Pregnant Beef Cows Research Articles

PSLBI-12 Screening and isolation of Fusobacterium necrophorum and Fusobacterium varium from seminal, and vagino-uterine microbiota of healthy cattle and sheep

Abstract Fusobacteria necrophorum is an important opportunistic bacterial pathogen associated with liver abscesses, foot rot, necrotic laryngitis and endometritis in both dairy and beef cattle. Recently, we identified F. necrophorum as one of the taxa in the uterine microbiota that are positively associated with pregnancy outcome in beef cows, and that Fusobacterium was identified as the most dominant genus in the bovine seminal microbiota. These findings indicate that Fusobacterium spp. may have a role in reproductive health and cattle fertility. Our objectives were to detect and isolate the F. necrophorum subsp necrophorum (FNN), F. necrophorum subsp. funduliforme (FNF) and F. varium (FV) in seminal, vaginal and uterine microbial ecosystems as well as fetal samples by culture and real-time PCR (qPCR) methods. The qPCR was performed on the DNA (n = 215) extracted from bull semen (n = 37), ram semen (n = 100), and vaginal (n = 25) and uterine swabs (n = 32), caruncles (n = 9), allantoic fluid (n = 6), and amniotic fluid (n = 6) from pregnant beef cows. The qPCR targeted the hgdA gene, and leukotoxin promoter regions (lktA-n and lktA-f) to detect and quantify FV, FNN and FNF, respectively. Cryopreserved samples (n = 174; 57 bull semen, 10 ram semen, 38 vaginal, and 47 uterine swabs) were cultured to detect and isolate FNN, FBF and FV by direct plating and after culturing in anaerobic peptone-yeast extract broth containing sodium lactate broth with josamycin, vancomycin and norfloxacin for selective enrichment of FN and FV. Also, 28 samples of 6-mo-old bovine fetuses caruncles, allantoic and amniotic fluids, and intestinal tissue) were screened for Fusobacterium species. By qPCR, FNF was detected in 75.7% of bull semen, and 8.0% of vaginal swabs as well as 33.3% of both allantoic fluid and caruncles, but was undetected in ram semen, uterine swabs, and amniotic fluids. Subspecies necrophorum was identified in 37.8% of bull semen, 3% of ram semen, 8.0% of vaginal and 15.6% of uterine 55.6 % of caruncles, 50% of allantoic fluid samples, but was not detected in amniotic fluid samples. Meanwhile FV was only detected in vaginal, uterine swabs and caruncles at 4%, 6.3%, and 11.1%, respectively. The culture method detected FNF in 63.2% of bull semen and 5.3% of vaginal samples, while FNN was identified in 1.8% of bull semen and 2.1% of uterine samples. F. varium was not isolated from any of the samples. Overall, FNF was the most prevalent subspecies present in the seminal microbiome of bulls. Identification of FNN subspecies and FV in seminal, vaginal, and uterine microbiota of healthy cattle, as well as in healthy calf fetus-associated samples suggests potential transfer from bulls to cows and then on to offspring, and potential involvement of the Fusobacterium spp. in cattle fertility.

PSVI-22 Effects of supplementation of beef cows during gestation on progeny backgrounding frame size and performance

Abstract The implications of supplementation during gestation on growth and efficiency of offspring have gained interest worldwide. The hypothesis of this study was that supplementation of cows during gestation results in favorable progeny growth and nutrient utilization. Our objectives were to assess the impacts of providing supplementation to pregnant beef cows during the dry grazing period on progeny backgrounding performance. During a 2-yr period, Tabapuã cows (n = 36) were managed on Brachiaria pastures, which were assigned to 1 of 3 treatments as follows: no application of N on pasture and cows supplemented with mineral mix (CON), application of 165 kg of Nּ ha-1ּ yr-1 and cows supplemented with a commercial product containing 40% of CP, macro and micro minerals, and vitamins (SUP), and application of 165 kg of Nּ ha-1ּ yr-1 and cows supplemented with grass silage (GS). At the beginning of the dry period, the commercial supplement and silage were fed for 140 d (from 116 ± 27 to 256 ± 27 d of gestation). The mineral mix was offered all year round. Bull (n = 18 in yr 1 and 12 in yr 2) and heifer progeny (n = 13 in yr 1 and 17 in yr 2) were weaned with average age of 203 ± 18 d in yr 1 and 229 ± 15 d in yr 2. After weaning, progeny were weighed and allocated in individual pens and adapted to a growing diet over 90 in yr 1 and 89 d in yr 2. For both years, rations were formulated to provide 0.9 kg/d (Dietary NEm = 1.68 Mcal/kg and dietary Neg = 1.07 Mcal/kg, on average). The PROC MIXED procedure of SAS was used to analyze all variables. The statistical model included supplementation program as a fixed effect and sex (male or female) as a random variable. Initial BW, weaning age, estimated progeny difference, and d on feed were included as covariates. No differences were obtained for initial BW, final BW, ADG, DM intake, and G:F. Frame size (e.g., heart girth, hip height) was also unaffected by dam supplementation. Overall, supplementing pregnant beef cows, during the dry grazing period, with a commercial supplement or silage does not affect progeny performance during backgrounding.

