Individual Animal Performance Research Articles

Effects of condensed tannin-enriched alternative energy feedstuff supplementation on performance, nitrogen utilization, and rumen microbial diversity in grazing beef cattle

This study aims to investigate the effects of alternative energy feedstuff supplementation containing condensed tannin (CT) on palisade grass pastures, focusing on intake, nutrient digestibility, animal performance, ruminal and blood parameters, nitrogen use efficiency (NUE), and its impacts on the ruminal bacterial community in backgrounding Nellore young bulls. Two experiments were conducted simultaneously. Animal performance was evaluated in Experiment 1. The experimental design was a completely randomized block; ninety Nellore bulls (Bos taurus indicus) with an average initial body weight (BW) of approximately 240 ± 5 kg were used (64 as testers and 26 as regulators). The feed intake, digestibility of dry matter and nutrients, ruminal parameters, NUE, and the impact on the ruminal bacterial community were evaluated in Experiment 2. The experimental design was a 4 × 4 double Latin square involving eight Nellore bulls with an average initial BW of 290 ± 8 kg, all of which were cannulated in the rumen. The treatments consisted of energy supplementation at 0.3 % of BW with peanut skin (PS), 0.3 % of BW with sorghum grain (SG), 0.3 % of BW with soybean hulls (SHs), and a control treatment with a supply of mineral salt ad libitum. The total digestible nutrient intake was lower in animals that received only mineral supplements (p < 0.005). The dry matter (DM) intake decreased with treatment PS, while the DM and nutrient digestibility increased (p < 0.005). There was a reduction in ruminal ammonia nitrogen and an improvement in NUE in the PS treatment (p < 0.005). However, the bacterial and Archaea populations were unaffected (p = 0.619). Individual animal performance and gain per kg were increased in the treatment with supplements containing or without CT compared to the mineral supplement (p < 0.001). The NUE improved in treatments PS, SG, and SH (p < 0.01). Feedstuff supplementation using no edible foods by products containing CTs is an effective alternative energy source for Nellore bulls grazing on palisade grass during the rainy season. Additionally, it can be used to mitigate the environmental impacts of N excretion.

4 Utilizing SmartFeed Pro and SuperSmart Feeders for applied beef cattle research

Abstract Designing research for applied beef cattle production systems has always presented challenges for Land Grant University and USDA Scientist. Specifically, creating study designs that have enough replication for statistical inference has often prompted scientists to use designs that do not closely replicate actual production systems. Past research has often used multiple replications (pens/paddocks/pastures) that utilize replication (group averages; 4 – 8 animals) means as the experimental unit. While effective in measuring average treatment responses, these types of study designs do little to describe the actual individual animal behavior and performance in a more practical production environments. Approaches to increasing statistical observations in actual production environments will be discussed in this presentation. Embracing new technologies such as GPS, activity monitors, EID tags, and feed intake monitors (C-Lock Inc, GrowSafe) combined with multiple regression modeling tools can aid in designing and publishing beef cattle production research in actual beef production environments. Research at Montana State University has utilized SmartFeed Pro and SuperSmart Feeders for strategic supplementation research on extensive rangelands and dry-land pastures for the past seven years. Results of these studies have evaluated self-fed (salt-limited; loose, pelleted, and baked molasses blocks) as well as hand-fed supplements where daily intakes are limited by the locking gate on the feeder. This presentation will summarize these studies with a focus on research designs that were successful and/or unsuccessful in respect to characterizing beef cattle performance in production settings. Our goal will be to assist the audience in the application of feed intake technology in designing future applied beef cattle research.

