J. Anim Sci. 2006. 84:2410-2417. doi:10.2527/jas.2005-400
© 2006 American Society of Animal Science
Effects of interval-feeding whole sunflower seeds during mid to late gestation on performance of beef cows and their progeny1,2
J. P. Banta*,
D. L. Lalman*,3,
F. N. Owens
,
C. R. Krehbiel* and
R. P. Wettemann*
* Department of Animal Science, Oklahoma State University, Stillwater 74078 and
and
Pioneer Hi-Bred International Inc., Johnston, IA 50131
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Abstract
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This experiment was conducted to determine the effects of interval feeding of whole sunflower seeds on the performance of beef cows and their progeny. During mid to late gestation, 144 multiparous, spring-calving beef cows (588 kg of initial BW; 5.6 initial BCS; 4 to 13 yr old) were individually fed 1 of 3 supplements 4 d/wk for a 76-d period. Supplements (DM basis) included: 1) 0.68 kg of soybean meal/feeding (NCON); 2) 3.01 kg of a soybean hull-based supplement/feeding (PCON); and 3) 1.66 kg of whole sunflower seeds high in linoleic acid/feeding (WSUN). Supplements were formulated to provide similar amounts of CP and ruminally degraded intake protein; PCON and WSUN were also formulated to be isocaloric. During the supplementation period, cows had free-choice access to bermudagrass (Cynodon dactylon) and tall-grass prairie hay. By the end of the 76-d supplementation period, cows fed PCON (P < 0.01) and NCON (P < 0.01) had gained more BW than cows fed WSUN (33, 23, and 10 kg, respectively). However, from the end of this supplementation period to the beginning of the breeding season 84 d later, cows supplemented with PCON had lost more (P < 0.01) BW than cows supplemented with WSUN (–123 kg vs. –111 kg). Cow BW change through weaning (–50 kg, P = 0.43) and final cow BW (536 kg, P = 0.70) at weaning were not different among supplement groups. Furthermore, cow BCS was similar among supplement treatment groups at the end of the supplementation period (5.3, P = 0.09), at the beginning of the breeding season (4.8, P = 0.38), and at weaning (4.7, P = 0.08). No difference among treatments was detected for calf birth weight (36 kg, P = 0.42), calf weaning weight (235 kg, P = 0.67), percentage of cows exhibiting luteal activity at the beginning of the breeding season (57%, P = 0.29), or pregnancy rate (88%, P = 0.44). However, first service conception rate was greater (P = 0.01) for cows fed PCON (79%) and tended (P = 0.07) to be greater for cows fed WSUN (74%) than for cows fed NCON (53%). After weaning, all steer calves were placed in a feedlot and fed a high-concentrate finishing diet for an average of 188 d. Supplements fed to dams during gestation did not influence feedlot performance or carcass characteristics. Prepartum energy supplementation, regardless of energy source or prepartum energy balance, resulted in improved conception rate, but other measures of reproduction, calf and feedlot performance, and carcass characteristics were not affected.
Key Words: beef cow • prepartum lipid supplementation • sunflower
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INTRODUCTION
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Lipid supplements have been proposed as nutraceuticals to improve reproductive efficiency through increased functional capability of the ovary, alterations in PGF2
synthesis by the uterus, or both (Williams and Stanko, 2000
). Lipid supplementation during late gestation may improve reproductive efficiency of beef cows (Bellows et al., 2001; Hess et al., 2002). Lipid sources rich in PUFA, especially linoleic acid, seem more beneficial in altering reproductive physiology than lipid sources composed primarily of SFA (Williams and Stanko, 2000). However, when cows consume low to moderate quality forage, excess lipid intake may reduce fiber digestion (Jenkins, 1993).
Whole high-oil sunflower seeds have several characteristics of a desirable supplement for range beef cows; these include a high lipid concentration, a moderate concentration of protein, and excellent storage and handling characteristics. For these reasons, high-oil sunflower seeds could be used to replace traditional protein supplements, which concomitantly provide supplemental lipid. Supplementation of beef cattle with sunflower seeds or feeding diets containing sunflower seeds has variable effects on BW and reproduction (Bellows et al., 2001; Alexander et al., 2002; Funston et al., 2002). Many ranching operations in the Southern Great Plains region of the United States use an interval feeding strategy to deliver protein supplements to beef cows. The use of whole oilseeds has not been evaluated in the context of an interval feeding system. Thus, our primary objective was to determine the effects of interval-feeding whole high-linoleic acid sunflower seeds during mid to late gestation on performance of beef cows and their progeny. Studies with pigs and rats suggest that prepartum diet composition may alter pre-natal development and postnatal body composition (Musser et al., 1999; Poulos et al., 2001). Consequently, a second objective was to determine if lipid supplementation during mid to late gestation would influence carcass characteristics of steer progeny.
