Composition of the rumen microbiome and its association with methane yield in dairy cattle raised in tropical conditions.

BACKGROUND: Methane (CH4) emissions from rumen fermentation are a significant contributor to global warming. Cattle with high CH4 emissions tend to exhibit lower efficiency in milk and meat production, as CH4 production represents a loss of the gross energy ingested by the animal. The objective of this study was to investigate the taxonomic and functional composition of the rumen microbiome associated with methane yield phenotype in dairy cattle raised in tropical areas. METHODS AND RESULTS: Twenty-two Girolando (F1 Holstein x Gyr) heifers were classified based on their methane yield (g CH4 / kg dry matter intake (DMI)) as High CH4 yield and Low CH4 yield. Rumen contents were collected and analyzed using amplicon sequencing targeting the 16 and 18S rRNA genes. The diversity indexes showed no differences for the rumen microbiota associated with the high and low methane yield groups. However, the sparse partial least squares discriminant analysis (sPLS-DA) revealed different taxonomic profiles of prokaryotes related to High and Low CH4, but no difference was found for protozoa. The predicted functional profile of both prokaryotes and protozoa differed between High- and Low CH4 groups. CONCLUSIONS: Our results suggest differences in rumen microbial composition between CH4 yield groups, with specific microorganisms being strongly associated with the Low (e.g. Veillonellaceae_UCG - 001) and High (e.g., Entodinium) CH4 groups. Additionally, specific microbial functions were found to be differentially more abundant in the Low CH4 group, such as K19341, as opposed to the High CH4 group, where K05352 was more prevalent. This study reinforces that identifying the key functional niches within the rumen is vital to understanding the ecological interplay that drives methane production.

Ration particle size has different effects on digestive but not production parameters in higher-yielding (Holstein) compared to lower-yielding (Girolando) cows.

The aim of the study was to evaluate the effect of total mixed ration particle size (length) and breed of cow on intake dynamics, animal performance and CH4 emissions, comparing high yielding Holstein and low yielding Girolando cows. The experimental design was 2 × 2 Latin Square arranged as a crossover factorial scheme with two diets (short particle size, SPS and long particle size, LPS) and the two breed compositions. The design comprised two periods of 26 d each, where all data collection was performed at cow level. No influence of the particle size occurred for the passage rate, neutral detergent fiber digestibility, performance and milk composition, methane emissions or ruminal fermentation parameters. Girolando cows had greater dry matter intake (DMI) when fed SPS, while Holsteins had the same (P < 0.05). Girolando cows had lower dry matter digestibility when fed LPS compared to SPS, while Holsteins had the opposite effect (P < 0.05). Also, the digestibility of crude protein and non-fibrous carbohydrates decreased in Girolando cows fed LPS, but not in Holsteins (P < 0.05). Girolando cows reduced DMI by 10.6% when fed LPS diet (P < 0.05). Girolando had an increased eating rate (+24 g of DM/min; P < 0.05) compared to Holstein cows, but Holstein cows had a lower CH4 intensity (by 29.7%: P < 0.05). Girolando cows increased the dry matter intake when fed a diet with short particle size, while the same did not happen in Holsteins. Dry matter digestibility increased in Holsteins when fed long particle size, while the opposite was observed in Girolando cows. Nutrient digestibility was reduced in Girolando cows when fed short particle size. Particle size did not influence eating time, eating rate, feed trough visits, visits with intake, milk yield and composition regardless of the breed. Reducing particle size increased CH4 intensity in both breeds.

Sensor validation to record rumination and analysis of behavioral parameters of dairy Gyr heifers in feedlot systems.

