Raising dairy heifers from birth to calving has been found to comprise the second largest expense on the dairy farm towards the production of milk--all while deriving no revenue until the onset of lactation (Heinrichs, 1993). Therefore, many of the experiments involving dairy heifers have focused on ways to minimize the costs associated with the growth period or decreasing the unproductive period of the animal's life. Reducing the length of the growing period by decreasing the age at first calving below recommendations (22 to 24 months) could overcome this lag between expenditure and revenue generation and reduce the costs associated with the nonproductive period. This could be accomplished by increasing prepubertal average daily gain (ADG; Hoffman, 1997), which would subsequently result in a lower age at first breeding and presumably a lower age at first calving.
Although this strategy would ultimately accelerate the return on investment, it has been demonstrated that increased prepubertal ADG has a negative impact on mammary development (Radcliff et al., 1997; Sejrsen et al., 1982) and first lactation milk yield (Van Amburgh, 1998; Radcliff, 2000; Lammers, 1999).
In summarizing recent literature on the association between prepubertal ADG and first lactation milk production, total first lactation milk and protein yield were found to be maximized when prepubertal ADG was around 800 g/d for Holstein heifers (Zanton and Heinrichs, 2005). Many researchers, however, are looking for ways to allow for greater ADG while maintaining optimal levels of mammary development and milk production.
To date many of the approaches have shown little progress, conflicting results, or impracticable recommendations to enable a producer to overcome the problems associated with accelerated prepubertal growth.
Since accelerating prepubertal ADG necessitates nutritional alterations, most of the experiments investigating the effects of prepubertal growth have also altered the nutritional status of the heifers in one or several groups. For instance, some studies altering prepubertal ADG have fed rations of vastly different composition for ad libitum consumption (i.e. high forage or high concentrate rations); others have fed an identical diet to each experimental group restrictively to obtain the different ADG. What is minimally represented in the literature are the effects that different proportions of forage and concentrate have on milk production, when fed to maintain a constant rate of growth. Serjsen and Foldager (1992) investigated this question using eight animals per treatment through 130 days of the first lactation. They concluded that there were no differences in milk production between the group that was fed the high or the low forage rations and achieved equal ADG during rearing.
Since feed costs make the greatest contribution to the expenses associated with raising heifers; comprising about 60% of the all heifer expenditures (Gabler et al., 2000), it would follow that a reduction in feed costs could significantly contribute to decreasing the overall cost for raising dairy heifers. Since there is an optimum ADG for heifer growth, feed costs should be expressed in a manner which considers both the cost of feed per unit of feed weight and the amount that must be fed to obtain the optimal ADG. In the United States, concentrates are usually more cost effective per unit of energy and protein than forages. If the energy requirement is fixed by the amount needed to obtain the optimal ADG, feed costs could be reduced by replacing the more expensive forage energy with energy from concentrates. Also, if there are no differences in milk production when heifers are fed high forage or high concentrate rations during the rearing period, then the costs to raise dairy heifers could be reduced. NRC (2001) states that when energy intake increases above maintenance level, the amount of fat being deposited is higher due to a lack of protein deposition. However, restricting intakes and feeding a more nutrient dense diet may control caloric intake, reducing feed costs and nutrient excretion (Hoffman et al., 2007).
There is currently very little data in the literature concerning the effects of feeding high forage (HF) or high concentrate (HC) rations, when delivered for the same level of growth, on responses in dairy heifers. Reynolds et al. (1991a; 1991b) investigated the effects of differing the proportions of forage and concentrate in rations fed to growing beef heifers on energy metabolism at the level of the whole animal as well as for the portal-drained viscera (PDV) tissues and the liver. Reynolds et al. (1991b) found that when fed a constant level of metabolizable energy, heat production was lower for the animals fed the HC ration (25:75 vs. 75:25 forage:concentrate), resulting in significantly increased tissue energy accretion. The PDV accounted for proportionately less oxygen consumption for the HC ration, however the total splanchnic tissue (TST) consumption of oxygen did not differ between diets. Glucose release to the periphery was also significantly increased when feeding a HC ration, possibly due to the decreased glucose metabolism by the PDV, as glucose output by the liver was not significantly different between diets (Reynolds et al., 1991a). While nitrogen dynamics were discussed, the responses are difficult to resolve or to ascribe to a particular forage-to-concentrate ratio due to differences in nitrogen intake between treatments. However, while nitrogen intake was greater for the HF ration, tissue retention of nitrogen was the greatest for the HC ration. Relative to intake, heifers fed the HF ration excreted more fecal dry matter, nitrogen, and energy and more urinary nitrogen. While it is unclear if the improved nitrogen efficiencies are due to differences in nitrogen intake, the flow of some nitrogen containing compounds (ammonia, alpha-amino nitrogen, and urea) across the PDV were not significantly affected by the treatment rations fed, indicating that post-absorptive nitrogen efficiency may be improved by low forage rations.