255 Awardee Talk: Nutritional management to optimize cow-calf production in Southeast

Abstract Nearly one-half of beef cows in the United States are located in southern states where cow-calf operations predominate. Grazing management in cow-calf systems can be affected by environmental and seasonal conditions, often leading to nutrient deficiency, particularly during late gestation of beef females. Maternal nutrition during the last trimester of gestation can influence offspring development and health, and can be explored to optimize maternal and progeny performance. The objective of this presentation is to share nutritional and management strategies for pregnant beef cows and their long-term effects on offspring growth and physiology. Study 1 investigated the effects of timing of maternal protein supplementation during all last trimester of gestation (LATE84), only the first 42 d of last trimester of gestation (LATE42), or no prepartum supplementation (NOSUP) on offspring pre- and post-weaning performance. At weaning, LATE84 calves were the heaviest, followed by LATE42, and NOSUP (P ≤ 0.05). Steer serum parainfluenza-3 titers were greater (P = 0.03) for LATE42 vs. NOSUP and tended to be greater for LATE84 (P = 0.10) vs. NOSUP steers. Marbling and the proportion of steers grading choice were greater (P ≤ 0.04) for LATE42 vs. NOSUP, and intermediate for LATE84. Study 2 evaluated the effects of frequency of maternal protein supplementation on offspring pre-weaning growth. Cows received the same weekly amount of supplement (7 kg·cow⁻¹·wk⁻¹) but with different frequencies: once a week (1X), three times per week (3X), every day (7X), or no prepartum supplementation (NOSUP) during the last 80 d of gestation. At weaning, calves born from 7X cows were the heaviest (P ≤ 0.05), followed by 3X and 1X, which did not differ between them (P = 0.54), and NOSUP calves were the lightest (P ≤ 0.05). Study 3 evaluated the use of monensin supplementation during the last 77 d of gestation and its impacts on offspring performance. Treatments consisted of no prepartum supplementation (NOSUP), supplementation of dried distillers grains at 1 kg·cow⁻¹·d⁻¹ added with 0 (SUP) or 200 mg/d of monensin (SUPMO). At weaning, SUPMO calves were the heaviest (P ≤ 0.05), SUP intermediate, and NOSUP were the lightest. Experiment 4 consisted of pregnant heifers receiving the supplementation of 1 kg/d of soybean hulls dry matter added (BAC) or not (CON) with a Bacillus-based DFM mixture during late gestation (d 0 to 139) and early lactation (d 139 to 242). Post-weaning body weight gain and indicators of humoral immune response post-vaccination were greater for BAC vs. CON calves (P ≤ 0.05). Therefore, changing the time and frequency of supplementation, and the use of additives and probiotics during late gestation of beef females are effective alternatives to improve offspring pre- and post-weaning growth and immune response.

Assessing supplementing strategies for beef cattle in a bale grazing system using grass hay during variable winter conditions

IntroductionBeef cattle in the Northern Great Plains of the United States of America are normally kept in open dry lot pens in winter. Practices such as bale grazing, swath grazing, stockpiling, and corn residue grazing, can be used to extend the grazing season and minimize dry lot use. Extending the grazing season has several advantages over dry lot use but arguably the most important benefit is cost savings due to lower labor and input costs. Strategies selected to supplement cattle in extended grazing systems should maintain cost savings while providing required nutrients to cattle. This study was conducted to evaluate supplementing strategies for beef cattle in a bale grazing system using grass hay during variable winter conditions. The study was conducted across variable winter conditions that are encountered in winters in the US Northern Great Plains.MethodsThe study extended over four years. Each year, non-lactating pregnant beef cows (n = 64, year 1; n = 80, year 2, 3, 4) were divided into eight groups of similar average body weight and randomly assigned to one of four bale grazing treatments as follows: a) bale grazing grass hay, b) bale grazing grass hay treated with a liquid supplement, c) bale grazing grass hay and alfalfa hay, and d) bale grazing grass hay and plus 1.8 kg corn DDGS/head/day. Animal performance was assessed from two-day body weights and body condition scores taken at the start and end of the study. Data analysis considered the fixed effects of treatment, year, and treatment x year interaction.ResultsFinal BW tended (P = 0.09) to be greatest following corn DDGS supplementation and lowest when grass hay was offered. The treatment strategy x year interaction (P = 0.026) for ADG showed that corn DDGS supplementation resulted in positive ADG across the years regardless of environmental conditions. Liquid or alfalfa hay supplementation resulted in positive ADG when environmental conditions were favorable. Final BCS (P = 0.005) and BCS change (P = 0.004) were greater following corn DDGS supplementation, intermediate following alfalfa hay or liquid supplementation and lowest when grass hay was fed. Supplementation costs ranged from $1.33 to $1.90/head/day, the highest cost occurred with corn DDGS supplementation mainly due to cost of corn DDGS and labor required to deliver corn DDGS to cattle on pasture.DiscussionAlfalfa hay or molasses-based liquids increased diet CP content but did not supply adequate energy in severely cold winters. Despite relatively higher supplement costs, high energy supplements such as corn DDGS may be required in severely cold winters where cattle require extra energy. Supplement selection should consider supplement effectiveness to meet animal nutrient requirements particularly in adverse winter conditions such as those encountered in the US Northern Great Plains.

