Search

Copyright of Canadian Journal of Animal Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Minimizing interruptions in feed intake during the highly stressful receiving period is critical for lamb performance and animal welfare for lambs arriving from extensively managed operations. The objectives of the study were to evaluate feeder lamb receiving protocols, specifically the effectiveness of hay processing and respiratory vaccine on feed intake, growth performance, feed efficiency and carcass traits on a 107-d feeding trial. Feeder lambs [n = 63; body weight (BW) = 47.6 ± 7.9 kg; wethers n = 46; ewes n = 17; Western white-faced n = 34; black-faced; n = 4; crossbred; n = 25) sourced from 15 WY and CO producers participated in the “Lamb-A-Year” program at the University of Wyoming- Laramie Research and Extension Center. Lambs were randomly sorted into two groups and fed an 8% CP, 61% NDF hay that was either unprocessed or processed (8 cm). One-half of the lambs in each hay processing group were then vaccinated or not vaccinated with a Mannheimia haemolytica Types 1 & 2 and Pasteurella multocida vaccine. Lambs were adapted to electronic feeders (Vytelle, Calgary, AB, CA) for 7 d (7 to 8 lambs/feeder) to record individual daily feed intake for 50 d. During the initial receiving period (d 0 to 14) lambs had ad libitum access to their respective hay treatment. A textured finishing diet was administered from d 15 to 50 (75% corn, 15% soyhulls, 10% lamb grower pellet). From d 51 to 107, lambs were group fed ad libitum the textured finishing diet until slaughter at a commercial abattoir. Hot carcass weight (HCW), 12th rib back fat (RFT), body wall thickness (BWT), and loin muscle area (LMA) carcass data were collected at the abattoir. Data were analyzed as a mixed model with fixed effects of hay treatment, vaccination status, and their interaction with random effects of ranch source and individual animal. The hay treatment x vaccine status interaction was significant (P ≤ 0.03) for RFI. While the ranking changed for RFI when comparing vaccination status, no statistical difference between treatment groups were observed after a Tukey adjustment. Interestingly, the hay treatment x vaccine status interaction was significant (P ≤ 0.01) for BWT. Again, ranking did change; however, no statistical differences were observed after a Tukey adjustment. Under current study conditions, there were no clear effects on dry matter intake (DMI), average daily gain (ADG), HCW, RFT, or LMA (Table 1). The effects of hay processing type and vaccine administration had minimal disruptions on DMI and ADG. Lamb performance may not be influenced by management interventions at the receiving phase. Further research should evaluate producer management prior to weaning and genetic factors that influence overall performance during the backgrounding and feeding phases. [ABSTRACT FROM AUTHOR]

Simple Summary: The rumen makes up a large portion of the digestive tract of beef cattle and is responsible for the absorption of nutrients and microbial by-products. The rumen papillae interact with feed, microbial populations, and fermentation products important to cattle nutrition. Variation in the animal's ability to take up and utilize these nutrients affects feed efficiency. This study was performed to identify genes involved in feed efficiency that are expressed in two unrelated and physically distant populations of Angus and Hereford crossbred steers. A total of 83 genes were identified that may be useful indicators of feed efficiency in cattle. Differentially expressed genes were involved in a protein turnover pathway and a stomach lining turnover pathway. The use of meta-analysis for the two populations of cattle with different sire lines, management and handling techniques, and feed ingredients should allow the identification of genes that are involved in feed efficiency across cattle populations rather than those identified in a single population. In cattle, the rumen is an important site for the absorption of feed by-products released by bacterial fermentation, and variation in ruminal function plays a role in cattle feed efficiency. Studies evaluating gene expression in the rumen tissue have been performed prior to this. However, validating the expression of genes identified in additional cattle populations has been challenging. The purpose of this study was to perform a meta-analysis of the ruminal transcriptome of two unrelated populations of animals to identify genes that are involved in feed efficiency across populations. RNA-seq data from animals with high and low residual feed intake (RFI) from a United States population of cattle (eight high and eight low RFI) and a Canadian population of cattle (nine high and nine low RFI) were analyzed for differences in gene expression. A total of 83 differentially expressed genes were identified. Some of these genes have been previously identified in other feed efficiency studies. These genes included ATP6AP1, BAG6, RHOG, and YPEL3. Differentially expressed genes involved in the Notch signaling pathway and in protein turnover were also identified. This study, combining two unrelated populations of cattle in a meta-analysis, produced several candidate genes for feed efficiency that may be more robust indicators of feed efficiency than those identified from single populations of animals. [ABSTRACT FROM AUTHOR]

