Forage Utilization Research Articles

Soil health under forage and grazing lands in the humid United States

Abstract Soil health describes critical functions that can be influenced by land management. Some key soil characteristics are inherent and not altered appreciably, such as texture, mineralogy, and landscape position. Other soil properties and processes can be changed by land management, such as soil organic matter, nutrient concentrations, and the capacity to infiltrate and store water. How and when forage and grazing lands are harvested can modify photosynthesis and allocation of carbon to roots and exudates in soil. Grazing intensity, characterized primarily by stocking rate, is a key management strategy that alters cycling of carbon (C) and associated plant nutrients. Stocking method, nutrient amendment (source, timing, and rate), forage utilization strategy, season of grazing/deferment, type and class of livestock, and livestock distribution on the landscape are other important management strategies that can either negatively affect compaction, nutrient concentration, and greenhouse gas emissions or stimulate greater water holding capacity, slow and steady cycling of nutrients, and soil C and nitrogen (N) sequestration. Responses of soil health to pasture management can be effectively characterized by its essential functions: (i) producing plants for food and fiber, (ii) cycling nutrients, (iii) storing organically bound elements like C and N, (iv) protecting water quality, (v) supplying water and plant growth–promoting compounds, (vi) enabling animal habitat, (vii) harboring biodiversity, and (viii) buffering against toxic accumulation of trace metals and xenobiotic compounds. This review focused on soil health responses to forage and grazing land management in the humid region of the eastern United States. Areas for further research were also identified.

Strip-Grazing Stockpiled Annual Forages: Impact on Carrying Capacity and Cattle Performance

Abstract Strip grazing can increase forage utilization, though it has been shown to decrease individual animal performance. The objective of this study was to evaluate forage utilization and cattle performance when strip grazing (STRIP) vs. continuously grazing (CONT) stockpiled annual forages. Exp. 1 consisted of a mix of Jerry oats (Avena sativa) and Trophy rapeseed (Brassica napus) while Exp. 2 was a 17-species mix in which the forage mass was predominantly pearl millet (Pennisetum glaucum), german millet (Setaria italica), and browntop millet (Urochloa ramosa). Fields were divided into six 6.3 ha (Exp. 1) or 4.1 ha (Exp. 2) paddocks which were blocked by location. Treatment was randomly assigned within block (n = 3 replicates per treatment per Exp.). Grazing was initiated in November and terminated in February. This resulted in a total of 83 and 54 grazing days for Exp. 1 and 2, respectively. Forage was allocated to STRIP twice a week. The STRIP steers gained 16% less (P = 0.01) per day in Exp. 1, but in Exp. 2, there was no difference (P = 0.56) between treatments. Compared to CONT, carrying capacity (AUM/ha) of STRIP was increased (P = 0.03) by 81% in Exp. 1 and tended to increase (P = 0.10) in Exp. 2. Gain per hectare increased (P = 0.02) for STRIP by 56% in Exp. 1 and by 31% in Exp. 2. Strip grazing stockpiled annual forages can be an effective way to increase carrying capacity and gain per hectare during the fall and winter months but effects on individual animal performance are inconsistent. Disparities in response to strip grazing could stem from differences in forage quality and allocation. Further research is needed to refine and optimize the utilization of this management approach.

PSI-11 Effect of thymol on forage utilization, rumen fermentation, and rumen microorganisms in beef steers

