Performance and metabolic evaluation in primiparous beef cows under grazing at different breeding ages.

We aimed to evaluate the metabolic and performance differences in primiparous Nellore cows, which became pregnant at 14 or 24-mo old. Thirty-eight cows with 202 ± 5 days of gestation were divided into two treatments according to breeding age: 14 or 24-mo. Cows were evaluated for body weight (BW), body condition score (BCS), carcass characteristics, milk yield, calves's performance, and blood characteristics. The animals were managed in eight paddocks under continuous grazing and evaluated from 90 d before parturition until 240 d after calving. We observed an interaction between breeding age and time (P < 0.01) for cow BW. Both breeding age categories experienced BW loss during parturition, with a concurrent decrease in BCS. However, following their first calving, the BW of 24-mo cows remained stable (P > 0.05), whereas 14-mo cows exhibited a gradual recovery in BW after parturition (P < 0.05). Milk yield was greater in 24-mo animals (P < 0.01), but decreased with increasing milking days (p < 0.05) for both groups. The weight gain calves from the heifers bred at 24-mo was greater (P < 0.01), which reflected in greater BW at weaning. The beta-hydroxybutyrate (ß-OHB) concentration was greater before calving and a marked decrease after parturition (P < 0.05). The 24-mo cows had greater blood ß-OHB (P < 0.01) at prepartum and 30 days after calving. Blood progesterone was greater in 24-mo cows (P > 0.05). Primiparous beef cows that conceive at either 14 or 24-months of age exhibit distinct nutritional requirements and metabolic profiles. Notably, cows that conceive at 24-months of age have the advantage of weaning heavier calves and displaying a more consistent reproductive cycle following their first calving than cows that conceive at 14-months.

Effects of supplementing narasin to Bos indicus heifers during late-gestation and lactation on development of the offspring.

This experiment evaluated the effects of supplementing narasin during late-gestation and lactation on productive and physiological responses of Bos indicus beef heifers and their offspring. Pregnant, nulliparous Nelore heifers (N = 88) that conceived under the same fixed-time artificial insemination protocol and to the same sire were used. Heifers were ranked by maternal ability genomic score, body weight (BW) and body condition score (BCS) and allocated to 44 drylot pens (2 heifers per pen; 10 × 25 m). Pens were ranked by these traits and alternatively assigned to receive (NAR) or not (CON) 0.260 mg of narasin/kg of heifer BW daily (Elanco Saúde Animal, São Paulo, Brazil). Narasin was mixed into a supplement offered at 0.30% of heifer BW from day 0 until heifers weaned their calves (day 316), whereas CON heifers received the same supplement without narasin addition. Heifers received Urochloa brizantha hay and water for ad libitum consumption (days 0 to 316) and calved between days 97 to 112 of the experiment. After calving, heifers and offspring had access to hay and supplement; hence, supplements and narasin were offered according to heifer + calf BW beginning on day 162. No treatment differences were detected (P ≥ 0.18) for heifer BW and BCS during the experiment, although BW loss from day 0 to calving was less (P = 0.04) in NAR compared to CON heifers. Hay intake during the experiment did not differ (P = 0.79) between treatments. Serum IGF-I concentrations were greater (P = 0.05) for NAR heifers on day 60 of the experiment and did not differ (P ≥ 0.28) between treatments 24 h and 30 d after calving (treatment × day interaction; P = 0.04). No treatment effects were detected (P ≥ 0.58) for calf birth BW. Serum concentrations of total protein 24 h after birth were greater (P = 0.04) in calves from NAR compared with CON heifers, and a tendency (P = 0.10) for a similar outcome was noted for serum IgG concentrations. Diarrhea incidence did not differ (P = 0.16) between treatments, although the number of total diarrhea cases per calf were greater (P = 0.03) in the CON offspring. Growth rate of calves from NAR heifers tended (P = 0.08) to be greater, resulting in heavier calves at weaning (P ≤ 0.04) compared with CON offspring. Collectively, these outcomes indicate narasin supplementation to beef heifers as a nutritional alternative to improve cow-calf productivity via developmental programming effects during gestation, as well as direct consumption by their nursing offspring.

Characterization of the cervicovaginal microbiota of female beef cattle harboring Campylobacter fetus subsp. venerealis using 16S rDNA gene sequencing.