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MATERIALS AND METHODS
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This experiment was conducted at the Range Cow Research Center, North Range Unit, located approximately 16 km west of Stillwater, OK, in accordance with an approved Oklahoma State University Animal Care and Use Committee protocol. During the winter of 2001–2002, 144 multiparous, spring-calving Angus x Hereford crossbred beef cows (588 kg of initial BW; 5.6 initial BCS; 4 to 13 yr old) were assigned to 1 of 3 supplements in a completely randomized design. Cows were ranked by BCS and randomly allocated so that BCS was similar across all treatments. The supplementation period was initiated on November 30 and terminated on Feb. 14, 2002, just before the first calf was born. During the 76-d supplementation period, cows were managed as a contemporary group in a single pasture with free-choice access to bermudagrass (Cynodon dactylon) hay, tall-grass prairie hay (Table 1), and a mineral supplement (DM basis: 41.9% NaCl; 9.5% Ca; 8.3% P; 0.3% Mg; 1,039 ppm Cu; 12 ppm Se; and 3,110 ppm Zn). Although hay was the major forage component of the diet during the supplementation period, cows had access to a negligible amount of dormant tall-grass prairie pasture. Diets were formulated to exceed CP requirements for beef cows in late gestation (NRC, 1996).
Supplements (DM basis) included: 1) 0.68 kg of soybean meal/feeding (NCON); 2) 3.01 kg of a soybean hull-based supplement/feeding (PCON); and 3) 1.66 kg of whole, high-linoleic acid sunflower seeds/feeding (WSUN; 22% CP; 44% ether extract, which was 58% linoleic acid and 22% oleic acid). The NCON and PCON supplements were fed as 0.64-cm diam. pellets. Supplements were formulated to provide similar amounts of CP and ruminally degraded intake protein (Table 2). In addition, PCON was formulated to be isocaloric to WSUN. Nutritive value of the supplements was estimated using NRC (2001) tabular values. Fatty acid methyl esters were analyzed using an HP6890 (Hewlett-Packard, San Fernando, CA) gas chromatograph equipped with an HP7673A (Hewlett-Packard) automatic sampler, as described by Duckett et al. (2002).
Each cow was fed its appropriate supplement in an individual stall on Monday, Tuesday, Thursday, and Saturday mornings. The amount of supplement fed on each of these 4 d was determined by calculating the amount of supplement needed per week (daily supplement amount x 7 d) and dividing that amount by 4 (e.g., cows receiving WSUN were fed 1.66 kg/feeding). This interval feeding strategy is a common practice among cow/calf producers in Oklahoma. Sunflower seeds were fed whole, rather than cracked or ground. Our assumption was that by feeding the seeds whole, release of oil from the seeds would be slowed to some extent (Coppock and Wilks, 1991), offsetting some of the potential detrimental effects of the interval feeding strategy. These potential detrimental effects may include reduced forage intake and fiber digestion associated with high lipid consumption (Byers and Schelling, 1988). After the 76-d supplementation period, all cows were managed as a contemporary group and were given the mineral supplement described above and free access to bermudagrass pasture or tall-grass prairie pasture.
Individual cow BW and BCS was determined at the beginning and end of the supplementation period (Nov. 30, 2001, and Feb. 14, 2002, respectively), at the onset of breeding (May 9, 2002), and at weaning (Oct. 14, 2002). Cows were weighed 16 h after withdrawal from feed and water. Body condition scores (1 = emaciated, 9 = obese) were assigned by the same 2 independent evaluators throughout the experiment.
