Impact of methane mitigation strategies on the native ruminant microbiome: A protocol for a systematic review and meta-analysis.

Recently, research has investigated the role of the ruminant native microbiome, and the role microbes play in methane (CH4) production and mitigation. However, the variation across microbiome studies makes implementing impactful strategies difficult. The first objective of this study is to identify, summarize, compile, and discuss the current literature on CH4 mitigation strategies and how they interact with the native ruminant microbiome. The second objective is to perform a meta-analysis on the identified16S rRNA sequencing data. A literature search using Web of Science, Scopus, AGRIS, and Google Scholar will be implemented. Eligible criteria will be defined using PICO (population, intervention, comparator, and outcomes) elements. Two independent reviewers will be utilized for both the literature search and data compilation. Risk of bias will be assessed using the Cochrane Risk Bias 2.0 tool. Publicly available 16S rRNA amplicon gene sequencing data will be downloaded from NCBI Sequence Read Archive, European Nucleotide Archive or similar database using appropriate extraction methods. Data processing will be performed using QIIME2 following a standardized protocol. Meta-analyses will be performed on both alpha and beta diversity as well as taxonomic analyses. Alpha diversity metrics will be tested using a Kruskal-Wallis test with a Benjamini-Hochberg multiple testing correction. Beta diversity will be statistically tested using PERMANOVA testing with multiple test corrections. Hedge's g standardized mean difference statistic will be used to calculate fixed and random effects model estimates using a 95% confidence interval. Heterogeneity between studies will be assessed using the I2 statistic. Potential publication bias will be further assessed using Begg's correlation test and Egger's regression test. The GRADE approach will be used to assess the certainty of evidence. The following protocol will be used to guide future research and meta-analyses for investigating CH4 mitigation strategies and ruminant microbial ecology. The future work could be used to enhance livestock management techniques for GHG control. This protocol is registered in Open Science Framework (https://osf.io/vt56c) and available in the Systematic Reviews for Animals and Food (https://www.syreaf.org/contact).

A diverse diet increases animal growth performance and carcass yield of grazing lambs.

The current experiments were conducted across two lamb finishing seasons (2019 [experiment 1; Exp1] and 2020 [experiment 2; Exp2]). In both experiments lambs were provided a monotonous (MON) diet (annual ryegrass [Lolium multiflorum L.] during 2019 and perennial ryegrass [L. perenne L.] and white clover [Trifolium repens L.] during 2020) or a diverse (DIV) diet composed of spatially separated strips sown to chicory (Chicorium intybus L.), plantain (Plantago lanceolata L.), perennial ryegrass, lucerne (Medicago sativa L.), and dock (Rumex obtusifolius). During Exp1, the DIV lambs had a stocking rate (SR) of either 80, 95, 100, or 110 m2/lamb/wk, whereas the MON lambs had a 100 m2/lamb/wk SR. In Exp2, the SR aimed to allocate the MON lambs with twice the forage allowance (kg DM/lamb/d) as DIV lambs. In Exp1, all lambs provided DIV had a greater (P < 0.01) average daily gain (ADG; + 130%) than MON rams, independent of the SR. Accordingly, DIV had greater (P < 0.05) hot carcass weight (HCW; + 26%) and aged carcass weight (CW; + 27%) compared with MON, across all SR. The 80 m2/lamb/wk SR tended to have a greater (P = 0.10) dressing percentage and had similar (P = 0.29) drip loss percentage to the MON lambs, while the other DIV lamb SR all had greater (P < 0.05; +12%) dressing percentages and lower (P < 0.05) drip loss percentage than MON lambs. In Exp2, DIV lambs had greater (P < 0.01) ADG (+37%), HCW (+15%), and dressing percentage (+6%) compared with MON lambs. This improved animal performance occurred despite being offered 57% less (P = 0.01) dry matter (DM), 56% less (P < 0.01) digestible DM, and 57% less (P = 0.02) metabolizable energy per lamb per day. Ultimately, these experiments demonstrate that providing growing lambs a functionally diverse diet improves animal growth performance and carcass weight compared with a monotonous diet of annual ryegrass or a mixed sward containing perennial ryegrass with white clover.

Utilizing gas flux from automated head chamber systems to estimate dietary energy values for beef cattle fed a finishing diet.