The use of sensors for livestock monitoring has grown in the last decade, motivated not only by the search for improvements in animal production and health, but also by the better use of physical, financial, and human resources in the management of livestock. Since precision livestock farming depends on technological innovation, including the use of sensors, it is essential to validate their applicability in confined animals. Therefore, the objective was to evaluate the functioning of the SCR Heatime® HR System sensor in heifers and analyze the behavioral differences of these animals in two feedlot systems (tie-stall and loose-housing). Eleven Gyr heifers of 10 months of age and an average body weight of 179 ± 26 kg were used. Animals were equipped with the SCR Heatime® HR System 7 days before the evaluations for adaptation, with the behavioral and system studies carried out during two periods each of 5 days, for 8 h a day. Five heifers were housed in tie-stall bedding and six were housed in loose-housing. After the evaluations for a period, animals have been switched systems in the following period. While the animals had the sensors attached to their bodies, behavioral evaluations were also performed visually, every 3 min by two evaluators per system. Behavior activities were characterized as standing, lying, idle standing, idle lying, ruminating standing, ruminating lying, feed, and water intake. The regression for the rumination activity recorded between the sensor and the visual assessment was significant only for loose-housing (P = 0.0002), but the Pearson correlation between both was negative and low (r = - 0.25; P = 0.0002). The sensor overestimated rumination by 27.3% in loose-housing (28 vs. 22 min/2 h) and 38.5% in tie-stall (36 vs. 26 min/2 h). Thus, when considering the different feedlot systems, validation was not possible due to the overestimation of time spent on rumination activity determined by the sensor. In the behavioral comparison between the systems by visual assessment, there was a significant difference (P < 0.05) for the behaviors of motor activity, idle lying, total idle time, and feed intake between the animals in the two housing systems. As for idle standing, ruminating standing, total rumination time, and water intake, there was no difference (P > 0.05). However, the time spent ruminating lying was greater from 10:00 to 12:00 h (43 ± 3 min/2 h) in the tie-stall, whereas in the loose-housing the animals distribute more uniformly their rumination from 08:00 to 16:00 h (26 min/2 h on average). Therefore, the use of the SCR Heatime® HR System sensor is not recommended for Gyr heifers housed in tie-stall and loose-housing systems. Regarding the daytime range of rumination and the accuracy improvements of similar sensors, it is recommended to develop them in both feedlot systems using the periods of less rumination in early morning in tie-stall and late afternoon in loose-housing.

Screening microchip sites to predict body temperature in young calves.

Thermal microchip sensors can automate body temperature measurements. The best site of implantation is still unknown, and the accuracy and precision of body temperature predictions based on microchip data need to be investigated. The aim of this study was to investigate the best site for microchip implant for monitoring body temperature in dairy calves. Seventeen calves were used (32.2 ± 5.2 kg of body weight) and the microchips were implanted four days after birth. The microchips were implanted at navel, ear and tail base (subcutaneous), neck (cleidocephalicus) and internal face of leg (gracilis) (intramuscular). Rectal temperature (RT, °C), obtained with a clinical thermometer, was considered as core temperature. Air temperature (AT), relative humidity (RH) and the temperature and humidity index (THI) were evaluated at the same time of rectal and microchip temperature measurements over 56 days. The range of AT, RH and THI was 7.6-34.4 °C, 17.5-99.0% and 50.6 to 91.5. The average for rectum, ear, neck, tail, leg, and navel were 38.7; 36.9; 38.0; 37.0, 37.8 and 37.0 °C. The intramuscular implantations had closest values to RT. The correlations between RT and ear, neck, tail, leg, and navel temperatures were 0.56, 0.60, 0.60, 0.53 e 0.48. The RT prediction based on microchip data had precision (rc) ranged between 0.49 and 0.60 and accuracy (Cb) between 0.79 and 0.88. The inclusion of AT, RH and THI as predictive variables in models decrease the mean absolute error (23%) and increase the precision (21.3%) and accuracy (10.2%). The Concordance Correlation Coefficient and root-mean-square error for equations using tail or neck microchips were 0.68 and 0.67, and 0.29 and 0.28 °C, respectively. The tail base is a promising site for microchip implantation to predict rectal temperature. The inclusion of air temperature as a predictive variable in the models is recommended.

Intake, digestibility, nitrogen balance and performance of crossbreed Boer goats fed with diets containing saltbush (Atriplex nummularia L.) and spineless cactus (Opuntia ficus-indica).

