Performance Of Beef Cows Research Articles

PSII-14 Influence of recent postpartum weight variation on milk production, cow and calf performance and reproductive efficiency of beef cows in Southern Brazil

Abstract The objective of this study was to evaluate the influence of the weight changes between calving to peak lactation of range beef cows on the cow and calf performance, milk production and pregnancy rate. Data were collected from 142 primiparous and multiparous beef cows, over a 5-year period. Cows and calves were raised in an extensive range system in Southern Brazil. Cows were divided into two groups according to calving performance and peak lactation. Cows that lost weight (L group, n = 59) and cows that gain weight (G group, n = 83). Milk yield evaluation (weigh-suckle-weigh technique), cow and calf performance were estimated from calving to 189 postpartum days, every 21 days. Cows were subjected to an estrus synchronization protocol and after that, breed by natural service for 45 days. Analysis of variance (ANOVA - GLM) was performed considering effects of the two groups, and pregnancy rates were compared using chi-square analysis. Calves from L cows had greater (P = 0.03) ADG between 21 and 42 days postpartum. However, there was no difference (P > 0.05) in weaning weight. Total milk production was greater (P = 0.01) in L cows. The cows from group G showed a tendency (P = 0.08) to increase pregnancy rate by 15% compared to L cows. In conclusion, cows that gain weight between calving to peak lactation have lower total milk production without any influence in calf performance, and appear to have an increase in pregnancy rate.

76 Does supplemental protein and rumen-protected methionine improve performance and digestibility during late-gestation in beef cows?

Abstract Methionine (MET) is likely the first limiting amino acid in low-protein forages fed to beef cattle during late-gestation. Therefore, the objective of this study was to determine if supplemental protein and rumen-protected MET improve cow performance and apparent tract digestibility (TTD) during late-gestation. This study used 147 late-gestation Angus crossbred cows and heifers in a 3x2 factorial arrangement for dietary treatments. The cattle were randomly assigned to one of six diets formulated to 90, 100 or 110% of metabolizable protein (MP) requirements (NRC, 2016), with (without) 9 g/d of rumen-protected MET (MetaSmart, Adisseo Inc.). These diets were fed for approximately 8 wks before calving. All data was analyzed as a randomized block design using SAS 9.4 PROC GLIMMIX procedure. Cows fed at 90% MP requirements lost body weight (BW), while cows fed at 100% and 110% MP requirements maintained and (or) gained BW over the trial (P = 0.02). Similarly, cows fed at 90% MP requirements lost more pregnancy corrected BW than cows fed at 100% and 110% MP requirements (P = 0.01). However, supplemental MET did not affect body weight gains (P > 0.07). Cows and heifers fed at 90% MP requirements had reduced TTD for crude protein compared to cattle fed to 110% MP requirements (P < 0.001), MET supplementation did not impact TTD (P > 0.20). Additionally, cattle fed at 90% MP requirements had increased serum cholesterol and reduced urea concentrations compared to cows fed to 100% and 110% MP requirements (P < 0.0001). MET supplementation increased serum concentrations for glucose, isoleucine, leucine, lysine, serine, threonine and valine (P < 0.02). Calf birth weights were not significantly impacted by dietary treatment (P > 0.31). Feeding cows above their MP requirements may improve late-gestation performance and CP digestibility. Supplemental MET may increase amino acid utilization but did not improve beef cow performance or digestibility parameters measured in late-gestation.