Early and mid lactation milk production were determined using the weigh-suckle-weigh technique. The cows that calved earliest from each supplement group were used to determine milk production; the same cows were used to determine early and mid lactation milk production. At 1630 on d 131 and 200 of the experiment, 21 cows each from NCON and PCON and 20 cows from WSUN and their calves were gathered, and the calves were separated from their dams. The cows were returned to the pasture to graze, but the calves were held in pens until 0730 the following morning, at which time the calves were allowed to suckle their dams until all calves stopped suckling. After this initial suckling period, the calves were again separated, and 24-h milk production was measured using 3 consecutive 8-h weigh-suckle-weigh periods (0800 to 1600, 1600 to 0000, and 0000 to 0800). After each 8-h separation period, the calves were weighed and then immediately returned to their dams for suckling. The calves were allowed to suckle for approximately 15 min. Once the calves stopped suckling, they were immediately weighed again. Milk production was determined by subtracting each 8-h prenursing BW from the postnursing BW and summing the three 8-h milk production estimates. When not being suckled, cows were given access to tall-grass prairie pasture or hay.
Early lactation milk composition was determined on Apr. 4, 2002, using 5 cows each per supplement treatment (average calf age = 31 d, range = 24 to 37 d). Cows were separated from their calves at 2000 and allowed to graze until 0800 the following morning. Before milking, a 1.0-mL injection of oxytocin (20 USP units/mL, i.m.; Phoenix Pharmaceutical Inc., St. Joseph, MO) was administered to each cow to facilitate milk let-down. Cows were then individually milked using a portable milking machine. Total milk from the 4 quarters was mixed; a sample of approximately 40 mL was then mixed with a Broad Spectrum Microtab II (D & F Control Systems Inc., Sam Ramon, CA) and sent to the Heart of America DHIA (Manhattan, KS) for analysis of milk urea N, protein, butterfat, lactose, solids not fat, and somatic cell count.
The 72-d calving season lasted from Feb. 14 to Apr. 25, 2002 (average calving date: March 6, 2002). Birth weight of each calf was determined within 24 h of birth, and all bull calves were castrated at this time. The percentage of cows exhibiting luteal activity at the beginning of the breeding season was determined by quantifying progesterone concentration (Vizcarra et al., 1997) in plasma samples collected 9 d before and again on the first day of the breeding season. Blood samples were collected via coccygeal venipuncture, and the collection tubes were immediately placed in ice. Cows with 1 or more plasma samples containing 
0.5 ng of progesterone/mL were considered to have luteal activity.
Cows were artificially inseminated from May 9 through June 5, followed by natural mating from June 6 through July 15, which resulted in a 67-d breeding season. During the AI period, cows were observed each morning and evening for 1 h to detect standing estrus. All cows exhibiting standing estrus were artificially inseminated approximately 12 h after estrus observation. Artificial insemination conception rate was determined using only data from cows that were serviced during the AI period, and the date of conception was based on calving date the following year. Final pregnancy rate was determined by rectal palpation at weaning. At weaning (October 14; average calf age = 222 d), calves were weighed immediately after being separated from their cows. Neither feed nor water was restricted before weighing.
Fifteen days after weaning, all steer calves (n = 24, 24, and 22, respectively, for NCON, PCON, WSUN) were transported to the Willard Sparks Beef Research Center, Stillwater, OK, to determine the effects of mid to late gestation cow supplement composition on subsequent feedlot performance and carcass characteristics of the offspring. Steers were assigned to 1 of 2 blocks based on BW, and within block were randomly assigned to pens based on the supplement fed to their dam. A total of 18 pens were used, with 6 pens per treatment (4 pens per treatment for the heavy BW block; 2 pens per treatment for the light BW block). Four steers were housed in each pen with the exception of 2 WSUN pens containing only 3 steers.
Steers were fed for an average of 188 d until slaughter. A dry-rolled corn-based finishing diet, as described by Krehbiel et al. (2004), was fed from d 36 until slaughter. Steers were implanted with Component E-S (Vet-Life, West Des Moines, IA) on d 0 and Revalor-S (Intervet Inc., Millsboro, DE) on d 98 of the finishing period. Steers from the heavy block and light block were slaughtered on d 181 and 202, respectively. Steers were slaughtered at IBP (Emporia, KS) and chilled for 24 h before collection of data for HCW, 12th rib fat thickness, LM area, KPH, and marbling score. Yield grade was calculated as described by Field and Taylor (2003).
