Effects of the Feeding Rate of High Protein Calf Milk Replacers

The Professional Animal Scientist 23 (2007):649–655

Effects of the Feeding Rate of High Protein Calf Milk Replacers T. M. Hill,1 H. G. Bateman II, J. M. Aldrich, PAS, and R. L. Schlotterbeck Akey, Nutrition and Research Center, Lewisburg, OH 45338

ABSTRACT Weaning and postweaning reductions in ADG in calves fed large amounts of milk or milk replacers (MR) are common. The purpose of these trials was to determine the effect of feeding a high CP MR at different rates on ADG, starter intake, and efficiency. In trial 1, a 26% CP, 17% fat MR was fed at either 0.681 kg/ d (P681), and then stepped up to 0.794 kg/d by d 8 (P794), or stepped up to 0.908 kg/d by d 15 (P908). In trial 2, P681 and P908 were fed. In trial 3, calves were fed either P681, 26% CP, 17% fat MR stepped up to 1.135 kg/d by d 22 (P1135), 28% CP, 20% fat MR stepped up to 1.135 kg/d by d 22 (PF1135), or conventional 20% CP, 20% fat MR at 0.454 kg/d (C454). Calves fed P794, P908, P1135, and PF1135 had faster ADG from 0 to 21 d and less starter intake from 0 to 56 d compared with calves fed P681 (P < 0.05); however, ADG from 0 to 56 d did not differ. In trials 2 and 3, efficiency for 0 to 21 d was better in calves fed P908, P1135, and PF1135, but worse vs. P681 (P < 0.05) after d 42. The ADG of calves fed P681 was faster than calves fed C454 (P < 0.05), but starter intake did not differ. The maximum amount of a high CP MR that could be fed without creating a weaning and postweaning slump in performance was 0.681 kg/d. Key words: calf, milk replacer, intake

1

Corresponding author: [email protected]

INTRODUCTION Weaning and postweaning reductions in ADG have been reported in many peer-reviewed trials where large amounts of milk or milk replacers (MR) were fed to calves (Bar-Peled et al., 1997; Jasper and Weary, 2002; Cowles et al., 2006; Hill et al., 2006a). These reductions in ADG have been associated with less starter intake and poor feed efficiencies (Strzetelski et al., 2001; Jasper and Weary, 2002; Cowles et al., 2006; Hill et al., 2006a) and may be because of decreased digestion of the starter by postweaned calves fed large amounts of liquid (Terre et al., 2007). Currently, Hill et al. (2006b) is the only peer-reviewed trial to report improved ADG from a high feeding rate, high protein MR without depressing starter intake compared with feeding 0.454 kg/d of a conventional 20% CP, 20% fat MR. They fed 0.681 kg/d of a 26% CP, 17% fat MR, which is a much lower rate of MR or milk solids than fed in many high feeding rate trials (BarPeled et al., 1997; Strzetelski et al., 2001; Jasper and Weary, 2002; Cowles et al., 2006; Hill et al., 2006a). Tikofsky et al. (2001) suggested that feeding approximately 1 kg of a 23.5% CP, 14.7% fat MR (with no starter fed) was optimum in Holstein calves. Feeding more fat resulted in more fat deposition but similar protein deposition. Similar results were reported by Bascom (2002) in Jersey calves not fed starter. Feeding excessive milk or MR has been repeatedly shown to create

weaning and postweaning reductions in calf performance. However, there are limited data available to determine maximum feeding rate of a high protein MR that will not create a weaning and postweaning slump. Thus, the purpose of these 3 trials was to determine the effect of feeding a 26% CP, 17% fat MR at different rates on ADG, starter intake, and efficiency of gain of dairy calves.

