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,2
* Dept. of Animal Sciences, University of Illinois, Urbana 61801
Puyallup Research and Extension Center, Washington State University, Puyallup, 98371
Department of Animal and Nutritional Sciences, University of New Hampshire, Durham 03824
2 Corresponding author: peter.erickson{at}unh.edu
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONSACKNOWLEDGEMENTSREFERENCES |
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Key Words: milk replacer • lactoferrin • calf
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONSACKNOWLEDGEMENTSREFERENCES |
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Due to increasing pressure to reduce subtherapeutic use of antibiotics in animal agriculture, there is a need to investigate possible alternatives. Lactoferrin (LF) is a 78-kDa iron-binding protein that exhibits broad-spectrum antimicrobial effects. Lactoferrin is found in colostrum, milk, and tears (Kijlstra et al., 1983), cere-brospinal fluid (Talukder et al., 2003), and most other body secretions. Lactoferrin concentrations are highest in bovine colostrum (2 mg/mL; Masson and Heremans, 1971). It is an effective antimicrobial agent against a wide range of infectious agents, such as Escherichia coli (Reiter and Perraudin, 1998), Salmonella spp., and Staphylococcus spp. (Weinberg, 2001).
Joslin et al. (2002) observed that calves fed either 1 or 10 g/d of LF had higher BW, increased ADG, tended to consume more dry feed, and tended to have increased feed efficiency (gain:DMI) compared with calves receiving no LF. Robblee et al. (2003) observed that calves supplemented with 1 g/d of LF added to MR had reduced fecal scores and number of days medicated compared with nontreated calves. Average daily gain and feed efficiency were increased in calves fed 1 g/d of LF during the preweaning phase compared with calves on other treatments.
Lactoferrin in colostrum may serve several purposes to the newborn calf; it may offer protection from infection, stimulate carbohydrate absorption (Teraguchi et al., 1998), and increase small intestine epithelial cell size (Zhang et al., 2001). A D-xylose absorption test is an indirect measure of intestinal absorptive capacity. Several studies have included xylose tests on young calves to evaluate intestinal function (Hammon and Blum, 1997; Kuhne et al., 2000; Rauprich et al., 2000).
The objectives of this study were to evaluate intensified calf feeding on starter intakes, performance, and parameters indicating rumen development and to observe the performance, health, and intestinal function of calves fed 1 g/d of bovine LF supplementation pre-weaning.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONSACKNOWLEDGEMENTSREFERENCES |
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At birth, 34 Holstein heifers (initial BW of 43.1 ± 5.3 kg) were randomly assigned by blocks of 4 to 1 of 4 treatments: nonmedicated conventional (20% CP: 20% fat,) MR with (CL) or without (C0) 1 g of supplemental bovine LF (n = 9 each group); or nonmedicated intensified MR (28% CP: 20% fat) with (IL) or without (I0) 1 g of supplemental bovine LF (n = 8 each group). The number of calves was limited by calf availability. The source of LF was bovine milk (Immucell Corp., Portland, ME); iron saturation was 13.2 g/100 g. All calves received 2 L of good quality colostrum (mean IgG = 73.9 mg/dL ± 15.6) tested by a colostrometer within 3 h of birth, and another 2 L within 12 h. A 50-mL aliquot of colostrum was saved and stored at –20°C for IgG and LF analyses using radial immunodiffusion assay (RID; Cardiotech, Louisville, KY). Calves were removed from their dam before the first feeding of colostrum and placed in individual pens (1 m x 2.15 m) in a naturally ventilated, enclosed calf room. Pens were bedded with kiln-dried sawdust. The calves remained in their pens for the duration of the study.
An initial BW, wither height, hip height, heart girth, and hip width were taken by 24 h after birth. Calves were trained to consume MR from a bucket after the colostrum-feeding period. On d 1, calves were fed 2.27 kg of whole milk at 0700 and 1500 h. On d 2, calves began on their respective treatments.