Dietary net energy for maintenance (NEm) and gain (NEg) can be estimated using calculations based on live performance or adjusted-final body weight, which is calculated based on carcass characteristics. These values are commonly referred to as performance-adjusted (pa) NEm (paNEm) and NEg (paNEg). The NEm and NEg of a diet can also be estimated by adding recovered energy (RE) with heat production (HP) derived from an automated head chamber system (AHCS), which we will term gas-adjusted (ga) NEm (gaNEm) and NEg (gaNEg). Furthermore, HP from the Brouwer equation requires an estimate of urinary nitrogen (UN) excretion, which can be calculated based on N intake, blood urea N, UN concentration, and urine creatinine, or it could be zeroed. Alternatively, HP can be calculated using an alternative equation based on the respiratory quotient. Demonstrating agreement between pa and ga derived dietary energy values provides an opportunity to validate using the AHCS for energetic experiments and this comparison has not been conducted previously. Accordingly, the objective of this experiment was to assess the agreement between live and carcass paNEm and paNEg with gaNEm and gaNEg, where HP was calculated using 4 different approaches. Estimates of HP were not different (P = 0.99) between the 4 approaches employed, indicating that all options investigated are appropriate. Live paNEm and paNEg had a higher agreement (Lin's concordance correlation coefficient [CCC] = 0.91) with gaNEm and gaNEg than carcass values (CCC ≤ 0.84). These results suggest that researchers can implement the AHCS to provide good estimates of dietary energy values in finishing beef cattle that are unrestrained.

Automated head chamber systems (AHCS) implemented into beef cattle research allow estimation of gas flux, heat production (HP), and calculated gas-adjusted dietary net energy for maintenance (gaNEm) and gain (gaNEg) values when paired with recovered energy. However, a comparison between AHCS-derived values and performance-adjusted NEm (paNEm) and NEg (paNEg) from either live performance (live paNEm and paNEg) or carcass data (carcass paNEm and paNEg) has not been conducted. Accordingly, the objectives of this experiment were to evaluate the agreement between gaNEm and gaNEg, estimated using different approaches for calculating HP, with live paNEm and paNEg or carcass paNEm and paNEg. Accounting for urinary nitrogen or methane when calculating HP does not appreciably influence HP estimates or subsequent calculations to estimate dietary NEm and NEg. There was excellent agreement between live paNEm and gaNEm, and between paNEg and gaNEg. Measures of precision, accuracy, and agreement were lower for carcass than for live-derived values when compared to gaNEm and gaNEg but were still acceptable. These results suggest that researchers can implement the AHCS to provide estimates of HP, gas flux, and estimates of dietary energy values in unrestrained finishing beef cattle-fed diets ranging in crude protein content (10.8% to 12.5%). Additional research is warranted on the use of the AHCS to conduct energetic studies across varying diets and production systems, particularly grazing systems.

Recommendations on visit duration and sample number requirements for an automated head chamber system.

Automated head chamber systems (AHCS; GreenFeed, C-Lock Inc., Rapid City, SD) increasingly are being used for measuring the gas flux of unrestrained cattle. There are a wide range of recommendations for what constitutes a "good" visit (i.e., duration) to an AHCS and how many visits are required for the AHCS to quantify gas fluxes accurately and precisely. Accordingly, the purpose of this experiment was to investigate the effects of visit duration thresholds and the subsequent effects of these thresholds on the number of visits needed to provide adequate estimates of carbon dioxide (CO2) and methane (CH4) emissions, and oxygen (O2) consumption by beef cattle. This analysis utilized data from three previously published experiments with grazing beef steers and one experiment with finishing beef steers, with 103 steers total. When comparing all available visits, there was excellent agreement [Lin's concordance correlation coefficient (CCC) ≥ 0.96] between visits ≥ 3 min in duration and those ≥ 2 min for the three gases in all four experiments. When data from all four experiments were pooled, there was excellent agreement between visits ≥ 3 min and those ≥ 2 min and ≥ 1 min for all gases (CCC ≥ 0.96). These results suggest that estimates from visits ≥ 2 min are like those from visits ≥ 3 min. Next, we investigated if including visits ≥ 2 min or ≥ 1 min would increase the minimal number of visits required to provide excellent agreement with the "gold-standard" (mean of all visits ≥ 3 min). For this, we used only one of the experiments and randomly selected visits per animal ranging from n = 5 to 60, in increments of 5. The sole experiment was used because all animals had more than 60 visits. We then assessed the agreement between the "gold-standard" (mean of all visits ≥ 3 min [144 ±â€…55.01 visits per steer]) estimates of CO2, O2, and CH4. The minimum number of visits required to achieve excellent agreement (CCC ≥ 0.90) to the "gold-standard" estimate for all gases was 30 visits ≥ 3 min in duration, or 40 visits ≥ 2 min in duration. Visits ≥ 1 min in duration did not achieve excellent agreement, even when 60 were used. Based on these results, we recommend excluding visits < 3 min in duration with 30 minimum visit records per animal. However, if researchers choose to implement a 2-min visit duration threshold then 40 visit records are needed per animal.

