Fire management effects on ruminal digestibility and in vitro methane emissions of subtropical rangeland plant species.

Prescribed fire is a common management practice used to manipulate rangeland plant productivity and composition. Although the nutritive value of most herbaceous plant species is considered poor for grazing animals, native rangelands in Florida are an important source of forage for livestock, especially during the winter months, when the productivity of cultivated perennial warm-season pastures is limited. This study evaluated the effects of prescribed fire on methanogenic potential and nutritive value of selected native rangeland plant species. Treatments were a 3 × 2 factorial arrangement of plant species (creeping bluestem [Schizachyrium scoparium var. stoloniferum {Nash} Wipff], wiregrass [Aristida stricta {Michx.}], or saw palmetto [Serenoa repens {W. Bartram} Small]) and prescribed fire management [2 yr after burning (control) vs. 1 yr after burning (burned)] distributed in a randomized complete block design with four replicates. Samples were analyzed for crude protein (CP), neutral detergent undigestible fiber (NDF), in vitro methane production, and in situ ruminal disappearance. Prescribed fire generally increased forage CP and DM effective degradability relative to control; however, no effect was observed on saw palmetto. Wiregrass had the least CP concentration in both burned (8.5%) and control (2.3%). In burned treatments, creeping bluestem and palmetto had greater DM effective degradability (62% and 58%) than wiregrass (53%). Fire increased in vitro gas production by 60 (creeping bluestem) to 90% (wiregrass) relative to control treatments. No effect of fire on methane production was observed for any of the plant species evaluated in this study. Creeping bluestem had the greatest methane production (12.5 mg/g DM), followed by wiregrass (5.3 mg/g DM) and saw palmetto (1.4 mg/g DM). Methane:DM effective degradability decreased in the following order: creeping bluestem ≥ wiregrass > saw palmetto. Data indicated prescribed fire was an effective tool to increase creeping bluestem and wiregrass nutritive value but no effect was observed on saw palmetto. Cattle grazing grass-dominated rangelands will likely emit more gas and methane than shrub or tree-dominated ecosystems; however, the greater forage nutritive value and subsequent positive impacts on animal production are expected to offset a substantial fraction of enteric methane emissions.

Greenhouse gas mitigation and carbon sequestration potential in humid grassland ecosystems in Brazil: A review.

Climate change is a major constraint on the sustainability of the humid tropics, maintaining ecosystem services, food production, and social functioning. Humid tropics play an essential role in C storage and greenhouse gas (GHG) emission reduction. Unfortunately, unplanned economic exploration, human occupation, and lack of knowledge of techniques to maintain ecosystem services negatively affect the humid tropics. In this study, we focused on the mechanisms of GHG emissions, C storage, and their mitigation strategies. This review indicated technologies that can be adopted by farmers in humid tropics to maintain or increase their capacity to store C stocks and reduce GHG emissions. The adoption of climate-smart agriculture technologies and the regulation of ecosystem services markets will accelerate the progress of preserving the humid tropics. Improved management practices, such as proper N fertilizer management and the introduction of N2-fixing legumes, can increase soil C sequestration, providing economic and environmental trade-offs associated with these management strategies. Public and private investments toward knowledge dissemination and technology adoption regarding GHG emissions reduction and soil C storage are needed to allow humid tropics to maintain their critical function of generating environmental and societal benefits.

Monensin supplementation during late gestation of beef cows alters maternal plasma concentrations of insulin-like growth factors 1 and 2 and enhances offspring preweaning growth.

