Nelore Cows Research Articles

215 Supplementation with beta-carotene and vitamins improves pregnancy rate after timed-AI in beef Nellore cows grazed in pasture systems

Abstract The aim was to evaluate the effects of beta-carotene and vitamins (A, D3, E and biotin) on reproductive performance of grazing Nellore cows calving in different moments. A total of 497 multiparous cows (5.68 ± 0.11 parities) were homogeneously divided in 4 paddocks (Brachiaria brizantha spp.) according to BCS (2.8 ± 0.27), following a completely randomized design in a 2 x 2 factorial arrangement, being the factors: calving moment [CM = early October (EO; 1st-15th) or late October (LO; 16th-31st)]; and supplementation (SUP): control [(mineral supplementation, Fosbovi® Reprodução; n = 251) or vitamins (control + beta-carotene (150 mg), vitamins A (40.000IU), D3 (5.000IU), E (300 mg) and biotin (20 mg)/cow/day; n = 246)]. Mineral supplement and vitamins were daily offered for 60 days (30d before to 30d after 1st FTAI), and provided by DSM Produtos Nutricionais Brasil S.A. Cows were synchronized (1st FTAI) with a P4/E2-based FTAI protocol, and open cows were resynchronized (2nd FTAI) 30 days after the first insemination. The 1st FTAI conception rate (CR) tended to be greater for vitamins group, compared to control [64.2%(158/246) vs. 56.6%(142/251); P = 0.08], regardless of CM. The CM*SUP interaction was significant for CR at 2nd FTAI, with vitamins presenting higher CR over control in LO moment [52.1% (38/73) vs. 41.4% (24/58), P = 0.0053]. Greater cumulative CR (1st + 2nd FTAI) was observed for vitamins over control [83% (204/246) vs. 79% (198/251); P = 0,058], and for LO compared to EO [86% (157/183) vs. 78% (245/314); P = 0.01], without CM*SUP significance. The BCS was higher for the vitamins group, compared to control, at AI moment (3.00 vs. 2.81, P < 0.0001) and 30 days after AI (3.11 vs. 3.03, P < 0.0001), regardless of CM. The inclusion of beta-carotene and vitamins A, D3, E and biotin in mineral supplements is a tool to optimize reproductive performance and BCS of grazing Nellore beef cows during breeding season.

PSXII-35 The Periovulatory Endocrine Milieu Affects the Composition of the Oviductal Fluid in Beef Cows

Abstract Our main objective was to compare the composition of the oviductal fluid (OFL) between cows of high and low receptivity to the embryo. A model for receptivity based on the manipulation of the size of the preovulatory follicle (POF) was used to compare the composition of the OFL. Using this model, it has been proved that the oviduct of high receptivity cows has differences in morphology, gene expression, and extracellular matrix remodeling when compared to low receptivity cows. Cycling, non-lactating, multiparous Nelore cows (n = 14) were presynchronized before receiving cloprostenol (large follicle [LF] group) or not (small follicle [SF] group), along with a progesterone (P4) device on Day (D) ─10. Devices were withdrawn, and cloprostenol administered 42–60 h (LF) or 30–36 h (SF) before GnRH agonist treatment (D0). As a result, higher estrogen concentrations, corpora lutea, and progesterone concentrations were also observed in the LF group in comparison to the SF group. Four days after GnRH-induced ovulation, OFL was collected. Quantitative mass spectrometry was used to determine the concentration of 21 amino acids, 21 biogenic amines, 40 acylcarnitines, 76 phosphatidylcholines, 14 lysophosphatidylcholines, 15 sphingomyelins, 29 hexoses, and 17 prostaglandins and related compounds in the OF. MetaboAnalyst 3.0 was used to identify which metabolites better explained the separation of experimental groups and which could potentially be used as markers of receptivity. After multivariate and PLS analysis, samples of the LF and SF were divided clearly into two non-overlapping clusters. The most influential variables to separate the two groups included: Glutamate, Leucine, four phosphatidylcholines, three lysophosphatidylcholines, and arachidonic acid. Univariate analyses further confirmed these results. There were statistical differences in the concentration of 31 metabolites (P ≤ 0.05) between groups. We concluded that the composition of the OFL is different between cows with contrasting receptivity and fertility status.