Saltbush and spineless cactus are adapted to arid and semiarid regions and used as an important forage resource in ruminants' diet. However, spineless cactus restricts production due to its low crude protein and NDF levels and high salt and oxalate contents, which can limit the digestibility and intake of dietary nutrients. Therefore, this experiment was conducted to evaluate the best ratio levels of saltbush associated with spineless cactus in diets for crossbreed Boer goats through ingestion, water balance, digestibility, nitrogen balance, growth and carcass weight. Twenty-four castrated crossbred Boer (Boer × Brazilian native) goats 6 months of age and average body weight of 20.28 kg were utilized. The animals were weighed and distributed in randomized blocks in four experimental diets with saltbush of 8.4, 18.8, 31.2 and 48.3%. The addition of saltbush hay promoted quadratic behaviour (P < 0.05) in intake of dry matter and nutrients. There was no effect (P < 0.05) from the addition of saltbush hay on the digestibility of organic matter, total carbohydrates, non-fibrous carbohydrates and neutral detergent fibre, whereas there was an increase in dry matter. The crude protein digestibility behaved quadratically (P = 0.06), where the maximum digestibility was obtained with the addition of 31.2% of hay. The balance and net nitrogen utilization presented a quadratic effect (P < 0.01). Saltbush in rations for goats presented promising results, the growth rate (0.15 kg/day) obtained in diet with a lower proportion of saltbush, would satisfy smallholders when considering that this species, associated with spineless cactus, may reduce the use of concentrate feeds; however, the diet with 31.2% of saltbush hay provided the biggest gain in body and carcass weight of the goats.

Effects of exogenous amylase on the in vitro digestion kinetics of whole-crop maize silages made from flint or dent grain type at different phenological stages grown in tropical condition.

The effect of exogenous amylase on the in vitro rumen digestion kinetics of whole-crop maize silage made from dent (RB9004) or flint grain type (RB9308) was evaluated at different phenological stages: soft dough (SOD), early dent (EAD), ½ milkline (½M) and ¾ milkline (¾M). Forage was harvested from 70 to 110 days after sowing. Two rumen-cannulated cows receiving or not exogenous amylase (0.7 g/kg dry matter-DM, provided to achieve 396 kilo Novo units of amylase activity/kg of TMR DM) were used as donor of ruminal fluid. The in vitro gas production kinetics was evaluated according to a dual-pool logistic model. The chemical composition and gas production kinetics were affected by the hybrid and phenological stages. The flint hybrid had lower range for chemical analysis among physiological stages. Harvesting at ½M and ¾M improved DM content, bromatological composition and silage quality parameters compared to dent or flint types. Amylase (i) increased methane (CH4 ) production and in vitro dry matter digestibility (IVDMD) in ½M stage, (ii) improved digestion kinetics by reducing lag time and increasing total gas production and fermentation rates of non-fibrous carbohydrates (NFC) and fibrous carbohydrates (FC), and (iii) increased extent and fermentation rate of NFC and increased fermentation rate of FC fraction in whole-crop maize silages produced from dent or flint types in all phenological stages. Harvesting between ½M and ¾M is the best phenological stage to improve chemical composition and silage quality parameters. Exogenous amylase showed improvements on fibre digestion of silages at ½M and ¾M phenological stages in both grain types of corn.

Crude glycerin combined with sugar cane silage in lamb diets.

This study aimed to evaluate the effect of the level of crude glycerin (CG) on in vitro fermentation kinetics (0, 20, 40, 60, and 80 g/kg DM of sugar cane silage), on in vitro neutral detergent fiber (NDF) degradation (0, 30, 60, and 90 g/kg DM of sugar cane silage), and intake and digestibility of nutrients and nitrogen balance (0, 20, 55, 82, and 108 g/kg DM of sugar cane silage) in lambs. The in vitro trials were conducted in a completely randomized design with three repetitions. The in vivo trial was conducted in a Latin square design with five repetitions (5 × 5). For variables in which the F test was considered significant, the statistical interpretation of the effect of CG substitution levels was carried out through regression analyses. Kinetic parameters were not affected by CG inclusion. On in vitro NDF degradation, a significant effect of CG levels was observed on the potentially degradable fraction of NDF, the insoluble potentially degradable fraction of NDF, and the undegradable NDF fraction. The intake and digestibility of nutrients and nitrogen balance were not affected by CG inclusion. The CG levels change in vitro NDF degradability parameters; however, there were no changes in animal intake, digestibility, and nitrogen balance with the inclusion levels used.

Detoxified castor meal in substitution of soybean meal in sheep diet: growth performance, carcass characteristics and meat yield.