This study evaluated the effects of maternal prepartum supplementation of dried distillers grains (DDG), with or without monensin addition, on maternal performance and physiology and offspring preweaning growth. On day 0 (approximately 197 ±â€…4 d prepartum), 150 multiparous, Brangus crossbred beef cows were ranked by their initial body weight (BW; 524 ±â€…51 kg) and body condition score (BCS; 5.0 ±â€…0.63), and then randomly assigned into one of 15 bahiagrass (Paspalum notatum) pastures (10 cows and 8.1 ha/pasture). Maternal treatments were randomly assigned to pastures (5 pastures/treatment) and consisted of no prepartum supplementation of DDG (NOSUP) or supplementation of DDG at 1 kg/cow/d (dry matter basis; DM) added with 0 mg (SUP) or 200 mg/d of monensin (SUPMO) from days 0 to 77. Effects of maternal treatment and maternal treatment × day of the study were not detected (P ≥ 0.63) for any forage data. Cow BCS on day 35 and near calving (day 77) did not differ (P ≥ 0.19) between SUP and SUPMO cows but both groups had greater (P ≤ 0.001) BCS compared with NOSUP cows. Cow BCS at the start of the breeding season (day 142) and on day 168 were the greatest (P < 0.0001) for SUPMO cows, least for NOSUP cows, and intermediate (P ≤ 0.02) for SUP cows. Maternal plasma concentrations of glucose did not differ (P ≥ 0.25) among treatments. Plasma concentrations of insulin-like growth factor 1 (IGF-1) on day 77 were the least for NOSUP cows (P ≤ 0.05) and did not differ (P = 0.66) between SUP and SUPMO cows, whereas plasma concentrations of IGF-2 on days 35 and 77 were greatest (P ≤ 0.05) for SUPMO cows and did not differ (P ≥ 0.60) between NOSUP and SUP cows. Birth BW of first offspring did not differ (P = 0.77) between SUP and SUPMO calves but NOSUP calves were lighter at birth (P ≤ 0.05) compared with SUP and SUPMO calves. Percentage of cows pregnant with a second offspring did not differ (P = 0.72) between SUP and SUPMO cows and were the least for NOSUP cows (P ≤ 0.05). First offspring BW at weaning (day 325) was greatest (P ≤ 0.05) for SUPMO calves, least for NOSUP calves, and intermediate for SUP calves. Therefore, adding monensin into prepartum DDG supplements for Bos indicus-influenced beef cows did not increase cow prepartum BCS but led to greatest offspring preweaning growth, likely by modulating maternal plasma concentrations of IGF-1 and IGF-2 during gestation.

Frequency of maternal supplementation of energy and protein during late gestation modulates preweaning growth of their beef offspring.

This study evaluated the effects of decreasing the frequency of dried distillers grains (DDG) supplementation during third trimester of gestation on cow physiology and offspring preweaning growth. At 201 ± 7 d prepartum (day 0 of the study), 120 Brangus crossbred cows were stratified by body weight (BW = 543 ± 53 kg) and body condition score (BCS = 5.47 ± 0.73), and then assigned randomly to 1 of 20 bahiagrass (Paspalum notatum) pastures (six cows and 4.7 ha/pasture). Treatments were randomly assigned to pastures (five pastures/treatment) and consisted of cows offered no DDG supplementation (NOSUP) or precalving supplementation of DDG dry matter at 1 kg/cow daily (7×), 2.33 kg/cow every Monday, Wednesday, and Friday (3×), or 7 kg/cow every Monday (1×) from day 0 to 77. All cows assigned to DDG supplementation received the same total amount of DDG dry matter (77 kg/cow) from day 0 to 77. All cow-calf pairs were managed similarly from day 77 until calf weaning (day 342). Supplementation frequency did not impact (P ≥ 0.16) any forage or cow reproduction data. Cow BCS on days 77, 140, and 342 did not differ among 1×, 3×, and 7× cows (P ≥ 0.29) but all supplemented cows, regardless of supplementation frequency, had greater BCS on days 77, 140, and 342 compared to NOSUP cows (P ≤ 0.04). Cows offered 1× supplementation had greater plasma concentrations of IGF-1 on days 35 and 140 compared to NOSUP, 3× and 7× cows (P ≤ 0.04), whereas 3× and 7× cows had greater plasma concentrations of IGF-1 on day 35 compared to NOSUP cows (P ≤ 0.005). Average plasma concentrations of glucose did not differ among 1×, 3×, and 7× cows (P ≥ 0.44), but all supplemented cows had greater plasma concentrations of glucose compared to NOSUP cows (P ≤ 0.05). Birth BW of the first offspring did not differ between 3× and 7× calves (P = 0.54) but both groups were heavier at birth compared to NOSUP calves (P ≤ 0.05). On day 342, calves born from 7× cows were the heaviest (P ≤ 0.05), whereas calves born from 1× and 3× cows had similar BW (P = 0.97) but both groups were heavier compared to calves born from NOSUP cows (P ≤ 0.05). In summary, decreasing the frequency of DDG supplementation, from daily to one or three times weekly, during third trimester of gestation of beef cows did not impact cow BCS but altered maternal plasma concentrations of IGF-1 and glucose, leading to reduced offspring preweaning growth.