Body size in beef cows and its influence on calf production

Cattle farming becomes more intensive when the productive efficiency of the cows is increased, and nutrition is adjusted to the animal biotype. Eighty purebred Charolais and Nellore cows and their crosses between 3 and 7 years of age, were grouped for body weight at calving into Light (332.6 kg), Moderate (385.3 kg) and Heavy (444.6 kg). Cows and their calves were weighed at calving, at 63 days (early weaning) and at 210 days. The estimated milk production of the cows was evaluated by manual milking at 21, 42 and 63 days postpartum. The difference in the weight of the cows at calving was maintained during lactation and at 210 days postpartum. The body size of the cow did not influence milk production. Heavier cows produce heavier calves up to 365 days of age compared to lighter cows. The reproductive performance of the cows is not affected by their weight. The production of kilograms of calf for every 100 kilograms of cow at calving and weaning is higher in Light cows. The production of kilograms of calf adjusted for the pregnancy rate of the cows is higher in Heavy cows. Production efficiency in kilograms of calf per area is lower in Heavy cows.

Effects of protein supplementation on Nellore cows’ reproductive performance, growth, myogenesis, lipogenesis and intestine development of the progeny

Context It is hypothesised that protein supplementation in pregnant Nellore cows during the dry season would improve reproductive performance in the next breeding season, as well as growth, myogenesis and intramuscular lipogenesis of the progeny until weaning. Aims To evaluate the effect of maternal nutrition on cow reproductive performance, as well as on the growth, myogenesis and lipogenesis of the progeny until weaning. Methods A total of 92 pregnant cows were fed on pasture, and half of the cows were also fed a mineral–protein supplement (36% crude protein) from 124 ± 21 days of pregnancy to calving. Therefore, two treatments were tested: non-supplemented or supplemented cows. Progeny were weighed after birth, 130 days after birth and at weaning. Six newborn calves from each treatment were slaughtered to collect muscle and jejunum samples to analyse histology and gene expression. In addition, Longissimus thoracis muscle biopsies were collected at 11 days after birth and weaning for gene expression analyses. Key results Supplemented cows had greater bodyweight (P = 0.03) and body condition score (P = 0.05) during gestation, and the pregnancy rate in the subsequent breeding season had a tendency (P = 0.10) to be greater. The progeny from supplemented cows had greater bodyweight at birth (P = 0.05). However, no differences (P > 0.05) were found in bodyweight at weaning or in the average daily gain during this period. Non-supplemented calves had greater SLC27A4 (P = 0.04) expression and a tendency for greater expression of SLC5A1 (P = 0.08) in the jejunum. Muscle gene expression data showed that progeny from supplemented cows had greater expression of myogenic (WNT10B), adipogenic (PPARG, ZFP423, CD36) and fibrogenic (TGFβ1) markers at birth and at weaning (P ≤ 0.10). Conclusions In conclusion, protein supplementation of pregnant Nellore cows leads to positive effects for subsequent reproductive performance and for muscle development of their progeny. In addition, the progeny from feed-restricted cows increases prenatal intestinal development for better nutrients absorption under a potentially impaired environmental condition. Implications The use of protein supplementation in pregnant Nellore cows has a positive impact on the production system, increasing productivity in a cow/calf operation.

Effects of pre- and postpartum supplementation on lactational and reproductive performance of grazing Nellore beef cows

Context Few studies have evaluated the effects of providing concentrate pre- or postpartum, or during both of these intervals, to beef cows grazing tropical pastures, even though this information is important for planning breeder herd management. Aims A study was undertaken to examine the effects of supplementation with concentrates before calving (prepartum), after calving (postpartum) or during both these intervals on production and reproductive efficiency in Bos indicus beef cows grazing Urochloa decumbens pasture. Methods Nellore cows, initially 6 months pregnant (mean ± s.e.), weighing 516 ± 1.3 kg and body condition score 4.7 ± 0.15 (1–9 scale), were used in an experiment with four treatments in a 2 × 2 factorial design with 20 animals per treatment. The treatments comprised no supplementation or provision of a supplement (1 kg/cow.day containing 28% crude protein) for 90 days prepartum only, 90 days postpartum only or during the pre- and postpartum intervals. Key results Responses could be described in terms of the main effects of providing the supplement pre- or post-calving; the interactions were not significant (P > 0.05). Prepartum supplements increased the cow bodyweight at calving by 29 kg, and calf birthweight by 3.7 kg (P 4 did not change the response to postpartum supplementation. Implications Prepartum supplementation may increase cow performance and calf weight at birth, whereas postpartum supplementation may improve the reproductive efficiency.