Abstract Essential oils (EOs) have been extensively researched for their ability to modulate rumen microbial populations and, subsequently, rumen fermentation and enteric methane production. However, biological changes from dietary EOs are inconsistent due to the varying presence and concentrations of terpenes, the main bioactive component of EOs. Further, mechanisms by which terpenes exert their actions are not well understood due to structural variety and complexity. Therefore, terpenes should be researched individually and at known dosages. The objective of this study was to determine the effects of thymol on forage utilization and rumen microbial populations in beef steers. Thymol is a terpene from thyme and oregano EOs which is thought to reduce methanogenesis in ruminants. As thymol has potent antimicrobial activity, we aimed to identify a dose that favorably modulates microbial populations without interfering with forage utilization. Accordingly, we utilized beef steers (n = 4) in a 4×4 Latin square design experiment with four 28-d periods. Four doses of thymol [0 (CON), 120, 240, and 480 mg thymol/kg intake] were administered on alfalfa cubes to a basal hay diet which was provided ad libitum. Intake and digestion were determined on d 9 to 12 and rumen contents were collected then separated into liquid and solid fractions on d 14 of each period. DNA was extracted from the liquid and solid rumen contents and analyzed with whole genome shotgun sequencing. Forage organic matter intake, total digestible organic matter intake, and organic matter digestibility were not affected by treatment (P ≥ 0.66). Ruminal ammonia, total volatile fatty acids, and rumen pH were also not affected by treatment (P ≥ 0.30). However, for 240 mg thymol/kg intake, molar proportions of acetate were significantly increased compared with 120 mg thymol/kg intake (P ≤ 0.02) and tended to be greater than for 480 mg thymol/kg intake (P = 0.08). Propionate was significantly decreased (P ≤ 0.02) for 240 mg thymol/kg intake compared with other treatments. Numerous lactic acid bacteria (LAB) including multiple Lactobacillus, Enterococcus, and Pediococcus species were increased for thymol treatments compared with CON. The ammonia producing bacteria Prevotella bryantii was increased at 240 and 480 mg thymol/kg intake compared with 120 mg thymol/kg intake (P ≤ 0.05). Methanogenic microbial species, uncultured Methanobrevibacter sp., and total archaeal abundances were increased in the solid microenvironment versus CON for 240 mg thymol/kg intake (P ≤ 0.04). Ultimately, our data indicate that thymol did not negatively affect forage utilization or fermentation products, although microbial populations were affected. While methanogenic archaea were not reduced with thymol supplementation, the increases in LAB may indicate an alternative mechanism for thymol to modulate microbial populations and methanogenesis. These data provide insight into the impact of specific doses of thymol on cattle and provide a foundation for future research that specifically studies the mechanisms by which terpenes and EOs exert biological actions.

PSX-2 Productive performance of Raramuri Criollo, Angus x Raramuri Criollo and Hereford x Angus cows in a low-input cow-calf system in northern Mexico

Abstract Raramuri Criollo cattle (RC), a local heritage breed in the Chihuahua state of Mexico, are highly rustic and well-adapted animals that can contribute to cow productivity in a low-input cow-calf production system. The aim was to evaluate traits related to productive performance of purebred RC, Angus x RC (AC) and Hereford x Angus (HA) cows. Each cow breed group was randomly assigned to one of three pastures within each of two mountains dominant exposures and evaluated during 2022 and 2023 at Rancho Teseachi (28◦48′ N, 107◦25′ W) belonging to Universidad Autonoma de Chihuahua. The six grazing pastures ranged from 263 to 400 ha, with similar slope, altitude and water sources characteristics. The stocking rate was moderate (forage utilization <50%). Forage biomass availability for the period of use was sampled in October, and stocking rate adjusted accordingly in March. RC cows were bred with RC bulls, and AC and HA with Angus bulls. The breeding season was from September to November, and pregnancy diagnosis at mid-January. Non-pregnant cows were replaced by pregnant cows from other pastures of the same farm. Feed supplementation was limited in 2022 and according to nutritional requirements in 2023. Evaluated variables included calf birth (BW) and weaning weight adjusted (WW) to the average age at weaning (190 d in 2022 and 165 d in 2023); body condition score (BCS 1 to 9), cow body weight (CBW) at the beginning of the breeding season, as well as body weight of calf weaned by unit of cow weight (WW/CBW), and pregnancy rate (PR). A general linear model with fixed effects of breed group, sex, dominant exposure of mountains, their interaction, cow age subclass (Young, 4 yr; Middle, 5 to 8 yr; Adult, > 9 yr) and Julian date at calving as a covariate was adjusted using PROC GLM of SAS for continuous, normally distributed variables, and PROC CATMOD for pregnancy rate, leaving out sex and interaction effects. Means of BW and WW on calves from AC and HA cows were greater (P < 0.5) than those from RC cows in both years (Table 1). In 2022, the mean CBW of HA was greater (P < 0.5) than for AC, and this greater (P < 0.5) than for RC cows; BCS was greater for AC than for HA and RC, and PR lower (P < 0.5) for HA than for AC and RC. In 2023, there was no difference in CBW between AC and HA; BCS was similar (P > 0.05) among the three groups; and PR was the lowest (P < 0.5) for HA. The AC cows had the greatest WW/CBW mean (P < 0.5) in both years. Overall, using AC cows resulted on a combination of traits that outperformed on general productivity in the evaluated production system.

