Non-lactating Cows Research Articles

Soil N2O flux and nitrification and denitrification gene responses to feed-induced differences in the composition of dairy cow faeces

Faeces from cows with different milk yield and non-lactating cows were applied to soil to investigate whether soil N2O efflux is related to feeding-induced differences in faecal microbiome and abundances of nitrification and denitrification genes. Fungal 18S-rRNA gene abundance was the highest in the faeces of the non-lactating group. The 18S-rRNA/ergosterol ratio showed a strong positive correlation with the 18S-rRNA/fungal glucosamine ratio. The milk-yield groups did not affect the gene abundances of bacterial 16S rRNA, AOB amoA, nirS and nosZ clade I, or the 16S-rRNA/muramic acid (MurN) ratio. In contrast, nirK gene abundance was generally the lowest in the high-yield group. The 16S-rRNA/MurN ratio showed a strong positive correlation with the 16S-rRNA/bacterial PLFA ratio. Cow faeces application to soil increased microbial biomass and ergosterol contents as well as the gene abundances of 18S-rRNA and nosZ clade I, compared with the non-amended control soil. Cumulative ΣCO2 efflux was roughly twice as high as the control, without differences between the faeces treatments. Cumulative ΣN2O efflux showed a 16-fold increase after applying high-yield cow faeces to soil, which was above the sevenfold increase in the non-lactating faeces treatment. The ΣN2O efflux from soil was positively related to faecal MurN and total PLFA concentration but also to soil nirK at day 14. The comparison of genome markers with cell wall (glucosamine) and cell membrane components (ergosterol) showed that the fungal cells were much larger in energy-rich faeces than in C-limited soil. A cow diet reduced in protein decreased the ΣN2O efflux from faeces amended soil.

Effects of feeding a live yeast on rumen fermentation and fiber degradability of tropical and subtropical forages.

The effect of live yeast Saccharomyces cerevisiae strain CNCM I-1077 (SC) on the ruminal degradability of different forages commonly found in dairy diets in South America was evaluated. We also assessed if SC supplementation interacts with forage group to affect ruminal fiber degradability. Four non-lactating rumen-cannulated Holstein cows were randomly assigned to two treatment sequences: Control-SC-Control or SC-Control-SC, in a switchback design, with three 30-day periods. Cows in the SC treatment were supplied with 1 × 1010 colony-forming units of yeast daily via rumen cannula. In situ degradability of dry matter (DM) and neutral detergent fiber (aNDF) was measured in 15 forages collected in South America. Forages were assigned to one of three groups: corn silages; tropical grasses (sugarcane silages and tropical grass silages); and temperate grasses and alfalfa (oat silages, ryegrass silages, alfalfa silage, and alfalfa hay). Cows supplemented with SC had higher (P=0.05) counts of yeasts and lower (P=0.03) concentration of lactate in rumen fluid. There was no interaction between forage group and yeast supplementation (P > 0.10) on in situ degradability. The SC increased DM (by 4.6%) and aNDF degradation (by 10.3%) at 24 h of incubation (P < 0.05). Metabolomics revealed that a chemical entity (C17 H29 N6 O3 , m/z 365.2284 [M + H]+ ) from the family of lipids and related molecules was suppressed in the rumen fluid of cows supplemented with SC. The SC supplementation improved DM and aNDF degradability regardless of the forage group. © 2021 Society of Chemical Industry.

Cotton Byproduct Use in Southeastern Beef Cattle Diets: Quality, Intake, and Changes in Feed Characteristics

Abstract Cotton is grown on over 4.5 million hectares in the southeastern U.S. annually, and byproducts of cotton production are utilized as feedstuffs in beef systems. Cotton breeding efforts and variety recommendations for crop production represent potential changes in cotton seed size, density, and quality, which may influence whole cottonseed feed quality characteristics. Also, cotton breeding to reduce gossypol concentration without compromising yield may improve value in ruminant diets. A recent feed intake trial demonstrated greater consumption of ultra-low gossypol seed compared with seed derived from a more widely planted cotton variety (0.072% vs 0.53% free gossypol, respectively) in growing steers (1.9 and 1.1 kg/hd/d, respectively). Historically, cottonseed is limited in bull diets due to the associated of decreased fertility in males due to gossypol. However, a recent study found that feeding up to 3.2 kg/hd/d over a 60-d period to developing beef bulls did not affect sperm quality. Heat damage commonly occurs in cottonseed during storage after the ginning process, but the feed value of heat damaged cottonseed is unknown. A recent study indicated that in situ dry matter (52.2 vs 69.2%) and N (78.1 vs 91.6%) disappearance decreased for heat damaged compared to normal cottonseed, respectively. Cotton gin trash remains a prevalent byproduct with traditionally limited use. Some gins have equipment for baling gin trash in 180-to-270 kg modules, which allow ease of access and transport of gin trash waste for cow-calf producers. Similar to gin trash, grazing cotton crop residue after harvest can decrease the amount of hay fed during the winter. A recent 3-yr study indicated a 2.5 hd/ha stocking rate of mature, non-lactating cows over a 30-d period decreased hay consumption by 65 %. By understanding the feed characteristics and management needed to utilize cotton byproducts, cattle operations can decrease feed cost while maintaining animal performance.