GreenFeed systems (C-Lock Inc., Rapid City, SD) are being increasingly used for measuring carbon dioxide (CO2) and methane (CH4) emissions and oxygen consumption (O2) of free-roaming cattle. These systems utilize averages of multiple visits to provide estimates of daily gas flux. There currently exists a range of recommendations for what constitutes a "good" visit to GreenFeed. Additionally, the number of recommended visits required to achieve adequate estimates of these gas fluxes appears to be dependent on the minimum visit duration that is used. To date, there has been only one experiment that has investigated visit duration and the recommended number of visits for CO2 and CH4 emissions and to our knowledge this has not been assessed for O2 consumption. Based on the results of this experiment, we recommend using a 3-min minimum visit duration threshold with 30 visit records per animal. If researchers choose to use a 2-min visit duration threshold, then 40 visit records per animal are recommended.

Association of glucose metabolism and insulin resistance with feed efficiency and production traits of finishing beef steers.

Increasing nutrient utilization efficiency is an important component of enhancing the sustainability of beef cattle production. The objective of this experiment was to determine the association of glucose metabolism and insulin resistance with dry matter intake (DMI), average daily gain (ADG), gain:feed ratio (G:F), and residual feed intake (RFI). Steers (n = 54; initial body weight = 518 ±â€…27.0 kg) were subjected to an intravenous glucose tolerance test (IVGTT) where glucose was dosed through a jugular catheter and serial blood samples were collected. Three days after the last group's IVGTT, steers began a 63-d DMI and ADG test. Body weight was measured on days 0, 1, 21, 42, 62, and 63, and DMI was measured using an Insentec Roughage Intake Control system (Hokofarm Group, Emmeloord, the Netherlands). To examine relationships between DMI, ADG, G:F, and RFI with IVGTT measurements, Pearson correlations were calculated using Proc Corr of SAS 9.4 (SAS Inst. Inc., Cary, NC). Additionally, cattle were classified based on DMI, ADG, RFI, and G:F, where the medium classification was set as mean ±â€…0.5 SD, the low classification was < 0.5 SD from the mean, and the high classification was > 0.5 SD from the mean. No associations between DMI and IVGTT parameters were observed, and no differences were detected when classifying cattle as having low, medium, or high DMI. Peak insulin concentration in response to the IVGTT tended to be correlated with ADG (r = 0.28; P = 0.07), indicating cattle with greater ADG tend to have a greater insulin release in response to glucose. Glucose nadir concentrations tended to be positively correlated with ADG (r = 0.26; P = 0.10). Additionally, the glucose nadir was greater in high-ADG steers (P = 0.003). The association of greater glucose nadir with high-ADG could indicate that high-ADG steers do not clear glucose as efficiently as low-ADG steers, potentially indicating increased insulin resistance. Further, RFI was not correlated with IVGTT measurements, but low RFI steers had a greater peak glucose concentration (P = 0.040) and tended to have a greater glucose area under the curve (P = 0.09). G:F was correlated with glucose area under the curve (r = 0.33; P = 0.050), glucose nadir (r = 0.35; P = 0.011), and insulin time to peak (r = 0.39; P = 0.010). These results indicate that glucose metabolism and insulin signaling are associated with growth and efficiency, but the molecular mechanisms that drive these effects need to be elucidated.

