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The objectives of this study were to examine the effects of gender and breed type on performance, feed efficiency, and feeding behavior traits in growing goats. The trial was conducted with 36 intact male (n = 16) and female (n = 20) goats of 4 breed types;12 purebred Spanish, 12 F1 Spanish x Boer (dam-sire), 8 F1 Boer x Spanish, and 4 purebred Boer. Goats with initial BW of 30.9 ± 6.0 kg and 38.8 ± 7.4 kg for females and males, respectively, were fed a concentrate diet in pens equipped with electronic feed bunks (GrowSafe System). Individual dry matter intake (DMI) and feeding behavior traits were collected daily for 44 d and BW measured weekly. Residual feed intake (RFI) was calculated as the residual from the regression of DMI on ADG and mid-test BW0.75. Feeding behavior traits evaluated were frequency and duration of bunk visit (BV) events, head-down (HD) duration, BV eating rate (BVER), and day-to-day variation of these traits, defined as the root mean squared error (RMSE) from linear regression of each trait on the day of trial. A mixed model (JMP) with fixed effects of gender, breed type, and gender x breed type interaction with pen as a random effect was used. Gender x breed type interactions were not significant for any traits. Male goats had heavier (P < 0.01) initial and final BW, but similar ADG during the trial. Male goats consumed more (P < 0.05) DMI, but had similar F:G and RFI compared with female goats. Gender did not affect feeding behavior traits, but male goats had greater BVER and more (P < 0.05) day-to-day variation in DMI than female goats. Purebred Boer goats had heavier (P < 0.05) initial and final BW and greater ADG than purebred Spanish and both F1 crosses. However, DMI and RFI were not affected by breed type. G:F was greater (P < 0.05) in Boer and Boer x Spanish goats (0.183, 0.153) than Spanish goats (0.115), with Spanish x Boer (0.132) goats being intermediate. Breed type did not affect feeding behavior traits in this trial. Minimal effects of gender and breed type on feed efficiency were detected in growing goats in this trial. Further research is warranted to examine effects of breed type on life-cycle feed efficiency including growing goats and female goats during pregnancy and lactation. [ABSTRACT FROM AUTHOR]

Virginiamycin (VM) possesses antimicrobial properties due to its blocking of protein synthase in Gram-positive bacteria, allowing it to reduce lactic acidosis and the incidence of liver abscesses in ruminants. Ruminal acidosis is a common metabolic disorder that affects feedlot and dairy cattle and occurs when the supply of organic acids from fermentation exceeds its absorption and degradation, accumulating acid content in the rumen. The objective of this study was to evaluate the effects of three different doses of VM administration on in vivo and in vitro ruminal digestion kinetics of beef steers consuming a high-grain diet [metabolizable energy (ME): 2.99 Mcal/kg; Crude Protein (CP): 15.2 % dry matter basis (DM)]. Nine ruminally cannulated British-crossbred steers (596 ± 49 kg) were assigned to this experiment. Animals were housed in three pens (n = 3/pen) equipped with a Calan gate feed system and water trough. Pens were enrolled in a 3×3 Latin square design containing three periods of 16 d, and a 5-d washout interval between periods. Dietary treatments consisted of VM administration at 0 mg/d (VM0), 180 mg/d (VM180), and 240 mg/d (VM240). During d 15 and 16 of each period, about 600 mL of rumen fluid was collected before (0 h) and at 4, 8, 12, and 16 h relative to the morning feed (0730 h) pH and redox potential (Eh) measurements were taken immediately after collection using a portable pH and redox meter, and subsamples were taken for volatile fatty acids (VFA), and NH3-N analyses. During the 4-h post-morning feed rumen collection, rumen inoculum was utilized to perform in vitro gas production (IVGP) measurements. All statistical procedures were performed using SAS software where steer was considered the experimental unit, and period and square were included as random. Acetate, propionate, and total VFA did not differ among treatments (P = 0.50), whereas butyrate increased linearly (P = 0.033) as the VM dose increased. Acetate:propionate ratio did not differ among treatments (P = 0.273). Lactate concentration decreased linearly (P = 0.027) as the VM dose increased; likewise, pH increased linearly (P = 0.019) as the VM dose increased. Branched-chain VFA and NH3-N concentrations increased linearly (P = 0.056) as the VM dose increased. The total and rate of gas production were similar among treatments (P = 0.161). However, second-pool gas production increased linearly as VM inclusion increased (P = 0.023). The in vitro neutral detergent fiber digestibility did not differ among treatments (P = 0.984). The provision of VM altered the rumen dynamics in a dose-dependent manner. Animals consuming high-grain diets will likely promote rumen health through a more stable pH and fermentation profile. [ABSTRACT FROM AUTHOR]

