Bos Indicus-influenced Cattle Research Articles

24 Effects of Gestational and Postweaning Nutrition on Brain Development and Puberty in Beef Heifers

Abstract Approximately 5 million beef heifers enter the U.S. cow herd annually, and their lifetime productivity is largely dependent upon their ability to attain puberty and produce a calf by 24 mo of age. However, a considerable proportion of heifers within existing U.S. production systems fail to achieve these goals, particularly in southern regions where Bos indicus-influenced cattle predominate. Consequently, managerial approaches are needed that employ nutritional programming of the reproductive neuroendocrine axis, while minimizing feeding costs and optimizing the consistent attainment of puberty by approximately 14 mo of age. Our previous research has clearly demonstrated that increased BW gain between 4 and 8 mo of age facilitates pubertal development by programming hypothalamic centers that regulate gonadotropin releasing-hormone (GnRH) secretion. Among the different metabolic hormones, leptin has a critical role in conveying nutritional information to the hypothalamus and controlling puberty. Two hypothalamic neuronal populations that express the orexigenic peptide neuropeptide Y (NPY) and the anorexigenic peptide alpha melanocyte-stimulating hormone (αMSH; a product of the POMC gene) are key components of afferent pathways that convey inhibitory (NPY) and excitatory (αMSH) inputs to GnRH and kisspeptin neurons. Our studies have demonstrated that short-term increases in dietary energy intake after early weaning at 4 mo of age result in epigenetic, structural, and functional modifications in these hypothalamic pathways to promote high-frequency, episodic release of GnRH and luteinizing hormone. However, integrating the foundational knowledge of metabolic imprinting of the brain for early puberty with issues related to lifetime performance is complex. One approach has been to employ a novel stair-step nutritional regimen involving alternating periods of dietary energy-restriction and re-feeding during juvenile development. This approach is designed to support early onset of puberty by imprinting functional alterations in the hypothalamus during key periods of brain development while optimizing other aspects of growth and performance. Finally, while several key processes of fetal brain development occur during late gestation, neither maternal undernutrition (BCS 3.0-3.5) nor maternal obesity (BCS 7.5-8.0) during the last two trimesters of gestation impacted the organization of hypothalamic neurocircuitries controlling GnRH/LH secretion or age at puberty in the heifer offspring. Collectively, these results indicate that the adult reproductive phenotype in Bos indicus-influenced females is resilient to significant degrees of nutritional stress imposed during prenatal development, particularly if early gestation (first trimester) is avoided. These findings are in contrast with reports in Bos taurus females in which late gestation nutritional extremes result in delayed puberty in heifer offspring, suggesting that potential genotype-specific differences may exist. Research support: USDA-NIFA-AFRI (2018-67015-27595 and 2021-67015-33676).

Lysolecithin-derived feed additive improves feedlot performance, carcass characteristics, and muscle fatty acid profile of Bos indicus-influenced cattle fed in a tropical environment.

Lysolecithin might increase ruminal and intestinal emulsification, leading to increased digestibility, but there is minimum information about which is the most appropriate phase to start supplementation and its impacts on feedlot performance and muscle fatty acid profile. Two experiments were conducted to evaluate the effects of phase-feeding of Lysoforte™ eXtend (LYSO). In the first experiment, 1,760 predominantly Bos indicus bullocks (initial body weight of 400 ± 0.561 kg) were allocated in a complete randomized block design. LYSO was supplemented at 1 g/1% of ether extract from the diet. Treatments were no LYSO supplementation (NON); LYSO starting during the growing period and continuing during the finishing period; LYSO starting during the finishing period (FIN); and LYSO during adaptation, growing, and finishing periods (ALL). In the second experiment, the same treatments were evaluated with 96 bullocks (64 Nellore and 32½ Nellore × ½ Angus) in a 4 × 2 factorial arrangement (treatments × genotype). For both studies, intake and average daily gain were accessed; carcass characteristics were evaluated in the first experiment, while digestibility of nutrients and profile of muscle fatty acids were measured in the second experiment. In the first experiment, LYSO increased final body weight (P < 0.022) and average daily gain (GRO and FIN; P < 0.05). In the second study, a treatment × breed × feeding phase interaction was observed with Nellore having a greater average daily gain (P < 0.05) than crossbreds in every feeding phase that LYSO was introduced to the diet. A treatment × feeding phase interaction was observed for digestibility, such that LYSO increased total dry matter (P = 0.004), crude protein (P = 0.043), and NDF (P = 0.001) digestibility during the finishing period. A treatment × breed × day classification was observed (P < 0.05). During the finishing phase, crossbreds treated with LYSO had greater DMI (P < 0.05) on very hot days than NON. Also, animals treated with LYSO presented a greater C18:3 n3 concentration (P = 0.047) in the longissimus. Overall, feeding LYSO during GRO and FIN enhanced feedlot performance and should lead to higher intakes during very hot days of the finishing feeding period.