Feed efficiency is an important component of improving the sustainability of beef production. There is a need to understand how metabolism influences feed efficiency. This experiment aimed to explore the association of glucose metabolism and insulin resistance with feed intake, growth, and efficiency of finishing beef cattle. The results indicate that there is a relationship between insulin resistance and improved efficiency measured as the ratio of growth to feed intake. The findings of this experiment are novel as they show a relationship between insulin resistance and feed efficiency and indicate further research is needed to determine the mechanisms of insulin resistance in ruminants that contribute to improved feed efficiency.

An Experimental Field Trial Investigating the Use of Bacteriophage and Manure Slurry Applications in Beef Cattle Feedlot Pens for Salmonella Mitigation.

Post-harvest Salmonella mitigation techniques are insufficient at addressing Salmonella harbored in cattle lymph nodes, necessitating the exploration of pre-harvest alternatives that reduce Salmonella prior to dissemination to the lymph nodes. A 2 × 2, unbalanced experiment was conducted to determine the effectiveness of pre-harvest treatments applied to the pen surface for Salmonella mitigation in cattle. Treatments included manure slurry intended to mimic pen run-off water (n = 4 pens), a bacteriophage cocktail (n = 4), a combination of both treatments (n = 5), and a control group (n = 5) that received no treatment. Environment samples from 18 feedlot pens and fecal grabs, hide swabs, and subiliac lymph nodes from 178 cattle were collected and selectively enriched for Salmonella, and Salmonella isolates were sequenced. The combination treatment was most effective at reducing Salmonella, and the prevalence was significantly lower compared with the control group for rump swabs on Days 14 and 21. The treatment impact on Salmonella in the lymph nodes could not be determined due to low prevalence. The reduction on cattle hides suggests that bacteriophage or water treatments applied to the feedlot pen surface may reduce Salmonella populations in cattle during the pre-harvest period, resulting in reduced contamination during slaughter and processing.

Effect of vitamin D source and dietary cation-anion difference in peripartum dairy cows on calcium homeostasis and milk production.

The objective of this experiment was to determine the effects of dietary vitamin D source on serum calcium (Ca), urinary Ca excretion, and milk production when fed in combination with a prepartum acidogenic negative dietary cation-anion difference (DCAD) diet. Nonlactating, pregnant multiparous cows (n = 15), balanced for breed (Holstein n = 9 and Jersey n = 6), and previous mature equivalent milk production, were assigned to one of three treatments (five cows/treatment), consisting of a control (PCH; positive DCAD, 8.9 mEq/100 g DM) and two negative DCAD diets (-15.4 mEq/100 g DM), one with vitamin D3 (cholecalciferol; NCH) and one with 25-hydroxyvitamin D3 (calcidiol; NCA; DSM nutritional products). The treatments were formulated to provide 1.95 mg/d of vitamin D and were fed 28 d prior to expected calving date. Delivery of vitamin D sources was accomplished by manufacture of a pellet and 2 kg of these pellets were individually fed simultaneously each day along with 2 kg of ground corn daily at 0800 hours. Negative DCAD treatments were formulated to provide 0.46 kg/d of Animate (Phibro Animal Health) and, if needed, additional Animate was top-dressed at each feeding to achieve a urine pH between 5.5 and 6.0 based on the previous day's urine pH. Close-up cows had ad libitum access to chopped bermudagrass (Cynodon dactylon L.) hay and hay intake was measured using SmartFeed Pro systems (C-Lock Inc.; Rapid City, SD). Prepartum urine and serum samples were collected weekly and serum was collected 36, 48, and 72 h post-calving. Prepartum dry matter intake (DMI) as a percent of body weight was not (P = 0.66) affected by treatments. Cows fed NCH and NCA had greater (P = 0.02) prepartum serum Ca than PCH and tended to have greater urinary Ca excretions (P = 0.10). Average postpartum serum Ca (mg/dL) was greater (P = 0.05) for cows fed NCH (8.8) compared with PCH (7.8), whereas NCA (8.4) was numerically intermediate and not (P > 0.05) different from either of the other treatments. Postpartum DMI was not affected by treatment (P = 0.39). Daily milk yield (MY) (kg/d) was greatest (P < 0.01) for NCA (37.5) compared with the other treatments and NCH (34.1) was intermediate and greater than PCH (29.9). These results suggest that an acidogenic prepartum diet in combination with vitamin D was effective in maintaining peripartum serum Ca and the 25-hydroxy form of vitamin D improved MY compared with NCH in early lactation.

