It is now recognized that defining and meeting the nutritional requirements of the dry cow can greatly impact animal health, production in the ensuing lactation, overall longevity and animal well-being. Nutrition and management during the dry period are essential in determining the profitability of the cow for the rest of her lactation.
An inadequate transition program may result in cows having inconsistent feed intakes after calving and metabolic diseases during the transition from dry period to early lactation.
Inadequate nutrients provided to the dry cow can result in increased costs for veterinary treatment and loss of production potential. Problems during the transition period often result in the loss of 10 to 20 pounds of peak milk, which translates into economic losses up to $600 for that lactation. To maximize productivity and ensure successful reproduction, rations fed during this time need to be nutrient-dense and allow for proper transitioning of the diet to the lactating cow ration.
Maximizing prepartum and postpartum dry matter intake is an important key to successful transition cow management. There are many excellent reviews detailing the physiological changes associated with the transition period. This [article] will examine various feeding management strategies that can impact the nutrient needs, overall management and health of the transition cow. It will focus on the practical aspects of nutritional management strategies for the cow during this very critical period of the lactation cycle.
Feed-related costs typically comprise 50 to 70 percent of the costs of production on a dairy farm, while the costs associated with a single health problem often are never fully recovered. Because the transition period has the most impact on health, production and reproduction, the greatest marginal return for an investment that improves dairy cow profitability will occur for changes made during this time. The transition to lactation underscores the importance of gluconeogenesis in ruminants as hypoglycemia, ketosis and related metabolic disorders are often observed when gluconeogenic capacity fails to adapt to the increased demands for glucose to support lactose synthesis and mammary metabolism.
Ketosis is accompanied by fatty liver, and cows that develop fatty liver and ketosis have reduced feed intake, lower gluconeogenic capacity, lower milk production and an increased risk for developing other metabolic and infectious diseases. It has been estimated that an incident of ketosis costs the dairy producer $140 per cow in treatment costs. Given a ketosis incidence rate of 17 percent in U.S. cattle, a producer milking 120 cows would lose $2,520 annually to clinical ketosis.
Subclinical ketosis costs approximately $78 per case. Additional losses are realized through lost milk production potential. Reducing subclinical ketosis and fatty liver, such that cows produce a minimum of 0.5 kilogram more milk at peak lactation, would result in an additional $2,880 of income.
In addition, ketosis increases the risks of developing other metabolic diseases such as displaced abomasum ($334 per case), retained placenta ($319 per case), mastitis ($200 per case) and other metabolic problems. Clearly, feeding management strategies that reduce clinical and subclinical ketosis will directly benefit dairy farm profitability, enhance animal well-being and improve cow longevity.
Does ruminal capacity affect prepartum intake depression?
The fermentative capacity of the rumen has not been adequately characterized through the dry period to lactation. Understanding the dynamics of rumen digestion is critical to developing a mechanistic approach to predicting the nutritive value of feeds for transition dairy cows. During late gestation it has been thought that cows reduce dry matter intake as a consequence of constraints in rumen fill and digestion. This reduction in intake results in the mobilization of body fat and energy stores to meet tissue energy demands.
The combination of these factors often leads to fatty liver and other problems. Increasing the supply of glucogenic precursors, such as propionate, act to minimize the negative impact of reduced feed intake during this period. Likewise, increasing the energy density of diets for late-gestation dairy cows reduces fatty liver and improved lactation performance. However, diet modifications that increase energy density through inclusion of rapidly fermentable carbohydrates, such as starch, may increase the incidence of displaced abomasums, acidosis and result in over-conditioned cows.
Hartnell and Satter demonstrated that there were no differences in ruminal fill, digesta capacity or ruminal retention time in prepartum versus postpartum dairy cows. Park et al. demonstrated by measuring ruminal water-holding capacity at various times, prepartum and postpartum, that physical capacity of the rumen during this time period does not contribute to prepartum intake depression. It becomes very clear as more information of this nature becomes available that to some extent the role of physical constraints has been overemphasized in ruminants, and that metabolic and endocrine changes in late pregnancy and early lactation play an important role in prepartum intake reduction.
