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Dairy Technology Research Institute, Purchasing and Supplying Department, The National Federation of Dairy Co-operative Associations (ZEN-RAKU-REN), Nishi-shirakawa, Fukushima, Japan 969-0223
Dairy Technology Research Institute, Purchasing and Supplying Department, The National Federation of Dairy Co-operative Associations (ZEN-RAKU-REN), Nishi-shirakawa, Fukushima, Japan 969-0223
The objective of this study was to evaluate effects of partial replacement of dry ground corn with lactose in calf starters on dry matter intake, growth rate, ruminal pH, and volatile fatty acid profile. Sixty Holstein bull calves were raised on a high plane of nutrition program until 55 d of age. Calves were fed texturized calf starters containing 30.1% steam-flaked grains and lactose at 0 (control), 5, or 10% (n = 20 for each treatment) on a dry matter basis. All calves were fed treatment calf starters ad libitum from d 7 and kleingrass hay from d 35. Ruminal pH was measured continuously immediately after weaning (d 55–62) for 15 calves (n = 5 per treatment), and 3 wk after weaning (d 77 to 80) for the other 45 calves (n = 15 per treatment). Dry matter intake, growth performance, and ruminal pH variables were not affected by treatment. However, according to Spearman's correlation coefficient (rs) analyses, lactose intake was positively correlated with dairy minimum ruminal pH (rs = 0.306) for the data collected from d 77 to 80. Similarly, hay intake was not affected by treatment, but positively correlated with daily mean (rs = 0.338) and maximum ruminal pH (rs = 0.408) and negatively correlated with duration pH <5.8 (rs = −0.329) and area pH <5.8 (rs = −0.325), indicating that the variation in hay intake among animals might have masked treatment effects on ruminal pH. Ruminal molar ratio of acetate was higher (45.2 vs. 40.6%), and that of propionate was lower in 10% lactose than control (35.3 vs. 40.2%) for ruminal fluid collected on d 80; however, molar ratio of butyrate was not affected by treatment. These results indicate that lactose inclusion in calf starters up to 10% of dry matter might not affect dry matter intake and growth performance of calves, but that greater lactose and hay intake might be associated with higher ruminal pH.
Effects of supplementing concentrates differing in carbohydrate composition in veal calf diets: I. Animal performance and rumen fermentation characteristics.
Starch source evaluation in calf starter: II. Ruminal parameters, rumen development, nutrient digestibilities, and nitrogen utilization in Holstein calves.
Effects of supplementing concentrates differing in carbohydrate composition in veal calf diets: I. Animal performance and rumen fermentation characteristics.
). In addition, the low ruminal pH might be also attributed to underdeveloped ruminal epithelium of calves, where fermentation acid production exceeds the absorptive capacity of the ruminal wall (
Sugars versus starch as supplements to grass silage: Effects on ruminal fermentation and the supply of microbial protein to the small intestine, estimated from the urinary excretion of purine derivatives, in sheep.
); however, effects of feeding lactose on ruminal fermentation and animal performance have not been extensively studied for calves.
We hypothesized that lactose inclusion in calf starters would increase ruminal butyrate concentration, ruminal pH, starter intake, and growth performance of calves. The objective of our study was to evaluate effects of partial replacement of a starch source with lactose in calf starters on DMI and growth performance before and after weaning, as well as ruminal pH and VFA profiles after weaning.