MATERIALS AND METHODS In each trial, single source Holstein calves initially (d 0) 3 to 4 d old were weaned by d 42. A 26% CP, 17% fat MR fed at 0.681 kg powder/d was selected as the base treatment (MR program A) because this composition and rate has been shown to improve ADG over a conventional 20% CP, 20% fat MR while not depressing starter intake or postweaning gain (Hill et al., 2006b). An 18% CP starter was fed based on data of Stamey et al. (2005a,b) and Hill et al. (2007) showing that 18% CP was correct for calves receiving both conventional and high protein, high feeding rate MR. The starter was a complete pellet in trials 1 and 2, and textured (rolled corn, whole oats, protein pellet, and molasses) in trial 3. In the 3 trials, 6 different MR programs were fed; however no trial fed all 6 MR programs. The MR program abbreviations were kept constant across trials (i.e., MR programs P681 and P908 were the same in trials 1 and 2). In trial 1, a 26% CP, 17% fat MR powder was fed at either 0.681 kg/d

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(P681), and then stepped up to 0.794 kg/d by d 8 (P794), or stepped up to 0.908 kg/d by d 15 (P908). The rate of P681 was constant from d 1 to 39 and was divided into 2 equal meals. Calves fed P794 were fed 0.681 kg MR/d on d 1 to 7 and 0.794 kg MR/d on d 8 to 39 divided into 2 equal meals. Calves fed P908 were fed 0.681 kg MR/d on d 1 to 7, 0.794 kg MR/d on d 8 to 14, and 0.908 kg MR/d on d 15 to 39 divided into 2 equal meals. On d 40 to 42, calves were only fed MR in the a.m. (0.340, 0.397, and 0.454 kg MR/d for P681, P794, and P908, respectively). Measurements were made through d 56 when the trial ended. This trial was conducted January through March. The average nursery temperature was −7°C with weekly averages ranging from −9 to −5°C based on hourly measurements. In trial 2, a 26% CP, 17% fat MR powder was fed at either 0.681 kg/d (P681) or stepped up to 0.908 kg/d by d 15 (P908). Calves fed P681 and P908 were fed according to the schedule in trial 1. Measurements were made through d 56 when the trial ended. The average nursery temperature was 9°C with weekly averages ranging from 7 to 12°C based on hourly measurements. In trial 3, calves were fed either a 26% CP, 17% fat MR powder at 0.681 kg/d (P681), a 26% CP, 17% fat MR powder stepped up to 1.135 kg/d

by d 22 (P1135), a 28% CP, 20% fat MR powder stepped up to 1.135 kg/d by d 22 (PF1135), or a conventional 20% CP, 20% fat MR powder at 0.454 kg/d (C454). Calves fed P681 were fed according to the schedule in trial 1. Calves fed P1135 and PF1135 were fed 0.681 kg MR/d on d 1 to 7, 0.817 kg MR/d on d 8 to 14, 0.999 kg/d on d 15 to 21, and 1.135 kg/d on d 22 to 35, divided into 2 equal meals. On d 36 to 42, calves fed P1135 and PF1135 were only fed in the a.m. (0.567 kg/d). Calves fed C454 were fed 0.454 kg MR/d on d 1 to 39, divided into 2 equal meals. On d 40 to 42 calves fed C454 were fed only in the a.m. (0.227 kg MR/d). At d 56, calves were moved from individual to group pens. Measurements were made through d 84 when the trial ended. The average nursery temperature (0 to 56 d) was 9°C with weekly averages ranging from 1 to 16°C based on hourly measurements. The average group pen (56 to 84 d) temperature was 13°C with weekly averages ranging from 3 to 18°C based on hourly measurements. Ingredient compositions of the MR and starter have been previously reported (Hill et al., 2006b, 2007). The feeds were tested (AOAC, 1996) for DM, CP, fat, Ca, and P and results are reported in Table 1. The reconstituted MR for P681, P794, P908, P1135, and PF1135 were 148 g of powder diluted into a volume of 1 L with warm wa-

