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Growth and reproductive performance of beef replacement heifers fed development diets containing soybean meal or wet distillers grains 1
The Professional Animal Scientist 28 (2012):300–305
©2012 American Registry of Professional Animal Scientists
Growth and reproductive performance of beef
replacement heifers fed development diets containing soybean meal or wet distillers grains1 J. R. Jaeger,*2 PAS, J. W. Waggoner,* PAS, K. C. Olson,† PAS, K. R. Harmoney,* and J. W. Bolte* *Western Kansas Agricultural Research Center, Kansas State University, Hays 67601; and †Department of Animal Sciences and Industry, Kansas State University, Manhattan 66506
ABSTRACT Our objective was to evaluate the effects of replacing soybean meal with wet distillers grains plus solubles (WDG) in beef heifer development diets on growth and reproductive performance. Weaned heifers (n = 172; initial BW 319 ± 2 kg; age 282 ± 1 d) were stratified by BW and age and assigned randomly to be fed development diets using soybean meal (CON) or WDG as the primary source of CP in the diet. Heifers were allotted equally to 8 pens, adapted to diets for 14 d, and fed for ad libitum intake for 94 d. Heifer BW was measured on d 28, 56, and 84 relative to the beginning of the experiment and at breeding; paired serum samples were collected at these times to define puberty status. After 94 d, treatments were combined in a native shortContribution no. 11-323-J from the Kansas Agricultural Experiment Station. 2 Corresponding author: [email protected] 1
grass rangeland pasture. Heifers from each treatment were exposed to ovulation synchronization and fixed-time AI 23 or 51 d after diets ended. Total DM delivered was 4,695 kg less (P < 0.01) for WDG (57,131 kg) than for CON (61,826 kg). Daily DMI by WDG (7.07 kg) was 0.58 kg less (P < 0.01) than that by CON (7.65 kg), resulting in greater (P < 0.01) ADG throughout the development period for CON heifers (0.47 kg/d) than for WDG heifers (0.32 kg/d). Proportion of pubertal heifers was greater (P < 0.01) for CON compared with WDG on d 28 and 56 but not on d 84 or at breeding (P > 0.10). Conception to fixed-time AI and overall pregnancy rates were not different (P > 0.60) between treatments. Under the conditions of our study, developing replacement heifer diets using WDG as the primary source of CP had negative temporal effects on growth performance and age at puberty; however, these effects were nullified when heifers were allowed to graze native range for at least 23 d before breeding.
Key words: beef heifer, puberty, wet distillers grains
INTRODUCTION Proper development of replacement heifers is necessary to ensure maximum lifetime productivity by reducing age at first parturition (Lesmeister et al., 1973). Development of heifers should also be achieved at minimal cost without sacrificing performance. Wet distillers grains plus solubles (WDG) are a common component of diets fed to growing and finishing beef cattle; WDG is used also as a winter protein supplement for beef heifers and cows because of the modest cost per unit of CP. During ethanol production, protein is concentrated 3-fold relative to corn (Klopfenstein et al., 2008); therefore, WDG typically replaces a portion of the grain and most of the protein in feedlot diets. Heifers are often developed on foragebased diets of modest quality; high-
Wet distillers grains for heifer development diets
Table 1. Ingredient and nutrient compositions of replacement beef heifer development diets containing either soybean meal (CON) or wet distillers grains plus solubles (WDG) as the primary dietary protein source Diet, DM basis Item Ingredient composition, % Sorghum hay, ground Sorghum grain, rolled Soybean meal WDG Vitamin-mineral premix Calcium carbonate Salt Nutrient analysis1 DM, % CP, % RDP,2 % of CP NEm,3 Mcal/kg NEg,3 Mcal/kg NDF, % ADF, % TDN,3 % Calcium, % Phosphorus, % Sulfur, %
CON
80.5 10.4 7.82 — 0.64 0.31 0.31 79.4 10.7 67.0 1.48 0.75 47.4 35.3 60.6 0.86 0.21 0.17
WDG
75.7 10.4 — 12.4 0.58 0.62 0.31 67.5 10.1 64.4 1.48 0.75 41.1 35.4 60.6 0.99 0.25 0.23
Analysis conducted by SDK Laboratories, Hutchinson, KS. Calculated from diet-formulation software (BRaNDS 07, Ames, IA). 3 Calculated according to NRC (2000). 1 2
protein feedstuffs and supplements that promote fiber digestion are a logical complement to diets of this type. Howlett and coworkers (2003) evaluated soybean meal, whole linted cottonseed, whole raw soybeans, or pelleted soyhulls as protein sources in isonitrogenous heifer development diets. They observed no differences in proportion of pubertal heifers at initiation of the breeding season or in first-service conception rates and concluded that, independent of protein source, performance responses of heifers were predictable based on known relationships between nutrient composition and animal performance. Ruminal degradability of CP in the feedstuffs evaluated by Howlett et al. (2003) was substantial; however, WDG protein has modest ruminal degradability (NRC, 2000). This may limit the functionality of WDG as a supplement for low-quality forage di-
ets. Based on these data, we hypothesized that the level of RDP provided by WDG would limit DMI of heifers consuming a low-quality forage-based diet. Therefore, our objective was to document the effects of replacing soybean meal with WDG in replacement heifer development diets on growth and reproductive performance.
