14 days. Supplemental nutrition of pasture systems
For many areas of the world, dairy heifers cannot be reared without significant nutrient supplementation during some portion of the year. The nutrient variation of grazed forage species represents one of the greatest challenges of grazing, particularly for animals less than 1 year of age. In the more temperate areas of the world, protein concentrations of pasture can vary from 6% to levels exceeding 20%, while the growing dairy heifer may require levels ranging from 12 to 18%. Similarly, energy values will range from those similar to corn silage to levels that more nearly resemble straw. Although heifer rearing regimes might tolerate some variation in growth, in today’s economic climate it is important that heifers calve at an early age and with desired body size and condition. When forage availability is adequate, but quality is lacking, provision of supplemental energy and protein through concentrate feeding is advised. At other times such as winter months or during severe drought, heifers require supplementation with both forages and concentrates. It is beyond the scope of this article to address adequately the supplemental nutrient needs of pasturereared heifers. Pasture-reared heifers require more energy than those in confinement due to their increased activity and exposure to environmental conditions, particularly during the winter. Research at Virginia Tech has shown that
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confinement-reared heifers require 12–25% less energy than indicated by National Research Council (NRC). They are also less influenced by severe cold and wet weather. Therefore, managers of pasture-reared heifers must make adjustments in nutritional strategies when environmental conditions are less than perfect. Factors such as cold weather, nonthermal resting areas, wind, rain, and snow increase demand for energy for maintenance thereby reducing that available for growth. Environmental conditions for heifers raised without housing may become so severe that it is not possible to maintain sufficient growth, even with substantial energy and protein supplementation. Supplementation of rations with energy must be based upon observed growth of heifers during inclement weather. Similarly, supplementation can often be reduced at considerable savings when pasture growth and environment are optimal. The greatest challenge of pasture systems lies in the establishment of pastures that enable maximal grazing throughout the season and provisions for supplementation when pasture nutrients are insufficient to promote desired growth. Depending upon the climate and resources, successful growers utilize a mixture of swards containing cool and warm season perennial grasses and legumes. Young calves readily adapt to pasture systems as they provide ample opportunity for exercise, excellent air quality, and when pasture growth is young and rapid, a plentiful supply of energy, protein, mineral, and vitamins. However, it is important to note that calves weighing less than 150 kg require nutrients at least as high as that for the lactating cow (>16% CP and >2 Mcal of metabolizable energy (ME) per kg of DMI). An additional consideration for younger calves is their susceptibility to parasitism. Aggressive parasite control programs are recommended because the young animals have not developed sufficient immunity more common in animals in their second grazing season. By 300 kg body weight, concentration of nutrients is less important as adequate intake (7 kg DM per day) of forage providing 12% protein and 2 Mcal ME per kg DMI is adequate for 700 g of gain per day. It is uncommon to formulate rations for grazing dairy heifers. Rather the manager assesses pasture quality and availability, and heifer growth to determine if supplemental nutrition is needed. Confinement rearing systems
Young heifers, less than 150 kg body weight, require diets of high forage quality to enhance rumen function and promote economical growth. Forages must be free of mold and spoilage to ensure adequate ration intake. Fermented feeds and a wide variety of by-product feeds are readily accepted by heifers more than 150 kg body weight. Forage quality, as defined by nutrient content, becomes less important for the heifer over 150 kg body
weight as intake is usually not the limiting factor in nutrition. Professional heifer growers have been especially aggressive in seeking ways to provide nutrients at the lowest possible costs. This strategy requires the grower to ‘think outside the box’ when it comes to selecting ration components. Rations are presented to demonstrate the possibilities for utilization of by-product feeds. They are based upon those used by several large heifer growers in Colorado and Texas as well as conventional rations used in heifer feeding trials at Virginia Tech. Each ration was evaluated using the Cornell Penn Minor (CPM) program to determine expected gains based on ME and metabolizable protein (MP). Ration I relied heavily on by-products from vegetable processing, wet brewer grains, and low-cost alfalfa silage, which were of insufficient quality for lactating dairy cattle or export. Frequent weighing of heifers revealed growth of 800 g day 1, while the CPM model indicated that ME supplied by the ration should provide for only 690 g of gain per day and sufficient MP for 1.17 kg of gain per day. Ration II used an exceptional array of by-product feeds. Alfalfa was of lower quality, as was the whole cottonseed. Outdated dairy products (ice cream, cottage cheese, yogurt, and other products) were also used as available in this ration. In comparison to ration I, this ration contained an abundance of protein of a very degradable nature. Sufficient