Compensatory expansion of the cotyledonary surface in response to nutritional restriction in multiparous pregnant beef cows

Compensatory expansion of the cotyledonary surface in response to nutritional restriction in multiparous pregnant beef cows

Dietary guanidinoacetic acid as arginine spare molecule for beef cows at late gestation: Effects on cow’s performance and metabolism, and offspring growth and development

We aimed to assess whether guanidinoacetic acid (GAA) affects the performance, metabolism, and placental vascularization of pregnant beef cows during late gestation as well as its impact on the offspring’s performance. Twenty-eight pregnant Brahman cows, averaging 532±15.1 kg and carrying male (n=15) and female (n=13) fetuses, were used. The basal diet consisted of 688 g/kg corn silage, 147 g/kg sugarcane bagasse, 47.7 g/kg corn, 89.6 g/kg soybean meal, 6.86 g/kg urea, and 21.2 g/kg mineral mixture (DM basis). Cows were fed the experimental diets from 180 to 270 days of gestation. The following treatments were evaluated: control (no addition of GAA) or addition of 0.2 % GAA to the total diet (DM basis). There was no effect (P≥0.37) of GAA on voluntary intake. Similarly, GAA addition did not affect (P≥0.54) cows performance variables, except for ribeye area (REA), which had a lower (P<0.01) variation compared to the initial REA in cows fed dietary GAA compared to the control group. Dietary GAA increased (P≤0.02) both serum nitric oxide and placental vascularization compared to cows fed the control diet. There was no effect (P≥0.43) of GAA on urine and serum creatine concentrations. In contrast, dietary GAA increased (P≤0.03) plasma concentration of arginine, ornithine, citrulline, and tyrosine compared to the control. Conversely, dietary GAA decreased (P<0.02) plasma methionine concentration. Dietary GAA increased AGAT activity (P<0.03) in the liver, with no differences observed (P>0.68) on GAMT activity. There was no effect (P≥0.15) of GAA on performance of the offspring. Addition of GAA in maternal diet did not affect skeletal muscle fiber number (P>0.09) and diameter (P>0.23) of the offspring. Guanidinoacetic acid decreases skeletal muscle mobilization and enhances placental vascularization of beef cows during late gestation. However, providing GAA seems to not affect the performance of the offspring.

Protein supplementation during mid-gestation affects maternal voluntary feed intake, performance, digestibility,and uterine blood flow of beef cows.

This study aimed to assess the impact of protein supplementation and its interaction with calf sex (CS) on the performance, metabolismand physiology of pregnant beef cows. Fifty-two multiparous Zebu beef cows carrying female (n = 22) and male (n = 30) fetuses were used. Cows were individually housed from day 100 to 200 of gestation and randomly assigned to restricted (RES, n = 26) or supplemented (SUP, n = 26) groups. The RES cows were ad libitum fed a basal diet (corn silage + sugarcane bagasse + mineral mixture), achieving 5.5% crude protein (CP), while SUP cows received the same basal diet plus a protein supplement (40% CP, at 3.5 g/kg of body weight). All cows were fed the same diet during late gestation. Differences were declared at p < 0.05. No significant interaction between maternal nutrition and calf sex was found for maternal outcomes (p ≥ 0.34). The SUP treatment increased the total dry matter (DM) intake (p ≤ 0.01) by 32% and 19% at mid- and late-gestationrespectively. The total tract digestibility of all diet components was improved by SUP treatment at day 200 of gestation (p ≤ 0.02), as well as the ruminal microbial CP production (p ≤ 0.01). The SUP treatment increased (p ≤ 0.03) the cows'body score condition, ribeye area, the average daily gain (ADG) of pregnant components (PREG; i.e., weight accretion of cows caused by pregnancy)and the ADG of maternal tissues (i.e., weight accretion discounting the gain related to gestation) in the mid-gestation. The SUP cows exhibited a lower maternal ADG (p < 0.01) compared to RES cows in late pregnancy. There was a 24% additional gain (p < 0.01) in the PREG components for SUP cows during late gestation, which in turn improved the calf birthweight (p = 0.05). The uterine arterial resistance and pulsatility indexes (p ≤ 0.01) at mid-gestation were greater for RES cows. In conclusion, protein supplementation during mid-gestation is an effective practice for improving maternal performance, growth of the gravid uterusand the offspring's birth weight.

Colostrum Replacement and Serum IgG Concentrations in Beef Calves Delivered by Elective Cesarean Section.