MATERIALS AND METHODS Animals and Experimental Design All procedures involving the handling and care of animals used in our experiment were approved by the Kansas State University Institutional Animal Care and Use Committee (Protocol number 2799.3). Springborn crossbred beef heifers (n = 172; initial BW = 319 ± 2 kg, age = 282 ± 1 d) that were preconditioned,
301
weaned, and backgrounded for 60 d were stratified by BW and age. Heifers were then assigned randomly to development diets containing soybean meal (CON) or WDG as the primary source of protein (Table 1). Heifers were allotted randomly within treatment to 8 pens (4 pens/treatment) and adapted to assigned development diets for 14 d. Diets were formulated to be similar in CP and energy content (Table 1) and were fed for ad libitum intake for 94 d following the end of the adaptation period. Heifers were fed once daily at 0700 h, and bunks were evaluated each morning at 0630 h. If the previous day’s feed was consumed, total feed delivered was increased by approximately 2% of the previous day’s feed delivery. Bunks were managed using a slick or clean bunk-management method to minimize feed refusals (Pritchard and Bruns, 2003). On d 95, heifers were removed from treatment pens and combined in a single native shortgrass rangeland pasture. Prior to the experiment, it was hypothesized that the level of RDP provided by WDG would limit DMI and ultimately decrease heifer performance during the drylot development period compared with heifers fed the CON diet. Based on performance data collected during the drylot development period, an ad hoc decision was made to randomly allot equal proportions of heifers from each treatment to an early or late breeding group to ascertain the drylot performance effects on conception to fixedtime AI. The early breeding group was exposed to ovulation synchronization and bred via fixed-time AI 23 d after development diets were terminated. The late breeding group was exposed to ovulation synchronization and bred via fixed-time AI 51 d after development diets were terminated.
Data Collection Heifer BW was measured every 28 d during the development period (i.e., d 1 to 94) and immediately before fixedtime AI. A BCS (scale 1 to 9; 1 = extremely thin, 9 = obese; Wagner et
302 al., 1988) was assigned to each animal by 2 trained evaluators blinded to treatment immediately before fixedtime AI. Weekly diet samples were collected from each pen, composited by treatment, and immediately frozen. At the conclusion of the study, weekly composite samples were combined to create treatment-diet composites, which were submitted to a commercial laboratory for analysis (SDK Laboratories, Hutchinson, KS; DM, CP, NEm, NEg, NDF, ADF, TDN, Ca, P, and S).
Puberty Evaluation Paired blood samples, collected at 10-d intervals, were obtained from all heifers via jugular venipuncture every 28 d during the feeding period, 10 d before initiation of ovulation synchronization, and on the day ovulation synchronization was initiated. Samples were collected with 16 × 100 mm Vacutainer tubes and then immediately placed on ice, allowed to clot for 24 h at 4°C, and then centrifuged (1,500 × g) for 10 min at 4°C. Serum was decanted into 12 × 75 mm plastic tubes and immediately frozen (−20°C). Concentration of progesterone in serum was subsequently quantified by RIA (Skaggs et al., 1986). Intra- and interassay CV were 7.0 and 7.9%, respectively, and assay sensitivity was 0.019 ng/mL. When samples contained concentrations of progesterone ≥1 ng/mL, heifers were considered to have attained puberty and be estrous-cycling.
Synchronization and Breeding For each breeding group of heifers (inseminated 23 or 51 d after termination of treatment diets), ovulation was synchronized using the 7-d CO-Synch+CIDR protocol; heifers were inseminated by fixed-time AI 54 to 56 h after CIDR removal. Heifers were exposed to fertile bulls 10 d after fixed-time AI for the remaining 35 d of a 45-d breeding season. Conception to fixed-time AI was determined via ultrasound 35 d after insemination, and final pregnancy rate was deter-
Jaeger et al.
mined via rectal palpation 60 d after the end of the breeding season.
Statistical Analysis Heifer performance data during the feeding period were analyzed as a completely random design (PROC GLM; SAS Institute Inc., Cary, NC). The model included effects for treatment and pen. Pen was considered the experimental unit. Heifer performance data during the pasture phase were analyzed as a completely random design (PROC GLM; SAS Institute Inc.). The model included an effect for treatment only; animal was considered the experimental unit. Proportion of pubertal heifers, fixed-time AI pregnancy rates, and overall pregnancy rates were analyzed using logistic regression (PROC CATMOD; SAS Institute Inc.). The original model used to assess differences in fixed-time AI pregnancy rates and overall pregnancy rates included effects for treatment and breeding group. Breeding group effects and associated interactions were not significant (P > 0.10) and were removed from the final model. Least squares means for pregnancy rates were reported. Treatment differences in performance, proportion of pubertal heifers, fixed-time AI pregnancy rates, and overall pregnancy rates were discussed when P ≤ 0.05; tendencies were discussed when P > 0.05 and ≤0.10.