ME and MP were present to support gains in excess of 1 kg day 1, which supported observations on the feedlot of rapid gains, and heavy body condition. Ration III represents the traditional ration fed to dairy heifers in Virginia. MP and ME were present in sufficient amounts to support daily gains in excess of 900 g. These rations demonstrate the ability of heifers to grow at rates that support early calving at recommended body sizes at very low ration costs. The greatest limitation involved in the successful use of by-product feeds is personal prejudices and preconceived ideas of what will be successful. Once it has been determined that by-products contain no harmful substances and that product quality is predictable, many by-products serve as economical ingredients for heifer rations (Table 4). Feeding the Breeding Age Heifer and Bred Heifer Growers should not need to increase nutrient levels for the breeding age heifer, since she should already be on a high plane of nutrition promoting 750–900 g of average daily gain (ADG) for large-breed heifers or 500–650 g of ADG for small-breed heifers. Once the heifer is bred, it is important to maintain these growth rates, although it is possible to tolerate some variation as long as goals for growth are attained at calving. As shown earlier, attaining a breeding weight of 363 kg at 13 months of age requires an ADG exceeding 800 g. However, attaining
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Table 4 Example rations for growing a 225 kg heifer at an average daily gain of 815 g
Ration I
kg DM
CP (%)
RUP (% of CP)
TDNs (%)
ME (Mcal lb 1)
NDF (%)
Cost ($ day 1)
6.0
11.2
45.4
66
2.2
46
0.72
Ground wheat straw, 1.45 kg; wet brewers’ grain, 2.9 kg; carrots, 1.8 kg; wet beet pulp, 1.8 kg; corn screenings, 1.1 kg; alfalfa silage, 3.6 kg; Rumensin was included in the mix. Ration II
5.85
17.2
29.4
68
2.6
35.91
74
Cotton gin trash, 730 g; rolled corn, 1.27 kg; distillers’ grains, 454 g; whole cottonseed, 363 g; alfalfa hay, 1 kg; wheat midds, 1.63 kg; cottonseed meal, 363 g; sorghum silage, 1.27 kg; waste dairy products, 1.82 kg. Ration III
13.6
12.0
33.9
67
2.44
41.3
90
Corn silage, 6.82 kg; soybean meal, 454 g; ground shelled corn, 1.6 kg; orchard grass hay, 2.27 kg. All rations were fed as total mixed rations for ad libitum intake, with prevailing feed prices as of August 2009. DM, dry matter; CP, crude protein; RUP, rumen-undegradable protein; TDNs, total digestible nutrients; ME, metabolizable energy; NDF, neutral detergent fiber.
the postcalving weight of 570 kg requires heifers to continue to gain 750–900 g day 1. Opportunities to utilize by-product feeds in total mixed rations continue. These heifers can tolerate variations in gain, and rapid compensatory growth prior to calving is well tolerated provided that heifers do not become overconditioned.
Feeding Management Considerations Grouping heifers is a challenging issue to resolve, as it is a compromise between facilities, labor, and nutrient efficiency. Heifers should be placed in as many groups as is efficient from a labor standpoint. Suggested grouping are transition heifers, 4–8 months, 9–12 months, breeding-age heifers, and pregnant heifers. If possible, place heifers in groups within a range of 50 kg. Group heifers by size and body condition, paying close attention to note heifers significantly older within a group that may need to be culled. When multiple breeds are present in a herd, it is important to remember that smaller breeds mature more rapidly than larger breeds. If heifers are grouped by size, smaller breed heifers such as Jerseys will frequently become overconditioned. It is recommended that Jerseys and other earlier-maturing breeds are housed with slightly larger and older large-breed heifers. Provision of sufficient feed bunk space is an important consideration in such situations. Factors influencing growth and feed efficiency of dairy heifers
A common misconception regarding dairy heifer nutrition is that published nutrient requirements provide sufficient nutrients to assure the stated rate of gain under a wide variety of environments. One must
remember that these recommendations are based on the assumption that replacement heifers are clean, dry, fed ad libitum, free of disease and parasites, unbred, and raised at moderate temperatures. A survey of Wisconsin dairy herds showed that much of the variation in gains could be attributed to environment rather than feeding programs. Net energy maintenance requirements were 12–24% higher for fall/spring and winter as compared to summer. Failure to adjust for these added nutrient needs could decrease ADG by 90–180 g or more. Cold stress is especially problematic for smaller heifers or when the animal has lost insulating capacity of its coat due to excess mud or moisture. Temperature has an influence on DMI. However, it was found that although temperature had a statistically significant influence on intake, it is of less importance than for lactating dairy cattle. In heifers, intake does not increase appreciably unless the temperature is less than – 10 C for more than several days. Likewise, heifers are not as prone to experiencing a meaningful depression in daily DMI during hot weather as they delay eating during the day and consume the majority of their ration during the cooler hours of the evening. Housing type has a strong influence on growth and feed efficiency. Heifers housed in well-designed confinement systems are not subjected to wind, rain, snow, or solar radiation. Nutrient expenditures for exercise are also reduced compared to pasture or more open housing systems. Several studies at Virginia Tech conducted in a counter-sloped heifer barn have demonstrated that heifers reared in housing systems with a resting area of 4.2 m2 per head had 10–20% higher feed efficiency than expected according to published nutrient requirements. This is attributed to lower maintenance costs and
