Comparison of ruminal microbiota, IL-1ß gene variation, and tick incidence between Holstein × Gyr and Holstein heifers in grazing system.

Introduction: The variation in bacterial communities among breeds has been previously reported and may be one of the reasons why Holstein × Gyr dairy heifers have better development in grazing systems in tropical conditions. This study aimed to explore the ruminal microbiota composition, the IL-1ß gene variation, tick incidence, and blood parameters of Holstein × Gyr (½ Holstein × ½ Gyr) and Holstein heifers grazing intensely managed Guinea grass (Panicum maximum Jacq. cv. Mombaça). Methods: Sixteen heifers were divided into two groups consisting of 8 Holstein × Gyr and 8 Holstein heifers. The experimental period was comprised of 3 periods of 21 days. Ruminal samples were taken via the stomach tube technique. The sequencing of the V4 hypervariable region of the 16S rRNA gene was performed using the Illumina MiSeq platform. Counting and collection of ticks were conducted each 21 days. Blood and skeletal muscle tissue biopsies were performed at the end of the experiment. Results: Firmicutes were the most abundant phyla present in both breed rumen samples and Bacteroidota showed differences in relative abundance between breed groups, with greater values for Holstein heifers (p < 0.05 with FDR correction). The 10 most abundant unique OTUs identified in each breed included several OTUs of the genus Prevotella. Holstein heifers had a greater tick count and weight (9.8 ticks/animal and 1.6 g/animal, respectively) than Holstein × Gyr (2.56 ticks/animal and 0.4 g/animal, respectively). We found nucleotide substitutions in the IL-1ß gene that might be related to adaptation and resistance phenotypes to tick infestation in Holstein × Gyr heifers. Blood concentrations of urea, albumin, insulin-like growth factor 1, triiodothyronine, and thyroxine were greater in Holstein × Gyr than in Holstein heifers. Conclusion: Adaptations in Holstein × Gyr heifers such as ruminal microbiota, tick resistance, nucleotide substitutions in IL-1ß gene, and hormone concentration suggest a better energy metabolism and thermoregulation resulting in better performance in tropical grazing systems.

A comprehensive molecular analysis of bovine coronavirus strains isolated from Brazil and comparison of a wild-type and cell culture-adapted strain associated with respiratory disease.

Bovine coronavirus (BCoV) has dual tropisms that can trigger enteric and respiratory diseases in cattle. Despite its global distribution, BCoV field strains from Brazil remain underexplored in studies investigating the virus's worldwide circulation. Another research gap involves the comparative analysis of S protein sequences in BCoV isolates from passages in cell lines versus direct sequencing from clinical samples. Therefore, one of the objectives of our study was to conduct a comprehensive phylogenetic analysis of BCoV strains identified from Brazil, including a respiratory strain obtained during this study, comparing them with global and ancestral BCoV strains. Additionally, we performed a comparative analysis between wild-type BCoV directly sequenced from the clinical sample (nasal secretion) and the cell culture-adapted strain, utilizing the Sanger method. The field strain and multiple cell passage in cell culture (HRT-18) adapted BCoV strain (BOV19 NS) detected in this study were characterized through molecular and phylogenetic analyses based on partial fragments of 1,448 nt covering the hypervariable region of the S gene. The analyses have demonstrated that different BCoV strains circulating in Brazil, and possibly Brazilian variants, constitute a new genotype (putative G15 genotype). Compared with the ancestral prototype (Mebus strain) of BCoV, 33 nt substitutions were identified of which 15 resulted in non-synonymous mutations (nine transitions and six transversions). Now, compared with the wild-type strain was identified only one nt substitution in nt 2,428 from the seventh passage onwards, which resulted in transversion, neutral-neutral charge, and one substitution of asparagine for tyrosine at aa residue 810 (N810Y).

Frequent social regroupings affect corporal and reproductive development, metabolic status, and behavioral time budget in dairy heifers.

