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Department of Dairy Science, University of Wisconsin, Madison 53706
Corresponding author:
R. R. Grummer; e-mail:
rgrummer{at}wisc.edu.
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONSACKNOWLEDGEMENTSREFERENCES |
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Key Words: dairy cattle • transition • energy density • lactation performance
Abbreviation key: AC = acetate, ADICP = acid detergent insoluble crude protein, DL = low energy density prepartum, DH = high energy density prepartum, EB = energy balance, EE = ether extract, H = high energy density postpartum, L = low energy density postpartum, NDICP = neutral detergent insoluble crude protein, NEB = negative energy balance, NEI = net energy intake, NEM = net energy for maintenance, NEP = net energy for pregnancy, PROP = propionate
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONSACKNOWLEDGEMENTSREFERENCES |
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A series of endocrine changes may be partially responsible for an accelerated decline in feed intake during the last 2 wk before parturition (Ingvartsen and Andersen, 2000). It has been suggested that increasing energy density of the diet by increasing nonfiber carbohydrates during this period has some benefits (Grummer, 1995; Minor et al., 1998; Vandehaar et al., 1999). The additional energy provided to the animal may help offset the negative energy balance before parturition, especially if feed intake is greatly reduced. Feeding additional nonfiber carbohydrate may allow ruminal microorganisms to adapt to the high concentrate diets and promote the development of ruminal papillae. Papillae development takes between 4 to 6 (Dirksen et al., 1985) or 6 to 7 wk (Mayer et al., 1986) to fully develop and may increase the capacity for VFA absorption when additional grain is fed postpartum. On the other hand, feeding high energy density diets during the prepartum is associated with a greater decline of DM and energy intake as parturition approaches (Ingvartsen et al., 1997; Minor et al., 1998; Olsson et al., 1998; Hayirli, 2001). The effects of this on postpartum performance of cows during the subsequent lactation are not well documented in the literature.
Early postpartum, high-producing cows experience a negative energy balance (NEB) because of low energy intake relative to energy required for maintenance and milk production. Because milk yield has been increasing substantially in dairy breeds due to improved nutrition, management, and genetic selection, an exacerbation of NEB is probably occurring during early lactation. A common practice observed on commercial dairy farms is feeding cows an early lactation diet after parturition for about 3 to 4 wk. It usually has less forage than the late prepartum diet, but it is not as high in nonfiber carbohydrate as the diet fed to cows in peak lactation. This is usually done to decrease the risk of rumen acidosis and related diseases (Nocek, 1997). However, feeding a higher nonfiber carbohydrate diet immediately postpartum compared with delaying the increase until 3 wk postpartum may ameliorate the period of NEB during early lactation and improve production responses.
The objective of this study was to compare the effects of different diet energy densities fed during the prepartum and postpartum transition period and potential diet interactions that might occur on periparturient lactation performance and ruminal parameters.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONSACKNOWLEDGEMENTSREFERENCES |
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) for 7 d. Then, one-half of the animals remained on DL and the others were assigned to a high energy diet (DH; Table 1) until the day of calving. After calving, one-half of the cows from each prepartum treatment group were assigned to a low (L) or high (H) energy density diet until d 20 postpartum (Table 1). After d 20 postpartum, all cows were fed H until d 70.
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Cows were milked twice daily, and milk production was recorded at each milking. Milk samples were obtained from four consecutive milkings each wk and analyzed for fat, CP, lactose, and nonfat solids by infrared analysis (AgSource Milk Analysis Laboratory, Menomonie, WI). Cows were weighed weekly during the trial and on d 1 postpartum. Body condition score (BCS) [five-point scale where 1 = thin to 5 = fat; (Wildman et al., 1982)] was recorded on d 29 before expected calving and on d 1 and 70 postpartum.
Rumen samples were obtained by rumenocentesis (Nordlund and Garrett, 1994) 2 wk before expected calving date (-15 ± 4.4 d) and at the third wk of lactation (17 ± 2.0 d). Samples were taken 5 to 6 h after morning feeding. Rumen pH was determined immediately after the samples were collected (Cardy Twin pH-meter Model B-213, Spectrum Technologies Inc., Plainfield, IL). One ml rumen fluid was acidified with 20 µl of 50% H2SO4 and frozen (-20°C) until VFA analysis by GLC (Bal et al., 2000).