RESULTS AND DISCUSSION Chemical composition of treatment diets and calculated dietary energy values are presented in Table 1. Diets were verified to contain sufficient metabolizable protein to support maintenance and growth for the heifers in this study (model level 1; NRC, 2000). Treatment diets were fed ad libitum and formulated to contain similar concentrations of CP, NEm, and NEg. In spite of these conditions, heifers fed the development diet containing WDG consumed less feed than did heifers fed the development diet containing soybean meal. Total
DM delivered during the 94-d feeding period was numerically 4,694 kg less (P < 0.01) for heifers fed the WDG diet than for heifers fed the CON diet (data not shown). Likewise, average daily DMI by heifers fed the WDG diet was 0.58 kg/d less (P < 0.01) than that by heifers fed the CON diet (7.07 vs. 7.65, respectively; Table 2). This resulted in greater (P < 0.01) BW change and ADG during each 28-d period and throughout the development period for CON-fed heifers than for WDG-fed heifers (Table 2). Theoretically, the WDG diet may have been deficient in RDP relative to the CON diet. The assumed RDP values for WDG and soybean meal used during diet formulation were 48 and 66%, respectively (NRC, 2000). Our diet-formulation software (BRaNDS 07, Ames, IA) indicated that the RDP for the WDG and CON diets was 64.4 and 67.0% of total CP, respectively, (Table 1) and supplied 460 and 547 g/d of RDP, respectively. In contrast, Cao et al. (2009) indicated that the A fraction of WDG (with proportions of condensed distillers solubles ranging from 0 to 40%) averaged 29.5% of total CP. Using this value for ruminal degradability of CP from WDG, our calculated dietary RDP intakes would have been 379 and 547 g/d for WDG and CON diets, respectively. Lowquality forage sorghum hay (6.5% CP) composed the bulk of the diets used in our study. Köster et al. (1996) indicated that dietary RDP:digestible OM should equal 0.11 to 0.13 in diets based on low-quality, warm-season forages. In the case of our WDG diet, the value of the ratio was only 0.10, indicating that low RDP intake may have caused reduced intake and gain of the heifers fed the WDG diet. Bandyk et al. (2001) reported that diets adequate in metabolizable protein but deficient in RDP resulted in depressed low-quality forage OM intake. Likewise, Olson et al. (1999) found that adequate supplemental RDP increased intake and digestion of low-quality, warm-season forage. At the end of the developmentdiet feeding period, overall ADG was greater (P < 0.01) for heifers fed
Wet distillers grains for heifer development diets
Table 2. Growth performance of beef replacement heifers fed diets containing either soybean meal (CON) or wet distillers grains plus solubles (WDG) as the primary dietary protein source during a 94-d development period Treatment mean Item No. of pens No. of heifers Days on feed Growth performance Initial BW, kg Final BW, kg Total BW change, kg DMI, kg/d ADG d 1 to 28, kg ADG d 29 to 56, kg ADG d 57 to 84, kg Overall ADG, d 1 to 94, kg
CON
WDG
SE
P-value
4 85 94 323 367 44.0 7.65 0.62 0.30 0.83 0.47
4 86 94 327 357 30.4 7.07 0.37 0.10 0.40 0.32
— — —
— — —
CON than for heifers fed WDG. Likewise, final heifer BW also tended to be greater (P < 0.10) for CON than for WDG (Table 2). At the beginning of the pasture phase of the experiment, BW of heifers assigned to the early breeding averaged 366 kg for WDG and 358 kg for CON (P = 0.33). Body weight and BCS at breeding were not different (P
3.3 3.9 1.8 0.04 0.03 0.04 0.03 0.02
0.31 0.09 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01
≥ 0.73) between CON and WDG heifers in the early breeding group (Table 3). Conversely, WDG heifers lost an average of 0.19 kg/d during the pasture phase of the experiment, whereas CON heifers gained 0.15 kg/d (P = 0.01; Table 3). Heifer BW in the late breeding group averaged 351 kg for WDG and 374 kg for CON (P < 0.01) at the
Table 3. Growth performance of beef replacement heifers grazing native shortgrass rangeland pasture that were previously fed development diets containing either soybean meal (CON) or wet distillers grains plus solubles (WDG) as the primary dietary protein source Treatment mean Item Early breeding group1 Initial BW, kg BW at breeding, kg Prebreeding ADG, kg BCS2 at breeding Late breeding group3 Initial BW, kg BW at breeding, kg Prebreeding ADG, kg BCS2 at breeding
CON
358 361 0.15 5.78 374 387 0.25 6.14
WDG
366 362 −0.19 5.82 351 368 0.34 5.88
SE
4.1 3.8 0.07 0.05 3.7 3.3 0.03 0.04
P-value
0.33 0.92 0.01 0.73 <0.01 <0.01 0.12 <0.01
Heifers in the early breeding group were bred via fixed-time AI 23 d after treatment diets were terminated. 2 BCS scale: 1 to 9 (1 = emaciated, 9 = obese). 3 Heifers in the late breeding group were bred via fixed-time AI 51 d after treatment diets were terminated. 1
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beginning of the pasture phase of the experiment (Table 3). Body weight and BCS at breeding were less (P < 0.01) for WDG heifers than for CON heifers; however, heifers fed WDG achieved adequate prebreeding BW and BCS (Table 3) based on similar (P = 0.46) fixed-time AI pregnancy rates for the WDG and CON heifers (51.0 vs. 43.5%, respectively). Heifers in the late breeding group appeared to compensate in terms of BW gain (0.11 vs. 0.15 kg/d, for CON and WDG, respectively; P = 0.12) during the pasture phase of the experiment (Table 3). Proportion of pubertal heifers was greater (P < 0.01; Table 4) for CON compared with WDG after treatment diets were fed for 28 and 56 d. Conversely, proportion of pubertal heifers was not different (P > 0.10) after 84 d or at initiation of ovulation synchronization (d 100 for the early breeding group, d 128 for the late breeding group; Table 4). Conception to fixedtime AI was not different (P = 0.70) between treatments and averaged 46%. Likewise, overall pregnancy rate (86%) was not affected (P = 0.66) by development-diet treatment. Thus, heifers fed WDG must have achieved sufficient growth and body condition to initiate puberty, in spite of their lower intake and growth rate, and cycled at least 23 d before breeding. Diet cost for the WDG diet was $35.01/t numerically less than that for the CON diet ($80.44/t vs. $115.45/t, respectively). Therefore, the WDG diet may be considered more cost effective because WDG-fed heifers overcame their slower growth rate during the development period as shown by breeding performance (Table 4). Similar proportions of heifers in both treatments were cycling before ovulation synchronization and conceived to fixed-time AI. Age at puberty can be reduced when heifers are fed a high level of nutrition and delayed when heifers are nutritionally restricted (Wiltbank et al., 1966, 1969). Clanton et al. (1983) found that the timing of postweaning gain by replacement heifers did not affect subsequent breeding perfor-
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Jaeger et al.
