The objective of this study is to investigate individual animal variation of bovine fecal microbiota including as affected by diets. Fecal samples were collected from 426 cattle fed 1 of 3 diets ...typically fed to feedlot cattle: 1) 143 steers fed finishing diet (83% dryrolled corn, 13% corn silage, and 4% supplement), 2) 147 steers fed late growing diet (66% dry-rolled corn, 26% corn silage, and 8% supplement), and 3) 136 heifers fed early growing diet (70% corn silage and 30% alfalfa haylage). Bacterial 16S rRNA gene amplicons were determined from individual fecal samples using next-generation pyrosequencing technology. A total of 2,149,008 16S rRNA gene sequences from 333 cattle with at least 2,000 sequences were analyzed. Firmicutes and Bacteroidetes were dominant phyla in all fecal samples. At the genus level, Oscillibacter, Turicibacter, Roseburia, Fecalibacterium, Coprococcus, Clostridium, Prevotella, and Succinivibrio were represented by more than 1% of total sequences. However, numerous sequences could not be assigned to a known genus. Dominant unclassified groups were unclassified Ruminococcaceae and unclassified Lachnospiraceae that could be classified to a family but not to a genus. These dominant genera and unclassified groups differed (P < 0.001) with diets. A total of 176,692 operational taxonomic units (OTU) were identified in combination across all the 333 cattle. Only 2,359 OTU were shared across 3 diet groups. UniFrac analysis showed that bacterial communities in cattle feces were greatly affected by dietary differences. This study indicates that the community structure of fecal microbiota in cattle is greatly affected by diet, particularly between forage- and concentrate-based diets.
The inter-cattle growth variations stem from the interaction of many metabolic processes making animal selection difficult. We hypothesized that growth could be predicted using metabolomics. Urinary ...biomarkers of cattle feed efficiency were explored using mass spectrometry-based untargeted and targeted metabolomics. Feed intake and weight-gain was measured in steers (n = 75) on forage-based growing rations (stage-1, 84 days) followed by high-concentrate finishing rations (stage-2, 84 days). Urine from days 0, 21, 42, 63, and 83 in each stage were analyzed from steers with the greater (n = 14) and least (n = 14) average-daily-gain (ADG) and comparable dry-matter-intake (DMI; within 0.32 SD of the mean). Steers were slaughtered after stage-2. Adjusted fat-thickness and carcass-yield-grade increased in greater-ADG-cattle selected in stage-1, but carcass traits did not differ between ADG-selected in stage-2. Overall 85 untargeted metabolites segregated greater- and least-ADG animals, with overlap across diets (both stages) and breed type, despite sampling time effects. Total 18-bile acids (BAs) and 5-steroids were quantified and associated with performance and carcass quality across ADG-classification depending on the stage. Stepwise logistic regression of urinary BA and steroids had > 90% accuracy identifying efficient-ADG-steers. Urine metabolomics provides new insight into the physiological mechanisms and potential biomarkers for feed efficiency.
Depletion of the ovarian reserve is associated with reproductive senescence in mammalian females, and there is a positive relationship between the size of the ovarian reserve and the number of antral ...follicles on the surface of the ovary. Therefore, we conducted a series of experiments to investigate the influence of stage of the estrous cycle, age, and birth weight on antral follicle counts (AFC) in beef cows and heifers. Pairs of ovaries were collected from crossbred beef cows at slaughter (n = 72) or at necropsy (n = 333; 0 to 11 yr of age); all visible antral follicles were counted, the ovaries were weighed, and stage of the estrous cycle was estimated based on ovarian morphology. There was no influence of estimated stage of the estrous cycle on AFC (P = 0.36). There was a small but positive effect of birth weight on AFC AFC = -1.7 + 0.31(birth weight); P = 0.007, r² = 0.05. When antral follicle counts were regressed on age, there was a quadratic effect of age such that AFC increased until 5 yr of age and decreased thereafter AFC = 12.9 + 9.0(yr) - 0.86(yr²); P < 0.001, r² = 0.22. In a third experiment, crossbred beef heifers (n = 406; 353 to 463 d of age) at 3 locations were subjected to ovarian ultrasonography on unknown day of the estrous cycle. Heifers were classified as low AFC (<15 follicle, n = 84) or high AFC (>24 follicles, n = 178). Whereas estimated stage of the estrous cycle did not influence AFC (P = 0.62), heifers classified as low AFC had smaller ovaries (P = 0.001), decreased birth weight (P = 0.003), and a decreased heifer pregnancy rate (P = 0.05) compared with heifers in the high AFC group. From these results, we conclude that AFC in beef cows and heifers is influenced by birth weight and age but not by stage of the estrous cycle. In beef cows, the number of antral follicles increases to 5 yr of age and then begins to decline. This may indicate that a decrease in fertility due to decline of the ovarian reserve may begin earlier than previously thought in beef cows.