Subclinical mastitis is a common intramammary disease in sheep production systems. Expenses associated with compromised animal performance, therapeutic interventions, and decreased ewe longevity make efforts to minimize its prevalence worthwhile. The objectives of this study were to 1) quantify the prevalence of subclinical mastitis throughout lactation, 2) evaluate the impact of bedding treatments on subclinical mastitis during early lactation, 3) evaluate the efficacy of prophylaxis and feed restriction during weaning on subclinical mastitis cure rates, and 4) identify levels and types of antimicrobial resistance in milk-derived bacteria. Ewe milk samples were collected at days 1, 2, and 28 post-partum, weaning, and 3-d post-weaning for bacterial identification via culture-based methods. Staphylococcus spp. and Streptococcus spp. isolates were subjected to in vitro antimicrobial susceptibility testing. The overall prevalence of subclinical mastitis defined by culture growth ranged between 22% and 66% and differences were observed between post-weaning and days 1 and 28 milk samples. Commonly isolated bacteria include coagulase-negative staphylococci (CoNS; 59%), Bacillus spp. (35%), Mannheimia haemolytica (10%), Staphylococcus aureus (8%), Streptococcus spp. (5%), and Corynebacterium spp. (5%). Early milk samples (days 1 and 2) were compared between jug bedding treatment: jugs were recently vacated, cleaned, and dusted with barn lime before adding fresh straw (CLEAN) or jugs were previously vacated and fresh straw was added atop soiled bedding (SOILED). Jug bedding treatment did not affect the prevalence of subclinical mastitis, though CoNS had greater sulfadimethoxine resistance in SOILED isolates than CLEAN isolates (P = 0.03). Three different weaning treatments were used: ewes were injected with penicillin at weaning (PENN), ewes had restricted feed access 48 h prior to and 72 h post-weaning (FAST), or a combination of these treatments (COMBO). Weaning treatment did not affect the prevalence of subclinical mastitis or cure rate from weaning to 3-d post-weaning, though all PENN and no FAST milk S. aureus isolates were resistant against tetracycline (P = 0.08). Subclinical mastitis prevalence tended to decrease from weaning to post-weaning (P = 0.08). These data show that subclinical mastitis is common throughout lactation and the levels of antimicrobial resistance of bacteria isolated from ewe milk are generally low against commonly used antimicrobials. [ABSTRACT FROM AUTHOR]

The article focuses on study of strategies of post-weaning management and mentions impact on ewe subclinical mastitis and antimicrobial susceptibility. Topics discussed include managing environmental pathogens that may reproduce prevalence of subclinical mastitis, antimicrobial resistance for agents of ovine mastitis and production impacts on ewe productivity and animal welfare.

The article focuses on study of materno-placental microbiome of gravid beef cows under feed intake restriction. Topics discussed include existence of reproductive microbiome as evidence in cattle, matured bovine rumen influenced by feed intake restriction, and counts of phyla presented in abundance in mature rumen being impacted.

Objective: Realimentation can compensate for weight loss from poor-quality feedstuffs or drought. Mature cows fluctuate in body weight throughout the year due to nutrient availability. The objective of this study was to determine whether cows that differ in weight gain during realimentation also differ in the abundance of transcripts for enzymes associated with energy utilization in skeletal muscle. Mature cows were subjected to feed restriction followed by ad libitum feed. Skeletal muscle transcriptome expression differences during the two feeding periods were determined from cows with greater (n = 6) and less (n = 6) weight gain during the ad libitum feeding period. Results: A total of 567 differentially expressed genes (408 up- and 159 down-regulated) were identified for the comparison of restriction and ad libitum periods (PBonferroni < 0.05). These genes were over-represented in lysosome, aminoacyl-tRNA biosynthesis, and glutathione metabolism pathways. Validation of the expression of five of the genes was performed and four were confirmed. These data suggest that realimentation weight gain for all cows is partially controlled by protein turnover, but oxidative stress and cellular signaling pathways are also involved in the muscle tissue. This dataset provides insight into molecular mechanisms utilized by mature cows during realimentation after a period of low abundance feed. [ABSTRACT FROM AUTHOR]