PSIII-29 Effects of late gestational tall fescue forage system on spring-calving beef cow performance, circulating metabolites, and colostrum quality

Abstract Multiparous cows [n = 56; 639 ± 73 (SD) kg initial BW; 5.3 ± 0.4 initial BCS; 5.9 ± 3.0 yr of age; February 16, 2016 average calving date] were allocated by BW, BCS, age, and expected calving date to strip-graze endophyte-infected stockpiled tall fescue (STF; n = 4 pastures; 12.5% CP, 59.5% NDF; DM basis) or consume ad libitum endophyte-infected tall fescue hay (n = 4 uncovered drylots; 7.5% CP, 65.3% NDF; DM basis) for the last 75.0 ± 11.9 d of gestation. At 13.5 ± 1.6 d pre-calving, STF cows were moved to drylots and fed tall fescue haylage (12.6% CP, 61.7% NDF; DM basis). Effects of forage system were included in the model with pen as experimental unit. For gestational metabolites, effects of forage system, day, and their interaction were included with day as a repeated measure. Forage system did not affect (P ≥ 0.35) cow BW. Cows fed STF had greater (P ≤ 0.06) BCS than hay-fed cows at d 32 and 62 of study. Forage system did not affect (P ≥ 0.12) gestational plasma glucose or triglycerides. Serum non-esterified fatty acids (NEFA) were greater (P ≤ 0.005) in hay-fed cows at d 32 and 82 of study and less (P = 0.02) at d 62 of study. After study initiation, serum urea N was greater (P ≤ 0.002) in STF-fed cows than hay-fed cows. At colostrum sampling (6.8 ± 0.9 h postpartum), forage system did not affect (P ≥ 0.10) circulating NEFA, glucose, or triglycerides. Cows fed STF had greater (P ≤ 0.002) serum and colostrum urea N than hay-fed cows. Forage system did not affect (P ≥ 0.17) colostrum protein, lactose, triglyceride, or immunoglobulin concentrations. In conclusion, grazing STF improved cow BCS and altered cow metabolic status but did not affect colostrum quality.

Influence of ractopamine hydrochloride and days on feed on feedlot performance and red meat yield in thin cull beef cows targeted for a lean market

Thin, beef, cull cows [n = 144; initial body weight (BW) = 465.8 ± 56.9 kg, initial body condition score (BCS) = 2.13 ± 0.68] were serially slaughtered to evaluate the relationship between ractopamine hydrochloride (RH) administration and days on feed (DOF) on feedlot performance and carcass cutout value in a lean cow market. Cows were organized into a 3 × 2 factorial arrangement of treatments (48 pens, 8 pens per treatment, 3 cows per pen) and blocked by BW nested within pregnancy status. Treatment pens were top-dressed 400 mg per cow per day of RH (Actogain 45; Zoetis, Parsippany, NJ) for the final 28 d prior to slaughter to cows spending 28, 42, or 56 DOF. Pen served as the experimental unit, for all calculations. No RH × DOF interactions were detected (P ≥ 0.11), indicating that despite a majority of compensatory gain occurring during the first 28 d of the trial, the magnitude of the RH response was not affected by DOF. Compared to controls, RH incited improvements in feedlot performance, but had a greater extent on carcass weight gain and efficiency. Specifically, RH improved average daily gain (ADG) by 13.7% (P = 0.04) and carcass ADG by 16.9% (P = 0.02) Cattle fed RH displayed a 15.5% improved gain to feed ratio (P = 0.02) and a 20% improved carcass gain to feed ratio (P = 0.05). Inclusion of RH in the finishing diet increased hot carcass weight by 4.5% (P = 0.05; 12.9 kg). However, supplementation of RH did not alter red meat yield (P ≥ 0.16), but provoked a 11.1% improvement in lean maturity (P < 0.01). Evaluation of the main effect of DOF provided insight into the compensatory state of beef cull cows on a high-concentrate diet. Serial slaughter offal weights presented confounding results. With additional DOF, a numerical increase in liver weights (P = 0.20) suggested that organ tissue replenishment occurred throughout the trial, and cattle experienced compensatory gain during the entire feeding phase. In contrast, lung and heart weights were not altered, while kidney tended to decrease linearly (P = 0.08) despite additional DOF. Furthermore, extending DOF generated a linear increase in dry matter intake (P < 0.01) yet a tendency for a decline in ADG (P = 0.10), reinforcing the premise that most of compensatory gain occurred during the first 28 d of the trial. If thin (BCS ≤ 4), healthy candidates can be finished, feeders can reap the benefits of an additive relationship between compensatory gain and RH.