Interleukin-6 supplementation improves post-transfer embryonic and fetal development of in vitro-produced bovine embryos

The use of in vitro produced embryos in dairy and beef cattle has increased in recent years, but compromised post-transfer pregnancy success prevents producers from capturing all the benefits this technology can provide. This study explored whether supplementing interleukin-6 (IL6) during in vitro embryo development influences post-transfer development of the embryo-proper, fetus and placenta during early gestation in cattle. Slaughterhouse-derived cumulus oocyte complexes underwent IVM (day −1) and IVF (day 0). On day 5 post-fertilization, embryos were treated with either 0 (CONT) or 100 ng/mL recombinant bovine IL6. No difference in blastocyst formation was detected on day 7.5 post-fertilization, but an increase (P < 0.05) in inner cell mass cell numbers and tendency for increased (P = 0.08) trophectoderm cell numbers were detected in IL6-treated blastocysts. A subset of the blastocysts was loaded individually into transfer straws, and embryo transfer (ET) was completed using estrous cycle stage-matched, nonlactating commercial beef and dairy cows. A subset of cows from each group underwent timed artificial insemination (TAI). Pregnancy rates were similar among all three treatment groups at day 28 and 70. No differences in crown-rump length (CRL), crown nose length (CNL), abdominal diameter (AD), or placental fluid volume (PFV) were detected between TAI and ET-IL6 groups. Reductions (P < 0.05) in CRL and AD were detected at day 56 and a tendency for a reduction (P = 0.08) in PFV was detected on day 35 when comparing the ET-CONT group with the TAI group. Reductions (P < 0.05) in CRL and PFV on day 28 and CNL and AD on day 56 as well as a tendency for a reduction (P = 0.08) in PFV on day 35 were detected when contrasting ET-CONT with ET-IL6. Circulating plasma pregnancy-associated glycoprotein concentrations were similar among all treatment groups. In summary, IL6 treatment to IVP embryos before ET produced pregnancies that more closely resembled TAI-generated pregnancies than pregnancies generated using conventionally cultured embryos. These findings failed to find any adverse effects of IL6 supplementation on early development of the embryo-proper and fetus or on placental activity. Rather, these observations suggest that IL6 treatment may normalize the developmental trajectory of the embryo-proper and fetus for in vitro produced embryos.

Short-Term Variations of C18:1 Trans Fatty Acids in Plasma Lipoproteins and Ruminal Fermentation Parameters of Non-Lactating Cows Subjected to Ruminal Pulses of Oils.

Simple SummaryThe objective of this study was to evaluate short-term variations of trans fatty acids (TFA) in plasma lipoproteins and ruminal fermentation parameters of non-lactating cows subjected to ruminal pulses of vegetable oils. Over three-day periods, three non-lactating, non-pregnant Holstein cows received ruminal pulses of soybean oil, partially hydrogenated vegetable oil and a control with no added oil. In summary, results showed that for both oil treatments there was an accumulation of several C18:1 TFA in plasma and lipoproteins, especially on the third day of pulsing. Each C18:1 TFA responded differently to treatments over time.The objective of this study was to evaluate short-term variations of trans fatty acids (TFA) in plasma lipoproteins and ruminal fermentation parameters of non-lactating cows subjected to ruminal pulses of vegetable oils. Three non-lactating, non-pregnant Holstein cows, each with a ruminal cannula, were arranged in a 3 × 3 Latin square design with three-day pulsing periods and four-day washout intervals between treatments. Cows were treated with single ruminal pulses of: (1) control (skimmed milk (SM); 500 mL); (2) soybean oil (SO; 250 g/d in 500 mL of SM) and (3) partially-hydrogenated vegetable oil (PHVO; 250 g/d in 500 mL of SM). Time changes after infusion in TFA contents were only observed for plasma C18:1 trans-4, trans-5 and trans-12, and high-density lipoprotein fraction C18:1 trans-9. After ruminal pulses, concentration of acetate decreased linearly; molar concentrations of propionate and valerate increased linearly; molar concentrations of butyrate and isovalerate changed quadratically and were greater at 1 h than at other times. There was an accumulation of several C18:1 TFA in plasma and lipoproteins, especially on the third day of pulsing. Overall, naturally occurring C18:1 TFA isomers (produced during ruminal biohydrogenation of SO) and preformed TFA (supplied by PHVO) elicited differential TFA partitioning and transport in plasma and lipoproteins.

Lactation Associated Genes Revealed in Holstein Dairy Cows by Weighted Gene Co-Expression Network Analysis (WGCNA).

