King Ranch Bluestem Research Articles

PSIX-19 Effect of protein and starch level on N balance and ruminal fermentation parameters in steers consuming low-quality forage: Bos taurus taurus

Abstract Globally cattle convert low-quality forage to beef and milk; therefore, understanding protein utilization in Bos taurus taurus is critical to enhancing sustainability as over and under-supplementation of protein are economically and environmentally costly. Low-quality forage lacks the N necessary for proper utilization and metabolic function. Supplemental protein improves low-quality forage utilization and is expected to increase N absorption and retention. Supplement starch can increase volatile fatty acid (VFA) production and energy supplied to the animal; however, too much starch decreases ruminally available N and pH potentially decreasing fibrolytic activity. Accordingly, our objective was to determine the effect starch supplementation on N balance and ruminal fermentation parameters in Bos taurus steers. Ruminally cannulated Angus steers [n = 5; body weight (BW) = 375 ± 45 kg] were used in a 4 × 4 Latin square to evaluate the effect of decreasing supplemental starch when consuming King Ranch Bluestem hay (3.5% CP, 73% NDF). Steers received four isonitrogenous (130 mg N/kg BW) supplements providing increasing levels of starch (2% starch = 100% soybean meal; 20% starch = 26.3% corn, 73% soybean meal, 0.7% urea; 38% starch = 51.6% corn, 47% soybean meal, 1.4% urea; 56% starch = 78.6% corn, 19% soybean meal, 2.4% urea). Five 14-d periods were conducted, consisting of 9 d adaptation and 4 d to measure intake and digestion, and 1 d for ruminal fermentation. Supplemental N intake decreased linearly (P < 0.01) with increasing starch as the crude protein content of the soybean was underestimated. Forage and total N intake were not affected by starch level (P ≥ 0.17). Fecal and total urinary N excretion were not different between starch levels (P ≥ 0.43). Urinary ammonia-N and urea-N averaged 6.6 and 16.8% of total urinary N excretion, respectively, but no differences between starch levels were observed (P ≥ 0.39). Level of starch supplementation had no effect on N retention and absorption (P ≥ 0.50). There was a treatment × time interaction observed for ruminal ammonia concentration (P < 0.01). All treatments, except 2% starch, peaked at 4 h post feeding, 20 and 38% treatments gradually decreased following four, but the concentration of ruminal ammonia decreased by 80% between 4 h and 8 h after feeding in the 56% starch treatment. Starch level had no effect total VFA concentration, VFA molar proportions, or ruminal pH (P ≥ 0.10). In conclusion, providing supplemental starch did not affect N balance or VFA production when fed to steers consuming low-quality forage. Nitrogen balance and VFA production likely were not affected because all supplements provided sufficient ruminally available N and, therefore, exerted minimal effects on forage utilization.

PSX-15 Effect of starch supplementation on rumen bacterial abundance in Bos taurus indicus steers consuming low-quality forage

Abstract Deficient ruminally available nitrogen caused by a basal diet of low-quality forage can limit microbial growth in the rumen and decrease forage utilization. Protein supplementation is well-documented to improve forage digestibility and performance. Additionally, starch has been evaluated to increase energy supply to grazing cattle when the forage cannot support adequate levels of production. However, most research in this area has been conducted in Bos taurus taurus, especially the response of the rumen microbiome to supplementation. Accordingly, the objective of this study was to evaluate the effects of increasing starch supplementation on rumen bacterial populations in Bos taurus indicus steers supplemented protein and consuming low-quality forage. Ruminal samples were collected from five ruminally-cannulated Brahman steers (BW 420 ± 55 kg) used in a 4×4 Latin square fed a basal diet of King Ranch Bluestem Hay (3.5% CP and 73% NDF) provided ad libitum, and one of four isonitrogenous (130 mg N/kg BW) supplements with increasing levels of starch (2% starch= 100% soybean meal; 20% starch= 73% soybean meal, 26.2% corn, 0.8% urea; 38% starch = 47% soybean meal, 51.6% corn, 1.4% urea; 56% starch= 19% soybean meal, 78.6% corn, 2.4% urea). Rumen content samples were collected via rumen cannula at 4h post-feeding. Microbial DNA was extracted; full length 16S rRNA amplicon libraries were prepared using Kinnex kits and then sequenced on the PacBio Revio platform. Reads were analyzed using DADA2 and QIIME2. Statistical analysis was performed with the GLIMMIX procedure of SAS 9.4 (SAS Inst. Inc., Cary, NC). Firmicutes, Bacteroidata, Actinobacteriota, Verrucomicrobiota, and Euryarchaeota were the most abundant phyla in all treatments (83, 10, 3, 0.4, and 1%, respectively), and were not affected by treatment (P ≥ 0.10). Christensenellaceae R-7 group, Rikenellaceae RC9 gut group, Lachnospiraceae-XPB1014-group, Butyrvibrio, Lachnospiraceae-NK3A20-group, and Prevotella represented the most abundant genera for all treatments (7, 5, 11, 9, 7, and 3%, respectively). Lachnospiraceae-XPB1014-group and Lachnospiraceae-NK3A20-group responded quadratically (P ≤ 0.02) to increasing starch with decreased abundance for the 20% and 38% starch supplement. Comparatively, relative abundance of Butyrvibrio responded quadratically (P < 0.01) with increased abundance in the 20% and 38% starch supplement. Pseudobutyrvibrio increased with supplementation of 20% starch and then decreased as starch supplementation increased (quadratic, P = 0.04). In conclusion, supplementation of starch elicited changes in microbial relative abundance at the genus level with the response in Butyrivibrio suggesting greater fibrolytic activity. Forage and total digestible NDF intake in these steers decreased with increased starch supplementation; however, TDOMI was not affected by starch provision.