MATERIALS AND METHODS
Animals and Housing
Sixty Holstein male calves (4–6 d of age, BW = 47.3 ± 0.7 kg; mean ± SD) were collected from commercial dairies in Fukushima and Ibaraki prefectures (Japan) and transported to the Dairy Technology Research Institute (Yabuki, Fukushima, Japan). Calves were born on March 20 to April 13, 2015 (group 1), and May 7 to June 2, 2015 (Group 2). Calves were further blocked by birthdate, BW, and farm origin, and randomly assigned to 1 of 3 calf starter treatments (n = 20 for each treatment). Calves were raised in individual hatches (made by fiber-reinforced plastics with wood grating floor) without bedding materials. When calves were arrived in the research farm, they received 5 mL of Terramycin (Zoetis Japan, Tokyo, Japan) and 0.1 mL of Duphafral Forte (Zoetis Japan) via subcutaneous injection and received 5 mL of Ivermec PO (Fujita Pharm, Tokyo, Japan) via percutaneous absorption. In addition, all calves received 5 mL of Ektecin Liquid (Meiji Seika Pharma, Tokyo, Japan) and 20 mL of Baycox Bovis (Bayer Yakuhin, Osaka, Japan) via oral administration on d 3 and 21 after arrival, respectively.
Feeding
All calves were fed a milk replacer (28% CP and 15% fat; 166.7 g/L) using a bucket with a soft rubber nipple twice daily at 0615 and 1615 h. Milk replacer was offered at 600 g/d until d 13, 800 g/d from d 14 to 20, and 1,200 g/d from d 21 to 41, 800 g/d from d 42 to 48, and 600 g/d from d 49 to 55; calves were then weaned on d 56. All calves had free access to fresh water supplied by a bucket with a soft rubber nipple. Calves were fed texturized calf starters containing 30.1% steam-flaked grains and lactose at 0 (control), 5.0 (LAC5), or 10.0% (LAC10) on a DM basis. All calf starters were formulated for 23.1% CP (Table 1). Treatment calf starters were offered ad libitum using an 8-L bucket from d 7. Feeding time of calf starters was 1000 h initially, but when calves consumed more than 900 g/d (as fed) of starter, calves were fed twice daily (1000 and 1500 h; equal volume of starter). Kleingrass hay was offered at 50 g/d (as fed) from d 42 to 48, 100 g/d (as fed) from d 49 to 55, and 150 g/d (as fed) after d 56. Refused calf starters and hay were cleaned daily at 1000 h and their intakes were recorded.
Table 1Dry matter ratio of ingredients on calf starter formulations
Treatment: Control = calf starter containing no lactose; LAC5 = calf starter containing 5% of lactose on a DM basis; LAC10 = calf starter containing 10% of lactose on a DM basis.
Lactose (Hilmar 5030 Extra Fine Grind Lactose, Hilmar Ingredients, Hilmar, CA).
0.0
5.0
10.0
1 Treatment: Control = calf starter containing no lactose; LAC5 = calf starter containing 5% of lactose on a DM basis; LAC10 = calf starter containing 10% of lactose on a DM basis.
2 Heated soybean (SoyPlus, West Central Cooperative, Ralston, IA).
3 GC mix 21 (trace mineral and vitamin premix, Zenrakuren, Tokyo, Japan), containing vitamin mix 16.0%, trace mineral mix 6.3%, and rice bran 77.7%.
4 Lactose (Hilmar 5030 Extra Fine Grind Lactose, Hilmar Ingredients, Hilmar, CA).
Body weight, withers height, hip height, horizontal body length, hip width, and heart girth were measured at the start of trial (d 7) and weekly thereafter until the end of trial (d 80). Fecal score (1–4 scales; 1 = normal fecal consistency to 4 = severe diarrhea) and diseases incidences, if any, were recorded daily. Blood was sampled from a jugular vein on d 7 after birth and serum was harvested. Ruminal pH was measured using Small Ruminal pH Data Loggers (SRL T-9, DASCOR, Escondido, CA) every 2 min from d 55 to 62, immediately after weaning, for 15 calves (n = 5 per treatment), and from d 77 to 80, 3 wk after weaning, for the other 45 calves (n = 15 per treatment), as described by
. All pH probes were calibrated at pH 4 and 7 before and after ruminal pH measurements. Mean, minimum, and maximum pH values as well as duration and area under pH 5.8 were calculated daily and averaged.