Reproductive efficiency Nellore and crossbred cows submitted to administration of melengestrol acetate (MGA) after FTAI protocols

This study aimed to evaluate the influence of medroxyprogesterone acetate (MGA) supplementation between the 13th and 20th day after Fixed-Time-Artificial Insemination (FTAI), on the conception and gestation rates of Nellore and crossbred cows (Nellore x Angus), pluriparous and lactating. For the study, 349 Nellore cows and 270 crossbred cows were selected, distributed into 1) group G1 (n=176): Nellore cows submitted to the FTAI protocol, without MGA supplementation; 2) group G2 (n=173): Nellore cows submitted to the FTAI protocol, with supplementation for 7 days of MGA® (0.28g/AU/day) from the 13th post-FTAI; 3) group G3 (n=119): crossbred cows: FTAI protocol, without MGA supplementation; 4) group G4 (n=151): crossbred cows: FTAI protocol followed by MGA supplementation for 7 days (0.28g/AU/day), from the 13th to the 20th day after FTAI. For statistical analysis, the procedures MIXED and GLIMMIX from SAS were used. G3 had higher rates of conception (CR=85.7%) and pregnancy (PR=95.8%) at the end of the breeding season (P<0.05), without the interference of supplementation with MGA (P>0.05). G1 females had a lower conception rate (TC=76.7%) (P<0.05), with the use of MGA® (CR-MGA=59.5%), but similar rates of pregnancy (PR=90.3%; PR-MGA=92.5%) to the G2, at the end of the breeding season (P>0.05). When G2 and G4 were compared, we found that crossbred females supplemented had higher rates of conception and pregnancy. In conclusion, crossbred animals have higher conception and pregnancy rates at the end of the breeding season. Besides, we found that Nellore females had a lower conception rate, with the use of MGA® Premix.

In vitro embryo production in Nelore cows supplemented with calcium salts of long-chain fatty acid

This study was performed to evaluate the effects of supplementation of lactating Nelore cows with calcium salts of long-chain fatty acids (Ca-LCFA) of soybean oil on in vitro oocytes competency, cleavage rate, embryo production rate, pregnancy rate, and sex ratio of transferred embryos. Fifteen multiparous Nelore cows grazed on a Tifton 85 pasture were allotted to two treatments: (1) supplement without fat inclusion (CONT, n = 6) and (2) supplement containing 47.2 g Ca-LCFA /kg (to provide an intake of 0.2 kg Ca-LCFA/day) based on dry matter (n = 9). Animals were subjected to 2.53 ± 1.35 rounds of consecutive ovum pick up at intervals of 27.65 ± 21.72 days. Oocytes were morphologically evaluated, selected, maturated, fertilized, and cultivated for embryo production in vitro and then transferred into recipients who had previously undergone an embryo transfer protocol at a fixed time. The number of aspirated oocytes, the proportion of viable oocytes, cleavage rate, embryo percentage, pregnancy rate, and sex ratio were not affected when Nelore cows were supplemented with Ca-LCFA of soybean oil compared with non-supplemented Nelore cows. In conclusion, our results suggest that feeding a supplement containing 47.2 g Ca-LCFA/kg (to provide an intake of 0.2 kg Ca-LCFA/day) to Nelore cows does not affect in vitro embryo production in lactating Nelore cows. However, further studies using higher dietary doses of fat could be useful to determine the potential of fat supplementation to improve in vitro embryo production.

Influence of nutritional and ovarian parameters on pregnancy rates of Nelore cows artificially inseminated at fixed time

This experiment aimed to evaluate the effect of weight gain, body condition score and antral follicle count on the fertility of cows subjected to fixed-time artificial insemination. To this study, it was used 194 Nelore, pluriparous cows, between the 30th and the 45th day of the postpartum period. The cows were weighed, was classified by the body condition score and a transrectal ultrasound was performed in the ovaries to identify the corpus luteum and for counting the antral follicles. Then, the females were submitted to a hormonal protocol to perform the artificial insemination in fixed time. Thirty days after the artificial insemination, the cows were weighed again and the pregnancy was diagnosed by transrectal ultrasound. The pregnancy rate did not interact (P>0.05) with the body score condition, nor the presence of the corpus luteum, neither with the antral follicles count. The weight gain between the artificial insemination moment and the pregnancy diagnosis showed an interaction (P = 0.02) with the pregnancy rate. The weight gain average between the FTAI and the pregnancy diagnosis was 9.0 kg. The animals that gained up to 73 kg, showed higher pregnancy rate. In conclusion, the weight gain between the artificial insemination in fixed time and the pregnancy diagnosis influenced the pregnancy rate.