Reynolds et al. (1991a) also found that the maximal contribution of amino acid to gluconeogenesis tended (P < 0.10) to be reduced, and significantly less (P < 0.05) alpha-amino acid nitrogen was removed by the liver in the heifers fed the HC ration. Similarly, Huntington et al. (1996) fed iso-nitrogenous and iso-energetic diets to six multi-catheterized beef steers to investigate the dynamics of nitrogen when fed varying proportions of forage and concentrate. In a comparison of diets containing 63 or 37% forage, significantly more urea nitrogen and glucose were released by the TST to the periphery when fed 37% forage, while acetate release was significantly reduced. Amino acid release by the TST was numerically, but not statistically, greater for the low forage diet.
It is critical that data can be produced where these factors are closely controlled so that nitrogen excretion for these diets can be more thoroughly understood in the context of the different levels of forage fed to growing dairy heifers. Furthermore, the combination of lower acetate with the possibility of increased amino acid release to the periphery could have effects on the composition of gain in heifers due to the preferential use of acetate for lipogenesis in ruminants (Bergman, 1990) as well as the increased availability of amino acids for protein synthesis (Owens et al., 1993).
A typical dairy heifer is fed a ration in which the majority of its nutrition is derived from forages as opposed to concentrated feedstuffs. However, there is a large inefficiency associated with this method of feeding due to lower digestibility of most forages, greater metabolic protein and energy requirements associated with digesting forage, and higher feed costs per unit of energy as compared to concentrates. The potential therefore exists to replace a significant proportion of the forage DM in a ration with concentrate DM, reducing the inefficiency associated with raising dairy heifers while maintaining similar ADG. This can allow for reduced excretion of manure and nutrients by feeding less DM of a more digestible diet. To address this concept for raising dairy heifers, a series of experiments have recently been conducted by researchers at the Pennsylvania State University and the University of Wisconsin to evaluate heifer growth characteristics and nutrient utilization when given HF or HC rations at restricted intakes to achieve a similar ADG.
To test the effects of restricting the intake of feed to dairy heifers, irrespective of the level of dietary forage and concentrate, an experiment was conducted, the objective of which was to determine the effects of differing intakes of dry matter on the nutritional and nitrogen efficiency in growing dairy heifers (Zanton and Heinrichs, 2004; Zanton and Heinrichs, 2005). Organic matter digestibility was linearly increased (P < 0.05) by decreasing levels of DMI, while NDF digestibility was unaltered by treatment. Nitrogen excretion in the feces and urine increased linearly (P < 0.05) with increasing intake of nitrogen and dry matter. Nitrogen retained as either a proportion of nitrogen consumed or nitrogen apparently absorbed was quadratically affected by treatment (P < 0.05) with nitrogen efficiency peaking at intermediate levels of intake.
To further address the concept of restricting intake for dairy heifers on productive efficiency, experiments have recently been conducted to evaluate heifer growth characteristics and nutrient utilization when given rations of high or low energy density for similar levels of ADG. The objective of the first experiment (Zanton and Heinrichs, 2007) was to elucidate the effects of feeding a HC or a HF ration at restricted intakes on feed efficiency and growth characteristics, and the effects on first lactation milk yield. Less DM was consumed by the heifers fed HC than for HF (5.41 HC vs. 5.95 HF kg/d ± 0.11; P < 0.01) at similar ADG leading to significantly improved feed efficiency for the heifers receiving HC (P < 0.01). Daily gains of skeletal measurements were not different between treatments. From these results we conclude that feeding a HC ration leads to similar growth performance when the level of intake is restricted to achieve a controlled ADG.