Feed intake and Analysis
All calves had free-choice access to a nonmedicated, pelleted starter (Archer Daniels Midland, Inc., Ft. Wayne, IN) and fresh water for the duration of the study. The starter was experimental and consisted of grain, plant protein, fat, vitamins, minerals, and molasses. Fresh starter was fed once daily in the morning. The starter was offered in 227.5-g increments; when a calf consumed 227.5 g, she was offered more starter. Starter orts were collected and weighed daily. Calves on C0 and CL treatments received 562 g of MR daily, reconstituted at 15% DM, split into 2 feedings. This remained constant until d 42. Calves on the I0 and IL treatments were fed based on ME requirements. From d 2 to 9, calves were fed MR to meet an intake of 0.2 Mcal/kg of BW0.75. From d 10 to 42, calves were fed to meet an intake of 0.27 Mcal/kg of BW0.75 (Tikofsky et al., 2001). All calves were weaned following the same protocol; calves were switched to one morning MR feeding on d 42 for 7 d, and then were weaned completely at d 49. Calves remained on the study for 14 d postweaning for a total of 63 d on the study.
Dry matter intake was calculated on a daily basis. The DM of the orts was determined daily, and the DM of starter and MR powder was determined for each 22.7-kg bag. The DM of the orts was determined by drying in a forced-air convection oven (VWR Scientific Products Corp., Boston, MA) for 6 h at 60°C. A sample from each day was ground through a 1-mm screen using a Wiley mill (Thomas Scientific, Swedesboro, NJ) and composited into preweaning and postweaning periods for nutrient analysis. The DM of the MR powder and starter was determined by drying samples in the same forced-air convection oven at 60°C for 24 h. Samples from each bag of MR (50 g) and starter were saved and stored at –20°C. When the experiment was completed, samples were composited for nutrient analysis. Composited starter samples (75 g/bag) were dried in the forced-air convection oven at 60°C for 6 h. Composites of starter were ground through a 1-mm screen using a Wiley mill. Milk replacer and starter were analyzed for CP (AOAC, 1979), fatty acid or fat content (AOAC, 1995), and Ca, P, Mg, and Fe (AOAC, 1990), and LF after reconstituting the milk replacer to 15% DM (RID; Cardiotech). Milk replacer was analyzed for intake energy by an adiabatic bomb calorimeter (Parr Instruments Co., Moline, IL). Starter was analyzed for NDF (Goering and Van Soest, 1970). Chemical analysis of MR and starter are shown in Table 1
. Lactoferrin content of the intensified and control MR was 1.19 ± 0.04 mg/g of DM and 0.45 ± 0.01 mg/g of DM, respectively. These amounts of LF consumed fall within the range of LF fed in the studies of Joslin et al. (2002) and Robblee et al. (2003). The maximum amount of LF consumed in this experiment was 2.6 g/d at the highest consumption observed for the IL treatment. Average LF content of colostrum was 1.12 ± 0.15 g/L.
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Blood Collection
Blood was collected from all calves twice weekly on Mondays and Thursdays before weights and measurements were taken. Blood was collected via jugular venipuncture using 5-mL evacuated tubes. Tubes without anticoagulant were used for the determination of BUN and were stored at 4°C for 1 h before centrifugation. Blood was centrifuged at 3,300 x g for 20 min. Supernatants were divided into aliquots and stored at –20°C until analyzed.
On d 10 (±1 d), D-xylose (0.5 g/kg of BW) was fed to each calf by adding it to the MR at the a.m. feeding. Blood samples were taken before (0 h) and 0.5, 1, 2, 3, 4, 6, 8, and 12 h after feeding. Calves were fasted for entire blood sampling time, but were allowed access to free-choice water. Blood samples were collected via jugular venipuncture into evacuated tubes containing 15% tripotassium EDTA to measure D-xylose and glucose concentrations in the plasma.
