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Utilization of dried distillers grains for developing beef heifers^1,2,3

J. L. Martin^*,, A. S. Cupp^*, R. J. Rasby^*, Z. C. Hall^* and R. N. Funston^*,,4

^* Department of Animal Science, University of Nebraska, Lincoln 68583; and and University of Nebraska, West Central Research & Extension Center, North Platte 69101

	Abstract

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION LITERATURE CITED

 
A 2-yr study was conducted at 2 locations to determine if supplementing beef heifers with dried distillers grains (DDG) as an energy source affected growth or reproduction. Spring-born crossbred heifers (n = 316) were blocked by age or sire and age and assigned randomly to DDG or control (dried corn gluten feed, whole corn germ, urea) supplement. Heifers received prairie hay in amounts sufficient for ad libitum intake and 0.59% of BW DDG or 0.78% of BW control supplement (DM basis). Supplements were formulated to be isocaloric, but protein degradability differed. Supplemental undegradable intake protein intake from DDG averaged 267 g/animal daily and reached 318 g/animal daily; control supplemental undegradable intake protein intake averaged 90 g/animal daily and peaked at 107 g/animal daily. Initial pubertal status was determined by 2 blood samples collected 10 d apart, and monthly BW were collected from November through January; then biweekly BW and blood samples were collected from February until May yearly. Heifers were synchronized with 2 injections of PGF₂14 d apart; estrus was detected and heifers were artificially inseminated for 5 d and placed with bulls 10 d later. Conception and pregnancy rates were determined via transrectal ultrasonography. Initial age, BW, and BCS did not differ (P > 0.92) for control and DDG heifers. Final BW, ADG, and final BCS also were not affected (P > 0.31) by supplementation. Estimated age and BW at puberty did not differ (P > 0.23) between treatments, and the proportions of pubertal heifers did not differ at the initiation of the experiment (P > 0.82), at the beginning of the 14-d sampling intervals, or before synchronization. Estrus synchronization rate (75.9%), time of estrus, and overall pregnancy rate (89.5%) were not affected (P > 0.14) by treatment. However, a greater proportion (P = 0.008) of DDG than control heifers conceived to AI (75.0 vs. 52.9%), resulting in greater (P = 0.07) AI pregnancy rates for DDG heifers (57.0 vs. 40.1%). Body weight or BCS at pregnancy diagnosis did not differ (P > 0.52) between DDG and control heifers. Supplementing beef heifers with DDG during development did not affect age at puberty but improved AI conception and pregnancy rates compared with an isocaloric control supplement.

Key Words: beef cattle • dried distillers grain • heifer development • puberty • reproduction • undegradable intake protein

	INTRODUCTION

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION LITERATURE CITED

 
The majority of replacement beef heifers developed in the Midwest are fed forage-based diets supplemented with protein and energy to achieve traditional target weights of 60 to 65% of mature BW (Patterson et al., 1992). In forage-based diets, dried distillers grains (DDG) have greater energy value than corn (Loy et al., 2003). Crude protein concentration of DDG is nearly 30%, with approximately 50% or more of CP in the form of undegradable intake protein (UIP; Benton et al., 2006). Dried distillers grains also have relatively high concentrations of P, which reduces or eliminates the need for supplemental P with many forage diets (NRC, 2000). Development of new ethanol plants is likely to increase the proportion of corn grown in the Midwest used for ethanol production by the corn dry-milling industry. Therefore, DDG may be economically feasible as the primary source of energy and protein for growing replacement heifers.

When DDG are fed as an energy source in growing heifer diets, UIP is commonly supplied in excess of requirements. Supplementation of prepubertal heifers with 421 g of UIP/d, primarily from blood meal, increased BW at puberty compared with control heifers fed 231 g UIP/d; high UIP heifers also had increased age at puberty compared with heifers fed the control supplement plus monensin (Lalman et al., 1993). In the same study, fewer heifers fed high UIP supplements were detected in estrus during the first 21 d of the breeding season, but pregnancy rates did not differ. Additionally, supplementing postpubertal heifers with high UIP (321 g/d), mainly from feathermeal and fish-meal, decreased serum concentrations of FSH compared with heifers consuming 115 g/d UIP (Kane et al., 2004).

