Dietary energy density for the close-up dry cow – Postpartum

The transition period for dairy cows is generally defined as three weeks prior to parturition through three weeks after parturition. Defining and meeting the transition dairy cow ‘s nutritional requirements can greatly impact animal health, subsequent lactation production, overall longevity, and animal well-being (NRC, 2001). Dry cow nutrition and management have been active research areas over the last two decades. This effort has resulted in better biological understanding and insight into how to feed cows during the close-up dry period. However, the lack of repeatable success with close-up dry period nutrition programs has been a concern to nutritionists and producers. Many nutritional strategies have come and gone. This paper will summarize current research in feeding dry cows, providing some recommendations based on research and field experiences.

Economic Impact

Feed cost is typically 50-70% of the cost of milk production, while costs associated with a single health problem are often never fully recovered. Because the transition period has the most impact on health, production and reproduction, the greatest marginal return for investments to improve dairy cow profitability will occur during this time.

The transition to lactation underscores the importance of gluconeogenesis in ruminants as hypoglycemia, ketosis, and related metabolic disorders occur when gluconeogenic capacity fails to adapt to the increased glucose demand to support lactose synthesis and mammary metabolism. Ketosis is accompanied by fatty liver; cows that develop fatty liver and ketosis have reduced feed intake, lower gluconeogenic capacity (Grummer, 1995), lower milk production, and an increased risk for developing other metabolic and infectious diseases (Curtis et al., 1985).

A case of ketosis is estimated to US$140/cow in treatment costs. Given a ketosis incidence rate of 17% in US cattle (Gillund et al, 2001), a producer milking 120 cows would lose $2,520 annually to clinical ketosis. Additionally, subclinical ketosis cases add approximately $78/case (Geishauser et al, 2000) with additional losses due to lost milk production potential.

Factors impacting nutrient needs of the transition cow

Does ruminal capacity affect prepartum intake depression?

The fermentative capacity of the rumen is incompletely characterized through the dry period to lactation making it difficult to predict the nutritive value of feeds for transition dairy cows. During late gestation cows are thought to reduce dry matter intake due to constraints in rumen fill and digestion. This reduced intake results in mobilization of body fat and energy stores to meet tissue energy demands, often leading to fatty liver and other problems. Increasing the supply of glucogenic precursors, such as propionate, minimizes the negative impact of reduced feed intake during the transition period (Dann et al, 1999). Likewise increasing the energy density of diets for late-gestation dairy cows reduces fatty liver and improves lactation performance (Minor et al., 1998). However, diet modifications that increase energy density via rapidly fermentable carbohydrates, such as starch, may increase the incidence of displaced abomasums, acidosis (Penner et al, 2007), and result in over conditioned cows.

It has become very clear that the role of physical constraints has been overemphasized in ruminants (Hartnell and Satter, 1979; Park et al., 2001). Instead, metabolic and endocrine changes in late pregnancy and early lactation play an important role in prepartum intake reduction (Ingvartsen et al., 1999). Prepartum intake reduction is not unique to ruminant animals, having also been observed in rats (Peterson and Baumguardt, 1976). Low intake may play an important role in early host defense mechanisms (Murray and Murray, 1979); during infection, cytokines that can severely reduce intake are released. Additionally, feedback signals from oxidation of nonesterified fatty acids (NEFA) are speculated to reduce intake in late pregnancy and early lactation when fat mobilization is high (Ingvartsen and Andersen, 2000). Blood NEFA elevations in cows occur at the same time as feed intake is reduced with similar effects both prepartum and postpartum (Vallimont et. al., 2001).

Prepartum DMI effects on postpartum DMI: is it important?

There is some evidence that the shape of the prepartum DMI curve (i.e., the rate and extent of decrease of DMI prior to calving) may better predict overall transition health and performance. Critical metabolic indices (i.e., postpartum plasma NEFA concentrations and liver triglyceride accumulation) were most strongly correlated with the change in DMI from 21 day to 1 day prepartum; as the change in DMI decreased, postpartum plasma NEFA and liver triglycerides also decreased (Mashek and Grummer, 2003).