The article tests the hypothesis that the calf rumen is exposed to a microbial source prior to birth and that the amnion plays an important role in its inoculation. It details the isolation and identification of bacterial and archaeal species in the late gestation amniotic fluid (AF). The species are then compared to the rumen fluid of the newborn calf prior to suckling, as well as the meconium of the neonate.

The article tests the hypothesis that the cow maternal rumen microbiome influences colonization of the calf rumen microbiome. It relates the rumen microbiome of the cow prior to parturation and at weaning to the calf's meconium microbiome and calf rumen microbiome at birth and weaning. The sample collection, microbial DNA extraction, library preparation and sequencing, and bioinformatic analysis are discussed.

The article quantifies carcass characteristics of Intermountain West lambs during different time points of the year. It also estimates the economic impact of over-finished lamb carcasses on the processing sector. Topics discussed include subcutaneous fat, hot carcass weight, and yield grade. Also mentioned are percentage of boneless closely trimmed retain cuts, labor and trucking cost, and profitability of lamb carcasses.

The article identifies the impacts of zinc concentrations in a lamb finishing diet on performance and fecal oocyst load. Topics discussed include parasitic infection by Eimeria, average daily gain, and coccidiosis incidence and severity. Also mentioned are animal selection and management, fecal collection and analysis, and feedlot performance.

The article investigates the effects of increased dietary zinc (Zn) fed at approximately three times the National Research Council (NRC) recommendations from late gestation to early lactation on ewe milk Zn and mammary health. Topics discussed include milk somatic cell count, milk mineral element concentrations, and effects on neonate performance, passive immunity, and lamb serum Zn concentrations.

The article presents a study surveying lamb carcass characteristics in the Intermountain West during periods of seasonally constrained supply. Topics discussed include environmental and dietary factors that affect ruminant livestock performance; energy used by ruminants is mainly derived from volatile fatty acids (VFA); and ways in which heat stress (HS) events can affect ruminal microbial populations.

Maternal gestational nutrition is known to impact gut physiology and the gut microbiome of offspring early in life; however, it remains unknown if these changes persist later in life. We hypothesized that the impacts of maternal feed restriction in late gestating beef cows on early colonization of the calf gut would impact the rumen microbiome post-weaning. Our objective was to compare the post-weaning rumen microbiome of calves born with feed restricted dams and those born to dams with adequate nutrition. Starting roughly 60 d before expected calving, dams were stratified to either receive 100% of NRC requirements (CON) or 70% intake of NRC requirements (FR) through 28 d post-parturition. Pairs were then moved on to native grass until weaning. Rumen fluid was collected from the calves at the time of weaning (PRE) and after a 70 d backgrounding feed efficiency study (POST). Microbial DNA was isolated and the V4 region of the 16S rRNA was sequenced on the MiSeq platform. Data were analyzed within each time point using QIIME2. Maternal treatment had no impact on alpha diversity (Faith's phylogeny, Shannon's diversity, and Evenness) in the PRE group, but CON calves had greater (q = 0.05) evenness than FR calves in the POST samples. There were differences in composition between CON and FR in the PRE samples (unweighted unifrac q = 0.04; bray-curtis q = 0.03). No differences (q = 0.14) in composition were found in the POST samples. These data indicate that at the time of weaning (PRE) differences in composition existed in CON vs. FR calves, specifically in the rare taxa, but the microbial composition converged by the end of the feeding trial. Interestingly, previous findings in our lab reported differences in alpha and beta diversity 28 d after birth in these calves. Together, these data indicate the potential for long-term impacts of maternal nutrition on the gut microbiome. This coupled with the previously published work where feed efficiency tended to differ between CON and FR, suggests that early perturbations during gestation may have had lasting impacts on gut physiology and subsequent performance in the presence of rumen microbial shifts. [ABSTRACT FROM AUTHOR]