ter. The reconstituted MR for C454 was 120 g of powder diluted into a volume of 1 L with warm water. No calf rejected any MR. Holstein bull calves from a single dairy were received midday at 2 to 3 d of age after a 3-h transit. Their first MR was fed at the p.m. feeding. The day after arrival at approximately noon, the calves were weighed, blood was sampled intravenously for serum protein, which was determined via a refractometer (ATAGO US Inc., Bellevue, WA), and animals were randomly assigned to treatment (d 0, initial BW). Calves were weighed initially and weekly thereafter midway between a.m. and p.m. feedings. Dry starter feed was offered initially on d 3 and refused feed and new feed were weighed daily. Fecal scores were assigned daily based on a 1 to 5 system (1 being normal, thick in consistency; 2 being normal, but less thick; 3 being abnormally thin but not watery; 4 being watery; 5 being watery with abnormal coloring). Body condition and hip widths (with a caliper) were recorded at time of initially weighing and at 2, 4, 6, and 8 wk thereafter. Body condition score was based on a 1 to 5 system using 0.25 unit increments with 1 being emaciated and 5 being obese (Wildman et al., 1982). Scores were based on changes around the vertical and transverse processes of the spine as palpated by one expe-

Table 1. Analyzed nutrient content (as-fed basis) of milk replacers1 and starters (S) Trial 1

Trial 2

Trial 3

Nutrient, %

P681

P794

P908

S

P681

P908

S

P681

P1135

PF1135

C454

S

Moisture CP Fat Ash Ca P

3.2 26.0 17.1 5.6 0.80 0.63

3.3 26.3 17.1 5.5 0.82 0.60

3.2 26.1 17.1 5.5 0.83 0.61

12.3 18.3 3.2 5.9 0.75 0.51

3.3 26.2 17.2 5.7 0.79 0.61

3.2 26.1 17.0 5.6 0.78 0.59

13.3 18.0 3.4 6.3 0.85 0.52

3.3 26.2 17.1 5.4 0.79 0.60

3.3 26.1 17.0 5.3 0.80 0.61

3.4 28.3 20.2 5.0 0.75 0.61

3.1 20.2 20.1 6.4 0.79 0.61

13.0 18.3 3.6 6.1 0.77 0.63

1

P681 = a 26% CP, 17% fat MR powder fed at 0.681 kg/d; P794 = a 26% CP, 17% fat MR powder stepped up to 0.794 kg/d by d 8; P908 = a 26% CP, 17% fat MR powder stepped up to 0.908 kg/d by d 15; P1135 = a 26% CP, 17% fat MR powder stepped up to 1.135 kg/d by d 22; PF1135 = a 28% CP, 20% fat MR powder stepped up to 1.135 kg/d by d 22; and C454 = a conventional 20% CP, 20% fat MR powder at 0.454 kg/d.

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rienced technician and ranged from 1.5 to 3.5. Vaccines and medical treatments were based on the recommendations of a veterinarian and described in Hill et al. (2006a). From 0 to 56 d of each trial, calves were housed a curtain-sided, naturally-ventilated barn with no added heat in 1.2 by 2.4 m pens bedded with straw. In trial 3, from 56 to 84 d, calves were housed in group pens with 5.5 m2 of outside pen space and 0.9 m2 of inside pen space per calf. The inside pen space was bedded with straw and there was no added heat. Calves had access to clean, fresh water at all times. All animals were cared for by acceptable practices as described in the Guide for the Care and Use of Agricultural Animals in Agricultural Research and Teaching (FASS, 1999). Data from each trial were analyzed separately as completely randomized block designs using the GLM procedure of SAS (SAS Institute Inc., Cary, NC). Effects of block and diet were considered random and fixed effects, respectively. Starter intake, fecal score, and medical treatment data were first pooled by 7-d periods and then analyzed. Data are reported are least squares means for the experimental unit (calf) for d 1 to 56 in all trials. In trial 3, calves were grouped in pens (6 calves/pen) from d 56 to 84 and pen was the experimental unit. Calves were grouped according to their previous MR treatment. In trial 1, if the differences among treatments were significant (P < 0.05), orthogonal polynomial contrasts for linear and quadratic effects were conducted to further characterize differences. In trial 3, if the differences among treatments were significant (P < 0.05), polynomial contrasts for treatments C454 vs. P681, P1135, or PF1135, treatments P681 vs. P1135 or PF1135, and treatments P1135 vs. PF1135 were conducted to further characterize differences.