Fifteen calves (n = 5 per treatment) were euthanized on d 62, and the other 45 calves (n = 15 per treatment) were euthanized on d 80. After BW was measured, calves were anesthetized (subcutaneous injection of Selactar 2% injection solution at 1.5 mL/kg of BW; Bayer Yakuhin) and killed by exsanguination from the carotid artery. Ruminal fluid (50 mL) was sampled immediately after euthanization and frozen at −20°C until further analysis. Digestive organs were weighed and rumen papillae were sampled to determine expression of selected genes, and these data were reported elsewhere (
Treatment calf starters were sampled weekly, composited monthly, and stored at room temperature. The samples were ground using a hammer mill (SM1, Retsch GmbH, Haan Germany) with a 1-mm screen, and analyzed by Zen-Raku-Ren Analysis Center (Kamisu, Ibaraki, Japan) for concentrations of DM, ash, CP, ether extract, and starch according to
. Lactose content was analyzed by a commercial laboratory (Japan Food Research Laboratories, Tokyo, Japan) using HPLC (LC-20AD, Shimadzu, Kyoto, Japan) according to
. Serum samples were analyzed for IgG concentration by single radial immunodiffusion method using a commercial kit (Bovine IgG SRID assay kit LL-70002, Life laboratory, Yamagata, Japan). Ruminal VFA profile was analyzed using gas chromatography (GC-14B, Shimadzu) according to the method described by
All response variables except for ruminal pH and VFA profile were analyzed separately for 3 phases differing in primary nutrient sources; before weaning (d 7–41), during weaning transition (d 42–55), and after weaning (d 56–80). In addition, as calves were purchased at 2 different periods, group effect and group by treatment interaction were included then statistical model to account for possible confounding effects of different environment to which calves were exposed. Data were analyzed using JMP 12 (SAS Institute Inc., Cary, NC) according to the following model:
where Yijk is the dependent variable, µ is overall mean, Ti is fixed effect of treatment, Wj is the fixed effect of week used as a repeated measure, Gk is the fixed effect of group, TWij is the effect of treatment by week interaction, TGik is the effect of treatment by group interaction, Cov is the IgG concentration of serum samples collected on wk 1 used as covariate, and eijk is the residual. Treatment effects were declared significant at P < 0.05 and tendencies were declared at 0.05 ≤ P < 0.10.
Ruminal pH and VFA data were analyzed using JMP 12 (SAS Institute Inc.) according to the following model:
where Yijk is the dependent variable, µ is overall mean, Ti is fixed effect of treatment, Gk is the fixed effect of group, TGik is the effect of treatment by group interaction, Cov is the IgG concentration of plasma samples collected on wk 1 used as covariate, and eik is the residual. Treatment effects were declared significant at P < 0.05 and tendencies were declared at 0.05 ≤ P < 0.10. Correlations of ruminal pH variables to DMI, calf starter intake, hay intake, starch intake, and lactose intake were analyzed by Spearman's correlation method of JMP 12 (SAS Institute Inc.).
RESULTS
One calf in the LAC5 treatment had severe pneumonia and another calf in LAC10 treatment had severe arthritis, these calves were excluded from statistical analysis. Furthermore, ruminal pH data were missing for 1 calf each for the control and LAC10 treatments due to the failure of small ruminant ruminal pH-logger system.
Analyzed nutrient composition of calf starters is shown in Table 2. Starch concentration was 29.7, 28.1, and 21.9% and lactose concentration was 0, 3.0, and 7.2% for control, LAC5, and LAC10, on a DM basis, respectively. Analyzed lactose concentration was lower than formulated values possibly because of the Maillard reaction from the pelleting procedure.
Table 2Nutrient composition of treatment calf starters (mean ± SD)
Treatment: control = calf starter containing no lactose; LAC5 = calf starter containing 5% of lactose on a DM basis; LAC10 = calf starter containing 10% of lactose on a DM basis.