Statistical Analysis
Individual animal was the experimental unit because supplements were fed to each cow individually. Continuous data were analyzed using the MIXED procedure of SAS (SAS Inst. Inc., Cary, NC). The model for cow performance included supplement as a fixed effect and cow age as a covariate. The models for milk production included supplement and calf sex as fixed effects; cow and calf age were included as covariates. The model for milk composition was the same as the milk production models, except that calf sex was not included. The model for calf performance included supplement and calf sex as fixed effects and calf sire as a random effect. Cow age was included as a covariate in all the calf performance models, and calf age was included as a covariate in the weaning weight model. The model for days from calving to the beginning of the breeding season and days from calving to first AI date included supplement as a fixed effect. The model for feedlot performance and carcass characteristics of steer progeny included cow supplement as a fixed effect and sire and block as random effects; covariates included cow age and calf age at slaughter. When the P-value for the F-statistic was 
0.05, least squares means were separated and reported using the LSD procedure of SAS ( = 0.05).
Proportional data were analyzed using the FREQ procedure of SAS. A 2 x 3 contingency table was developed for differences among supplements for percentage of cows exhibiting luteal activity, first service conception rate, and final pregnancy rate. These variables were tested using a 
2 analysis. The SE for proportional data was calculated as: 
P(1–P)/n, where P = the proportion of the variable in question (M. Payton, Department of Statistics, Oklahoma State University, Stillwater, personal communication).
For various reasons (failure to calve, n = 1; cow injury or illness, n = 4; severe mastitis, n = 1), data from 6 cows and their calves were removed from the experiment. No relationship was apparent between any of these factors and the composition of the late-gestation supplement. Only data from the 138 cows that weaned a calf in October were used for statistical analysis.
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RESULTS AND DISCUSSION
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On occasion, cows fed WSUN did not completely consume their allotted supplement. Of the total feeding events (feeding events = number of cows per supplement x 43 feedings), cows fed WSUN did not consume all of their supplement 5.9% of the time, resulting in average estimated consumption of WSUN supplement of 0.92 kg/d rather than 0.95 kg/d as intended (Table 2
). In contrast, cows fed NCON and PCON did not completely consume their supplement 0.3 and 0.2% of the time, respectively, resulting in supplement intake that was similar to the intended amount. There was no consistent pattern in partial supplement refusal among WSUN-supplemented cows; partial supplement refusal was stratified across all cows assigned to that treatment and across all feeding days.
Cow Weight and BCS
During the 76-d supplementation period, cows fed PCON gained 10 kg more BW than cows fed NCON (P < 0.01) and 23 kg more BW than cows fed WSUN (P < 0.01; Table 3). However, from the end of the supplementation period to the beginning of the breeding season, cows fed WSUN lost 12 kg less BW than cows fed PCON (P < 0.01; Table 3). From the beginning of the breeding season until weaning, cow BW change was not different among treatments (P = 0.54; Table 3). Although differences in BW change were observed during certain time periods, mean BW change during the entire 318-d experiment was not different (P = 0.43) among treatments (–51 kg; beginning of supplementation to weaning; Table 3). During the 76-d supplementation period, changes in BCS followed the same pattern as changes in BW. Cows fed PCON lost less body condition than cows fed WSUN (P < 0.01) or NCON (P = 0.04; Table 3). Changes in BCS from the end of the supplementation period to the beginning of the breeding season (P = 0.29), from the beginning of the breeding season to weaning (P = 0.07), and during the entire experiment (P = 0.26) were similar among supplement treatments (Table 3). Final BCS at weaning was not different among supplement treatments (P = 0.08; Table 3), although a trend existed for cows fed WSUN to have lower BCS.
Differences in cow BW and BCS change during gestation may be due to reduced forage intake or digestion by cows fed sunflower seeds (Jenkins, 1993). Given an average cow BW of 583, 590, and 589 kg, and assuming hay intake of 1.7% of BW (Johnson et al., 2003), the diets would have contained approximately 2.0, 2.0, and 5.7% dietary lipid for NCON, PCON, and WSUN, respectively. These values assume constant availability of dietary lipid across all feeding and nonfeeding days. Lipid consumption on feeding days only was approximately 8% of daily DMI for cows fed WSUN. Decreased fiber digestion is typically experienced when total lipid content of a forage-based diet exceeds 5% (Byers and Schelling, 1988; Whitney et al., 2000). Moreover, in the current experiment, most of the supplemental lipid was in the form of unsaturated fatty acids (C 18:2 and C 18:1), which have been shown to inhibit ruminal fermentation to a greater extent than SFA sources (Palmquist and Jenkins, 1980; Chalupa et al., 1984). In contrast to our results, Bellows et al. (2001) did not observe a difference in BW or BCS change of cows fed cracked sunflower or high-linoleic acid safflower seeds daily to provide 5.1% dietary fat compared with a control diet containing 2.4% dietary fat. Perhaps reduced cow performance of cows fed WSUN during the treatment period may be attributed to or exacerbated by high fat consumption in concert with the interval feeding strategy.