RESULTS AND DISCUSSION In trial 1, initial BW, hip width, BCS, and serum protein concentra-

Table 2. Least squares means for calves fed 26% CP, 17% fat milk replacers at 0.681 kg/d (P681) or stepped up to 0.794 (P794) and 0.908 kg/d (P908) in trial 1 (16 calves/mean) Item Initial BW, kg Initial serum protein, mg/dL BW gain, kg/d 0 to 21 d 0 to 42 d 42 to 56 d 0 to 56 d Milk replacer powder intake, kg/d 0 to 42 d Starter intake, kg/d 0 to 21 d 0 to 42 d 42 to 56 d 0 to 56 d G:F2 0 to 21 d 0 to 42 d 42 to 56 d 0 to 56 d BCS3 Initial 0 to 14 d change 0 to 42 d change 42 to 56 d change 0 to 56 d change Hip width, cm Initial 0 to 14 d change 0 to 42 d change 42 to 56 d change 0 to 56 d change

P608

P794

42.6 5.3

42.3 5.5

P908 42.3 5.5

SEM 1.0 0.5

Linear1 NS NS

0.468 0.613 1.071 0.727

0.516 0.574 1.072 0.698

0.538 0.561 1.076 0.690

0.022 0.021 0.044 0.018

0.05 NS NS NS

0.657

0.747

0.819

—

—

0.114 0.399 2.208 0.851

0.082 0.329 2.137 0.781

0.056 0.264 2.141 0.734

0.012 0.032 0.080 0.041

0.05 0.05 NS 0.05

0.588 0.581 0.485 0.543

0.604 0.550 0.506 0.532

0.595 0.531 0.507 0.520

0.031 0.016 0.014 0.010

NS 0.05 NS NS

2.2 0.1 0.4 0.2 0.6

2.3 0.2 0.4 0.2 0.6

2.4 0.3 0.4 0.2 0.2

0.04 0.03 0.04 0.04 0.09

NS 0.05 NS NS NS

17.6 0.3 3.0 1.5 4.5

17.7 0.4 3.0 1.3 4.3

17.6 0.5 2.7 1.3 4.0

0.21 0.11 0.22 0.14 0.27

NS NS NS NS NS

Value of 0.05 indicates the linear polynomial was significant at P < 0.05; NS indicates P > 0.05. 2 Gain divided by milk replacer plus starter. 3 Body condition score: 1 to 5 system with 1 = emaciated and 5 = obese. 1

tions did not differ (P > 0.05) among treatments (Table 2). Calf ADG increased linearly (P < 0.05) as MR increased during d 1 to 21. Calf ADG did not differ (P > 0.05) from 0 to 42, 42 to 56, or 0 to 56 d. Calf BCS change from d 0 to 14 increased linearly (P < 0.05) as MR increased. Starter intake for 0 to 42 d and 0 to 56 d and efficiency from 0 to 42 d declined linearly (P < 0.05) as MR increased. Other measures did not differ (P > 0.05). In trial 2, initial BW, hip width, BCS, and serum protein concentra-

tions did not differ (P > 0.05) among treatments (Table 3). Calves fed P681 had slower (P < 0.05) ADG from d 0 to 21 and d 0 to 42, but faster (P < 0.05) ADG from d 42 to 56 compared with calves fed P908. However, ADG from d 0 to 56 did not differ. Starter intake was greater (P < 0.05) for calves fed P681 than for calves fed P908 from d 0 to 42, d 42 to 56, and d 0 to 56. Calves fed P681 were less (P < 0.05) efficient from d 0 to 21 and d 0 to 42, but more efficient (P < 0.05) from d 42 to 56 compared with calves fed P908. However, efficiency