1 Treatment: control = calf starter containing no lactose; LAC5 = calf starter containing 5% of lactose on a DM basis; LAC10 = calf starter containing 10% of lactose on a DM basis.
Dry matter intake, starter intake, and hay intake were not affected by treatment (Table 3). Starch intake was lower for calves fed LAC5 and LAC10 than those fed control before weaning (32.2 and 30.0 vs. 46.0 g/d; P < 0.05) and during the weaning transition (174.4 and 168.8 vs. 231.5 g/d; P < 0.05), respectively. In addition, starch intake after weaning was different among all treatments (822.7, 739.1, and 616.5 g/d for control, LAC5, and LAC10, respectively; P < 0.05). Lactose intake was different among all treatment before weaning (0.0, 3.5, and 9.8 g/d for control, LAC5, and LAC10, respectively; P < 0.05), during weaning transition (0.0, 18.5, and 55.6 g/d for control, LAC5, and LAC10, respectively; P < 0.05), and after weaning (0.0, 78.4, and 201.6 g/d for control, LAC5, and LAC10, respectively; P < 0.05). Intake of NDF was higher in calves fed LAC10 than those fed control and LAC5 (544.2 vs. 505.4 and 487.1 g/d; P < 0.05) after weaning. Treatment did not affect ADG and other growth variables (Table 4); in addition, fecal score was not different among treatments (Table 5).
Table 3Effects of feeding calf starters differing in lactose content on feed and nutrient intakes before weaning (d 7–41), during weaning transition (d 42–55), and after weaning (d 56–80; LSM ± SEM)
Treatment: control = calf starter containing no lactose; LAC5 = calf starter containing 5% of lactose on a DM basis; LAC10 = calf starter containing 10% of lactose on a DM basis.
Means within a row differ (P < 0.05) if superscript letters differ.
0.01
a–c Means within a row differ (P < 0.05) if superscript letters differ.
1 Treatment: control = calf starter containing no lactose; LAC5 = calf starter containing 5% of lactose on a DM basis; LAC10 = calf starter containing 10% of lactose on a DM basis.
2 Total DMI is a sum of milk replacer, starter, and hay intakes.
Table 4Effects of feeding calf starters differing in lactose content on growth performance before weaning (d 7–41), during weaning transition (d 42–55), and after weaning (d 56–80; LSM ± SEM)
Treatment: control = calf starter containing no lactose; LAC5 = calf starter containing 5% of lactose on a DM basis; LAC10 = calf starter containing 10% of lactose on a DM basis.
P-value
Control (n = 15)
LAC5 (n = 14)
LAC10 (n = 14)
Before weaning (d 7–41)
ADG, kg/d
0.78 ± 0.042
0.73 ± 0.043
0.79 ± 0.043
0.50
Withers height gain, cm/d
0.24 ± 0.018
0.22 ± 0.018
0.24 ± 0.019
0.69
Hip height gain, cm/d
0.22 ± 0.025
0.24 ± 0.026
0.23 ± 0.025
0.94
Body length gain, cm/d
0.33 ± 0.028
0.25 ± 0.028
0.30 ± 0.029
0.11
Heart girth gain, cm/d
0.40 ± 0.037
0.38 ± 0.037
0.41 ± 0.038
0.80
Hip width gain, cm/d
0.09 ± 0.011
0.09 ± 0.011
0.09 ± 0.011
0.99
ADG/total DMI, kg/kg
0.67 ± 0.041
0.65 ± 0.041
0.69 ± 0.043
0.83