PSX-14 Effect of starch supplementation on rumen bacterial abundance in Bos taurus taurus steers consuming low-quality forage

Abstract Low-quality forage provides a limited supply of ruminally available nitrogen and is generally resistant to digestion, inhibiting microbial growth in the rumen and ultimately decreasing forage utilization. Supplementation with protein is well documented to increase forage utilization by promoting microbial growth. Even when protein requirements are met, additional energy, often provided as starch, may be required to meet performance expectations. The objective of this study was to evaluate the effect of increasing starch supplementation on rumen bacterial populations in Bos taurus taurus steers supplemented protein and consuming low-quality forage. Ruminal samples were collected from ruminally-cannulated Angus steers [n = 5; 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) ad libitum, and supplemented with one of four isonitrogenous (130 mg N/kg BW) supplements with increasing 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 4 h after supplementation and immediately frozen. Microbial DNA was extracted; full length 16S rRNA amplicon libraries were prepared using Kinnex kits and 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 and Bacteriodata were the most abundant phyla in all treatments (82% and 11%, respectively), and were not affected by starch supplementation (P ≥ 0.45). Actinobacteriota and Euryarchaeota abundance responded quadratically (P < 0.01) to increasing starch provision. 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. Increasing supplemental starch resulted in a quadratic response (P < 0.01) for abundance of Christensenellaceae R-7 and Lachnospiraceae XPB1014 groups. Relative abundance of Butyrvibrio was 4.05% for steers fed 2% starch supplement and increased to 18.24 and 11.85% for 20 and 38% starch, respectively and then decreased to 4.34% for steers fed 56% starch supplement (quadratic, P < 0.01) Abundance of Pseudobutyrvibrio followed a similar but less dramatic pattern (quadratic, P < 0.01). In contrast, abundance of Streptococcus and Methanobrevibacter decreased with the first two levels of starch and then increased with 56% (quadratic; P < 0.01). In conclusion, responses to the first two increments of starch supplementation suggest increased fibrolytic and decreased methanogenic activity. These results are supported by the previously reported increase in TDOMI for 20 and 38% starch 49.0 and 48.2 g/kg MBW, respectively versus 45.7 and 44.3 g/kg MBW for 2 and 56%, respectively.

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.

396 Effects of allocation timing on cattle performance and forage utilization when swath grazing a sorghum-sudangrass hybrid in eastern Nebraska