We aimed to evaluate the corporal and reproductive development, metabolic status, and behavioral patterns of resident dairy heifers subjected to social regroupings (SR). Holstein replacement heifers (153.3 ± 16.1 kg, 11 months old) were homogeneously allocated to: 1) Control (CON; n = 14 resident + 5 "permanent") and 2) Regrouped (RG; n = 14 resident + 5 "changing"). "Changing" heifers were exchanged for 5 novel heifers every 21 d over 205 days (total = 10 SR). At each SR, body weight, wither height, body condition score (BCS), eating, ruminating, lying and standing behaviors were recorded, and blood hormones and metabolites were determined. Behavior was registered through scan sampling every 10 min., and estrus was detected using patches. Wither height and BCS were greater in CON than RG at SR9 and 10, and at SR4 and 5, respectively (P < 0.01). Control heifers showed first heat earlier (93 ± 9 d vs 126 ± 14 d; P = 0.03) and presented greater insulin growth factor- 1 (171.3 vs 120.0 ng/ml ± 10.1; P < 0.01) and glucose (4.3 vs 4.2 mmol/L ± 0.07; P = 0.04) concentrations than RG, while non-esterified fatty acids concentration was greater in RG (0.35 vs 0.30 mmol/L ± 0.04 P = 0.04). Regrouped heifers were observed more times eating (0.45 vs 0.33 ± 0.01), but fewer times ruminating (0.21 vs 0.24 ± 0.01) than CON (P < 0.01). Frequent SRs negatively affected corporal and reproductive development and energy metabolism, and altered behavioral patterns in dairy heifers.

Maternal instinct of imported meat direction cattle and ethology of their calves

The examination of maternal qualities in the ethology of cows and their young offspring, derived from the study on adaptability and productivity of second and third-generation Aberdeen Angus cattle imported to Kazakhstan from Canadian and European selection, is presented in this paper. The findings indicate that Canadian heifers, belonging to the second generation, displayed extended feeding behavior throughout the day, dedicating 33.2 minutes or 2.2% more time to feeding compared to their European counterparts (P < 0.001). Similar disparities between groups were observed in the duration of the ruminant process. Moreover, Canadian heifers consumed water for an additional 2 minutes or 0.6%, which can be attributed to their higher daily feed intake. The calving process of Aberdeen Angus cows generally proceeded smoothly, demonstrating a well-developed maternal instinct towards their offspring. Notably, calves born from Canadian cows exhibited greater agility and achieved the ability to stand on their feet in a shorter time, with an average duration of 41.0 ± 1.60 minutes, which was 11.7% faster than European calves. Additionally, Canadian calves displayed a shorter time to locate their mother's breast, with an average duration of 68.0 ± 7.70 minutes.(AU)

Effects of heat-stress on oocyte number and quality and in vitro embryo production in Holstein heifers

Background: This study aimed to determine the effects of environmental temperature on the number and quality of oocytes and embryo production rates obtained by performing ovum pick up (OPU). Heat stress leads to long-term, short-term, visible, and invisible effects in dairy cows. Its effects on reproduction are evident in all stages, from oocyte development to birth. Disturbance in ovarian follicle development, follicular dominance deficiency, anoestrus, polyspermia, embryonic losses, decreased fetal growth, and abortion are some examples of responses to these effects. The aim of the present study was aimed to determine the effects of ambient temperature on oocyte quality and number and embryo production rates. Materials, Methods & Results: The animal material used in this study comprised 10 Holstein heifers. At the beginning of the study, the heifers were 13-15 months old. OPU was performed at different times of the year, and weather conditions were recorded. Grouping according to ambient temperature was done as < 10°C (group 1), 10-25°C (group 2), and > 25°C (group 3). The veterinary ultrasonography device and a set of compatible intravaginal OPU probe, catheter, and aspiration device were used for OPU application. All antral follicles with diameters of 2-8 mm in the ovaries were aspirated. The aspirated follicle fluids were examined under a stereo microscope, and the cumulus-oocyte complexes (COC) were collected and classified according to their structure. A, B, and C-quality oocytes were included in the in vitro embryo production process. After performing 69 OPUs on random days of the cycle, the number of oocytes per OPU was found to be 8.72, 6.32, and 6.85 in groups 1, 2, and 3, respectively (P < 0.05). The number of viable oocytes per OPU was 6.83, 4.64, and 4.65 in groups 1, 2, and 3, respectively (P < 0.05). The statistical difference between the first group and the other groups was significant for cleavage and blastocyst counts (P < 0.05). Discussion: All the negative effects of heat stress on animals resulted from the increased body temperature. Reproductive performance is adversely affected by high temperatures and humidity during periods of high ambient temperatures. Metabolic heat is released, and the heat load increases due to the metabolism of nutrients in cattle. Internal body temperature is regulated via the dissipation of metabolic heat to the environment. The amount of heat dissipated via conduction and convection depends on the unit body weight, surface area, skin and coat color, difference in temperature gradient of the animal and ambient temperature, and humidity. In the present study, it was determined that the blastocyst development rates of the oocytes obtained in the warm season (>25°C [group 3]) were lower than those of the other groups. It was concluded that this may be because the oocytes developed under chronic heat stress in the animals, and several cycles were required to enhance oocyte quality and developmental potential. Additional studies are needed to investigate the response of oocytes obtained with OPU to heat stress during embryonic developmental stages and to determine the sensitivity and effects of embryonic tissue damage according to developmental stages. Based on the results of the present study, it was concluded that performing OPU and in vitro embryo production (IVEP) when the ambient temperature is close to the thermoneutral limits may increase the blastocyst development rates.