Bovine genital campylobacteriosis (BGC) is a leading cause of return to estrus in cows. The etiologic agent, Campylobacter fetus subsp. venerealis (Cfv) is transmitted by venereal route. Hence, the surrounding reproductive tract microenvironment could play a role in return to estrus in cows. The presence of Cfv in cervicovaginal mucus of Angus breed females provide three experimental groups, which were subject to bacteriome analyses: 10 Cfv-positive cows (CVP), 10 Cfv-negative cows (CVN), and 10 nonsexually active heifers (NSA). Cows with return to estrus showed higher bacterial richness than NSA. Beta diversity analysis showed a significant difference (P = 0.006) in bacterial composition among the three groups analyzed (CVP, CVN, and NSA). However, no significant difference was found when comparing the CVP versus CVN groups. Ureaplasma and Pseudomonas were the genera most frequently observed in NSA, being Ureaplasma the predictor genus to that group, whereas Alistipes, Bacteroides, Rikenellaceae_RC9_gut_group, UCG-005, and UCG-10 were both significantly more abundant and predictors genera in cows with return to estrus. Our results provide an overview of the cervicovaginal bacterial microbiota in cows harboring Cfv and improve the knowledge of the pathogenesis of BGC.

Application of PGF2α at the moment of fixed-time artificial insemination in crossbred beef cows.

Although studies have shown positive effects of gonadotropin releasing hormone (GnRH) or prostaglandin F2α (PGF2α) at the moment of fixed-time artificial insemination (FTAI) in the conception rate (CR) of cattle, its effects on treatments based on progesterone (P4) and estradiol benzoate (EB) is still not conclusive. The objective of this study was (1) to evaluate the effect of a PGF2α analogue at FTAI in the CR of crossbred beef cows submitted to a 11d FTAI protocol based on P4 and EB; and (2) to describe the CR between PGF2α-treated and control cows in different body condition scores (BCS) and parity categories. Crossbred (½ Nellore and ½ Angus) beef cows were submitted to a synchronization protocol and randomly assigned into 2 groups: Control (n = 163), at FTAI cows received 2 mL of saline solution as a placebo, and PGF2α (n = 163), at FTAI cows were treated with PGF2α analogue (10 mg of dinoprost tromethamine). Pregnancy diagnosis was performed 33d post-FTAI. Binary logistic regression model was used to analyze the effect of PGF2α treatment on CR. There was no difference in CR between PGF2α and control groups (P > 0.05; odds ratio (OR) = 0.92; confidence interval (CI) = 0.59-1.4). A greater CR was found in heifers (P = 0.0006, OR = 2.65, CI = 1.61 - 4.38) and multiparous (P = 0.0006, OR = 2.12, CI = 1.04 - 4.3) when compared to primiparous cows. Cows with low BCS (4; 9-point scale) showed lower CR when compared with moderate BCS (5-6; 9-point scale) (P < 0.05; OR = 0.10; CI = 0.06 - 0.18). There was no numerical difference on CR between PGF2α-treated and control cows in different BCS and parity categories. The results suggested that the CR in this study was not influenced by 10 mg PGF2α analogue at FTAI.

Effects of Maternal Protein Supplementation at Mid-Gestation of Cows on Intake, Digestibility, and Feeding Behavior of the Offspring.

This study aimed to assess the effects of maternal protein supplementation and offspring sex (OS) on the intake parameters of the offspring. Forty-three Tabapuã cows were randomly allocated in the following treatments: protein supplementation (PS) during days 100-200 of gestation (RES, 5.5% total crude protein (CP), n = 2, or CON, 10% total CP, n = 19) and OS (females, n = 20; males, n = 23). The offspring were evaluated during the cow-calf (0-210 days), backgrounding (255-320 days), growing 1 (321-381 days), and growing 2 (382-445 days) phases. The CON offspring tended to present higher dry matter intake (DMI) at weaning (p = 0.06). The CON males presented lower digestibility of major diet components in the growing 2 phase (p ≤ 0.02). The CON offspring spent 52% more time per day eating supplements at 100 days and 17% less time in idleness at 210 days. The CON males spent 15 min more per day ruminating than RES males in the feedlot phase (p = 0.01). We concluded that protein supplementation over gestation alters the offspring feed intake pattern as a whole, while protein restriction promotes compensatory responses on nutrient digestibility in males.

Influence of body condition score and its change after parturition on pregnancy rates to fixed-timed artificial insemination in Bos indicus beef cows.

This experiment evaluated pregnancy rates to fixed-time artificial insemination (FTAI) in Bos indicus beef cows according to their body condition score (BCS) at calving and subsequent change until 30 days after FTAI. Non-pregnant, suckling Nelore cows (n = 593 primiparous, 461 secundiparous, and 893 multiparous) were evaluated for BCS at calving and FTAI, and at 30 days after FTAI when cow pregnancy status was verified. Cow BCS at calving was subtracted from BCS recorded at pregnancy diagnosis, and cows classified as those that lost BCS (L), maintained BCS (M), or gained BCS (G) during this period. Cows that calved with BCS ≥ 5.0 had greater (P < 0.01) BCS throughout the experiment, and greater (P < 0.01) pregnancy rates to FTAI compared with cows that calved with BCS < 5.0 (54.8 vs. 34.2%). Pregnancy rates to FTAI were greater (P < 0.01) for G and M cows compared with L cows (50.0%, 47.5%, and 36.0%, respectively), and similar (P = 0.46) between G and M cows. Moreover, pregnancy rates to FTAI in G cows that calved with BCS < 5.0 were less compared with L (tendency; P = 0.08) and M cows (P < 0.01) that calved with BCS ≥ 5.0 (42.2%, 48.3%, and 58.3%, respectively). In summary, pregnancy rates to FTAI were greater in B. indicus cows that calved with a BCS ≥ 5.0 regardless of parity and post-calving BCS change, and greater in M and G cows within those that calved with BCS < 5.0 or ≥ 5.0.