The aim of this study was to evaluate the intake, digestibility, performance, and carcass characteristics of lambs fed different levels of replacement (0, 15, 30, and 45 % based on dry matter, DM) of soybean meal (SM) by detoxified castor meal (DCM). Twenty-four and 32 intact hair lambs of nondescript breed (21.7 ± 2.6 kg of initial average body weight and approximately 10 months old) were used, respectively, in the intake and digestibility and performance experiments. The diets were composed of buffel grass hay, ground corn grain, and different levels of SM, DCM, and urea, in a roughage-to-concentrate ratio of 40:60. There was no effect of treatments on DM intake. However, crude protein (CP) and neutral detergent fiber (NDF) intakes were higher at 30 and 45 % than at 0 and 15 % of DCM, which in turn showed higher intake of non-fiber carbohydrates (NFC) (P < 0.05). The organic matter, CP, and NDF digestibilities were not affected, but the digestibility of NFC was lower at 30 and 45 % than at 0 % of DCM (P < 0.05). The average daily gain, feed conversion, slaughter and carcass weights, chilling losses, ribeye area, and absolute values and yields of neck, ribs, loin, and leg were not affected. However, the carcass yield was lower at 45 % of DCM and the absolute value of shoulder was lower at 30 and 45 % of DCM (P < 0.05). The replacement of SM by DCM up to 45 % in the feed of lambs did not negatively affect the intake, digestibility, performance, and main carcass features.

Silage or fresh by-product of peach palm as roughage in the feeding of lambs.

The objective of this study was to evaluate intake and apparent digestibility of agro-industrial by-product of peach palm in diets for lambs. Twenty castrated, crossbred Santa Ines lambs, with average age of 150 days and body weight of 22.4 ± 3.4 kg, were distributed in a completely randomized design with four experimental diets composed of the following: fresh by-product of peach palm enriched with urea + ammonia sulfate (FU); fresh peach palm by-product + concentrate (FP); silage of peach palm by-product + concentrate (SP); and silage of peach palm by-product enriched with 15% of cornmeal + concentrate (SPC). Intake was recorded daily, and the digestibility coefficients were estimated with the internal marker indigestible acid detergent fiber (iADF). Diet FU resulted in the lowest intake and digestibility of the nutrients evaluated. Animals receiving diet FP showed higher intakes of dry matter (DM), organic matter (OM), crude protein (CP), neutral detergent fiber (NDF), total digestible nutrients (TDN), and digestible energy (DE) in relation to animals fed diets SP and SPC. Diets SP and SPC showed higher coefficients of digestibility of DM, OM, CP, and NDF than diet FP. Diet SP reduced the intakes of DM, OM, ether extract (EE), non-fibrous carbohydrate (NFC), TDN, and DE and the digestibility coefficients of DM, OM, and NFC as compared with diet SPC. Feedlot lambs fed a diet with fresh peach palm by-product + concentrate (diet FP) have higher nutrient intake.

Performance and characteristics of carcass and non-carcass components of lambs fed peach-palm by-product.

The objective of this study was to evaluate the effects of supplying the by-product of peach-palm (Bactris gasipaes) on performance and characteristics of carcass and non-carcass components of feedlot lambs. Twenty Santa Ines lambs of 150 days average age and 22.4 ± 3.4 kg body weight were confined in individual pens. A completely randomized design was utilized with four experimental diets composed of: fresh peach-palm by-product enriched with urea, fresh peach-palm by-product + concentrate, silage of peach-palm by-product + concentrate, and silage of peach-palm by-product enriched with 15 % corn meal + concentrate. Intake was evaluated daily, and at the end of 42 days of experiments, lambs were slaughtered and the characteristics of carcass and non-carcass parts were evaluated. Performance and carcass characteristics showed differences between the animals' intake of total mixed rations (TMR) and only the diet with roughage. For the lambs that intaked TMR, the form of utilization of roughage (fresh or as silage) affected animal performance but did not change the carcass characteristics. Dry matter intake and feed conversion were influenced by the form of utilization of the silage (with and without additive). Providing fresh by-product plus concentrate improves lamb performance but does not interfere in the carcass characteristics, compared with the use of by-product in the form of silage.

How does reproduction account for dairy farm sustainability?

Sustainability - the new hype of the 21st century has brought discomfort for the government and society. Sustainable agriculture is essential to face our most concerning challenges: climate change, food security, and the environmental footprint, all of which add to consumers' opinions and choices. Improvements in reproductive indexes can enhance animal production and efficiency, guaranteeing profit and sustainability. Estrus detection, artificial insemination (AI), embryo transfer (ET), estrus synchronization (ES), and multiple ovulations are some strategies used to improve animal reproduction. This review highlights how reproductive strategies and genetic selection can contribute to sustainable ruminant production. Improved reproductive indices can reduce the number of nonproductive cows in the herd, reducing methane emissions and land use for production while preserving natural resources.