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.

Number of Calving and Its Relationship with Productive Indicators in Nelore Cows

Number of Calving and Its Relationship with Productive Indicators in Nelore Cows

Influence of the male effect on follicular dynamics and pregnancy rate in lactating cows undergoing fixed-time artificial insemination

The objective of this study was to determine the biostimulatory effect of bull exposure on follicular dynamic traits and pregnancy rate of lactating Nelore cows subjected to a fixed-time artificial insemination protocol. A total of 150 postpartum cows were randomly assigned to either a non-biostimulated or (C) and biostimulated (BS) group. Ovarian follicular dynamics was monitored by using transrectal ultrasonography. Females in both groups showed follicular regression after beginning the hormonal protocol. Daily follicular growth and percentage of ovulating females did not differ (P > 0.05) between groups. The interval between the start of the follicular wave and the ovulation was smaller (P < 0.05) in the C group; however, the pregnancy rate was greater (P < 0.05) in the B group. Furthermore, the BS group required less services per pregnancy (P < 0.05). In summary, the results allow to conclude that the association between the male effect and the Fixed Timed Artificial Insemination (FTAI), does increase the pregnancy rates and reduce the number of services per female, although there is no effect on follicular dynamics.

Can cover sheath model influence semen retention in AI-gun trials and pregnancy rates of cows inseminated at a fixed-time?

The achievement of satisfactory results in fixed-time artificial insemination (FTAI) protocols depends on several factors, such as the quality of the materials used to perform the artificial insemination (AI). In this context, three experiments were conducted to evaluate the effect of the cover sheath model on the residual retention of semen during AI and the pregnancy rates of cows submitted to FTAI. In Experiment 1, 400 straws of cryopreserved bovine semen were thawed and repacked in samples with similar weight and volume characteristics. Each new dose of semen (n = 300) was mounted using one of three AI cover sheath models (n = 100 semen/sheath doses): the main brand in the global market (G1), the main model in the Brazilian market (G2), and a model marketed as having a low residual semen retention rate (G3), to determine the percentages of seminal elimination (PSEs) during AI. In Experiment 2, 464 Nelore cows were synchronized through intravaginal progesterone implants and inseminated using the same cover sheaths as those tested in Experiment 1, which were grouped into classes (conventional: G1 and G2 [n = 225]; and low reflux: G3 [n = 239]). In Experiment 3, 859 Nelore cows were synchronized and inseminated as described above, using the same cover sheaths previously tested. After each AI, cover sheaths were visually inspected for the presence of residual semen and pregnancy diagnosis was performed 35 days after FTAI (Experiments 2 and 3). The PSEs in Experiment 1 were 91.7%, 90.6% and 96.5% for groups G1, G2 and G3, respectively (P = 0.05). The pregnancy rates in Experiment 2 were 53.33% and 58.16% for the conventional and low reflux model, respectively (P > 0.05), but there were differences (P = 0.05) among the cover sheath models employed for AI (G1 - 57.72% [71/123]; G2 - 48.04% [49/102]; G3 - 58.16% [139/239]). Additionally, a lower semen reflux incidence (P < 0.05) was observed in the low residual sperm retention model (0.72%) in Experiment 3, compared to the main international (10.42%) and national (22.99%) market models. In conclusion, residual semen retention occurs regardless of the cover sheath model used for AI. However, the PSE is influenced by the model and quality of cover sheath used. According to the results, the cover sheath represents a factor that may compromise the pregnancy rates of synchronized cows for FTAI.

The effect of clitoral stimulation post artificial insemination on pregnancy rates of multiparous Bos indicus beef cows submitted to estradiol/progesterone-based estrus synchronization protocol.