Table 4. Reproductive performance of beef replacement heifers fed diets containing either soybean meal (CON) or wet distillers grains (WDG) as the primary dietary protein source during a 94-d development period Treatment mean, % Item
CON
WDG
SE
P-value
Pubertal at d 28 Pubertal at d 56 Pubertal at d 84 Pubertal at onset of ovulation synchronization Early breeding group1 Late breeding group2 Fixed-time AI pregnancy rate Early breeding group1 Late breeding group2 Overall pregnancy rate3
52.3 84.9 93.0
33.7 60.4 86.0
0.05 0.05 0.04
0.01 <0.01 0.13
93.0 93.5
88.4 89.8
0.03 0.04
0.29 0.51
45.0 43.5 87.2
43.2 51.0 84.9
0.08 0.07 0.04
0.87 0.46 0.66
Heifers in the early breeding group were bred via fixed-time AI 23 d after treatment diets were terminated. Heifers in the late breeding group were bred via fixed-time AI 51 d after treatment diets were terminated. 3 All heifers were exposed for natural-service breeding 10 d after fixed-time AI for 35 d. 1 2
mance, provided that adequate BW was achieved by the beginning of the breeding season. These authors concluded there is flexibility in the procedures by which heifers can be developed and that achieving a targeted BW could be accomplished through more cost-efficient means. Similarly, Lynch et al. (1997) found that heifers accruing most of their prebreeding BW late in the development period (0.11 kg ADG for 112 d followed by 0.91 kg ADG for 47 d) consumed less feed than did heifers that were fed to achieve a consistent rate of gain (0.45 kg ADG for 159 d) during development. Additionally, restricted heifers in that study tended to have greater first-service conception rate in 1 of the 2 yr the experiment was conducted. Our heifers, regardless of treatment group, had apparently reached an adequate prebreeding BW because 93% of CON heifers and 89% of WDG heifers had attained puberty by the time ovulation synchronization was initiated. Funston and Deutscher (2004) reported that developing heifers to only 53% of mature BW did not adversely affect reproduction or calf production traits compared with developing heifers to 58% of mature BW. Similar to our study, they also found that developing heifers
to achieve more modest prebreeding target BW decreased feed costs. Under the conditions of this study, developing replacement heifers with WDG-containing diets increased age at puberty and decreased growth performance during the feeding period. However, the proportion of heifers that had attained puberty was similar between treatments at the time of fixed-time AI and did not affect fixedtime AI or overall pregnancy rates.
IMPLICATIONS Total feed costs during the development period were less for replacement heifers fed WDG as the primary dietary protein source than for heifers fed soybean meal as the primary protein source. This was due to the lesser cost and lesser consumption of the diet containing WDG. However, heifers fed the diet containing WDG as the primary protein source were older at puberty than those fed the diet containing soybean meal as the primary protein source; conception rates could have been negatively affected if heifers had been exposed for breeding earlier in the year. Further research is warranted to evaluate the effects of WDG inclusion rate, duration of feeding, and diet composition in relation
to timing of puberty and breeding of replacement beef heifers.
LITERATURE CITED Bandyk, C. A., R. C. Cochran, T. A. Wickersham, E. C. Titgemeyer, C. G. Farmer, and J. J. Higgins. 2001. Effect of ruminal vs postruminal administration of degradable protein on utilization of low-quality forage by beef steers. J. Anim. Sci. 79:225–231. Cao, Z. J., J. L. Anderson, and K. F. Kalscheur. 2009. Ruminal degradation and intestinal digestibility of dried or wet distillers grains with increasing concentrations of condensed distillers soluble. J. Anim. Sci. 87:3013–3019. Clanton, D. C., L. E. Jones, and M. E. England. 1983. Effect of rate and time of gain after weaning on the development of replacement beef heifers. J. Anim. Sci. 56:280–285. Funston, R. N., and G. H. Deutscher. 2004. Comparison of target breeding weight and breeding date for replacement beef heifers and effects on subsequent reproduction and calf performance. J. Anim. Sci. 82:3094–3099. Howlett, C. M., E. S. Vanzant, L. H. Anderson, W. R. Burris, B. G. Fieser, and R. F. Bapst. 2003. Effect of supplemental nutrient source on heifer growth and reproductive performance, and on utilization of corn silagebased diets by beef steers. J. Anim. Sci. 81:2367–2378. Klopfenstein, T. J., G. E. Erickson, and V. R. Bremer. 2008. Board-invited review: Use of distillers by-products in the beef cattle feeding industry. J. Anim. Sci. 86:1223–1231.
Wet distillers grains for heifer development diets Köster, H. H., R. C. Cochran, E. C. Titgemeyer, E. S. Vanzant, I. Abdelgadir, and G. St-Jean. 1996. Effect of increasing degradable intake protein on intake and digestion of lowquality, tallgrass-prairie forage by beef cows. J. Anim. Sci. 74:2473–2481. Lesmeister, J. L., P. J. Burfening, and R. L. Blackwell. 1973. Date of first calving in beef cows and subsequent calf production. J. Anim. Sci. 36:1–6. Lynch, J. M., G. C. Lamb, B. L. Miller, R. T. Brandt Jr., R. C. Cochran, and J. E. Minton. 1997. Influence of timing of gain on growth and reproductive performance of beef replacement heifers. J. Anim. Sci. 75:1715–1722. NRC. 2000. Nutrient Requirements of Beef Cattle. 7th rev. ed. Natl. Acad. Press, Washington, DC.
Olson, K. C., R. C. Cochran, T. J. Jones, E. S. Vanzant, E. C. Titgemeyer, and D. E. Johnson. 1999. Effects of ruminal administration of supplemental degradable intake protein and starch on utilization of low-quality, warm-season grass hay by beef steers. J. Anim. Sci. 77:1016–1025. Pritchard, R. H., and K. W. Bruns. 2003. Controlling variation in feed intake through bunk management. J. Anim. Sci. 81(E. Suppl. 2):E133–E138. Skaggs, C. L., B. V. Able, and J. S. Stevenson. 1986. Pulsatile or continuous infusion of luteinizing hormone-releasing hormone and hormonal concentrations in prepubertal beef heifers. J. Anim. Sci. 62:1034–1048. Wagner, J. J., K. S. Lusby, J. W. Oltjen, J. Rakestraw, R. P. Wettermann, and L. E.