Connecting Heat Tolerance and Tenderness in Bos indicus Influenced Cattle.

Simple SummaryBos indicus (also known as zebu or humped) cattle are heat tolerant and parasite resistant, which is advantageous in hot, humid climates. However, Bos indicus cattle are also known for excitable temperaments, slower growth, and variation in meat quality characteristics. The relationships between thermotolerance, temperament, and meat production traits are poorly understood. Due to its contribution to body weight, muscle may play an important role in determining the thermoregulatory capacity of Bos indicus cattle. Ultimately, defining relationships between muscle metabolism and heat tolerance are necessary in order to enhance tenderness, without sacrificing heat tolerance of Bos indicus breeds.Bos indicus cattle are widely utilized in tropical and subtropical climates. Their heat tolerance and parasite resistance are integral for beef production in these regions; however, a reputation for excitable temperaments, slower growth, and variation in tenderness has limited their use in commercial beef production. This suggests that there is antagonism between heat tolerance and meat production traits. Meat quality characteristics are determined by the properties of skeletal muscle as well as conditions during slaughter and processing. Thus, it is possible that adaptations related to heat tolerance in the living animal affect tenderness and other meat quality attributes. Since muscle represents a large proportion of body mass, relatively small changes at the cellular level could impact overall heat production of the animal. Specifically, protein degradation and mitochondria function are aspects of organ and cellular metabolism that may help limit heat production and also have a connection to tenderness. Protein degradation postmortem is critical to structural changes that enhance tenderness whereas mitochondria may influence tenderness through their roles in energy metabolism, calcium regulation, cell death signaling, and oxidative stress. This review explores potential relationships between cellular metabolism in vivo and beef quality development in Bos indicus and Bos indicus influenced cattle.

Cattle adapted to tropical and subtropical environments: social, nutritional, and carcass quality considerations.

Beef production needs to increase from 60 million to 130 million tons by 2050 to feed a growing world population, and 70% of this production increase is expected from beef industries located in subtropical and tropical regions of the world. Bos indicus-influenced cattle predominate in these regions but are often managed using practices developed for Bos taurus breeds reared in temperate climates. Hence, a fundamental step to meet the increasing global demand for beef is to develop specific management for B. indicus-influenced cattle in tropical or subtropical environments. Bos taurus and B. indicus are different subspecies, and diverge in social and biological functions due to selection pressure caused by complex evolutionary and domestication processes. Bos indicus cattle display different social responses compared with B. taurus counterparts, which must be taken into account by management planning as these traits directly impact cattle performance and welfare. In tropical and subtropical regions, warm-season perennial C4 grasses are the dominant forages, and their availability has a significant influence on the productivity of beef cattle systems. The resilience of C4 grasses under adverse conditions is one of their most important characteristics, even though these forages have reduced nutritive value compared with forages from temperate climates. Accordingly, nutritional planning in tropical and subtropical conditions must include management to optimize the quantity and quality of C4 forages. Nutritional requirements of cattle raised within these conditions also require special attention, including inherent metabolic compromises to cope with environmental constraints and altered energy requirements due to body composition and heat tolerance. Nutritional interventions to enhance beef production need to be specifically tailored and validated in B. indicus-influenced cattle. As an example, supplementation programs during gestation or early life to elicit fetal programming or metabolic imprinting effects, respectively, yield discrepant outcomes between subspecies. Bos indicus-influenced cattle produce carcasses with less marbling than B. taurus cattle, despite recent genetic and management advances. This outcome is mostly related to reduced intramuscular adipocyte volume in B. indicus breeds, suggesting a lesser need for energy stored intramuscularly as a mechanism to improve thermotolerance in tropical and subtropical climates.