The effect of magnitude of prepartum DMI decrease has been studied to determine whether dry cow energy intake restrictions can prepare cows for the negative energy balances occurring in early lactation. Cows fed balanced prepartum diets restricted to below calculated energy requirements (usually about 80% of predicted requirements) did not decrease DMI during the days preceding parturition. These animals increased postpartum DMI and milk yield at faster rates than cows consuming the same diets for ad libitum intake prepartum (Douglas et al., 1998; Holcomb et al., 2001; Agenas et al., 2003). Feed-restricted cows seemed to have greater insulin sensitivity (Holtenius et al., 2003) and reduced peripartal NEFA curves compared with those fed for ad libitum prepartum intake (Douglas et al., 1998; Holcomb et al., 2001; Holtenius et al., 2003).

Several studies conducted at Penn State University evaluated restricted intake diets (1.5% of body weight, DMI of 19 lb/d) for 4 weeks prior to calving versus free-choice feeding where DMI was as high as 2.7% of body weight (DMI of 35 lb/d). Provided that rations were properly balanced and managed, DMI postpartum and animal health was not compromised. These studies all utilized individually housed and fed cows. Achieving uniform restricted intake in the typical group-fed, commercial situation where social interactions and competition will predominate will be difficult.

How long does it take for animals to adapt to dietary changes?

Approximately 5 weeks are required to change the physiological set point of ruminant animals in response to alterations in nutritional status (Koong et al, 1982). Rumen, intestines, and liver size differ significantly from 3 weeks prepartum compared with 3 weeks postpartum (Reynolds et al., 2000) and blood flow through the portal drained viscera increases with increasing energy intake (Huntington, 1990). Therefore, establishing a new metabolic plateau for liver and intestinal tissues to meet demands for milk production after parturition by altering diet may require significant adaptation time (Finnegan et al., 2001; Huntington et al., 1988; Koong and Ferrell, 1990).

Other prepartum physiological challenges are not adequately described to fine-tune nutritional programs during the transition period. These include the 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, and describing requirements for glucogenic precursors and the additional nutrients needed to meet the demands for mammary gland growth.

Feeding strategies and management of dry cows

Nutritional strategies

The primary nutritional goal during the transition period should be to support the dam, fetus, uterine, and mammary tissues. Recommendations for feeding a lower energy diet during the early dry period were developed to minimize risk of overly fat cows at parturition (Dairy NRC 2001) and potential detrimental carryover effects of overconditioned cows (Dann et al., 2006). Available data support feeding a higher energy diet for two to three weeks prior to parturition (Contreras et al., 2004; Corbett, 2002; Mashek and Beede, 2001). Further, (Contreras et al., 2004) managing cows to achieve a body condition score of approximately 3.0 at dry off rather than the traditional 3.5 to 3.75 body condition score seems to be beneficial.

Evaluation of dietary strategies

Increasing energy content of the close-up diet by varying the nonfiber carbohydrate (NFC) content of the diet was been widely studied. Feeding diets containing higher proportions of NFC should promote ruminal microbial adaptation to NFC levels typical of lactation diets and provide increased amounts of propionate to support hepatic gluconeogenesis and microbial protein production (providing the diet contains sufficient ruminally degradable protein) to support protein requirements for maintenance, pregnancy, and mammogenesis.

A large body of research concerning manipulation of dietary energy through NFC content exists (Dewhurst et al., 2000;. Holcomb et al., 2001; Keady et al., 2001; Mashek and Beede, 2001; and VandeHaar et al., 1999). Despite a wide range of NFC concentrations, feeding a high NFC diet virtually always resulted in higher prepartum DMI and frequently resulted in one or more positive effects on energy metabolism or production when compared with lower NFC diets. Replacing forages in dairy rations with nonforage fiber sources (NFFS; i.e., beet pulp, citrus pulp, soybean hulls, cottonseed, wheat midds, etc.) has also been evaluated. In one example, Pickett et al. (2003) replaced forage in a conventional dry cow diet with NFFS; cows fed the diet containing NFFS had increased prepartum DMI and decreased prepartum NEFA concentrations in plasma.