Milk Production and Composition
A supplement x calf sex interaction was detected for early lactation milk production (P = 0.03) but not for mid lactation milk production (P = 0.44). This interaction was due to reduced milk production by cows rearing steer calves that were fed WSUN compared with those fed NCON (P = 0.01) and PCON (P < 0.01; 5.4 vs. 7.2 and 7.7 kg/d, respectively). Milk production was not different (P = 0.65) among cows fed supplement treatments that were rearing heifer calves (data not shown). Because calf sex did not determine how the cows were managed and no biological explanation for this difference is apparent, only main effect means for supplements are reported in Table 4 and discussed hereafter. The source of supplement did not influence early lactation (6.7 kg/d) or mid lactation (6.7 kg/d) milk production. Additionally, source of supplement did not alter (P = 0.16 to 0.68) concentrations of milk urea N, crude protein, butterfat, lactose, solids not fat, or somatic cell count (Table 5).
Few reports are available in which milk production and composition have been evaluated in beef cows fed lipid supplements during mid to late gestation. Alexander et al. (2002) found no differences in milk yield or milk fat concentration when cows were fed 2 different sources of dietary fat during a 60-d prepartum period, compared with cows fed an isoenergetic control supplement. Considering that milk production was first measured 55 d after supplementation had ceased, it was not surprising that no supplement effects were observed for milk production or milk composition.
Calf Performance
No supplement x calf sex interaction was observed for calf birth (P = 0.64) or weaning weight (P = 0.87). Additionally, neither calf birth (36 kg) nor weaning weight (235 kg) was significantly influenced by composition of supplement fed during gestation (Table 6). Differences in weaning weight would not be expected because milk production and composition were not altered by supplement treatment. In a review of the literature, Hess et al. (2002) concluded that prepartum lipid supplementation did not influence calf birth or weaning weight.
Cow Reproductive Performance
No significant differences in days from calving to the beginning of the breeding season (63 d) or percentage of cows exhibiting luteal activity at the beginning of the breeding season (57%) were observed among treatments (Table 7). However, AI conception rate was greatest (P < 0.01) for cows fed PCON (79%) and tended to be greater (P = 0.07) for cows fed WSUN (74%) compared with cows fed NCON (53%). No difference in AI conception rate was observed between cows fed PCON and cows fed WSUN (P = 0.55). Although AI conception rate tended to be greater for PCON and WSUN compared with NCON, no difference (P = 0.44) in final pregnancy rate (88%) was observed among cows fed different supplements (Table 7).
Among the few available reports with adequate experimental units to evaluate reproductive performance of beef cows, the effects of supplemental dietary fat during gestation have been inconsistent. Others have reported no difference in percentage of cows exhibiting luteal activity at the beginning of the breeding season (Bellows et al., 2001; Alexander et al., 2002) and no difference in pregnancy rates (Alexander et al., 2002) for cows fed prepartum lipid treatments compared with control cows. Funston et al. (2002) found no difference in pregnancy rate to AI for heifers fed whole sunflower seeds for 30 or 60 d prebreeding compared with control heifers. Prepartum supplementation of a high-fat range supplement did not significantly improve first service conception rate (Alexander et al., 2002). However, Graham et al. (2001) reported that first service conception was greater for cows fed whole soybeans prepartum compared with cows fed an isocaloric control supplement. Bellows et al. (2001) observed that pregnancy rate was increased for cows fed whole soybeans prepartum. A distinguishing characteristic of the current experiment is that cows fed WSUN and NCON had greater prepartum BCS loss than cows fed PCON, whereas cows fed WSUN maintained similar AI conception rate to cows fed PCON. This suggests a positive carryover effect on conception, independent of prepartum energy balance, associated with feeding WSUN prepartum. Improved conception rate could be attributed to the ability of lipid supplementation to modify follicular growth, to increase the life span of the corpus luteum, or both (Staples et al., 1998; Williams and Stanko, 2000). However, at parturition, BCS was >5 across all treatment groups. Morrison et al., (1999) concluded that prepartum changes in body energy reserves did not influence reproductive performance as long as cows calved with moderate BCS. Moreover, when pre-and postpartum BW and BCS changes were considered together, prebreeding changes in energy reserves were minimal among treatments. In this context, one might conclude that prepartum energy supplementation can influence AI conception rate even in the absence of substantial changes in energy reserves up to the beginning of the breeding season.