Reproduction results from this experiment showed that conception rate was not affected by treatment (P > 0.42) and occurred at a time that allowed heifers to calve at an average age of 23.4 mo (P > 0.50). Body weight at puberty (293 HF vs. 287 HC; ± 7 kg) and experimental ADG prior to puberty (0.837 HF vs. 0.837 HC; SE ± 0.009 kg/d) were not different between rations. The same pattern was observed with average BW at calving (BWC) (548 ± 11 kg; P > 0.16). Milk and component production were similar for all groups.
In a concurrent study, Hoffman et al. (2007) investigated the effect of different levels of controlled intake (100, 90 and 80%) from NRC (2001) recommendations on feed efficiency and milk production of gravid Holstein dairy heifers (n = 54). To limit feed the animals, higher density diets containing up to approximately 40% concentrates were provided. This research group also reported no differences in the first 150 d of first lactation milk production and an increased feed efficiency (12.8, 10.4 and 9.9 ± 0.9 kg of body weight gain/ kg DMI respectively; P < 0.09). Due to the restricted DMI and improved efficiency in nutrient utilization, manure output was reduced linearly from 12.9 and 34.6% for the 90 and 80% limit-fed heifers. They concluded that higher density diets fed at restricted intakes to gravid heifers could control caloric intake as efficiently as HF diets fed ad libitum, which would reduce feed costs.
Given the nutritional efficiency observed by feeding HC rations at restricted intakes, a study was conducted to evaluate the effects feeding different forage and concentrate levels on feed and nitrogen efficiency and on nitrogen utilization and ammonia volatilization from the resulting manure. The hypothesis was that energy and nitrogen provided in a HC ration would be utilized with a greater efficiency than when an equivalent amount of energy and nitrogen was given in a high forage ration. A further hypothesis was that greater utilization of nitrogen by the animal would lead to reduced nitrogen excretion and therefore reduced ammonia emissions into the environment. The experiment (Zanton and Heinrichs, 2006b; 2006c) was designed as a split plot design with Young (Y; 313 ± 4 d; 263 ± 6 kg) and Old (O; 666 ± 8 d; 583 ± 6 kg) heifer blocks given HC and HF twice daily to four cannulated heifers per block for four, 28-d periods. Both the HC and the HF rations contained the same feed ingredients, but in differing proportions, yielding two treatment rations containing 75 or 25 percent of the ration dry matter as forages.
Organic matter intake was lower for heifers fed HC (P < 0.01), however due to improved OM digestibility (75.97 HC vs. 71.53 HF ± 0.70%; P < 0.01), intake of digestible OM was not different between treatments (P > 0.20). NDF digestibility was not affected by dietary treatment (52.92 HC vs. 51.18 HF ± 1.46%; P > 0.20). The heifers fed HF had increased total rumen content wet weight (37.84 HC vs. 42.18 HF ± 1.36 kg; P < 0.01). Total VFA concentrations were not altered by dietary treatment (110.80 HC vs. 112.87 HF ± 5.00 mM; P > 0.14). Similar concentrations of total VFA occurred due to higher acetate concentrations, lower butyrate concentrations (both P < 0.01), and a tendency for reduced propionate concentrations (P > 0.07) in HF. Mean rumen pH was lower for HC (6.24 HC vs. 6.51 HF ± 0.10; P < 0.01) and the amount of time that the pH was lower than 6.00 was greater in HC (7.12 HC vs. 3.15 HF ± 1.84 h.; P < 0.01).
Fecal N excretion tended to be greater for HF (P < 0.06) and urinary N excretion was not affected by treatment ration (P > 0.20), leading to greater overall N retention for heifers fed HC (P < 0.01). The efficiency of N retention (0.2740 HC vs. 0.2126 HF ± 0.0128 g N retained/g N consumed; P < 0.01) and the environmental N load (2.92 HC vs. 4.72 HF ± 0.43 g N excreted/g N retained; P < 0.01) were also significantly improved in heifers receiving HC. The ammonia volatilization rate, when adjusted to reflect the greater production of urine and feces by HF, was greater for heifers fed HF (28.74 HC vs. 33.15 HF ± 1.00 g/d; P < 0.01). The conclusion of this experiment was that feeding HC can produce changes in rumen fermentation in Y and O heifers, but the magnitude of these changes can be reduced by restricting intake. This group further concluded that Y and O heifers fed HC will have improved efficiency of OM and N utilization when intake is controlled. Other experiments using corn silage as the sole source of forage have shown similar results (Daubert et al., 2006; Moody et al., 2006).