Assistance during calving and cesarean section (C-section) are important risk factors for the failure of transfer of passive immunity (FTPI) in beef calves, which increases the risk of morbidity and mortality in beef calves during the preweaning period. Colostrum replacement recommendations for beef calves, and especially for those delivered by C-section, are unavailable. The objective of this study was to determine whether or not colostrum replacement or supplementation with a commercially available product could increase serum IgG concentrations in beef calves delivered by elective C-section, compared to beef calves that nursed colostrum naturally. An elective C-section was performed in 32 pregnant beef cows and first-calf heifers. Immediately after delivery, newborn calves were randomly assigned to one of three different treatment groups. Group A calves (n = 7) were fed one packet of a commercial colostrum replacer (CR) product providing 60 g of IgG within 30 min of life. A second packet of the same CR was fed at 6 h of life. Group B calves (n = 13) were fed the same CR at the same frequency as group A; however, these calves were reunited with their dams after the second CR feeding to allow additional nursing of maternal colostrum. Group C calves (n = 12) were united with their dams immediately after surgery without colostrum intervention. Serum IgG levels at 48 h of life were greater in group C calves and in calves born to multiparous cows. Based on the results of this study, neither colostrum replacement nor supplementation result in higher serum IgG concentrations in beef calves delivered by elective C-section compared with natural nursing.

165 Does supplementation of beef cattle impact the agronomy performance of tall fescue and bermudagrass pastures?

Abstract In forage-based beef cattle systems, bermudagrass [Cynodon dactylon (L.) Pers.] and tall fescue (Festuca arundinacea Schreb.) stand as widely used forage species. The strategic supplementation of animals may reduce forage intake, thereby potentially affecting the agronomic performance of these grasses. Our objective was to evaluate the impact of beef cattle supplemental feeding on forage accumulation, forage mass, and nutritive value in tall fescue and bermudagrass pastures. Two studies were conducted where pregnant beef cows were supplemental fed 1% of BW on DM basis of corn silage daily (SUP) or received no supplemental feeding (free-choice mineral; NON). Trial 1: conducted on bermudagrass pastures (BERM) grazed from late May to early October. Experimental design for BERM was completely randomized design with 4 pastures per treatment (n = 3 cows/pasture; average 5 years of age; 550 ± 72 kg initial BW). Trial 2: conducted on fescue pastures (FES) with an experimental design of a 2 x 2 factorial arrangement. The two factors evaluated were fescue type [TOXIC (507 ppm ± 0.82 SEM ergot alkaloids; 92.5% endophyte infection)] or non-toxin-producing (NT; 5 ppm ± 2.50 SEM ergot alkaloids; 38.6% endophyte infection) and two levels of supplemental feeding (NON or SUP). There were 3 or 4 replications per fescue x supplemental feeding treatment (n = 15 pastures), stocked with 3 cows/pasture (average age 4.75 years; 558 ± 73 kg initial BW) and grazed from early May through November. Forage accumulation (FA) was estimated every 28 d using the paired-cage method (4 exclosure cages/pasture). On each exclusion period, the forage mass (FM) was estimated both inside and outside the cages through destructive sampling method and samples analyzed for forage quality. Pasture was experimental unit and repeated measures were included in analysis. Bermudagrass FM tended to be increased by 31% with SUP (P = 0.09; 774 kg/ha greater). Forage accumulation tended (P = 0.07) to be affected by feeding method x month. There was greater FA in June for SUP; however, there was greater FA for NON in July. SUP pastures had greater ADF (1% more; P = 0.01) and reduced TDN (1.5%; P &amp;lt; 0.01) than NON. Forage mass tended to be 10% greater for TOXIC pastures (P = 0.09; 409 kg/ha more forage mass). Supplemental feeding on fescue did not impact FM (P = 0.74). Forage accumulation was not impacted by fescue type, feeding method, nor the interaction (P &amp;gt; 0.30). Cows generally do not consume as much toxic fescue, thus more forage is available in pastures and supplemental feeding did not alter forage parameters. However, on a warm-season grass that is growing while supplemental feeding, forage availability was increased and maybe useful as method to increase stocking rates or as mitigation tool during drought.

Performance and ruminal fermentation of second-trimester pregnant beef cows fed short-season high-moisture corn stover or barley greenfeed during winter in western Canada

This study evaluated performance and ruminal fermentation for cows fed short-season high-moisture shelled corn stover with corn dried distillers’ grains with solubles (COR) or barley greenfeed (BAR) that was either swathed (S-COR; S-BAR; Experiment 1) or baled (B-COR; B-BAR; Experiment 2) as winter-feeding systems. In Experiment 1, cows were randomly assigned to S-COR or S-BAR and fed for 52 days in the fields where crops were grown. Body weight (BW), subcutaneous rib and rump fat, and body condition score (BCS) were measured, with no differences detected between treatments ( P &gt; 0.05). However, S-COR had a lower estimated dry matter intake (DMI) than S-BAR ( P ≤ 0.03). In Experiment 2, cows were assigned to B-COR or B-BAR for 42 days and fed in field paddocks. Cows fed B-COR had less ( P ≤ 0.01) DMI, final BW, rib fat, rump fat, and BCS than B-BAR, with no differences ( P &gt; 0.05) for ruminal pH. Total SCFA concentration was greater ( P ≤ 0.05) on day 21 for B-BAR than B-COR, but not on day 42. Under western Canadian conditions, COR may reduce DMI and the performance of pregnant cows, suggesting that additional preservation and supplementation strategies should be investigated.