Rumen microbes serve a vital role in feed utilization of ruminant animals, suggesting the potential of rumen microbiota to influence inter-animal variation in nutrient utilization. There is limited knowledge surrounding the influence of the rumen bacterial community in animals selected based on feed efficiency. The objective of this study was to examine the differences in the rumen bacterial community in replacement Holstein heifers with divergent genomically enhanced breeding values for residual feed intake (RFIg). Genomic breeding values for RFIg were based on RFI phenotypes of 6,563 growing Holstein heifers from STgenetics ongoing EcoFeed research program. Holstein heifers (n = 55; initial BW = 351 ± 64 kg) with low RFIg (n = 29) or high RFIg (n = 26) were selected from a contemporary group of 453 heifers (RFIg = -0.023 ± 0.211 kg/d). These heifers were assigned to 1 of 2 pens, equipped with electronic feedbunks (GrowSafe Systems) and a GreenFeed gaseous-exchange measurement system (C-Lock). Individual DMI was collected for 84-d and BW measured weekly to determine phenotypic RFI. On d-70 of the study, a rumen sample was collected from each animal via esophageal tubing and bacterial community composition determined through 16S rRNA gene sequencing of the V4 region. A total of 523 amplicon sequence variants (ASVs) were observed among the 55 samples, with the average reads per sample of 54,107 ± 42,688 across samples. To examine the rumen bacterial composition, permutational multivariate analysis of variance (PERMANOVA) utilizing the weighted and unweighted Unifrac distance matrix was used. Utilizing the weighted Unifrac no differences (P = 0.513) were observed in the bacterial composition of the rumen content between heifers with divergent RFIg; however, utilizing the unweighted Unifrac differences (P = 0.031) were identified in the bacterial composition between heifers with divergent RFIg. Based on alpha diversity metrics, observed ASVs displayed greater (P = 0.015) bacterial richness in high-compared with low-RFIg heifers; however, there was no difference (P = 0.500) in the Shannon diversity index between heifers with divergent RFIg. ASV level classification of the most differentially abundant (P < 0.05; log2-fold change > 1) ASVs demonstrated that three ASVs from the bacterial family Prevotellaceae, and one ASV from the bacterial family Ruminococcaceae was predominant in high-compared with low-RFIg heifers. Additionally, one ASV belonging to the family Prevotellaceae was predominant in low-heifers compared with their high-RFIg counterparts. Results from this study indicate greater enrichment of ruminal bacteria in high RFIg cattle, with ASVs from the Prevotellaceae and Ruminococcaceae families differing between heifers with divergent RFIg. Opportunities exist to further investigate the role of the rumen microbiome in selection of cattle based on genomic RFI, and to assess associations between specific bacterial ASVs and phenotypic feed efficiency traits in cattle. [ABSTRACT FROM AUTHOR]

The objectives of this study were to evaluate the effects of breed and days on trial (DOT) on feed intake, growth rate, and feed efficiency of growing goats. Nineteen female goats (10 Alpine and 9 Spanish) with an initial BW of 38.8 ± 2.8 and 35.5 ±3.1 kg, respectively, were randomly assigned within breed to one of two pens (5 goats/pen), each equipped with GrowSafe feed bunks. A pelletized total mixed diet (TMD) was fed twice per day and goats had ad libitum access to feed and water throughout the 84-d trial. Daily feed intake (DMI) was collected with GrowSafe automated feeding system, and BW was measured biweekly. Linear regression of 14-d BW on DOT was used to derive ADG, mid-test metabolic BW (MBW) and expected DMI of individual goats at 42, 56, 70, and 84 DOT. Expected DMI was predicted by linear regression of DMI on MBW and ADG, with RFI calculated as a difference between actual and expected DMI for each DOT. Data were analyzed using a repeated-measures model with a fixed effect of breed, DOT as a repeated measure, and breed x DOT interaction with a pen as a random effect. The interaction was not significant for either of the response variables. Alpine goats had greater (P < 0.05) initial and final BW (37.6 kg and 51.7 kg, respectively) than Spanish goats (34.7 kg and 46.5 kg, respectively) although ADG (0.233 kg/d vs 0.191 kg/d) did not differ. DMI (P = 0.10) and RFI (P = 0.09) tended to be greater in Alpine than in Spanish goats (0.57 kg vs -0.64 kg). However, G:F was not affected (P > 0.70) by breed. As DOT increased from 42 to 84, MBW increased, while ADG, DMI, and G:F decreased. Further research is warranted to determine changes in phenotypic variances of ADG and DMI to determine the minimal DOT needed to accurately measure feed efficiency in growing goats. Our results suggest that Spanish goats tended to consume less feed and tended to be more efficient (negative RFI) than their counterpart Alpine goats. Further research is needed to compare the lifecycle efficiency of Alpine and Spanish goats. [ABSTRACT FROM AUTHOR]