Abstract Swath, or windrow, grazing is the process of cutting hay, leaving it in windrows, and allowing cattle to graze these windrows in the winter. This grazing system reduces winter feeding costs by mitigating the need to bale and transport hay, while having the potential for increased utilization compared with grazing the forage standing. This study aimed to determine the effect of varying allocation timing on cattle performance and forage utilization. A sorghum-sudangrass hybrid (Sorghum× drummondii) was planted in June 2023, cut in early November, and grazed from mid-November 2023 to mid-January 2024. A 16-ha field was divided based on seeding rate with one-half seeded at the recommended rate of 39.2 kg/ha (REC) and one-half with a double rate of 78.4 kg/ha (DOU). The field was subdivided into a total of 8 paddocks (4 per seeding rate) with either 10 (n = 4) or 11 (n = 4) windrows. Forage was cut and windrows were gathered from a 4.57 m width in the field. Prior to grazing, a 0.30 m length of three swaths in each paddock was sampled to determine initial forage mass. A total of 60 steers [initial body weight (BW) = 240 ± 8.3 kg] were stratified by BW and assigned to one of 8 paddocks (n = 7 or 8 calves) to result in equal BW per swathed area. Allocations were offered in full once-per week (1X) or, one-half of the total forage was allocated twice weekly (2X). Post-graze samples were collected to estimate utilization and allocation amount was adjusted as needed based on visual appraisal of post grazing biomass. Cattle were pulled from the field due to snow cover after a 64-d grazing period. The area grazed was used to calculate the animal unit months/ha (AUM) achieved for each paddock. Pre-grazing forage mass did not differ between allocation timing (P = 0.89) or among seeding rates (P = 0.10; REC = 6,720 ± 545 kg/ha, DOU = 8,534.0 ± 545 kg/ha). There was an allocation timing by seeding rate interaction (P < 0.01) for forage offered with 1X (10.62 kgּ steer-1ּ d-1) being offered more (P < 0.01) than 2X (8.43 kg/steer/d) within REC, but no difference (P = 0.31) in forage offered due to allocation within DOU (8.31 kgּ steer-1ּ d-1). However, post grazing biomass (P = 0.35) and utilization (59 ± 8%) were not affected by allocation timing (P = 0.48). Average daily gain (ADG) also did not differ (P = 0.93) due to allocation timing (0.20 ± 0.07 kg). Most notably, there was a significant allocation effect (P = 0.05) on AUM/ha with 1X (14.51 ± 1.00) being lesser than 2X (16.82 ± 1.00). However, there was no significant difference (P = 0.30) in forage disappearance (291 ± 61 kg/AUM) due to allocation timing. This indicates that more frequent allocations can lead to increased carrying capacity. Increasing the frequency of allocation is a simple management practice producers can implement when swath grazing sorghum-sudangrass to increase carrying capacity.

402 The effect of supplemental protein degradability and frequency of supplementation on nitrogen metabolism of beef cattle consuming low-quality forage

Abstract Rumen degradable protein (RDP) is required for cattle consuming low-quality forage to ensure adequate fiber digestion. However, in situations where cattle are not supplemented daily, supplementing RDP could overwhelm the nitrogen recycling mechanisms, leading to increased nitrogen excretion. The objective of this experiment was to determine the effect of rumen degradability and frequency of supplemental protein in beef cattle consuming low-quality forage. Treatments were arranged in a 2 × 2 factorial with protein degradability (68.5% or 32.8% RDP) and supplementation frequency (daily or biweekly) as the two factors. Ruminally cannulated Angus steers [n = 8; body weight (BW) = 328 ± 12.2 kg] were used in a Latin rectangle. The low RDP treatment was composed of 50% soybean hulls and 50% corn gluten meal (40.3% CP; 32.8% RDP), and the high RDP treatment consisted of 45.4% soybean hulls, 41.4% soybean meal, 4.1% urea, and 9.1% molasses (40% CP; 68.5% RDP). The biweekly steers were supplemented on d 0, 4, 7, 11, 14, 18, and 21 of each period. Steers were given ad libitum access to low-quality (7.4% CP) native grass hay. Daily blood samples were collected from d 14 to 17 at 0630 h and d 21 at -2, 3, and 7 h relative to supplementation. Rumen fluid samples were collected every 4 h on d 18 to 21. Daily NEFA concentrations decreased (P < 0.001) post-supplementation in the biweekly supplemented steers and then returned to baseline values, while the daily supplemented steers had no change. Hourly NEFA concentrations in steers supplemented with high RDP biweekly increased from 2 h pre-supplementation to 3 h post-supplementation (P < 0.001), then decreased at 7 h post-supplementation back to pre-supplementation concentrations. Plasma urea nitrogen (PUN) increased in biweekly high RDP supplemented steers 1 d after supplementation (P < 0.001) and decreased from d 15 to d 17. PUN concentrations increased from 2 h pre-supplementation through 7 h post-supplementation in both high RDP treatments, while low RDP treatments did not change (P < 0.001). Rumen fluid lactate and ammonia concentrations rapidly increased in the biweekly high RDP-supplemented steers in response to each supplementation (P < 0.001). There were spikes in ammonia concentrations for the daily high RDP treatment post-supplementation; however, they were smaller in magnitude compared with the biweekly high RDP. The low RDP treatments remained steady across all hours of ammonia sampling, where daily and biweekly supplemented steers decreased slightly in the time points following supplementation and then gradually increased. Rumen pH displayed drastic changes in the biweekly high RDP-supplemented group with values ranging from 6.99 to 5.97 (P < 0.001), but the low RDP treatments remained consistent. Supplementing biweekly with high RDP resulted in fluctuations in metabolites not observed in the other treatments, which could reduce forage utilization and increase nitrogen excretion.