Energy Calculations
Net energy intake (NEI) was determined by multiplying the weekly DMI by the calculated energy value of the diet. The energy value of the diet was calculated according to NRC (2001) considering a discount factor based on TDN intake above maintenance. Energy required for body maintenance (NEM) was computed using the equation NEM = BW0.75 x 0.08 (NRC, 2001). Pregnancy requirements (NEP) were computed using the equation NEp = [((2 x 0.00159 x days pregnant - 0.0353) x (calf birth weight / 45)) / 0.14] x 0.64 (NRC 2001). Calf birth weight used was 43 kg. Estimated energy balance (EB) prepartum was computed on a daily basis using the equation EB = NEI - (NEM + NEP). Milk energy was calculated using the equation NEL= MP x [(0.0929 x Fat) + (0.0547 x Prot) + (0.0395 x Lact)], where MP, Fat, Prot and Lact are milk production (kg), and fat, CP, and lactose percentage in milk (NRC 2001). Estimated EB postpartum was computed on a weekly basis using the equation EB = NEI - (NEM + NEL).
Statistical Analyses
One cow was removed from the experiment because it calved twins. Among the remaining 59 animals, 10 were treated for retained fetal membranes, 4 for milk fever, 5 for ketosis, and 3 had surgery because of displaced abomasums. This trial did not provide sufficient replication to determine if incidences of disorders were affected by treatment. However, because that possibility existed, we elected to include the data from cows experiencing disorders. Milk production and energy intake and balance were analyzed as repeated measures using PROC MIXED of SAS (SAS, 1999). For each analyzed variable, cow nested within treatment and parity was subjected to three covariance structures: compound symmetric, autoregressive order one, and unstructured covariance. The covariance structure that yielded the largest Akaike’s information criterion was used. Different statistical models were used for the pre- and postpartum periods. The model for samples taken during the prepartum period and through d 1 postpartum included prepartum treatment effect, block, parity, time (day) and 2- and 3-way interactions as fixed effects (except block). For samples taken after d 1 postpartum, the model included prepartum and postpartum treatment effects, block, parity, time (week or day depending on the variable), and 2- and 3-way interactions as fixed effects (except block). The random effect for both models was cow nested within treatment and parity. Measurements obtained prior to administration of treatments (d -35 to -28 relative to calving) were used as covariates for statistical analyses of corresponding performance parameters (DMI, BW, and BCS). Pretreatment DMI (d -35 to -28 relative to calving) was used as a covariate for statistical analyses of milk yield. Volatile fatty acids and pH were analyzed using PROC MIXED of SAS (SAS, 1999) with block, parity, prepartum or prepartum and postpartum effects, 2- and 3-way interactions, and residual error in the model. For all models, interaction terms with P > 0.30 were removed in a backwards stepwise manner. Least square means and standard error of the means are reported. Statistical significance was declared at P < 0.05 and a tendency towards significance at P = 0.05 to P < 0.15.
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONSACKNOWLEDGEMENTSREFERENCES |
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and 2. Potassium carbonate was added at 0.4% of DM to the DH diet so that both prepartum diets had the same dietary cation-anion difference (DCAD = meq [(0.15Ca + 0.15Mg + Na + K) - (Cl + S + 0.3P)]/100g of dietary DM).
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). Dry matter intake (% BW) was about 15% higher for cows than for heifers in the beginning of the prefresh period, but this difference tended to disappear as calving approached (parity x time interaction, P = 0.07; Figure 1A). The magnitude of depression of DMI between wk -4 and -1 prior to parturition was 0.4 and 0.2% of BW for cows and heifers, respectively.
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). The advantage was greater for cows compared to heifers (14 vs. 24.5%; prepartum treatment x parity interaction, P < 0.09; Table 3 and Figure 1A). Animals fed DH had greater energy intake and energy balance compared to animals fed DL (17.7 vs. 21.5 and 3.9 vs. 8.1 Mcal/d, respectively; P < 0.001; Table 3 and Figure 1B). The prepartum treatment x parity interaction was also significant for energy intake and energy balance (P = 0.008 and 0.02, respectively; Table 3) with the benefit of increased energy density being greater for cows compared to heifers. Body weight in the last week before calving and change in BW during the prefresh period were not affected by prepartum treatments. Body condition score at d 1 and BCS change during the prepartum were higher and lower, respectively, for animals fed DH compared to animals fed DL (Table 3). Calf weights at birth were not affected by prepartum treatments (Table 3).
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). Total ruminal VFA concentration tended to be higher for animals fed DH compared to animals fed DL (P = 0.14). No statistical differences in ruminal fluid concentrations of acetate (AC), propionate (PROP), and AC: PROP ratio were detected.