Varied diets: implications for lamb performance, rumen characteristics, total antioxidant status, and welfare.

Intensive pastoral systems have moved away from diverse and varied diets towards overly simple monotonous diets. Feed choice through time is an obsolete way of providing forage to animals, as intensive management schemes generally allocate a single herbage or a dyad mixed sward. Monotonous feeding regimes impose nutritional repetition, which may impair animal performance and welfare. The objective of this experiment was to determine the impact of a diverse diet [DIV; free choice from perennial ryegrass (Lolium perenne L.), plantain (Plantago lanceolata L.), alfalfa (Medicago sativa L.), and chicory (Cichorium intybus L.) at all times], a varied diet [VAR; choice from ryegrass and plantain in the AM (0700-1600 h), and chicory and alfalfa in PM (1600-0700 h)], and a single forage diet of alfalfa [SFA; alfalfa at all times], on DMI, performance, and welfare of lambs. Six-month-old Coopworth ram lambs (n = 21) were offered their respective fresh-forage treatment (n = 7) diet indoors for 20 d. The DIV lambs consumed 1.64 ± 0.03 kg DM/d (mean ± SEm), which was 6% more (P < 0.05; 1.54 ± 0.03 kg DM/d) than the SFA and were not different (P > 0.05; 1.59 ± 0.03 kg DM/d) to the VAR lambs. Average daily gain (ADG) of DIV (296 g/d) and VAR (378 g/d) was 30% and 67% greater (P < 0.05) than that in the SFA lambs (227 g/d), respectively. The VAR lambs had 28% greater (P < 0.05) ADG than the DIV lambs. Differences among treatments were detected (P < 0.05) for the proportion of the day spent conducting the following behaviors: eating, ruminating, idling, lying, and standing. In addition, the number of bouts of stereotypic behaviors recorded from the SFA lambs (13.2 ± 2.2) was 150% greater (P < 0.05) than the DIV (5.1 ± 1.0) and VAR (5.5 ± 1.0) lambs. Our results suggest that the varied diet offered can improve animal performance and welfare compared to a monotonous SFA diet. Feeding management to provide a varied diet can improve performance relative to giving lambs free choice from taxonomically diverse forage options. Moreover, performance is affected by more than the primary chemical composition of the diet consumed, but how the diet is presented through time and the herbage species and quantities of each that are consumed to reach that chemical composition.

Nitrogen Balance of Dairy Cows Divergent for Milk Urea Nitrogen Breeding Values Consuming Either Plantain or Perennial Ryegrass.

Inefficient nitrogen (N) use from pastoral dairy production systems has resulted in environmental degradation, as a result of excessive concentrations of urinary N excretion leaching into waterways and N2O emissions from urination events into the atmosphere. The objectives of this study were to measure and evaluate the total N balance of lactating dairy cows selected for milk urea N concentration breeding values (MUNBVs) consuming either a 100% perennial ryegrass (Lolium perenne L.) or 100% plantain (Plantago lanceolata L.) diet. Sixteen multiparous lactating Holstein-Friesian × Jersey cows divergent for MUNBV were housed in metabolism crates for 72 h, where intake and excretions were collected and measured. No effect of MUNBV was detected for total N excretion; however, different excretion characteristics were detected, per urination event. Low MUNBV cows had a 28% reduction in the concentration of urinary urea nitrogen (g/event) compared to high MUNBV cows when consuming a ryegrass diet. Cows consuming plantain regardless of their MUNBV value had a 62% and 48% reduction in urinary urea nitrogen (g/event) compared to high and low MUNBV cows consuming ryegrass, respectively. Cows consuming plantain also partitioned more N into faeces. These results suggest that breeding for low MUNBV cows on ryegrass diets and the use of a plantain diet will reduce urinary urea nitrogen loading rates and therefore estimated nitrate leaching values, thus reducing the environmental impact of pastoral dairy production systems.