408 Replacement Management in Cattle | Growth Diets
less exercise. Similarly, housing can have a dramatic influence on animal performance in heifers changing from confinement systems to systems that are more extensive, such as might happen when heifers reared in confinement during the winter are moved to a pasture system. Research at Virginia Tech has shown that when Holstein heifers reared in a counter-sloped heifer barn with 4.2 m2 or less per heifer were moved to a pasture system, they lost between 500 and 1000 g day 1 for the first 30 days. This was primarily due to increased activity of the heifers. This experience has demonstrated the need for transition housing under these circumstances and the need for substantial increases in energy in the diet during the transition. The latest version of Nutrient Requirements of Dairy Cattle (2001) has included adjustments for environmental conditions in its estimates of nutrient requirements for growth. In addition to expected growth, the user is requested to enter estimates for previous temperature, coat condition, hair depth, and evidence of heat stress and nighttime cooling. These factors are considered when estimating maintenance requirements for the growing heifer and represent a significant improvement. In addition, the program may be used for grazing animals as it includes distance animals are expected to walk and the topography of the land being grazed in estimating energy requirements. Unlike the high-producing dairy cow, the nutrient requirements of the growing heifer can be met at less than the animal’s intake capacity. Recent research has demonstrated that feeding dairy heifers at less than ad libitum intake results in reduced fecal output and improvements in feed efficiency. Diets are formulated to provide adequate nutrients for the desired rate of gain at 80–90% of ad libitum intake using higher-quality forages and/or more-concentrate-type ingredients. Since these diets are typically consumed within a relatively short period of time, the limit-fed systems require that feeding facilities have sufficient feed bunk space for all animals to eat simultaneously and that the bedding used is not edible. In contrast, the advantages of balancing rations for ad libitum intake are that less expensive by-products and high-fiber feeds can be utilized to reduce ration cost. Growers and producers believe that it also encourages body development, but research has not confirmed this anecdotal observation. The economic advantages of either system depend upon ingredient costs and existence of facilities with sufficient feed bunk space. A significant negative side effect of limit feeding is that heifers become bored quickly and will readily consume fences and housing facilities if they are constructed of wood. Probably one of the most important components of the heifer-feeding program is the implementation of a system to weigh and measure heifers on a routine basis. For the lactating herd, the dairy herd improvement (DHI)
program has provided a valuable decision-making tool for herd management. Similarly, heifer weights and heights are essential to successful heifer growing systems. Scales should be electronic with facilities to enable weighing animals easily with minimal stress to the animal or grower. Such management information is necessary if the grower is to respond in a timely manner to the environmental and health-related factors that might impair heifer growth or lead to overfattening. An excellent example of the effectiveness of routine body weight monitoring is the management system of the New Zealand Grazing Company that has contract raised over 300 000 heifers on pasture-grazing systems. All heifers are weighed (monthly up to 10 months of age and subsequently bimonthly) by a technician using electronic scales. Using an internet management system, the company is able to analyze the performance of each heifer compared to predetermined benchmarks, which means that the data are quickly translated into management information for the grower and enables a meaningful report to the owner of the heifers. This has enabled the New Zealand Grazing Company to guarantee performance of heifers and build a business that raises 5000–10 000 heifers annually. By 2009, the New Zealand dairy industry has widely accepted the principle of regular monitoring and reporting heifer growth performance, and consequently most dairy farmers outsource their dairy replacement growing allowing increased profitability from their dairy herd. Feeding programs for heifers must first achieve the ultimate goal of providing an animal capable of expressing her genetic potential at a reasonable age. Current research indicates that this is somewhere between 22 and 24 months of age and a body weight of 550 kg after calving for Holsteins and 350 kg after calving for Jerseys. Future research may yield ways in which age at calving may be reduced without significant risk to mammary development. At the present time, average ages of first calving below 22 months are not advisable for large-breed heifers. The second requirement for success involves aggressively seeking out low-cost ingredients, which will enable attainment of growth goals. Profitable heifer-growing operations will thrive in locations adjacent to sources of by-products or low-cost pasture, which will enable economical feeding programs. The third requirement for success involves monitoring body weights of the growing heifers. Facilities must be incorporated into heifer management system that enable weighing and measuring animals.