93 Ruminal archaea and bacteria metatranscriptomic responses to supplementation in steers fed low-quality forage

Abstract Forage comprises the majority of beef cattle diets globally, and its quality can vary. Supplementation presents a significant opportunity to improve the efficiency of production. Supplementation has been shown to increase ruminally available nitrogen, improve forage utilization, and reduce livestock methane (CH4) emissions. However, corresponding effects of supplementation on gene expression of rumen microbiota, in particular metabolic pathways involved in methanogenesis, have yet to be studied. This study aimed to evaluate the effect of supplement composition before and after feeding on rumen archaeal and bacterial gene expression in steers consuming a low-quality forage diet. Ruminal samples were collected from five ruminally cannulated Angus steers [body weight (BW) = 375 ± 45 kg] used in a 4 × 4 Latin square fed a basal diet of King Ranch Bluestem Hay (3.5% CP, 73% NDF), and one of four isonitrogenous (130 mg N/kg BW) supplements. Steers provided the two most divergent supplements (2% starch, 43% CP; 56% starch, 21% CP) were used for metatranscriptomic analysis. Rumen fluid samples were collected via rumen cannula 0 and 4 h post-feeding. Total RNA was extracted and sequenced. Differentially expressed genes (DEGs) were identified and functionally annotated. Pathway enrichment analysis was completed to determine enriched pathways (broad metabolic pathways) and modules (specific metabolic reactions). Only main effects are presented in this abstract. Archaeal hydrogenotrophic and methylotrophic methanogenesis reactions and tryptophan biosynthesis reactions were upregulated in the 2% starch supplement (P < 0.05). The 2% starch supplement resulted in fewer bacterial total upregulated carbohydrate-active enzymes compared with the 56% starch supplement (957 vs. 1,695 DEGs, respectively; P < 0.05), and an increased proportion of cellulose and hemicellulose-specific enzymes (35 vs. 29%, respectively; P < 0.05). The 56% starch supplement resulted in upregulation of the bacterial 3-Hydroxypropionate bi-cycle reaction (P < 0.05). Collection time exerted a larger effect than supplement composition on both archaeal and bacterial gene expression, with 83% and 63% of DEGs associated with time, respectively (P < 0.05). Archaeal hydrogenotrophic methanogenesis and carbon metabolism were upregulated 4 h post-feeding. In addition, 1,704 bacterial carbohydrate-active enzymes were upregulated 4 h post-feeding, as compared with 975 upregulated at 0 h (P < 0.05). However, these differences in DEGs did not correlate with significantly enriched pathways of bacterial carbohydrate metabolism. These findings demonstrate improvements to low-quality forage utilization, through CP and starch supplementation, can be correlated to relevant changes in gene expression of rumen microbiota. Furthermore, they demonstrate that supplementation influences the expression of methanogenesis reactions, suggesting an opportunity to affect CH4 production. Additional studies quantifying forage utilization, rumen microbiota gene expression and CH4 production are needed to further optimize supplementation strategies for improved efficiency of beef production whilst maintaining or reducing its carbon footprint.

401 Effect of protein and starch supplementation level on intake and digestibility by steers consuming low-quality forage: I. Bos taurus