Technical note: using an automated head chamber system to administer an external marker to estimate fecal output by grazing beef cattle.

The objective of this experiment was to determine if titanium dioxide (TiO2) dosed through an automated head chamber system (GreenFeed; C-Lock Inc., Rapid City, SD, USA) is an acceptable method to measure fecal output. The GreenFeed used on this experiment had a 2-hopper bait dispensing system, where hopper 1 contained alfalfa pellets marked with 1% titanium dioxide (TiO2) and hopper 2 contained unmarked alfalfa pellets. Eleven heifers (BW = 394 ± 18.7 kg) grazing a common pasture were stratified by BW and then randomized to either 1) dosed with TiO2-marked pellets by hand feeding (HFD; n = 6) or 2) dosed with TiO2-marked pellets by the GreenFeed (GFFD; n = 5) for 19 d. During the morning (0800), all heifers were offered a pelleted, high-CP supplement at 0.25% of BW in individual feeding stanchions. The HFD heifers also received 32 g of TiO2-marked pellets at morning feeding, whereas the GFFD heifers received 32 g of unmarked pellets. The GFFD heifers received a single aliquot (32 ± 1.6 g; mean ± SD) of marked pellets at their first visit to the GreenFeed each day with all subsequent 32-g aliquots providing unmarked pellets; HFD heifers received only unmarked pellets. Starting on d 15, fecal samples were collected via rectal grab at feeding and every 12 h for 5 d. A two-one sided t-test method was used to determine agreement and it was determined that the fecal output estimates by HFD and GFFD methods were similar (P = 0.04). There was a difference (P < 0.01; Bartlett's test for homogenous variances) in variability between the dosing methods for HFD and GFFD (SD = 0.1 and 0.7, respectively). This difference in fecal output variability may have been due to variability of dosing times-of-day for the GFFD heifers (0615 ± 6.2 h) relative to the constant dosing time-of-day for HFD and constant 0800 and 2000 sampling times-of-day for all animals. This research has highlighted the potential for dosing cattle with an external marker through a GreenFeed configured with two (or more) feed hoppers because estimated fecal output means were similar; however, consideration of the increased variability of the fecal output estimates is needed for future experimental designs.

Negative effects of energy supplementation at peak lactation of sheep can be offset by the addition of Lactobacillus-fermented plant extracts.

Energy supplementation may reduce oxidative stress by correcting a negative energy balance, but in some contexts, it has been shown to increase oxidative stress, especially at peak lactation. The current experiment examined if a pelleted energy supplement with or without the addition of Lactobacillus-fermented seaweed or seaweed plus terrestrial plants extracts affected oxidative stress of ewes from late gestation through to weaning and ewe and lamb production from lambing to weaning. Treatments were either no supplement (CON-), a pelleted supplement only (CON+, 100 g/ewe per d), CON+ with seaweed extract only (SWO, 10 mL/ewe per day), or CON+ with seaweed plus an arrangement of terrestrial plant extract (SWP, 10 mL/ewe per d). Ewes (n = 160; mean initial BW = 72.3 ± 9.5 kg [mean ± SD]) were randomized to pastures (n = 4 pastures per treatment with 10 ewes each). After lambing, ewes with twins were reallocated to pastures (n = 3 pastures per treatment with 10 ewes each) according to lambing date. At 4 wk in milk, supplementation tended to reduce total antioxidant status (TAS; P = 0.10) and increased glutathione peroxidase (GPx) activity compared with nonsupplemented ewes (P = 0.04). The addition of seaweed and terrestrial plants extracts to the concentrate, that is, SWO and SWP, increased TAS and reduced GPx activity compared with CON+ (P < 0.01). Supplementation increased milk yield at weeks 4, 6, and 8 of lactation, and protein, lactose, and total milk solids yield at peak lactation (week 4; P < 0.05). The CON- ewes had greater somatic cell count than the supplemented ewes at weeks 4, 8, and 10 of lactation (P = 0.03). Our results suggest that energy supplementation, alone, increases oxidative stress of lactating ewes, which may relate to increased oxidative phosphorylation. Most importantly, these results indicate that in situations where energy supplementation is needed to increase animal performance, negative effects of energy supplementation around peak lactation can be offset by the addition of Lactobacillus-fermented plant extracts (SWO and SWP) to improve antioxidant status.