Weaning transition (d 42–55)
ADG, kg/d
0.74 ± 0.061
0.69 ± 0.065
0.86 ± 0.063
0.17
Withers height gain, cm/d
0.21 ± 0.028
0.26 ± 0.029
0.25 ± 0.029
0.52
Hip height gain, cm/d
0.27 ± 0.031
0.26 ± 0.020
0.26 ± 0.032
0.96
Body length gain, cm/d
0.23 ± 0.052
0.30 ± 0.052
0.27 ± 0.054
0.61
Heart girth gain, cm/d
0.31 ± 0.054
0.28 ± 0.056
0.36 ± 0.053
0.99
Hip width gain, cm/d
0.09 ± 0.017
0.08 ± 0.016
0.09 ± 0.017
0.92
ADG/total DMI, kg/kg
0.49 ± 0.034
0.52 ± 0.036
0.56 ± 0.035
0.35
After weaning (d 56–80)
ADG, kg/d
1.42 ± 0.071
1.38 ± 0.072
1.35 ± 0.075
0.79
Withers height gain, cm/d
0.27 ± 0.032
0.21 ± 0.033
0.24 ± 0.032
0.51
Hip height gain, cm/d
0.23 ± 0.040
0.20 ± 0.042
0.27 ± 0.040
0.50
Body length gain, cm/d
0.34 ± 0.062
0.37 ± 0.065
0.35 ± 0.065
0.93
Heart girth gain, cm/d
0.39 ± 0.087
0.44 ± 0.088
0.32 ± 0.091
0.62
Hip width gain, cm/d
0.14 ± 0.018
0.09 ± 0.018
0.15 ± 0.017
0.11
ADG/total DMI, kg/kg
0.54 ± 0.025
0.53 ± 0.026
0.49 ± 0.027
0.36
1 Treatment: control = calf starter containing no lactose; LAC5 = calf starter containing 5% of lactose on a DM basis; LAC10 = calf starter containing 10% of lactose on a DM basis.
Treatment: control = calf starter containing no lactose; LAC5 = calf starter containing 5% of lactose on a DM basis; LAC10 = calf starter containing 10% of lactose on a DM basis.
P value
Control (n = 15)
LAC5 (n = 14)
LAC10 (n = 14)
Before weaning (d 7–41)
1.7 ± 0.06
1.6 ± 0.07
1.8 ± 0.07
0.11
Weaning transition (d 42–55)
1.3 ± 0.05
1.2 ± 0.06
1.3 ± 0.05
0.20
After weaning (d 56–80)
1.3 ± 0.13
1.3 ± 0.13
1.3 ± 0.14
0.56
1 Fecal score: 1 = normal fecal consistency to 4 = severe diarrhea.
2 Treatment: control = calf starter containing no lactose; LAC5 = calf starter containing 5% of lactose on a DM basis; LAC10 = calf starter containing 10% of lactose on a DM basis.
Ruminal pH immediately after weaning or 3 wk after weaning were not affected by treatment (Table 6); however, lactose intake was positively correlated (P < 0.05) to daily minimum ruminal pH [Spearman's correlation coefficient (rs) = 0.306] and tended to be negatively correlated (P < 0.10) with area pH <5.8 (rs = −0.268) at 3 wk after weaning (Table 7). In addition, hay intake was positively correlated (P < 0.05) to daily mean pH (rs = 0.408) and maximum ruminal pH (rs = 0.338), and negatively correlated (P < 0.05) to duration pH <5.8 (rs = −0.329) and area pH <5.8 (rs = −0.325) at 3 wk after weaning.
Table 6Effects of feeding calf starters differing in lactose content on ruminal pH of calves immediately after weaning (d 55–62) and 3 wk after weaning (d 77–80; LSM ± SEM)
Treatment: control (n = 5 and 14 immediately and 3 wk after weaning, respectively) = calf starter containing no lactose; LAC5 (n = 5 and 14 immediately and 3 wk after weaning, respectively) calf starter containing 5% of lactose on a DM basis; LAC10 (n = 4 and 14 immediately and 3 wk after weaning, respectively) = calf starter containing 10% of lactose on a DM basis.