Simple SummaryWeighted gene coexpression network analysis (WGCNA) is a novel approach that can quickly analyze the relationships between genes and traits. In the past few years, studies on the gene expression changes of dairy cow mammary glands were only based on transcriptome comparisons between two lactation stages. Few studies focused on the relationships between gene expression of the dairy mammary gland and lactation stage or milk composition in a lactation cycle. In this study, we detected milk yield and composition in a lactation cycle. For the first time, we constructed a gene coexpression network using WGCNA on the basis of 18 gene expression profiles during six stages of a lactation cycle by transcriptome sequencing, generating 10 specific modules. Genes in each module were performed with gene ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. Module–trait relationship analysis showed a series of potential candidates related to milk yield and composition. The current study provides an important theoretical basis for the further molecular breeding of dairy cows. Weighted gene coexpression network analysis (WGCNA) is a novel approach that can quickly analyze the relationships between genes and traits. In this study, the milk yield, lactose, fat, and protein of Holstein dairy cows were detected in a lactation cycle. Meanwhile, a total of 18 gene expression profiles were detected using mammary glands from six lactation stages (day 7 to calving, −7 d; day 30 post-calving, 30 d; day 90 post-calving, 90 d; day 180 post-calving, 180 d; day 270 post-calving, 270 d; day 315 post-calving, 315 d). On the basis of the 18 profiles, WGCNA identified for the first time 10 significant modules that may be related to lactation stage, milk yield, and the main milk composition content. Genes in the 10 significant modules were examined with gene ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. The results revealed that the galactose metabolism pathway was a potential candidate for milk yield and milk lactose synthesis. In −7 d, ion transportation was more frequent and cell proliferation related terms became active. In late lactation, the suppressor of cytokine signaling 3 (SOCS3) might play a role in apoptosis. The sphingolipid signaling pathway was a potential candidate for milk fat synthesis. Dairy cows at 315 d were in a period of cell proliferation. Another notable phenomenon was that nonlactating dairy cows had a more regular circadian rhythm after a cycle of lactation. The results provide an important theoretical basis for the further molecular breeding of dairy cows.

Physiological Comparison of Some Serum Biochemistry between Lactating and Non-Lactating Dairy Cows in Selected Dairy Farms of Dhaka District of Bangladesh

The present study was carried out to investigate the physiological comparison of some serum biochemistry between lactating and non-lactating dairy cows in selected dairy farms of Dhaka district of Bangladesh. The aim of the current study was to evaluate the serum parameters like glucose, total protein, total cholesterol, calcium and phosphorus concentration and these parameters were measured by the serum analyzer for lactating (n=50) and non-lactating (n=50) dairy cattle which were selected from various selected dairy farms of Dhaka district. The results (mean ± standard deviation) of the study showed that among the serum biochemical parameters total protein (84.2±1.18 gm/l) and total cholesterol (156.36± 3.41 mg/dl) level in non-lactating cows were higher than the value of lactating cows as (80.14±2.31 gm/l) and (138.21± 1.21 mg/dl). On the other hand, serum glucose, calcium and phosphorus level in lactating cows (68.12± 2.34 mg/dl), (12.06±3.21 mg/dl) and (8.30±0.20 mg/dl) respectively were found higher than the non-lactating cows (60.32 ±1.42 mg/dl), (10.48±5.60 mg/dl) and (6.31 ±0.12 mg/dl). In case of parity-wise biochemical parameters were insignificant variation was found. It may be concluded that biochemical parameters variation present between lactating cow and non-lactating cow is important for interpretation of laboratory data and also for physiological diagnosis.

Metabolism of Zearalenone in the Rumen of Dairy Cows with and without Application of a Zearalenone-Degrading Enzyme.

The mycotoxin zearalenone (ZEN) is a frequent contaminant of animal feed and is well known for its estrogenic effects in animals. Cattle are considered less sensitive to ZEN than pigs. However, ZEN has previously been shown to be converted to the highly estrogenic metabolite α-zearalenol (α-ZEL) in rumen fluid in vitro. Here, we investigate the metabolism of ZEN in the reticulorumen of dairy cows. To this end, rumen-fistulated non-lactating Holstein Friesian cows (n = 4) received a one-time oral dose of ZEN (5 mg ZEN in 500 g concentrate feed) and the concentrations of ZEN and ZEN metabolites were measured in free rumen liquid from three reticulorumen locations (reticulum, ventral sac and dorsal mat layer) during a 34-h period. In all three locations, α-ZEL was the predominant ZEN metabolite and β-zearalenol (β-ZEL) was detected in lower concentrations. ZEN, α-ZEL and β-ZEL were eliminated from the ventral sac and reticulum within 34 h, yet low concentrations of ZEN and α-ZEL were still detected in the dorsal mat 34 h after ZEN administration. In a second step, we investigated the efficacy of the enzyme zearalenone hydrolase ZenA (EC 3.1.1.-, commercial name ZENzyme®, BIOMIN Holding GmbH, Getzersdorf, Austria) to degrade ZEN to the non-estrogenic metabolite hydrolyzed zearalenone (HZEN) in the reticulorumen in vitro and in vivo. ZenA showed a high ZEN-degrading activity in rumen fluid in vitro. When ZenA was added to ZEN-contaminated concentrate fed to rumen-fistulated cows (n = 4), concentrations of ZEN, α-ZEL and β-ZEL were significantly reduced in all three reticulorumen compartments compared to administration of ZEN-contaminated concentrate without ZenA. Upon ZenA administration, degradation products HZEN and decarboxylated HZEN were detected in the reticulorumen. In conclusion, endogenous metabolization of ZEN in the reticulorumen increases its estrogenic potency due to the formation of α-ZEL. Our results suggest that application of zearalenone hydrolase ZenA as a feed additive may be a promising strategy to counteract estrogenic effects of ZEN in cattle.