Abstract A deficiency of ruminally available N (RAN) caused by a basal diet of low-quality forage depresses forage utilization. Supplemental protein improves forage utilization by increasing RAN, resulting in increased intake and potentially improving digestion. Addition of starch to a supplement can increase total digestible organic matter (OM) intake (TDOMI); however, too much starch decreases RAN and pH potentially decreasing forage utilization. Our objective was to determine the effect of starch supplementation on intake and digestion in Bos taurus indicus steers. Accordingly, five ruminally cannulated Brahman steers [body weight (BW) = 420 ± 55 kg) were used in a 4 × 4 Latin square to evaluate the effect of decreasing supplemental starch when consuming King Ranch Bluestem hay (3.5% CP, 73% NDF). Steers received four isonitrogenous (130 mg N/ kg BW) supplements providing increasing levels of starch (2% starch = 100% soybean meal; 20% starch = 26.3% corn, 73% soybean meal, 0.7% urea; 38% starch = 51.6% corn, 47% soybean meal, 1.4% urea; 56% starch = 78.6% corn, 19% soybean meal, 2.4% urea). Five 14-d periods were conducted, consisting of 9 d adaptation and 4 d to measure intake and digestion, and 1 d for ruminal fermentation. As designed, supplement OM intake (SOMI) increased linearly (P < 0.01) as starch level increased. Other measures of intake, including forage OM intake (FOMI), total OM intake (TOMI), and total neutral detergent fiber intake (TNDFI) decreased in a cubic manner in response to increasing starch (P ≤ 0.04). Forage OMI also responded with a cubic decrease (72.2, 68.9, and 69.5 g/kg BW0.75) when the protein supplement contained 2, 20, and 38% starch, respectively, but decreased to 61.2 g/kg BW0.75 when the 56% starch supplement was provided. Similarly, TOMI decreased 5.3% when starch inclusion increased from 38 to 56%. Total tract OM digestion and NDF digestion were not significantly affected (P ≥ 0.86) by starch level in the supplement; therefore, despite TOMI and TNDFI decreasing, there was no effect on total digestible OM intake and (TDOMI) and total digestible NDF intake (TDNDFI). In conclusion, providing supplemental starch over 38% decreased forage utilization. Decreases in FOMI with starch inclusion may be attributed to competition for RAN between fiber fermenting and starch fermenting bacteria.

PSII-23 Effect of Protein Supplementation Level and Degradability on N Balance in Steers Consuming Low-Quality Forage: Ii.Bos Taurus Indicus

Abstract Low-quality forage lacks the nitrogen (N) necessary for optimal forage utilization and animal performance. Supplemental protein improves forage utilization by increasing ruminally available N and energy supply to the animal. Together these two are expected to increase N absorption and balance. Therefore, our objective was to determine the effect of ruminal degradability and level of protein supplementation on N balance in Bos taurus indicus steers. Accordingly, six ruminally cannulated Brahman steers (BW 369 ± 51 kg) were used in a 5 × 5 Latin square to evaluate the interaction between level and degradability of protein supplementation when consuming King Ranch Bluestem hay (3.5% CP, 71.0% NDF). Treatments were arranged as a 2 × 2 factorial with steers receiving protein supplements (43% CP) with two ruminal degradable protein levels; 35% RDP (35%; 58% corn gluten meal and 42% soybean hulls) and 70% RDP (70%; 100% soybean meal). Supplements were fed at two levels, providing 1.26 or 2.53 g of supplement/kg BW (LOW and HIGH). A control (CON) provided no supplement. Five, 14-d periods, consisted of 9 d adaptation and 4 d to measure intake, digestion, and N balance, and 1 d for ruminal fermentation. No degradability × level interactions were significant (P > 0.10) for any measures of N balance. Forage organic matter intake increased (P < 0.01) in response to supplementation, forage N intake tended to increase (P = 0.06). Supplemental N intake increased with increased supplementation, as designed, (P < 0.01) resulting in a significant increase in total N intake (P < 0.01). Degradability tended (P = 0.09) to affect supplement N intake with 70% RDP being greater than 35% RDP. Fecal N excretion increased 50% for LOW and 68% for HIGH (P < 0.01) compared with CON but did not differ (P = 0.24) between RDP levels. Urinary N excretion increased with increasing level (P < 0.01) and degradability (P < 0.01) of the protein supplement. Urinary N excretion increased 250% for the 70% HIGH supplement and 84% for the 35% HIGH supplement. Nitrogen absorption increased from -3.8 g N/d for unsupplemented steers to 38.8 and 48.8 g N/d for the 35% HIGH and 70% HIGH, respectfully (P < 0.01). Nitrogen retention increased (P = 0.03) with level of supplementation from -19.1 g N/d for unsupplemented steers to 10.6 and 9.7 g N/d for 35% HIGH and 70% HIGH, respectfully. Providing supplemental N to Bos taurus indicus increased N intake, excretion, absorption, and retention. Level of ruminal degradability did not affect the amount of N retained or absorbed suggesting that protein supplementation regardless of ruminal N degradability will improve N balance in Bos taurus indicus consuming low-quality forage.

363 Effect of Protein and Starch Supplementation Level on Intake and Digestibility By Steers Consuming Low-Quality Forage: I. Bos Taurus Taurus