Cattle adapted to tropical and subtropical environments: genetic and reproductive considerations

Efforts to understand biological functions and develop management schemes specific to Bos indicus-influenced cattle raised in tropical and subtropical environments are critical to meet the increasing global demand for protein. In the United States, B. indicus breeds are mostly used to generate B. indicus × B. taurus crosses with increased thermal and parasite tolerance, while retaining some productive characteristics of B. taurus cattle. Although crossbreeding represents a proven strategy to improve cattle adaptation almost immediately, research has also attempted to identify B. taurus genetics that can withstand subtropical and tropical climates. Reduced milk production and delayed reproductive maturation appear to be related with tropical adaptation of B. taurus breeds, as a means to conserve energy under stressful conditions and limited nutrition. Moreover, longevity may be the ultimate adaptation response to unfavorable environments, and retention of bulls and heifers from proven cows is the recommended strategy to improve longevity in B. indicus-influenced herds. Besides selection for longevity, other aspects should be considered when planning reproductive management in tropical and subtropical regions. Bos indicus and B. taurus breeds have multiple differences pertaining to reproductive function, including age at puberty, ovarian dynamics, and pregnancy development. Nutritional strategies such as the stair-step regimen, and use of exogenous progesterone (P4) inserts are options to hasten puberty attainment of late-maturing B. indicus-influenced heifers. Yet, limited pharmacological alternatives are available for reproductive management of B. indicus-influenced females in the United States, which rely on GnRH-based protocols not specifically designed to the reproductive function of B. indicus breeds. In contrast, hormonal protocols based on exogenous P4, estradiol esters, and equine chorionic gonadotropin are available for use in B. indicus females in South America. These include protocols tailored to prepubertal heifers, anestrous cows, and cycling nulliparous or parous females, which often yield pregnancy rates of 50% to fixed-time artificial insemination. The global dairy industry also faces similar challenges in increasing demand and production as the beef industry. Selection of cows capable of sustaining optimal milk yield, reproductive success, and health status in hot and humid conditions is essential for optimal dairy production in subtropical and tropical regions.

38 Welfare and behavior considerations for cattle in tropical and subtropical environments

Abstract Bos indicus and B. taurus are two different subspecies that differ in reproductive physiology, nutritional requirements, social behavior, digestive system, and body composition. A fundamental step in meeting the increasing global demand for protein on a planet experiencing climate change while addressing environmental stewardship is to identify management practices optimized for B. indicus-influenced cattle reared in the growing subtropical/tropical regions of the planet. Bos indicus-influenced cattle, are typically managed in subtropical/tropical regions utilizing practices developed and validated for B. taurus breeds in temperate environments. Little is known about the behavioral profile of B. indicus. Bovine Respiratory Disease (BRD), lameness, and bulling are three welfare and productivity issues that require behavioral evaluation to identify and treat. Little is known regarding lameness in feedlot cattle, irrespective of breed, but cattle are prey animals designed to mask illness and pain. Therefore, characterizing species-specific behavioral indicators of discomfort are paramount to early detection and treatment of these afflictions. B. indicus cattle are more gregarious than B. taurus and have more excitable temperaments; thus, they are more susceptible to stress, may have greater difficulty coping, and may be more adept at masking health issues. These cattle display different social behaviors compared to B. taurus counterparts, which may contribute to differences in production efficiency and outcomes. Gaining an understanding of the behavioral and social aspects of these animals, and understanding their biological thresholds regarding thermoregulation, disease resistance, transportation resiliency, and the human-animal interaction will provide foundational data for developing appropriate stewardship practices. Beef cattle, irrespective of what sector they are managed (e.g., feedlot, cow-calf, pasture housed), are directly affected by weather. Therefore, as the climate changes, we must begin to increase our use of animals that are better suited to these environmental conditions, and within that framework increase our understanding of their species-specific welfare needs.