The effect of sodium butyrate supplementation on ruminal and fecal pH and serum lipopolysaccharide-binding protein after ruminal acidosis challenge in nonlactating cows.

The objective of this study was to evaluate effects of sodium-butyrate supplementation on gastrointestinal function and the inflammatory response to ruminal acidosis (RA) challenge in cows. Four nonlactating cows with a rumen cannula were assigned to two treatments in a crossover design. Treatments were ruminal administration of sodium-butyrate (BUT) or control (CON). Sodium-butyrate was provided as Gustor BP70 and administered at a butyrate dose of 0.04% per kg body weight. The CON premix was made by replacing sodium-butyrate with wheat bran. Experimental periods were 28 days long with 21-day washout period separating the treatments. On Day 25 of each period, corn starch was ruminally administered at 0.7% per kg body weight as RA challenge. After RA challenge, ruminal pH was lower, and endotoxin concentration was higher for cows provided with BUT than those with CON, but the increase in fecal starch and the decrease in fecal pH were attenuated by BUT. The effect of butyrate supplementation on serum lipopolysaccharide-binding protein after RA challenge was not found. From these findings, butyrate supplementation mitigated rectal acidosis by reducing the flux of fermentable carbohydrate into the large intestine. An anti-inflammatory effect of butyrate was not observed, possibly due to lower pH and higher endotoxin concentration in the rumen.

117 Effect of length of insertion of a progesterone device on follicular diameter, time of ovulation, and pregnancy rates in Bos indicus cows treated with an oestradiol/progesterone-based protocol with a prolonged proestrus

Three experiments were designed to evaluate the effect of the length of insertion of a intravaginal progesterone (P4) device on follicular and corpus luteum (CL) diameter, time of ovulation, and pregnancy rates following fixed-time AI (P/FTAI) in Bos indicus cows treated with an oestradiol/P4-based treatment with a lengthened proestrus, named J-Synch. Multiparous suckled Bos indicus beef cows that were 35 to 60 days postpartum were used in Experiments 1 and 2, whereas non-lactating cows were used in Experiment 3. All cows had a CL or a follicle of at least 8mm in diameter and a body condition score between 2.5 and 4 (1 to 5 scale) at the time of treatment. On Day 0, all cows received 2mg of oestradiol benzoate (EB; Sincrodiol, Ourofino, Brazil) and a previously used intravaginal device (1g of P4; Sincrogest, Ourofino). The P4 device was removed on Day 6 in the J-Synch 6-day group and on Day 7 in the J-Synch 7-day and Control groups. All cows received 500µg of cloprostenol (Sincrocio, Ourofino) and 400IU of equine chorionic gonadotrophin (SincroeCG, Ourofino) at the time of P4 device removal, and cows in the Control group also received 0.5mg of oestradiol cypionate (ECP, SincroCP, Ourofino) at the same time. In Experiment 1, cows (n=20 per group) were examined every 12h, from P4 device removal to determine the time of ovulation and 7 days after ovulation to measure the CL. In Experiment 2, all cows (n=200 per group) were tail-painted for oestrous detection. Cows with=50% of the tail-paint rubbed-off by 72h (J-Synch groups) or 48h (Control group) after P4 device removal, were FTAI at that time. Cows not designated as showing oestrus at that time received 10µg Buserelin (GnRH, Sincroforte, Ourofino) and were FTAI 8h later. In Experiment 3, P/FTAI was compared in cows that received the J-Synch 7-day treatment (n=265) or the 7-day Control treatment (n=250). Data were analysed using the GLM mixed procedure (InfoStat). In Experiment 1, the diameter of the ovulatory follicle was larger (P&amp;lt;0.05) and the interval to ovulation was longer (P&amp;lt;0.05) in the J-Synch groups (J-Synch 7 d: 16.4±0.2mm and 86.0±3.0 h; J-Synch 6 d:15.5±0.3mm and 83.0±4.0h) than in the Control group (13.8±0.2mm and 64.0±3.0h). Furthermore, CL diameter was greater (P&amp;lt;0.05) in the J-Synch 7-day group (21.9±0.8mm) than in the J-Synch 6-day (18.7±0.8mm) and Control (16.8±0.9mm) groups. In Experiment 2, P/FTAI was higher (P&amp;lt;0.05) in the J-Synch 7-day group (116/200; 58.0%) than in the J-Synch 6-day (93/200; 46.5%) and Control (98/200; 49.0%) groups. In Experiment 3, P/FTAI was higher (P&amp;lt;0.05) in the J-Synch 7-day group (161/265; 60.7%) than in the Control group (124/250; 49.6%). In conclusion, delaying the removal of the P4 device by 1 day (i.e. Day 7 vs. Day 6) in the J-Synch protocol and lengthening the proestrous period (i.e. J-Synch 7-day vs. 7-day Control) resulted in higher P/FTAI in Bos indicus cows.