Influence of dietary roughage level and Megasphaera elsdenii on feedlot performance and carcass composition of thin cull beef cows fed for a lean market.

One hundred forty-four cull cows (body condition score = 2.10 ± 0.61; BW = 456 ± 47 kg) were organized into a 2 × 2 factorial design (48 pens, 12 pens/treatment, and 3 cows/pen) to evaluate the effect of dietary roughage level and oral drenching of Megasphaera elsdenii NCIMB 41125 (M. elsdenii culture; Lactipro Advance; MS Biotec Inc., Wamego, KS) on performance and carcass characteristics. Cattle were finished over a 42-day realimentation period, and aggressively stepped up over a 10-day period to either a high roughage finisher (HRF; 25% roughage) or a low roughage finisher (LRF; 10% roughage). Within diet, cattle were administered no probiotic or 100 mL of M. elsdenii culture (M. elsdenii NCIMB 41125, 2 108 cfu/mL) on day 0. No diet × probiotic interactions were detected (P ≥ 0.15), suggesting that the magnitude of the response was not influenced by the concentrate level of the diet. The main effect of diet triggered several significant responses. Decreasing roughage level tended to improve average daily gain (ADG) by 9.7% (0.26 kg, P = 0.08), while decreasing dry matter intake (DMI) by 0.9 kg (P = 0.09), provoking a 19.7% enhancement of feed efficiency (0.036 units, P < 0.01). However, interim data revealed declines of performance parameters among both diets with a significant difference between treatments only documented during the final phase of the realimentation period. During the final 14 days, LRF posted a 0.68 kg increase in ADG (P = 0.05) and a 2.0 kg decrease in DMI (P = 0.01), translating to improved feed efficiency (0.054 units, P = 0.03). This suggests that increasing the caloric density of finishing diets may help offset the regression of performance typically observed following a compensatory gain. No carcass traits were impacted by either diet or M. elsdenii culture (P ≥ 0.08). Overall, oral drenching of M. elsdenii culture tended to augment ADG (0.26 kg, P = 0.08) and carcass ADG (0.20 kg, P = 0.10). Implying that M. elsdenii culture was effective at alleviating the acidosis risk prompted by the rapid step-up period employed in the trial and may help capitalize on the narrow timeline of compensatory gain in cull cow realimentation.

Changing views on the role of the uterus in post-partum reproductive function in beef cows1.

The paradigm for post-partum management of well-being and reproductive function in beef cows is changing. For many decades, research focused on the hypothalamic-pituitary-ovarian axis in attempts to manage beef cows to resume estrous cycles more quickly, because uterine involution was not considered a factor that was limiting to reproductive function in post-partum beef cows (Kiracofe, 1980). Questions remained, however, about the prevalence of subclinical endometritis in beef cows, and about the impact of sub-clinical reproductive tract health on subsequent reproductive performance and well-being (McNeel et al., 2017a). In a pair of papers published in this issue of the Journal of Animal Science, Ault and colleagues (Ault et al., 2019a,b) investigated the uterine and vaginal microbiome in post-partum beef cows using next generation sequencing and demonstrated that a less diverse uterine microbiome in the post-partum interval close to breeding was associated with a decreased risk of conception to timed artificial insemination. A similar result was reported for the vaginal microbiome of post-partum dairy cows (Bicalho et al., 2017). Beef cows, therefore, may not have as many cases of clinical metritis, but some of the same components of post-partum reproductive health may be influencing post-partum re-breeding efficiency in beef cows as in dairy cows. The results of studies examining the influence of endometrial cytology on reproductive performance in post-partum beef cows have been mixed (Santos et al., 2009; Ricci et al., 2017); however, the papers by Ault and colleagues indicate that the application of next generation sequencing technologies may allow more accurate determination of the relationships between post-partum reproductive tract health and re-breeding efficiency.