Feedlot Performance and Carcass Characteristics of Steers
Feedlot performance and carcass characteristics of steer progeny were not influenced by supplements fed to dams during gestation (Table 8). Steers in this experiment may have been fed longer than desired for detecting differences in marbling score or fat deposition as indicated by average fat thickness over the 12th rib (1.60 cm). However, when steers having more than 1.78 cm of 12th rib fat were removed from the data set, no significant differences in feedlot performance or carcass characteristics were observed among progeny of cows fed different supplements during late gestation (data not shown). We are not aware of other studies that have examined the effects of prepartum lipid supplementation of beef cows on carcass characteristics of their progeny.
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Table 8. Effect of mid to late gestation supplement on feedlot performance and carcass characteristics of steer progeny
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IMPLICATIONS
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In a system requiring an interval feeding strategy, supplemental protein and energy from whole sunflower seeds may not be as effective in maintaining mid to late gestation energy reserves compared with supplemental protein and energy from more traditional sources. However, reduced body weight gain during mid to late gestation for cows fed whole sunflower seeds did not affect cow reproduction or calf performance.
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Footnotes
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1 Approved for publication by the director of the Oklahoma Agric. Exp. Stn. This research was supported under project H-2464. 
2 The authors would like to thank J. Steele, D. Williams, and the staff at the Willard Sparks Beef Research Center for the care and daily management of the cattle used in this study.
3 Corresponding author: david.lalman{at}okstate.edu
Received for publication July 25, 2005.
Accepted for publication April 24, 2006.
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LITERATURE CITED
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Alexander, B. M., B. W. Hess, D. L. Hixon, B. L. Garrett, D. C. Rule, M. McFarland, J. D. Bottger, D. D. Simms, and G. E. Moss. 2002. Influence of prepartum fat supplementation on subsequent beef cow reproduction and calf performance. Prof. Anim. Sci. 18:351–357.
Bellows, R. A., E. E. Grings, D. D. Simms, T. W. Geary, and J. W. Bergman. 2001. Effects of feeding supplemental fat during gestation to first-calf beef heifers. Prof. Anim. Sci. 17:81–89.
Byers, F. M., and G. T. Schelling. 1988. Lipids in ruminant nutrition. Pages 298–312 in The Ruminant Animal: Digestive Physiology and Nutrition. D. C. Church ed. Waveland Press Inc., Englewood Cliffs, NJ.
Chalupa, W., B. Rickabaugh, D. S. Kronfeld, and D. Sklan. 1984. Rumen fermentation in vitro as influenced by long chain fatty acids. J. Dairy Sci. 67:1439–1444.[Abstract/Free Full Text]
Coppock, C. E., and D. L. Wilks. 1991. Supplemental fat in high-energy rations for lactating cows: Effects on intake, digestion, milk yield, and composition. J. Anim. Sci. 69:3826–3837.[Abstract]
Duckett, S. K., J. G. Andrae, and F. N. Owens. 2002. Effect of high-oil corn or added corn oil on ruminal biohydrogenation of fatty acids and conjugated linoleic acid formation in beef steers fed finishing diets. J. Anim. Sci. 80:3353–3360.[Abstract/Free Full Text]
Field, T. G., and R. E. Taylor. 2003. Page 244 in Beef Production & Management decisions. 4th ed. Pearson Education Inc., Upper Saddle River, NJ.
Funston, R. N., T. W. Geary, R. P. Ansotegui, R. J. Lipsey, and J. A. Patterson. 2002. Supplementation with whole sunflower seeds before artificial insemination in beef heifers. Prof. Anim. Sci. 18:254–257.