Postpartum hair cortisol, dehydroepiandrosterone sulfate and their ratio in beef cows: Exploring association with parity and conception outcome

Hair steroid measurement has received increasing attention for monitoring hypothalamic-pituitary-adrenal axis function, as it offers the advantages of being noninvasive, fast, and able to indicate steroid concentrations over long periods. The objects of the study were to evaluate cortisol (C) and dehydroepiandrosterone sulfate (DHEA-S) hair concentrations and their ratio (C/DHEA-S) in beef cows from calving to 100 days (d) postpartum (pp) and to assess possible differences related to parity (primiparous vs multiparous) and conception outcome (pregnant vs not pregnant). Hair samples were collected from 6 primiparous and 5 multiparous pregnant beef cows by clipping the coat at calving (T0) and every 20 d for 5 times (T1-T5), collecting only the regrown hair. Starting from the 6th-week pp, cows were submitted to artificial insemination at spontaneous estrus; by 100 d pp, 7 cows were pregnant and 4 were not pregnant. Statistical analysis showed higher hair C concentrations in the 11 cows at calving (T0) compared to all the subsequent samplings except for T1, and higher C concentrations at T1 compared to T3, T4, and T5. These results indicate that hair C concentrations in beef cows are affected by sampling time, with a decrease from calving, as reported in other matrices. When exploring changes within parity groups, no differences were found in the multiparous among sampling times, while hair C concentrations at T0 and T1 tended to be higher than at T2 (0.01 ≤ p < 0.05) and were higher (p < 0.01) than in all the subsequent samplings (T3, T4 and T5) within the primiparous group. Higher hair C concentrations were found at T0 and T1 in the primiparous compared to multiparous (p < 0.01), suggesting that primiparous cows undergo a greater stress level before and around parturition compared to multiparous, probably due to the novelty of the calving experience. No differences were detected in C hair concentrations according to conception outcome (pregnant versus not pregnant) in each sampling time. Hair DHEA-S concentrations were neither affected by time nor by parity or conception outcome. Differences in the C/DHEA-S ratio were found at T1, with higher C/DHEA-S in the multiparous compared to primiparous cows (p < 0.001), and a tendency for higher ratio in the not pregnant compared to the pregnant (0.01 ≤ p < 0.05). These results support the choice of hair as a valuable biological matrix when investigating long-time periods such as postpartum in cows and suggest an enhanced immunoprotective effect of DHEA-S in the postpartum of primiparous cows, and in cows that get pregnant within 100 d postpartum.

PSIX-22 Performance, Digestibility, and Blood Parameters in Pregnant Beef Cows Fed Total Mixed Ration Silages

Abstract The aim of this study was to investigate the effects of two total mixed ration (TMR) silages (low and high rumen undegradable protein; RUP) on digestibility, blood parameters, and performance in pregnant beef cows. Thirty-three mid-gestation (~130 d of gestation) Tabapua beef cows were randomly assigned to 1 of 2 treatments: 1) a TMR silage containing Brachiaria grass, soybean hulls, urea, and mineral mix (low RUP; n = 16) or 2) a TMR silage containing Brachiaria grass, DDG, and mineral mix (high RUP; n = 17). The concentration of A1 fraction was, on average, 12.9% and 34.0% of N in low and high RUP silages, respectively. A preservative with a blend of organic acids, surfactants, and activated propionates was applied in both silages. Pressed bag silos were used to conserve silages for 7 wk. Cows were housed in individual pens for 100 d. During a 4-d digestion period (at 50 d of housing), fecal samples were collected for measurement of nutrient digestibility using undigested neutral detergent fiber as a marker. Blood parameters were collected at the last day of housing. Statistical analysis of experimental data was performed using the GLM procedure of SAS 9.4. Diet, calf sex (male or female), and interactions between these factors were considered fixed effects. No differences were obtained for initial BW. High RUP diet showed greater final BW (P = 0.0004) and ADG (P = 0.0003). Cows fed high RUP gained 50 g/d, while cows fed low RUP diet lost 445 g/d. Dry matter intake was greater by 23% (P &amp;lt; 0.0001) in cows consuming high RUP silage. Dry matter, CP, and NDF digestibility did not differ between treatments. Regarding blood parameters, no differences were observed for glucose at 0 h and 4 h post-feeding. Plasma urea at 0 h post-feeding was greater in cows fed low RUP silage (P = 0.0003). However, no differences were observed for plasma urea at 4 h post-feeding. The plasma concentrations of non-esterified fatty acids (P = 0.017) and beta-hydroxy-butyric acid (P = 0.002) were greater in cows consuming low RUP diet. Overall, feeding pregnant cows during mid-gestation with TMR silage containing high RUP promotes greater performance.