The objective of this study was to determine if supplementing beef heifers with excess UIP from DDG during development affects heifer growth or reproduction.

	MATERIALS AND METHODS

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION LITERATURE CITED

 
Heifers
All procedures were approved by the University of Nebraska Institutional Animal Care and Use Committee. In each of 2 yr, weaned heifer calves (n = 316) were stratified by age at location 1 (n = 151; University of Nebraska Dalbey-Halleck farm, Virginia, NE) and by age by sire at location 2 (n = 165; University of Nebraska Agricultural Research and Development Center, Ith-aca, NE), and assigned randomly to receive DDG or control supplement (Table 1) during development. Heifers from location 1 were of composite Angus x Simmen-tal and Angus x Gelbvieh genetics. At location 2, composite MARC III (1/4Angus, 1/4 Hereford, 1/4 Red Poll, 1/4 Pinzgauer) x Red Angus heifers were utilized. Heifers were weaned in mid October yearly at an average age of 200 d, and supplementation began in mid November at an average age of 239 d. Between weaning and initiation of the experiment, heifers at location 1 were maintained in a drylot and offered ad libitum access to prairie hay. Heifers at location 2 were allowed to graze cool-season pasture between weaning and the beginning of the experiment. The supplementation period was 196 d in yr 1 and 190 d in yr 2, concluding in late May yearly.

Supplementation
During the supplementation phase of the experiment, heifers were maintained in drylots and allowed ad libitum access to prairie hay (Table 2). Hay intake was not quantified. Hay samples were analyzed by the University of Nebraska Soil and Plant Analysis Laboratory (Lincoln, NE) using an NIRS 5000 (Foss North America Inc., Eden Prairie, MN) machine to determine forage nutrient concentration. Results of hay analysis for each location and year are presented in Table 1.

Supplements were bagged in approximately 22.7-kg bags. Heifers were fed daily in their respective groups with 0.5 m or more of bunk space per heifer. Supplement was offered at 0.78% of BW for control and 0.59% of BW for DDG heifers and adjusted after each weigh date. Each group was fed their respective supplement through the last day of AI, at which time heifers at each location were placed in a single group on cool-season pastures containing predominantly smooth brome grass (Bromus inermis Leyss.) and Kentucky bluegrass (Poa pratensis L.).

Blood Collection and Assay Procedures
Blood samples were collected via coccygeal venipuncture into tubes containing liquid K₃EDTA (BD Vacutainer, BD Diagnostics, Franklin Lakes, NJ) and cooled immediately on ice. Plasma was harvested via centrifugation within 4 h of collection and frozen at –20°C until analysis. Plasma concentrations of progesterone were determined by direct solid-phase RIA (Coat-A-Count, Diagnostics Products Corp., Los Angeles, CA), with modifications described by Melvin et al. (1999). Intra-and interassay CV (n = 7 assays) for samples from yr 1 were 3.1 and 6.8%, respectively. Samples from yr 2 were evaluated in 10 assays, with intra- and interassay CV of 4.6 and 8.0%, respectively.

Initial pubertal status of heifers was determined in November, immediately before initiation of supplementation. Two blood samples were collected 10 d apart, and plasma concentrations of progesterone were utilized to determine the proportion of heifers pubertal before treatment. Further blood sampling began in mid February yearly, with blood samples collected every 14 d to determine approximate age at puberty. Concentrations of progesterone greater than 1 ng/mL were interpreted to indicate ovarian luteal activity and therefore attainment of puberty.

Estrus Synchronization and Artificial Insemination
Estrus was synchronized using 2 injections of PGF₂ (PGF; Prostamate, IVX Animal Health, St. Joseph, MO) administered 14 d apart. Injections were given i.m. in the neck. Estrus detection was performed for at least 1 h in the early morning and late evening for 5 d after the second PGF injection. Heifers observed in es-trus received AI approximately 12 h later. Within year, a single AI service sire was used at location 1 and 2 sires were used equally across treatments at location 2. Heifers were exposed to fertile bulls for approximately 45 d beginning 10 d after final AI. Conception rate to AI was determined via transrectal ultrasonography approximately 45 d after AI. An additional ultrasound pregnancy diagnosis was performed 45 d after removal of bulls to determine the final pregnancy rate.