Abstract A deficiency of ruminally available N (RAN) caused by a basal diet of low-quality forage depresses forage utilization. Supplemental protein improves forage utilization by increasing RAN, resulting in increased intake and potentially improving digestion. Addition of starch to a supplement can increase total digestible OM intake (TDOMI); however, too much starch decreases RAN creating competition between fiber and starch fermenting bacteria potentially decreasing forage utilization. Our objective was to determine the effect of starch supplementation on intake and digestion in Bos taurus taurus steers. Accordingly, five ruminally cannulated Angus steers (BW 375 ± 45 kg) were used in a 4 × 4 Latin square to evaluate the effect of decreasing supplemental starch when consuming King Ranch Bluestem hay (3.5% CP, 73% NDF). Steers received four isonitrogenous (130 mg N/ kg BW) supplements providing increasing levels of starch (2% starch = 100% soybean meal; 20% starch = 26.3% corn, 73% soybean meal, 0.7% urea; 38% starch = 51.6% corn, 47% soybean meal, 1.4% urea; 56% starch = 78.6% corn, 19% soybean meal, 2.4% urea). Five 14-d periods were conducted, consisting of 9 d adaptation and 4 d to measure intake and digestion, and 1 d for ruminal fermentation. As designed, supplement OM intake (SOMI) increased linearly (P < 0.01) as starch level increased. Forage OM intake (FOMI) decreased linearly with increasing starch (P < 0.01). Increases in SOMI and decreases in FOMI combined to result in no significant (P ≥ 0.14) differences in total OMI (TOMI) between starch levels. Total digestible OMI (TDOMI) responded quadratically (P = 0.05) to increasing starch and was 45.8, 49.4, 48.4 and 41.9 g TDOMI/kg BW0.75 for 2, 20, 38, and 56% starch, respectfully. Total DOMI was 18% greater when steers were provided 20% starch supplement compared with 56% starch. Similarly, total digestible NDF intake responded quadratically (P = 0.05) and was maximized with 20% starch. Total tract OM digestion and NDF digestion were not significantly affected (P ≥ 0.15) by starch level in the supplement. In conclusion, providing supplemental starch over 20% decrease forage utilization. Decreases in FOMI with starch inclusion may be attributed to competition for RAN between fiber fermenting and starch fermenting bacteria.

PSII-22 Effect of Protein Supplementation Level and Degradability on N Balance By Steers Consuming Low-Quality Forage: I.Bos Taurus Taurus

Abstract Globally, cattle convert low-quality forage to beef and milk; therefore, understanding protein utilization in Bos taurus taurus is critical to enhancing sustainability as over and under-supplementation of protein are economically and environmentally costly. Low-quality forage lacks the N necessary for proper utilization and metabolic function. Supplemental protein improves low-quality forage utilization and is expected to increase N absorption and retention. Accordingly, our objective was to determine the effect of ruminal degradability and level of protein supplementation on N balance in Bos taurus taurus steers. To achieve this objective, six ruminally cannulated Angus steers (BW 294 ± 37.7 kg) were used in a 5 × 5 Latin square to evaluate the interaction between level and degradability of protein supplementation when consuming King Ranch Bluestem hay (3.5% CP, 71.0% NDF). Treatments were arranged as a 2 × 2 factorial steers receiving protein supplements (43% CP) with two ruminal degradable protein levels; 35% RDP (35%; 58% corn gluten meal and 42% soybean hulls) and 70% RDP (70%; 100% soybean meal). Supplements were fed at two levels, providing 1.26 or 2.53 g of supplement/kg BW (LOW and HIGH, respectively). A control (CON) provided no supplement. Five, 14-d periods, consisted of 9 d adaptation and 4 d to measure intake, digestion, and N balance, and 1 d for ruminal fermentation. No significant (P ≥ 0.14) degradability × level interactions were detected for any measures of N balance. Although forage organic matter intake increased (P < 0.01) in response to supplementation, forage N intake was not improved. Supplemental N intake increased linearly (P < 0.01) with increased supplementation, as designed, resulting in a significant linear (P < 0.01) increase in total N intake. In addition, 70% RDP supplement resulted in greater supplemental N intake than the 35% RDP supplement. Fecal N excretion increased linearly with supplementation. Supplementation at the HIGH level increased (P < 0.01) fecal N excretion 90% compared with CON. There was no significant (P = 0.94) effect of ruminal degradability. Urinary N excretion was greater (P < 0.01) when the 70% RDP supplement was fed than the 35% RDP. Nitrogen absorption linearly increased with supplementation (P < 0.01). Similarly, nitrogen retention linearly increased (P < 0.01) with level of supplementation but was not significantly affected by degradability (P = 0.87). In conclusion, providing supplemental N to Bos taurus taurus increased N intake, excretion, absorption, and retention. Level of ruminal degradability did not affect N retention or absorption suggesting that protein supplementation regardless of ruminal N degradability improves N balance in Bos taurus taurus consuming low-quality forage.

PSII-3 Effect of Protein Supplementation Level and Degradability on Forage Utilization by Steers Consuming Low-Quality Forage: II. Bos taurus indicus