Cow efficiency: modeling the biological and economic output of a Michigan beef herd.

In recent decades, beef cattle producers have selected cattle for biological traits (i.e., improved growth) to maximize revenue, leading to an increase in average cow body size. However, matching cow size to the production environment would allow producers to maximize productivity and economic returns per unit of land. This may help meet the goals of sustainable intensification, but environmental complexity and varying cow-calf production systems dictates a regional approach. The objective of this experiment was to examine the biological efficiency and economic returns of a Northern Michigan cow-calf system. We hypothesized that biological efficiency and economic returns would decrease with increasing cow body size. Data were collected from a Red Angus cow herd located at the Lake City AgBio Research Center in Lake City, MI from 2011 to 2018 on cow age, weight, and body condition score at weaning, and subsequent 205 d adjusted calf weaning weight (WW), sex, and yearling weight. Biological efficiency was defined as WW as a percentage of cow body weight (DBW). Enterprise budgeting techniques were used to calculate expected net returns from 2011 to 2018 after classifying cows into 11 BW tiers at 22.67 kg intervals beginning at 430.83 kg. Forward-looking net present value (NPV) was calculated using the same tier system, for a 10-yr production cycle with the baseline being a 200 d grazing season. Weaning weight increased with increasing DBW (P < 0.01), but the percentage of cow body weight weaned was reduced by -38.58 × Ln(DBW) (P < 0.01). This led to cows weaning 26.38 kg/ha more with every 100 kg drop in DBW. Expected net returns from 2011 to 2018 did not differ by DBW tier on a per cow basis but did on a per ha basis with a decrease in $10.27/ha with each increase in DBW tier (P < 0.01). Net present value was maximized in the baseline scenario at 453.51 kg DBW and decreased in value as DBW increased. These results suggest that for a Northern Midwestern cow-calf herd, comparatively lighter cows provide a higher economic value on a land basis.

Stocking rate impacts performance and economics of grazing beef steers on mixed-grass prairies of the Southern Great Plains.

Stocking rate is a fundamental management factor that has major impacts on animal performance, profitability, and long-term sustainability of native range ecosystems. This research was conducted to determine the effects of stocking rate on performance and economics of growing steers grazing a mixed-grass prairie on a rolling upland red shale ecological site at the Marvin Klemme Range Research Station (35° 25' N 99° 3' W). The recommended sustainable stocking rate at this location is suggested to be 25 animal unit days (AUD)/ha. Steers [n = 836, initial body weight (BW) ± SD = 216 ± 11.7 kg] grazed at seven stocking rates ranging from 4.13 ha/steer to 1.83 ha/steer over a 7-yr period, from 1990 to 1996, with year considered the random replication. During the experimental period, overall climatic conditions were favorable for forage production with average growing season precipitation of 118% of the long-term average over the 7-yr experiment, and only 1 yr (1994 with only 57% of the long-term average) with growing season precipitation substantially less than the long-term average. Over the entire summer grazing season, average daily gain (ADG) decreased linearly (P < 0.01) with increasing stocking rate, such that for each additional hectare available per steer ADG increased by 0.05 kg/d (R 2 = 0.88). Contrary to ADG, BW gain per hectare over the grazing season increased linearly (P < 0.01) with increasing stocking rate, as stocking rate increased from 4.13 ha/steer to 1.83 ha/steer BW gain per hectare doubled from 33.1 kg/ha to 66.8 kg/ha, respectively. With land costs included in the economic analysis, net return per hectare increased linearly (P < 0.01) from $13 [U.S. Dollars [USD]) at the 4.13 ha/steer to $52/ha at the 1.83 ha/steer. For each additional hectare per steer, net return was reduced by $15.80 (USD)/steer and $15.70 (USD)/ha. In favorable climatic conditions, such as during this 7-yr experiment, economically optimal stocking rates can be more than doubled compared with the stocking rate recommended by the United States Department of Agriculture (USDA) Soil Conservation Service. Increasing stocking rates decrease individual animal performance but maximize BW gain per hectare, which leads to the increasing economic returns observed. Research is needed to determine the long-term implications of these stocking rates during unfavorable growing conditions and setting stocking rates based on seasonal weather patterns and extended weather outlook predictions.