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Walters. 1988. Carcass composition in mature Hereford cows: Estimation and effect on daily metabolizable energy requirement during winter. J. Anim. Sci. 66:603–612. Wiltbank, J. N., K. E. Gregory, L. A. Swinger, J. E. Ingalls, J. A. Rothlisberger, and R. M. Koch. 1966. Effects of heterosis and age and weight at puberty in beef heifers. J. Anim. Sci. 25:744–751. Wiltbank, J. N., C. W. Kasson, and J. E. Ingalls. 1969. Puberty in crossbred and straightbred beef heifers on two levels of feed. J. Anim. Sci. 29:602–605.
©2012 American Registry of Professional Animal Scientists
Growth and reproductive performance of beef
replacement heifers fed development diets containing soybean meal or wet distillers grains1 J. R. Jaeger,*2 PAS, J. W. Waggoner,* PAS, K. C. Olson,† PAS, K. R. Harmoney,* and J. W. Bolte* *Western Kansas Agricultural Research Center, Kansas State University, Hays 67601; and †Department of Animal Sciences and Industry, Kansas State University, Manhattan 66506
ABSTRACT Our objective was to evaluate the effects of replacing soybean meal with wet distillers grains plus solubles (WDG) in beef heifer development diets on growth and reproductive performance. Weaned heifers (n = 172; initial BW 319 ± 2 kg; age 282 ± 1 d) were stratified by BW and age and assigned randomly to be fed development diets using soybean meal (CON) or WDG as the primary source of CP in the diet. Heifers were allotted equally to 8 pens, adapted to diets for 14 d, and fed for ad libitum intake for 94 d. Heifer BW was measured on d 28, 56, and 84 relative to the beginning of the experiment and at breeding; paired serum samples were collected at these times to define puberty status. After 94 d, treatments were combined in a native shortContribution no. 11-323-J from the Kansas Agricultural Experiment Station. 2 Corresponding author: [email protected] 1
grass rangeland pasture. Heifers from each treatment were exposed to ovulation synchronization and fixed-time AI 23 or 51 d after diets ended. Total DM delivered was 4,695 kg less (P < 0.01) for WDG (57,131 kg) than for CON (61,826 kg). Daily DMI by WDG (7.07 kg) was 0.58 kg less (P < 0.01) than that by CON (7.65 kg), resulting in greater (P < 0.01) ADG throughout the development period for CON heifers (0.47 kg/d) than for WDG heifers (0.32 kg/d). Proportion of pubertal heifers was greater (P < 0.01) for CON compared with WDG on d 28 and 56 but not on d 84 or at breeding (P > 0.10). Conception to fixed-time AI and overall pregnancy rates were not different (P > 0.60) between treatments. Under the conditions of our study, developing replacement heifer diets using WDG as the primary source of CP had negative temporal effects on growth performance and age at puberty; however, these effects were nullified when heifers were allowed to graze native range for at least 23 d before breeding.
Key words: beef heifer, puberty, wet distillers grains
INTRODUCTION Proper development of replacement heifers is necessary to ensure maximum lifetime productivity by reducing age at first parturition (Lesmeister et al., 1973). Development of heifers should also be achieved at minimal cost without sacrificing performance. Wet distillers grains plus solubles (WDG) are a common component of diets fed to growing and finishing beef cattle; WDG is used also as a winter protein supplement for beef heifers and cows because of the modest cost per unit of CP. During ethanol production, protein is concentrated 3-fold relative to corn (Klopfenstein et al., 2008); therefore, WDG typically replaces a portion of the grain and most of the protein in feedlot diets. Heifers are often developed on foragebased diets of modest quality; high-
Wet distillers grains for heifer development diets
Table 1. Ingredient and nutrient compositions of replacement beef heifer development diets containing either soybean meal (CON) or wet distillers grains plus solubles (WDG) as the primary dietary protein source Diet, DM basis Item Ingredient composition, % Sorghum hay, ground Sorghum grain, rolled Soybean meal WDG Vitamin-mineral premix Calcium carbonate Salt Nutrient analysis1 DM, % CP, % RDP,2 % of CP NEm,3 Mcal/kg NEg,3 Mcal/kg NDF, % ADF, % TDN,3 % Calcium, % Phosphorus, % Sulfur, %
CON
80.5 10.4 7.82 — 0.64 0.31 0.31 79.4 10.7 67.0 1.48 0.75 47.4 35.3 60.6 0.86 0.21 0.17
WDG
75.7 10.4 — 12.4 0.58 0.62 0.31 67.5 10.1 64.4 1.48 0.75 41.1 35.4 60.6 0.99 0.25 0.23
Analysis conducted by SDK Laboratories, Hutchinson, KS. Calculated from diet-formulation software (BRaNDS 07, Ames, IA). 3 Calculated according to NRC (2000). 1 2
protein feedstuffs and supplements that promote fiber digestion are a logical complement to diets of this type. Howlett and coworkers (2003) evaluated soybean meal, whole linted cottonseed, whole raw soybeans, or pelleted soyhulls as protein sources in isonitrogenous heifer development diets. They observed no differences in proportion of pubertal heifers at initiation of the breeding season or in first-service conception rates and concluded that, independent of protein source, performance responses of heifers were predictable based on known relationships between nutrient composition and animal performance. Ruminal degradability of CP in the feedstuffs evaluated by Howlett et al. (2003) was substantial; however, WDG protein has modest ruminal degradability (NRC, 2000). This may limit the functionality of WDG as a supplement for low-quality forage di-
ets. Based on these data, we hypothesized that the level of RDP provided by WDG would limit DMI of heifers consuming a low-quality forage-based diet. Therefore, our objective was to document the effects of replacing soybean meal with WDG in replacement heifer development diets on growth and reproductive performance.