Area under the curve was calculated by multiplying the time ruminal pH was below 5.8 by pH units below pH 5.8 at each measurement point.
pH × min/d
460 ± 102.8
451 ± 110.7
349 ± 106.7
0.48
Daily SD
0.21 ± 0.030
0.23 ± 0.029
0.19 ± 0.029
0.73
1 Treatment: control (n = 5 and 14 immediately and 3 wk after weaning, respectively) = calf starter containing no lactose; LAC5 (n = 5 and 14 immediately and 3 wk after weaning, respectively) calf starter containing 5% of lactose on a DM basis; LAC10 (n = 4 and 14 immediately and 3 wk after weaning, respectively) = calf starter containing 10% of lactose on a DM basis.
2 Some pH data were missing due to pH system failures.
3 pH was measured every 2 min. If ruminal pH was below pH 5.8, ruminal pH was considered to be below pH 5.8 for the following 2 min.
4 Area under the curve was calculated by multiplying the time ruminal pH was below 5.8 by pH units below pH 5.8 at each measurement point.
Molar ratios of ruminal acetate, propionate, and butyrate were not affected by treatment at 1 wk after weaning (Table 8). However, calves fed LAC10 had higher molar ratio of acetate (45.2 vs. 40.6%; P < 0.05) and lower molar ratio of propionate (35.3 vs. 40.2%; P < 0.05) compared with those fed control at 3 wk after weaning. Consequently, acetate-to-propionate ratio was higher in calves fed LAC10 than those fed control (1.29 vs. 1.04; P < 0.05); however, the molar ratio of ruminal butyrate was not affected by treatment.
Table 8Effects of feeding calf starters differing in lactose content on ruminal VFA concentration and profile in calves 1 wk after weaning (d 62) and after 3 wk after weaning (d 80; LSM ± SEM)
Treatment: control (n = 5 and 15 immediately and 3 wk after weaning, respectively) = calf starter containing no lactose; LAC5 (n = 5 and 14 immediately and 3 wk after weaning, respectively) = calf starter containing 5% of lactose on a DM basis; LAC10 (n = 5 and 14 immediately and 3 wk after weaning, respectively) = calf starter containing 10% of lactose on a DM basis.
Means within a row differ (P < 0.05) if superscript letters differ.
<0.01
a–c Means within a row differ (P < 0.05) if superscript letters differ.
1 Treatment: control (n = 5 and 15 immediately and 3 wk after weaning, respectively) = calf starter containing no lactose; LAC5 (n = 5 and 14 immediately and 3 wk after weaning, respectively) = calf starter containing 5% of lactose on a DM basis; LAC10 (n = 5 and 14 immediately and 3 wk after weaning, respectively) = calf starter containing 10% of lactose on a DM basis.
Starch source evaluation in calf starter: II. Ruminal parameters, rumen development, nutrient digestibilities, and nitrogen utilization in Holstein calves.
). Therefore, we hypothesized that we would be able to increase calf starter intake and growth performance if we prevent SARA in calves. We had expected that partial replacement of corn grain with lactose in calf starters would increase ruminal pH of calves, as
Sugars versus starch as supplements to grass silage: Effects on ruminal fermentation and the supply of microbial protein to the small intestine, estimated from the urinary excretion of purine derivatives, in sheep.
reported that addition of lactose to a basal diet in sheep (silage only) resulted in higher ruminal pH compared with addition of other carbohydrates (lactose, xylose, starch, and fructose). Previous studies that evaluated effects of feeding lactose to mature cows (
Sugars versus starch as supplements to grass silage: Effects on ruminal fermentation and the supply of microbial protein to the small intestine, estimated from the urinary excretion of purine derivatives, in sheep.
) reported increased ruminal butyrate concentration. Because greater butyrate production in the rumen is expected to decrease proton production per unit of OM fermentation compared with production of acetate or propionate (
), we expected greater butyrate concentration in ruminal fluid to be associated with higher ruminal pH. However, we did not detect any treatment effects on ruminal butyrate concentration, ruminal pH, calf starter intake, and growth performance. The lack of treatment effects on intake and growth performance can be attributed to similar ruminal pH among treatments.