The objective was to examine the effect of maternal nutrient restriction followed by realimentation during midgestation on uterine blood flow (BF). On Day 30 of pregnancy, lactating, multiparous ...Simmental beef cows were assigned randomly to treatments: control (CON; 100% National Research Council; n = 6) and nutrient restriction (RES; 60% of CON; n = 4) from Day 30 to 140 (period 1), and thereafter, realimented to CON until Day 198 of gestation (period 2). Uterine BF, pulsatility index (PI), and resistance index (RI) were obtained from both the ipsilateral and contralateral uterine arteries via Doppler ultrasonography. Generalized least square analysis was performed. Ipsilateral uterine BF in both groups increased quadratically (P < 0.01) during period 1 and linearly (P < 0.01) during period 2. There was a treatment (P = 0.05) effect during period 2; where RES cows had greater ipsilateral BF versus CON. Ipsilateral uterine PI and RI decreased linearly (P ≤ 0.01) during period 1 across treatments. Contralateral uterine BF in CON cows tended (P < 0.09) to be greater versus RES in both periods. Contralateral PI in both groups increased linearly (P ≤ 0.01) during period 1. Contralateral uterine RI was increased (P ≤ 0.05) in RES cows versus CON in both periods. There was no interaction or treatment effect (P ≥ 0.24) for total BF during either period. Nutrient restriction does not alter total uterine BF, but it may increase vascular resistance. However, up on realimentation, local conceptus-derived vasoactive factors appear to influence ipsilateral uterine BF.
We hypothesized that CH4 production will decrease with increased feed efficiency. Two experiments were conducted to determine CH4 production of cattle that differed in feed efficiency. Cattle in both ...studies were selected from larger contemporary groups. Animals furthest from the confidence ellipse that resulted from regressing BW gain on DMI were selected. In the first experiment, 113 crossbred steers were evaluated for feed efficiency for 64 d. Steers were 355 ± 1 d of age and weighed 456 ± 10 kg when they began the study. Steers were fed a ration that consisted of (dry matter basis) 82.8% corn, 12.8% corn silage, and 4.5% supplement (contains 0.065% monensin, 32% CP (28% NPN), 7.5% Ca, 0.8% P, 4.8% NaCl 1.8% K, and 55,116 IU/kg Vitamin A). Thirty-seven steers were selected to measure CH4 production. In the second experiment, 197 heifers were evaluated for feed efficiency for 64 d. Heifers were 286 ± 1 d of age and weighed 327 ± 2 kg when they began the study. Heifers were fed a ration that consisted of (dry matter basis) 60% corn silage, 30% alfalfa hay, and 10% wet distillers grains with solubles. Forty-seven heifers were selected to measure CH4 production. Methane production was measured with respiration calorimeters. In both experiments, cattle had ad libitum access to feed, and DMI consumed during the 24 h before CH4 production was measured. Methane production was collected for a 6-h period on untrained cattle; consequently, methane production is not a quantitative measure of daily methane production rather it is an index value to rank cattle. Multiple regression analysis was used to determine the relationship between either BW gain:DMI ratio or residual feed intake (RFI) on CH4 production after adjusting for the previous 24 h DMI. In the steers, gain:DMI ratio and previous 24 h feed intake accounted for little of the variance in CH4 production (R2 = 0.009), nor did RFI and previous 24 h feed intake (R2 = 0.001). In the heifers, the gain:DMI ratio contributed 28% toward the variance estimate and previous 24-h DMI contributed 72% toward the variance estimate (R2 = 0.31). As the gain:DMI ratio increased daily CH4 production increased. The regression coefficient for RFI (P = 0.45) did not differ from zero for CH4 production. Our study does not support our original hypothesis that CH4 production decreases with increased feed efficiency, and suggests that CH4 production may increase with increased feed efficiency.