MATERIALS AND METHODS Animals and Experimental Design All procedures involving the handling and care of animals used in our experiment were approved by the Kansas State University Institutional Animal Care and Use Committee (Protocol number 2799.3). Springborn crossbred beef heifers (n = 172; initial BW = 319 ± 2 kg, age = 282 ± 1 d) that were preconditioned,
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weaned, and backgrounded for 60 d were stratified by BW and age. Heifers were then assigned randomly to development diets containing soybean meal (CON) or WDG as the primary source of protein (Table 1). Heifers were allotted randomly within treatment to 8 pens (4 pens/treatment) and adapted to assigned development diets for 14 d. Diets were formulated to be similar in CP and energy content (Table 1) and were fed for ad libitum intake for 94 d following the end of the adaptation period. Heifers were fed once daily at 0700 h, and bunks were evaluated each morning at 0630 h. If the previous day’s feed was consumed, total feed delivered was increased by approximately 2% of the previous day’s feed delivery. Bunks were managed using a slick or clean bunk-management method to minimize feed refusals (Pritchard and Bruns, 2003). On d 95, heifers were removed from treatment pens and combined in a single native shortgrass rangeland pasture. Prior to the experiment, it was hypothesized that the level of RDP provided by WDG would limit DMI and ultimately decrease heifer performance during the drylot development period compared with heifers fed the CON diet. Based on performance data collected during the drylot development period, an ad hoc decision was made to randomly allot equal proportions of heifers from each treatment to an early or late breeding group to ascertain the drylot performance effects on conception to fixedtime AI. The early breeding group was exposed to ovulation synchronization and bred via fixed-time AI 23 d after development diets were terminated. The late breeding group was exposed to ovulation synchronization and bred via fixed-time AI 51 d after development diets were terminated.
Data Collection Heifer BW was measured every 28 d during the development period (i.e., d 1 to 94) and immediately before fixedtime AI. A BCS (scale 1 to 9; 1 = extremely thin, 9 = obese; Wagner et
302 al., 1988) was assigned to each animal by 2 trained evaluators blinded to treatment immediately before fixedtime AI. Weekly diet samples were collected from each pen, composited by treatment, and immediately frozen. At the conclusion of the study, weekly composite samples were combined to create treatment-diet composites, which were submitted to a commercial laboratory for analysis (SDK Laboratories, Hutchinson, KS; DM, CP, NEm, NEg, NDF, ADF, TDN, Ca, P, and S).
Puberty Evaluation Paired blood samples, collected at 10-d intervals, were obtained from all heifers via jugular venipuncture every 28 d during the feeding period, 10 d before initiation of ovulation synchronization, and on the day ovulation synchronization was initiated. Samples were collected with 16 × 100 mm Vacutainer tubes and then immediately placed on ice, allowed to clot for 24 h at 4°C, and then centrifuged (1,500 × g) for 10 min at 4°C. Serum was decanted into 12 × 75 mm plastic tubes and immediately frozen (−20°C). Concentration of progesterone in serum was subsequently quantified by RIA (Skaggs et al., 1986). Intra- and interassay CV were 7.0 and 7.9%, respectively, and assay sensitivity was 0.019 ng/mL. When samples contained concentrations of progesterone ≥1 ng/mL, heifers were considered to have attained puberty and be estrous-cycling.
Synchronization and Breeding For each breeding group of heifers (inseminated 23 or 51 d after termination of treatment diets), ovulation was synchronized using the 7-d CO-Synch+CIDR protocol; heifers were inseminated by fixed-time AI 54 to 56 h after CIDR removal. Heifers were exposed to fertile bulls 10 d after fixed-time AI for the remaining 35 d of a 45-d breeding season. Conception to fixed-time AI was determined via ultrasound 35 d after insemination, and final pregnancy rate was deter-
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mined via rectal palpation 60 d after the end of the breeding season.
Statistical Analysis Heifer performance data during the feeding period were analyzed as a completely random design (PROC GLM; SAS Institute Inc., Cary, NC). The model included effects for treatment and pen. Pen was considered the experimental unit. Heifer performance data during the pasture phase were analyzed as a completely random design (PROC GLM; SAS Institute Inc.). The model included an effect for treatment only; animal was considered the experimental unit. Proportion of pubertal heifers, fixed-time AI pregnancy rates, and overall pregnancy rates were analyzed using logistic regression (PROC CATMOD; SAS Institute Inc.). The original model used to assess differences in fixed-time AI pregnancy rates and overall pregnancy rates included effects for treatment and breeding group. Breeding group effects and associated interactions were not significant (P > 0.10) and were removed from the final model. Least squares means for pregnancy rates were reported. Treatment differences in performance, proportion of pubertal heifers, fixed-time AI pregnancy rates, and overall pregnancy rates were discussed when P ≤ 0.05; tendencies were discussed when P > 0.05 and ≤0.10.