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Table 3. Least squares means for calves fed 26% CP, 17% fat milk replacers at 0.681 kg/d (P681) or stepped up to 0.908 kg/d (P908) in trial 2 (24 calves/mean) Item Initial BW, kg Initial serum protein, mg/dL BW gain, kg/d 0 to 21 d 0 to 42 d 42 to 56 d 0 to 56 d Milk replacer powder intake, kg/d 0 to 42 d Starter intake, kg/d 0 to 21 d 0 to 42 d 42 to 56 d 0 to 56 d G:F2 0 to 21 d 0 to 42 d 42 to 56 d 0 to 56 d Body condition score3 Initial 0 to 14 d change 0 to 42 d change 42 to 56 d change 0 to 56 d change Hip width, cm Initial 0 to 14 d change 0 to 42 d change 42 to 56 d change 0 to 56 d change

P681 41.2 5.5

P908 40.5 5.5

SEM 0.9 1.3

P > F1 NS NS

0.408 0.508 0.847 0.593

0.537 0.585 0.656 0.603

0.020 0.023 0.062 0.025

0.05 0.05 0.05 NS

0.657

0.819

—

—

0.068 0.273 1.727 0.636

0.050 0.220 1.553 0.553

0.012 0.027 0.088 0.040

NS 0.05 0.05 0.05

0.545 0.533 0.491 0.517

0.638 0.589 0.423 0.532

0.037 0.033 0.034 0.023

0.05 0.05 0.05 NS

2.3 0.2 0.5 0.2 0.7

2.2 0.4 0.6 0.1 0.7

0.06 0.05 0.05 0.04 0.05

NS 0.05 NS NS NS

17.2 0.4 2.6 1.3 3.9

17.7 0.4 2.8 1.2 4.0

0.26 0.12 0.14 0.13 0.14

NS NS NS NS NS

Value of 0.05 indicates P < 0.05; NS indicates P > 0.05. Gain divided by milk replacer plus starter. 3 Body condition score: 1 to 5 system with 1 = emaciated and 5 = obese. 1 2

from d 0 to 56 did not differ. Calves fed P681 had less (P < 0.05) BCS change from 0 to 28 and 0 to 42 d than calves fed P908. Other measures did not differ (P > 0.05). In trial 3, initial BW, hip width, BCS, and serum protein concentrations did not differ (P > 0.05) among treatments (Table 4). Calves fed C454 grew slower (P < 0.05) during d 1 to 21, d 1 to 42, and d 1 to 56, but faster (P < 0.05) for d 42 to 56 than calves fed P681, P1135, and PF1135. Calves fed P1135 and PF1135 grew the fastest (P < 0.05) and had the

greatest gain to feed efficiency (P < 0.05) during d 0 to 42 but grew the slowest (P < 0.05) and had the lowest (P < 0.05) efficiency during d 42 to 56 and d 56 to 84. The BW gain for 7-d weigh periods up to d 56 are plotted in Figure 1. The BW gain among calves fed P681, P1135, and PF1135 did not differ (P > 0.05) at d 56; however, at d 56 BW gain for calves fed C454 was less (P < 0.05) than for calves fed the other MR. Calves fed P1135 and PF1135 consumed the least (P < 0.05) amount of starter during d 1 to 42 and d 56 to 84. Calves