Application of PGF2α at the moment of fixed-time artificial insemination in crossbred beef cows

Although studies have shown positive effects of gonadotropin releasing hormone (GnRH) or prostaglandin F2α (PGF2α) at the moment of fixed-time artificial insemination (FTAI) in the conception rate (CR) of cattle, its effects on treatments based on progesterone (P4) and estradiol benzoate (EB) is still not conclusive. The objective of this study was (1) to evaluate the effect of a PGF2α analogue at FTAI in the CR of crossbred beef cows submitted to a 11d FTAI protocol based on P4 and EB; and (2) to describe the CR between PGF2α-treated and control cows in different body condition scores (BCS) and parity categories. Crossbred (½ Nellore and ½ Angus) beef cows were submitted to a synchronization protocol and randomly assigned into 2 groups: Control (n = 163), at FTAI cows received 2 mL of saline solution as a placebo, and PGF2α (n = 163), at FTAI cows were treated with PGF2α analogue (10 mg of dinoprost tromethamine). Pregnancy diagnosis was performed 33d post-FTAI. Binary logistic regression model was used to analyze the effect of PGF2α treatment on CR. There was no difference in CR between PGF2α and control groups (P > 0.05; odds ratio (OR) = 0.92; confidence interval (CI) = 0.59-1.4). A greater CR was found in heifers (P = 0.0006, OR = 2.65, CI = 1.61 - 4.38) and multiparous (P = 0.0006, OR = 2.12, CI = 1.04 - 4.3) when compared to primiparous cows. Cows with low BCS (4; 9-point scale) showed lower CR when compared with moderate BCS (5-6; 9-point scale) (P < 0.05; OR = 0.10; CI = 0.06 - 0.18). There was no numerical difference on CR between PGF2α-treated and control cows in different BCS and parity categories. The results suggested that the CR in this study was not influenced by 10 mg PGF2α analogue at FTAI.(AU)

Osteomalacia as a result of phosphorus deficiency in beef cattle grazing subtropical native pastures in Uruguay.

We investigated 2 outbreaks of osteomalacia as a result of phosphorus (P) deficiency in herds of lactating beef cows grazing subtropical native pastures in Uruguay. Cows exhibited pica, difficulty to stand and walk, rib fractures, and body weight loss even with adequate forage availability. Osteopenia and severe osteomalacia were observed on gross and histologic examination. The concentrations of bicarbonate-extractable P in soil (4.0, 4.1 mg P/kg), total P in pasture (0.9, 1.1 g P/kg), inorganic P in serum (1.0, 0.71 mmol P/L), and P in bone (73 mg P/mL) were all low. Although injectable and mineral salt supplements provided additional P in both outbreaks, these supplementary amounts were insufficient to prevent P deficiency. The P ingested by the cows from the pasture and supplements would have provided 20-55% of their daily P requirements of ~21 g P/d. Osteomalacia occurred in cattle at the 2 ranches as a result of severe P deficiency in the soil and forage, and inadequate P supplementation. Following diagnosis, control of P deficiency in beef cattle requires estimation of the amount of pasture P ingested and provision of sufficient additional supplementary P to meet the animals' requirements.

Seasonal Effect on Feed Intake and Methane Emissions of Cow-Calf Systems on Native Grassland with Variable Herbage Allowance.

The aim of this study was to measure methane emissions (CH4) and herbage intake, and, on the basis of these results, obtain the methane yield (MY, methane yield as g CH4/kg dry matter intake (DMI) and Ym, methane yield as a percentage of Gross Energy intake), from beef cows grazing on native grasslands. We used forty pregnant heifers, with two treatments of herbage allowance (HA) adjusted seasonally (8 and 5 kg dry matter (DM)/kg cattle live weight (LW), on average), during autumn, winter and spring. Methane emissions (207 g CH4/d), organic matter intake (OMI, 7.7 kg organic matter (OM)/d), MY (23.6 g CH4/kg DMI) and Ym (7.4%), were similar between treatments. On the other hand, all variables had a marked increase in spring (10.8 kg OM/d and 312 g CH4/d), except for Ym. The methane emission factor from Intergovernmental Panel on Climate Change (IPCC) Tier 2 estimated with these results was 78 kg CH4/head/year. The results show that methane emissions and intake were influenced by the season, but not by the HA analyzed in this study. This information for cow-calf systems in native grasslands in Uruguay can be used in National greenhouse gases (GHG) inventories, representing a relevant contribution to global GHG inventories.

