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Journal of Animal Science - Animal Nutrition

The effect of restricted milk feeding through conventional or step-down methods with or without forage provision in starter feed on performance of Holstein bull calves1

 

This article in JAS

  1. Vol. 93 No. 8, p. 3979-3989
     
    Received: Dec 30, 2014
    Accepted: May 21, 2015
    Published: July 10, 2015


    2 Corresponding author(s): morteza.h.g@gmail.com
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doi:10.2527/jas.2014-8863
  1. D. Daneshvar*,
  2. M. Khorvash*,
  3. E. Ghasemi*,
  4. A. H. Mahdavi*,
  5. B. Moshiri,
  6. M. Mirzaei,
  7. A. Pezeshki§ and
  8. M. H. Ghaffari 2*
  1. * Department of Animal Science, College of Agriculture, Isfahan University of Technology, Isfahan 84156-83111, Iran
     Ghiam Dairy Complex, Isfahan, Iran
     Department of Animal Science, Faculty of Agriculture and Natural Resources, Arak University, 38156-8-8349 Arak, Iran
    § Department of Production Animal Health, Faculty of Veterinary Medicine, Gastrointestinal Research Group, Calvin, Phoebe and Joan Snyder Institute for Chronic Diseases, University of Calgary, Calgary, Alberta, Canada

Abstract

The objective of the current study was to examine whether step-down (STP) milk feeding method together with forage provision would improve performance, rumen fermentation, nutrient digestibility, blood metabolites, and structural growth of calves. Holstein bull calves (n = 40) were randomly assigned to 1 of 4 treatments in a completely randomized design with a 2 × 2 factorial arrangement. Treatments were 1) conventional (COV) milk feeding without forage provision (COV-NF), 2) COV milk feeding with forage provision, 3) STP milk feeding without forage provision, and 4) STP milk feeding with forage provision. Calves in the COV method (n = 20) received 5.5 L/d milk until d 56 of age followed by 2 L/d milk from d 56 to 59 of age. Calves in the STP method (n = 20) received 7 L/d milk until d 35, 4 L/d milk from d 35 to 48, and 2 L/d milk from d 50 to 59 of age. All the calves received the starter ration from d 3 of the study until d 74 of age. Forage-supplemented calves (n = 10/milk feeding method) received 15% alfalfa hay mixed with finely ground starter as a total mixed ration. All calves were weaned on d 60 of age and remained in the study until d 74. Regardless of the milk feeding method, the final BW (92.54 vs. 83.14 kg/d), starter intake (0.90 vs. 0.65 kg/d), total DMI (1.43 vs. 1.17 kg/d), and ADG (0.73 vs. 0.60 kg/d) were greater (P < 0.01) in forage-supplemented calves than those that received no forage during the preweaning, postweaning, and overall periods. Milk feeding method had no effect on ruminal pH, total VFA, acetate, or acetate:propionate ratio as well as body measurements. Ruminal pH and the molar proportions of acetate were greater (P < 0.05) in the forage-supplemented calves than those that received no forage during the pre- and postweaning periods. Regardless of forage provision, STP methods increased (P < 0.05) the postweaning numbers of monocytes and lymphocytes. Overall, there was no interaction between milk feeding methods and forage provision with respect to BW, DMI, G:F, apparent nutrient digestibility (DM, OM, and CP), and body measurements. The interaction of milk feeding method and forage provision was significant for the rumen concentration of butyrate (P < 0.05), with the highest concentration for the COV-NF treatment on d 35 of the study. In conclusion, independent of the milk feeding method, inclusion of 15% alfalfa hay in starter diets enhances the performance of dairy calves.



INTRODUCTION

Previous studies have shown that restricted milk feeding of calves encourages solid feed consumption (Appleby et al., 2001; Jasper and Weary, 2002) and this has been considered a key contributor to the metabolic and physical development of the rumen (Baldwin et al., 2004). It is clear that milk feeding level has great potential to influence the rumen development indirectly via starter and/or forage intake. Many studies have documented that the gradual decrease of liquid feed provision for dairy calves enhances their solid feed intake (Sweeney et al., 2010) and stimulates rumen development (Khan et al., 2007a; Roth et al., 2008), resulting in improved growth characteristics (Khan et al., 2007b; Sweeney et al., 2010). A liquid feeding method may also change plasma concentration of insulin, IGF-1, and other growth factors (Khan et al., 2007a; Silper et al., 2014), which play an important role in the stimulation of rumen epithelial cell proliferation (Baldwin et al., 2004).

In the conventional (COV) milk feeding method, calves receive a restricted amount of milk or milk replacer (4 L/d, equivalent to approximately 10% of birth weight) during the whole milk-feeding period (Khan et al., 2007a,b; Silper et al., 2014). According to Davis and Drackley (1998), the COV milk feeding method results in decreased alimentary efficiency, thereby leading to suboptimal performance of dairy calves during the whole milk-feeding period. Alternatively, the step-down (STP) milk feeding method allows calves to receive milk at the rate of 20% of BW until 25 d of age. In this method, the rate of milk feeding is gradually decreased between 26 and 30 d of age by diluting the milk with water until a milk-feeding rate of 10% of BW is achieved (Khan et al., 2007a,b).