fed C454 had less (P < 0.05) hip width change during d 1 to 21, d 1 to 42, and d 1 to 56 than calves fed P681, P1135, and PF1135. Calves fed C454 had less (P < 0.05) BCS change during d 1 to 21, d 1 to 42, and d 1 to 56, but more (P < 0.05) for d 42 to 56 than calves fed P681, P1135, or PF1135. Calves fed PF135 had more (P < 0.05) abnormal fecal score days during d 0 to 21 than calves fed P1135 (1.0, 1.1, 1.3, and 2.2 d for C454, P681, P1135, and PF1135E, respectively). Other measures did not differ (P > 0.05). In each trial, calves fed P681 (26% CP, 17% fat MR fed at 0.681 kg/d) did not have different ADG from 0 to 56 d than calves MR at greater rates (P794, P908, P1135, and PF1135). Yet in all trials, calves fed P681 had slower ADG from 0 to 21 d than calves fed P794, P908, P1135, and PF1135. Additionally in trials 2 and 3, calves fed P681 had slower ADG from 0 to 42 d than calves fed P908, P1135, or PF1135 (Figure 1). As one would expect, calves fed P1135 and PF1135 gained more BW than calves fed P681 and C454 in the first few 7d periods; however, BW gained for calves fed P681, P908, and P1135 converged to not be different by d 56. This is explained by starter intake and efficiency of gain. In all trials, calves fed P681 consumed more starter from 0 to 56 d than calves fed P794, P908, P1135, and PF1135, although efficiency did not differ. Efficiency was greater from 42 to 56 d in calves fed P681 than in calves fed P908, P1135, and PF1135 in trials 2 and 3. Efficiency, intake, and ADG were greater from 56 to 84 d in calves fed P681 than in calves fed P908, P1135, and PF1135 in trial 3. It is interesting to note that in trial 1, when environmental temperatures were the coldest (average of −5°C or colder every week of the trial), ADG of calves fed P681 (the common treatment) did not appear to differ from calves fed P681 in trials 2 and 3 when environmental temperatures were considerably warmer. From 0 to 21 d, calves fed P681 in trial 1 had

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Table 4. Least squares means for calves fed different milk replacers1 at different rates in trial 3 (24 calves/ mean2) Contrast significance3 Item Milk replacer CP, % Milk replacer fat, % Initial BW, kg Initial serum protein, mg/dL BW gain, kg/d 0 to 21 d 0 to 42 d 42 to 56 d 0 to 56 d 56 to 84 d Milk replacer powder intake, kg/d 0 to 42 d Starter intake, kg/d 0 to 21 d 0 to 42 d 42 to 56 d 0 to 56 d 56 to 84 d Hay intake, kg/d 56 to 84 d G:F4 0 to 21 d 0 to 42 d 42 to 56 d 0 to 56 d 56 to 84 d BCS5 Initial 0 to 14 d change 0 to 42 d change 42 to 56 d change 0 to 56 d change 56 to 84 d change Hip width, cm Initial 0 to 14 d change 0 to 42 d change 42 to 56 d change 0 to 56 d change 56 to 84 d change 1