301 Determining Individual Dry Matter Intake of Charolais Bulls from Ingestion Time Recorded with Rgb-D Cameras

Abstract Monitoring individual dry matter intake (DMI) may help decision-making of cattle producers to improve feed efficiency, health and welfare; however, classic methods to record DMI are expensive and time-consuming (Davison et al., 2021). Thus, since the last years new technologies, such as cameras and Deep Learning (DL) algorithms have been developed to capture individual animal performance in an easier and cheaper way. The aim of this work is to evaluate the capability of an RGB-D camera coupled to a DL algorithm to predict individual DMI of beef cattle. For this, 12 young Charolais bulls (581 ± 37) were recorded during 10 days after meal distribution though an Intel Realsense (TMD455) camera (12 mins per video at 5 frames per second) and their DMI was individually measured. The DL algorithm for video processing was the YOLO (V8). We first trained the model to characterize activity of the animals (biting, chewing, visiting, ruminating and others; Table 1) through manual labelling using 650 images randomly extracted form videos. The images were divided into three sets for training, validation, and testing, (60, 20, and 20%, respectively) and metrics used to evaluate the model were Precision (P), Recall (R) and the average precision (AP). Then, we estimated the ingestion time (IT) by summing predicted biting and chewing time. This predicted IT was compared with the real IT measured through a chronometer. Finally, a mixed effects model was used to predict individual DMI from IT. Results showed an average high precision for all activities predicted (P = 0.62, R = 0.83, AP = 0.81). In addition, activities encompassed on the IT also showed a high precision (AP &amp;gt; 0.84). However, the confusion matrix showed a slight confusion between chewing and visiting (r = 0.14) activities. After processing activity of the animal, we observed a high correlation (r = 0.82, P = 0.001) between predicted and measured IT. Finally, we obtained a significant relationship between DMI and predicted IT (R² = 0.45, P = 0.001, RMSE = ±0.18kg DMI). The present work shows how new technologies such as RGB-D cameras associated to a trained DL algorithm could facilitate data acquisition on cattle farms, which may help decision-making of producers in terms of efficiency, health and welfare of the animal.

Field demonstration analyzing the implementation of individual animal electronic identification and genetic testing in western range sheep flocks.

Adoption of electronic identification ear tags (EID) and DNA testing by commercial range sheep producers in the Western United States has been low, despite the availability of these technologies for over a decade. Jointly, these technologies offer an approach to provide individual animal performance data to improve flock health, genetic and reproductive management. This project involved a collaboration with five California sheep producers representing a broad geographic range, varying levels of pre-project EID adoption, and diverse operational practices. Tissue samples were collected from, and ear EIDs were placed in, a total of 2,936 rams and their potential lambs. We partnered with a commercial packing company, Superior Farms, to genotype the animals. Superior Farms used a targeted genotyping panel to assign parentage, and link individual animal identification (ID) to camera-graded carcass measurements. This enabled the collection of individual progeny carcass data and provided insight into sire performance, providing for the within-flock identification of prolific sires that were producing lambs with significantly more saleable meat as compared to their flock mates. Overall, almost 91% of lambs were successfully matched to their sire, and prolificacy ranging from 0-135 lambs per ram. There was as much as an $80 difference in the average edible product from camera-graded carcasses derived from lamb groups sired by different rams. A partial budget analysis modeling investment in an EID system coupled with an autodrafter and scale to collect individual weights and improve labor efficiency during processing, and a sheep flip chute to improve worker safety during foot trimmings, yielded a greater than 7:1 return on investment over a five-year time frame. Ideally, the data collection enabled by EIDs and DNA testing would feed into data-driven genetic evaluation programs to enable selection for more productive and profitable animals, and allow the US sheep industry to accelerate the rate of genetic improvement.

109 Invited Talk: Grazing Management and Stocking Strategy Decisions for Pasture-Beef Systems: Experimental Confirmation vs Testimonials and Perceptions

Abstract The primary objectives of forage-based livestock grazing systems are to enhance sustainability of pastures and cattle production, and to maintain economic stability in the presence of changes in input costs and returns. Grazing management strategies and implementation vary for adapted forages according to vegetational-hardiness zones, livestock production objectives, and manager preferences for grazing systems, stocking rates, and stocking methods. Stocking methods are strategies or techniques to manipulate grazing animals in space and time and may be considered as variations of continuous or rotational stocking. In many stocking method discussions, the debates are often focused on experimental confirmational data vs testimonials and perceptions. Acceptable methodology and statistical analyses of grazing experimentation on continuous vs rotational stocking provides repeated measures of forage nutritive value, forage mass, grazing intensity, and stocking rate on gain per animal, gain per unit land area. Additional measurements may include effects on forage stand maintenance and soil nutrient analyses-status. Recent adaptations of mob stocking and intensive rotational grazing via popular press and consultants have received acclaims for methods to enhance ecosystem services, soil health, and other non-experimentally documented attributes. Managers may adopt these testimonials of stocking methods of 60 days or more deferment based on their perception of protecting and enhancing the environment rather than logic of seeking experimental evidence. However, when given a choice of forage available for consumption, cattle select more than 80% of their diet as leaves. Thus, with respect to average daily gain per animal (ADG), only a small percentage of pasture studies have shown an advantage for rotational stocking. The lack of ADG was attributed to reduced nutritive value of forage available for selection during the residence time. Selecting management and stocking strategies for optimum utilization for forage produced, individual animal performance, and overall gain per unit land area has led to flexible grazing systems. These grazing systems may not be “hardcore rotationally, time-scheduled stocked,” but they do involve multiple pastures with strategies to incorporate movement of cattle based on current paddock forage status and forage mass estimates for desired animal performance. Grazing management strategies control the degree of intensity of beef cattle production based on level of economic risk and desired-expected environmental stewardship goals. Of all the strategies that management may adopt for grazing, the primary factor that controls resultant sustainability of pastures is that of grazing intensity as measured by stocking rate or forage height-density. Implementing revised or new management strategies requires attention to detail and the use of data-results-recommendations from comparative experiments conducted by a recognized source without conflict of interest in the method promoted.