Graham, K. K., J. F. Bader, D. J. Patterson, M. S. Kerley, and C. N. Zumbrunnen. 2001. Supplementing whole soybeans prepartum increases first service conception rate in postpartum suckled beef cows. J. Anim. Sci. 79(Suppl.2):106. (Abstr.)
Hess, B. W., D. C. Rule, and G. E. Moss. 2002. High fat supplements for reproducing beef cows: Have we discovered the magic bullet? 2002 Pacific Northwest Animal Nutrition Conference. Available: http://www.dsm.com/en_US/downloads/dnpus/PNW_02_10.pdf Accessed Jan. 31, 2005.
Jenkins, T. C. 1993. Lipid metabolism in the rumen. J. Dairy Sci. 76:3851–3863.[Abstract/Free Full Text]
Johnson, C. R., D. L. Lalman, M. A. Brown, L. A. Appeddu, D. S. Buchanan, and R. P. Wettemann. 2003. Influence of milk production potential on forage dry matter intake of multiparous and primiparous Brangus females. J. Anim. Sci. 81:1837–1846.[Abstract/Free Full Text]
Krehbiel, C. R., R. E. Peterson, L. J. McBeth, J. P. Banta, D. L. Lalman, D. L. Step, H. DePra, C. E. Markam, D. R. Gill, and R. L. Ball. 2004. Effect of an isolated soy protein by-product on finishing cattle performance and carcass characteristics. Available: http://www.ansi.okstate.edu/research/2004rr/05/05.htm Accessed July 19, 2005.
Morrison, D. G., J. C. Spitzer, and J. L. Perkins. 1999. Influence of prepartum body condition score change on reproduction in multiparous beef cows calving in moderate body condition. J. Anim. Sci. 77:1048–1054.[Abstract/Free Full Text]
Musser, R. E., S. S. Dritz, R. D. Goodband, M. D. Tokach, D. L. Davis, J. L. Nelssen, K. Q. Owen, R. E. Campbell, S. Hanni, J. S. Bauman, and M. Heintz. 1999. Additional L-carnitine in the gestating sow diet improves carcass characteristics of the offspring. Pages 37–40 in Swine Day 1999, Kansas State Univ., Manhattan. Available: http://www.oznet.ksu.edu/library/lvstk2/srp841.pdf Accessed Jan. 18, 2005.
NRC. 1996. Nutrient Requirements of Beef Cattle. 7th rev. ed. Natl. Acad. Press, Washington, DC.
NRC. 2001. Nutrient Requirements of Dairy Cattle. 7th rev. ed. Natl. Acad. Press, Washington, DC.
Palmquist, D. L., and T. C. Jenkins. 1980. Fat in lactation rations: Review. J. Dairy Sci. 63:1–14.[Abstract/Free Full Text]
Poulos, S. P., M. Sisk, D. B. Hausman, M. J. Azain, and G. J. Hausman. 2001. Pre- and postnatal dietary conjugated linoleic acid alters adipose development, body weight gain and body composition in Sprague-Dawley rats. J. Nutr. 131:2722–2731.[Abstract/Free Full Text]
Staples, C. R., J. M. Burke, and W. W. Thatcher. 1998. Influence of supplemental fat on reproductive tissues and performance of lactating cows. J. Dairy Sci. 81:856–871.[Abstract]
Vizcarra, J. A., R. P. Wettemann, T. D. Braden, A. M. Turzillo, and T. M. Nett. 1997. Effect of gonadotropin-releasing hormone (GnRH) pulse frequency on serum and pituitary concentrations of luteinizing hormone and follicle-stimulating hormone, GnRH receptors, and messenger ribonucleic acid for gonadotropin subunits in cows. Endocrinology 138:594–601.[Abstract/Free Full Text]
Whitney, M. B., B. W. Hess, L. A. Burgwald-Balstad, J. L. Sayer, C. M. Tsopito, C. T. Talbott, and D. M. Hallford. 2000. Effects of supplemental soybean oil level on in vitro digestion and performance of prepubertal beef heifers. J. Anim. Sci. 78:504–514.[Abstract/Free Full Text]
Williams, G. L., and R. L. Stanko. 2000. Dietary fats as reproductive nutraceuticals in beef cattle. Proc. Amer. Soc. Anim. Sci. 1999. Available at: http://www.asas.org/jas/symposia/proceedings/0915.pdf Accessed Jan. 31, 2005.
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Abstract
INTRODUCTION