How Dietary Diversity Enhances Hedonic and Eudaimonic Well-Being in Grazing Ruminants.

Ruminants evolved in diverse landscapes of which they utilized, by choice, a diverse arrangement of plants (grasses, forbs, and trees) for food. These plants provide them with both primary (carbohydrates, protein, etc.) and secondary (phenolics, terpenes, etc.) compounds (PPC and PSC, respectively). As no one plant could possibly constitute a "balanced-diet," ruminants mix diets so that they can exploit arrangements of PPC to meet their individual requirements. Diet mixing also allows for ruminants to ingest PSC at levels, acquiring their benefits such as antioxidants and reduced gastrointestinal parasites, without overstepping thresholds of toxicity. Meeting dietary requirements is assumed to provide satisfaction through achieving positive internal status and comfort, thereby a sense of hedonic (happiness through pleasure) well-being. Furthermore, choice including dietary choice is a factor influencing well-being of ruminants in a manner akin to that in humans. Choice may facilitate eudaimonic (happiness through pursuit of purpose) well-being in livestock. Nutritional status plays an integral role in oxidative stress, which is linked with illness. Several diseases in livestock have been directly linked to oxidative stress. Mastitis, metritis, hypocalcaemia, and retained placenta occur in animals transitioning from dry to lactating and have been linked to oxidative stress and such a stress has likewise been linked to diseases that occur in growing livestock as well, such as bovine respiratory disease. The link between physiological stress and oxidative stress is not well-defined in livestock but is evident in humans. As dietary diversity allows animals to select more adequately balanced diets (improved nutrition), take advantage of PSC (natural antioxidants), and allows for choice (improved animal well-being) there is a strong possibility for ruminants to improve their oxidative status and thus health, well-being, and therefor production. The purposes of this review are to first, provide an introduction to oxidative and physiological stress, and nutritional status as effected by dietary diversity, with special attention to providing support and on answering the "how." Second, to provide evidence of how these stresses are connected and influence each other, and finally discuss how dietary diversity provides a beneficial link to all three and enhances both eudaimonic and hedonic well-being.

Measuring the respiratory gas exchange by grazing cattle using an automated, open-circuit gas quantification system.

Ruminants are a source of enteric CH4, which has been identified as an anthropogenic greenhouse gas that contributes to climate change. With interest in developing technologies to decrease enteric CH4 emissions, systems are currently being developed to measure CH4 emissions by cattle. An issue with grazing cattle is the ability to measure CH4 emissions in open-air environments. A scientific instrument for this task is an automated, open-circuit gas quantification system (GQS; C-Lock, Inc., Rapid City, SD). The GQS is a head chamber that grazing cattle occasionally visit (3 to 8 min/visit; 3 to 6 visits/d), and while the animal consumes a small portion of bait (0.5 to 1.0 kg/visit), the GQS captures the animal's breath cloud by exhausting air through the GQS. The breath cloud is then analyzed for CH4, CO2, and O2 concentrations. Data are hourly uploaded to a server where it is processed using algorithms to determine total daily fluxes. Several factors affect emission estimates generated by the GQS including the animal's visitation rate, length of sampling period, and airflow through the system. The location of the GQS is an important factor in determining the cattle's willingness to visit. Further, cattle need to be trained to use the GQS, which normally requires 4 to 8 wk. Several researchers have shown that 30 or more visits are required to obtain high-quality estimates of gas fluxes. Once cattle are trained to use the GQS, the bait delivery rate has little effect on the animal's willingness to use the system. Airflow through the GQS is an important factor, but as long as airflow is maintained above 26 L/s the breath-cloud capture seems nearly complete. There is great concern regarding circadian variation in the instantaneous production rates of CH4 because the GQS normally only spot-samples 2 to 4 times/d. Preliminary analysis has shown that variation in the instantaneous production rates of CH4 do not vary as greatly with grazing cattle compared with meal-fed cattle. It seems that increasing the visitation length decreases variation in estimated emissions, but there is a diminishing return to increasing visitation length. The GQS is a useful tool for researching the nutrition and emissions of grazing cattle, but great care must be taken to obtain the best quality data possible for use in this high-impact research.