150 Administration of prostaglandin F2α 24 h prior to CIDR removal impacts reproductive performance of suckled beef cows assigned to the 7-d CO-Synch + CIDR protocol

Abstract Angus-influenced cows received 100 µg of GnRH and a CIDR device containing 1.38 g of progesterone (P4) on d 0, and were randomly assigned to 25-mg injection of PGF2α on d 6 (PG6; n = 147) or d 7 (PG7; n = 162). The CIDR device was removed on d 7, and cows received 100 µg of GnRH and artificial insemination (AI) on d 10. An estrus detection patch was attached to the tailhed of each cow on d 7, and estrus expression assessed at AI (&gt; 50% coating removal). Blood samples were collected on d 0 to determine the presence of a functional corpus luteum via plasma P4 (CL, P4 ≥ 1.0 ng/mL; NOCL P4&lt; 1.0 ng/ mL). A subset of cows (70 cows/treatment) were assigned to ultrasonography at AI to verify dominant follicle diameter (DFD). Blood samples for plasma P4 analysis were collected (42 cows/treatment) on d 6, and on d 7 at CIDR removal and 1 h later. A similar proportion of PG6 and PG7 cows were classified as CL (P = 0.38). Plasma P4 at CIDR removal and 1 h later were less in PG6 vs. PG7 cows classified as CL (1.81 vs. 3.99 and 1.06 vs. 2.89 ng/mL), and did not differ (P ≥ 0.43) within NOCL. Estrus expression was greater in PG6 vs. PG7 cows classified as CL (72.8 vs. 48.3%), but similar (P = 0.96) within NOCL. Pregnancy rates did not differ between treatments (P = 0.53), despite a numerical difference (P = 0.15) between PG6 vs. PG7 cows classified as CL (65.5 vs. 55.0%). No other treatment effects were detected (P ≥ 0.20). Hence, PGF2α administration 24 h prior to CIDR removal appears to benefit reproductive performance of beef cows with a functional CL at the beginning of the 7-d CO-Synch + CIDR protocol

57 Impact of weaning strategy on beef cow performance

Abstract It has been shown that physiologic stress in beef cattle can impact animal performance. Weaning stress is recognized as a major stress in a calf’s life. However, less is known of its impacts on the dam or developing fetus, as the dam is at the end of the second trimester at weaning. Therefore, the objective was to investigate the impact of weaning stress on cow performance. A total of 240 cows from two locations were assigned to one of three weaning strategies: abrupt removal of the calf on d 0 (n = 80), d 7 cow-calf fenceline contact (n = 81), and late weaning on d 84 (n = 79). Cows averaged 16 and 24 weeks of gestation on d 0 and d 84 respectively. Weights and BCS were obtained monthly. Behavioral observations occurred over the week before and after weaning for each weaning period. Five late-wean cows per location were milked on d 14 and d 70 to estimate milk yield throughout the late wean period. Data were analyzed using the MIXED procedure of SAS with BW and BCS utilizing repeated measures. Means are declared different at P ≤ 0.05. The ADG over the course of the study was lower (P &lt; 0.05) for the late weaned cows compared to the abrupt weaned cows. This was also reflected by change in body condition where late weaned cows dropped from a 5.7 to a 4.9 (P &lt; 0.05) over the 105 d. Milk production in late weaned cows decreased over time (6.0 and 4.4 kg/d for d 14 and 70, respectively; P = 0.05). Energy expenditure for lactation may have contributed to the drop in BCS of the late weaned compared with the non-lactating cows and could compromise third trimester growth of calf in utero. The results of this study warrant further exploration of the effect of weaning stress on dams and their developing fetuses.