Evaluation of Ingestive Behavior, Ruminal and Blood Parameters, Performance, and Thermography as a Phenotypic Divergence Markers of Residual Feed Intake in Rearing Dairy Heifers.

The objectives of this study were: (1) to identify and rank phenotypically divergent animals for residual feed intake (RFI) regarding their efficiency (high: HE or low: LE); (2) to evaluate their relationships with ingestive behavior, ruminal and blood parameters, performance, and infrared thermography; and (3) to determine if such measurements can be used as feed efficiency markers in rearing dairy heifers. Thirty-eight heifers, 143 d ± 4 (Mean ± SD) of age and 108.7 kg ± 17.9 of body weight were used. The animals were fed with a total mixed ration during the 91 d of the trial. A phenotypic divergence of DMI for RFI was observed between -0.358 and 0.337 kg/d for HE and LE, respectively. Dry matter intake (DMI) was lower in the HE (2.5 kg DMI/d vs. 3.1 kg DMI/d), as was the number of visits to the feed bin with consumption (59 vs. 71). Feed intake was the best predictor of said divergence. Water intake and number of visits to the feed bin were presented moderate correlations with RFI. The ruminal fermentation variables, blood metabolites, blood hormones (such as the other ingestive behavior variables), and infrared thermography were not able to accurately predict HE or LE animals.

Taxonomic and predicted functional signatures reveal linkages between the rumen microbiota and feed efficiency in dairy cattle raised in tropical areas.

Ruminants digest plant biomass more efficiently than monogastric animals due to their symbiotic relationship with a complex microbiota residing in the rumen environment. What remains unclear is the relationship between the rumen microbial taxonomic and functional composition and feed efficiency (FE), especially in crossbred dairy cattle (Holstein x Gyr) raised under tropical conditions. In this study, we selected twenty-two F1 Holstein x Gyr heifers and grouped them according to their residual feed intake (RFI) ranking, high efficiency (HE) (n = 11) and low efficiency (LE) (n = 11), to investigate the effect of FE on the rumen microbial taxa and their functions. Rumen fluids were collected using a stomach tube apparatus and analyzed using amplicon sequencing targeting the 16S (bacteria and archaea) and 18S (protozoa) rRNA genes. Alpha-diversity and beta-diversity analysis revealed no significant difference in the rumen microbiota between the HE and LE animals. Multivariate analysis (sPLS-DA) showed a clear separation of two clusters in bacterial taxonomic profiles related to each FE group, but in archaeal and protozoal profiles, the clusters overlapped. The sPLS-DA also revealed a clear separation in functional profiles for bacteria, archaea, and protozoa between the HE and LE animals. Microbial taxa were differently related to HE (e.g., Howardella and Shuttleworthia) and LE animals (e.g., Eremoplastron and Methanobrevibacter), and predicted functions were significatively different for each FE group (e.g., K03395-signaling and cellular process was strongly related to HE animals, and K13643-genetic information processing was related to LE animals). This study demonstrates that differences in the rumen microbiome relative to FE ranking are not directly observed from diversity indices (Faith's Phylogenetic Diversity, Pielou's Evenness, Shannon's diversity, weighted UniFrac distance, Jaccard index, and Bray-Curtis dissimilarity), but from targeted identification of specific taxa and microbial functions characterizing each FE group. These results shed light on the role of rumen microbial taxonomic and functional profiles in crossbred Holstein × Gyr dairy cattle raised in tropical conditions, creating the possibility of using the microbial signature of the HE group as a biological tool for the development of biomarkers that improve FE in ruminants.

Feed intake, milk production and metabolism of Holstein, Gyr and Girolando-F1 heifers with high body condition score during the transition period.