PSXIV-1 Impact of Slow-Release Nitrogen Or Regular Protein-Based Supplementation During Late Gestation on Maternal and Offspring Performance in Beef Cattle

Abstract The objective of this study was to determine whether supplementing pregnant beef cows with regular nitrogen or a slow-release nitrogen source at the late gestation could enhance the use of a low protein basal diet and improve the performance of cows and their offspring until weaning. Thirty-five pregnant Brahman cows (556 ± 47 kg and 4.5 ± 1.4 years old) were individually housed in covered pens and randomly divided into three groups. From 180 ± 19 days of gestation until calving, cows were fed either a control (CON, n = 12) low crude protein (CP) basal diet (6% of CP, ad libitum) plus mineral mixture (130 g·cow-1·d-1), or the CON treatment supplemented with protein concentrate supplements (40% CP, fed 2 g·kg of BW-1·d-1 in the morning) based either on a regular (REG, n = 11) composition (corn, soybean meal, and urea) or on a slow-release N (SRN, n = 12) source (Timafeed Boost, Roullier Group, Saint-Malo, France) which replaced 60% of soybean meal and urea in the supplement composition. The MN, fetal sex (FS), and MN×FS were used as fixed effects in the statistical model, while the number of previous calvings was considered as a random effect. Maternal initial BW was used as a covariate. Statistical differences were declared at P &amp;lt; 0.05. Supplementation with REG and SRN increased total dry matter intake (DMI) and basal diet intake compared with the control treatment (P &amp;lt; 0.01). Protein supplementation allowed the cows to have a higher average daily gain (P &amp;lt; 0.01; 0.177 and 0.193 kg/day, respectively, for REG and SRN) than the CON treatment (-0.255 kg/day). Body condition score (BCS) also increased (P &amp;lt; 0.01) when cows received protein supplementation in late pregnancy, but with no differences between REG and SRN cows (P = 0.31). Interactions between MN and FS were observed for calf birth weight (CBW, P &amp;lt; 0.01) and calves' average daily gain up to 120 days of age (ADG120, P = 0.01), but not at weaning weight (P = 0.69). Male calves born from REG and SRN cows were born heavier and gained more weight up to 120 days after birth than calves born from CON cows (P &amp;lt; 0.05) but did not differ from each other (P = 0.94 and 0.92, respectively, for CBW and ADG120). Female calves had no differences in CBW and ADG120 as a function of maternal dietary treatment during pregnancy. The REG and SRN calves weaned heavier (P &amp;lt; 0.05) than CON calves. In conclusion, supplementing protein to pregnant beef cows during periods of low CP pasture improves maternal and progeny performance. The SRN-based product can replace the major part of soybean and urea in the protein supplement, achieving same level of improvement in forage utilization and animal performance as the regular protein-based supplement.

Can the post-ruminal urea release impact liver metabolism, and nutritional status of beef cows at late gestation?

We aimed to evaluate the effects of post-ruminal supply of urea (PRU) on nutritional status, and liver metabolism of pregnant beef cows during late gestation. Twenty-four Brahman dams, pregnant from a single sire, and weighing 545 kg ± 23 kg were confined into individual pens at 174 ± 23 d of gestation, and randomly assigned into one of two dietary treatments up to 270 d of gestation: Control (CON, n = 12), consisting of a basal diet supplemented with conventional urea, where the cows were fed with diets containing 13.5 g conventional urea per kg dry matter; and PRU (PRU, n = 12), consisting of a basal diet supplemented with a urea coated to extensively prevent ruminal degradation while being intestinally digestible, where the cows were fed with diets containing 14,8 g urea protected from ruminal degradation per kg dry matter. Post-ruminal supply of urea reduced the urine levels of 3-methylhistidine (P = 0.02). There were no differences between treatments for dry matter intake (DMI; P = 0.76), total digestible nutrient (TDN) intake (P = 0.30), and in the body composition variables, such as, subcutaneous fat thickness (SFT; P = 0.72), and rib eye area (REA; P = 0.85). In addition, there were no differences between treatments for serum levels of glucose (P = 0.87), and serum levels of glucogenic (P = 0.28), ketogenic (P = 0.72), glucogenic, and ketogenic (P = 0.45) amino acids, neither for urea in urine (P = 0.51) as well as urea serum (P = 0.30). One the other hand, enriched pathways were differentiated related to carbohydrate digestion, and absorption, glycolysis, pyruvate metabolism, oxidative phosphorylation, pentose phosphate pathway, and biosynthesis of amino acids of the exclusively expressed proteins in PRU cows. Shifting urea supply from the rumen to post-ruminal compartments decreases muscle catabolism in cows during late gestation. Our findings indicate that post-ruminal urea supplementation for beef cows at late gestation may improve the energy metabolism to support maternal demands. In addition, the post-ruminal urea release seems to be able to trigger pathways to counterbalance the oxidative stress associated to the increase liver metabolic rate.

Genotype by Prenatal Environment Interaction for Postnatal Growth of Nelore Beef Cattle Raised under Tropical Grazing Conditions.