Clitoral stimulation after artificial insemination (AI) in beef cattle is a common practice utilized by AI technicians; however, the effect of clitoral stimulation during fixed-time AI (TAI) is still unknown. The objective of the present experiment was to evaluate the effect of clitoral stimulation on temperament responses and pregnancy rates to TAI in Bos indicus beef cows. A total of 1,186 multiparous Nellore cows across three different locations were assigned to an estradiol/progesterone-based estrus synchronization + TAI protocol (day -11 to 0). Cows were randomly assigned to receive either 3 s of clitoral stimulation (n = 602) or no clitoral stimulation (n = 584) immediately after TAI (day 0). Cow body condition score (BCS) was recorded on day -11. Estrus expression was evaluated based on estrus detection visual aid patch activation on day 0 (estrus, ≥50% activated; no estrus, <50% activated). Temperament was assessed by individual chute score based on a 5-point scale before TAI, and individual exit velocity was measured after clitoral stimulation. Pregnancy diagnosis was performed 30 d after TAI via transrectal ultrasonography. Pregnancy rate to TAI was positively affected by BCS (P < 0.01) and estrus expression (P = 0.03). Pregnancy rates of cows receiving clitoral stimulation did not differ (P = 0.39) from cows non-stimulated (47.5 ± 4.6% vs. 44.3 ± 4.6%, respectively). No interaction of clitoral stimulation and estrus expression was observed (P = 0.26). Chute score was positively correlated to exit velocity (P < 0.01; r = 0.29); however, clitoral stimulation did not affect exit velocity (P = 0.86). In summary, pregnancy rates to TAI are influenced by various factors and multiple strategies have the potential to increase the fertility of beef cows submitted to TAI; however, clitoral stimulation of Bos indicus beef cows did not improve TAI pregnancy rate.

Feed efficiency and maternal productivity of Bos indicus beefcows.

This study evaluated 53 primiparous cows (36.8±1.23 months old and 484±40.9 kg of body weight) performance tested (GrowSafe® System) from 22±5 to 190±13 days of lactation in order to obtain daily dry matter intake (DMI). The animals received a high-forage diet (forage-to-concentrate ratio of 90:10). Milk production of the cows was evaluated three times by mechanical milking and the energy-corrected milk yield (ECMY) was calculated. Energy status (through the indicators glucose, cholesterol, triglycerides, and β-hydroxybutyrate), protein status (indicators albumin, urea, and creatinine), mineral status (indicators calcium, phosphorus, and magnesium), and hormonal status (indicators insulin and cortisol) were estimated four times throughout lactation. The residual feed intake (RFI) of cows was calculated considering DMI, average daily gain (ADG) and mid-test metabolic weight (BW0.75) obtained in early lactation (from 22±5 to 102±7 days), and the animals were classified as negative (most efficient) or positive RFI (least efficient). The RFI model explained 53% of the variation in DMI. The mean DMI, ADG, ECMY, and calf weight as a percentage of cow weight were 12.47±2.70 kg DM/day, 0.632±0.323 kg/day, 10.47±3.23 kg/day, and 36.6±5.39%, respectively. Negative RFI cows consumed 11.5% less DM than positive RFI cows, with performance and metabolic profile being similar to those of positive RFI cows, except for a lower milk protein content and higher blood cholesterol concentration. In conclusion, negative (most efficient) and positive RFI (least efficient) Nellore cows, fed an ad libitum high-forage diet, produced similar amounts of milk, fat and lactose and had similar subcutaneous fat thickness, weight, calf weight as a percentage of cow weight, and blood metabolite concentrations (except for cholesterol). Therefore, there are economic benefits to utilizing RFI in a cow herd since cattle had decreased DMI with similar overall performance, making them more profitable due to lower input costs.

Importance of temperament in the pregnancy by timed insemination in bovine females Bos taurus indicus