The transition period in taurine dairy cows is widely reported in the literature. However, little is known about the metabolism of zebu animals and their crossbreeding with taurine breeds during this phase. Considering the importance of these breeds in tropical and subtropical regions, this study aimed to evaluate the feed intake, milk production and hepatic metabolism in Holstein, Gyr and Girolando-F1 (½ Holstein × ½ Gyr) heifers presenting high body condition score (BCS) during the transition period (prepartum weeks -2 and -1 and postpartum weeks +1 and + 3). Twelve heifers of each genetic group were used, totaling 36 animals. Variables considered were blood metabolites related to liver function, dry matter intake (DMI), body condition score (BCS), body weight (BW), milk yield (MY), and fat and protein concentrations in milk. Gyr heifers had the lowest concentrations of paraoxonase in weeks -2 (43.13 U/mL), -1 (62.10 U/mL) and + 3 (77.89 U/mL), albumin in week -1 (3.07 g/dL), and the highest concentration of non-esterified fatty acids (NEFA) in weeks -2 (1.35 mmol/L) and -1 (1.19 mmol/L). ß-hydroxybutyrate (BHB) and NEFA values were negatively correlated with prepartum DMI (-0.82 and -0.57, respectively), while paraoxonase was positively correlated to DMI (0.54). Gyr cows were more susceptible to inflammation despite having intermediate BCS and lower milk yield. Girolando-F1 animals showed the highest BCS among groups, although their hepatic metabolism had better results than Gyr cows. Holstein animals had lower lipomobilization and higher DMI and MY between breeds. These results suggest that the metabolism of zebu and crossbred cows does not react equally to the metabolism of Holstein cows concerning stress factors such as transition period and obesity. Therefore, the present study addresses an emerging theme that highlights the need for differentiated management during the transition period between the different breeds studied in order to ensure the maximum health and welfare of these animals.

Quantification of methane emitted by ruminants: a review of methods.

The contribution of greenhouse gas (GHG) emissions from ruminant production systems varies between countries and between regions within individual countries. The appropriate quantification of GHG emissions, specifically methane (CH4), has raised questions about the correct reporting of GHG inventories and, perhaps more importantly, how best to mitigate CH4 emissions. This review documents existing methods and methodologies to measure and estimate CH4 emissions from ruminant animals and the manure produced therein over various scales and conditions. Measurements of CH4 have frequently been conducted in research settings using classical methodologies developed for bioenergetic purposes, such as gas exchange techniques (respiration chambers, headboxes). While very precise, these techniques are limited to research settings as they are expensive, labor-intensive, and applicable only to a few animals. Head-stalls, such as the GreenFeed system, have been used to measure expired CH4 for individual animals housed alone or in groups in confinement or grazing. This technique requires frequent animal visitation over the diurnal measurement period and an adequate number of collection days. The tracer gas technique can be used to measure CH4 from individual animals housed outdoors, as there is a need to ensure low background concentrations. Micrometeorological techniques (e.g., open-path lasers) can measure CH4 emissions over larger areas and many animals, but limitations exist, including the need to measure over more extended periods. Measurement of CH4 emissions from manure depends on the type of storage, animal housing, CH4 concentration inside and outside the boundaries of the area of interest, and ventilation rate, which is likely the variable that contributes the greatest to measurement uncertainty. For large-scale areas, aircraft, drones, and satellites have been used in association with the tracer flux method, inverse modeling, imagery, and LiDAR (Light Detection and Ranging), but research is lagging in validating these methods. Bottom-up approaches to estimating CH4 emissions rely on empirical or mechanistic modeling to quantify the contribution of individual sources (enteric and manure). In contrast, top-down approaches estimate the amount of CH4 in the atmosphere using spatial and temporal models to account for transportation from an emitter to an observation point. While these two estimation approaches rarely agree, they help identify knowledge gaps and research requirements in practice.

There is a need to accurately and precisely quantify greenhouse gas (GHG) emissions, specifically methane (CH4), to ensure correct reporting of GHG inventories and, perhaps more importantly, determine how to best mitigate CH4 emissions. The objective of this study was to review existing methods and methodologies to quantify and estimate CH4 emissions from ruminants. Historically, most techniques were developed for specific purposes that may limit their widespread use on commercial farms and for inventory purposes and typically required frequent calibration and equipment maintenance. Whole animal and head respiration chambers, spot sampling techniques, and tracer gas methods can be used to measure enteric CH4 from individual animals, but each technique has its own inherent limitations. The measurement of CH4 emissions from manure depends on the type of storage, animal housing, CH4 concentration inside and outside the boundaries of the area of interest, and ventilation rate, which is likely the most complex variable creating many uncertainties. For large-scale areas, aircraft, drones, and satellites have been used in association with the tracer flux method, inverse modeling, imagery, and LiDAR (Light Detection and Ranging), but research is lagging in validating these methods. Bottom-up approaches to estimating CH4 emissions rely on empirical or mechanistic modeling to quantify the contribution of individual sources. Top-down approaches estimate the amount of CH4 in the atmosphere using spatial and temporal models to account for transportation from an emitter to an observation point.