37 Effect of invivo and invitro heat stress on DNA methylation and DNA hydroxymethylation of bovine oocytes and embryos

Reduced reproductive performance is one of the main effects caused by heat stress in cattle. Its negative effects have been observed at the transcriptional, biochemical, morphological, and developmental levels on the oocyte and embryo. There are no studies evaluating the effect of heat stress on the epigenetic profile of bovine oocytes and early embryos. The objective of this study was to evaluate the effect of invivo and invitro heat stress on DNA methylation and DNA hydroxymethylation in bovine MII oocytes, pronuclear, and 2- to 4-cell stage embryos. Seven Bos taurus crossbred nonpregnant, non-lactating beef cows located in Saint Gabriel, Louisiana (30.269746, −91.103357) were used for oocyte collection. Dominant follicle removal was performed 5 days before oocyte collection. Cumulus–oocyte complexes were collected by ovum pickup from follicles &amp;gt;2mm. Samples were collected during the summer (August) and winter (February) (5 collections each). Three treatments were utilised: invivo heat stress (August samples), invitro heat stress (February samples subjected to 41°C during the first 12h of IVM and then to 38.5°C during the next 12h of IVM), and control (February samples IVM at 38.5°C). All oocytes collected per treatment were assigned to 3 developmental stages: MII oocytes, pronuclear, and 2- to 4-cell stage embryos. Embryos were obtained through standard IVF. DNA methylation and DNA hydroxymethylation was assessed by fluorescence immunohistochemistry utilising primary antibodies against 5′-methylcytosine and 5′-hydromethylcytosine and secondary antibodies Alexa Fluor 488 and Alexa Fluor 546, respectively. Samples were visualised with a fluorescence deconvolution microscope, and immunofluorescence data were expressed as corrected relative fluorescence per nucleus. Results were analysed by the Type III test of fixed effects and Tukey media separation utilising the Proc Glimmix of SAS 9.4 (P&amp;lt;0.05). Maturation rate, 2 pronuclei (2PN) rate, cleavage rate, and 2- to 4-cell rate were analysed by Chi-square. There was no difference in maturation rate (88.19±7.57, 82.91±5.18, 94.51±5.04; P=0.2516), 2PN rate (79.34±10.23, 93.75±7.21, 81.74±12.53; P=0.1757), cleavage rate (79.26±2.69, 70.65±7.22, 81.85±16.65; P=0.2388) and 2- to 4-cell rate (69.38±7.83, 81.25±10.34, 61.11±11.69; P=0.4392) between invivo and invitro heat stress compared with control, respectively. No difference was found in DNA methylation (P=0.0537) or DNA hydroxymethylation (P=0.4632) between treatments in MII oocytes. When evaluating the paternal and maternal pronuclei, there was no difference in DNA methylation (P=0.9766; P=0.1954, respectively) or DNA hydroxymethylation (P=0.6440; P=0.1932, respectively) between invivo and invitro heat stress compared with control. Similarly, there was no difference in DNA methylation (P=0.0903) or DNA hydroxymethylation (P=0.2452) between treatments when evaluating the 2- to 4-cell embryos. In conclusion, we detected no effect of invivo or invitro heat stress on MII oocytes and early embryos when evaluating global DNA methylation and hydroxymethylation through fluorescence immunohistochemistry.

Effects of soybean meal supplementation on ruminal kinetics of feed particle size reduction and passage in dairy cows fed rice straw.

Six ruminal-cannulated nonlactating Holstein Friesian cows (mean body weight:660 ± 42.9 kg) were used to investigate the effect of soybean meal (SBM) supplementation on voluntary rice straw (RS) intake, feed particle size reduction, and passage kinetics in the rumen. They were allocated to two dietary treatments: RS alone or RS supplemented with SBM. Voluntary dry matter intake of RS and total tract fiber digestibility was increased by SBM supplementation (p < 0.05). Supplementation with SBM decreased rumination time per dietary dry matter (DM) and neutral detergent fiber (NDFom) intake (p < 0.01). Particle size distribution in the rumen and total ruminal NDFom digesta weights were not affected by SBM supplementation. However, the disappearance rates of total digesta and large and small particles from the rumen were increased by SBM supplementation (p < 0.01). Moreover, SBM supplementation increased the rate of size reduction in ruminal particles (p < 0.05). In situ disappearance of DM and NDFom of RS in the rumen was greater in SBM-supplemented cows than in nonsupplemented cows (p < 0.05). This study clearly showed that increased ruminal RS particle size reduction, passage, and fermentation due to SBM supplementation accelerated the RS particle clearance from the rumen and resulted in increased voluntary RS intake of dairy cows.