114 Evaluation of Assertions from Educational, Outreach and Engagement Programs in Pasture-Based Livestock Systems

Abstract Assertions about grazing management and grazing systems should be evaluated based on the scientific literature. Prior assumptions can limit our ability to achieve constructive dialogue regarding the merits of various stocking methods. These include the assumption that rotational stocking is inherently superior to continuous stocking, regardless of the nature of the overall grazing system, and the presumption that continuous stocking implies overgrazing. We revisited assertions about grazing management in general, but more specifically the choice of the stocking method, and considered their merit in the context of evidence from the literature, including a chapter titled Prescribed Grazing on Pasturelands from a National Resource Conservation Service (NRCS) literature synthesis published in 2012. We framed those assertions in the form of questions. The questions were: a) Does choice of rotational stocking ensure well-managed pastures?, b) Does rotational stocking result in greater accumulation of soil carbon than continuous stocking?, c) Does rotational stocking increase pasture productivity and optimal stocking rate compared with continuous stocking?, d) Does forage nutritive value and individual animal performance increase in rotational versus continuous stocking?, and e) Do pastures “look better” in rotational versus continuous stocking?. The objectives were to consider whether these often-stated assertions about grazing management were supported, refuted, or simply not adequately assessed by the body of scientific evidence. It is important to recognize that choice of stocking method is only one element of grazing management and grazing management is only one element of a grazing system. Thus, stocking method is “one piece of a very large pie”. Additionally, stocking rate (grazing intensity) is a separate and independent grazing management choice from stocking method, such that both rotationally and continuously stocked pastures can be understocked, overstocked, or optimally stocked. It is unfortunate that choice of stocking method dominates discussions of improving grazing management to the expense of other issues, when in fact intensity of grazing has been shown conclusively to be the most important determinant of a wide array of soil, plant, animal, and ecosystem responses. We have observed that terminology such us regenerative grazing, holistic planned grazing, adaptative multipaddock grazing, management intensive grazing, high intensity low frequency grazing, and others, arise frequently and can dominate discussions in the realm of education, outreach and engagement programs in pasture-based livestock systems. These words/themes lack clear definition, and this lack of specificity may promote misconceptions, thus hindering the opportunity for critical thinking and ultimately the advancement and improvement of grazing systems. Educational efforts in pasture management should strive to remain relevant by focusing on experimental evidence. Local (i.e., state or county level) outreach and engagement programs are challenged with providing timely and specific information with implementable guidelines based on frequent observations at the landscape and farm levels.

The defoliation dynamics of a stockpiled native grassland pasture follow similar patterns between supplemented and unsupplemented beef calves

AbstractIt is unclear to what extent and on which variables does supplementing beef cattle on native grasslands affect sward structure, specifically on the dynamics of its grazing horizons. Three hypotheses were tested: (i) during a grazing down process under similar forage allowance, supplemented animals take longer to finish each grazing stratum, than their unsupplemented counterparts, (ii) in both cases, the upper stratum will be heavily depleted before the subsequent strata are grazed, (iii) some species and/or forage fractions are consumed faster than others, regardless of the animals being supplemented (corn dried distillers grains with solubles, DDGS, at 0.7% of their body weight, BW, on a dry matter, DM, basis) or not. Three blocks of stockpiled native grasslands were used and split into two treatments plots (n = 6), on which either supplemented (S) or control (C) heifers of 10.6 ± 0.6 months of age and an initial BW of 143 ± 9 kg, were used. A 2.5 × 0.5 m observation grid was installed on the sward, generating 384 observation points on each plot. On these observation plots, sward height (SH) and visually assessed green forage mass percentage (%G) were registered every other day for 12 consecutive days. No differences were found between the horizontal grazing dynamics between supplemented and control animals in terms of how they switched from the upper grazing horizon to the successive ones. In both cases, when the upper grazing horizon was heavily depleted, the subsequent horizon was being depleted by its half. Differences of preference for C3 species over C4 was observed for both treatments, but this effect was more meaningful for control animals. Grazing time never fully compensated for the decline in intake rate during depletion throughout the grazing horizons. Pasture intake declined when the animals transition from grazing the top grazing horizons to the lower horizons, irrespective of the level of supplementation. Managing the sward structure in terms of sward height will be beneficial to maximizing individual animal performance, for both C and S animals. Native grasslands paddocks with a greater C3 gasses predominance will always be preferred to C4 dominated paddocks, regardless of an eventual supplementation practice.