The aim of this research was to evaluate the effects of the temperament of bovine females Bos taurus indicus submitted to a timed artificial insemination (TAI) protocol on the concentrations of cortisol, diameter of the largest follicle, pregnancy by TAI on Days 30 (P/TAI 30) and 60 (P/TAI 60) after TAI. Nellore cows (n = 2702) of 45 ± 7 days post-partum were submitted to the same TAI protocol. On D -10 devices containing 1 g of progesterone were inserted into the vagina and 2 mg of estradiol benzoate were applied intramuscularly. On D -2, the devices were removed and 530 µg of sodium D-cloprostenol, 300 IU of equine chorionic gonadotropin, and 1 mg of Estradiol Cypionate were applied. Forty-eight hours after the final injection, the cows were submitted to TAI (D 0). The temperament of the cows was rated on a numerical scale from 3 to 12 using the composite reactivity score (RS) on D -10. The RS included the evaluation of the movement and breathing while the animal was in the cattle chute and the exit velocity. Cows were classified as Calm (RS ≤ 4; n = 830; Calm group), Reactive (RS = 5 to 8; n = 1313; Reactive group) and Very Reactive (RS ≥ 9; n = 559; Very Reactive group) and 5% of the cows of each group were submitted to blood collection for the subsequent plasmatic cortisol concentration measurement by ELISA. It was observed that Calm group had lower concentration of cortisol than did the Reactive and Very Reactive groups (35.07 ± 1.78, 50.58 ± 2.76, and 54.45 ± 3.39 nmol/L, respectively). The Calm group had diameter of the largest follicle on the day of TAI compared to Reactive and Very Reactive groups (14.4 ± 0.2, 13.6 ± 0.4, and 13.2 ± 0.2 mm, respectively). The Calm and Reactive groups had higher P/TAI compared to the Very Reactive Group on Day 30 (56.4%, 57.0%, 51.0%, respectively) and on Day 60 (50.0%, 47.3%, 42.7%, respectively). In conclusion, temperament influences the reproductive efficiency of bovine females Bos taurus indicus submitted to TAI protocols.

Performance, metabolic and hormonal responses of grazing Nellore cows to an energy-protein supplementation during the pre-partum phase

BackgroundSupplementation programs for prepartum beef cows are usually adopted because the nutritional status of the cows upon calving is a main factor impacting reproductive performance of the next production cycle. This study evaluated the effects of 60-d pre-partum energy-protein supplementation on performance, metabolic and hormonal responses during the peripartum phase of grazing beef cows. Thirty-eight pregnant multiparous Nellore cows were assigned to a completely randomized design with two treatments: control (no supplement) and supplementation (1.5 kg of energy-protein per d with 30% crude protein, dry matter basis).ResultsThe supplemented cows had higher ADG pre-partum (P < 0.10), but postpartum ADG did not differ between treatments. Supplementation did not affect BCS and calf BW upon calving, on days 45 and 90, milk yield and composition (P > 0.10). No differences were found for forage intake and neutral detergent fiber digestibility (P > 0.10). The intake and digestibility of CP and OM increased in response to supplementation (P < 0.10). An interaction occurred between supplementation and peripartum days for BUN, βHB, T3 and T4, which had higher concentrations for supplemented cows at pre-partum period (P < 0.10). Concentration of others blood parameters significantly changed along peripartum days (P < 0.10). There was no difference in pregnancy rates and days from calving to conception between treatments (P > 0.10).ConclusionsProviding an energy and protein supplement to grazing Nellore cows over the last 60 d of gestation improved their pre-partum energy balance. However, no post-partum carryover effects were detected.

Relationship of Longevity with Productive and Reproductive Variables in Nelore Cows of the Bolivian Tropic

The objective of this study was to evaluate the relationship between longevity with productive and reproductive efficiency variables of Nelore cows in grazing systems in the Bolivian tropics. Retrospective data corresponding to the period 1992-2019, belonging to the Cooperativa Agropecuaria Integral San Juan de Yapacaní and the Foundation Technology Center on Agriculture and Livestock, Santa Cruz-Bolivia were used. The data corresponding to 774 Nelore breed cows, primiparous and multiparous discarded with a total of 4050 calvings were evaluated. The following variables were analyzed: Number of calves, live weight of cow in kg, calf weight at birth in kg, calf weight at weaning in kg, total calf weight in kg, age at first calving in months, longevity in days and calving interval in days. Cows born in the year (1985-1995) are those that arrive later to have their first calving, have a greater calving interval, have greater longevity, similar weaning weight, lower birth weight, lower live weight and higher weight total calf. While cows born in the year (2005-2015) are those that arrive younger to have their first calving, they have a shorter calving interval; have shorter longevity, similar weaning weight, higher birth weight, live weight intermediate and lower total calf weight. For the three periods analyzed, the length of life increases between 0.66-0.95 days on average when the age at first calving increases by one unit, between 1.78-2.99 days on average when the calving-calving interval increases by one unit and between 1.77-1.83 days on average when total calf weight increases by one unit. It is concluded that it was possible to find a model that explained that the greater longevity of Nelore cows in a grazing system in the Bolivian tropics was related to the older age at first calving, the greater calving interval and the greater kg of weights total calves.