Abstract A deficiency of ruminally available N (RAN) caused by a basal diet of low-quality forage may depress forage utilization. Supplemental protein improves utilization by addressing the RAN therefore increasing intake and potentially improving digestibility. The objective of this study was to determine the effect of ruminal degradability and level of protein supplementation on forage utilization by Bos taurus indicus steers. Accordingly, five ruminally cannulated Brahman steers (BW 369 ± 51 kg) were used in a 5 × 5 Latin square to evaluate the interaction between level and degradability of protein supplementation when consuming a basal diet of King Ranch Bluestem hay (3.5% CP, 71.0% NDF). Treatments were arranged as a 2 × 2 factorial with steers receiving protein supplements (43% CP) having two levels of protein degradability (35 or 70% RDP) fed at two levels of supplementation, 1.26 or 2.53 g/kg BW (LOW and HIGH). A control treatment providing no supplemental protein was also included (CON). Five 14-d periods were conducted, consisting of 9 d adaptation, 4 d to measure intake and digestion, and 1 d for ruminal fermentation. No degradability × level interactions were observed for any measures of intake or digestion (P > 0.10). Protein supplementation linearly increased (P < 0.01) total digestible OM intake (TDOMI), NDF intake (P = 0.01), and total digestible NDF intake (DNDFI; P < 0.03). Total digestible OMI was greater in steers receiving 70% RDP than the 35% RDP (P = 0.08). This response resulted from the linear increase in FOMI with 75% RDP (P = 0.03), that was not observed with 35% RDP. Despite differences in FOMI, TDOMI increased linearly (P ≤ 0.03) for both 35 and 70% RDP, partially the result of providing a highly digestible supplement. Forage OMI differences also resulted in NDFI being greater for 70% RDP than 35% RDP (P = 0.06) and DNDFI increasing linearly with the addition of both supplements (P ≤ 0.03). Organic matter digestibility (OMD) increased linearly with supplementation as a result of supplement provision. In contrast to observations previously reported in Bos taurus steers, provision of 35% RDP supplement did not improve FOMI. Supplementation with 70% RDP improved FOMI 19 and 20% compared to the basal diet at LOW and HIGH levels, respectively. A portion of this relatively modest response to protein supplementation could be attributed to greater intake in the unsupplemented controls.

PSII-2 Effect of Protein Supplementation Level and Degradability on Forage Utilization by Steers Consuming Low-Quality Forage: I. Bos taurus taurus

Abstract A deficiency of ruminally available N (RAN) caused by a basal diet of low-quality forage may depress forage utilization. Supplemental protein improves utilization by increasing RAN therefore increasing intake and potentially improving digestibility. The objective of this study was to determine the effect of ruminal degradability and level of protein supplementation on forage utilization by Bos taurus taurus steers. Accordingly, six ruminally cannulated Angus steers (BW 294 ± 37.7 kg) were used in a 5×5 Latin square to evaluate the interaction between level and degradability of protein supplementation when consuming King Ranch Bluestem hay (3.5% CP, 71.0% NDF). Treatments were arranged as a 2×2 factorial with steers receiving protein supplements (43% CP) with two levels of protein degradability (35 or 70% RDP) fed at two levels of supplementation, providing 1.26 or 2.53 g/kg BW (LOW and HIGH). A control treatment (CON) provided no supplemental protein. Five 14-d periods were conducted, consisting of 9 d adaptation and 4 d to measure intake and digestion, and 1 d for ruminal fermentation. No degradability × level interactions were significant for any measures of intake or digestion, although there was a tendency for an interaction (P = 0.09) for total organic matter intake (TOMI), resulting from a tendency for a quadratic (P = 0.08) increase when supplemented. In contrast, the 70% RDP supplement continued to increase TOMI linearly (P < 0.01), suggesting the maximum effective level of supplementation was not reached. As expected, protein supplementation increased all measures of intake such as, forage OMI (FOMI), total digestible OMI (TDOMI), and NDF intake (P < 0.01). In addition, level of supplementation affected all measures of intake (P ≤ 0.01) with HIGH being greater than LOW. Protein supplements with 70% RDP at LOW increased FOMI 28% versus control when supplemented at LOW, and 47% at HIGH. Supplementation with 35% RDP increased FOMI 23% at the LOW and 28% at HIGH indicating the lower degradability supplement was less effective at improving forage utilization that the 70% RDP supplement (P = 0.01). Total NDF intake (NDFI) followed this same pattern with 70% RDP supplementation increasing NDFI 29 and 52% with LOW and HIGH supplementation, respectfully; 28 and 37% when 35% RDP supplementation was provided (P = 0.10). Despite the effect of protein supplementation on intake, OM digestion (OMD) and NDF digestion (NDFD) were not affected by protein supplementation regardless of degradability or level (P ≥ 0.23). In conclusion, FOMI and TDOMI were increased with the provision of greater levels and more degradable supplements resulting in better forage utilization.

Evaluation of Black Soldier Fly larvae (Hermetia illucens) as a protein supplement for beef steers consuming low-quality forage.