C454 20 20 44.2 5.0

P681 26 17 44.1 5.0

P1135

PF1135

SEM

26 17 44.1 4.8

28 20 43.9 5.1

— — 0.9 0.2

C454 vs. others

P681 vs. P1135, PF1135

P1135 vs. PF1135

— — NS NS

— — NS NS

— — NS NS

0.154 0.409 1.109 0.583 1.039

0.406 0.607 1.036 0.714 1.108

0.513 0.683 0.846 0.724 1.004

0.551 0.715 0.902 0.714 0.959

0.031 0.023 0.053 0.025 0.026

0.05 0.05 0.05 0.05 NS

0.05 0.05 0.05 NS 0.05

NS NS NS NS 0.05

0.438

0.657

0.888

0.888

—

—

—

—

0.104 0.397 2.129 0.830 2.792

0.090 0.380 2.154 0.824 2.960

0.061 0.218 1.947 0.650 2.840

0.059 0.227 2.098 0.695 2.729

0.011 0.033 0.085 0.044 0.057

0.05 0.05 NS 0.05 NS

0.05 0.05 NS 0.05 0.05

NS NS NS NS NS

0.119

0.126

0.121

0.116

0.002

NS

0.05

NS

0.255 0.437 0.527 0.506 0.357

0.523 0.590 0.486 0.546 0.360

0.573 0.615 0.426 0.548 0.340

0.619 0.642 0.428 0.560 0.337

0.037 0.015 0.019 0.012 0.008

0.05 0.05 0.05 0.05 NS

0.05 0.05 0.05 NS 0.05

NS NS NS NS NS

2.2 −0.1 0.2 0.1 0.3 0.2

2.2 0.1 0.5 0.0 0.6 0.2

2.3 0.1 0.6 0.0 0.7 0.2

2.3 0.1 0.6 0.0 0.7 0.1

0.04 0.04 0.05 0.05 0.04 0.04

NS 0.05 0.05 NS 0.05 NS

NS NS NS NS NS NS

NS NS NS NS NS NS

17.3 0.2 2.3 1.7 4.0 2.8

17.4 0.7 3.3 1.5 4.8 3.1

18.3 0.7 3.3 1.1 4.4 2.8

18.1 0.5 3.3 1.1 4.4 2.6

0.19 0.12 0.15 0.15 0.21 0.14

NS 0.05 0.05 0.05 0.05 NS

NS NS NS 0.05 NS 0.05

NS NS NS NS NS NS

C454 = a conventional 20% CP, 20% fat MR powder at 0.454 kg/d; P681 = a 26% CP, 17% fat MR powder at 0.681 kg/d; P1135 = a 26% CP, 17% fat MR powder stepped up to 1.135 kg/d by d 22; and PF1135 = a 28% CP, 20% fat MR powder stepped up to 1.135 kg/d by d 22. 2 All data are based on 24 calves/mean with calf as the experimental unit except 56 to 84 d data, which are based on 4 pens/ mean (6 calves/pen) with pen as the experimental unit. 3 Value of 0.05 indicates the polynomial contrast was significant at P < 0.05; NS indicates P > 0.05. 4 Gain divided by milk replacer plus starter. 5 Body condition score: 1 to 5 system with 1 = emaciated and 5 = obese.

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Figure 1. Body weight gain of calves fed a 26% CP, 17% fat MR powder at 0.681 kg/d (䊉 with solid line; P681), a 28% CP, 20% fat MR powder stepped up to 1.135 kg/d by d 22 (䊐 with dashed line; PF1135), a 26% CP, 17% fat MR powder stepped up to 1.135 kg/d by d 22 (䊏 with solid line; P1135), or a conventional 20% CP, 20% fat MR powder at 0.454 kg/d (䊊 with dashed line; C454) in trial 3. Body weight gain among calves fed P681, P1135, and PF1135 did not differ (P > 0.05) at d 56; however, at d 56 BW gain for calves fed C454 was less (P < 0.05) than calves fed the other MR. The SEM for BW gain for d 7, 14, 21, 28, 35, 42, 49, and 56 was 0.2, 0.3, 0.4, 0.6, 0.7, 0.9, 1.2, and 1.3 kg, respectively.

ADG of 0.468 kg/d compared with 0.408 and 0.406 kg/d in trials 2 and 3. From 0 to 21 d, calves fed P908 had ADG of 0.538 kg/d in trial 1 and 0.537 kg/d in trial 2. Additionally and also confounded with trial, calves were fed a completely pelleted starter in trials 1 and 2 and a textured starter in trial 3, and the results across trials appeared similar to each other. The research of Bar-Peled et al. (1997) is frequently cited to support the idea of increased rate of MR feeding to increase the rate of gain of calves. In this study, calves fed ad libitum milk (suckle the dam) gained 0.85 kg/d from 0 to 6 wk preweaning compared with calves fed restricted MR that only gained 0.56 kg/d. However, from 6 to 12 wk postweaning, the ad libitum-fed group only gained 0.35 kg/d compared with the restricted-fed group gaining 0.86 kg/d. Thus, the ad libitum-fed group gained 0.60 kg/d and the restricted group gained 0.71 kg/d from 0 to 12 wk. Dry feed (starter) intake was not reported. Jasper and Weary (2002) fed whole Holstein milk at 4.9 kg (restricted amount by bucket) and 8.8