An evaluation of detailed animal characteristics influencing the lactation production efficiency of spring-calving, pasture-based dairy cattle

Selection for feed efficiency, the ratio of output (e.g., milk yield) to feed intake, has traditionally been limited on commercial dairy farms by the necessity for detailed individual animal intake and performance data within large animal populations. The objective of the experiment was to evaluate the effects of individual animal characteristics (animal breed, genetic potential, milk production, body weight (BW), daily total dry matter intake (TDMI), and energy balance) on a cost-effective production efficiency parameter calculated as the annual fat and protein (milk solids) production per unit of mid-lactation BW (MSperBWlact). A total of 1,788 individual animal intake records measured at various stages of lactation (early, mid, and late lactation) from 207 Holstein-Friesian and 200 Jersey × Holstein-Friesian cows were used. The derived efficiency traits included daily kilograms of milk solids produced per 100 kg of BW (dMSperBWint) and daily kilograms of milk solids produced per kilogram of TDMI (dMSperTDMI). The TDMI per 100 kg of BW was also calculated (TDMI/BWint) at each stage of lactation. Animals were subsequently either ranked as the top 25% (Heff) or bottom 25% (Leff) based on their lactation production efficiency (MSperBWlact). Dairy cow breed significantly affected animal characteristics over the entire lactation and during specific periods of intake measurements. Jersey crossbred animals produced more milk, based on a lower TDMI, and achieved an increased intake per kilogram of BW. Similarly, Heff produced more milk over longer lactations, weighed less, were older, and achieved a higher TDMI compared with the Leff animals. Both Jersey × Holstein-Friesian and Heff cows achieved superior production efficiency due to lower maintenance energy requirements, and consequentially increased milk solids production per kilogram of BW and per kilogram of TDMI at all stages of lactation. Indeed, within breed, Heff animals weighed 20 kg less and produced 15% more milk solids over the total lactation than Leff. In addition, Heff achieved increased daily milk solids yield (+0.16 kg) and milk solids yield per kilogram of TDMI (+ 0.23 kg/kg DM) during intake measurement periods. Moreover, the strong and consistently positive correlations between MSperBWlact and detailed production efficiency traits (dMSperBWint, dMSperTDMI) reported here demonstrate that MSperBWlact is a robust measure that can be applied within commercial grazing dairy systems to increase the selection intensity for highly efficient animals.

359 Using an Extruded 100% Dried Distillers' Grains Cube to Intensify Production in a Stocker Grazing Enterprise on Native Range in Northwestern Oklahoma

Abstract A 2-year experiment was conducted at the USDA-ARS Southern Plains Experimental Range (SPER) near Fort Supply, OK to define the effects of supplementing steers grazing native range with extruded 100% dried distillers' grains (DDGS) cubes. Each year 126 steers (259 ± 43 kg) grazed from late May to late September allocated to 3 treatments: 1) negative control (NC) stocked at 2.4 ha/steer with ad libitum mineral only, 2) positive control (PC), supplemented with 1.8 kg/steer on alternate days during the late summer stocked at 2.4 ha/steer, and 3) high supplement (HS) fed 0.75% BW supplemental DDGS cubes all season stocked at 1.6 ha/steer. Data were analyzed across years using PROC MIXED in SAS as a complete block design using year as the random block and pasture within treatment by year as the error term. Early season ADG and BW gains for HS were 0.30 ± 0.031 kg and 20 ± 2.1 kg greater (P &amp;lt; 0.01) than NC and PC, respectively. However, late season ADG for HS and PC steers were 0.34 ± 0.08 and 0.36 ± 0.08 kg greater (P &amp;lt; 0.01) than NC. Late season BW gains for HS and PC did not differ (P ≥ 0.76) but were 22.3 ± 5.3 and 23.9 ± 5.4 kg greater than NC, respectively. Hence, overall ADG, total BW gain, and BW gain/ha for HS were 0.32 ± 0.04, 0.14 ± 0.04; 42 ± 5.4, 18 ± 5.4; and 53 ± 2.2, 42 ± 2.2 kg greater (P &amp;lt; 0.01) than NC and PC, respectively. Supplementing 100% DDGS cubes during summer grazing is an effective management option to increase stocking rates without negatively impacting individual animal performance, and increasing gain/hectare.