While available data do not clearly support a single strategy for carbohydrate nutrition of transition cows during the prepartum period, most studies report one or more positive outcomes when higher NFC diets are fed relative to lower NFC control diets (Hayirli et al., 2002). The only guideline provided by the Dairy NRC (2001) for carbohydrate nutrition of dry cows was that NFC content of the close-up diet should not exceed 43% of dietary DM. This recommendation is consistent with data indicating close-up period diets containing high concentrations of NFC (43 to 45%) appeared to accentuate decreases in DMI occurring in the days preceding parturition (Minor et al., 1998; Rabelo et al., 2003). Overall, the data summarized above support feeding diets during the close-up period that contain moderately high concentrations (34 to 36%) of starch-based NFC sources.

Application of low energy diets

Simple replacement of forage with straw to provide a more bulky diet decreased insulin concentrations (Rabelo et al., 2003) and may not allow microbial adaptation to a higher energy diet during the prepartum period. However, successful responses to transition diets containing chopped straw (i.e., 8 to 10 lbs of DM) are common in commercial dairies with consistently observed reductions in postpartum displaced abomasum cases. Dietary bulkiness should ensure high rumen fill, thereby decreasing the risk of displaced abomasum and potentially limiting energy intake. Straw persists in the rumen of these cows during transition into lactation, likely for a week. During this time when DMI might be lower there appears to be less opportunity for these cows to displace.

Disadvantages of this type of diet are the increased risk for sorting by cows and the relatively higher level of feeding management required to ensure consistent intake of a high-bulk diet. It is not known whether the shape of the prepartum DMI curve is flatter when cows are fed a high-bulk diet, as in a restricted-feeding scenario. No controlled comparisons of high-bulk diets with currently recommended, well-managed higher NFC diets have been published.

Plane of nutrition during the far-off dry period plays a significant role in periparturient metabolism, regardless of the close-up ration (Dann et al., 2006).
Overfeeding during the far-off period combined with underfeeding during the close-up period negatively affected prepartum energy metabolism. Carryover effects of the far-off period feeding diminished as lactation progressed. These findings may be applicable to situations where DMI in close-up groups is decreased by overcrowding or other management limitations.

It would appear that overfeeding during the early dry period may play a greater role in development of postpartum health disorders than markedly different close-up nutrition programs.

How low-energy dry cow diets might work

Decreasing dietary energy density in the far-off dry period to near NRC recommendations (about 0.57 Mcal NEL per pound of DM) may help decrease health problems in several ways. First, the addition of indigestible or slowly digestible fiber sources (straw, cottonseed hulls, or corn stalks) maintains rumen health, fill, and function, and may help to prevent displaced abomasum around calving.

Prolonged intakes of energy in excess of requirement seems to increase insulin resistance and other changes similar to those in obesity and Type II diabetes in humans and other animals. Cows allowed free access to moderate energy diets, had higher insulin concentrations but similar glucose concentrations compared with limit fed animals (Dann et al., 2006), indicating insulin resistance. Others have provided more direct evidence of insulin resistance caused by prolonged over consumption of energy (Holtenius et al., 2003). By lowering energy intake in the dry period, post-calving appetite may be improved, mobilization of body fat stores may be decreased, and fat accumulation in the liver may be decreased (Drackley, 1999; Drackley et al., 2001).

Dry cows can easily meet their energy needs (about 14 Mcal of NEL per day for a typical Holstein cow) when fed a palatable low-energy diet; for example, cows would need to consume only 23.7 lb DM per day of a diet containing 0.59 Mcal/lb DM to meet energy requirements. Ingredients that decrease dry period dietary energy density also tend to be lower in potassium content. By lowering dietary potassium, problems with periparturient hypocalcemia may be reduced. In all of these studies, the outcome for the prepartum diet is largely due to effects on metabolic disease than production per se. However, proving differences in disease incidence is difficult unless hundreds of animals are evaluated.