In Situ UIP Determination
Undegradable intake protein content of supplement ingredients was determined using a 16-h in situ procedure. Sample preparation varied with feedstuff. Dried distillers grains were placed directly into Dacron bags without processing. Whole corn germ was ground to pass through a 2-mm screen before incubation. Dried corn gluten feed pellets were incubated as whole pellets and coarsely ground (4-mm screen) for each sample because grinding of the pellets through a 2-mm screen resulted in nearly complete washout in the rumen. In yr 1, approximately 10 g of sample was weighed into 10 x 20-cm bags with a 50-µm pore size. In yr 2, approximately 2 g of sample was used in 5 x 10-cm bags with the same pore size. Although sample size was different between years, Whittet et al. (2002) determined that sample size did not affect in situ UIP estimation. Samples from each year were incubated in duplicate for 0 and 16 h in the ventral rumen of a single donor. After retrieval from the rumen, the bags were gently hand-washed, dried for 12 h in a 60°C forced-air oven, and the residue was weighed. Protein content of feedstuffs and residue was determined using a Leco N analyzer (Leco Corp., St. Joseph, MI). Calculated UIP content (% of CP) of feedstuffs was determined as the ratio of CP in the residue remaining after in situ incubation compared with the CP in the unincubated feedstuff.

Statistical Analysis
Data were analyzed using PROC MIXED (SAS Inst. Inc., Cary, NC). Treatment group within year and location (n = 4 replications per treatment) was the experimental unit. The model included treatment, location, and the interaction of treatment and location. Year was included as a random effect. Least squares means were compared using the PDIFF option of SAS. Percentage of heifers reaching puberty, estrus synchronization response, conception rate, and pregnancy rates were analyzed after logit transformation using PROC MIXED as previously described (Cox, 1988; Martin et al., 2005). Technician and service sire were included in the initial model for AI conception and pregnancy rates but were removed from the final model because they were not significant.

	RESULTS AND DISCUSSION

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION LITERATURE CITED

 
Heifers supplemented with DDG consumed an average of 267 g/animal daily supplemental UIP. At the end of the supplementation period, at approximately the time of breeding, supplemental UIP intake reached 318 g/animal daily. The NRC (2000) model level 1 predicted a MP balance of 180 g/d for DDG heifers. However, the model assumes 80% digestibility for all UIP sources. Benton et al. (2006) reported UIP digestibility of DDG to be 88.8%. Therefore, it seems likely the MP balance reported in Table 2 is underestimated.

Heifer performance and BCS data are presented in Table 3. Age at the beginning of the study did not differ (P = 0.93) between groups but differed (P < 0.002) by location; heifers at location 1 averaged 250 ± 2 d of age and heifers at location 2 averaged 230 ± 2 d of age. Initial BW and BCS did not differ (P > 0.95) between control and DDG heifers and averaged 252 ± 13 kg of BW and 5.34 ± 0.07 BCS. Heifer BW at conclusion of supplementation was not affected (P > 0.63) by treatment or location. Final BW after supplementation averaged 373 ± 17 kg. At location 1, ADG were similar (P = 0.86) for DDG and control heifers (0.64 ± 0.04 kg vs. 0.65 ± 0.04 kg, respectively). Heifers at location 2 supplemented with DDG also had similar (P = 0.16) ADG to control and averaged 0.72 ± 0.04 kg and 0.60 ± 0.04 kg, respectively. Treatment did not (P = 0.60) influence BCS at the end of the supplement period and averaged 5.7 ± 0.1 for DDG heifers and 5.6 ± 0.1 for control heifers.

Lalman et al. (1993) reported similar pregnancy rates for heifers fed a high UIP supplement vs. those fed a supplement balanced for protein degradability. Kane et al. (2004) supplied postpubertal heifers 321, 216, or 115 g/d of UIP, mainly from feather meal and fishmeal. Heifers supplemented with 321 g of UIP/d had increased follicular fluid IGFBP-2 and IGFBP-4 on d 12 to 14 of the estrous cycle, lower basal serum FSH, and reduced FSH area under the curve compared with heifers fed 115 g of supplemental UIP/d, indicating high UIP intake may impair gonadotropin secretion and follicle development. In the current study, 75.0% of DDG heifers conceived to AI service, compared with 52.9% of control heifers (P = 0.008). Therefore, AI pregnancy rate for DDG heifers was 57.0% and was greater (P = 0.07) than AI pregnancy rate of control heifers (40.1%). Other studies have reported positive effects of high UIP supplements on reproduction. In pregnant heifers supplemented during late gestation and young postpartum cows, supplementation with high UIP feeds tends to improve subsequent reproductive performance when adequate dietary energy is supplied (Hawkins et al., 1999).