Digestive, fermentative, and physical properties of pineapple residue as a feed for cattle.

The intake, digestion, and ruminal fermentation properties; the antioxidative activity; and the physical effectiveness of pineapple residue (PR) from the cut-fruit industry as a feed for cattle were investigated. Four nonlactating Holstein cows were fed a basal diet and diets with 1.4- and 3.6-kg dry matter (DM)/day of PR (low-PR and high-PR diets, respectively). The DM digestibility and total digestible nutrients were 71% and 70%, respectively. Ruminal pH, volatile fatty acids, and ammonia-N did not differ among the diets. The numbers of total viable, amylolytic, cellulolytic, and methanogenic bacteria and protozoa, and microbial protein synthesis in the rumen also did not differ significantly. Blood triglyceride, nonesterified fatty acids, urea nitrogen, and aspartate transaminase were lower in the high-PR diet. Feeding PR did not affect blood malondialdehyde, although PR has a higher antioxidative value than other commonly used feeds. The particle distribution of PR satisfied the recommended range for haylage. The chewing time for ingestion and rumination did not change with PR content, and the roughage value index of PR was 57-min/kg DM. These results suggest that PR has good intake and digestion properties and satisfactory physical effectiveness. Even a high-PR-content feed unlikely induces the risk of ruminal acidosis.

48 Timing of luteolysis and conceptus expulsion after induced pregnancy loss at three different timepoints after maternal recognition of pregnancy in cattle

Results from previous research indicate that induced pregnancy loss (IPL) on Day 36 of gestation in cattle resulted in luteolysis by gestation Day ∼45. The aim of this study was to test the hypothesis that IPL at 25, 35, or 55 days of gestation will result in luteolysis and whether the interval between IPL and luteolysis is positively associated with days of gestation at time of treatment. Pregnant non-lactating beef cows were randomly assigned to undergo IPL, consisting of an intrauterine infusion of 120mL of hypertonic saline (7.2%), at Day 25 (IPL25, n=15), Day 35 (IPL35, n=14), or Day 55 (IPL55, n=14). Corpus luteum (CL) volume and embryo/fetal viability were evaluated by transrectal B-mode ultrasonography daily for 19 days following treatment and every other day subsequently until luteolysis was identified or gestation Day 91. Blood flow through the CL was evaluated using colour-Doppler ultrasonography, and luteolysis was defined as the day when &amp;lt;25% of the CL was represented with colour pixels. Conceptus expulsion was defined as the absence of a conceptus and fluid accumulation in the uterus was &amp;lt;25%. Data were analysed using Proc Mixed in SAS (v9.4; SAS Institute Inc.). Cessation of conceptus heartbeat occurred in all animals within 24h of administration of treatment. Day of luteolysis occurred earlier (P&amp;lt;0.01) in IPL25 (5.3±0.4d) than IPL55 (8.9±1.4d) cows, and luteolysis tended (P=0.07) to occur earlier in IPL35 (6.6±0.6d) than IPL55 cows; however, values for this variable in IPL25 and IPL35 cows were similar (P&amp;gt;0.2). The variance in timing of luteolysis was greater for IPL55 than for IPL35 cows, whereas variance for IPL35 was greater than that for IPL25 (P&amp;lt;0.05) cows. Conceptus expulsion was detected earlier (P&amp;lt;0.01) in IPL25 (Day 4.2±0.4) and IPL35 (Day 5.8±0.5) than IPL55 (Day 10.4±1.4) cows; however, IPL25 and IPL35 cows had similar (P&amp;gt;0.1) values for this variable. Values for luteolysis and conceptus expulsion were correlated in IPL35 (r=0.84; P&amp;lt;0.01) and IPL55 (r=0.88; P&amp;lt;0.01) cows, whereas there was no correlation among values for these variables in IPL25 (r=0.31; P=0.3) cows. There were effects of treatment (P&amp;lt;0.01), time (P&amp;lt;0.01), and treatment by time interaction (P&amp;lt;0.01) on CL volume. Volume of the CL was less (P&amp;lt;0.04) in IPL25-treated cows by treatment day 5 compared with that in IPL55-treated cows. Additionally, CL volume was less (P&amp;lt;0.03) in IPL25 by treatment day 6 than in IPL35 cows, and IPL35 cows had a lesser (P&amp;lt;0.01) CL volume starting on treatment day 10 than IPL55 cows. Induction of pregnancy loss at different times of gestation resulted in luteolysis; however, the interval between treatment and luteolysis tended to increase as gestation days increased. Furthermore, the variability in the timing of luteolysis increased as gestation days increased. Results from the present study support the working hypothesis of presence of a continuous mechanism for CL maintenance during pregnancy beyond the classical maternal recognition period in cattle.