Stair-step strategy and immunomodulatory feed ingredient supplementation for grazing heat-stressed Bos indicus-influenced beef heifers.

On day 0 of years 1 and 2, 64 Brangus crossbred heifers per year were stratified by initial body weight (BW) and age (mean = 257 ± 20 kg and 271 ± 22 d) and allocated into 16 bahiagrass (Paspalum notatum) pastures (4 heifers per pasture per yr). Treatments were randomly allotted to pastures in a 2 × 2 factorial arrangement of treatments (4 pastures per treatment per yr). Treatments consisted of concentrate dry matter (DM) supplementation at 1.50% of BW from days 0 to 100 (CON) or concentrate DM supplementation at 1.05% of BW from days 0 to 49 and 1.95% of BW from days 50 to 100 (SST). Then, each respective supplementation strategy was added or not with immunomodulatory feed ingredients from days 0 to 100 (OMN; 4 g/45 kg of BW). Heifers were assigned to an estrus synchronization protocol from days 100 to 114. Heifers detected in estrus from days 111 to 114 were inseminated (AI) 12 h after estrus detection. Heifers not detected in estrus were timed AI on day 114. All heifers were exposed to Angus bulls from days 120 to 210 (1 bull per pasture). Effects of supplementation strategy × OMN inclusion × hour were detected (P < 0.0001) only for intravaginal temperature from days 26 to 30, which were the least (P ≤ 0.03) for SST heifers offered OMN supplementation and did not differ (P ≥ 0.17) among all remaining treatments from 0830 to 1600 hours. Effects of supplementation strategy × OMN inclusion and OMN inclusion were not detected (P ≥ 0.12) for any variable, except for the percentage of heifers detected in estrus, which was greater (P = 0.01) for heifers supplemented with vs. without OMN. Total concentrate DM offered from days 0 to 100 and heifer BW on days 0 and 56 did not differ (P ≥ 0.49) between CON and SST heifers, but SST heifers were heavier (P ≤ 0.01) on days 100 and 210 compared with CON heifers. Body surface temperature on day 25 and plasma IGF-1 concentrations on day 75 were greater (P ≤ 0.04) for SST vs. CON heifers. Percentage of pubertal heifers, heifers detected in estrus, and pregnancy to AI did not differ (P = 0.36) between SST and CON heifers but the final pregnancy percentage was greater (P = 0.04) for SST vs. CON heifers. Thus, OMN supplementation decreased the intravaginal temperature of SST heifers but failed to improve their growth and reproduction, whereas the SST strategy improved body thermoregulation, growth, and final pregnancy percentage of heat-stressed Bos indicus-influenced beef heifers compared with a constant concentrate supplementation strategy.