96 Using greenhouse gas flux to estimate forage dry matter intake in ad libitum fed replacement heifers

Abstract An accurate estimate of feed intake is a critical component in determining individual animal feed efficiency. However, existing feed intake measurement systems are not designed for unprocessed, dry forage diets. Open-circuit gas flux technology measures enteric gas emissions for cattle in a pasture-based setting. If a significant relationship exists between feed intake and gas emissions, this system could be used to rank grazing cattle for forage intake and forage utilization efficiency. Our objective was to develop prediction equations to estimate forage dry matter intake using gas flux and performance data. Angus and Angus x Hereford heifers [n = 71; initial body weight (BW) 329.5 ± 31.1 kg] were used over 3 yr to measure intake, gain, and gas flux. All heifers were subject to a 21-d adaptation and 71-d intake test using individual intake technology (SmartFeed; C-Lock Rapid City, SD) with a stocking rate of 3.3 heifers per feeder. Throughout the study, heifers were fed a long-stem, unprocessed, grass hay diet (≥ 10.8% CP, 2.0 Mcal ME, and 56% TDN) with ad libitum access to a salt/mineral supplement. The GreenFeed system (C-Lock Rapid City, SD) was used to monitor oxygen (O2) consumption (means ± SD; 3364.4 ± 374.8 g/d), methane (CH4; 181.4 ± 24.3 g/d) and carbon dioxide (CO2) production (4,965.3 ± 494.5 g/d). Body weights were collected every 14 d, and average daily gain (ADG) was calculated by regressing BW on day of study. The phenotypic correlations of forage DMI with CO2, CH4, O2, and heat production (HP) were 0.72, 0.66, 0.74, and 0.74, respectively. Average daily gain and midpoint metabolic BW combined with the estimate of daily HP, O2, or CO2 accounted for 60% of the variation in forage DMI. These results suggest that forage intake can be predicted using performance data in conjunction with the GreenFeed gas quantification system.

Digestive utilization of Sahelian forages associated with cowpea haulms (Vingna unguiculata) and blood profile in Arabic rams

Digestive utilization of sahelian forages associated with Vingna unguiculata and blood profile study was conducted in scientific garden of the University of Sciences and Technology, Ati (JSUSTA). Three forages were used to assess in vivo digestibity in eighteen (18) rams weighing around 31.83±3.02 kg and displayed individually in metabolic cages in six (6) groups of three (3) animals. Control groups received 1000g of feed made up of Brachiaria deflexa, Dactyloctenium aegyptium and Echinocloa colona. While, experimental groups received basal feeds associated with 30% of Vingna unguiculata. The experiment was preceded by 14 days adaptation and 7 days of data collection during which, hundred (100g) grams of feeds and feces as well as urine (10 ml) were collected for chemical analysis and digestibility assessment. At the end of experimentation, two (2) ml of blood was collected from each animal before and after feeding for blood profile analysis. The results showed that the association of 30% Vingna unguiculata have significantly (p<0.05) increased intake of D. aegyptium and B. deflexa in Arab rams. In vivo digestibility of E. colona was significantly (p<0.05) higher in rams when associated or no with 30% of Vingna unguiculata. Blood profile analysis showed that E. colona associated with 30% of Vingna unguiculata induced significant (p<0.05) increase in blood protein, globulin and cholesterol concentration in Arabic rams.