Apart from the rumen, limited knowledge exists regarding the structure and function of bacterial communities within the gastrointestinal tract and their association with beef cattle feed efficiency. ...The objective of this study was to characterize the microbial communities of the cecum among steers differing in feed efficiency. Within 2 contemporary groups of steers, individual feed intake and BW gain were determined from animals fed the same diet. Within both of 2 contemporary groups, BW was regressed on feed intake and 4 steers within each Cartesian quadrant were sampled (n = 16/group). Bacterial 16S rRNA gene amplicons were sequenced from the cecal content using next-generation sequencing technology. No significant changes in diversity or richness were detected among quadrants, and UniFrac principal coordinate analysis did not show any differences among quadrants for microbial communities within the cecum. The relative abundances of microbial populations and operational taxonomic units revealed significant differences among feed efficiency groups (P < 0.05). Firmicutes was the dominant cecal phylum in all groups and accounted for up to 81% of the populations among samples. Populations were also dominated by families Ruminococcaceae, Lachnospiraceae, and Clostridiaceae, with significant shifts in the relative abundance of taxa among feed efficiency groups, including families Ruminococcaceae (P = 0.040), Lachnospiraceae (P = 0.020), Erysipelotrichaceae (P = 0.046), and Clostridiaceae (P = 0.043) and genera Coprobacillus (P = 0.049), Parabacteroides (P = 0.044), Blautia (P = 0.042), Ruminococcus (P = 0.040), Oscillospira (P = 0.042), and Prevotella (P = 0.042). The study identified cecal microbial associations with feed efficiency, ADG, and ADFI. This study suggests an association of the cecum microbial community with bovine feed efficiency at the 16S level.
Aims
The objective of this study was to determine if the faecal microbiome has an association with Escherichia coli O157:H7 prevalence and enumeration.
Methods and Results
Pyrosequencing analysis of ...faecal microbiome was performed from feedlot cattle fed one of three diets: (i) 94 heifers fed low concentrate (LC) diet, (ii) 142 steers fed moderate concentrate (MC) diet, and (iii) 132 steers fed high concentrate (HC) diet. A total of 322 585 OTUs were calculated from 2,411,122 high‐quality sequences obtained from 368 faecal samples. In the LC diet group, OTUs assigned to the orders Clostridiales and RF39 (placed within the class Mollicutes) were positively correlated with both E. coli O157:H7 prevalence and enumeration. In the MC diet group, OTUs assigned to Prevotella copri were positively correlated with both E. coli O157:H7 prevalence and enumeration, whereas OTUs assigned to Prevotella stercorea were negatively correlated with both E. coli O157:H7 prevalence and enumeration. In both the MC diet group and the HC diet group, OTUs assigned to taxa placed within Clostridiales were both positively and negatively correlated with both E. coli O157:H7 prevalence and enumeration. However, all correlations were weak. In both the MC diet group and the HC diet group, stepwise linear regression through backward elimination analyses indicated that these OTUs were significantly correlated (P < 0·001) with prevalence or enumeration, explaining as much as 50% of variability in E. coli O157:H7 prevalence or enumeration.
Conclusions
Individual colonic bacterial species have little impact on E. coli O157:H7 shedding but collectively groups of bacteria were strongly associated with pathogen shedding.
Significance and Impact of the Study
Bacterial groups in the bovine colon may impact faecal shedding of the zoonotic pathogen E. coli O157:H7, and manipulation of the intestinal microbiota to alter these bacteria may reduce shedding of this pathogen and foodborne illnesses.
The impetus behind the global food security challenge is direct, with the necessity to feed almost 10 billion people by 2050. Developing a food-secure world, where people have access to a safe and ...sustainable food supply, is the principal goal of this challenge. To achieve this end, beef production enterprises must develop methods to produce more pounds of animal protein with less. Selection for feed-efficient beef cattle using genetic improvement technologies has helped to understand and improve the stayability and longevity of such traits within the herd. Yet genetic contributions to feed efficiency have been difficult to identify, and differing genetics, feed regimens, and environments among studies contribute to great variation and interpretation of results. With increasing evidence that hosts and their microbiomes interact in complex associations and networks, examining the gut microbial population variation in feed efficiency may lead to partially clarifying the considerable variation in the efficiency of feed utilization. The use of metagenomics and high-throughput sequencing has greatly impacted the study of the ruminant gut. The ability to interrogate these systems at great depth has permitted a greater understanding of the microbiological and molecular mechanisms involved in ruminant nutrition and health. Although the microbial communities of the reticulorumen have been well documented to date, our understanding of the populations within the gastrointestinal tract as a whole is limited. The composition and phylogenetic diversity of the gut microbial community are critical to the overall well-being of the host and must be determined to fully understand the relationship between the microbiomes within segments of the cattle gastrointestinal tract and feed efficiency, ADG, and ADFI. This review addresses recent research regarding the bacterial communities along the gastrointestinal tract of beef cattle; their association with ADG, ADFI, and feed efficiency; and the potential implications for beef production.