Effect of body condition

Heavier cows decrease DMI prior to calving more than thin cows. If cows are fat at dry off, restricting prepartum period intake might prevent accumulation of more body condition. However there may be increased risk for metabolic disorders after calving such as ketosis, displaced abomasum, and fatty liver. It is clear that over conditioned cows (>4.0 on a 5.0 scale) have reduced intakes after calving and are more prone to fatty liver disease and ketosis (Fronk et al, 1980). Overconditioned cows are more likely to have elevated NEFA and or ketone concentrations which may be accompanied by higher incidence of ketosis and lower milk production (Michelone et al., 1999; Putnam et al., 1997: Putnam et al., 1999; Waltner et al., 1993).The result is heavier cows that 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% of late lactation cows are over-conditioned (BCS > 3.5), a change is warranted. Some options include feeding a low group TMR, restrict intake of a one group TMR to the tail- enders, include NFFS in place of high energy dense feeds, or feed a lower quality forage.

Challenges to current dry cow feeding and management concepts

A number of facts must be considered in developing a transition period nutritional program. Dry cows do not need nutrient dense rations: however, during the last 6-8 weeks of gestation the fetus is growing at its most rapid rate and has a tremendous demand for glucogenic precursors.The cow is also manufacturing immunoglobulins necessary forthe calf at birth. It has been demonstrated that poor nutrition impacts the composition and quantity of immunoglobulins synthesized. The mammary gland also requires nutrients in preparation for lactogenesis.

Dry cows have reduced nutrient demands and can be fed cheaper feed sources and/or lower 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 undesirable during this time period.

Dry cows require less oversight and labor and may move to another facility. However, this time period 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. Dry cows are more sensitive to overcrowding; an 11% decrease in DMI was observed when numbers went from 88 to 93% of capacity in a headlock pen (Buelow ,1998).

If a steam-up ration containing lactating cow TMR is used, differences in mineral requirements between pre- and postpartum animals must be accounted and adjusted for. In addition, 2 to 3 weeks is inadequate for liver and intestinal enzymes to adjust to the ration change.

Is an early and close up ration necessary for dry cows? Can a one group total mixed ration (TMR) be fed during the dry period?

Many producers are successfully feeding a one group TMR during the entire dry period. Cows eating rations with a portion of the fiber coming from NFFS had higher DMI prepartum in comparison to conventionally-fed dry cows (Ordway et al., 2002). Increased milk production and reduced metabolic problems have also been demonstrated (Ordway et al., 2001).The cost of feeding one ration throughout the entire dry period is easily offset by the costs of treatment and lost production for one case of ketosis.

In any dry cow feeding program ration changes should not be drastic. The fresh cow ration should be intermediate between the close up ration and the fresh group ration. No more than a 10% increase in any nutrient should occur when transitioning cows to the lactating cow ration (Chandler, 1995). For example, if the prepartum close-up ration is 0.70 NEl Mcal/lb then the immediate fresh ration should be no greater than 0.77 NEl Mcal /lb DM.

Dry cow ration recommendations follow; energy 0.68-0.72 Mcal NEl/lb DM, 13-14% CP in, metabolizable protein 1100-1200 grams, NFC 33-38%, and NDF >32%. Successful transitions from dry to lactating are critical to profitability of the cow. Stimulation and maintenance of DMI around calving is essential for high productivity and healthy cows. Proper formulation of rations for protein, energy density, fiber, and nonfiber carbohydrates will help to increase intake around calving. This, 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.

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Author

Gabriella A. Varga

Gabriella A. Varga
1 articles

Gabriella A. Varga is a Professor in the Department of Dairy and Animal Science at Penn State University and has been a member of the faculty since 1985. Gabriella has a research, teaching and extension appointment in the department.

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Penn State University

Penn State University

Penn State is a multicampus public research university that educates students from Pennsylvania, the nation and the world, and improves the well being and health of individuals and communities through integrated programs of teaching, research, and service.

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