Administering an additional prostaglandin F2α injection to Bos indicus beef cows during a treatment regimen for fixed-time artificial insemination.

Two experiments were conducted to evaluate if an additional prostaglandin F2α (PG) injection during an estradiol-based estrous synchronization treatment regimen affects pregnancy rates resulting from fixed-time artificial insemination (FTAI) in Nelore cows. In Experiment 1, 1039 cows were administered estradiol benzoate and an intravaginal progesterone releasing device (CIDR) on d -11, an injection of PG on d -4, with CIDR removal and administration of estradiol cypionate and eCG occurring on d -2, and FTAI on d 0. Cows were administered an additional injection of PG (PG2) or saline (PG1) on d -2. Percentage pregnancy per FTAI on d 30 was greater (P = 0.01) in cows of the PG2 than PG1 group (54.5 % and 46.6 %, respectively). In Experiment 2, there was use of the same treatment regimen for estrous synchronization of 934 cows as that for Experiment 1 followed by FTAI, with there being diagnosis of whether cows had or did not have a corpus luteum on d -4. Response to estrous synchronization, largest follicle diameter at FTAI, and pregnancy per FTAI were greater (P ≤ 0.05) in cows of the PG2 than PG1 group with a body condition score (BCS) < 5.0 at FTAI (81.2 % and 72.6 %, 11.9 and 11.2 mm, 55.5 and 45.6 %; respectively). These treatment responses did not differ (P ≥ 0.18) in cows with BCS ≥ 5.0. Collectively, results indicate that treatment with PG2 increased pregnancy per FTAI in B. indicus cows deficient in body energy reserves, by enhancing follicle development and estrous synchronization response.

Effect of temperature - humidity index on the onset of post- partum ovarian activity and reproductive behavior in Bos indicus cows.

The effect of climatic factors on ovarian activity and reproductive behavior (RB) was evaluated in 46 Bos indicus cows kept under grazing conditions. Temperature-humidity index (THI) was used as an indicator of stress and divided in alert, damage and emergency levels. Fat thickness (FAT) was taken during the last trimester of gestation (LTG) to approximately 90d postpartum (PP). At 30d PP animals received a progesterone (P4)-releasing device (CIDR) which was withdrawn 9d later. Ovarian activity was assessed by blood progesterone on days 21, 24, 27, 30, 49, 51, and 54 PP. Animals were divided into three groups, higher, and moderate RB and non-behavior. Sixty percent presented a THI >74 increasing dramatically from June to September up to >78. During LTG, animals lost 27% of their body reserves contrasting to PP where an increase of 2.6% (P=0.002) was observed. The percentages of cyclic and non-cyclic animals were 57 and 43%, respectively (P> 0.05). Seventy-two percent displayed RB and 28% were non-behavior (P<0.05). A negative correlation (r = -0.307; P = 0.038) between THI and RB, and a positive correlation (r = 0.427; P = 0.003) between the onset of ovarian activity and RB were observed. Differences in THI during the LTG (P<0.01) were observed between cyclic and non-cyclic animals. Non-behavior cows in the LTG had a higher THI (P <0.05). High levels of THI have a negative effect on the resumption of ovarian activity and RB in Bos indicus especially if high THI occurs during the last trimester of gestation.

Influence of an immune-modulatory feed supplement on performance and immune function of beef cows and calves preweaning.