In the current study, both treatments supplied CP in excess of requirements (NRC, 2000). Heifers fed DDG were supplied excess CP in the form of UIP, whereas control heifers received excess CP in the form of DIP (Table 2). We are unable to determine if excess DIP in the control supplement decreased AI conception and pregnancy rates, rather than DDG supplementation increasing AI conception and pregnancy rates. Dairy heifers fed diets containing 21.8% CP with 82.5% of CP as degradable protein had decreased conception rate compared with heifers fed diets with 15.45% CP (73% degradable) due to decreased uterine pH 7 d after estrus (Elrod and Butler, 1993). However, uterine pH 7 d after estrus was reduced to the same extent by feeding diets with excess UIP (19.8% CP, 55.1% degradable) as excess DIP (20.4% CP, 75.4% degradable) to lactating Holstein cows (Elrod et al., 1993).

Limited research is available on effects of feeding highly degradable protein sources to beef heifers on reproductive performance. Kenny et al. (2001) increased CP intake of 18- to 24-mo-old beef heifers by fertilizing pastures with N. Forage from the pastures fertilized with high levels of N contained 23.2% CP (DM basis) and did not affect embryo survival at 30 d of gestation compared with forage (12.8% CP) from pastures fertilized with low levels of N; dietary CP was less in the current study.

Feeding diets that promote high plasma urea concentrations to beef heifers resulted in reduced embryo cleavage rates and blastocyst formation after in vitro fertilization of oocytes from small and medium follicles, but in vivo fertilization and embryonic development were not studied (Sinclair et al., 2000). Similarly, direct addition of urea to in vitro oocyte maturation media did not affect cleavage rate but decreased the proportion of cleaved oocytes that formed blastocysts at d 8 (Ocon and Hansen, 2003). In the current study, treatments were concluded 5 d after the second PGF injection, and heifers at each location were managed in a common group on pasture after AI. Heifers supplemented with DDG had similar (P = 0.35) overall pregnancy rates to control heifers. Weight and BCS at final pregnancy diagnosis were not affected (P > 0.52) by treatment.

As ethanol production in Nebraska and the Great Plains expands, greater opportunity will exist to incorporate DDG in replacement heifer diets. Dried distillers grains complement forage diets typically used for heifer development by supplying protein, energy, and P. Therefore, DDG alone may provide the majority of supplemental nutrients required in forage-based heifer development diets. In the current study, utilizing DDG as a source of protein and energy in heifer development diets to promote moderate gains did not influence age at puberty but enhanced AI conception and pregnancy rates compared with an isocaloric supplement.

	Footnotes

 
¹ A contribution of the University of Nebraska Agricultural Research Division, supported in part by funds provided through the Hatch Act. Mention of a trade name, proprietary products, or company name is for presentation clarity and does not imply endorsement by the authors or the University of Nebraska.

² The authors wish to thank Dakota Gold Marketing, Sioux Falls, SD; Cargill Inc., Blair, NE; Archer Daniels Midland Company, Columbus, NE; and IVX Animal Health, St. Joseph, MO, for donation of products.

³ The authors wish to acknowledge the financial support of the Nebraska Center for Energy Sciences Research and the Nebraska Public Power District, which partially funded this study.

⁴ Corresponding author: rfunston2{at}unl.edu

Received for publication February 1, 2007. Accepted for publication May 13, 2007.

	LITERATURE CITED

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION LITERATURE CITED

 


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Cox, C. 1988. Multinomial regression models based on continuation ratios. Stat. Med. 7:435–441.[Medline]

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This Article Abstract Full Text (PDF) All Versions of this Article: jas.2007-0076v1 85/9/2298    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Martin, J. L. Articles by Funston, R. N. Search for Related Content PubMed PubMed Citation Articles by Martin, J. L. Articles by Funston, R. N.