Blood Analyses
Blood urea N concentration was determined using Procedure No. 535 (Sigma Chemical Co., St. Louis, MO). Serum IgG concentration from 24-h samples was determined using RID (Cardiotech). D-Xylose and glucose concentrations were measured in blood samples collected on d 10 of life. Plasma D-xylose concentration was measured as described by Merritt and Duelly (1983). Plasma glucose concentration was determined using a glucose oxidase based kit (Wako, Richmond, VA).
Statistical Analyses
A randomized complete block design was used; calves were randomly assigned to treatment in blocks of 4 based on birth order. An ANOVA was conducted using the MIXED procedure of SAS (SAS Institute, 2001). The mixed effects model used was as follows:
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where Yi is the dependent continuous variable, µ is the overall mean, Bi is the random effect of block (i = 1,...9), Lj is the fixed effect of lactoferrin source (j = 0,1), Mk is the fixed effect of milk replacer source (k = 20,...28), LMjk is the fixed effect of the interaction between the jth lactoferrin source and the kth milk replacer source, Cijkl is the value of the covariate variable for the lth calf of the ith block of jth lactoferrin and kth milk replacer source (l = 1, 34), and eijkl is the random residual 
N (0,
2).
Data were run through 3 covariance structures: unstructured, compound symmetry, and first order autoregressive. First order autoregressive was the covariance structure selected due to smaller Bayesian information criteria values. Initial BW was used as a covariate for DMI and weight calculations, and initial skeletal measurements were used as covariates for the respective measurement. Initial blood values were used as covariates for each hour for glucose and xylose concentrations. Significance was determined at a probability value of 0.05. Degrees of freedom were determined using the Sattherwaite option of the MIXED procedure of SAS (SAS Institute, 2001). One calf was removed from the final statistical analysis due to an allergic reaction to penicillin at wk 5.
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONSACKNOWLEDGEMENTSREFERENCES |
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and Figures 1 and 2. Calves fed the intensified treatments had greater MR intake over the entire treatment period (Table 2, P < 0.001). There was an effect of MR on starter intake during the entire experiment except during wk 1 and 2. Calves on conventional treatments consumed more starter than calves fed intensified treatments (Figure 1). Similarly, there was an effect of MR on total DMI during the entire experiment but not during weaning (Table 2, Figure 2). There was a trend (P < 0.10) during the preweaning period for calves fed CL to consume more DM than calves fed C0, but calves fed I0 consumed more DM than those fed IL.
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; Figure 3, P < 0.001). There was a trend for intensified-fed calves to be heavier preweaning than calves fed control MR (P <0.10). There were no differences in BW postweaning. Preweaning, weaning, and overall ADG were higher for intensified-fed calves than calves fed conventional treatments (Table 3, Figure 3). There were no differences postweaning. Lactoferrin had no effect on BW, ADG, and ADG per DMI.
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, Figure 4). Calves on intensified treatments were more efficient preweaning than conventionally fed calves (P < 0.01), but calves on conventional treatments were more efficient during weaning than intensified-fed calves (P < 0.001). There were no differences postweaning and overall.
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). Intensified MR-fed calves were taller at the hip than conventionally fed calves during weaning and postweaning (P < 0.05; Table 4). There was a MR effect preweaning (P < 0.01), weaning (P < 0.001), and postweaning (P < 0.05) for heart girth; intensified-fed calves had larger heart girths than conventionally fed calves (Table 4). There was also an MR effect on hip width during weaning (P < 0.01) and postweaning (P < 0.05); intensified-fed calves had larger hip widths than conventionally fed calves. There was a preweaning trend (P < 0.10) for intensified-fed calves to have larger hip widths than conventionally fed calves (Table 4).
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There was a preweaning (P < 0.05) MR effect on days medicated, with conventionally fed calves having fewer days medicated than intensified-fed calves (Table 5). Control calves also had fewer days medicated overall than intensified-fed calves (P < 0.05). There was no treatment effect on fecal scores preweaning, postweaning and overall. There was an MR effect during weaning on fecal scores, with intensified-fed calves having lower fecal scores than calves receiving the conventional treatments (P < 0.05). There was no effect of LF.