Microbial community structure of the bovine rumen as affected by feeding cashew nut shell liquid, a methane-inhibiting and propionate-enhancing agent.

The effect of cashew nut shell liquid (CNSL) feeding on bacterial and archaeal community of the bovine rumen was investigated by analyzing clone libraries targeting 16S rRNA genes, methyl-coenzyme reductase A-encoding genes (mcrA), and their respective transcripts. Rumen samples were collected from three non-lactating cows fed on a hay and concentrate diet with or without CNSL supplementation. DNA and complementary DNA (cDNA) libraries were generated for investigating rumen microbial communities. MiSeq analysis also was performed to understand more comprehensively the changes in the microbial community structures. Following CNSL supplementation, the number of operational taxonomical unit (OTU) and diversity indices of bacterial and archaeal community were decreased. Bacterial OTUs belonging to Proteobacteria, including Succinivibrio, occurred at a higher frequency with CNSL feeding, especially in cDNA libraries. The methanogenic archaeal community became dominated by Methanomicrobium. A bacterial community shift also was observed in the MiSeq data, indicating that CNSL increased the proportion of Succinivibrio and other genera known to be involved in propionate production. Methanogenic archaeal community shifts to increase Methanoplanus and to decrease Methanobrevibacter also were observed. Together, these results imply the occurrence of significant changes in rumen communities, not only for bacteria but also for methanogens, following CNSL feeding.

Effect of expression of estrus and treatment with GnRH on pregnancies per AI in beef cattle synchronized with an estradiol/progesterone-based protocol

Three experiments evaluated the effects of expression of estrus and gonadotropin releasing hormone (GnRH) treatment on pregnancies per AI (P/AI) in beef cattle that were treated with an estradiol/progesterone (P4)-based protocol for fixed-time artificial insemination (FTAI). In Experiment 1, 20 non-lactating beef cows were treated with 2 mg estradiol benzoate (EB) and an intravaginal device containing 0.5 g of P4. Seven days later, P4 devices were removed and all cows received prostaglandin F2 alpha (PGF2α) and 0.5 mg estradiol cypionate (ECP). Estrus was detected using tail paint and cows that did not show estrus by 48 h after P4 device removal were randomized to receive GnRH or no treatment. Ovulation, as determined by ultrasonography, occurred earlier in cows that showed estrus (68.0 ± 2.5 h) than in cows that did not (82.0 ± 2.1 h, P < 0.05). Furthermore, cows that received GnRH ovulated earlier (78.0 ± 2.6 h) than those that did not (86.0 ± 2.0, P < 0.05). Experiment 2 determined whether expression of estrus and the administration of GnRH to animals that did not show estrus increased P/AI. Non-lactating beef cows and heifers (n = 1356) were treated as in Experiment 1 (P4 device removal, PGF2α and ECP administration on Day 7) or extended until Day 8. All animals in estrus by 48 h after P4 device removal were inseminated and those not showing estrus received GnRH or no treatment and were FTAI 8 h later (i.e., at 56 h). P/AI were greater (P < 0.01) in animals that were observed in estrus by 48 h (56.4%) than in those that did not show estrus (46.5%). Likewise, animals that did not show estrus but were treated with GnRH had greater P/AI (53.8%, P < 0.04) than those that did not receive GnRH (37.9%). Experiment 3 was designed to determine the effect of delaying GnRH treatment to the time of FTAI (at 56 h) in cows not showing estrus by 48 h after P4 device removal. Suckled beef cows (n = 969) were treated as in Experiment 1, except that all cows also received 400 IU of eCG at the time of P4 device removal on Day 7. Cows that showed estrus by 48 h or 56 h had greater P/AI (62.3%, P < 0.05) than those did not show estrus (51.5%). Furthermore, when cows that did not show estrus by 48 h were analyzed separately, P/AI were greater (P < 0.05) in those that received GnRH at 48 h and were FTAI by 56 h (64.9%) than in those that received GnRH concurrent with FTAI by 56 h after device removal (54.6%). In summary, expression of estrus was associated with earlier ovulations and resulted in greater P/AI in cows and heifers treated with an estradiol/P4-based protocol for FTAI. Furthermore, GnRH treatment in animals that did not show estrus hastened the time of ovulation and increased P/AI.

Beta-Carotene concentration in blood serum of cows from herds with impaired fertility

Beta-Carotene concentration in blood serum of cows from herds with impaired fertility

281 Techniques to estimate colostrum quality and the effects of cow age and pre-partum supplement intake levels on colostrum quality and serum IgG levels