In addition to benefits of milk feeding method on performance of dairy calves, providing forage in the starter feed of calves may influence DMI and rumen development (Beiranvand et al., 2014; Mirzaei et al., 2015). Forage stimulates physical abrasion of feed particles on the rumen papillae and increases rumen pH to provide a favorable condition for the fiber-digesting microbes (Tamate et al., 1962; Beharka et al., 1998). This improvement in rumen environment could positively affect calf performance (Zitnan et al., 2005; Beiranvand et al., 2014).

To the best of our knowledge, the combined effect of COV or STP liquid feed regimen with or without providing forage in the starter feed on the performance and rumen development of dairy calves has not yet been reported. Those authors hypothesized that using the STP milk feeding method together with forage provision in the starter feed could substantially speed up growth and rumen development in dairy calves. In this study, calves in both milk feeding methods (STP and COV) received the same amount of milk (311 L ± 3) during the preweaning period. Therefore, the aim of the study was to examine the interaction of milk feeding method and forage provision on calf performance when they consume the same and restricted amount of milk.


MATERIALS AND METHODS

Calves, Management, and Treatments

The study was conducted at the Ghiam Agri-Animal Production Co., Isfahan, Iran, under the guidelines of the Iranian Council of Animal Care (1995). Holstein bull calves (n = 40) born between December 2013 and January 2014 (minimum, maximum, and average temperatures recorded as –10 ± 3.09, 24.5 ± 3.09, and 3.37 ± 3.09°C, respectively) were used. Calves were separated from their dams immediately after birth, weighed, and randomly transferred to individual pens (1.5 by 2.5 m) bedded with sawdust that was replenished every 24 or 48 h as required. All the calves were fed 3 to 4 L of colostrum within 2 to 6 h after birth. Blood samples were collected by venipuncture from the jugular vein, using Clot Activator Vacutainers (Vacutest, Arzergrande, Italy), 24 h after the first feeding of colostrum, and serum total protein was determined using a commercially available hand-held refractometer (VET 360; Reichert Inc., Depew, NY). Only calves with a serum protein level > 5.5 mg/dL were included in the study. Holstein bull calves (3 d of age; 41.2 ± 3 kg of BW) were randomly assigned to 1 of 4 treatments in a completely randomized design with a 2 × 2 factorial arrangement. Treatments were 1) COV milk feeding without forage provision (COV-NF), 2) COV milk feeding with forage provision (COV-F), 3) STP milk feeding without forage provision (STP-NF), and 4) STP milk feeding with forage provision. Calves were fed whole milk containing 3.22 ± 0.11% fat, 2.96 ± 0.07% CP, 4.92 ± 0.05% lactose, and 11.77 ± 0.15% total solids from steel buckets twice daily at 0900 and 1800 h. Before milk feeding, the milk was warmed in a water bath to raise its temperature to 39 ± 0.5°C. Calves in the COV method (n = 20) received 5.5 L/d milk (approximately 12% of BW) until d 56 of age, after which they were fed 2 L/d milk (approximately 5% of BW) as morning feeding from d 56 to 60 of age (Fig. 1). Calves in the STP method (n = 20) received 7 L/d milk (approximately 17% of BW) from d 3 to 35, 4 L/d from d 35 to 48, and 2 L/d milk (approximately 5% of BW) during morning feeding from d 50 to 59 of age (Fig. 1). The total quantities of milk consumed by calves in both milk feeding methods (COV and STP) were identical throughout the study (311 ± 3 L). Calves subjected to both milk feeding methods (COV and STP) were weaned on d 60 and remained in the study until d 74. From d 3 of the study until d 74, all the calves received the starter ration ad libitum; however, the forage-supplemented calves (n = 10/milk feeding method) received a starter containing 15% chopped alfalfa hay (AH; particle size distribution: 1.80 ± 0.1% greater than 18 mm, 29.71 ± 3.4% between 8 and 18 mm, 47.7 ± 3.4% between 1.18 and 8 mm, and 20.76 ± 6.5% less than 1.18 mm and chop length 3.5 ± 0.4 cm) as a total mixed ration (TMR) mixed with finely ground concentrates throughout the study. The ingredients and nutrient compositions of the starters are presented in Table 1. The calves had free access to fresh water throughout the study.

Figure 1.
Figure 1.

Milk feeding method for calves fed through conventional (5.5 L of milk/d until 56 d and 2 L/d from 56 to 60 d of age) or step-down (7 L of milk/d until 35 d, 4 L/d from 35 to 49 d, and 2 L/d from 50 to 60 d of age) methods. Calves in both groups were weaned at 60 d of age.

 

View Full Table | Close Full ViewTable 1.