The prenatal environment is recognized as crucial for the postnatal performance in cattle. In tropical regions, pregnant beef cows commonly experience nutritional restriction during the second half of the gestation period. Thus, the present study was designed to analyze the genotype by prenatal environment interaction (G × Epn) and to identify genomic regions associated with the level and response in growth and reproduction-related traits of beef cattle to changes in the prenatal environment. A reaction norm model was applied to data from two Nelore herds using the solutions of contemporary groups for birth weight as a descriptor variable of the gestational environment quality. A better gestational environment favored weights until weaning, scrotal circumference at yearling, and days to first calving of the offspring. The G × Epn was strong enough to result in heterogeneity of variance components and genetic parameters in addition to reranking of estimated breeding values and SNPs effects. Several genomic regions associated with the level of performance and specific responses of the animals to variations in the gestational environment were revealed, which harbor QTLs and can be exploited for selection purposes. Therefore, genetic evaluation models considering G × Epn and special management and nutrition care for pregnant cows are recommended.

Effects of endophyte-infected tall fescue on performance of genotyped pregnant beef cows supplemented with rumen-protected niacin

A total of 28 Angus × Simmental pregnant dams (11 cows and 17 heifers) were selected based on genetic resistance to fescue toxicosis based on a commercial genetic test (T-snip™, Ag. Botanica, Columbia, MO). Subsequently, dams were divided based on genetic resistance to fescue toxicosis and randomly assigned to dietary treatments: 1) Susceptible Control (SC; n = 7); 2) Susceptible Niacin (SN; n = 7); 3) Tolerant Control (TC; n = 7); and 4) Tolerant Niacin (TN; n = 7). All animals received 1.16 kg of endophyte-infected (E+) tall fescue seeds for a period of 30 days. Ergovaline concentration in fescue seeds was ∼5,000 ppb on a DM basis. Dams in SN and TN groups received 6 g/hd/day as-fed of top-dressed rumen-protected niacin, following manufacturer's maximum dose recommendation. Dams in the TN group experienced an accelerated reduction in BW as compared to the rest of the treatments. However, TN offspring did not show BW differences at birth or weaning as compared to those born to dams in other treatments. Milk production was estimated by the weigh-suckle-weigh method, and no difference was observed among treatments. All dams had a reduction in circulating prolactin concentration, indicating that all animals were experiencing fescue toxicosis. In addition, blood metabolites that indicate liver health status were markedly decreased at the end of the study. Overall, these results suggest that dams receiving E+ tall fescue seeds were effectively exposed to fescue toxicosis symptoms. Nevertheless, neither rumen-protected niacin supplementation nor genetic test for resistance to fescue toxicosis could be used as an efficient mechanism of dampening these symptoms.

Update on copper and selenium in Canadian cow-calf herds: regional differences and estimation of serum reference values.

Trace mineral supplementation of beef cattle is essential for efficient reproduction and herd health. Understanding regional differences in cow trace mineral status could inform decisions about risks of deficiencies and supplementation management. Cow-calf surveillance projects provided three opportunities to evaluate the trace mineral status of Canadian beef cow herds. Blood samples were collected at pregnancy testing in 2014 from 102 cow-calf herds and in 2016 from 86 cow-calf herds in Western Canada. In 2019, blood samples were collected at pregnancy testing from cows in 163 cow-calf herds from Eastern and Western Canada. Serum samples were analyzed for copper, selenium, and molybdenum concentrations using a plasma mass spectrometer. The prevalence of copper deficient cows sampled from the Western provinces ranged from 24% to 43% across the three periods, and was 20% from Eastern Canada in 2019. The prevalence of selenium deficient cows ranged from 0.2% to 0.4% across the three projects in Western Canada, but was higher in Eastern Canada at 4.6% in 2019. High serum molybdenum was identified in 9.4% to 14% of cows across the three periods in Western Canada and in 15% of cows sampled in Eastern Canada in 2019. Serum copper, selenium, and molybdenum concentrations varied by cow age and month of sample collection. Serum selenium and molybdenum concentrations, but not copper, varied by soil type associated with the location of the farm. A subsample of samples from cows from Western Canadian herds provided body condition score (BCS) data, pregnancy status, and calf survival data and were used to estimate updated serum reference values for adequate concentrations. Age-specific values were required for selenium and molybdenum. Reference intervals (80%) were estimated from 2,406 pregnant beef cows from 99 herds with each cow having a BCS ≥ 2.5/5 and a live calf at 3 wk with no retained placenta: copper for all cows (0.379 to 0.717 ppm), selenium for cows <4 yr (0.052 to 0.152 ppm), and selenium for cows ≥4 yr (0.064 to 0.184 ppm). Upper 90% reference limits were also estimated for serum molybdenum for cows <4 yr (>0.104 ppm) and cows ≥4 yr (>0.110 ppm). The lower limits for the reference intervals for adequate copper and selenium are below those previously reported; nevertheless, they represent a large sample that was specifically applicable to extensively managed beef animals in western Canada.