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Cows and heifers fed DH during the prepartum period tended to have higher DMI, expressed as kg/d or % of BW, than cows fed DL during the first 20 DIM (P = 0.14 and 0.11, respectively; Table 5). However, during the first 20 DIM, no difference was observed for energy intake due to prepartum diets. Prepartum treatment x time interactions were significant for postpartum DMI (kg/d and % BW) and energy intake; differences were during the second wk of lactation and were mainly accounted for by cows fed DL that received L postpartum (Figure 2). Cows fed H postpartum tended to have higher DMI (P = 0.11) than cows fed L during the first 20 DIM. Energy intake during the first 20 DIM was 11% higher for cows fed H compared to cows fed L (P = 0.01). Prepartum and postpartum diets did not affect DMI and energy intake from 1 to 70 DIM, although energy intake tended to be lowest for cows fed the DL-L sequence of treatments (prepartum x postpartum treatment interaction, P = 0.10; Table 5). Cows fed H had higher energy intake compared to cows fed L only during the first three wk of lactation (postpartum treatment x time, P = 0.001; Figure 2). After 3 wk of lactation, when all cows were fed H, no differences in energy intake were observed.
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). An interaction between prepartum treatment and time tended to be significant for milk energy output (P = 0.07). Cows fed DL tended to have higher milk energy output around the fifth week of lactation, and this effect tended to be more evident in primiparous cows than multiparous cows (prepartum treatment x time x parity interaction, P = 0.03). Prepartum treatment did not affect overall energy balance during the first 70 DIM. Cows fed L tended to have a higher energy balance compared to cows fed H during the fourth wk postpartum (postpartum treatment x week, P = 0.10). A similar interaction was observed for gross efficiency (milk energy/intake energy; P = 0.05); cows fed L had lower gross efficiency on wk 4 than cows fed H. This may be a carry over effect of cows switching from L to H.
Body weight at d 70 tended to be lower for heifers fed DH compared to heifers fed DL (534 vs. 571 kg, respectively; P = 0.07; Table 5); no differences were observed for cows (prepartum treatment x parity interaction, P = 0.05). No differences in BW change and BCS were observed due to prepartum or postpartum treatments.
Milk production during the postpartum was not affected by prepartum treatment (Table 6). An interaction between postpartum treatment x time (P = 0.001) indicated that rate of increase in milk production was higher for cows fed H compared to cows fed L (Figure 3). A trend for a postpartum treatment x parity x time interaction for milk production demonstrated that multiparous cows responded more to increasing energy density of postpartum diets than primiparous cows fed on the third wk of lactation (P = 0.09; Figure 3).
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). No differences in 3.5% FCM production due to prepartum treatments were observed for multiparous cows, but primiparous cows fed DL tended to have higher 3.5% FCM production than those fed DH. However, during the second wk of lactation, the opposite was true (prepartum treatment x parity x week interaction, P = 0.02; Figure 4). A similar interaction, (prepartum treatment x parity x time) was observed for milk fat content and production (P = 0.03 and 0.01, respectively). Postpartum treatments did not affect fat or 3.5 % FCM production or milk fat percentage (Table 6). Prepartum diets did not affect milk protein percentage or production during lactation. Cows fed L tended to have a higher milk protein percentage than cows fed H (3.14 vs. 3.06%, respectively, P = 0.10). A trend for a prepartum x postpartum treatment interaction tended to be significant (P = 0.09), with cows fed the DL-L sequence of treatments having the highest protein content. No effects of postpartum and prepartum treatments were observed for milk protein production. Lactose content was lowest for DH-L sequence of treatments (prepartum x postpartum treatment interaction, P = 0.002) and a similar interaction was also observed for SNF content (P = 0.004). Lactose production was not affected by prepartum or postpartum treatments.
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). Cows fed H had lower ruminal pH compared to cows fed L (5.90 vs. 6.14, P = 0.02). Cows fed H also had higher ruminal propionate concentration than cows fed L (37.4 vs. 26.5 µmol/ml, respectively; P = 0.001). Postpartum treatments did not affect ruminal acetate concentration, therefore, AC: PROP ratio decreased for cows fed H compared to cows fed L (2.37 vs. 3.55, respectively, P = 0.001). Ruminal concentration of isobutyrate tended to be lower for cows fed H compared to cows fed L (0.76 vs 0.91 µmol/ml, P = 0.07).