Abstract Our study was conducted to evaluate the influence of cow age and supplement intake level during gestation on the quality of colostrum at calving, serum IgG levels of the cow at parturition, and serum IgG levels of the calf 3 days post-partum using two on-farm refractometer methods. Forty-five non-lactating multiparous Angus cows were selected from a contemporary group of 300 cows winter grazing northern mixed grass prairie rangelands with free choice protein supplement. Specifically, 15 first service bred cows were selected for each of the following treatment groups: 1) low supplement intake (&amp;gt; -0.75 SD); 2) average supplement intake (± 0.50 SD); 3) high supplement intake (&amp;gt; +0.75 SD). Supplement intakes were measured using 8 feeding stations in a SmartFeed Pro self-feeder system (C-Lock Inc., Rapid City, SD) and measurements were obtained from d 164 to 215 of gestation. Cows were further divided by age comparing young (4, 5, and 6 yr) to old (7 and 8 yr). Cow age did not interact with supplement intake for any of the colostrum or blood serum measurements (P ≥ 0.29). In addition, cow age and supplement intake did not influence colostrum Brix %, calf serum total protein taken 3 d post-partum or cow serum total protein taken at birth (P ≥ 0.14). The optical refractometer was found to be a good alternative to the more expensive digital refractometer. When regressing values of the two techniques, they were observed to be correlated (P &amp;lt; 0.01; R = .96). In summary, cow age and supplement intake levels of mature cows during the mid to late stages of gestation did not influence colostrum quality at birth. The lack of colostrum quality differences was likely due to the moderate to good condition of the cows and adequate nutrition 90 d prior to parturition.

197 Effect of a SARA challenge diet on chewing behavior and rumino-reticular short chain fatty acid concentrations in dairy cows

Abstract Intensive dairy production systems encourage feeding of high-concentrate diets to increase milk production efficiency. However, there is limited information regarding the effect of a SARA challenge diet on chewing behavior and rumino-reticular short chain fatty acid (SCFA) concentration. The objective of this study was to evaluate chewing activity and SCFA production in the rumen and reticulum, using nine ruminally cannulated non-lactating Holstein cows. Preceding the trial, cows were transitioned from 100% forage to 65% DM concentrate over eight days. Trial day 1 began once cows reached 65% DM concentrate and monitoring during 23 days. RumiWatch halters were used to monitor chewing activity. SCFA analysis was conducted on rumen and reticulum fluid collected 4 hours after feeding using gas chromatography. Data were analyzed with SAS, with the fixed effect of days and cow as random effect. There was an increase in DM intake during the first four hours after feeding: 1.97 and 2.25 ± 0.12 kg for day 1 and 23, respectively (P &amp;lt; 0.05). There was no difference in rumination time (P = 0.16) with 29 ± 8.5 minutes during the first four hours of feeding. However, chewing index (P = 0.08) tended to decrease from 36.7 to 29.4 ± 4.4 minutes of chewing/kg of DM for day 1 and 23, respectively. Moreover, on day 1, propionate increased from 19.9 ± 1.02 to 20.1 ± 1.02% and from 24.04 ± 0.93 to 25.4 ± 1.02% compared to day 23 for rumen and reticulum, respectively (P &amp;lt; 0.05). In addition, from day 1 to day 23, the rumen and reticulum acetate/propionate ratio declined from 3.2 ± 0.15 and 3.1 ± 0.1, to 2.5 ± 0.15, respectively, and reticulum SCFA decreased from 87 to 67 µmol/g, respectively. Overall, there was no effect of the 23-day SARA challenge diet on chewing activity. However, there was a reduction of SCFA concentration in reticulum, which may be due to enhanced SCFA absorption or increased feed bolus neutralizing capacity.

PSIV-23 Variations in chewing behavior and rumino-reticular pH in dairy cows during gradual adaptation to a high-grain diet

Abstract Physical effective fiber in the diet promotes chewing, contributing to the regulation of ruminal pH through saliva production, which leads to rumen health. However, lower dietary fiber content in high-grain diets may reduce rumination time and compromise ruminal pH regulation. The objective of this experiment was to evaluate rumination behavior and rumino-reticular pH variations during an 8-day adaptation to a 65% concentrate diet. For this study nine ruminally cannulated non-lactating Holstein cows were used. Prior to the initiation of the adaptation, cows were transitioned from a forage-only grass silage diet to a 65% DM concentrate diet over eight days. Rumination was monitored using RumiWatch halters (RumiWacthSystem ITIN+HOCH). Rumino-reticular pH was measured using eCow indwelling pH systems in five of nine cows recording data every 15 minutes. Data were analysed with SAS, the statistical model included day as fixed effect and cow was considered as random effect. Adaptation days had an effect (P &amp;lt; 0.01) on rumination time, number of rumination chews per minute, and mean daily (rumino-reticular) pH. Especially, rumination time decreased from 439 to 327±62.8 minutes per day from day 1 to 8, respectively. Concomitantly, rumination chews per minute decreased from 68.8 to 65.6±2.06, and mean daily pH decreased from 6.54 and 6.26±0.07, respectively. Nevertheless, daily dry matter intake (P = 0.23) and eating time (P = 0.37) were not affected during the adaptation period. In conclusion, adaptation to a high-grain diet and the associated decrease in physically effective fiber gradually reduced chewing activity and ruminal/reticular pH. However, compared to the forage-only diet, significant reduction in rumination time was only noted at the 65% concentrate level.