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). There was a postweaning LF trend (P < 0.10) for BUN, with calves that had received LF having higher BUN concentrations than those not receiving LF (Table 6).
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONSACKNOWLEDGEMENTSREFERENCES |
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Joslin et al. (2002) observed increased starter consumption preweaning in calves fed 1 or 10 g/d of LF. This was not observed in the present study. As expected, calves receiving the intensified treatments had higher total DMI but lower starter intakes. These calves were fed almost at ad libitum liquid intakes, thereby giving the calves no incentive to consume appreciable amounts of dry feed, which is necessary for rumen development (Davis and Drackley, 1998). In contrast, calves on conventional treatments had consistently higher starter intakes from wk 3 until the completion of the study. For consistency purposes, weaning was held constant regardless of the MR fed. In practice, calves fed conventional treatments could have been weaned earlier than 7 wk (Greenwood et al., 1997). Calves fed intensified treatments doubled their starter intake during weaning, but on average it was 50% of the starter intake that the conventionally fed calves were consuming. Postweaning, there was a difference in DMI, but all calves were eating appreciable amounts of starter.
There was an MR effect on BW; intensified-fed calves were heavier during the preweaning and weaning phases. Previous research has shown that intensified-fed calves are heavier than those raised conventionally (Diaz et al., 2001; Blome et al., 2003; Brown et al., 2005). Calves on this study did not maintain the weight advantage postweaning. This may be an example of compensatory growth occurring with the restricted-fed heifers (Lacasse et al., 1994). This response is similar to older heifers raised in a stair-step regimen (Ford and Park, 2001). After inducing compensatory growth during an allometric phase of growth, mammary gland development and energy and protein metabolic status were improved (Ford and Park, 2001). Even though the conventionally fed heifers were not capitalizing on early, fast growth, they were able to compensate in BW by d 63.
The MR effect on ADG seen preweaning was a function of higher total DMI and heavier BW for the calves fed intensified treatments. The effect was reversed during weaning; calves fed conventional treatments had a 5-fold increase in ADG over calves on the intensified treatments. This can be attributed to the 50% decrease in MR fed during weaning, coupled with lower starter intakes compared with conventionally fed calves. Joslin et al. (2002) observed an increase in ADG preweaning when calves were fed either dose of 1 or 10 g/d of LF. Robblee et al. (2003) saw a linear effect of LF on pre-weaning ADG with calves fed 1, 2, or 3 g/d of LF. This effect of LF was not apparent in this experiment.
Young animals are very efficient at converting dietary protein to body protein. In support of research with young nonruminant animals and with ruminants raised on this intensified regimen (Diaz et al., 2001; Blome et al., 2003), calves on the intensified treatments had increased ADG per DMI preweaning. During weaning, calves receiving conventional treatments were more efficient, reflecting the decrease in ADG and DMI of the calves on the intensified treatments. An intensified MR program may not have value if calves lose the effects of gains and efficiencies acquired preweaning after weaning.
In contrast to the current study in which LF had no effect ADG per DMI, Robblee et al. (2003) observed a linear effect on ADG per DMI with increasing amounts of LF. Humphrey et al. (2002) saw increased ADG per DMI in chicks fed LF compared with control chicks, and that equaled the antibiotic treatment used in their experiment. This was not seen in this study.
Joslin et al. (2002) and Robblee et al. (2003) observed increase heart girth gain for calves fed LF. In the present study, there was a trend for increased wither height gain in calves fed LF. There is no explanation for this effect because BW, ADG, and feed efficiency were unaffected by LF addition. The effects on skeletal growth are reflective of the increase in frame size seen with calves fed on the intensified-fed program. Calves fed the intensified treatments were taller at the hip, had larger heart girths, and larger hip widths. Increased skeletal growth is more important than increased BW; one of the goals of an intensified heifer-raising program is to reduce the age at first breeding, which is directly related to frame size (Heinrichs and Hargrove, 1987). There was a trend for the interaction for average daily hip width gain overall but there is no clear explanation for this.