48 Impact of weaning strategy on beef cow performance

Abstract It has been shown that physiologic stress in beef cattle can impact animal performance. Weaning stress is recognized as a major stress in a calf’s life. However, less is known of its impacts on the dam or developing fetus, as the dam is at the end of the second trimester at weaning. Therefore, the objective was to investigate the impact of weaning stress on cow performance. A total of 240 cows from two locations were assigned to one of three weaning strategies: abrupt removal of the calf on d 0 (n = 80), d 7 cow-calf fenceline contact (n = 81), and late weaning on d 84 (n = 79). Cows averaged 16 and 24 weeks of gestation on d 0 and d 84 respectively. Weights and BCS were obtained monthly. Behavioral observations occurred over the week before and after weaning for each weaning period. Five late-wean cows per location were milked on d 14 and d 70 to estimate milk yield throughout the late wean period. Data were analyzed using the MIXED procedure of SAS with BW and BCS utilizing repeated measures. Means are declared different at P ≤ 0.05. The ADG over the course of the study was lower (P &lt; 0.05) for the late weaned cows compared to the abrupt weaned cows. This was also reflected by change in body condition where late weaned cows dropped from a 5.7 to a 4.9 (P &lt; 0.05) over the 105 d. Milk production in late weaned cows decreased over time (6.0 and 4.4 kg/d for d 14 and 70, respectively; P = 0.05). Energy expenditure for lactation may have contributed to the drop in BCS of the late weaned compared with the non-lactating cows and could compromise third trimester growth of calf in utero. The results of this study warrant further exploration of the effect of weaning stress on dams and their developing fetuses.

164 Effects of year-round supplementation of sugarcane molasses/urea or range cubes on growth performance of Bos indicus-influenced beef cows and their offspring

Abstract This study compared the effectiveness of liquid sugarcane molasses/urea or wheat middlings-based range cubes supplementation on performance of beef cow-calf pairs. On d 0, 82 mature pregnant Brangus cows were stratified by BW and BCS (433 ± 47 kg; BCS = 4.6 ± 0.77) and randomly allocated into 1 of 6 bahiagrass pastures (13–14 pairs and 9.3 ha/pasture). Treatments were assigned randomly to pastures (2 pastures/treatment) and consisted of cows offered: winter supplementation of molasses/urea from calving until end of breeding season (d 161 to 300; MOL-W), or year-round supplementation of liquid urea/molasses (MOL-Y) or range cubes (CUB-Y). Supplement amount offered to cows differed monthly among treatments, but all cows were limit-fed 272 kg/yr of the respective supplement DM and similar trace mineral supplementation (336 g/cow/wk). Cubes were formulated to be isocaloric and isonitrogenous compared with molasses/urea (75% TDN, 20% CP; DM basis). Weekly supplement amount was divided in half and offered every Monday and Thursday. Cow BCS: did not differ among treatments from d 0 to 74 (P ≥ 0.56); was greater at calving (d 161) for MOL-Y and CUB-Y vs. MOL-W cows (P ≤ 0.05); and was greatest, intermediate, and least at start of breeding season (d 217) for MOL-Y, CUB-Y, and MOL-W cows (P ≤ 0.05), respectively. Liver concentrations for Co, Se, and Cu on d 122 and 217 were greater (P ≤ 0.02) for CUB-Y vs. MOL-W and MOL-Y cows. Calving date, percentage of pregnant cows on d 360, and calf birth BW, pre-weaning ADG, and BW at weaning did not differ (P ≥ 0.14) among treatments. Therefore, year-round supplementation of liquid molasses/urea and range cubes enhanced cow BCS at calving and start of breeding season but did not impact subsequent reproductive performance of cows and calf weaning weights than conventional winter molasses/urea supplementation of cows

PSI-18 Effects of supplementing polyunsaturated fatty acids during late gestation on performance of fall-calving cows