kg (ad libitum; nursed the cow) of liquid daily for 36 d and reported extremely low dry feed intakes of 0.2 and 0.1 kg/d, respectively. Dry feed intakes during the 5-d weaning period were 1.0 and 0.75 kg/d, and 1.94 and 2.01 kg/d for the 20-d postweaning period for calves fed restricted or ad libitum milk, respectively. Total BW gain was 17.3 and 28.1 kg preweaning, 2.7 and 1.8 kg during weaning, and 17.0 and 13.6 kg postweaning for the low- and high milk-fed groups. Strzetelski et al. (2001) fed either 1.0 or 1.6 kg of a 22% CP, 17% fat MR and reported 0.41 and 0.34 kg daily of dry feed intake in the 49-d preweaning period and 2.52 and 2.65 kg daily dry feed intake in the 63-d postweaning period, respectively. Total gains were 20.0 kg preweaning and 81.5 kg postweaning for the low MR group and 37.7 kg preweaning and 81.2 kg postweaning for the high MR group. Calves fed the greater level of liquid diet in both trials (Strzetelski et al., 2001; Jasper and Weary, 2002) appeared more efficient preweaning and less efficient postweaning. Similar reductions in ADG at weaning and lower starter intakes

have been reported by Cowles et al. (2006), Hill et al. (2006a), and Stamey et al. (2006) in calves fed high vs. low rates of MR and by Ito et al. (2006) in calves fed high vs. low rates of whole milk. Terre et al. (2007) fed approximately 1 and 0.5 kg/d of a 25% CP, 19% fat MR over 34 d and measured lower apparent DM (71.8 vs. 77.4%), OM (73.3 vs. 78.6%), NDF (20.3 vs. 34.7%), and CP (71.6 vs. 77.1%) digestibility in calves fed high vs. low rates of MR during the week postweaning. Calves fed the high rate of MR tended to be heavier at 42 d (87.9 vs. 82.0 kg) but had a lower starter intake (0.64 vs. 0.97 kg/d) from 0 to 42 d than calves fed the low rate of MR. Collectively, the data of Bar-Peled et al. (1997), Strzetelski et al., (2001), Jasper and Weary (2002), Cowles et al. (2006), Hill et al. (2006a), Ito et al. (2006), Terre et al. (2007), and trials 1, 2, and 3 are consistent and rather conclusive. Feeding too much milk or MR will result in a postweaning reduction in growth. In trials 1, 2, and 3, calves fed more than 0.681 kg/d of MR had reduced starter intake and this appears to be compromising the ability of that calf to gain BW postweaning. The digestive system of the calf fed high rates of MR or milk may not be as prepared to digest starter based on the reduced digestibility data of Terre et al. (2007). In summary, there was no improvement in ADG and starter intake was reduced from 0 to 56 d when 26 and 28% CP MR were fed at rates from 0.794 to 1.135 kg/d vs. the 26% CP, 17% fat MR fed at 0.681 kg/d. The 26% CP, 17% fat MR fed to calves at 0.681 kg/d did not reduce starter intake and increased the ADG of calves compared with calves fed a 20% CP, 20% fat MR at 0.454 kg/d. Approximately 0.681 kg/d is the upper limit to how much of a 26% CP, 17% fat MR that can be fed without creating a weaning and postweaning reduction in performance.

Feeding rate of high protein milk replacers

IMPLICATIONS As the feeding rates of high protein MR (26 or 28% CP) were increased above 0.681 kg/d, ADG was increased from 0 to 21 d, but starter intake from 0 to 56 d was decreased. From 0 to 56 d, ADG did not differ in calves fed high CP MR at 0.794 to 1.135 kg/ d vs. 0.681 kg/d. In trials 2 and 3, efficiency from 0 to 21 d was better in calves fed MR at rates over 0.681 kg/ d, but worse after d 42. The 26% CP, 17% fat MR fed to calves at 0.681 kg/ d did not reduce starter intake and increased the ADG of calves compared with calves fed at conventional 20% CP, 20% fat MR at 0.454 kg/d. Approximately 0.681 kg/d was the maximum amount of a high CP MR that could be fed without creating a weaning and postweaning reduction in performance.

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