Robblee et al. (2003) observed a quadratic effect on fecal scores and days medicated. Calves fed 1 g/d of LF had the lowest preweaning fecal scores and number of days medicated. There was no effect on fecal scores or days medicated in the current study. This supports the findings of Joslin et al. (2002). Based on the previous research conducted in our laboratory, it is surprising that fecal scores and days medicated were not affected by LF. This may be due to the fact that preweaning fecal scores and days medicated were at least 50% lower that than reported by Joslin et al. (2002). The overall days medicated in the current study from the CL treatment compared with the 1 g/d of LF from Robblee et al. (2003) were slightly higher (1.89 vs. 1.59, respectively).
There was an MR effect on both preweaning and overall days medicated, with calves receiving the intensified MR having more days medicated than those on conventional treatments. It would be expected that a similar effect would be seen in fecal scores, but this was not observed. This may be because fecal scores were only recorded 3 times weekly, but the calves could be medicated any time during the week. The MR effect seen during weaning of conventionally fed calves having higher fecal scores may be explained by the fact that the calves at this point were eating an average of 1,256 g of starter compared with the intensified-fed calves eating an average of 635 g of starter. Because these calves could have been weaned much earlier and would have been started on a TMR, it is possible that they had mild acidosis, causing some diarrhea. These calves, however, had no further challenges postweaning.
There was no effect of LF on xylose and glucose absorption. Xylose absorption is used as an indirect method to estimate intestinal epithelial size and function (Hammon and Blum, 1997; Kuhne et al., 2000; Rauprich et al., 2000). Previous research with other species indicates that LF has a stimulatory effect on both cell proliferation and increased cell size (Zhang et al., 2001). Zhang et al. (2001) found oral LF increased small intestine size in rat pups. Humphrey et al. (2002) observed increased villus heights in the duodenum of chicks fed rice expressing LF and lysozyme. Results from this study do not support this characteristic of LF in the preruminant calf.
Some of the calves were experiencing slight diarrhea during the xylose challenge, likely impairing the absorptive ability of the small intestine. Xylose is used to determine the health of the small intestine. Diarrhea affects the absorption of nutrients and may mask the true absorptive capacity of the cells. Because calves fed intensified MR consumed greater amounts of both lactose and protein than the conventionally fed calves due to greater DMI, they would be expected to have increased glucose levels compared with conventionally fed calves.
As a sign of excess protein, BUN concentrations were originally determined to observe differences between the CP of the diets and circulating N. Because calves on intensified treatments had lower serum urea pre-weaning, excess protein can be excluded.
It is also possible that calves receiving conventional treatments had more endogenous protein breakdown than intensified-fed calves. It has been reported than in piglets fed water, colostrum, or milk, fractional protein synthesis in the visceral organs was 3- to 4-fold greater in the piglets fed milk or colostrum (Burrin et al., 1992). Perhaps the intensified-fed calves had greater protein synthesis relative to protein ingestion than the conventionally fed calves, which may explain the increased preweaning urea levels in the conventionally fed calves.
Some of the differences seen are also indicative of rumen development. There are better indicators, such as BHBA concentrations, of the conversion of the rumen from immature to mature, such as VFA production and microbial protein synthesis. However, urea N may be an indirect measurement of ammonia production in the rumen. Abdelgadir et al. (1996) noted that in calves receiving more RDP in their diet had higher ruminal ammonia than those with lower RDP diets. Calves consuming conventional treatments were consuming significantly more starter grain, which contained 16.3% RDP and 8.6% RUP (DM basis). This may explain why calves receiving conventional treatments had higher preweaning BUN values.
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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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FOOTNOTES |
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Received for publication March 21, 2006. Accepted for publication July 24, 2006.
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONSACKNOWLEDGEMENTSREFERENCES |
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