Intensification strategies for temperate hot-summer grazing dairy systems in South America: Effects of feeding strategy and cow genotype

Pasture-based dairy systems present the opportunity to increase productivity per hectare through increasing stocking rate and forage utilization. However, in the temperate hot-summer region of South America, different productive strategies are being adopted by farmers. The aim of this study was to quantify the effect of feeding strategy (FS) and cow genotype (G) on individual animal and whole-farm biophysical performance. A design with 2 × 2 levels of intensification aiming to increase home-grown forage utilization and milk output per hectare was evaluated. The experiment was a randomized complete block design with a 2 × 2 factorial arrangement of treatments, combining 2 feeding strategies with varying proportions of grazing in the annual feeding budget [grass fixed (GFix) and grass maximum (GMax)] and 2 Holstein Friesian cow genotypes [New Zealand (NZHF) or North American Holstein Friesian (NAHF)]. The effects of FS, G, and their interaction were analyzed using mixed models. New Zealand Holstein Friesian cows presented lower individual milk yield and higher milk component concentrations, maintained higher average body condition score, and increased body weight (BW) throughout the experiment, while presenting a better reproductive performance compared with the NAHF cows. Although all farmlets were planned at the same stocking rate on a per kilogram of BW basis, the current stocking rate changed as a result of animal performance and grass utilization resulting in NZHF cows achieving greater BW per hectare. The superior stocking rate led to greater milk solids production and feed consumption per hectare for the systems with NZHF cows. The GFix feeding strategy resulted in greater total home-grown forage harvest and conserved forage surplus than GMax. Overall, it was feasible to increase stocking rate and increase milk production per hectare from home-grown forage with differing feeding strategies and Holstein Friesian cow genotypes within grazing systems located in the temperate hot-summer climate region of South America. The interactions reported between FS × G highlight the superior productivity per hectare of NZHF cows within the GMax feeding strategy based on maximizing grazed pasture, which could represent a competitive intensification strategy in terms of cost of production for this region.

Short Communication: Performance of steers fed on pasture receiving different seeding rates of vetch in an integrated crop-livestock system

Aim of study: To evaluate the performance of beef calves fed black oat and Italian ryegrass pasture seeded with several different seeding rates (SR) of common vetch in a crop-livestock integrated system.Area of study: The experiment was carried out in Dois Vizinhos city, Paraná, Brazil.Material and methods: An area of 8.3 ha was used, which was divided into 11 paddocks, 0.75 ha each. Nellore calves (n = 22), 7 ± 2 months old and with initial body weight of 134 ± 27 kg were used for the tests. The experimental design was completely randomised. Vetch (Vicia sativa L., ‘Amethyst’) SR treatments included 0, 15, 30, and 45 kg ha-1, in a mixture with black oat (Avena strigosa Schreb. ‘IPR 61’ and Italian ryegrass (Lolium multiflorum Lam.) pastures.Main results: There was no effect of SR on pasture productivity parameters. The increase in vetch seed in the seed mixture resulted in an increase in crude protein and neutral detergent fibre, but decreased in vitro digestibility of vetch. However, these changes did not affect the nutritional value of the pasture. Vetch SR of 30 kg ha-1 or higher allowed greater share of the legume in the pasture, thereby enhancing greater individual animal performanceResearch highlights: Vetch SR of 30 kg ha-1 or higher allowed greater share of the legume in the pasture, thereby enhancing greater individual animal performance.

Invited review: The future of selection decisions and breeding programs: What are we breeding for, and who decides?