33 Nutritional programming of puberty in Bos indicus-influenced heifers

Abstract Approximately 5 million beef heifers enter the U.S. cow herd annually and their lifetime productivity is heavily-dependent upon their ability to attain puberty and produce a calf by 24 mo of age. However, a significant proportion of heifers within existing U.S. production systems fail to achieve these goals, particularly in southern regions where Bos indicus-influenced cattle predominate. Therefore, approaches are needed that facilitate nutritional programming of the reproductive neuroendocrine axis, while minimizing feeding costs and optimizing the consistent establishment of puberty by 14–15 mo of age. Increased BW gain between 4 and 9 mo of age facilitates pubertal development by programming hypothalamic centers that regulate GnRH secretion. Among the different metabolic hormones, leptin plays a critical role in conveying nutritional information to the brain and controlling puberty. Two hypothalamic neuronal populations that express the orexigenic peptide neuropeptide Y (NPY) and the anorexigenic peptide alpha melanocyte-stimulating hormone (αMSH) are key components of afferent pathways that convey inhibitory (NPY) and excitatory (αMSH) inputs to GnRH neurons. Our studies have demonstrated that short-term increases in dietary energy intake during juvenile development result in epigenetic, structural, and functional modifications in these hypothalamic pathways to promote high-frequency, episodic release of GnRH/LH. However, integrating the foundational knowledge of metabolic imprinting of the brain for early puberty with issues related to lifetime performance is complex. One approach has been to employ a novel stair-step nutritional regimen involving alternating periods of dietary energy-restriction and re-feeding during juvenile development. This approach is designed to support early onset of puberty by imprinting functional alterations in the hypothalamus during key periods of brain development while optimizing other aspects of growth and performance. Finally, our recent findings suggest that maternal nutrition during gestation can also induce neuroendocrine changes that are likely to persist and influence reproductive performance throughout adulthood in cattle.

Technologies for fixed-time artificial insemination and their influence on reproductive performance of Bos indicus cattle

The adaptation of Bos indicus cattle to tropical and subtropical environments has led to their widespread distribution around the world. Although artificial insemination (AI) is one of the best alternatives to introduce new genetics into Bos indicus herds, the peculiarity of their temperament and the tendency to show short oestrus (many of them during the night) greatly affects the effectiveness of genetic improvement programs. Therefore, the most useful alternative to increase the number of females that are inseminated is the use of protocols that allow for AI without the need for oestrus detection, usually called fixed-time AI (FTAI). Besides, the development of protocols to advance the resumption of cyclicity during the early postpartum period has a great impact on beef production and will allow for the inclusion of a significantly larger population of animals into genetic improvement programs. Fixed-time AI protocols using progestin devices, oestradiol and eCG have resulted in consistent pregnancy rates in suckled Bos indicus and Bos indicus × Bos taurus cows. Furthermore, fertility in the successive cycles and the overall pregnancy rates at the end of the breeding season, have been shown to be improved by the use of progestin devices at the beginning of the breeding season. In summary, exogenous control of luteal and follicular development has facilitated the application of assisted reproductive technologies in Bos indicus-influenced cattle, by offering the possibility of planning programs without the necessity of oestrus detection and may provide the opportunity to improve reproductive performance of beef cattle in tropical climates.

Is Blade Tenderization Still Needed for Inherently Tender Top Sirloin Steaks?