The ability to positively alter immune and stress response with nutritional compounds is of great interest and importance to the beef industry. There is a proprietary product (OmniGen-AF [OG]; Phibro Animal Health, Quincy, IL) reported to have performance-enhancing benefits by altering animal response to stress and immune challenges. The objective of this 2-yr research project was to study the effect of supplementing OG to beef cows and their calves on breeding and growth performance. One hundred and twelve multiparous beef cows and 48 primiparous cows were randomly assigned to treatment in year 1; control (CON, no OG; n = 56 multiparous and 24 primiparous) or treatment (OG fed at 8.8 g/100 kg body weight [BW]; n = 56 multiparous and 24 primiparous). Multiparous cows (mean ± SD = 6.4 ± 0.4 yr; BW = 589 ± 9.2 kg; body condition score [BCS] 6.2 ± 0.07) were used in both years of the experiment and primiparous cows (mean ± SD = 2.1 ± 0.04 yr of age, weighed 400 ± 7.5 kg, and BSC of 5.6 ± 0.06) were only used in the first year of the experiment. CON and OG supplements were offered over two production cycles beginning in December approximately 60 d prior to projected calving through pre-breeding in May of each year. Calves from treatment cows were offered treatments in a creep supplement limited to a daily rate of 1% as-fed of BW prorated for 3-d/wk feeding from mid-July through weaning with OG offered at 8.8 g/100 kg BW. Primiparous cow's BW, BCS, and calf performance were not affected by treatment (P ≥ 0.15) in year 1. BW of multiparous OG cows tended (P = 0.10) to be heavier at weaning in year 1 and was greater (P = 0.05) at the onset of the experiment in year 2. Body condition of OG cows was greater (P ≤ 0.02) at weaning in both years 1 and 2, as well as at the onset of the experiment in year 2. Calves fed OG from the mature cows gained more (P = 0.05) BW during the creep feeding period than CON. Core body temperatures of OG heifers measured during the late summer with intravaginal temperature data loggers tended (P ≤ 0.10) to be less at 1400 and 1700 hours and were less (P = 0.05) at 1800 hours than CON heifers. Feeding OG did not result in changes (P = 0.25) in serum titer response to the BVD virus of calves during year 2. The results of the current experiment indicate feeding OG to beef cows and calves can result in improvement in BCS of cows, enhance weight gain of calves preweaning, and reduce heat loads in heifer calves during the late summer.

Effect of temperature humidity index on the onset of post- partum ovarian activity and reproductive behavior in Bos indicus cows

The effect of climatic factors on ovarian activity and reproductive behavior (RB) was evaluated in 46 Bos indicus cows kept under grazing conditions. Temperature-humidity index (THI) was used as an indicator of stress and divided in alert, damage and emergency levels. Fat thickness (FAT) was taken during the last trimester of gestation (LTG) to approximately 90d postpartum (PP). At 30d PP animals received a progesterone (P4)-releasing device (CIDR) which was withdrawn 9d later. Ovarian activity was assessed by blood progesterone on days 21, 24, 27, 30, 49, 51, and 54 PP. Animals were divided into three groups, higher, and moderate RB and non-behavior. Sixty percent presented a THI >74 increasing dramatically from June to September up to >78. During LTG, animals lost 27% of their body reserves contrasting to PP where an increase of 2.6% (P=0.002) was observed. The percentages of cyclic and non-cyclic animals were 57 and 43%, respectively (P> 0.05). Seventy-two percent displayed RB and 28% were non-behavior (P<0.05). A negative correlation (r = -0.307; P = 0.038) between THI and RB, and a positive correlation (r = 0.427; P = 0.003) between the onset of ovarian activity and RB were observed. Differences in THI during the LTG (P<0.01) were observed between cyclic and non-cyclic animals. Non-behavior cows in the LTG had a higher THI (P <0.05). High levels of THI have a negative effect on the resumption of ovarian activity and RB in Bos indicus especially if high THI occurs during the last trimester of gestation.(AU)

Effect of temperature – humidity index on the onset of post- partum ovarian activity and reproductive behavior in Bos indicus cows

The effect of climatic factors on ovarian activity and reproductive behavior (RB) was evaluated in 46 Bos indicus cows kept under grazing conditions. Temperature-humidity index (THI) was used as an indicator of stress and divided in alert, damage and emergency levels. Fat thickness (FAT) was taken during the last trimester of gestation (LTG) to approximately 90d postpartum (PP). At 30d PP animals received a progesterone (P4)-releasing device (CIDR) which was withdrawn 9d later. Ovarian activity was assessed by blood progesterone on days 21, 24, 27, 30, 49, 51, and 54 PP. Animals were divided into three groups, higher, and moderate RB and non-behavior. Sixty percent presented a THI >74 increasing dramatically from June to September up to >78. During LTG, animals lost 27% of their body reserves contrasting to PP where an increase of 2.6% (P=0.002) was observed. The percentages of cyclic and non-cyclic animals were 57 and 43%, respectively (P> 0.05). Seventy-two percent displayed RB and 28% were non-behavior (P<0.05). A negative correlation (r = -0.307; P = 0.038) between THI and RB, and a positive correlation (r = 0.427; P = 0.003) between the onset of ovarian activity and RB were observed. Differences in THI during the LTG (P<0.01) were observed between cyclic and non-cyclic animals. Non-behavior cows in the LTG had a higher THI (P <0.05). High levels of THI have a negative effect on the resumption of ovarian activity and RB in Bos indicus especially if high THI occurs during the last trimester of gestation.