Ingredients and chemical composition of the experimental starter feeds

 
Treatment1
Item Control 15% alfalfa hay
Ingredient, % of DM basis
    Alfalfa hay 15
    Corn grain, ground 51.56 45.10
    Soybean meal (45% CP) 30.09 27.40
    Barley grain, ground 12.03 6.00
    Full fat soybean 3.01 3.60
    Vitamin and mineral mix2 1.00 1.00
    Calcium carbonate 1.50 1.10
    Sodium bicarbonate 0.30 0.30
    Salt 0.50 0.50
Chemical composition, % of DM
    DM 88.35 87.70
    CP 21.78 21.24
    Fat 3.50 3.30
    NDF 14.69 19.88
    NFC3 59.6 54.0
    Starch 54.7 47.9
    Ash 6.00 7.00
1Control = concentrate with no forage; 15% alfalfa hay is the concentrate + 15% alfalfa hay.
2Contained per kilogram of supplement: 250,000 IU of vitamin A, 50,000 IU of vitamin D, 1,500 IU of vitamin E, 2.25 g of Mn, 120 g of Ca, 7.7 g of Zn, 20 g of P, 20.5 g of Mg, 186 g of Na, 1.25 g of Fe, 3 g of S, 14 mg of Co, 1.25 g of Cu, 56 mg of I, and 10 mg of Se.
3NFC = nonfiber carbohydrate; calculated as DM – (NDF + CP + ether extract + ash) (NRC, 2001).

Feed Intake, BW, and Total Tract Digestibility

Starter feed intake and milk intake were measured daily and BW were recorded weekly during the pre- (d 1 to 60) and postweaning (d 60 to 74) periods. Actual milk intake was calculated by subtracting the amount of milk refused from the total amount of milk offered to the calves. To calculate feed intake, the offered and refused amounts of TMR were recorded daily on an individual basis.

Acid insoluble ash (AIA) was used as an internal marker to calculate the apparent digestibility of DM, OM, NDF, and CP from d 67 to 74. Fecal samples were collected directly from the rectum of each calf after morning and evening feedings. Apparent digestibility was calculated based on the concentrations of these nutrients and of AIA in the feed (corrected for refusals) and fecal samples (Van Keulen and Young, 1977).

Body Measurements

Body measurements including body length, wither height, heart girth, body barrel, and hip height and width of the calves were measured according to Lesmeister and Heinrichs (2004) at birth, at weaning (d 60), and at the end of the study period (d 74).

Rumen and Blood Sampling and Storage

On d 35 and 74 of the study, rumen fluid samples were collected with a stomach tube 4 h after morning feeding and strained through 4 layers of cheesecloth to obtain rumen fluid. The pH was immediately measured using a hand-held pH meter (HI 8314 membrane pH meter; Hanna Instruments, Villafranca, Italy). Four milliliters of the rumen fluid was acidified with 1 mL of 25% metaphosphoric acid and stored (–20°C) until analysis for VFA.

Blood samples were collected 3 h after the morning feeding on d 35 and 74 of the study, by venipuncture from the jugular vein, using Clot Activator Vacutainers (Vacutest). Samples were immediately placed on ice after collection. Tubes were centrifuged at 2,000 × g at 4°C for 20 min within 2 h of sampling. The serum was separated and stored at –20°C for subsequent analysis. Whole blood samples were also collected into evacuated tubes containing K3-EDTA (Becton Dickinson Vacutainer Systems, Franklin Lakes, NJ) on d 61 and transferred to the laboratory within 6 h to determine the number of red blood cells and white blood cells (WBC), differential WBC, hemoglobin concentration, mean corpuscular hemoglobin concentration, hematocrit, and platelets.

Chemical and Biochemical Analyses

Feed and refusals were mixed thoroughly and ground to pass a 1-mm screen in a Wiley mill (Ogaw Seiki Co., Ltd., Tokyo, Japan) before chemical analyses. Feed, refusals, and fecal samples were analyzed for DM content (method 934.01; AOAC, 1990) and for CP (method 988.05; AOAC, 1990). Neutral detergent fiber was analyzed without the use of sodium sulfite and with the inclusion of α-amylase (Van Soest et al., 1991). Starch content was determined enzymatically as described by Rijnen et al. (2001).

Acid insoluble ash was used as an internal marker to estimate the apparent total tract digestibility of DM, CP, NDF, and ADF (Van Keulen and Young, 1977). Apparent digestibility was calculated based on the relative amount of these nutrients and of AIA in the feed, feed refusal, and feces.

Two consecutive bulk milk samples were obtained at weekly intervals. Milk samples were pooled to 1 sample and kept at room temperature (i.e., 23°C) with the preservative potassium dichromate. Milk samples were analyzed for fat, CP, lactose, and total solids content by Milkoscan (Foss Electric, Hillerød, Denmark; AOAC International, 1996).

Rumen samples were analyzed for VFA by gas chromatography (model CP-9002; Chrompack, Middelburg, The Netherlands) with a 50-m (0.32 mm i.d.) silica-fused column (CP-Wax Chrompack Capillary Column; Varian, Palo Alto, CA). Helium was used as the carrier gas and oven initial and final temperatures were 55 and 195°C, respectively. Detector and injector temperatures were set at 250°C. Crotonic acid (1:7, vol/vol) was used as the internal standard.