ObjectivesAlthough blade tenderization has historically been used to enhance tenderness, it may create a food safety concern. Therefore, the objective of this study was to determine if consumer satisfaction improves by blade tenderizing today’s inherently tender beef.Materials and MethodsPaired USDA Choice top sirloin butts (n = 20 total pieces) were collected from 10 carcasses representative of the typical carcass in today’s fed beef market. Carcasses from dairy-type cattle, Bos indicus-influenced cattle, and from cattle over 30 mo of age were not used. No selection preference was given to carcass sex class, weight, or presence or absence of black hide, but excessively heavy or light carcasses that would not yield a representative sample of what today’s consumers call an “average steak” were not selected. Subprimals were subjected to a 28-day refrigerated wet aging period before treatments were administered, with “d 0” defined as the day of carcass fabrication. Top sirloins from the left side of the carcass were blade tenderized once before portioning into steaks, whereas top sirloins from the right side of the carcass received no treatment and served as the control. Paired top sirloin butts were subjected to Warner-Bratzler Shear (WBS) force testing as a measure of objective tenderness. Consumer sensory evaluation was used to determine if consumer liking of tenderness, flavor, juiciness, and overall liking differed for steaks from blade tenderized (BT) subprimals versus those from non-blade tenderized (NBT) subprimals. Steaks were cut into fourths after cooking, with each sample (one-fourth of a steak) presented on a plate along with a metal steak knife and a plastic fork. This serving style allowed panelists to cut into the product, which sometimes influences consumer acceptability. Data were analyzed with paired t-tests using the matched pairs function of JMP (Version 12, SAS Inst. Inc., Cary, NC), at an alpha of 5%.ResultsConsumers assigned BT steaks higher (P < 0.05; Table 1) ratings for tenderness liking rating, flavor liking rating, and overall liking rating compared to NBT steaks. No differences (P > 0.05) were seen for juiciness liking ratings or WBS force values.ConclusionAlthough today’s beef is inherently tender, these data show that blade tenderization improved consumer sensory panel ratings for tenderness, flavor, and overall likeability for beef top sirloin steaks. Therefore, discontinuing the use of blade tenderization could result in less favorable consumer eating experiences.

Bill E. Kunkle Interdisciplinary Beef Symposium: Temperament and acclimation to human handling influence growth, health, and reproductive responses in Bos taurus and Bos indicus cattle.

Temperament in cattle is defined as the fear-related behavioral responses when exposed to human handling. Our group evaluates cattle temperament using 1) chute score on a 1 to 5 scale that increases according to excitable behavior during restraint in a squeeze chute, 2) exit velocity (speed of an animal exiting the squeeze chute), 3) exit score (dividing cattle according to exit velocity into quintiles using a 1 to 5 scale where 1=cattle in the slowest quintile and 5=cattle in the fastest quintile), and 4) temperament score (average of chute and exit scores). Subsequently, cattle are assigned a temperament type of adequate temperament (ADQ; temperament score≤3) or excitable temperament (EXC; temperament score>3). To assess the impacts of temperament on various beef production systems, our group associated these evaluation criteria with productive, reproductive, and health characteristics of Bos taurus and Bos indicus-influenced cattle. As expected, EXC cattle had greater plasma cortisol vs. ADQ cattle during handling, independent of breed type (B. indicus×B. taurus, P<0.01; B. taurus, P<0.01; B. indicus, P=0.04) or age (cows, P<0.01; heifers or steers, P<0.01). In regards to reproduction, EXC females had reduced annual pregnancy rates vs. ADQ cohorts across breed types (B. taurus, P=0.03; B. indicus, P=0.05). Moreover, B. taurus EXC cows also had decreased calving rate (P=0.04), weaning rate (P=0.09), and kilograms of calf weaned/cow exposed to breeding (P=0.08) vs. ADQ cohorts. In regards to feedlot cattle, B. indicus EXC steers had reduced ADG (P=0.02) and G:F (P=0.03) during a 109-d finishing period compared with ADQ cohorts. Bos taurus EXC cattle had reduced weaning BW (P=0.04), greater acute-phase protein response on feedlot entry (P≤0.05), impaired feedlot receiving ADG (P=0.05), and reduced carcass weight (P=0.07) vs. ADQ cohorts. Acclimating B. indicus×B. taurus or B. taurus heifers to human handling improved temperament (P≤0.02), reduced plasma cortisol (P<0.01), and hastened puberty attainment (P≤0.02). However, no benefits were observed when mature cows or feeder cattle were acclimated to human handling. In conclusion, temperament impacts productive, reproductive, and health characteristics of beef cattle independent of breed type. Hence, strategies to improve herd temperament are imperative for optimal production efficiency of beef operations based on B. taurus and B. indicus-influenced cattle.