Advances in smallholder large ruminant production and profitability in Southeast Asia over the past decade – lessons from the Mekong region: a review

The global demand for protein in the form of red meat is growing, especially in Southeast Asia, with income and population growth driving an increase in global beef consumption projected to continue from 2023 to 2032. This provides incentive for smallholder large-ruminant producers to build on production improvements obtained over the past decade to ensure long-term profitability and sustainability. This review aims to provide an update on advances in smallholder large-ruminant production and profitability in Southeast Asia over the past decade, as well as highlight ongoing challenges that require further investment from governments and the private sector to meet the growing regional and global demand for protein that is safe for human consumption. Improvements are discussed in detail across the areas of health, production and welfare, using outputs from research for development projects across Southeast Asia, specifically Cambodia and Laos which have high proportions of population living below the national poverty line. Areas covered include nutrition, disease control, diversification and farmer engagement. Ongoing challenges and opportunities are also considered. Key improvements in smallholder large-ruminant production, health and welfare in Southeast Asia over the past decade include the introduction of strategies to improve nutrition through forage utilisation and disease control through vaccination and biosecurity as well as farmer engagement and diversification. However, major challenges continue in the areas of disease control and eradication, training, climate variability, gender empowerment and policy. Increasing global demand for red meat places smallholder large-ruminant producers throughout Cambodia and Laos in an ideal position to capitalise. To do this and gain improved regional food security requires ongoing investment in stakeholder training and adoption of appropriate strategies to ensure greater productivity from existing numbers and resisting increasing numbers in an environment with limited resources. Although the challenges for large-ruminant smallholders are substantial, the rewards for continual investment to improve health and production include increased household incomes and profitability as well as greater regional food security.

Mealworm larvae and black soldier fly larvae as novel protein supplements for cattle consuming low-quality forage.

The global population is projected to increase, indicating that there will be greater demand for animal protein to meet the associated food needs. This demand will place additional pressure on livestock systems to increase output while also minimizing natural resource inputs. Insect protein has emerged as a potential alternative to conventional protein feeds, such as soybean meal. Mealworm larvae (MWL; Tenebrio molitor) have been studied in poultry and swine as an alternative protein source; however, there is no research currently evaluating MWL for cattle. Black soldier fly larvae (BSFL; Hermetia illucens) have also received attention for their potential use in livestock feed due to their scalability and nutritional value, but research in cattle is limited. The objective of this study was to evaluate the effects of whole-dried MWL and defatted BSFL as protein supplements for cattle consuming forage. Five ruminally cannulated steers were utilized in a 5 × 5 Latin square experiment to determine how MWL and BSFL supplementations affect forage utilization. Steers consuming ad libitum low-quality forage (76.5% neutral detergent fiber [NDF], 4.2% crude protein) were provided one of the five treatments each period: 1) control with no supplement (CON), 2) soybean meal (CONV), 3) BSFL, 4) MWL, or 5) 50/50 by-weight blend of BSFL and MWL (MIX). All treatments were provided at 100 mg N/kg BW and periods included 8 d for treatment adaptation, 5 d for intake and digestion, and 1 d for ruminal fermentation measures. Protein supplementation stimulated forage organic matter intake (FOMI; P ≤ 0.01) relative to CON (3.28 kg/d). There was a significant difference in FOMI (P ≤ 0.01) between BSFL (4.30 kg/d) and CONV (4.71 kg/d), but not between CONV and MWL (P = 0.06, 4.43 kg/d). Total digestible OM intake (TDOMI) was also stimulated by the provision of protein (P ≤ 0.01), from 1.94 kg/d for CON to an average of 3.24 kg/d across protein supplements. Organic matter digestibility (OMD) and NDF digestibility (NDFD) were not affected by treatment (P ≥ 0.37), for an average OMD of 66.5% and NDFD of 62.7%. There was also no treatment effect on ruminal volatile fatty acid (P = 0.96) or ammonia-N (P = 0.22) concentrations. These data indicate that MWL may stimulate forage utilization by beef cattle to a greater extent than BSFL, but both are viable protein supplements.