The objective of this study was to examine the differences in performance, feed efficiency, and greenhouse gas emissions in Holstein heifers with divergent genomic residual feed intake (RFIg). Holstein heifers (n = 55; initial BW = 351 ± 64 kg) were classified as either low RFIg (n = 29) or high RFIg (n = 26) based on RFIg values determined from their genomic breeding values (Ecofeed index, STgenetics). Heifers were blocked by RFIg, stratified by BW and assigned to 1 of 2 pens, each equipped with 4 electronic feedbunks (GrowSafe Systems), with 1 pen equipped with a GreenFeed realtime gaseous-exchange measurement system (GEM; C-Lock). Heifers were fed a corn-silage based total mixed ration twice daily. Individual dry matter intake (DMI) was collected for 84 d and BW measured weekly. Phenotypic residual feed intake (RFIp) was calculated as the residual from the regression of DMI on average daily gain (ADG) and mid-test BW0.75. As only 1 of the 2 pens had a GEM system, during the 84-day study heifers were rotated between the two pens at 14 day intervals resulting in each group of heifers having three 14-day gaseous exchange measurement periods. A time series analysis of gaseous exchange measurements, with a repeated measure of measurement period, fixed effect of RFIg class and random effect of pen was conducted. A mixed model with RFIg class as fixed effect and pen as a random effect was used for analysis of the other response variables. There were no differences in initial or final BW and ADG for heifers with divergent RFIg; however, the low RFIg heifers consumed 7.3% less (P < 0.05) feed per day than their high RFIg counterparts. Consequently, low RFIg heifers exhibited a more favorable (P < 0.05) RFIp, with a RFIp of -0.188 and 0.211 kg/d for low and high RFIg heifers, respectively. There were no RFIg class by measurement period interactions (P > 0.10) for the greenhouse gas emissions measured. Low RFIg heifers had 7.7% less (P < 0.05) methane emissions (g/d) and 6.1% less (P < 0.05) carbon dioxide production (g/d) than their high RFIg counterparts. However, methane yield (g methane/kg DMI) was similar (P > 0.05) for low and high RFIg heifers. These results indicate that selection for low RFIg has the potential to identify cattle with favorable feed efficiency phenotypes. Additionally, selection based on RFIg provides the opportunity to produce cattle with fewer greenhouse gas emissions. Further research is warranted into selection based on RFIg through genomic indexes to improve feed efficiency and mitigate the environmental impact of cattle production. [ABSTRACT FROM AUTHOR]

Visual observations of social behavior and dominance relationships in cattle have been used to examine associations with productivity and well-being. This method is time consuming limiting the number of animals that can be evaluated. The objective of this study was to validate an algorithm to quantify feedbunk replacement events using data from an electronic feeding system. Crossbred beef steers (n = 20) fed a grower diet were housed in 1 of 2 pens each equipped with 3 electronic feedbunks (GrowSafe Systems) and video recorders. A trained video observer recorded all feedbunk replacement events and other agonistic activities at the feedbunk over a 4-d period (24 h/d). The electronic feeding system recorded the start and end timestamps of bunk visit (BV) events for each animal. An algorithm was developed to determine BV events deemed to be replacement events, defined as a BV event when an actor animal displaced a reactor animal from the feedbunk and occupied the same feeder within a specified period of time (replacement criterion). We calculated the recall and precision corresponding to replacement criterions from 1 to 60 s, and the optimum replacement criterion was determined to be between 18 and 20 s. The recall, precision and F-score of the algorithm using this replacement criterion were high (on average > 0.75). Furthermore, a replacement competition index was computed as a proxy for competitive feedbunk behavior, calculated as the number of actor-initiated replacement events divided by the total number of replacement events for each steer. Using Spearmans rank correlation we found high correlations (r > 0.7; P < 0.05) between the electronic and observed indices. These preliminary results demonstrate the potential of the GrowSafe system to quantify feedbunk replacement events for confined beef cattle, providing opportunities to evaluate associations between competitive feedbunk behavior and economically relevant traits. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine if the magnitude of interactive feeding activity at the feedbunk affects feed efficiency and feeding behavior patterns in beef cattle. This study used data from 498 crossbred steers (3 trials) fed high-concentrate diets in pens with electronic feed bunks (GrowSafe Systems). Timestamp data for bunk visit (BV) events were used to develop an algorithm to quantify those BV events deemed to be replacement events; Defined as those that occur when an animal displaces and replaces another animal from the feedbunk within a specified period of time (replacement criterion). For this study, a replacement criterion of ≤ 18 s was used. A replacement activity index (RAI) was computed for each steer as the number of replacement events divided by total BV events. Within pen, steers were classified into 1 of 3 phenotypes based on ± 0.5 SD from mean RAI. Steers with high RAI (> 0.5 SD from mean RAI) were hypothesized to be more interactive at the feedbunk, whereas steers with low RAI were less interactive at the feedbunk. A mixed model with RAI class as fixed effect, and trial and pen within trial as random effects was used for data analysis. The low RAI steers had 6% fewer BV events that were 12% longer (P < 0.001) in duration than high RAI steers. Additionally, eating rate (g/min) was 14% slower (P < 0.001) and time to approach the feedbunk following feed delivery 6 min longer (P < 0.001) in low vs high RAI steers. The low-RAI steers had substantially less (P < 0.01) feeding activity during peak feeding time than high RAI. Further research is warranted to evaluate interactive feeding activity at the feedbunk as a potential indicator of performance and feed efficiency in feedlot cattle. [ABSTRACT FROM AUTHOR]