Blood metabolite concentrations were spectrophotometrically (UNICCO, 2100; Zistchemi Co., Tehran, Iran) determined using commercially available kits (Pars Azmoon Company, Tehran, Iran; catalogue numbers: glucose [1-500-017], total protein [1-500-028], albumin [1-500-001], globulin [1-500-011], and urea nitrogen [1-400-029]) according to the manufacturer’s instructions.

Whole blood samples were analyzed using a Cell-Dyn 3500R automated veterinary hematology analyzer (Abbott Diagnostics, Santa Clara, CA) to determine the number of red blood cells and WBC, differential WBC, hemoglobin concentration, mean corpuscular hemoglobin concentration, hematocrit, and platelets according to the manufacturer’s instructions.

Statistical Analyses

Body weight, DMI, ADG, and G:F data were analyzed separately for the preweaning (d 1 to 60 of the study), postweaning (d 61 to 74), and overall (d 1 to 74) periods. Data were subjected to ANOVA using the MIXED procedure of SAS 9.1(SAS Inst. Inc., Cary, NC) with time (week) as repeated measures for BW, DMI, ADG, and G:F. The statistical model used included the effects of milk feeding method, forage provision, and their interactions as fixed effects and calf within treatment as a random effect. Initial BW was considered a covariate for the final weight analysis. The initial values were considered a covariate for structural growth variables. Apparent nutrient digestibility was analyzed as described above but without including the initial BW as a covariate in the analysis model. When the main and interaction effects were significant, mean separation analysis was conducted using a Tukey’s multiple range test. Significance was declared at P < 0.05 and trends were considered when 0.05 < P < 0.10.


RESULTS AND DISCUSSION

Feed Intake, BW, and Nutrient Digestibility

Body weight, feed intake, ADG, feed efficiency, and nutrient digestibility results are presented in Table 2. In the current study, no interaction was detected between milk feeding method and forage provision with respect to the starter intake, total DMI, ADG, BW, and G:F. One possible reason for no interaction between milk feeding method and forage provision is that calves in both milk feeding methods (STP and COV) received the same amount of milk during preweaning period.


View Full Table | Close Full ViewTable 2.

Body weight, DMI, G:F, and nutrient digestibility of Holstein male calves fed milk through either the conventional or the step-down method with or without forage provision

 
Treatment2
P-value3
Item1 COV-NF COV-F STP-NF STP-F SEM MMF FOR MMF × FOR
BW, kg
    Preweaning 58.84 58.92 59.31 60.68 1.14 0.33 0.52 0.57
    Postweaning 81.01b 85.21ab 78.19b 87.12a 2.23 0.84 0.01 0.32
    Final 85.04b 92.22a 81.23b 92.85a 2.84 0.57 0.01 0.44
DMI of starter, kg/d
    Preweaning 0.54b 0.58ab 0.49b 0.68a 0.05 0.59 0.02 0.17
    Postweaning 1.62b 2.38a 1.64b 2.36a 0.16 0.99 0.01 0.91
    Overall 0.67b 0.89a 0.63b 0.91a 0.07 0.88 0.01 0.68
Total DMI,4 kg/d
    Preweaning 1.14b 1.20ab 1.09b 1.27a 0.05 0.84 0.02 0.22
    Postweaning 1.62b 2.38a 1.64b 2.36a 0.16 0.99 0.01 0.91
    Overall 1.16b 1.40a 1.17b 1.45a 0.07 0.74 0.01 0.75
ADG, kg/d
    Preweaning 0.59b 0.62ab 0.57b 0.68a 0.03 0.65 0.03 0.28
    Postweaning 0.80b 1.31a 0.61b 1.07a 0.12 0.09 0.01 0.82
    Overall 0.62b 0.72a 0.58b 0.73a 0.04 0.68 0.01 0.56
G:F
    Preweaning 0.49 0.49 0.54 0.53 0.03 0.09 0.95 0.96
    Postweaning 0.46bc 0.57a 0.37c 0.44ab 0.05 0.01 0.02 0.94
    Overall 0.51 0.51 0.50 0.53 0.02 0.60 0.26 0.48
Total ME,5 Mcal/d
    Preweaning 6.67b 6.80ab 6.55b 7.08a 0.14 0.59 0.02 0.17
    Postweaning 4.57b 6.69a 4.62b 6.64a 0.46 0.98 0.01 0.91
    Overall 6.32b 6.94a 6.20b 7.01a 0.19 0.88 0.01 0.68
Apparent nutrient digestibility
    DM 77.76a 70.91ab 72.45ab 65.64b 2.87 0.07 0.02 0.99
    OM 78.83a 72.21ab 73.55ab 67.10b 2.83 0.07 0.02 0.98
    NDF 51.81 46.52 43.64 41.97 5.54 0.25 0.53 0.74
    CP 74.15a 68.42ab 71.38ab 61.15b 3.15 0.11 0.01 0.47
a–cMeans within a row with different superscripts letters are significantly different (P < 0.05).
1Periods: preweaning is from 1 to 60 d of age; postweaning is from 61 to 74 d of age.
2COV-NF = conventional milk feeding without forage provision; STP-NF = step-down milk feeding without forage provision; COV-F = conventional milk feeding with forage provision; STP-F = step-down milk feeding with forage provision.
3MMF = method of milk feeding; FOR = effect of forage provision; MMF × FOR = interaction between method of milk feeding and forage provision.
4DMI includes milk, starter, and hay.
5Total (milk + starter) ME per day.