Genetic selection has been a very successful tool for the long-term improvement of livestock populations, and the rapid adoption of genomic selection over the last decade has doubled the rate of gain in some populations. Breeding programs seek to identify genetically superior parents of the next generation, typically as a function of an index that combines information about many economically important traits into a single number. In the United States, the data that drive this system are collected through the national dairy herd improvement program that began more than a century ago. The resulting information about animal performance, pedigree, and genotype is used to compute genomic evaluations for comparing and ranking animals for selection. However, the full expression of genetic potential requires that animals are placed in environments that can support such performance. The Agricultural Research Service of the US Department of Agriculture and the Council on Dairy Cattle Breeding collaborate to deliver state-of-the-art genomic evaluations to the dairy industry. Today, most breeding stock are selected and marketed using the net merit dollars (NM$) selection index, which evolved from 2 traits in 1926 (milk and fat yield) to a combination of 36 individual traits following the last NM$ update in 2018. Updates to NM$ require the estimation of many different values, and it can be difficult to achieve consensus from stakeholders on what should be added to, or removed from, the index at each review, and how those traits should be weighted. Over time, the majority of the emphasis in the index has shifted from yield traits to fertility, health, and fitness traits. Phenotypes for some of these new traits are difficult or expensive to measure, or require changes to on-farm habits that have not been widely adopted. This is driving interest in sensor-based systems that provide continuous measurements of the farm environment, individual animal performance, and detailed milk composition. There is also a need to capture more detailed data about the environment in which animals perform, including information about feeding, housing, milking systems, and infectious and parasitic load. However, many challenges accompany these new technologies, including a lack of standardization or validation, need for high-speed internet connections, increased computational requirements, and interpretations that are often not backed by direct observations of biological phenomena. This work will describe how US selection objectives are developed, as well as discuss opportunities and challenges associated with new technologies for measuring and recording animal performance.

Spinescence and Total Phenolic Content Do Not Influence Diet Preference of a Critically Endangered Megaherbivore, but the Mix of Compounds Does.

In contrast to understanding spinescence in savanna woody species, little is known about the functions of plant secondary metabolites (PSM). Negative effects of PSMs on individual animal performance potentially translate into negative effects on herbivore population growth. Hence, understanding PSM functions is important for the conservation of savanna megafauna. We tested the view that black rhinoceros (Diceros bicornis) diet preference is not affected by spinescence or total phenolic abundance. We hypothesized that the composition of phenolic mixtures, however, would affect preference. Furthermore, we tested our data from 71 woody species for a trade-off between structural and chemical defenses. Spinescence type, and spinescence generally, did not deter black rhino feeding. Using eco-metabolomic data, we found that total abundance of phenolics did not affect preference, but mixture composition did and that the probability of spinescence trading off against phenolics depended on the mixture. We note that our study was restricted to black rhino and that diet preferences of other mammal herbivores might be influenced by subtle differences in phenolic mixtures. However, our results did support a previous, more detailed study of phenolic profiles of six species showing the same patterns in relation to preference generalised across mammal herbivore species in savannas. Our results represent substantial advancement in the understanding of the roles of PSMs, especially flavonoid compounds, in the functioning of savanna ecosystems, and highlight the need to dig deeper into broad groups of traits such as spinescence or total phenolics to improve understanding of woody plant defenses in savannas.

Effects of supplementation with corn distillers’ dried grains on animal performance, nitrogen balance, and enteric CH4 emissions of young Nellore bulls fed a high-tropical forage diet

The inclusion of corn-dried distillers’ grains (DDG) could be an alternative supplement to increase animal performance, nitrogen efficiency usage (NEU), and decrease enteric methane (CH4) emissions. Our goal was to determine whether DDG could replace a traditional supplement (cottonseed meal) without affecting animal performance, N balance, and CH4 emissions. The experiment was conducted during the forage growing season (December to April), with 15 d adaptation, and a 112 d experimental period. The experimental design was completely randomized with four treatments: a mineral supplement (MS), cottonseed meal supplement (CS), 50% replacement of CS by DDG (50DDG), and 100% replacement of CS by DDG (100DDG). Cottonseed meal and DDG were used as protein supplement. A total of 12 paddocks, 3 per treatment, were used to measure forage mass: morphological and chemical composition of forage, forage allowance, and animal performance. Six animals per treatment were used to evaluate DM intake, digestibility, CH4 emissions, microbial protein production (MCP), and NEU of each treatment. Eighty-one Young Nellore bulls (48 testers, 12 per treatments and 33 adjusters) with initial BW of 255 ± 5 kg (10–12 months old) were supplemented with each supplement type at a level of 0.3% of BW. Pasture management was continuous stocking with a variable stocking rate (put-and-take). Enteric CH4 was measured using the gas tracer technique. The MCP was quantified using purine derivatives and the NEU mass balance. No differences were found in nutrient intake (P > 0.228). Individual animal performance and gain per area were higher in the treatments with concentrates compared with that of MS; however, there was no difference among treatments CS, 50DDG, and 100DDG. The ADG was 0.83 for MS and 1.08 kg/animal/d when supplemented (P < 0.05). Gain per hectare was 709 kg/ha for MS and 915 kg/ha when supplemented with concentrates (P < 0.05). There was no difference in CH4 production among treatments that average 180 g/animal/d; however, CH4 per kg of gain was reduced with CS. The CH4 conversion factor averaged 5.91%. There was no difference in the synthesis of MCP and NEU. Corn DDG can replace 100% of cottonseed meal as a protein source for supplementation of young Nellore bulls grazing in tropical pastures without affecting animal performance, NEU, MCP, and CH4 emissions.