Conclusion Heifer feeding management requires a different mindset than feeding cows. Heifer performance is not monitored well enough and we are not sure of the effects of
Replacement Management in Cattle | Growth Diets
heifer management decisions on the heifer’s ability to lactate. 1. The importance of forage quality declines in importance as the heifer ages. Significant opportunities for economy exist for growers willing to consider unusual by-product feeds and forages of insufficient quality to use in the lactating herd rations. 2. Transition to group housing requires well-designed facilities that permit easy accommodation of outliers from the average. 3. Control of the rate of gain from weaning to onset of puberty is critical. Too much energy and too rapid a rate of gain enhance the onset of puberty, but at the risk of impaired mammary development. Increasing protein avoids overfattening to a point, but still may not result in normal udder growth. Too little energy and protein or poor environmental conditions reduce gains and delay breeding and calving, resulting in significant increases in rearing costs. 4. Bred heifers offer significant opportunities for economizing feeding as nutrient density of rations is more moderate. 5. Feeding systems should be labor efficient, enable monitoring of intake and growth of heifers, and permit documentation of rearing expenses.
See also: Replacement Management in Cattle: Breeding Standards and Pregnancy Management; Growth Standards and Nutrient Requirements; Health Management; Pre-Ruminant Diets and Weaning Practices.
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Further Reading Bethard GL, James RE, and McGilliard ML (1997) Effect of rumenundegradable protein and energy on growth and feed efficiency of growing Holstein heifers. Journal of Dairy Science 80: 2149. Bickert WG (1990) Feed manger and barrier design. In: Dairy Feeding Systems, NRAES-38: Proceedings of the Dairy Feeding Systems Symposium. Harrisburg, PA, USA, 10–12 January. Ithaca, NY: NRAES. Hall MH (2009–2010) The Agronomy Guide. University Park, PA: The Department of Crop and Soil Sciences, Pennsylvania State University. Hoffman PC (1999) Protein requirements of dairy replacement heifers. In: Proceedings of the Four State Applied Nutrition and Management Conference, pp. 97–103. Dubuque, IA, 3–4 August. Hoffman PC, Brehm NM, Howard WT, and Funk DA (1994) The influence of nutrition and environment on growth of Holstein replacement heifers in commercial dairy herds. The Professional Animal Scientist 10: 59. Hoffman PC, Simson CR, and Wattiaux M (2007) Limit feeding of gravid Holstein heifers: Effects of growth, manure nutrient excretion, and subsequent early lactation performance. Journal of Dairy Science 90: 946–954. Kertz AF, Barton BA, and Reutzel LF (1998) Relative efficiencies of wither height and body weight increase from birth until first calving in Holstein cattle. Journal of Dairy Science 81: 1479–1482. Moody ML, Zanton GL, Daubert JM, and Heinrichs AJ (2007) Nutrient utilization of differing forage-to-concentrate ratios by growing Holstein heifers. Journal of Dairy Science 90: 5580–5586. Morrill JL (1999) Managing the calf from weaning through four months of age. In: Proceedings of the Third Annual Conference of the Professional Dairy Heifer Growers Association, pp. 23–30. Savoy, IL: FASS. National Research Council (2001) Nutrient Requirements of Dairy Cattle, 7th edn. Washington, DC: National Academy Press. Quigley JD, III, James RE, and McGilliard ML (1986) Dry matter intake in dairy heifers: 1. Factors affecting intake of heifers under intensive management. Journal of Dairy Science 69: 2855–2862. Wickham IW (1997) Marketing a custom heifer business. In: Proceedings of the First Conference of the Professional Dairy Heifer Growers Association, pp. 13–22. Savoy, IL: FASS.
Relevant Websites http://www.nzgrazing.co.nz – New Zealand Grazing Company Limited.