In the current study, the milk feeding methods (COV or STP) had no effects on DMI during the preweaning and postweaning periods. In the current study, the amount of milk offered was kept constant between groups to investigate the effect of method of milk feeding on calf performance. Similar performance between calves assigned to different milk feeding methods could be attributed to consumption of the same amount of milk offered in the STP or COV methods (311 ± 3 L) in the present study. Calves fed a restricted amount of milk or milk replacer (equivalent to 10% of BW) typically consume more starter the weeks before weaning (Jasper and Weary, 2002; Cowles et al., 2006; Raeth-Knight et al., 2009). It appears that rather than milk feeding method, the quantity of milk offered to dairy calves influences their DMI. There were some differences between the STP method used in this study and that used by others (Khan et al., 2007a,b). The amount of milk fed to calves and weaning age was different between these studies. In the current study, calves assigned to both milk feeding methods were provided the same and restricted amounts of milk; however, calves subjected to different milk feeding methods did not receive the same amount of milk in previous studies (Khan et al., 2007a,b). In this study, calves were weaned on d 60 of age but in the studies by Khan et al. (2007a,b), calves were gradually weaned between 45 and 49 d of age. Previous studies have shown that the volume of milk fed to dairy calves can influence their dry feed consumption (Jasper and Weary, 2002; Khan et al., 2011). Khan et al. (2007a) reported that calves fed milk with the STP method had greater DMI than those fed with the COV method (milk feeding at 10% of BW/d). In that study, the STP calves consumed 51.6% more milk than the conventionally fed calves during the preweaning period.

During the preweaning period, no differences were found for G:F among the treatments, but G:F was greater (P < 0.01) for calves fed COV-F diets than for those fed other diets during the postweaning period. Postweaning ADG tended (P = 0.09) to be lower in calves fed the STP method compared with that on the COV milk feeding method. The lower ADG and feed efficiency of calves fed milk with the STP method could be associated with lower nutrient digestibility.

Regardless of the milk feeding method, the final BW (92.54 vs. 83.14 kg/d; F = 10.93, df = 35), starter intake (0.90 vs. 0.65 kg/d), total DMI (1.43 vs. 1.17 kg/d), ADG (0.73 vs. 0.60 kg/d), and total ME (milk and starter) were greater (P < 0.01) for forage-supplemented calves compared with unsupplemented calves during the preweaning, postweaning, and overall periods. The effect of dietary forage on calf performance is controversial. Although some authors reported an improvement in performance of forage-supplemented calves (Coverdale et al., 2004; Khan et al., 2011; Castells et al., 2012), others were not able to show this improvement (Hill et al., 2008, 2010). Data obtained from the current study are in line with results of Terré et al. (2013), where forage-supplemented calves had greater postweaning pelleted starter intake and ADG compared with non-forage-supplemented calves. It has been widely recognized that feeding forage increases postweaning total DMI (Khan et al., 2011; Terré et al., 2013) and live weight of preweaned and weaned calves (Thomas and Hinks, 1982). Thomas and Hinks (1982) reported that there was a positive relationship between postweaning rumen pH and feed intake. In their study, greater roughage consumption led to higher rumen pH and increased total feed intake. Coverdale et al. (2004) showed that the inclusion of chopped hay to diets of young calves can favorably alter the rumen environment, resulting in improvement of G:F.

No interaction was observed between milk feeding method and forage provision for apparent nutrient digestibility. The overall apparent digestibility values of DM and OM tended (P = 0.07) to be lower in calves fed milk through the STP method than those fed milk through the COV method during the week following weaning (d 67 of the study), indicating that STP calves may have a less developed rumen than COV animals. Furthermore, the total tract apparent digestibility values of DM (P < 0.05), OM (P < 0.05), and CP (P < 0.01) were lower in forage-supplemented calves compared with the non-forage-supplemented calves. The apparent digestibility of NDF did not differ between treatments. Apparent digestibility of OM was significantly lower (P < 0.05) for forage-supplemented calves compared with non-forage-supplemented calves (69.65 vs. 79.19% DM). In the current study, the increased (P < 0.01) G:F of calves fed milk with the COV method compared with those fed with the STP method during the postweaning period may be due to (P = 0.07) to greater OM digestibility. The lower digestibility of DM, OM, and CP in forage-supplemented calves could be the result of high-fiber diets and high DMI compromising diet digestibility (Zanton and Heinrichs, 2008). Porter et al. (2007) reported that DM digestibility in calves fed high-fiber diets was lower than those fed low-fiber diets, which might be due to a forage digestibility effect.