16 Opportunities and challenges from deep-phenotyping of dairy cattle

Abstract Genetic selection has been a very successful tool for the long-term improvement of livestock populations, and the rapid adoption of genomic selection over the last decade has doubled the rate of gain in some populations. However, the full expression of genetic potential requires that animals are placed in environments that support such performance. Increasingly complex dairy cattle production systems require that all aspects of animal performance are measured across individuals’ lifetimes. Selection emphasis is shifting away from traits related to animal productivity towards those related to efficient resource utilization and increased animal welfare. However, phenotypes for many of these new traits are difficult or expensive to measure, or both. This is driving interest in sensor-based systems that provide continuous measurements of the farm environment, individual animal performance, and detailed milk composition. The goal of phenomics is to provide information for making decisions related to on-farm management, as well as genetic improvement. However, many challenges accompany these new technologies, including a lack of standardization, the need for high-speed Internet connections, increased computational requirements, and training to integrate these tools with more traditional management tools. There also is a lack of translational research on the use of these data for real-time precision management. We will identify opportunities and challenges associated with phenomics and discuss on-farm applications of these new tools.

Feed and production efficiency of young crossbred beef cattle stratified on a terminal total merit index.

Few studies have attempted to quantify the association between a terminal total merit index with phenotypic feed and production efficiency in beef cattle, particularly when feed efficiency is itself explicitly absent as a goal trait in the index. The objective of the present study was to quantify the differences in phenotypic performance for feed intake, feed efficiency, and carcass traits of crossbred bulls, steers, and heifers differing in a terminal total merit index. A validation population of 614 bulls, steers, and heifers that were evaluated for feed intake and efficiency in the same feedlot and subsequently slaughtered at the end of their test period was constructed. The Irish national genetic evaluations for a terminal index of calving performance, docility, feed intake, and carcass traits were undertaken with the phenotypic records of animals present in the validation population masked. The validation population animals were subsequently stratified into four groups, within sex, according to their terminal index value. Mixed models were used to quantify the association between terminal genetic merit and phenotypic performance; whether the associations differed by sex were also investigated. The regression coefficient of phenotypic feed intake, carcass weight, carcass conformation, or carcass fat on its respective estimated breeding values was 0.86 kg dry matter 0.91 kg, 1.01 units, and 1.29 units, respectively, which are close to the expectation of one. On average, cattle in the very high terminal index stratum had a 0.63 kg DM/d lower feed intake, a 25.05 kg heavier carcass, a 1.82 unit better carcass conformation (scale 1 to 15), and a 1.24 unit less carcass fat score (scale 1 to 15), relative to cattle in the very low terminal index stratum. Cattle of superior total genetic merit were also more feed efficient (i.e., had a lower energy conversion ratio, lower residual feed intake, and greater residual gain), had a greater proportion of their live-weight as carcass weight (i.e., better dressing percentage) and were slaughtered at a younger age relative to their inferior total genetic merit counterparts. This study provides validation of an all-encompassing total merit index and demonstrates the benefits of selection on a total merit index for feed and production efficiency, which should impart confidence among stakeholders in the contribution of genetic selection to simultaneous improvements in individual animal performance and efficiency.

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 (R2 = 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.