Late feedlot death caused by congestive heart failure has been quantified extensively through epidemiological studies however, these models do not consider losses or gains associated live growth performance, carcass quality, and consumer rejection of meat products. To address these gaps in the literature, we conducted two studies to characterize effects of pulmonary hypertension on four populations of feedlot cattle. In study one, reproductively intact (INT, n = 19), and ovariectomized (OVX, n = 18) yearling Sim-Angus heifers were selected on heart failure risk according to their pulmonary arterial pressure. Heifers were gradually transitioned onto a feedlot ration and fed to an acceptable harvest body composition determined using both 12th rib subcutaneous fat and body weight. Cattle were weighed biweekly and ADG was calculated by regressing body weight by days on feed (DOF). Pulmonary arterial pressure (PAP) was measured approximately every 3 months by a qualified veterinarian. Cattle were harvested at a commercial harvesting facility where carcass data and muscle samples were collected. In study two, weaned sim-angus steers (n = 41) were selected on heart failure risk categories using the same methodology outline above. Twenty steers were administered a steroidal growth promoting implant upon receiving (IMP) and twenty were untreated (NAT). Steers were fed to an average of 610 kg and data were collected using the same methodology outlined above. Data were analyzed using ANOVA, linear model, and Pearson correlation functions in R statistical software where PAP was used as a fixed continuous variable. Data were analyzed by study with the exception of live growth performance regression and correlations where data were combined. Linear regression within the combined datasets showed that initial mean PAP (P < 0.001), diastolic pressure (P < 0.001), and sex (P < 0.001) positively influenced ADG throughout the duration of the finishing period. Furthermore, initial PAP was moderately correlated with ADG (R = 0.38, P < 0.001). Gain to feed (G:F) was positively correlated with initial diastolic PAP (R = 0.31, P < 0.006). Neither initial mean PAP nor diastolic pressures impacted dry matter intake (DMI; P > 0.90), but sex was associated with DMI where steers had significantly decreased DMI (P = 0.003). Within study two, longissimus muscle objective color values were influenced by PAP where a* (redness; P < 0.001) and b* (yellowness; P < 0.04) values were negatively correlated with final PAP. These data begin to demonstrate the close relationship between live growth performance and pulmonary hypertension. More research is needed to better understand how cellular energy metabolism is potentially contributing to increased growth performance but negatively influencing muscle health in the form of oxygen binding capacity and inflammation. [ABSTRACT FROM AUTHOR]

The rumen microbiome has a critical role in multiple facets of ruminant livestock production. It is well known that the rumen microbiome is integral to animal performance through impacts on feed efficiency, greenhouse gas production, volatile fatty acid production, and numerous aspects of animal health. Therefore, understanding factors that influence the rumen microbiome at various stages of the production cycle and the interactions with other microbial niches and physiological processes is a critical area of research to aid in the goal of improving livestock performance. Our research objectives have focused on 3 primary general areas including 1) to characterize and understand the potential pathways of early gut colonization from conception throughout gestation, 2) implications of varying gestational perturbations on rumen microbiome development and calf performance post-weaning, and 3) understand the connections between the rumen microbiome and the microbiomes of the reproductive tract, blood, and respiratory tract. We hypothesize that strategies to program the rumen microbiome early in life may have lasting impacts on host performance specific to feed efficiency, reproductive fitness, and have implications on high altitude disease. These effects may not be a direct relationship between the rumen microbiome and host response, but rather through a total system level response that has the rumen microbiome as a key player in that cascade. The rumen microbiome has the potential to impact numerous aspects of host performance, as such, it is imperative that research continues to elucidate its role in host physiology and the development of intervention mechanisms to initiate specific responses in the rumen microbiome to improve downstream host response. [ABSTRACT FROM AUTHOR]