Abstract The objective was to determine the effects of supplementing calcium salts of PUFA or SFA + MUFA during late gestation on performance of fall-calving beef cows through calving. Mature, Simmental x Angus cows confirmed pregnant to a synchronized artificial insemination (AI) and fetal sexed were selected prior to the start of the experiment. At 200 d of gestation, cows (n = 96; BW = 603 ± 72 kg) were stratified by age, AI service sire, fetal sex and BW and allotted to 8 groups. Groups were randomly assigned to 1 of 2 treatments (4 groups per treatment): SFA + MUFA (0.155 kg of EnerGII per cow per day on a DM basis) and PUFA (0.08 kg of Strata and 0.08 kg of Prequel per cow per day on a DM basis). The SFA + MUFA supplement included palmitic and oleic acid. The PUFA supplement included eicosapentaenoic acid, docosahexaenoic acid, and linoleic acid. All cows grazed endophyte-infected tall fescue and were supplemented 2 kg DM per cow per d of soybean hulls for 78 d during late gestation in addition to their treatment supplement. Body condition score and BW were collected at trial initiation, during supplementation, before calving, and after calving. Pen was the experimental unit and BW, BCS, and calf BW were analyzed using the MIXED procedure of SAS. The BW and BCS at trial initiation, during supplementation, before calving, and after calving of the cows supplemented PUFA were not different (P ≥ 0.38) than the BW and BCS of cows supplemented SFA + MUFA. Calf birth BW from cows supplemented with PUFA were not different (P = 0.87) than calf birth BW from cows supplemented with SFA + MUFA. Supplementing cows PUFA during late gestation in fall-calving cows did not affect BW, BCS or calf birth BW.

Effects of extended-release eprinomectin on fescue toxicosis, performance, and reproduction on fall-calving beef cows.

The objective of this experiment was to evaluate effects of extended-release eprinomectin on fescue toxicosis and impacts on performance and reproduction in fall-calving beef cows. Fall-calving Angus × Simmental multiparous cows [n = 335; age = 5.8 ± 2.1 yr; 586.5 ± 6.0 kg body weight (BW); 5.48 ± 0.05 body condition score (BCS)] were stratified by BW, age, and BCS and randomly assigned to one of three treatments. Treatments included a spring injection of extended-release eprinomectin (SERE) on day 0, a fall injection of extended-release eprinomectin injection (FERE) on day 84, and a saline control (CON). All treatments were administered at a rate of 1 mL/50 kg BW. Prior to the experiment, all cows were treated with oral fenbendazole to minimize parasite load. Cows grazed endophyte-infected tall fescue. Hair coat score (HCS), BW, and BCS were recorded on all cattle. Fecal egg count (FEC), respiration rate (RR), horn fly and tick count, hematocrit (% packed cell volume, PCV), and serum prolactin were analyzed on a subset of cows (35/treatment). On day 194, cows were artificially inseminated (AI) and 11 d following AI were exposed to bulls for 51 d. Milk production was estimated on day 210 on a subset of 85 cow–calf pairs (28–29/treatment). There was a tendency for a treatment × time interaction (P = 0.07) for FEC likely driven by an increase in FEC of the CON cattle at day 126 compared to SERE and FERE. There was a tendency for a treatment × time interaction (P = 0.06) for cow BW, largely driven by time differences; however, there was no effect of treatment (P = 0.84) on BW. There was no difference (P ≥ 0.13) in cow PCV, fly and tick count, BCS, HCS, RR, and serum prolactin throughout the experiment. Additionally, there was no difference (P ≥ 0.46) in Julian calving date, calf birth BW, or milk production between treatments. Interestingly, heifer calves born to FERE dams tended to have greater (P = 0.06) weaning BW compared to heifer calves born to CON dams. In addition, there was no difference (P ≥ 0.17) in heat patch scores, AI conception rates, or overall pregnancy rates between treatments. Extended-release eprinomectin did not impact cow growth performance, reproductive performance or fescue toxicity symptoms when grazing endophyte-infected tall fescue; however, calf weaning BW tended to be improved.