Evaluating environmental impacts of selection for residual feed intake in pigs

To identify a proper strategy for future feed-efficient pig farming, it is required to evaluate the ongoing selection scenarios. Tools are lacking for the evaluation of pig selection scenarios in terms of environmental impacts to provide selection guidelines for a more sustainable pig production. Selection on residual feed intake (RFI) has been proposed to improve feed efficiency and potentially reduce the associated environmental impacts. The aim of this study was thus to develop a model to account for individual animal performance in life cycle assessment (LCA) methods to quantify the responses to selection. Experimental data were collected from the fifth generation of pig lines divergently selected for RFI (low line, more efficient pigs, LRFI; high line, less efficient pigs, HRFI). The average feed conversion ratio (FCR) and daily feed intake of LRFI pigs were 7% lower than the average of HRFI pigs (P < 0.0001). A parametric model was developed for LCA based on the dietary net energy fluxes in a pig system. A nutritional pig growth tool, InraPorc®, was included as a module in the model to embed flexibility for changes in feed composition, animal performance traits and housing conditions and to simulate individual pig performance. The comparative individual-based LCA showed that LRFI had an average of 7% lower environmental impacts per kilogram live pig at farm gate compared to HRFI (P < 0.0001) on climate change, acidification potential, freshwater eutrophication potential, land occupation and water depletion. High correlations between FCR and all environmental impact categories (>0.95) confirmed the importance of improvement in feed efficiency to reduce environmental impacts. Significant line differences in all impact categories and moderate correlations with impacts (>0.51) revealed that RFI is an effective measure to select for improved environmental impacts, despite lower correlations compared to FCR. Altogether more optimal criteria for efficient environment-friendly selection can then be expected through restructuring the selection indexes from an environmental point of view.

264 Using bermudagrass baleage to increase stocking rates of fall wheat pasture

Abstract The objectives of the current research were to determine the effect of offering ad libitum bermudagrass (Cynodon dactylon) round bale silage on performance and stocking rate of growing steers grazing wheat pasture in northern Arkansas. Eighteen, 1.6-hectare wheat fields were no-till planted to soft-red winter wheat in the first week of September (101 kg wheat seed/ha; cv. Jamestown) and were stocked to growing steers on October 23, 2018 at 2.5 steers/ha without bermudagrass baleage (CONTROL, n = 6) or with ad libitum bermudagrass baleage stocked at 2.5, 3.75, or 5.0 steers/ha (BALE2.5, BALE3.75, and BALE5.0, respectively; n = 4 pastures/treatment). The bermudagrass baleage was harvested in the late summer of 2018 and contained 40%DM, 14.3% CP, 70% NDF, 39% ADF, and 55% calculated TDN. Forage mass was 1,268 kg DM/ha (P ≥ 0.39) at the start of grazing and forage allowance (P &amp;lt; 0.01) was 2.25, 2.20, 1.62, and 1.27 kg forage DM/kg steer BW, respectively, at the start of grazing. Average daily gains of CONTROL (1.40 kg/d) did not differ (P = 0.36) from BALE2.5 (1.34 kg/d), but as stocking rate increased ADG decreased (P &amp;lt; 0.01) to 1.14 kg/d and 0.96 kg/d, for BALE3.75 and BALE5.0, respectively. As observed with ADG, gain per hectare and steer grazing-days per hectare did not differ (P ≥ 0.53) between CONTROL (340 kg/ha and 272 d/ha, respectively) and BALE2.5 (365 kg/ha and 272 d/ha, respectively), but each increased (P &amp;lt; 0.01) with increasing stocking rate, to 408 and 543 grazing d/ha for BALE3.75 and BALE5.0, respectively, and 467 and 524 kg BW gain/ha, respectively. The current research indicates that, even though individual animal performance decreases, stocking rates of wheat pasture for fall grazing stocker calves can be increased two-fold with up to 54% increase in BW gain/ha.

Mitigation of enteric methane emissions through pasture management in integrated crop-livestock systems: Trade-offs between animal performance and environmental impacts

We evaluated the effect of different grazing intensities by steers on animal performance, herbage intake and CH4 emissions in the stocking period of a soybean-beef cattle integrated system in southern Brazil. Treatments consisted of different grazing intensities, defined by target sward heights (10, 20, 30 and 40 cm) of mixed black-oat (Avena strigosa Schreb.) and Italian ryegrass (Lolium multiflorum Lam.) pastures under continuous stocking. Grazing management affected herbage utilization and, consequently, animal performance and CH4 emission. At the individual level, CH4 emission and animal performance had optimal values when pasture height was managed within a range of 23–30 cm. At the farm level, we found a positive linear effect of grazing intensity on animal live weight gain per hectare and the associated environmental costs of land use. Liveweight gain increased by 90 g ha−1 day−1 and CH4 emissions increased by 500 g CO2eq ha−1 day−1 for each cm of target sward height reduction. Given that most producers graze pastures to very short heights, large-scale adoption of target heights within 23–30 cm in southern Brazil has the potential to achieve 13–14% of the mitigation target for GHG emissions from the whole agricultural sector and 22–25% of the target for enteric fermentation from the livestock sector pledged by the Brazilian Government in the Paris Agreement. We conclude that adequate grazing management is the key strategy to improve animal production and reduce the environmental impact from livestock in ICLS.