Body Measurements

Mean body length, withers height, heart girth, body barrel, hip height, and hip width at d 60 (weaning) and 74 are presented in Table 3. Despite the increases in heart girth (P < 0.05) and body barrel (P < 0.01) in forage-supplemented calves compared with non-forage-supplemented calves, mean body length, withers height, hip height, and hip width of calves were not changed among treatments at 60 and 74 d of age, regardless of the milk feeding method. Results regarding body measurements herein are in agreement with those reported by Beiranvand et al. (2014), who did not find differences in body length, hip height, or hip width of calves fed 10% AH. However, Hill et al. (2010) found a linear decline in hip width as the level of AH in the diet increases.


View Full Table | Close Full ViewTable 3.

Average body measurements of Holstein male calves fed milk through either the conventional or the step-down method with or without forage provision.

 
Treatment1
P-value2
Item COV-NF COV-F STP-NF STP-F SEM MMF FOR MMF × FOR
Body length, cm
    At weaning, d 60 52.39 53.30 52.99 53.29 0.61 0.63 0.33 0.62
    At end, d 74 53.95 55.15 54.14 54.63 0.56 0.77 0.14 0.53
Withers height, cm
    At weaning, d 60 87.19 87.01 87.13 86.77 0.66 0.81 0.69 0.89
    At end d 74 89.25 89.76 88.98 89.32 0.70 0.61 0.56 0.90
Heart girth, cm
    At weaning, d 60 95.64 96.63 95.64 96.33 0.82 0.85 0.32 0.85
    At end d 74 99.0ab 101.5a 98.1b 100.3ab 1.03 0.32 0.03 0.89
Body barrel, cm
    At weaning, d 60 104.4 106.2 105.8 108.1 1.48 0.28 0.16 0.86
    At end, d 74 111.4b 115.1a 110.5b 116.2a 1.56 0.94 0.01 0.53
Hip height, cm
    At weaning, d 60 89.97 89.17 90.39 89.25 0.69 0.72 0.17 0.80
    At end, d 74 91.66 91.97 91.72 91.55 0.73 0.81 0.92 0.74
Hip width, cm
    At weaning, d 60 23.61 23.15 23.35 23.59 0.22 0.69 0.63 0.13
    At end, d 74 24.39 24.55 24.01 24.57 0.33 0.58 0.29 0.55
a,bMeans within a row with different superscripts letters are significantly different (P < 0.05).
1COV-NF = conventional milk feeding without forage provision; STP-NF = step-down milk feeding without forage provision; COV-F = conventional milk feeding with forage provision; STP-F = step-down milk feeding with forage provision
2MMF = method of milk feeding; FOR = effect of forage provision; MMF × FOR = interaction between method of milk feeding and forage provision.

Rumen Fermentation Parameters

The data for rumen fermentation parameters are presented in Table 4. The rumen fermentation profile was altered by forage provision. Regardless of the milk feeding method, forage-supplemented calves had greater ruminal pH than the non-forage-supplemented calves on 35 (P < 0.05) and 74 d (P < 0.01) of age, which is in line with previously reported data (Thomas and Hinks, 1982; Khan et al., 2011). Krause et al. (2002) reported that mean ruminal pH was positively correlated with the time spent on ruminating and chewing. In the current study, the greater ruminal pH in the forage-supplemented calves may be attributed to the greater time spent on ruminating, which is beneficial for the salivary secretion and rumen buffering (Mertens, 1997). Furthermore, feeding high-starch starter in dairy calves as a starter in this study was found to decrease rumen pH (Khan et al., 2008). Feeding strategies that can improve rumen pH, such as forage provision (Laarman et al., 2012), may improve calf performance by increasing concentrate DMI (Castells et al., 2012). In this study, inclusion of AH in calf starter was effective in increasing rumen pH as reported by Mirzaei et al. (2015).


View Full Table | Close Full ViewTable 4.

Average ruminal pH, and VFA concentrations of Holstein male calves fed milk through either the conventional or the step-down method with or without forage provision