Bovine semen thermoresistance tests and their correlation with pregnancy rates after fixed-time artificial insemination / Testes de termorresistência do sêmen bovino e sua correlação com taxas de prenhez após inseminação artificial em tempo fixo

The objective of the study was to determine whether or not there is a correlation between thermoresistance tests (TT) after semen thawing and pregnancy rate (PR) after fixed-time artificial insemination (FTAI). Four different TT were performed on ten samples used for AI; a rapid test (RTT) (30min / 46°C) and three slow tests (STT): STT1 (60min/38°C), STT2 (180min/38°C), and STT3 (300min/38°C). Two hundred and fifteen multiparous crossbred cows were submitted to FTAI under the following protocol: on day zero (d0) the animals received a P4 device +EB; on d7 PGF2α; on d8 P4 was removed and eCG+EC were administered; IATF was performed on d10. Three gestational diagnoses (G D) were performed on d40, d70 and d120. The mean sperm motility (%) in RTT and STTs were 19.84±6.13, 28.55±10.48, 17.62±5.87 and 8.63±3.46, respectively, and TP in the three DG 61.86%, 57.67%, and 55.81%, respectively. Through Person test a significant negative correlation (P< 0.05) was found between STT2 and PR at 60 days (r= -0.644) and between STT3 and all TPs (r= -0.774, -0.752, 0.748). It was concluded that TT parameters are not able to determine correlation between semen quality and TP.(AU)

O objetivo do presente estudo foi determinar se há ou não correlação entre testes de termorresistência (TT) após descongelamento do sêmen e taxa de prenhez (TP) após inseminação artificial em tempo fixo (IATF). Quatro diferentes TT foram realizados nas 10 amostras utilizadas para a IA; um teste rápido (RTT) (30min/46°C) e três testes lentos (STT): STT1 (60min/38°C), STT2 (180min/38°C) e STT3 (300min/38°C). Duzentas e quinze vacas cruzadas multíparas foram submetidas à IATF sob o seguinte protocolo: no dia zero (d0), os animais receberam um dispositivo de P4+EB; em d7, PGF2α; em d8, retirou-se P4 e eCG+EC administrados; no d10, foi realizada IATF. Três diagnósticos gestacionais (DG) foram feitos, em d40, d70 e d120. As médias de motilidade espermática (%) em RTT e STTs foram 19,84±6,13, 28,55±10,48, 17,62±5,87 e 8,63±3,46, respectivamente, e TP nos três DG 61,86%, 57,67% e 55,81%, respectivamente. Por meio do teste de Person, uma correlação negativa significativa (P<0,05) foi encontrada entre os resultados de STT2 e PR aos 60 dias (r=-0,644) e entre STT3 e todas TPs (r=-0,774, -0,752 e -0,748). Concluiu-se que parâmetros de TT não são capazes de determinar correlação entre qualidade do sêmen e TP.(AU)

Bovine semen thermoresistance tests and their correlation with pregnancy rates after fixed-time artificial insemination / Testes de termorresistência do sêmen bovino e sua correlação com taxas de prenhez após inseminação artificial em tempo fixo

The objective of the study was to determine whether or not there is a correlation between thermoresistance tests (TT) after semen thawing and pregnancy rate (PR) after fixed-time artificial insemination (FTAI). Four different TT were performed on ten samples used for AI; a rapid test (RTT) (30min / 46°C) and three slow tests (STT): STT1 (60min/38°C), STT2 (180min/38°C), and STT3 (300min/38°C). Two hundred and fifteen multiparous crossbred cows were submitted to FTAI under the following protocol: on day zero (d0) the animals received a P4 device +EB; on d7 PGF2α; on d8 P4 was removed and eCG+EC were administered; IATF was performed on d10. Three gestational diagnoses (G D) were performed on d40, d70 and d120. The mean sperm motility (%) in RTT and STTs were 19.84±6.13, 28.55±10.48, 17.62±5.87 and 8.63±3.46, respectively, and TP in the three DG 61.86%, 57.67%, and 55.81%, respectively. Through Person test a significant negative correlation (P< 0.05) was found between STT2 and PR at 60 days (r= -0.644) and between STT3 and all TPs (r= -0.774, -0.752, 0.748). It was concluded that TT parameters are not able to determine correlation between semen quality and TP.(AU)