Effects of polyunsaturated fatty acids supplementation on reproductive parameters associated with the performance of suckled beef cows

To evaluate the effects of a polyunsaturated fatty acids (PUFA) supplement on reproductive parameters of suckled beef cows, two experiments were conducted. In Experiment (Exp.) 1, 60 primiparous cows were randomly assigned to one of two treatments: CTRL – 1.36 kg/day of corn gluten feed (CGF) and MEGR – 1.36 kg/day of CGF and 0.23 kg/day of calcium salts of soybean oil. Supplementation occurred from 30 days before fixed-time artificial insemination (TAI) until 7 days post-TAI. The expression of interferon-stimulated genes (ISG) was measured on days 18 and 21. Pregnancy rates were diagnosed on days 30 and 100. Treatment altered plasma fatty acid profile (P<0.05), however, did not change cow BW (P=0.52) or body condition score (BCS) (P=0.52). Treatment did not alter (P=0.12) pregnancy rates to TAI or final pregnancy rates (P=0.56). Treatments did not impact messenger RNA (mRNA) expression of the ISG OAS1 or MX2 on days 18 (P=0.67; P=0.96, respectively) or 21 (P=0.72; P=0.17, respectively). Length of gestation was greater (P=0.02) for MEGR, however, treatments did not alter calf birth weight (P=0.20). In Exp. two, 66 multiparous cows were assigned to one of two treatments: MEG – 0.65 kg/day of CGF+0.23 kg/day of calcium salts of palm oil and MEGR – 0.65 kg/day of CGF+0.23 kg/day of Ca salts of soybean oil. Cows were supplemented from 30 days prepartum to 30 days postpartum. On day 35 after TAI, pregnancy status, embryo crown-to-rump length (CRL), and plasma concentrations of pregnancy-specific protein-B (PSPB) were evaluated. Treatment altered plasma fatty acid profile (P<0.05). In addition, cows from the MEG treatment had greater BW (P<0.01) and BCS (P<0.01) than those in the MEGR treatment, as well as heavier calves at weaning (P=0.03). Treatment did not affect resumption of estrous cycle (P=0.29). There were no differences in pregnancy rates to TAI (P=0.87) or final pregnancy rates (P=0.29). No differences between treatments were detected on CRL (P=0.24) and plasma concentrations of PSPB (P=0.46). Birth weight (P=0.12) and calving distribution (P=0.52) were not altered. We concluded that PUFA supplementation altered plasma fatty acid profile, however, did not impact the remaining reproductive parameters evaluated.

PSVIII-23 Late-Breaking: Effect of reproductive tract size and position scores and estrus on reproductive performance in beef cows.

PSVIII-23 Late-Breaking: Effect of reproductive tract size and position scores and estrus on reproductive performance in beef cows.

54 Effects of copper, zinc, and manganese source and concentration during late gestation on beef cow performance, fetal growth, and mineral status of cows and neonatal calves.

54 Effects of copper, zinc, and manganese source and concentration during late gestation on beef cow performance, fetal growth, and mineral status of cows and neonatal calves.

429 Effects of endophyte strain on performance of beef cows grazed on summer stockpiled tall fescue pastures.

429 Effects of endophyte strain on performance of beef cows grazed on summer stockpiled tall fescue pastures.

Reproductive performance of Bos indicus beef cows treated with different doses of equine chorionic gonadotropin at the end of a progesterone-estrogen based protocol for fixed-time artificial insemination