Economically optimized forage utilization choices in drylands for adapting to economic, ecological, and climate stress

Improving the economic performance of range forage in drylands internationally faces challenges from economic, ecological, and climate stress. Stakeholders in these drylands wish to protect range forage ecosystems while assuring economic viability of ranching. Despite several recent research achievements, little work to date has integrated relationships among precipitation, grazing pressure, animal performance, and forage production to protect ranching incomes faced with economic, ecological, and climate stress in dryland areas. This work addresses that gap by developing an empirical mathematical programming model for optimizing economic performance of livestock grazing on range forage ecosystems that adapt to several stressors. Its unique contribution is to formulate and apply a ranch income optimization model calibrated using positive mathematical programming. The model replicates observed economic, forage, and climate conditions while accounting for interacting relations among stocking rates, forage conditions, grazing pressure, animal performance, and ranch economic productivity. Results show ranch incomes ranging from about $5 to $88 per acre and marginal values of forage ranging from $0.01 to $0.12 per pound of forage, depending on economic, ecological, and climate conditions. Results reveal how all these stressors affect economically optimized choices of grazing levels, ranch income, and economic values of forage for a range of six biomes seen in the US west. Results help livestock ranchers to adjust stocking and forage choices as well as farm policymakers who seek flexible government programs to adapt to changes in economic, ecological, and climate conditions. The work's importance comes from applicability to forage management problems in dry regions internationally.

Dairy effluent applications to a pasture enhance soil fertility and microbial activity without impacting soil bacterial and fungal community composition

Farm dairy effluents (FDE) from washing the milking parlor contain manure, urine, and chemicals and constitute a large amount of wastewater. Applying FDE as soil fertilizers to pastures can enhance forage yield and improve soil nutrient status. Since the dairy industry is increasingly attempting to maximize returns through better utilization of forage with lesser inputs, there is demand for a supply of FDE as fertilizers. Nevertheless, the impact of this practice on soil microbiota remains largely unexplored. It must be studied before large-scale soil disposal to avoid diminishing microbial diversity or enhancing pathogen abundance. This study evaluated the effects of applying lagoon-stored (Lagoon) and raw dairy effluents (Raw) at a rate of 50 kg N ha−1 in four equal doses, in comparison to urea fertilization, on soil fertility and the activity, abundance, and community structure of soil microbiota. Raw was obtained after solid separation, and Lagoon corresponds to the Raw stationed in a two-lagoon system. Microbial activity was assessed as basal respiration, potentially mineralizable N, potential nitrification activity, and enzymatic activities. The catabolic activity of the microbial community was evaluated using Biolog Ecoplates™. Bacterial and fungal community composition and diversity were analyzed through amplicon sequencing of 16S rRNA and ITS2. The application of FDE benefited soil fertility and microbial activity. Lagoon had the most potent effects on soil available P and extractable K+, Na+, Mg2+ and Ca2+. Soil treated with Raw displayed higher microbial activities, such as dehydrogenase, basal respiration, urease, and potentially mineralizable N, than the other treatments. FDE did not significantly alter the microbial composition, abundance, or functional diversity. In conclusion, in this short-term trial, despite changes in soil chemical properties and microbial activity, the composition and diversity of the bacterial and fungal communities remained unaffected by FDE irrigation.