Fluctuating feed resources to beef cows across the production cycle is a proven method for decreasing input costs; however, limiting nutrients during late gestation have been demonstrated to decrease ...ovarian follicle numbers in female offspring in some studies. We hypothesize that limiting nutrients to mature (≥3yr) crossbred beef cows during the second and third trimesters would result in daughters that would have decreased follicle numbers detectable by ultrasonography as yearlings. Over four breeding seasons, pregnant beef cows (n=397) were assigned to either Low (L), Moderate (M) or High (H) nutrient intake during the second or third trimester, resulting in four dietary treatment groups (L–H, L–L, M–H, and M–M). Heifers (n=416) born to these cows were weighed at weaning and moved to a dry lot where they were monitored for behavioral estrus with the aid of heat detection patches. Two weeks before their first breeding season, heifers were submitted for ultrasonographic examination of their ovaries to determine antral follicle numbers. Heifers were placed with bulls for 60d and pregnancy status was determined 45d after the bulls were removed. Growth and reproductive traits were analyzed using the MIXED Procedure of SAS with maternal diet and year as fixed effects. Maternal dietary intake did not affect heifer growth rates, age at puberty, or antral follicle counts (P≥0.40). However, an increased proportion of the heifers born to dams fed a high nutrient diet during the third trimester (L–H or M–H) calved in the first 21d of their first calving season (P=0.004). Antral follicle counts detectable by ultrasonography at yearling pre-breeding examination were greater in heifers that calved during the first 21d of their first calving season (P=0.02); however, these heifers did not differ in age at puberty (P=0.60). From this study, we conclude that: (1) limiting nutrient intake during late gestation in mature (≥3yr) beef cows does not influence the ovarian reserve or reproductive performance of daughters; (2) increasing maternal nutrient intake during the third trimester can improve the first service conception rates of daughters; and (3) pre-breeding ultrasonography to determine antral follicle counts is a good indicator of fertility for choosing replacement heifers.
Twenty-four lactating and 13 nonlactating Alpine goats were used to determine effects of stage of lactation and dietary concentrate level on energy utilization. Diets comprising 60 or 20% concentrate ...(60%C and 20%C, respectively) were consumed ad libitum by lactating animals and at a level of intake near maintenance by nonlactating animals. Measurement periods were d 25 to 31 (early), 87 to 94 (mid), and 176 to 183 (late) of lactation. Eleven observations were made in early and mid lactation for each diet, and 8 and 7 were made in late lactation for the 60%C and 20%C diets, respectively. Efficiency of metabolizable energy (ME) use for maintenance (66.9, 71.4, and 61.1% for early, mid, and late lactation, respectively) and the maintenance ME requirement (479, 449, and 521 kJ/kg of BW0.75 for early, mid, and late lactation, respectively) determined with nonlactating animals differed among stages of lactation. The efficiency of ME use for maintenance was similar between diets, but the maintenance requirement tended to be greater for the 60%C than for the 20%C diet (504 vs. 463 kJ/kg of BW0.75). The latter difference may have involved greater ME intake for the 60%C diet, resulting in a slightly greater difference between ME intake and total heat energy for the 60%C compared with the 20%C diet (11 vs. −8 kJ/kg of BW0.75). Intake of ME by lactating goats was greater for the 60%C than for the 20%C diet (18.6 vs. 16.3 MJ/d). Recovered energy in lactation from mobilized tissue tended to be greater for the 60%C than for the 20%C diet (8.44 vs. 6.55 MJ/d) and differed among stages of lactation (2.60, 1.59, and 1.13 MJ/d in early, mid, and late lactation, respectively). Recovered energy in tissue gain was similar among stages of lactation and between diets and was not different from 0. Efficiency of use of dietary ME for lactation differed among stages of lactation (59.5, 51.9, and 65.4% for early, mid, and late lactation, respectively) and tended to be greater for the 60%C than for the 20%C diet (64.2 vs. 54.9%). The efficiency of use of dietary ME for maintenance and lactation was similar among stages of lactation and was greater for the 60%C compared with the 20%C diet (64.3 vs. 60.9%). Predicted milk yield from National Research Council requirements was reasonably accurate. In conclusion, using data of nonlactating goats to study energy utilization for maintenance in lactation has limitations. Efficiency of energy use by lactating dairy goats consuming diets high in concentrate appears greater than that by goats consuming diets low in concentrate. Despite differences in nutrient requirement expressions, observations of this study support National Research Council recommendations of energy requirements of lactating dairy goats.
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