Actually, this intake reduction prepartum is not unique to ruminant animals. This also occurs in rats offered a nutritious diet, even though food consumption was substantially less than what would be expected based on their physical capacity. Some researchers have actually demonstrated that hypophagia may play an important role in early host defense mechanisms. It is known that during infections cytokines are released that may severely reduce intake.
Additionally, feedback signals from the oxidation of nonesterified fatty acids (NEFA) are speculated to down regular intake in late pregnancy and early lactation when mobilization is high. We have shown that cows have higher NEFA in blood at the same time as feed intake is reduced and the effect is similar whether this occurs prepartum or postpartum. Before trying to improve feed management, it might be important to get a better understanding of intake regulation in the periparturient animal.
How much do dry cows eat?
When provided a diet containing 65 to 70 percent forage on a dry matter basis, dry cows will consume on average 13.6 kilograms of total dry matter during the four weeks prior to calving. A cow weighing 614 kilograms would consume 2.2 percent of her bodyweight. Several studies conducted at Penn State University have examined the performance of cows fed restricted intake diets at 1.5 percent of bodyweight (DMI of 9.1 kilograms per day) four weeks prior to calving versus free-choice feeding where DMI was as high as 2.7 percent of bodyweight (DMI of 16 kilograms per day). The take-home message from these experiments was as long as the rations were properly balanced and managed, DMI postpartum and animal health was not compromised.
Dry matter intake of dairy cows can be limited by physical fill in early lactation. Providing highly fermentable non-forage fiber sources (NFFS) may increase rate of passage through the rumen and thereby provide the cow the opportunity to consume more feed. A study by Ordway demonstrated that feeding a diet containing NFFS resulted in prepartum DMI that was 20 percent greater than previous studies conducted and was 2 to 5 kilograms per day greater than many values reported in the literature.
Additional work indicates that byproduct feeds, particularly soyhulls and cottonseed hulls, can be substituted for forage fiber without negative consequences on rumination activity. Because prepartum intake is correlated with postpartum intake and milk production is directly related to feed intake, it is critical to devise feeding strategies for transition dairy cows that help to avoid, or minimize, the natural tendency for feed intake depression just prior to calving. Doing so assures that the cow will begin lactation with minimal risk of developing health disorders and will maximize milk production.
A strategy to reduce fiber in the diet of late-gestation dry cows, derived from poor quality silages and long-stemmed hay in favor of highly fermentable byproduct feeds, appears logical. These rations are likely to be more uniform in chemical composition, more predictable in their fermentation characteristics, more readily consumed by transition dairy cattle and more universally applicable.
How long does it take for animals to adapt to dietary changes?
Approximately five weeks are required to change the physiological set point of ruminant animals in response to alterations in nutritional status. Rumen, intestines and liver size differ significantly less than three weeks prepartum compared with three weeks postpartum and blood flow through the portal drained viscera is positively correlated with energy intake.
Koong and Ferrell demonstrated that fasting heat production could differ up to 40 percent for animals of the same age and weight but with different nutritional backgrounds. Huntington et al. demonstrated the oxygen consumption by the portal drained viscera, as a percentage of whole animal oxygen consumption was 4 percent greater for orchardgrass silage compared to alfalfa silage. Finnegan et al. demonstrated a role for the gastrointestinal tract contributing to higher thermogenesis observed in ruminants fed forage as opposed to concentrate diets.
Taken together, these data suggest a minimum of five weeks of feeding may be required to establish a new metabolic plateau for liver and intestinal tissues in response to diet. Therefore, the duration of feeding a nutrient-dense diet may dictate the adaptive response in gut and liver and their capacity to meet the demands for milk production in the ensuing lactation.
There are many physiological challenges prepartum where we clearly lack adequate information to help guide us in nutritional strategies for feeding cows during the transition period. These include the importance of acclimation of microbial populations to the lactating cow diet, maintaining microbial protein synthesis, assuring maximal absorptive capacity of the ruminal epithelium, liver and gut function set points, quantity of adequate glucogenic precursors and the additional nutrients needed to meet the demands for protein and energy for growth of the mammary gland.