Malnutrition of pregnant beef cows and the impact on passive immunity transfer to calves

Nutritional management in rangeland beef cattle systems prioritises optimal body condition scores at calving for improved fertility and reproductive success. However, this focus often overlooks short-term dietary deficiencies before calving, which can lead to adverse outcomes for neonatal calves. This review explores the effects of beef cow malnutrition during the periparturient period on colostrum production, lactation onset, and passive immunity transfer to calves. Additionally, it discusses the long-term impact of such malnutrition on the offspring. By understanding how nutritional interventions affect the transition from gestation to lactation, it becomes possible to enhance calf health and survival in arid tropical environments. Commonly occurring short-term dietary restrictions, particularly protein deficiencies, can disrupt the hormonal equilibrium, resulting in reduced colostrum volume and quality, hindering calf growth and increasing mortality risks. Furthermore, dietary restrictions during this period affect critical physiological processes such as mammary gland blood flow and fetal small-intestine development. The review explores how these constraints influence colostrum production and immunoglobulin absorption by neonatal calves. Additionally, it highlights the significance of addressing other common nutrient deficiencies such as phosphorus and water and investigates the potential benefits of supplementing microbial products to enhance rumen function and protect cows from inflammation. Ultimately, addressing malnutrition during pregnancy is essential to prevent negative impacts on offspring performance, including alterations in carcass composition and muscle marbling. Consequently, cattle producers who aim for superior muscle marbling in the carcass by using costly genetics should give priority to enhancing nutritional programs for late-pregnant cows. In conclusion, a comprehensive understanding of the effects of malnutrition during the periparturient period on colostrum production, passive immunity transfer, and overall calf health is crucial for developing effective nutritional interventions that improve colostrum production, passive immunity transfer, and overall calf health in rangeland beef cattle systems.

Effects of stage of maturity at harvest of cereal crops on biomass and quality, estimated forage dry matter intake, beef cow performance, and system economics

The objective of this study was to evaluate the effects of maturity at harvest of cereal crops on biomass, quality, cow performance, and economics. In each of 3 yr, a 48-ha field was divided into 3 paddocks (16 ha per treatment) and seeded to either barley (Hordeum vulgare CDC Maverick, 135 kg/ha), oat (Avena sativa CDC 29 SO1, 135 kg/ha), or triticale (Triticosecale Taza, 135 kg/ha). Half of each field (8 ha) was swathed at either soft dough (SDo) or hard dough (HDo) stage for grazing. Each year, 120 dry pregnant beef cows (631 kg) were randomly allocated to 1 of 6 replicated (n = 2) paddocks for 90, 106, and 88 d in yr 1, 2, and 3, respectively. Triticale had 19 and 23% greater total yield than oat and barley, respectively. Barley CP was greater (P < 0.05; 10.9%) than oat (9.3%) or triticale (9.8%) at HDo stage. The animal unit months (AUM) per hectare were greater for HDo (11.5 ± 0.8 AUM/ha) than SDo (9.15 ± 0.8 AUM/ha) stage. Cow ADG was greater (P = 0.01) for barley (0.61 kg/d) compared with triticale (0.39 kg/d). Total crop cost averaged Can$426, Can$437, and Can$458/ha for oat, barley, and triticale, respectively. The HDo stage had Can$0.40 lower dollars per cow per day in-field costs (P = 0.02) than the SDo stage and 10% (Can$26.25 per cow/d) lower feeding costs (P = 0.02) over 3 yr. Delaying harvest to hard dough can increase yield and reduce feeding costs without affecting cow performance.

PSI-10 Effect of Chronic Melatonin Supplementation During mid to Late Gestation on Performance and Behavioral Responses of Cows Exposed to Summer Heat Stress

Abstract Summer heat stress negatively impacts the health and welfare of animals. Melatonin is a highly potent antioxidant and free radical scavenger with immune modulation and anti-inflammatory effects in domestic animals. This study examined the effect of supplemental melatonin during mid to late gestation on serum cortisol, heat shock protein 90 (HS90) and glucose concentrations, performance, behavior and hemogram of pregnant cows and their offspring. Multiparous pregnant beef cows were randomly assigned to 1 of 2 groups and supplemented with Melatonin® implants 24 mg (MEL, n=13) or without (CON, n=12) at day 190, 218, and 246 of gestation. Also, offspring performance (n = 24) was evaluated. Body weight, rectal temperature, hemogram, behavioral responses of cows (chute score, vocalization and exit score) were scored biweekly for 16 weeks. The average daily gain (ADG), rectal temperature, glucose concentration and hemogram of cows and calves showed no significant difference (P&amp;gt;0.05) between treatments except in calves were platelet were higher in MEL treated calves than control. Cortisol levels were significantly lower (P&amp;lt; 0.05) in MEL cows compare to CON from day 14 (1437 ± 2.54 and 2028 ± 3.23 pg/ml respectively) to the end of the experiment. Also, serum HSP90 concentrations were significantly lower (P&amp;lt; 0.05) from day 14 to the end of the study period (0 ng/ml and 0.73 ng/ml respectively). Chute and exit score did not differ significant between groups. Our results revealed that chronic melatonin supplementation during mid to late gestation reduced serum cortisol and HSP90 in cows exposed to summer heat stress.