How Divergence for Feed Efficiency Traits Affects Body Measurements and Metabolites in Blood and Ruminal Parameters on Pre-Weaning Dairy Heifers.

The objectives of this study were: (1) to evaluate feed efficiency indexes and their relationships with body measurements and blood and ruminal metabolites in the pre-weaning period; (2) to determine if such measurements can be used as feed-efficiency markers during the pre-weaning period. Holstein-Gyr heifer calves (n = 36), enrolled between 4 and 12 weeks of age, were classified into two residual feed intake (RFI) and residual body weight gain (RG) groups: high efficiency (HE; RFI, n = 10; and RG, n = 9), and low efficiency (LE; RFI, n = 10; and RG, n = 8). Calves were fed whole milk (6 L/day) and solid feed ad libitum. Body developments were measured weekly and feed intake (milk and solid feed) daily during the whole period. Blood samples were collected at 12 weeks of age and analyzed for glucose, insulin and ß-hydroxybutyrate (BHB). Samples of ruminal content were collected on the same day and analyzed for pH, NH3-N, and volatile fatty acids (VFA). Among the growth characteristics, only the initial hip width differed between the RFI groups, and withers height differed between the RG groups. Concentration of BHB was greater and glucose: insulin ratios tended to be greater in LE-RG animals. Butyric acid proportions were similar among RFI groups, but tended to be greater for HE-RG than for LE-RG. Overall, correlation coefficients between RFI or RG and blood, rumen, or morphometric markers were low. Thus, it is unlikely that measurements of metabolic indicators, per se, will be useful in the early identification of more efficient animals. Understanding the underlying physiological basis for improved feed efficiency in dairy heifers requires further investigation.

Effects of Bulk Tank Milk, Waste Milk, and Pasteurized Waste Milk on the Intake, Ruminal Parameters, Blood Parameters, Health, and Performance of Dairy Calves.

The aim of this study was to evaluate the effects of bulk tank milk (BTM), WM, and PWM on the intake, ruminal parameters, blood parameters, health, and performance of dairy calves. Forty-five male crossbred dairy calves (Gyr × Holstein) were used. On their fourth day of age, animals were grouped according to body weight, serum protein levels, and genetic composition. Three treatments were assessed: BTM (n = 15), WM from cows in antibiotic treatment (n = 15), and PWM via high-temperature, short-time pasteurization (72-74 °C for 16 s) (n = 15). During the experimental period (from 4 to 60 d of age), animals were fed 6 L of milk/d, divided into two equal meals. Water and concentrate were provided ad libitum. Daily measurements were made for milk, concentrate, and water intakes, as well as for fecal and respiratory scores. Rumen fluid and blood were sampled weekly. The following parameters were evaluated: volatile fatty acids (VFAs), pH and ammonia-N in rumen fluid, and ß-hydroxybutyrate (BHB) and glucose in blood. Animals were weighed at birth, 4 d of age, and weekly up to 60 d of age. At the end of the experimental period (60 ± 1 d), all animals were euthanized for pulmonary evaluation. The randomized complete design with an interaction between treatment and week was the experimental method of choice for testing the hypothesis of the treatment's effect on all evaluated outcomes. Animals in the BTM treatment had higher milk dry matter intake (DMI), followed by WM and PWM calves. Concentrate DMI was lower for BTM in comparison to WM and PWM calves. However, total DMI showed no significant differences between treatments. The rumen fluid from calves receiving PWM had higher concentrations of acetate and propionate than that of BTM and WM animals. No differences were observed between treatments for blood glucose and BHB concentrations. Health parameters (fecal and respiratory scores) and pneumonia occurrence showed no significant difference between treatments. No differences were observed for average daily gain (ADG) or body growth. Feeding WM and PWM did not show significant negative effects on the intake, ruminal parameters, blood parameters, health, or performance of dairy calves.

Effect of pelleted vs. ground starter with or without hay on preweaned dairy calves.