Feeding strategies and management of dry cows: Evaluation of diets and level of feeding
Mashek and Beede reported no effect of duration; cows were on a close-up dry cow diet on milk production. In a trial feeding a 60-to-40 (DM basis) of grass silage with barley straw ad libitum, grass silage ad libitum or 0.5 kilograms per day of prairie meal with grass silage ad libitum for six weeks prior to parturition, no effect of diet on milk yield was observed. Holcomb et al. fed diets high (70 percent) or low (28 percent) in forage either restricted or ad libitum for four weeks prior to parturition and reported no significant effects of forage percentage during the prepartum period on milk yield.
VandeHaar et al. fed diets varying in both protein and energy for 25 days prior to parturition and again reported no effect of diet composition on milk or component yield during lactation. Keady et al. supplemented grass silage-based diets with 0 or 5 kilograms per day of concentrates for four weeks prior to calving and found no effect of treatment on milk and milk protein yield, while milk fat increased significantly with concentrate feeding. Holcomb et al. reported no advantage of high DMI prepartum versus restricted diets on milk production.
These studies provide little evidence that close-up dry cow diets will promote increased production after calving. In addition, many of these dietary changes were made three to four weeks prepartum – likely inadequate time for the animal to adjust to a new physiological set point. However, the importance of the amount of DMI consumed prepartum is more critical to the prevention of metabolic diseases such as ketosis postpartum than increased milk production.
Effect of body condition
The outcome of prepartum diet is more likely its effects on metabolic disease which is much more difficult to measure unless hundreds of animals are evaluated. Heavier cows experience a greater decrease in DMI prior to calving than do cows of thin body condition. In situations where cows are fat at dry-off, restricting intakes during the prepartum period would be beneficial to avoid accumulating more body condition. However, there may be increased risk for metabolic disorders after calving such as ketosis, displaced abomasums and fatty liver. It is clear that overconditioned cows (4.0 on a 5.0 scale) have reduced intake after calving and are more prone to fatty liver disease and ketosis. In a well-managed high-producing herd, Waltner et al. found that FCM in the first 90 days of lactation was maximized when body condition score was 3.5 at calving. Putnam et al. demonstrated that cows with body condition score (BCS) greater than 3.25 prepartum had higher NEFA, and b-hydroxybutyrate (BHBA) concentrations and produced 2.5 kilograms per day less milk the first 30 days of lactation than cows with BCS less than 3.25.
The bottom line is that heavier cows lose more body condition after calving and have more difficulty getting bred back. It is recommended to begin feeding-management decisions for fat cows approximately 60 to 45 days prior to dry-off. If more than 10 percent of late-lactation cows are overconditioned (BCS greater than 3.5), a change is warranted. Some options to reduce BCS include feeding a low group total mixed ration (TMR) 60 days prior to dry-off, restrict intake of one group’s TMR to the tail-enders, include NFFS in place of high energy- dense feeds or feed a lower quality forage than currently fed.
Challenges to current dry cow feeding and management concepts
Practical decisions made regarding feeding cows during the dry period are simple.
1. The cow is not lactating; therefore, she does not need a nutrient-dense ration as when she is lactating.
However, during the last six to eight weeks prior to calving the fetus is growing at its most rapid rate and has a tremendous demand for glucogenic precursors. It is also the time period that the cow is manufacturing immunoglobulins necessary for the calf at birth. It has been demonstrated that poor nutrition impacts the composition and quantity of immunoglobulins synthesized. The mammary gland (as discussed previously) also requires nutrients in preparation for lactogenesis.
2. Since the cow has reduced nutrient demands, she can be fed cheaper feed sources or poor quality forage.
It has not been demonstrated that all physiological aspects of the cow’s nutrient demands are reduced during this time period. The cow is most immunocompromised at this time and exposure to mycotoxins and inconsistent nutrients (as found in poor quality forages) is least desired during this time period.
3. The dry cow can be brought to another facility, needs less oversight and therefore less labor.
This is the time period when observation is critical, especially regarding the body condition of the animal and her appetite. Physical facilities and cow comfort during this time period is also critical. Buelow demonstrated that dry cows are more sensitive to overcrowding with an 11 percent decrease in DMI when numbers went from 88 to 93 percent of capacity in a pen with headlocks.