O objetivo do presente estudo foi determinar se há ou não correlação entre testes de termorresistência (TT) após descongelamento do sêmen e taxa de prenhez (TP) após inseminação artificial em tempo fixo (IATF). Quatro diferentes TT foram realizados nas 10 amostras utilizadas para a IA; um teste rápido (RTT) (30min/46°C) e três testes lentos (STT): STT1 (60min/38°C), STT2 (180min/38°C) e STT3 (300min/38°C). Duzentas e quinze vacas cruzadas multíparas foram submetidas à IATF sob o seguinte protocolo: no dia zero (d0), os animais receberam um dispositivo de P4+EB; em d7, PGF2α; em d8, retirou-se P4 e eCG+EC administrados; no d10, foi realizada IATF. Três diagnósticos gestacionais (DG) foram feitos, em d40, d70 e d120. As médias de motilidade espermática (%) em RTT e STTs foram 19,84±6,13, 28,55±10,48, 17,62±5,87 e 8,63±3,46, respectivamente, e TP nos três DG 61,86%, 57,67% e 55,81%, respectivamente. Por meio do teste de Person, uma correlação negativa significativa (P<0,05) foi encontrada entre os resultados de STT2 e PR aos 60 dias (r=-0,644) e entre STT3 e todas TPs (r=-0,774, -0,752 e -0,748). Concluiu-se que parâmetros de TT não são capazes de determinar correlação entre qualidade do sêmen e TP.(AU)

Resynchronization improves reproductive efficiency of suckled Bos taurus beef cows subjected to spring-summer or autumn-winter breeding season in South Brazil.

The objective of the present study was to evaluate the effect of estrus resynchronization (RE) after the first Timed Artificial Insemination (TAI) protocol on reproductive efficiency of suckled Bos taurus beef cows (n = 1052; Angus and Brangus) subjected to two different breeding season (BS) in Rio Grande do Sul, Brazil. In experiment 1, cows were maintained in native pasture on conventional BS (spring-summer), and in experiment 2, cows were maintained in a grazing area cultivated in an integrated crop-livestock system on modified BS (autumn -winter). Experiment 1 cows (n = 92) were randomly distributed in two reproductive managements: 1) TAI at the first day of the BS (Day 0), followed by natural service (NS) on day 10 until the end of the BS (TAI + NS; n = 45) or, 2) TAI on day 0, followed by RE 22 days after the first TAI and then followed by NS on day 42 until the end of the BS (TAI + RE22 + NS; n = 47). Experiment 2 cows (n = 960) were subjected to one of four reproductive managements: 1) only NS for 90 days of the BS (NS; n = 266); 2) TAI on day 0, followed by NS on day 10 until the end of the BS (TAI + NS; n = 200); 3) TAI on day 0, followed by RE 22 days after the first TAI and then followed by NS on day 42 until the end of the BS (TAI + RE22 + NS; n = 249) or, 4) TAI on day 0, followed by RE 30 days after the first TAI and then followed by NS on day 50 until the end of the BS (TAI + RE30 + NS; n = 245). In experiment 1, conception rate after first TAI was similar for treatments TAI + NS (42%, 19/45) and TAI + RE22 + NS (48%, 23/47; P = 0.4107). Total pregnancy rates at day 60 of the BS were 55.6% and 66.6% for TAI + NS and TAI + RE22 + NS, respectively (P = 0.006). In experiment 2, only 3% of the females submitted to NS were pregnant 30 days after the onset of BS, a lower rate compared to other groups (TAI + NS = 40%; TAI + RE22 + NS = 39.8%; TAI + RE30 + NS = 40%; P < 0.001). At 70 days of the BS, the groups TAI + RE22 + NS and TAI + RE30 + NS obtained greater pregnancy rate (66.3% and 69.4%, respectively) than other groups (NS = 16.9%; TAI + NS = 48%; P < 0.001). Pregnancy rate at the end of BS was greater in RE groups (TAI + RE22 + NS = 81.5%; TAI + RE30 + NS = 83.7%) than the NS (45.1%) or TAI + NS (71%). In conclusion, resynchronization increases pregnancy rate per AI (P/AI) and reproductive efficiency of suckled Bos taurus beef cows during spring-summer or autumn-winter breeding season in natural pasture or cultivated pasture, respectively.

Infrared thermography relationship between the temperature of the vulvar skin, ovarian activity, and pregnancy rates in Braford cows.

The objective of this study was to compare the presence of ovarian activity and pregnancy rates to temperature variation at the vulvar skin measured by infrared thermography (IRT). In addition, we also aimed to evaluate the IRT as a non-invasive method to evaluate animal breeding from fixed timed artificial insemination (FTAI). The study comprises 150 non-lactating beef Braford cows (5/8 Hereford × 3/8 Nellore) aged between 3 and 10 years. Data were collected along the FTAI protocol period during animal management. Animals were subjected to reproductive ultrasound evaluation and thermal images were performed by an infrared camera. Mean skin vulvar temperature (°C) and ovarian structures data were compared using Tukey's t test used as follow-up test to ANOVA. We observed a statistical difference in the mean vulvar skin temperature between animals that had the presence of ovarian follicles (34.2 ± 1.8) compared to no activity (35.4 ± 1.0; P < 0.05). However, vulvar skin temperature were similar between pregnant (34.5 ± 1.5) compared to non-pregnant (34.3 ± 1.9) animals (P > 0.05). In conclusion, the IRT technique was efficient to detect changes on vulvar skin temperature observed during FTAI protocol in Braford cows. Therefore, the use of IRT as an indirectly diagnostic tool to detect ovarian activity seems promising and further studies are required to validate their potential in beef cattle production.