Two experiments were performed to evaluate the reproductive performance of zebu beef cows treated with different doses of eCG at the end of a progesterone (P4)/estrogen based protocol for timed artificial insemination (TAI). In Experiment 1, suckling Bos indicus Nelore cows (n = 261) received, on day 0, a progesterone (P4) intravaginal device (PD) and an injection of 1 mg estradiol benzoate (EB). On day 8, the PD was removed, 500 μg of cloprostenol was injected, and cows were assigned to one of the following groups: Control (no treatment), 300 (300 IU of eCG), 600 (600 IU of eCG), and 900 (900 IU of eCG). On day 9, all cows received 1 mg EB and TAI performed 54–56 h after cloprostenol injection. A pregnancy diagnosis was done by ultrasound scanning 40 days after TAI, and the number of fetuses and calves was recorded at pregnancy diagnosis and at birth. More cows treated with eCG displayed estrus within 48 h after removal of the PD (42.3% vs. 11.6%, P < 0.01), and ovulated more than one follicle (42%, 58/138 vs. 1.8%, 1/54; P < 0.01). This effect on ovulation rate was dose dependent (P < 0.05). The pregnancy rate was affected only by cow parity (primiparous, 25.3% vs. multiparous, 48.9%; P < 0.01). Twin pregnancy was higher (P < 0.01) in cows treated with eCG (42%, 58/138) than controls (0%, 0/54). However, few cows (33.3%) were able to keep both fetuses intact until birth. For evaluation of ovarian characteristics by B-mode and Doppler ultrasonography, 43 Nelore cows were submitted In Experiment 2 to the same four groups described in Experiment 1. Although no difference (P > 0.1) was observed for size and blood perfusion in the pre-ovulatory follicles, corpus luteum was larger and with greater blood perfusion (P < 0.05) in eCG-treated cows. In conclusion, eCG increased the number of double/multiple ovulations in a dose-dependent manner, induced larger and more vascularized corpora lutea, but did not affect the fertility of cyclic or anestrous cows. Although eCG results in twin pregnancies, most of cows underwet embryo/fetus loss and birth a single calf.

109 Effects of Year-Round Supplementation of Sugarcane Molasses and Range Cubes on Growth Performance and Physiological Parameters of Pregnant Beef Cows.

109 Effects of Year-Round Supplementation of Sugarcane Molasses and Range Cubes on Growth Performance and Physiological Parameters of Pregnant Beef Cows.

23 Effects of Timing of Weaning on Calf Performance and Maintenance Energy Requirements in Primiparous Beef Cows.

23 Effects of Timing of Weaning on Calf Performance and Maintenance Energy Requirements in Primiparous Beef Cows.

Impact of vaccination on the reproductive performance of multiparous Nellore cows

ABSTRACT: Two experiments were conducted to evaluate the impact of two vaccines on the reproductive performance of multiparous beef cows in Mato Grosso do Sul, Midwest Brazil. In Experiment 1,765 calved multiparous Nellore cows were subjected to the same fixed-time artificial insemination (FTAI) protocol and rebred. Ultrasound pregnancy diagnosis was performed 30 and 90 days post-FTAI (DPI). Rates of pregnancy and pregnancy loss were determined for three periods: from 30 to 90 DPI, from 30 DPI to calving, and from 90 DPI to calving. The cows were assigned to three groups with different vaccination protocols - namely, Group VACMULT (n=250): vaccine against bovine herpesvirus 1 (BoHV-1), bovine viral diarrhea virus (BVDV), and leptospirosis; Group VACL (n=245): vaccine against leptospirosis alone; Group NOVAC (n=270): no vaccination. Serum antibody titers for BoHV-1, BVDV, and leptospirosis, measured in 57 cows from each group indicated active infection, suggesting circulation of these pathogens in the herd. No differences in pregnancy rates were observed across groups. Pregnancy loss rates did not differ significantly across groups within any of the periods investigated (30 to 90 DPI, 30 DPI to calving, or 90 DPI to calving). In Experiment 2, two vaccination protocols for each vaccine were investigated. Group VACGEST was vaccinated on day zero of FTAI (D0) and again 30 days post-FTAI (30 DPI). Group VACPREV was vaccinated on D0 and again on the day of insemination (D11). No significant difference was observed between groups, or significant gestational loss in the group that received the second vaccine on the day of insemination. The results revealed that neither vaccine interfered with the reproductive performance of multiparous cows. No differences were observed between vaccination carried out on both D0 and D11 and that performed on both D0 and D30. The performance of the IBR/BVDV/Leptospirosis vaccine on the day of the artificial insemination did not cause adverse effects on the reproductive parameters.