 
Treatment1
P-value2
Item COV-NF COV-F STP-NF STP-F SEM MMF FOR MMF × FOR
Ruminal pH
    d 35 5.18b 5.71a 5.59a 5.64a 0.14 0.23 0.05 0.09
    d 74 5.08b 5.56a 5.02b 5.49a 0.08 0.48 0.01 0.90
Total VFA, mmol/L
    d 35 156.2a 118.4b 148.7a 133.1ab 11.9 0.76 0.03 0.36
    d 74 198.8a 169.1b 192.8a 166.9b 12.6 0.88 0.03 0.74
Individual VFA, mol/100 mol
Acetate
    d 35 48.79 55.30 55.33 55.90 1.11 0.09 0.09 0.15
    d 74 49.16ab 51.39ab 46.16b 53.00a 0.87 0.64 0.01 0.13
Propionate
    d 35 34.82 33.77 30.73 30.51 1.13 0.12 0.79 0.86
    d 74 33.73 38.16 33.44 35.64 1.23 0.58 0.20 0.66
Butyrate
    d 35 11.88a 7.47b 9.34ab 9.69ab 0.58 0.88 0.06 0.03
    d 74 10.43ab 7.14b 14.20a 7.47b 0.96 0.22 0.01 0.30
Valerate
    d 35 3.28 3.26 3.01 2.71 0.28 0.88 0.26 0.53
    d 74 4.43a 2.20b 3.95a 2.53b 0.36 0.91 0.01 0.54
Isovalerate
    d 35 0.61 0.63 0.91 0.61 0.09 0.48 0.48 0.42
    d 74 0.61 0.59 0.47 0.48 0.05 0.20 0.98 0.87
Acetate:propionate
    d 35 1.44 1.65 1.76 1.88 0.10 0.11 0.33 0.78
    d 74 1.33 1.36 1.24 1.49 0.07 0.73 0.09 0.17
a,bMeans within a row with different superscripts letters are significantly different (P < 0.05).
1COV-NF = conventional milk feeding without forage provision; STP-NF = step-down milk feeding without forage provision; COV-F = conventional milk feeding with forage provision; STP-F = step-down milk feeding with forage provision.
2MMF = method of milk feeding; FOR = effect of forage provision; MMF × FOR = interaction between method of milk feeding and forage provision.

In the current study, calves received AH had a lower concentration of total VFA than calves fed non-forage-supplemented diets. This may be attributed to lower digestibility of OM by ruminal microbes in the forage-supplemented diets, which is in line with results of Wanapat et al. (2013). Values for ruminal VFA concentrations in the current experiment are in the range previously reported in the literature (Coverdale et al., 2004; Suárez et al., 2007). Results reported herein are in accordance with Castells et al. (2013), who found a decrease in ruminal VFA concentration in forage-supplemented calves. In contrast, Suárez et al. (2007) did not observe differences in total rumen VFA concentrations between forage-supplemented calves and control calves. This discrepancy among studies could probably be attributed to the structure of the starter, forage supplementation as a part of a TMR, and the amount of milk consumed.

The molar proportion of ruminal acetate, propionate, valerate, isovalerate, and acetate to propionate ratio was similar across treatments on d 35 of the study. An interaction (P < 0.05) of milk feeding method and forage provision influenced the molar proportions of butyrate with the highest concentration in COV-NF treatment on d 35 of the study. No effect of milk feeding method on the molar proportions of individual VFA was detected. Molar proportion of acetate was greater (P < 0.01) in forage-supplemented calves than in the non-forage-supplemented calves on d 74 of the study. Greater acetate proportions are usually observed in forage-supplemented diets (Yang et al., 2001; Terré et al., 2013), as occurred in the present study (P < 0.01). Castells et al. (2013) also noted that acetate concentration in the rumen liquid tended to be greater in forage-supplemented calves than in the non-forage-supplemented calves. In the current study, the molar proportions of butyrate was lower (P < 0.01) in forage-supplemented calves compared with those supplemented with no forage on d 74 of the study, which is in agreement with the findings of Quigley et al. (1992). Baldwin et al. (2004) noted that butyrate has the greatest effects on rumen epithelial development because of increased blood flow during absorption and metabolism and a direct effect on ruminal epithelium gene expression. Compared with non-forage-supplemented calves, the molar proportions of valerate was lower (P < 0.05) in the rumen fluid of the calves fed forage on d 74 of the study, which might be associated with improved growth of cellulolytic bacteria (Castells et al., 2013). Cline et al. (1958) described a positive relationship between numbers of cellulolytic rumen microbes and the rate of valerate utilization in the rumen. Similarly, previous studies (Terré et al., 2013; Castells et al., 2013) have shown a decrease in rumen valerate molar proportions of calves supplemented with forage.

Blood Metabolites and Hematological Parameters

The data for blood metabolites and hematological parameters are presented in Table 5. No differences were observed in blood glucose concentration during the preweaning period across the treatments. However, the interaction of milk feeding method and forage provision tended (0.06) to be significant for the blood concentration of glucose, with the highest concentration for STP-NF treatment on d 74 of the study. The higher blood glucose concentration in calves fed STP-NF compared with other treatments may be explained by less solid feed consumption during the postweaning periods. In dairy calves, the primary source of energetic substrate is glucose derived from intestinal absorption (Khan et al., 2007b), but with the initiation of solid feed consumption, ruminal fermentation proceeds and VFA starts replacing glucose as the energy source (Baldwin et al., 2004). Glucose data for forage effect in the current study is consistent with the results of Terré et al. (2013), who observed similar serum glucose concentrations between calves supplemented and not supplemented with forage. Similarly, Silper et al. (2014) reported that milk replacer feeding strategy did not affect blood glucose concentration in dairy calves.


View Full Table | Close Full ViewTable 5.