Deletion on chromosome 5 associated with decreased reproductive efficiency in female cattle1,2,3,4

Reproductive efficiency is arguably the most economically important trait in commercial beef cattle production, as failure to achieve pregnancy reduces the number of calves marketed per cow exposed to breeding. Identification of variation in the genome with predictive merit for reproductive success would facilitate accurate prediction of daughter pregnancy rate in sires enabling effective selection of bulls producing daughters with improved fertility. Copy number variation (CNV) is one form of structural variation that results in abnormal copies of DNA in the genome. Our lab previously reported a region between 25 and 70 Mb on chromosome 5 associated with reproductive efficiency. To further evaluate this region for genomic variations such as CNV, we initially applied a genomewide association approach based on the >700,000 SNP marker assay and PennCNV analysis to 68 Bos indicus cross females from a large commercial ranch in central Florida. A genomic segment located on chromosome 5, spanning the region of approximately 58.37 to 58.44 Mb (Bovine UMD3.1 assembly) was identified as containing a deletion associated with decreased reproductive efficiency. To verify this deletion, a quantitative real-time PCR test was developed to evaluate additional females in the central Florida and U.S. Meat Animal Research Center (USMARC) populations. The frequency of the homozygous deletion was 7% (23/319) in the central Florida population (Bos indicus cross) for females with 2 consecutive failed breeding seasons and 0% in the USMARC population (predominantly Bos taurus) of low reproductive females. To date, we have not identified the deletion in Bos taurus cattle, suggesting that the deletion is specific to Bos indicus cattle. From these data, we have identified a deletion on chromosome 5 associated with reproductive efficiency in Bos indicus-influenced cattle.

Technologies for fixed-time artificial insemination and their influence on reproductive performance of &lt;I&gt;Bos indicus&lt;/I&gt; cattle

The adaptation of Bos indicus cattle to tropical and subtropical environments has led to their widespread distribution around the world. Although artificial insemination (AI) is one of the best alternatives to introduce new genetics into Bos indicus herds, the peculiarity of their temperament and the tendency to show short oestrus (many of them during the night) greatly affects the effectiveness of genetic improvement programs. Therefore, the most useful alternative to increase the number of females that are inseminated is the use of protocols that allow for AI without the need for oestrus detection, usually called fixed-time AI (FTAI). Besides, the development of protocols to advance the resumption of cyclicity during the early postpartum period has a great impact on beef production and will allow for the inclusion of a significantly larger population of animals into genetic improvement programs. Fixed-time AI protocols using progestin devices, oestradiol and eCG have resulted in consistent pregnancy rates in suckled Bos indicus and Bos indicus x Bos taurus cows. Furthermore, fertility in the successive cycles and the overall pregnancy rates at the end of the breeding season, have been shown to be improved by the use of progestin devices at the beginning of the breeding season. In summary, exogenous control of luteal and follicular development has facilitated the application of assisted reproductive technologies in Bos indicus-influenced cattle, by offering the possibility of planning programs without the necessity of oestrus detection and may provide the opportunity to improve reproductive performance of beef cattle in tropical climates.

Ovarian, hormonal, and reproductive events associated with synchronization of ovulation and timed appointment breeding of Bos indicus-influenced cattle using intravaginal progesterone, gonadotropin-releasing hormone, and prostaglandin F2α1