The objective of this study was to evaluate the effect of the physical form of starter and inclusion of hay in the diet of preweaning dairy calves on performance, digestibility, ruminal development, and mRNA expression of genes involved in ruminal metabolism. Holstein × Gyr crossbred male calves (n = 38 1day old) were assigned to 3 treatments for 9 weeks: Control (n = 13; pellet starter with 4 mm diameter and 18 mm length and 4% steam-flaked corn), Ground (n = 12; same starter of the control but ground pass through a 4.0 mm sieve), or Ground plus 5% chopped Tifton hay GH (n = 13). All calves were fed 4 L/d of whole milk up to 63 d of age and were abruptly weaned at 64 d of age. Water and diets were offered ad libitum. Samples of ruminal contents were obtained from all animals at 30, 45, and 60 d of age to evaluate pH, ammonia nitrogen, and volatile fatty acids (VFA). At 55 d of age, an apparent digestibility assay was performed using 18 animals (n = 6/ treatment). At 65 d of age, the 18 animals were euthanized to evaluate the development of the digestive tract. The physical form of starter and the dietary inclusion of hay did not influence starter intake (Control 326 g/d, Ground 314 g/d and GH 365 g/d), daily weight gain (Control 541g/d, Ground 531g/d and GH 606g/d), feed efficiency, apparent nutrient digestibility, energy partitioning, nitrogen balance, ruminal pH, ammonia nitrogen concentration, VFA, the development of the digestive tract and the mRNA expression of genes involved in AGV metabolism.

Generation of models from existing models composition: An application to agrarian sciences.

Mathematical models that describe gas production are widely used to estimate the rumen degradation digestibility and kinetics. The present study presents a method to generate models by combining existing models and to propose the von Bertalanffy-Gompertz two-compartment model based on this method. The proposed model was compared with the logistic two-compartment one to indicate which best describes the kinetic curve of gas production through the semi-automated in vitro technique from different pinto peanut cultivars. The data came from an experiment grown and harvested at the Far South Animal Sciences station (Essul) in Itabela, BA, Brazil and gas production was read at 2, 4, 6, 8, 10, 12, 14, 17, 20, 24, 28, 32, 48, 72, and 96 h after the start of the in vitro fermentation process. The parameters were estimated by the least squares method using the iterative Gauss-Newton process in the software R version 3.4.1. The best model to describe gas accumulation was based on the adjusted coefficient of determination, residual mean squares, mean absolute deviation, Akaike information criterion, and Bayesian information criterion. The von Bertalanffy-Gompertz two-compartment model had the best fit to describe the cumulative gas production over time according to the methodology and conditions of the present study.

Replacement of Soybean Meal With Soybean Cake Reduces Methane Emissions in Dairy Cows and an Assessment of a Face-Mask Technique for Methane Measurement.

The objective of this study was to (a) evaluate the effect of replacing soybean meal (SBM) with soybean cake (SBC) on feeding behavior, rumen fermentation, milk production, nutrient digestibility and CH4 emissions and (b) investigate whether a face-mask technique could be used to predict daily methane (CH4) emissions in dairy cattle. The experiment was conducted as a completely randomized design, with 32 crossbred Holstein × Gyr cows (days in milk (DIM): 112 ± 25.1) randomly assigned to the following treatments (n = 8/group) for 75 days: (1) 0% SBC, (2) 6% SBC, (3) 14% SBC, and (4) 23% SBC, in place of SBM on a dry matter (DM) basis. Across the final 4 weeks of the study, CH4 production was estimated using the proposed face-mask technique subsequent to a respiration chamber measurement for an evaluation of treatment efficacy and face-mask accuracy. There was no effect of SBM replacement by SBC on intake, feeding or drinking behavior (P > 0.21). Total VFA concentration, the individual proportions of VFA and blood metabolites were not altered (P > 0.17) by SBC, however there was a tendency for decreased (P = 0.08) lactate and plasma urea nitrogen (P = 0.07) concentration associated with SBC addition. Fat-corrected milk yield (FCM4%) and composition was not affected (P > 0.27) by SBC; however, there was a tendency for decreased total milk solids (P = 0.07) and milk fat (P = 0.08) associated with 23% SBC treatment. There was no treatment × technique interaction (P > 0.05) effect on gas measurements. A maximum reduction (P = 0.01) in CH4 yield (g/kg DM) and intensity (g/kg milk) of 11 and 20%, respectively, was observed for the 14% SBC inclusion. Compared to the week of mask measurements, chambers decreased (P = 0.01) intake (kg/d, %BW) and increased (P = 0.05) FCM4%. The face-mask method over estimated O2 consumption by 5%. The face-mask method accurately predicted daily CH4 emissions when compared to the chamber at the same time-point. However, there was a linear bias of CH4 outputs so further evaluation of the calculation of total CH4 from a spot measurement is required.