Average blood metabolites concentrations and hematological parameters1 of Holstein male calves fed milk through either the conventional or the step-down method with or without forage provision

 
Treatment2
P-value3
Item COV-NF COV-F STP-NF STP-F SEM MMF FOR MMF × FOR
Glucose, mg/dL
    d 35 95.1 103.1 94.3 95.0 3.59 0.19 0.20 0.28
    d 74 81.87 88.62 92.62 87.43 3.11 0.13 0.80 0.06
Total protein, g/dL
    d 35 5.46ab 5.70a 5.31b 5.73a 0.15 0.70 0.03 0.55
    d 74 6.98 7.05 6.96 6.48 0.37 0.43 0.59 0.46
Albumin, g/dL
    d 35 2.95 2.63 2.70 2.70 0.18 0.60 0.37 0.37
    d 74 3.19ab 3.41a 2.87b 2.96b 0.14 0.01 0.29 0.66
Globulin, g/dL
    d 35 2.50b 3.06a 2.60b 3.03a 0.19 0.83 0.01 0.71
    d 74 3.78 3.64 3.89 3.52 0.34 0.98 0.47 0.74
BUN,4 mg/dL
    d 35 9.63 10.50 9.00 9.38 0.68 0.21 0.37 0.71
    d 74 14.54 16.47 15.21 14.68 0.72 0.44 0.33 0.09
RBC,4 ×10–6/μL 8.57 9.00 8.55 8.24 0.21 0.07 0.77 0.08
WBC,4 ×10–3/μL 8.54 8.58 10.51 9.27 0.73 0.08 0.42 0.39
Monocytes, 103/mm 0.59b 0.66ab 0.81a 0.85a 0.09 0.02 0.54 0.90
Lymphocytes, 103/mm 3.79ab 3.59b 4.48a 4.24ab 0.35 0.05 0.53 0.95
Neutrophils, 103/mm 3.73 4.12 5.17 3.96 0.53 0.28 0.74 0.14
Hb,4 g/dL 10.72 11.50 10.52 10.37 0.56 0.24 0.58 0.41
MCHC,4 g/dL cells 33.97 34.42 34.11 34.76 1.59 0.88 0.73 0.95
HCT,4 % 31.60 33.31 31.08 29.98 1.21 0.12 0.80 0.25
Platelets, × 103/μL 533.0 548.4 526.4 567.6 55.7 0.91 0.61 0.81
a,bMeans within a row with different superscripts letters are significantly different (P < 0.05).
1Haematological parameters were measured on d 61 of age.
2COV-NF = conventional milk feeding without forage provision; STP-NF = step-down milk feeding without forage provision; COV-F = conventional milk feeding with forage provision; STP-F = step-down milk feeding with forage provision.
3MMF = method of milk feeding; FOR = effect of forage provision; MMF × FOR = interaction between method of milk feeding and forage provision.
4BUN = blood urea nitrogen; RBC = red blood cells; WBC = white blood cells; Hb = hemoglobin; MCHC = mean corpuscular hemoglobin concentration; HCT = hematocrit.

As expected, no change in blood total protein and globulin concentrations was observed when the same quantity of milk was fed to dairy calves for both milk feeding methods. This is in line with the results of Khan et al. (2007a), who did not find differences in blood total protein concentration of calves fed milk through STP and COV methods. Blood total protein (P < 0.05) and globulin (P < 0.05) concentrations were greater in forage-supplemented calves than in non-forage-supplemented calves on d 35, but they were not changed among treatment on d 74 of age. In the current study, higher blood total protein content in forage-supplemented calves compared with the non-forage-supplemented calves may be associated with higher starter intake and the better health status of calves during the preweaning period.

In the current study, the calves fed the STP method had a lower (P < 0.01) blood albumin concentration than those conventionally fed. This decrease in blood albumin concentration could be due to changes in liver synthesis of protein, vascular leakage with increased vascular permeability, and increased catabolism of protein (Kim et al., 2003; Orhue et al., 2005). Increased vascular permeability might also explain the greater number of monocytes and lymphocytes in calves fed milk through the STP method. No differences were observed in blood urea nitrogen concentrations during the pre- or postweaning period across the treatments.

Hematological parameters did not change with the milk feeding method or forage provision in diet. Calves fed the STP method had greater numbers of monocytes (P < 0.05) and lymphocytes (P < 0.05) than those conventionally fed on d 61 of the study. We are not aware of any biologically relevant explanation for these significantly decreased numbers of lymphocytes and monocytes in COV milk feeding. Further study is needed to detect the effect of milk feeding procedure on hematological variables.

Conclusions

In summary, no interaction between milk feeding methods (STP or COV) and alfalfa provision (15% DM) with respect to calf performance and body measurements was detected in this study. Providing the same and a restricted quantity of milk through COV and STP methods was found to have no effects on performance of young calves throughout the experimental period. Regardless of milk feeding method, provision of mix of forage and finely processed starter changes the rumen fermentation parameters in dairy calves. Including 15% AH in the starter diets improved the final BW, starter intake, total DMI, and ADG in young calves.

 

References

Footnotes


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