4. Use of a steam-up ration two to three weeks prior to calving.
Many times the lactating cow ration is used without attention to differences in mineral requirements between pre and postpartum animals. In addition, as discussed previously, two to three weeks is not adequate time for liver and intestinal enzymes to adjust to the prepartum and postpartum rations.
Can a one-group TMR be fed during the dry period?
Many producers are successfully feeding a one-group TMR during the entire dry period. In a completed study, we demonstrated that cows provided with corn silage-based rations and a portion of the fiber coming from NFFS had higher DMI prepartum in comparison to conventionally fed dry cows. These diets were based on corn silage as the primary forage source (50 percent of ration DM), approximately 20 percent of the ration DM coming from NFFS such as CSH, soyhulls and corn cobs, with the remainder from soybean meal, molasses, corn, distillers, vitamins and minerals.
Cows consumed on average 3 kilograms more DMI compared to the last six prepartum studies we have conducted feeding conventional dry cow rations (70 percent of DM from forage) during the last four weeks prepartum. Cows that were provided the experimental ration the entire dry period did not gain any additional body condition compared to cows fed a conventional high forage ration. In addition, cows averaged 18 kilograms of DMI the first two weeks of lactation with minimal health problems and peaked with an average of 46 kilograms of milk at five weeks postpartum.
We also conducted a pen feeding study with 36 animals, half of which were heifers, evaluating a conventional dry cow ration with one formulated to contain 35 percent NFFS fed the entire dry period. All cows averaged 48 kilograms of milk the first seven weeks of lactation; however, mature cows produced 3 kilograms more milk when provided the NFFS-based ration prepartum and had a lower incidence of metabolic problems. It is important to understand that the NFFS replaces the forage portion of the ration and not the energy and protein sources. The cost associated with feeding one ration throughout the entire dry period is easily offset when considering the costs associated with the treatment and lost production for one case of ketosis.
Finally, in a trial with 50 cows per treatment we demonstrated that cows consumed an average of 3 kilograms more DM the last four weeks prior to calving, had lower blood NEFA concentrations and numerical trends for increased milk production were observed when cows were provided a NFFS-based diet versus a traditional dry cow ration. Rations were formulated to be similar in chemical composition and fed the entire dry period.
Advantages of a one-group TMR for dry cows include:
1. reduced labor, ease of feeding, fewer rations to mix
2. consistency of diet provided to cows
3. less dramatic change when switched to lactating cow ration
4. more nutrient-dense to meet needs of fetus, mammary gland and reduced intake few days prior to calving
5. can contain many of the same ingredients as in the lactating cow ration
6. if more than one lactating feeding group, this ration can be similar to ration for tail-enders
7. cows are more prepared to meet demands of lactation and potentially have greater body reserves and therefore lose less body condition
8. cows do not have to be moved from various facilities or pens other than to a maternity pen
9. cows have to be monitored more regularly for aggressiveness at the feedbunk
10. cows that calve early are on a nutrient-dense diet for a longer period of time and therefore are assured an adequate adaptation to a lactation- type ration
Advantages of an early and close dry cow feeding program include:
1. cheaper sources of feed fed to the far-off group
2. far-off cows housed in a different facility
3. expensive feed additives provided for a shorter period of time
4. feed intake of far-off group not have to be as closely monitored
5. forage quality and availability may necessitate a two-group feeding program
In any dry cow feeding program it is critical that ration changes are not drastic. The fresh cow ration should be intermediate between the close-up ration and the fresh group ration. A shift should not be greater than a 10 percent increase in any nutrient when transitioning cows prepartum to the lactating cow ration.
Nutrition and management during the transition period are essential in determining the profitability of the cow for the rest of her lactation. Stimulation and maintenance of DMI around calving is essential to ensure a high level of productivity and healthy cows. Proper formulation of rations for protein, energy density, fiber and nonfiber carbohydrates will help to increase intake around calving along with management of body condition, cow comfort and consistent and high-quality forages will assure an excellent transition program for the high-producing dairy cow. PD
References omitted but are available upon request at email@example.com
—From 2nd Mid-Atlantic Nutrition Conference Proceedings