Continuing with this concept, restricted feeding and HC diets are two potential methods that may be utilized for growing dairy heifers. However, with limit feeding of forages and this high energy forage, rumen fermentation may be challenged. Lascano and Heinrichs (2007) designed experiments to study the effects HC and HF diets at a restricted level of intake. Treatments consisted of HC TMR (40% CS, 60% grain) and HF TMR (80% CS, 20% grain). ADG was similar by design between all treatments for prepubertal heifers. Feed efficiency, defined as the ratio of DMI to gain tended to improve with HC diet (P = 0.08). Ammonia emissions from the barn floor were numerically lower for the HC-fed heifers. These researchers also evaluated the effect of concentrate level on dry matter digestibility (DMD) and N digestibility (ND). Eight Holstein heifers (284.0 ± 3.6 and 405.8 ± 1.5 d of age and 234 ± 15 and 409 ± 20 kg BW) were used with the same diets. No differences were found among heifer ages regarding digestibility. N intake and apparent ND were similar in all treatments. HC diets decreased fecal output of DM (1.49 vs. 1.77 ± 0.06; P < 0.01) and wet feces (10.48 vs. 7.28 ± 0.36 kg; P < 0.01). Urine volume excretion was not different; therefore total manure output was lower for HC diets.
In conclusion, these results indicate that restricted HC diets can be fed to dairy heifers with similar growth performance as LC and improved feed efficiency through increased DM, OM, and NDF digestibility, which at the same time decreases manure output.
Overall, utilizing HC compared to HF rations, fed to maintain optimum levels of daily gain, have shown that whole body growth and skeletal measurements were unaffected, feed costs dropped between 3 and 16%, and manure output fell between 12 and 40% (depending on feedstuffs used). No detrimental effects, either short or long term, were noted from this feeding management system.
The recent studies summarized have shown that feeding high concentrate, low forage rations in a restricted manner to growing dairy heifers from 4 to 22 months of age leads to similar growth performance with respect to weight gains and structural growth. These results also lead to the overall conclusion that provided the level of intake is restricted to allow for an optimal level of ADG, HC rations can be fed to dairy heifers resulting in reduced feed costs and reduced levels of nutrient waste.
Finally, the use of by-product feeds should be evaluated using these higher concentrate, limit-fed situations to possibly reduce manure and ammonia emissions from heifer raising areas. Each situation should be evaluated in terms of these and other nutrients that may be reduced or increased by use of high levels of by-product feeds.
- Bergman, E. N. 1990. Energy contributions of volatile fatty acids from the gastrointestinal tract in various species. Physiol Rev. 70:567-590.
- Daubert, J. M., M. L. Moody, G. I. Zanton, and A. J. Heinrichs. 2006. Nitrogen and dry matter digestibility of high and low forage diets in dairy heifers. J. Dairy Sci. 89(Suppl. 1):160.
- Gabler, M. T., P. R. Tozer, and A. J. Heinrichs. 2000. Development of a cost analysis spreadsheet for calculating the costs to raise a replacement dairy heifer. J. Dairy Sci. 83:1104-1109.
- Heinrichs, A. J. 1993. Raising dairy replacements to meet the needs of the 21st century. J. Dairy Sci. 76:3179-3187.
- Hoffman, P. C. 1997. Optimum body size of Holstein replacement heifers. J. Anim. Sci. 75:836-845.
- Hoffman, P. C., C. R. Simson, and M. Wattiaux. 2007. Limit feeding of gravid Holstein heifers: Effect on growth, manure nutrient excretion, and subsequent early lactation performance. J. Dairy Sci. 90:946-954.
- Lammers, B. P., A. J. Heinrichs, and R. S. Kensinger. 1999. The effects of accelerated growth rates and estrogen implants in prepubertal Holstein heifers on estimates of mammary development and subsequent reproduction and milk production. J. Dairy Sci. 82:1753-1764.
- Lascano, G.J., A.J. Heinrichs. 2007. Digestibility of limit fed high and low concentrate diets with corn silage as the sole forage for dairy heifers with Saccharomyces cerevisiae. J. Dairy Sci.90 (Suppl. 1):187.
- Moody, M. L., G. I. Zanton, and A. J. Heinrichs. 2006. Rumen fermentation patterns of dairy heifers fed restricted amounts of high and low forage diets. J. Dairy Sci. 89(Suppl. 1):366.