Subclinical mastitis, a common intramammary disease in sheep production, can be costly to producers due to compromised performance and decreased longevity. Our research focused on preventative and therapeutic measures on mammary health where the objectives were to identify (1) the impact of Zn supplementation on the milk microbiome and (2) the impact of management practices at lambing and weaning on prevalence and cure rate of subclinical mastitis, the milk microbiome, and levels of antimicrobial resistance in milk bacteria. In study 1, the milk microbiome was characterized during the first 3 wk of lactation and at weaning in ewes divergent in dietary Zn supplementation (1× = CON or 3× recommendations = ZnTRT). Mammary health was assessed using somatic cell count (SCC) class. Amplicon sequencing revealed the presence of Staphylococcus, Mannheimia, Corynebacterium, and Pseudomonas, all major mastitis pathogens. Effects of breed, dietary Zn concentration, and SCC class on diversity were limited to early lactation, where CON milk had greater composition stability than ZnTRT milk (P = 0.02). In study 2, milk bacteria were characterized by culture; Staphylococcus spp. and Streptococcus spp. were tested for antimicrobial susceptibility. Subclinical mastitis prevalence ranged from 22–66% where coagulase-negative staphylococci (CoNS; 59%), bacilli (35%), Mannheimia haemolytica (10%), S. aureus (8%), streptococci (5%), and Corynebacterium spp. (5%) were common. Milk samples were compared by jug bedding treatment: jugs were cleaned and dried with barn lime before adding fresh straw (CLEAN) or fresh straw was added atop soiled bedding (SOILED). Bedding had no effect on subclinical mastitis (P = 0.57), but CoNS had greater sulfadimethoxine resistance in SOILED isolates (P = 0.03). Additional mastitis control methods at weaning were evaluated: penicillin injection (PENN), restricted feed access (FAST), or their combination (COMBO). Weaning treatment did not affect cure rate from weaning to 3-d post- weaning (P = 0.21). Further characterization of these samples via microbial sequencing are underway with source tracking analyses to investigate an exogenous route via retrograde transfer and environmental bacteria or endogenous route via an entero-mammary pathway. Results support that breed, animal husbandry, and mammary health variably affect the milk microbiome and provide novel insight to the impact of management practices in a milk microbiome longitudinal study. [ABSTRACT FROM AUTHOR]

Tremendous economic loss is attributed to high altitude disease mortality of calves in the Mountain West and Great Plains region. Additional economic losses may be associated with changes in feed efficiency and carcass quality in animals at higher risk of heart failure during the finishing phase. Thus, the objective of the current study is to evaluate economically relevant traits throughout the finishing period to determine inefficiencies associated with variable levels of heart failure risk and reproductive tract type of beef heifers. Both intact reproductive tract (n = 19) and ovariectomized (n = 18) heifers were stratified by risk category, where initial pulmonary arterial pressure (PAP) levels at or below 42 mmHg were designated as low risk and those above 42 mmHg as moderate/high risk. Heifers were fed a grain-based diet for 125 d before transportation to the harvest facility on d 126. All heifers were weighed in 2 wk intervals. Heifers were PAP tested by a qualified veterinarian in approximately 3 mo intervals during the feeding period. Feed intake data was collected for the last 55 d prior to harvest using the Vytelle SENSETM bunk system. Time of harvest was determined based on live weight and final ultrasound 12th rib fat thickness. Data were analyzed using the ANOVA function of R with tract type and risk as fixed effects. Comparisons were tested using a significance level of α = 0.05 and 0.05 (P ≤ 0.10) were considered tendencies. There were no interactions of risk category and tract type on performance or carcass characteristics (P ≥ 0.14). There was a tendency for higher total intake (P = 0.07) and relative growth rate (P = 0.04) among moderate/high risk heifers compared to the low-risk category. Hot carcass weight, marbling score, ribeye area, and USDA yield grade were not impacted (P ≥ 0.16) by risk category. Intact heifers had greater (P = 0.02) total gain than their ovariectomized contemporaries. However, marbling scores were higher (P = 0.04) among ovariectomized heifers compared to those from intact heifers. These data suggest that risk category and tract type minimally influence performance and carcass characteristics in a population that selects sires with low PAP scores. It remains unclear if more initial divergence in PAP scores would elicit greater impacts on performance and carcass characteristics in feedlot heifers. [ABSTRACT FROM AUTHOR]