Black Soldier Fly larvae (BSFL; Hermetia illucens) has been the focus of recent feeding trials in poultry, swine, and fish; however, in vivo research has not yet been conducted in cattle. Accordingly, a study was conducted to evaluate the effects of BSFL as a protein supplement in beef steers. Six steers (603 ± 20 kg of BW, n = 3 and 404 ± 17 kg of BW, n = 3) consuming King Ranch bluestem hay (6.55% dry matter [DM] crude protein [CP]) ad libitum were used in two simultaneous 3 × 3 Latin squares. Steers were provided one of three treatments each period: 1) a control with no supplement (CON), 2) a supplement comprised of conventional feed ingredients with whole cottonseed and soybean meal as the main protein sources (CONV), and 3) a supplement with BSFL as the main protein source (BSFL). Three 14-d periods were conducted with 8 d to adapt to treatments, 5 d to measure intake and digestion, and 1 d to complete a ruminal fermentation profile. DM, organic matter (OM), CP, neutral detergent fiber (NDF), and acid detergent insoluble ash were determined in forage, supplement, ort, and fecal samples. Protein supplementation as CONV or BSFL stimulated forage OM intake (P ≤ 0.01) relative to CON with a trend for a difference (P = 0.08) between the supplements such that CONV steers consumed more FOMI than BSFL steers. Treatment affected total digestible OM intake (TDOMI; P ≤ 0.01); TDOMI for CON steers was 47.5 g/kg metabolic body weight (MBW) which was significantly less (P ≤ 0.01) than that of CONV or BSFL steers. Steers supplemented with CONV consumed significantly more TDOMI than BSFL steers (P = 0.05; 62.2 vs. 60.1 g/kg MBW, respectively). Treatment did not significantly affect digestibility of DM, OM, or NDF (P > 0.32). There was also not a significant effect (P ≥ 0.17) of treatment on ruminal ammonia-N, total volatile fatty acids, or ruminal pH. Overall, these data indicate that BSFL may be an effective protein supplement for beef cattle consuming low-quality forage.

Invasive grasses in South Texas rangelands: historical perspectives and future directions

AbstractSouth Texas is home to a high diversity of species due to its location at the confluence of subtropical, desert, and coastal ecoregions. Historical overgrazing of South Texas rangelands transformed the savanna and prairie to a landscape dominated by woody plants and shrubs interspersed with low seral grass species and bare ground. During the first half of the 20th century, exotic grass species, coupled with the application of industrial agricultural practices appeared to be the future of forage production in South Texas and elsewhere. Several of these exotic species, namely King Ranch bluestem [Bothriochloa ischaemum(L.) Keng], Kleberg bluestem [Dichanthium annulatum(Forssk.) Stapf], Angelton bluestem [Dichanthium aristatum(Poir.) C.E. Hubbard], buffelgrass [Pennisetum ciliare(L.) Link], guineagrass [Urochloa maxima(Jacq.) R. Webster], Lehmann lovegrass (Eragrostis lehmannianaNees), and Bermudagrass [Cynodon dactylon(L.) Pers.], have escaped pasture cultivation. Additionally, the native grass tanglehead [Heteropogon contortus(L.) P. Beauv. ex Roem. & Schult.] has begun displaying invasive behaviors. The monoculture growth habit of these species simplifies vegetation structure, reduces biodiversity, and decreases habitat for many species of wildlife. These grasses also alter natural fire regimes and nutrient cycling. This landscape-level transformation of vegetation composition and structure requires monitoring to quantify and assess the spatial and temporal distributions of invasive species as a basis to inform management practices. Current advances in remote sensing technologies, such as very high spatial resolution coupled with daily satellite imagery and unmanned aerial vehicles, are providing tools for invasive vegetation monitoring. We provide a synthesis of the natural history of these grasses, including their introductions, an overview of remote sensing applications in South Texas, and recommendations for future management practices.

Can Nicosulfuron plus Metsulfuron Effectively Control or Suppress King Ranch Bluestem?

Core Ideas Nicosulfuron plus metsulfuron combinations failed to effectively control KR bluestem even when used in consecutive years. Lack of control in permanent plots was due to the high populations and also the crown bud bank, which were not entirely killed by herbicide treatments. Glyphosate provided effective control at the end of each growing season and provided 55 to 60% control the following spring. The use of herbicides alone is probably not an effective method for control or suppression for KR bluestem. Research was conducted in south-central Texas to evaluate nicosulfuron plus metsulfuron combinations or glyphosate for King Ranch (KR) bluestem (Bothriochloa ischemum var. Songarica) control. In one study, at one location, where KR bluestem was interspersed in a Tifton 85 bermudagrass [Cynodon dactylon (L.) Pers. × C. nlemfuënsis Vanderyst] pasture, control up to 9 weeks after an early fall application was 98% for nicosulfuron plus metsulfuron combinations and 99% for glyphosate. At another location, with a solid stand of KR bluestem, control was 60% or less for nicosulfuron plus metsulfuron combinations. When evaluated the following spring, control at either location was no better than 25% for nicosulfuron plus metsulfuron combinations and 60% for glyphosate. In another 2-year study with permanent plots having a solid stand of KR bluestem, control was ineffective for nicosulfuron plus metsulfuron combinations applied in either late spring, mid-summer, or early fall. When evaluated in mid- to late December, the best control was provided with sequential applications, either in late spring plus mid-summer or mid-summer plus early fall while in another year, the mid-summer plus early fall sequential applications were best. However, none of these sequential applications had greater than 45% control. Applying nicosulfuron plus metsulfuron combinations reduced KR bluestem herbage yields up to 10% as compared with the untreated check.