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONSACKNOWLEDGEMENTSREFERENCES |
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Surprisingly, except for changes in ruminal pH and butyrate concentration, dietary energy level fed during the prepartum did not markedly affect rumen fermentation characteristics. Conversely, Rabelo et al., (2001) reported higher ruminal propionate and butyrate concentrations for far-off dry cows fed diets with 40% NFC compared with those fed a diet with 33% NFC. Hernandez-Urdaneta et al. (1976) observed no major differences in VFA profile when cows were fed a 5 or 20% concentrate diet during the last 28 d before calving, but a higher ruminal total concentration of VFA and lower pH was observed for the group fed 20% concentrate. In our study, rumen samples were collected only once a day by rumenocentesis at 5 to 6 h after morning feeding. This sampling intensity may not have been sufficient to demonstrate changes in rumen fermentation pattern due to differences in NFC content of the diets (38 vs. 45% NFC).
Parity Interactions
Heifers had lower DMI (%BW) and less severe depression of DMI as calving approached compared to cows which agrees with findings of others (Marquardt et al., 1977; Hayirli, 2001). The reasons for the greater magnitude of DMI depression in cows compared to heifers are not known, but they might be related to the degree of energy intake above requirements. Because of the lower DMI, average energy intake for heifers during the last 4 wk before parturition was 30% above requirements while for cows it was 58% above requirements. Kunz et al. (1985) observed no drop in DMI for cows that were feed restricted to meet energy requirements (7.3 kg DM/d) during the whole dry period in contrast to cows that were fed forage ad libitum and some concentrate (1.9 kg DM/d). Cows that had DMI restricted to 8.0 kg/d for the last four weeks of gestation had a lower magnitude of DMI depression as parturition approached compared to a group fed ad libitum (12.4 kg/d; Holcomb et al., 2001). It seems that the greater the energy intake above requirements during the prepartum period the greater the magnitude of drop in DMI as parturition approaches.
Postpartum Performance
Increasing prepartum diet energy density had minor effects on overall postpartum performance. The slightly higher DMI during the second week of lactation for cows fed DH did not promote higher energy intake during the same period. Most studies have found that feeding a higher energy diet in the late prepartum period does not alter subsequent performance (Vandehaar et al., 1999; Mashek and Beede, 2000; Holcomb et al., 2001; Keady et al., 2001). However, some studies have demonstrated that restricted feeding during the last weeks of gestation affected performance during the first weeks of lactation (Kunz et al., 1985, Douglas et al., 1998, Holcomb et al., 2001). DMI after parturition increased slightly faster and energy deficiency and weight losses during the first weeks of lactation were less for cows fed reduced amounts of energy before parturition compared to those fed ad libitum (Kunz et al., 1985). Feed restricted cows during the last 4 wk of gestation (8.0 kg/d) demonstrated higher DMI and milk yield in early lactation compared to cows fed ad libitum (12.4 kg/d; Holcomb et al., 2001). In our study, heifers fed DL were the only group during the prepartum that had energy intakes close to requirements. Feeding DL during the prepartum increased FCM yield only for primiparous cows, supporting other studies that showed that cows feed restricted to their energy requirements during the prepartum period have better performance during early lactation (Kunz et al., 1985; Douglas et al., 1998; Holcomb et al., 2001).
Increasing dietary energy concentration immediately after calving instead of delaying 3 wk positively affected performance and energy status of dairy cows during early lactation. Cows fed H had higher DMI and energy intake during the first 3 wk of lactation than cows fed L. As a result of the higher energy intake, the rate of milk production increase was greater for cows fed H compared to cows fed L.
Increased DMI during the first weeks of lactation due to feeding H suggests that DMI during this period is limited by rumen fill. Hernandez-Urdaneta et al. (1976) observed higher DMI intake during the first 4 wk of lactation for cows consuming a diet with a 60:40 concentrate:forage ratio compared to cows fed 40:60 concentrate:forage ratio. Recently, Ingvartsen et al. (2001) compared three feeding strategies during early lactation: feeding forage ad libitum and increasing concentrate 0.3 or 0.5 kg/d up to a total of 10.2 kg/d, or feeding a complete diet. They observed higher milk yield and DMI during the first 4 wk of lactation for cows fed a complete diet compared to cows fed concentrate and forages separately. They attributed these responses to the higher level of concentrate fed to the group given the complete diet.
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CONCLUSIONS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONSACKNOWLEDGEMENTSREFERENCES |
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ACKNOWLEDGEMENTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONSACKNOWLEDGEMENTSREFERENCES |
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Received for publication June 4, 2002. Accepted for publication September 12, 2002.
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REFERENCES |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONSACKNOWLEDGEMENTSREFERENCES |
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– –), cows fed high energy density diet prepartum (– –
– –) and cows fed low energy density diet prepartum (—
—); animals fed low energy density diet prepartum and high energy density diet postpartum DL-H (—
—) and animals fed high energy density diet prepartum and high energy density diet postpartum, DH-H (—