Short-term dietary concentrate supplementation during estrus synchronization treatment in beef cows increased IGF-I serum concentration but did not affect the reproductive response.

The objective of this study was to evaluate if short-term dietary concentrate supplementation increased IGF-I serum concentration and resulted in a reproductive response during estrus synchronization treatment in non-lactating beef cows. Thirty non-lactating beef cows (Bos indicus × Bos taurus) were allocated to the same pastureland and fed native tropical grasses as a basal diet. Cows were synchronized using a 7-day CO-Synch plus controlled internal drug release (CIDR) protocol and received fixed time artificial insemination (FTAI). Cows were divided into two groups; the control group (n = 16) received 0.5 kg of concentrate/cow/day, whereas the supplemented group (n = 14) received 4.0 kg of concentrate/cow/day. The period of supplementation was 10 days from the day of CIDR insert to FTAI. The concentration of IGF-I increased (P < 0.05) in the supplemented group, while no significant changes were observed in the control group. Moreover, at the time of insemination, IGF-I serum concentrations were higher in supplemented cows compared with control cows (P < 0.05). Notably, metabolite and insulin concentrations did not differ (P > 0.05) between treatment groups or sampling day. The response to estrus induction, measured as estrus presentation, ovulation rate, and pregnancy rate, was similar between experimental groups (P > 0.05). In conclusion, our results indicated that supplementation with dietary concentrate for 10 days in non-lactating beef cows changed the endocrine milieu, specifically increasing IGF-I serum concentration. However, these endocrine changes did not affect response to estrous induction treatment.

Evaluation of grazing beef cows receiving supplements with different protein contents / Avaliação de vacas de corte em pastejo recebendo suplementos com diferentes teores de proteína

The aim of this study was to evaluate the effects of supplementation with different crude protein contents on the productive performance of grazing beef cows during post-calving. Thirty-six beef cows, with age and average body weight of 5 years and 490±17.9 kg, respectively, were used. The experimental design was completely randomized. The treatments were: control = cows received only mineral mixture ad libitum; supplemented = cows received 1 kg d-1 of supplement containing 80, 200, or 320 g crude protein (CP) kg-1. There was no effect (P ? 0.16) of supplementation on voluntary intake. A linear effect (P 0.02) of the CP content in the supplements was observed among supplemented cows, only for the CP intake. Supplementation did not affect (P ? 0.20) the total digestibility of organic matter, neutral detergent fiber corrected for ash and protein, and CP. Among supplemented cows, a positive linear effect (P 0.01) of the CP content in the supplement was observed for the CP digestibility. Intestinal flow of microbial nitrogen compounds and efficiency of synthesis microbial were not affected (P ? 0.18) by treatments. Performance, milk yield and composition were not also affected (P ? 0.11) by treatments. Supplementation did not affect (P ? 0.52) non-esterified fatty acids, urea nitrogen and progesterone serum concentrations. It is concluded that supplementation of grazing beef cows during post-calving does not affect nutritional and productive performance.

Objetivou-se avaliar os efeitos da suplementação com diferentes teores de proteína sobre o desempenho produtivo de vacas de corte em pastejo durante o pós-parto. Foram utilizadas 36 vacas de corte com idade e peso corporal médio de 5 anos e 490±17,9 kg, respectivamente. O delineamento experimental foi inteiramente casualizado. Os tratamentos foram: controle = vacas receberam somente mistura mineral ad libitum; suplementados = vacas receberam 1 kg dia-1 de suplemento contendo 80, 200 ou 320 g de proteína bruta (PB) kg-1. Não houve efeito (P ? 0,16) da suplementação sobre consumo voluntario. Entre os animais suplementados, o consumo de proteína aumentou linearmente (P 0,02) com o teor de PB no suplemento. A suplementação não afetou (P ? 0,20) a digestibilidade total da matéria orgânica, fibra em detergente neutro corrigida para cinza e proteína (FDNcp) e da proteína. Entre os animais suplementados, houve efeito linear positivo (P 0,01) dos teores de PB nos suplementos sobre a digestibilidade da PB. O fluxo intestinal de compostos nitrogenados microbianos e a eficiência de síntese de proteína microbiana não foram afetados (P ? 0,18) pelos tratamentos. O desempenho, produção e a composição do leite não foram afetados (P ? 0,11) pelos tratamentos. A suplementação não afetou (P ? 0,52) as concentrações séricas de ácidos graxos esterificados, ureia e progesterona. Conclui-se que a suplementação de vacas de corte em pastejo durante pós-parto não afeta o consumo e o desempenho produtivo.