- Owens, F. N., P. Dubeski, and C. F. Hanson. 1993. Factors that alter the growth and development of ruminants. J. Anim Sci. 71:3138-3150.
- Radcliff, R. P., M. J. Vandehaar, L. T. Chapin, T. E. Pilbeam, D. K. Beede, E. P. Stainisiewski, and H. A. Tucker. 2000. Effects of diet and injection of bovine somatotropin on prepubertal growth and first-lactation milk yields of Holstein cows. J. Dairy Sci. 83:23-29.
- Radcliff, R. P., M. J. Vandehaar, A. L. Skidmore, L. T. Chapin, B. R. Radke, J. W. Lloyd, E. P. Stanisiewski, and H. A. Tucker. 1997. Effects of diet and bovine somatotropin on heifer growth and mammary development. J. Dairy Sci. 80:1996-2003.
- Reynolds, C. K., H. F. Tyrrell, and P. J. Reynolds. 1991a. Effects of diet forage-to-concentrate ratio and intake on energy-metabolism in growing beef heifers - Net nutrient metabolism by visceral tissues. J. Nutr. 121:1004- 1015.
- Sejrsen, K. and J. Foldager. 1992. Mammary growth and milk production capacity of replacement heifers in relation to diet energy concentration and plasma hormone levels. Acta Agric. Scand., Sect. A. Animal Sci. 42:99-105.
- Sejrsen, K., J. T. Huber, H. A. Tucker, and R. M. Akers. 1982. Influence of nutrition on mammary development in pre- and postpubertal heifers. J. Dairy Sci. 65:793-800.
- Van Amburgh, M. E., D. M. Galton, D. E. Bauman, R. W. Everett, D. G. Fox, L. E. Chase, and H. N. Erb. 1998. Effects of three prepubertal body growth rates on performance of Holstein heifers during first lactation. J. Dairy Sci. 81:527-838.
- Zanton, G. I. and A. J. Heinrichs. 2004. Altering dry matter intake affects the nutritional efficiency of dairy heifer. J. Dairy Sci. 87(Suppl.1):128.
- Zanton, G. I. and A. J. Heinrichs. 2005. The effects of altering dry matter intake on rumen digestion and turnover in dairy heifers. J. Dairy Sci. 88(Suppl. 1):255.
- Zanton, G. I. and A. J. Heinrichs. 2006a. The effects of restricted feeding a high concentrate or high forage ration for similar weight gains on structural growth in Holstein heifers. J. Dairy Sci. 89(Suppl. 1):366-367.
- Zanton, G. I. and A. J. Heinrichs. 2006b. The effects of restricted feeding high concentrate or high forage rations on nutrient digestibility and nitrogen utilization in dairy heifers. J. Dairy Sci. 89(Suppl. 1):439.
- Zanton, G. I. and A. J. Heinrichs. 2006c. The effects of restricted feeding high concentrate or high forage rations on rumen fermentation in dairy heifers. J. Dairy Sci. 89(Suppl. 1):438-439.
- Zanton, G. I., and A. J. Heinrichs. 2005. Meta-analysis to assess effect of prepubertal average daily gain on Holstein heifers on first-lactation production. J. Dairy Sci. 88:3860-3867.
- Zanton, G. I., and A. J. Heinrichs. 2007. The effects of controlled feeding of a high-forage or high-concentrate ration on heifer growth and first- lactation milk production. J. Dairy Sci. 90:3388-3396.
This fact sheet has been developed to support the implementation of the Natural Resources Conservation Service Feed Management 592 Practice Standard. The Feed Management 592 Practice Standard was adopted by NRCS in 2003 as another tool to assist with addressing resource concerns on livestock and poultry operations. Feed management can assist with reducing the import of nutrients to the farm and reduce the excretion of nutrients in manure.
The Natural Resources Conservation Service has adopted a practice standard called Feed Management (592) and is defined as "managing the quantity of available nutrients fed to livestock and poultry for their intended purpose". The national version of the practice standard can be found in a companion fact sheet entitled "An Introduction to Natural Resources Feed Management Practice Standard 592". Please check in your own state for a state-specific version of the standard.
Mark Hill, Akey Co. and Mike Hutjens, University of Illinois
This fact sheet reflects the best available information on the topic as of the publication date, 11-27-2006.
This Feed Management Education Project was funded by the USDA NRCS CIG program. Additional information
This project is affiliated with the Livestock and Poultry Environmental Learning Center.