The objectives of this study were to 1) compare cumulative pregnancy rates in a traditional management (TM) scheme with those using a synchronization of ovulation protocol (CO-Synch + CIDR) for timed AI (TAI) in Bos indicus-influenced cattle; 2) evaluate ovarian and hormonal events associated with CO-Synch + CIDR and CO-Synch without CIDR; and 3) determine estrual and ovulatory distributions in cattle synchronized with Select-Synch + CIDR. The CO-Synch + CIDR regimen included insertion of a controlled internal drug-releasing device (CIDR) and an injection of GnRH (GnRH-1) on d 0, removal of the CIDR and injection of PGF2alpha (PGF) on d 7, and injection of GnRH (GnRH-2) and TAI 48 h later. For Exp. 1, predominantly Brahman x Hereford (F1) and Brangus females (n = 335) were stratified by BCS, parity, and day postpartum (parous females) before random assignment to CO-Synch + CIDR or TM. To maximize the number of observations related to TAI conception rate (n = 266), an additional 96 females in which TM controls were not available for comparison also received CO-Synch + CIDR. Conception rates to TAI averaged 39 +/- 3% and were not affected by location, year, parity, AI sire, or AI technician. Cumulative pregnancy rates were greater (P < 0.05) at 30 and 60 d of the breeding season in CO-Synch + CIDR (74.1 and 95.9%) compared with TM (61.8 and 89.7%). In Exp. 2, postpartum Brahman x Hereford (F1) cows (n = 100) were stratified as in Exp. 1 and divided into 4 replicates of 25. Within each replicate, approximately one-half (12 to 13) received CO-Synch + CIDR, and the other half received CO-Synch only (no CIDR). No differences were observed between treatments, and the data were pooled. Percentages of cows ovulating to GnRH-1, developing a synchronized follicular wave, exhibiting luteal regression to PGF, and ovulating to GnRH-2 were 40 +/- 5, 60 +/- 5, 93 +/- 2, and 72 +/- 4%, respectively. In Exp. 3, primiparous Brahman x Hereford, (F1) heifers (n = 32) and pluriparous cows (n = 18) received the Select Synch + CIDR synchronization regimen (no GnRH-2 or TAI). Mean intervals from CIDR removal to estrus and ovulation, and from estrus to ovulation were 70 +/- 2.9, 99 +/- 2.8, and 29 +/- 2.2 h, respectively. These results indicate that the relatively low TAI conception rate observed with CO-Synch + CIDR in these studies was attributable primarily to failure of 40% of the cattle to develop a synchronized follicular wave after GnRH-1 and also to inappropriate timing of TAI/GnRH-2.

Effects of growth implants on consumer perceptions of meat tenderness in beef steers.

Anabolic steroid implants are routinely used to increase growth performance and profitability; however, there are concerns that the use of implants, particularly those containing trenbolone acetate, may have detrimental effects on carcass quality and beef tenderness. Thus, the objectives of the current study were to determine the effects of various commonly used implant regimens on shear force values, sensory properties, and consumer satisfaction of beef top loin steaks from cattle of Bos indicus influence. Cattle were supplied by producers that agreed to provide sire and dam information in exchange for carcass and sensory data. Steers (n = 2,748) were assigned randomly to one of three implant treatments (12/sire; four steers from each sire were placed into each treatment group): 1) unimplanted controls (n = 1,368); 2) Synovex-S followed by another Synovex-S (n = 660); or 3) Synovex-S followed by Revalor-S (n = 720). Steaks sampled after 3, 7, and 14 d of aging indicated that unimplanted cattle had lower (P < 0.05) Warner-Bratzler Shear force values than those from implanted animals. No differences (P > 0.05) in shear force values were found between the two treatments or the control groups for steaks sampled following a 21-d aging period. Steaks from implanted animals sampled after 3, 7, and 14 d aging were rated lower (P < 0.05) for initial and sustained trained sensory panel tenderness scores. Consumers failed to detect any differences in steak samples related to implant treatment after 7 and 14 d of aging. Consumer education level and family income did not affect overall acceptability (P > 0.10 and 0.18, respectively) or tenderness acceptability (P > 0.11 and 0.68, respectively); however, consumers with postgraduate degrees recorded lower (P < 0.05) overall quality, beef flavor, juiciness, and tenderness scores than consumers in all other education classifications. Additionally, family income had no effect on overall quality (P > 0.21), beef flavor (P > 0.28), juiciness (P > 0.58), or tenderness (P > 0.45) scores. Results indicate that using a moderate implant program in Bos indicus-influenced cattle has no detrimental effects on beef tenderness and consumer acceptability.