Ruminal pH
Although ruminal pH was not affected by treatment in the current study, it is noteworthy that lactose intake was positively correlated with daily minimum ruminal pH, and tended to be negatively correlated with the severity of SARA indicated by area pH <5.8. We speculated that the variation in hay intake among calves, regardless of treatment, might have masked possible positive effects of lactose on ruminal pH. Numerous studies reported that hay intake increased ruminal pH of calves fed either pelleted or texturized starters (
Effects of dietary forage and calf starter on ruminal pH and transcriptomic adaptation of the rumen epithelium in Holstein calves during the weaning transition.
). We tried to minimize confounding effects of variable hay intake on treatment effects by limiting hay intake to 150 g/d; however, a small difference in hay intake can exert large effects on ruminal pH.
reported that postweaning calves consuming a pelleted starter with 81.5 g/d of oat hay had higher ruminal pH than those consumed no hay. In the current study, hay intake of calves varied from 0 to 139.4 g/d and was positively correlated with dairy mean and maximum ruminal pH and negatively correlated with duration pH <5.8 and area pH <5.8 at 3 wk after weaning.
reported that decreasing starch content of texturized calf starters, containing 29.6% flaked grains on a DM basis, did not prevent SARA, whereas hay intake was positively correlated with mean ruminal pH. Therefore, hay intake may influence ruminal fermentation to a greater extent than carbohydrate profiles or starch content of calf starters differing in their physical form.
The lack of treatment effects on ruminal pH might be also attributed to the feeding method of calf starters in the current study. We offered calf starters twice daily, and they were always available to calves. As such, calves did not have a large meal immediately after feeding (personal observation; data not shown), and the reduction in postprandial ruminal pH was less than 0.3 units (Figure 1). As the control calf starter did not cause severe SARA, treatment starters that partially replaced dietary starch with lactose might not have affected overall ruminal pH, although lactose intake was positively correlated with daily minimum ruminal pH. The lack of drastic reduction in postprandial ruminal pH in the current study is contrary to the report of
, calves were offered starters once daily, and its amount was restricted to 2.5 kg/d. Limit-feeding calf starters, to avoid excess fermentation in the rumen, may have induced slug-feeding and resulted in SARA (
). These results indicate that feeding methods and the consequent eating pattern of calves would exert substantial effects on ruminal pH, potentially masking effects of feeding calf starters differing in starch content.
Figure 1Effects of feeding calf starters differing in lactose content on diurnal changes in ruminal pH on d 77 to 80. Control = starter containing no lactose (dashed line; n = 13); LAC5 = starter containing 5% lactose on a DM basis (thin solid line; n = 14); LAC10 = starter containing 10% lactose on a DM basis (thick solid line; n = 14). Calves were fed treatment calf starters twice daily at 1000 and 1500 h, as incidated by arrows.
We had hypothesized that lactose inclusion in calf starters would increase ruminal butyrate concentration, but we did not observe treatment effects on butyrate concentration. Contrarily, the LAC10 treatment increased the molar ratio of acetate and decreased molar ratio of propionate in ruminal fluid, resulting in a higher acetate-to-propionate ratio compared with control at 3 wk after weaning. These results might be at least partially attributed to differences in NDF intake among treatments; NDF intake was greater for LAC10 compared with control partly due to the greater NDF content of LAC10 calf starter, although it was not intended. Our observation is consistent with
Effects of supplementing concentrates differing in carbohydrate composition in veal calf diets: I. Animal performance and rumen fermentation characteristics.
, who reported higher NDF intake was associated with greater acetate-to-propionate ratio.