Protein, energetic, enzymatic and mineral profile of Nellore cows during the pregnancy, parturition and postpartum

The aim of this study was to evaluate the protein energetic, enzymatic and mineral profile of Nellore cows during the pregnancy, parturition and postpartum. Fifteen multiparous cows with 4 ± 1 years of age and live weight of 400 ± 50 kg were used at different stages (non-pregnant, in the initial, middle and late pregnancy, at birth, one day postpartum, 30 and 60 days postpartum). Blood collections were performed every 30 days and assayed for the following blood biomarkers: Protein (total proteins, albumin, urea and creatinine), energetic (cholesterol, triglycerides, glucose and beta hydroxybutyrate), mineral (calcium, phosphorus, magnesium) and enzymatic (alkaline phosphatase and aspartate aminotransferase). Calcium had the lowest concentrations (p &lt; 0.05) in the initial pregnancy, while phosphorus had the highest concentration at parturition (p &lt; 0.05). Triglycerides, glucose and beta hydroxybutyrate were influenced by the stages of pregnancy, reducing in the late pregnancy and at parturition. Glucose had a reduction in the late pregnancy and elevation in the postpartum. Beta hydroxybutyrate showed increase at the late pregnancy. Although lipomobilization occurred in the phases of higher metabolic demands in the attempt to maintain homeostatic conditions. Nellore cows did not present negative energy balance in the late pregnancy period, maintaining normal variation in blood markers throughout the experimental period.

Effect of tannins and monensin on feeding behaviour, feed intake, digestive parameters and microbial efficiency of nellore cows

This study aimed to evaluate the associative effect of monensin and tannins on intake, feeding behaviour, digestibility, rumen kinetics, microbial protein synthesis and nitrogen balance. In a 2 × 4 factorial arrangement, 8 rumen cannulated Nellore cows were distributed in 2 contemporary 4 × 4 Latin squares and received 8 diets that differed in the level of tannins (0.00, 0.75, 1.50 and 2.25% DM) and presence of monensin. Monensin was daily administered to each cow in one square (about 32 mg/kg DM). No interaction between monensin and tannins was observed (p > .05). Tannins linearly reduced feed intake, but linearly increased daily eating time (p < .05), although these did not alter the number of meals. Monensin increased CP digestibility by 6% (p = .0387) while tannins linearly reduced digestibility of DM, CP, OM and TDN, whereas the reduction was quadratic for ADF and NDF. Tannins linearly reduced the rumen disappearance rate by linearly reducing both passage and digestion rates. Tannins also linearly reduced urinary urea, though neither additive affected microbial protein synthesis. Monensin reduced the proportion of N excreted in faeces, whereas tannins linearly increased faecal N and linearly reduced both urinary and retained N. Monensin and tannins have shown independent effects on feeding behaviour, feed intake, digestive parameters, microbial protein synthesis and N balance, but they did not improve nutrient usage, although monensin alone has shown to have potential to promote N utilisation. Tannins may play an important role in reducing the excretion of N in urine. Highlights Tannins reduce the efficiency of nutrient usage in cattle. Tannins change the pathway of the excretion of the feeding nitrogen. The emission of N2O from the urine may be reduced by the use of tannins in cattle feeding.

Evaluation of body weight and hip height in Nellore cows in a tropical environment

The aim of this study was to evaluate random regression models to estimate genetic parameters for body weight and hip height in Nellore females and identify the best time to select these characteristics for adult size control. The dataset comprised 33,569 body weight and 31,804 height records from 3,860 and 3,487 females, respectively. Contemporary group and physiological state (for body weight analysis) were modeled as fixed effects, whereas age at birth (both linear and quadratic effects) and Legendre polynomials of age at (k = 4) as covariates. Random effects, including the additive genetic effects, and the animal permanent environment effect and the dam (for body weight analysis), were also included in the model. Random effects were modeled by Legendre polynomials of degree k in [3, 6], while residues were considered to be homogeneous or heterogeneous. The best model for body weight included heterogeneous residual variance with 21 classes and Legendre polynomials of degree k = 3, k = 6 and k = 1 for the additive genetic effects, animal and maternal permanent environment effects, respectively. The best model for hip height included homogeneous residual variance and Legendre polynomials of degree k = 4 and k = 3 for the additive genetic effects and animal permanent environment effect, respectively. Heritability estimates were moderate to high and suggest the studied characteristics could be used for maintaining cow size, being the selection at 3 years sufficient to get the desired size.