RESULTS AND DISCUSSION Chemical composition of treatment diets and calculated dietary energy values are presented in Table 1. Diets were verified to contain sufficient metabolizable protein to support maintenance and growth for the heifers in this study (model level 1; NRC, 2000). Treatment diets were fed ad libitum and formulated to contain similar concentrations of CP, NEm, and NEg. In spite of these conditions, heifers fed the development diet containing WDG consumed less feed than did heifers fed the development diet containing soybean meal. Total
DM delivered during the 94-d feeding period was numerically 4,694 kg less (P < 0.01) for heifers fed the WDG diet than for heifers fed the CON diet (data not shown). Likewise, average daily DMI by heifers fed the WDG diet was 0.58 kg/d less (P < 0.01) than that by heifers fed the CON diet (7.07 vs. 7.65, respectively; Table 2). This resulted in greater (P < 0.01) BW change and ADG during each 28-d period and throughout the development period for CON-fed heifers than for WDG-fed heifers (Table 2). Theoretically, the WDG diet may have been deficient in RDP relative to the CON diet. The assumed RDP values for WDG and soybean meal used during diet formulation were 48 and 66%, respectively (NRC, 2000). Our diet-formulation software (BRaNDS 07, Ames, IA) indicated that the RDP for the WDG and CON diets was 64.4 and 67.0% of total CP, respectively, (Table 1) and supplied 460 and 547 g/d of RDP, respectively. In contrast, Cao et al. (2009) indicated that the A fraction of WDG (with proportions of condensed distillers solubles ranging from 0 to 40%) averaged 29.5% of total CP. Using this value for ruminal degradability of CP from WDG, our calculated dietary RDP intakes would have been 379 and 547 g/d for WDG and CON diets, respectively. Lowquality forage sorghum hay (6.5% CP) composed the bulk of the diets used in our study. Köster et al. (1996) indicated that dietary RDP:digestible OM should equal 0.11 to 0.13 in diets based on low-quality, warm-season forages. In the case of our WDG diet, the value of the ratio was only 0.10, indicating that low RDP intake may have caused reduced intake and gain of the heifers fed the WDG diet. Bandyk et al. (2001) reported that diets adequate in metabolizable protein but deficient in RDP resulted in depressed low-quality forage OM intake. Likewise, Olson et al. (1999) found that adequate supplemental RDP increased intake and digestion of low-quality, warm-season forage. At the end of the developmentdiet feeding period, overall ADG was greater (P < 0.01) for heifers fed
Wet distillers grains for heifer development diets
Table 2. Growth performance of beef replacement heifers fed diets containing either soybean meal (CON) or wet distillers grains plus solubles (WDG) as the primary dietary protein source during a 94-d development period Treatment mean Item No. of pens No. of heifers Days on feed Growth performance Initial BW, kg Final BW, kg Total BW change, kg DMI, kg/d ADG d 1 to 28, kg ADG d 29 to 56, kg ADG d 57 to 84, kg Overall ADG, d 1 to 94, kg
CON
WDG
SE
P-value
4 85 94 323 367 44.0 7.65 0.62 0.30 0.83 0.47
4 86 94 327 357 30.4 7.07 0.37 0.10 0.40 0.32
— — —
— — —
CON than for heifers fed WDG. Likewise, final heifer BW also tended to be greater (P < 0.10) for CON than for WDG (Table 2). At the beginning of the pasture phase of the experiment, BW of heifers assigned to the early breeding averaged 366 kg for WDG and 358 kg for CON (P = 0.33). Body weight and BCS at breeding were not different (P
3.3 3.9 1.8 0.04 0.03 0.04 0.03 0.02
0.31 0.09 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01
≥ 0.73) between CON and WDG heifers in the early breeding group (Table 3). Conversely, WDG heifers lost an average of 0.19 kg/d during the pasture phase of the experiment, whereas CON heifers gained 0.15 kg/d (P = 0.01; Table 3). Heifer BW in the late breeding group averaged 351 kg for WDG and 374 kg for CON (P < 0.01) at the
Table 3. Growth performance of beef replacement heifers grazing native shortgrass rangeland pasture that were previously fed development diets containing either soybean meal (CON) or wet distillers grains plus solubles (WDG) as the primary dietary protein source Treatment mean Item Early breeding group1 Initial BW, kg BW at breeding, kg Prebreeding ADG, kg BCS2 at breeding Late breeding group3 Initial BW, kg BW at breeding, kg Prebreeding ADG, kg BCS2 at breeding
CON
358 361 0.15 5.78 374 387 0.25 6.14
WDG
366 362 −0.19 5.82 351 368 0.34 5.88
SE
4.1 3.8 0.07 0.05 3.7 3.3 0.03 0.04
P-value
0.33 0.92 0.01 0.73 <0.01 <0.01 0.12 <0.01
Heifers in the early breeding group were bred via fixed-time AI 23 d after treatment diets were terminated. 2 BCS scale: 1 to 9 (1 = emaciated, 9 = obese). 3 Heifers in the late breeding group were bred via fixed-time AI 51 d after treatment diets were terminated. 1
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beginning of the pasture phase of the experiment (Table 3). Body weight and BCS at breeding were less (P < 0.01) for WDG heifers than for CON heifers; however, heifers fed WDG achieved adequate prebreeding BW and BCS (Table 3) based on similar (P = 0.46) fixed-time AI pregnancy rates for the WDG and CON heifers (51.0 vs. 43.5%, respectively). Heifers in the late breeding group appeared to compensate in terms of BW gain (0.11 vs. 0.15 kg/d, for CON and WDG, respectively; P = 0.12) during the pasture phase of the experiment (Table 3). Proportion of pubertal heifers was greater (P < 0.01; Table 4) for CON compared with WDG after treatment diets were fed for 28 and 56 d. Conversely, proportion of pubertal heifers was not different (P > 0.10) after 84 d or at initiation of ovulation synchronization (d 100 for the early breeding group, d 128 for the late breeding group; Table 4). Conception to fixedtime AI was not different (P = 0.70) between treatments and averaged 46%. Likewise, overall pregnancy rate (86%) was not affected (P = 0.66) by development-diet treatment. Thus, heifers fed WDG must have achieved sufficient growth and body condition to initiate puberty, in spite of their lower intake and growth rate, and cycled at least 23 d before breeding. Diet cost for the WDG diet was $35.01/t numerically less than that for the CON diet ($80.44/t vs. $115.45/t, respectively). Therefore, the WDG diet may be considered more cost effective because WDG-fed heifers overcame their slower growth rate during the development period as shown by breeding performance (Table 4). Similar proportions of heifers in both treatments were cycling before ovulation synchronization and conceived to fixed-time AI. Age at puberty can be reduced when heifers are fed a high level of nutrition and delayed when heifers are nutritionally restricted (Wiltbank et al., 1966, 1969). Clanton et al. (1983) found that the timing of postweaning gain by replacement heifers did not affect subsequent breeding perfor-