In Bos taurus beef heifers, altering the timing of body weight (BW) growth pattern either reduced feed costs without decreasing reproduction or enhanced reproduction without increasing feed costs. Moreover, supplementation of OmniGen-AF (OMN, a patented immunomodulatory feed ingredient) decreased internal body temperature in dairy and beef B. taurus cattle, with variable impacts on growth and reproduction. Combining both nutritional strategies for Bos indicus-beef heifers developed under heat stress conditions of tropical and subtropical environments has not been reported in the literature yet and was the main objective of the present study. For 100 d before the breeding season, heifers received either a constant supplementation amount or stair-step (SST) supplementation strategy (50 d of low followed by 50 d of high supplement amount), with or without OMN inclusion. Overall, OMN supplementation alleviated the internal body temperature of heifers but did not improve their growth and reproduction, whereas the SST strategy increased BW gain and final pregnancy percentage of B. indicus-influenced beef heifers under heat stress conditions.

Growth, physiology, and coccidiosis infestation of suckling beef calves grazing warm-season grasses and offered creep-feeding supplementation with or without monensin.

This study evaluated the growth, physiology, and coccidiosis infestation of suckling beef calves provided monensin and grazing limpograss (Exp. 1) or bahiagrass (Exp. 2) pastures. Treatments were randomly assigned to pastures (4 pastures/treatment; 3 cow-calf pairs/pasture in Exp. 1; 4 pastures/treatment; 10 cow-calf pairs/pair of pastures in Exp. 2) and comprised of supplementation of 0.40 kg/d of soybean meal added or not with monensin (20 mg/kg of total DM intake) for 112 and 78 days before weaning in Exp. 1 and 2, respectively. In Exp. 1, supplement DM disappearance tended (P = 0.10) to be less for calves supplemented with vs. without monensin, but treatment × day and treatment effects were not observed (P ≥ 0.18) for herbage mass (HM), herbage allowance (HA), cow body condition score (BCS), calf average daily gain (ADG), calf plasma data, and fecal coccidia egg count. In Exp. 2, forage nutritive value, HM and HA, and cow BCS did not differ (P ≥ 0.43) between treatments. Supplemental monensin did not impact (P ≥ 0.78) plasma concentrations of insulin-like growth factor 1 but increased (P ≤ 0.05) calf overall ADG and plasma concentrations on day 78 and reduced plasma concentrations of urea nitrogen (PUN) on day 78 and fecal coccidia egg count on day 78 compared to calves provided no monensin supplementation. Hence, monensin supplementation successfully improved growth performance of creep-fed suckling beef calves, when herbage mass was not a limiting factor and coccidiosis infestation occurred.

Effects of monensin on growth performance of beef heifers consuming warm-season perennial grass and supplemented with sugarcane molasses.

The objective of this study was to evaluate the effects of monensin on performance of beef heifers fed warm-season forages. Brangus heifers (n = 24) were stratified by BW and BCS, and randomly assigned into 1 of 12 bahiagrass pastures (1.2 ha and 2 heifers/pasture). Heifers were offered 14 kg of sugarcane molasses and 3.5 kg of cottonseed meal weekly from day 0 to 84. Treatments were randomly assigned to pastures (6 pastures/treatment) and consisted of heifers supplemented with or without 200 mg/day of monensin. On d 85, heifers were allocated to individual drylot pens, provided free choice access to bermudagrass hay, and received their respective treatment for 10 d of adaptation and 11 d of data collection. Monensin did not impact (P ≥ 0.13) heifer BW, BCS, overall ADG, bahiagrass IVDOM, CP, herbage mass, and allowance. Supplement disappearance after 10 and 34 h of supplementation was greater for control vs. monensin heifers (P = 0.04) and tended to be greater for control vs. monensin heifers 24 h post-supplementation (P = 0.07). Plasma concentrations of glucose, IGF-1, and BUN (P ≥ 0.24) did not differ between treatments. From d 85 to 106, forage and total DM intake, in vivo DM digestibility, and heifer growth performance did not differ between treatments (P ≥ 0.12). Therefore, adding monensin to sugarcane molasses-based supplements decreased supplement consumption rate, but did not impact growth and blood parameters of heifers grazing warm-season grasses with limited nutritive value.