Our finding that lactose inclusion in calf starters increased ruminal concentration of acetate, instead of butyrate, is contrary to previous research findings with mature cows (
). Responses to lactose feeding in calves might be different from those in mature cows. In general, forage intake is much higher in mature cows compared with calves (
The role of thermodynamics in the control of ruminal fermentation.
in: Sejrsen K. Hvelplund T. Nielsen M.O. Ruminant Physiology: Digestion, Metabolism and Impact of Nutrition on Gene Expression, Immunology and Stress. Wageningen Academic Publishers,
Wageningen, the Netherlands2008: 159-170
), accumulation of metabolic hydrogen in the rumen can be reduced. However, calves before or right after weaning consumed highly fermentable carbohydrates compared with mature cows (
The role of thermodynamics in the control of ruminal fermentation.
in: Sejrsen K. Hvelplund T. Nielsen M.O. Ruminant Physiology: Digestion, Metabolism and Impact of Nutrition on Gene Expression, Immunology and Stress. Wageningen Academic Publishers,
Wageningen, the Netherlands2008: 159-170
). As a consequence, ruminal hydrogen concentration might be low in the rumen of calves, and this could allow more acetate production, as it is favored at low metabolic hydrogen concentrations (
The role of thermodynamics in the control of ruminal fermentation.
in: Sejrsen K. Hvelplund T. Nielsen M.O. Ruminant Physiology: Digestion, Metabolism and Impact of Nutrition on Gene Expression, Immunology and Stress. Wageningen Academic Publishers,
Wageningen, the Netherlands2008: 159-170
) and is energetically more advantageous to ruminal microbes. However, we did not measure ruminal metabolic hydrogen concentration in the current study; further investigation is warranted to evaluate the speculations.
Although it is speculated that effects of lactose on ruminal VFA profile would differ between mature cows and calves, rapid fermentation of lactose along with fast absorption of butyrate should not be excluded as a possible reason explaining the lack of treatment effects on ruminal butyrate concentration. Absorption of butyrate can be stimulated at low ruminal pH; fractional absorption rate of butyrate was higher than acetate at pH 5.4 (
). In the current study, mean ruminal pH ranged from 5.42 to 5.69, which makes it possible to alter absorption rate of butyrate. In addition, it is reported that increasing ruminal infusion of VFA did not affect ruminal concentration of butyrate although it increased acetate concentration (Dijkstra et al., 1994;
). As such, butyrate concentration in ruminal fluid may not necessarily reflect butyrate production in the rumen, and it is possible to increase butyrate production in the rumen without affecting its concentration.
CONCLUSIONS
Lactose inclusion in calf starter up to 10% of DM did not affect ruminal pH, DMI, or growth performance. However, lactose intake was positively correlated with minimum ruminal pH, and we cannot exclude the possibility that partial replacement of dietary starch with lactose increases ruminal pH. It should be noted that hay intake, feeding method of calf starter, and feeding pattern of calves could exert substantial effects on ruminal pH in calves during the weaning transition, and these management factors require as much attention as nutrient composition of calf starters to avoid SARA in calves. In addition, we observed that lactose inclusion in calf starters increased acetate concentration in the rumen without affecting butyrate concentration. Effects of feeding lactose on ruminal VFA may be different between mature cows and calves depending on the basal diets that animals consume, and this requires further investigation.
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Starch source evaluation in calf starter: II. Ruminal parameters, rumen development, nutrient digestibilities, and nitrogen utilization in Holstein calves.
Effects of dietary forage and calf starter on ruminal pH and transcriptomic adaptation of the rumen epithelium in Holstein calves during the weaning transition.
Effects of supplementing concentrates differing in carbohydrate composition in veal calf diets: I. Animal performance and rumen fermentation characteristics.
The role of thermodynamics in the control of ruminal fermentation.
in: Sejrsen K. Hvelplund T. Nielsen M.O. Ruminant Physiology: Digestion, Metabolism and Impact of Nutrition on Gene Expression, Immunology and Stress. Wageningen Academic Publishers,
Wageningen, the Netherlands2008: 159-170
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