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Table 4. Reproductive performance of beef replacement heifers fed diets containing either soybean meal (CON) or wet distillers grains (WDG) as the primary dietary protein source during a 94-d development period Treatment mean, % Item
CON
WDG
SE
P-value
Pubertal at d 28 Pubertal at d 56 Pubertal at d 84 Pubertal at onset of ovulation synchronization Early breeding group1 Late breeding group2 Fixed-time AI pregnancy rate Early breeding group1 Late breeding group2 Overall pregnancy rate3
52.3 84.9 93.0
33.7 60.4 86.0
0.05 0.05 0.04
0.01 <0.01 0.13
93.0 93.5
88.4 89.8
0.03 0.04
0.29 0.51
45.0 43.5 87.2
43.2 51.0 84.9
0.08 0.07 0.04
0.87 0.46 0.66
Heifers in the early breeding group were bred via fixed-time AI 23 d after treatment diets were terminated. Heifers in the late breeding group were bred via fixed-time AI 51 d after treatment diets were terminated. 3 All heifers were exposed for natural-service breeding 10 d after fixed-time AI for 35 d. 1 2
mance, provided that adequate BW was achieved by the beginning of the breeding season. These authors concluded there is flexibility in the procedures by which heifers can be developed and that achieving a targeted BW could be accomplished through more cost-efficient means. Similarly, Lynch et al. (1997) found that heifers accruing most of their prebreeding BW late in the development period (0.11 kg ADG for 112 d followed by 0.91 kg ADG for 47 d) consumed less feed than did heifers that were fed to achieve a consistent rate of gain (0.45 kg ADG for 159 d) during development. Additionally, restricted heifers in that study tended to have greater first-service conception rate in 1 of the 2 yr the experiment was conducted. Our heifers, regardless of treatment group, had apparently reached an adequate prebreeding BW because 93% of CON heifers and 89% of WDG heifers had attained puberty by the time ovulation synchronization was initiated. Funston and Deutscher (2004) reported that developing heifers to only 53% of mature BW did not adversely affect reproduction or calf production traits compared with developing heifers to 58% of mature BW. Similar to our study, they also found that developing heifers
to achieve more modest prebreeding target BW decreased feed costs. Under the conditions of this study, developing replacement heifers with WDG-containing diets increased age at puberty and decreased growth performance during the feeding period. However, the proportion of heifers that had attained puberty was similar between treatments at the time of fixed-time AI and did not affect fixedtime AI or overall pregnancy rates.
IMPLICATIONS Total feed costs during the development period were less for replacement heifers fed WDG as the primary dietary protein source than for heifers fed soybean meal as the primary protein source. This was due to the lesser cost and lesser consumption of the diet containing WDG. However, heifers fed the diet containing WDG as the primary protein source were older at puberty than those fed the diet containing soybean meal as the primary protein source; conception rates could have been negatively affected if heifers had been exposed for breeding earlier in the year. Further research is warranted to evaluate the effects of WDG inclusion rate, duration of feeding, and diet composition in relation
to timing of puberty and breeding of replacement beef heifers.
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Wet distillers grains for heifer development diets Köster, H. H., R. C. Cochran, E. C. Titgemeyer, E. S. Vanzant, I. Abdelgadir, and G. St-Jean. 1996. Effect of increasing degradable intake protein on intake and digestion of lowquality, tallgrass-prairie forage by beef cows. J. Anim. Sci. 74:2473–2481. Lesmeister, J. L., P. J. Burfening, and R. L. Blackwell. 1973. Date of first calving in beef cows and subsequent calf production. J. Anim. Sci. 36:1–6. Lynch, J. M., G. C. Lamb, B. L. Miller, R. T. Brandt Jr., R. C. Cochran, and J. E. Minton. 1997. Influence of timing of gain on growth and reproductive performance of beef replacement heifers. J. Anim. Sci. 75:1715–1722. NRC. 2000. Nutrient Requirements of Beef Cattle. 7th rev. ed. Natl. Acad. Press, Washington, DC.
Olson, K. C., R. C. Cochran, T. J. Jones, E. S. Vanzant, E. C. Titgemeyer, and D. E. Johnson. 1999. Effects of ruminal administration of supplemental degradable intake protein and starch on utilization of low-quality, warm-season grass hay by beef steers. J. Anim. Sci. 77:1016–1025. Pritchard, R. H., and K. W. Bruns. 2003. Controlling variation in feed intake through bunk management. J. Anim. Sci. 81(E. Suppl. 2):E133–E138. Skaggs, C. L., B. V. Able, and J. S. Stevenson. 1986. Pulsatile or continuous infusion of luteinizing hormone-releasing hormone and hormonal concentrations in prepubertal beef heifers. J. Anim. Sci. 62:1034–1048. Wagner, J. J., K. S. Lusby, J. W. Oltjen, J. Rakestraw, R. P. Wettermann, and L. E.
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Walters. 1988. Carcass composition in mature Hereford cows: Estimation and effect on daily metabolizable energy requirement during winter. J. Anim. Sci. 66:603–612. Wiltbank, J. N., K. E. Gregory, L. A. Swinger, J. E. Ingalls, J. A. Rothlisberger, and R. M. Koch. 1966. Effects of heterosis and age and weight at puberty in beef heifers. J. Anim. Sci. 25:744–751. Wiltbank, J. N., C. W. Kasson, and J. E. Ingalls. 1969. Puberty in crossbred and straightbred beef heifers on two levels of feed. J. Anim. Sci. 29:602–605.