91 Mealworm and black soldier fly larvae as protein supplements for beef steers consuming forage

Abstract The global population is projected to increase, indicating there will be greater demand for animal protein to meet the associated food needs. This demand will place additional pressure on livestock systems to increase output while also minimizing natural resource inputs. Insect protein has emerged as a potential environmentally sustainable alternative to conventional protein feeds, such as soybean meal. Further, insect protein does not compete in the human food market as the products of conventional oil crops often do. Mealworm larvae (MWL) has been studied in poultry and swine as an alternative protein feed; however, there is not currently research evaluating MWL for cattle. Black soldier fly larvae (BSFL) has also received attention for its potential use in livestock feed due to its scalability and nutritional value, but research in cattle is limited. The objective of this study was to evaluate the effects of whole dried MWL and defatted BSFL as protein supplements for cattle consuming forage. These procedures were approved by IACUC at Texas State University (#7726). Five ruminally cannulated steers were utilized in a 5×5 Latin square experiment to determine how MWL and BSFL supplementation affect forage utilization. Steers consuming low-quality forage (4.2% crude protein) were provided one of five treatments each period: 1) control with no supplement (CON), 2) soybean meal (CONV), 3) BSFL, 4) MWL, and a 5) 50% BSFL and 50% MWL by-weight (MIX). Supplements were provided at 100 mg N/kg BW. Periods included 8-d for treatment adaptation, 5-d for intake and digestion measurements, and 1-d for ruminal fermentation measures. Dry matter (DM), organic matter (OM), CP, neutral detergent fiber (NDF), and acid detergent fiber (ADF) were determined for diet, ort, and feces. Protein supplementation stimulated forage OM intake (P ≤ 0.01) relative to CON. There was a significant difference in FOMI (P ≤ 0.01) between BSFL and CONV. Steers receiving CONV treatment consumed 4.71 kg FOMI/d, which was significantly greater (P ≤ 0.01) than those receiving BSFL (4.30 kg/d). There were not differences in FOMI between other treatment groups. Total digestible OM intake (TDOMI) was stimulated by protein supplementation (P ≤ 0.01) from 1.94 kg/d for CON to an average of 3.24 kg/d across protein supplements. Organic matter digestibility (OMD) and neutral detergent fiber digestibility (NDFD) were not affected by treatment (P ≥ 0.37), for an average OMD of 66.5% and NDFD of 62.7%. There was also not a treatment effect (P = 0.96) on total volatile fatty acid (VFA) concentrations, although there were some shifts in molar proportions of individual VFAs across treatments. These data indicate that MWL may be more efficacious than BSFL in stimulating forage utilization in beef cattle, but both are viable protein supplements.

3 Measuring feed intake in cows

Abstract In recent years, substantial progress has been made in understanding the sources of biological variation and genetic components of feed efficiency in growing animals consuming energy-dense mixed diets during the post-weaning phase. Much less is known about within-animal variation of feed efficiency for beef cows consuming moderate to low-quality forage diets common to most cow/calf production systems. Considerable evidence indicates the existence of a genetic by environment interaction for feed efficiency. Phenotype for feed intake and feed efficiency are most practically and cost effectively determined during the post-weaning growing stage. However, due to the additional nutrient sinks associated with gestation and lactation, and the cost, labor and technology required to measure economically relevant traits in mature cows, little is known about forage utilization efficiency in beef cows. The beef cow/calf segment of the industry represents, by far, the greatest opportunity to reduce beef production input costs and reduce the industry’s carbon footprint. We reason that selection tools for feed intake and feed efficiency developed over the last 20 years are effective for the post-weaning growing and finishing phases, although only marginally effective for beef cows consuming unprocessed, moderate to low-quality forage. In this session, we will discuss challenges, opportunities, and experiences associated with measuring forage intake and recovered energy in beef cows.

Growth, haemato-biochemical, hormonal and disease characteristics in Black Bengal goats: a review.

The goats have been considered one of the noteworthy animals to provide food security and could promote socio-economic upliftment under challenging climatic scenarios in the coming decades, particularly in the tropics. Black Bengal goat (BBG) is one of the recognised native meat-type breeds of hot-humid tropics with distinguished characteristics, including superior-quality meat, excellent skin and high prolificacy. Smaller body mass, lower metabolic rate and efficient utilisation of high-fibre forages enable BBG to adapt to a wide range of harsh climates in the tropics. The BBG can maintain physiological homeostasis efficiently in terms of electrolyte profile, endocrine functions and haemato-biochemical traits in different life phases, including the gestation period, even in high-saline coastal areas of hot-humid tropics. Crossbreeding to improve its growth rate has been attempted, but the prolificacy has been decayed. This review is intended to attract global attention to the adaptive potentialities of Black Bengal goats in terms of growth and production, haemato-biochemical, endocrinological, salt tolerance and disease characteristics that could be an asset of climate-resilient agricultural farming.