Carbon Sequestration of Soil and Plants along IH-35 in Bexar County, Texas

Soil and vegetation were evaluated along IH-35 within Bexar County for carbon content. The objectives of this study were to evaluate the vegetative composition and carbon sequestration potential of vegetation along IH-35. Three 20 m transects were placed at each site and percent vegetative cover was estimated and above ground plant biomass and soil was collected from three 0.25 m2 subplots along each transect. Plant and soil samples were analyzed for carbon content using the loss-on-ignition method. Two non-native grasses, bermudagrass and King Ranch bluestem, were the dominant cover. Bermudagrass was more efficient in absorbing CO2 compared to King Ranch bluestem. The top 10 cm of soil in all samples contained more organic carbon than the lower 10 cm. Collection of field data has been completed and the soil and plant carbon content is being analyzed with the final results presented at the conference.

Thermal acclimation of leaf respiration varies between legume and non-legume herbaceous

Ubiquitous thermal acclimation of leaf respiration could mitigate the respiration increase. However, whether species of different plant functional groups showing distinct or similar acclimation justifies the simple prediction of respiratory carbon (C) loss to a warming climate. In this study, leaf dark respiration (Rd) of illinois bundleflower (IB, legume), stiff goldenrod (GR, C₃ forbs), indian grass, little bluestem and king ranch bluestem (IG, LB and KB, C₄ grass) were measured with detached leaves sampled in a 17-year warming experiment. The results showed that Rd at 20°C and 22°C (R₂₀ and R₂₂) were significantly lower in the warming treatment for all the five species. Lower R₂₂ in warmed than R₂₀ in control in GR, KB, LB and IG imply acclimation homeostasis, but not in IB. The significant decline in temperature sensitivity of respiration (Q₁₀) of GR resulted in the marginal reduction of Q₁₀ across species. No significant changes in Q₁₀ of C₄ grasses suggest different acclimation types for C₃ forbs and C₄ grass. The magnitude of acclimation positively correlated with leaf C/N. Our results suggest that non-legume species had a relative high acclimation, although the acclimation type was different between C₃ forbs and C₄ grasses, and the legume species displayed no acclimation in Rd. Thus, the plant functional types should be taken into account in the grassland ecosystem C models.

Old World Bluestem Seedling Emergence and Vegetative Cover Following Glyphosate Treatment

Old world bluestems (OWB) are perennial warm-season grasses introduced into the U.S. from parts of Asia, eastern Europe, Africa, and Australia. The two most common old world bluestem species found in Kansas are yellow bluestem (Bothriochloa ischaemum), otherwise known as King Ranch bluestem, and Caucasian bluestem (Bothriochloa bladhii). These grasses were introduced for soil conservation and forage production in arid regions of the southern Great Plains; however, in Kansas and elsewhere, they have escaped areas where planted and have been invading native rangelands and pastures that were old crop fields seeded back to native grasses. Efforts to control OWB in native rangelands and native seeded pasture have had short term success, but the abundant seed produced from mature OWB plants has resulted in a soil seedbank capable of producing high populations of new seedlings. However, the length of time that this seedbank is capable of producing new seedlings has received relatively little investigation. The goal of this project was to evaluate new OWB seedling emergence from the soil seedbank for two years following OWB control with glyphosate.

Ropewick Application to Control Old World Bluestems

Old world bluestems (OWB) were introduced into the United States in the early 1900s for conservation and forage purposes. The two main OWB species found throughout the southern Great Plains are Caucasian bluestem (Bothriochloa bladhii) and yellow or King Ranch bluestem (Bothriochloa ischaemum). These introduced OWB grasses are warm-season grasses with excellent persistence and production characteristics for regions with low rainfall. These grasses also produce abundant seed and establish more easily under arid conditions compared to some of our most common native warm-season grasses of the Great Plains. The characteristics that enable OWB to be well adapted and to grow and persist in the Great Plains also enable OWB to become invasive and encroach areas where it is not wanted. Several studies have examined herbicides to control OWB, and glyphosate products showed the most economical and promising short-term control success. However, glyphosate is a non-selective herbicide and has the potential to injure almost all vegetation with which it comes into contact, including desirable native species that may be growing among a stand of sprayed OWB. Wick applicators have been used extensively in grain row crop systems to wipe herbicide on weedy species that grow taller than the desirable grain crop. Because OWB matures more quickly than many native species, OWB could potentially be treated with a wick applicator as it matures following its elongation and elevation above native grass species. Therefore, applying glyphosate with a ropewick applicator to control OWB warranted investigation.

Detection of the Red-Streaked Leafhopper,Balclutha rubrostriata(Melichor) (Hemiptera: Cicadellidae), on an Invasive Grass Species in Oklahoma

The invasive red-streaked leafhopper, Balclutha rubrostriata (Melichar) (Hemiptera: Cicadellidae), was previously reported in Central Texas and Louisiana. Collected primarily on the introduced grass King Ranch bluestem, Bothriochloa ischaemum (L.) Keng var. songarica, which occurs throughout Oklahoma and in the Tallgrass Prairie, the red-streaked leafhopper threatens native grassland ecosystems because it could potentially disrupt established invertebrate assemblages. To determine if the species moved north into Oklahoma, patches of King Ranch bluestem along roadways in central Oklahoma were swept in November 2013, and captured individuals resembling the red-streaked leafhopper were preserved in 95% ethanol at -20°C for subsequent identification. Samples from McClain and Payne counties in Oklahoma contained individuals identified as the red-streaked leafhopper by morphological characteristics of the genitalia. Genomic DNA was extracted from the red-streaked leafhoppers and from a panel of field-collected leafhopper species. Novel species-specific primers amplified a 570- bp fragment of the mtCOI gene of the red-streaked leafhopper only. Sequencing of the PCR amplicons confirmed the morphological identifications. Few red-streaked leafhoppers were collected at two of the three sampling areas in 2013. Sampling efforts were expanded in 2014 to more regions of Oklahoma including the Tallgrass Prairie resulting in eight more locations with the red-streaked leafhopper. This report constitutes the first evidence of the leafhopper in Oklahoma as far north as Osage County in the Tallgrass Prairie Preserve and includes the development of novel PCR primers for specific identification of the red-streaked leafhopper. Potential ecological impacts of this invasive species on native grassland leafhoppers are discussed.

Rapid Spread ofBalclutha rubrostriata(Hemiptera: Cicadellidae) in Texas and Southwestern Louisiana, USA with Notes on its Associated Host Plants

The red streaked leafhopper, Balclutha rubrostriata (Melichar) (Hemiptera: Cicadellidae), is an invasive insect from southeastern Asia that is known to be a vector of the phytoplasma that causes Sugarcane White Leaf Disease (SCWL). Sugarcane is a vital crop for the United States and is being considered as a biofuel source. The purpose of this survey was to determine whether B. rubrostriata has established populations in Texas and Louisiana, USA; and, if established, to estimate its range expansion. The gulf coast region of Texas, east Texas, and 2 southwestern parishes of Louisiana were surveyed for the red streaked leafhopper. Samples of the leafhopper were collected in all Gulf Coast regions and the majority of east Texas counties. However, it was only collected in one Louisiana parish. The leafhopper appears to be closely associated with an invasive grass, King Ranch Bluestem, Bothriochloa ischaemum (L.), throughout much of its present range in the United States, and it is now common along much of the Texas Gulf Coast and is moving into Louisiana.

Prescribed Extreme Fire Effects on Richness and Invasion in Coastal Prairie

AbstractWidely-held, untested assumptions in many prairies are that high-intensity fires conducted during droughts will decrease native herbaceous species richness and lead to rapid invasions by alien species. We compared native and exotic herbaceous species richness and aboveground herbaceous biomass one year following the application of high-intensity growing-season fires in Texas coastal prairie. Fires were conducted in June 2008, when precipitation was 96% below the long-term monthly average, at the end of a severe 5-mo drought, resulting in high fire intensities within treatment units. Native forb species richness was greater in burned than unburned areas. In contrast, species richness of native grasses, exotic forbs, and the frequency of King Ranch (KR) bluestem [Bothriochloa ischaemum(L.) Keng.] did not significantly differ between burned and unburned treatments. The potential to use prescribed extreme fire to maintain native herbaceous species richness while not increasing KR bluestem provides preliminary evidence that growing season fires conducted during droughts can be a viable management strategy in coastal prairies.

Can the Study of Natural Vegetation Succession Assist in the Control of Soil Erosion on Abandoned Croplands on the Loess Plateau, China?

Abstract In the Loess Plateau, China, arable cultivation of slope lands is common and associated with serious soil erosion. Planting trees or grass may control erosion, but planted species may consume more soil water and can threaten long‐term ecosystem sustainability. Natural vegetation succession is an alternative ecological solution to restore degraded land, but there is a time cost, given that the establishment of natural vegetation, adequate to prevent soil erosion, is a longer process than planting. The aims of this study were to identify the environmental factors controlling the type of vegetation established on abandoned cropland and to identify candidate species that might be sown soon after abandonment to accelerate vegetation succession and establishment of natural vegetation to prevent soil erosion. A field survey of thirty‐three 2 × 2–m plots was carried out in July 2003, recording age since abandonment, vegetation cover, and frequency of species together with major environmental and soil variables. Data were analyzed using correspondence analysis, classification tree analysis, and species response curves. Four vegetation types were identified and the data analysis confirmed the importance of time since abandonment, total P, and soil water in controlling the type of vegetation established. Among the dominant species in the three late‐successional vegetation types, the most appropriate candidates for accelerating and directing vegetation succession were King Ranch bluestem (Bothriochloa ischaemum) and Lespedeza davurica (Leguminosae). These species possess combinations of the following characteristics: tolerance of low water and nutrient availability, fibrous root system and strong lateral vegetative spread, and a persistent seed bank.