Effects of Maternal Nutrition on Female Offspring Weight Gain and Sexual Development.

Maternal nutrition during pregnancy influences postnatal life of animals; nevertheless, few studies have investigated its effects on the productive performance and reproductive development of heifers. This study evaluated the performance, reproductive development, and correlation between reproduction × fat thickness and performance × ribeye area (REA) traits of heifers. We also performed an exploratory genomic association during the rearing period in heifers submitted to fetal programming. The study comprised 55 Nellore heifers born to dams exposed to one of the following nutritional planes: control, without protein-energy supplementation; PELT, protein-energy last trimester, protein-energy supplementation offered in the final third of pregnancy; and PEWG, protein-energy whole gestation, protein-energy supplementation upon pregnancy confirmation. Protein-energy supplementation occurred at the level of 0.3% live weight. After weaning, heifers were submitted to periodic evaluations of weight and body composition by ultrasonography. From 12 to 18 months, we evaluated the reproductive tract of heifers to monitor its development for sexual precocity and ovarian follicle population. The treatments had no effect (p > 0.05) on average daily gain; however, the weight of the animals showed a significant difference over time (p = 0.017). No differences were found between treatments for REA, backfat, and rump fat thickness, nor for puberty age, antral follicular count, and other traits related to reproductive tract development (p > 0.05). The correlation analysis between performance traits and REA showed high correlations (r > 0.37) between REA at weaning and year versus weight from weaning until yearling; however, no correlation was found for reproductive development traits versus fat thickness (p > 0.05). The exploratory genomic association study showed one single-nucleotide polymorphism (SNP) for each treatment on an intergenic region for control and PEWG, and the one for PELT on an intronic region of RAPGEF1 gene. Maternal nutrition affected only the weight of the animals throughout the rearing period.

Intramuscular collagen characteristics and expression of related genes in skeletal muscle of cull cows receiving a high-energy diet.

We aimed to investigate differences in the synthesis and metabolism of intramuscular collagen in the Longissimus thoracis (LT) muscle between heifers and cull-cows fed high-energy diet. Ten cull-cows, (74.9 ± 3.2 months age, weighing 536 ± 14.55 kg) and ten heifers (18.4 ± 3.2 months age, weighting 310.5 ± 14.5 kg) were fed with high-energy diets for 150 days. The total collagen content did not differ between treatments. Greater collagen solubility was observed in heifers than cull-cows, although no differences in lysyl oxidase activity were observed between treatments. No differences were observed for mRNA expression of CO1A1, MMP2, MMP9 and TIMP2 between treatments. However, cull-cows presented greater mRNA expression of COL3A1, TIMP1 and TIMP3 than heifers. Our data give no indication that feeding a high-energy diet to cull-cows decreases the concentration of intramuscular collagen in the LT muscle or increases its solubility in respect to the collagen solubility in LT muscles from heifers on the same diet.

The effect of bovine vaccines against respiratory viruses administered either intranasal or intramuscular on broncho-alveolar fluid cells of heifers.

BACKGROUND: The knowledge on bovine vaccines against respiratory viruses on bronchoalveolar fluid cells is scarce. OBJECTIVE: To compare the effects of a commercial intranasal (IN) and intramuscular (IM) vaccine against bovine respiratory disease (BRD) complex viruses on bronchoalveolar fluid cells of healthy heifers. METHODS: 21 healthy heifers were assigned to three treatment groups: control (CO, N = 7), intranasally vaccinated (IN) (n = 7), and intramuscularly vaccinated (IM) (n = 7). The IN group received 1 mL of the commercial vaccine in each nostril once containing attenuated BoHV-1, bPIV-3, and BRSV. The IM group was vaccinated with two doses of 2 mL with an interval of 21 days of the commercial vaccine containing attenuated BoHV-1, bPIV-3, and BRSV plus inactivated BVDV. At day 0 (D0), before the first vaccine dose, and at D3, D7, and D21, after the last vaccine dose, airway bronchoscopy was performed to observe local irritation and collect bronchoalveolar lavage fluid (BALF). The bronchoalveolar count, cytological evaluation, bronchoalveolar cell oxidative metabolism, and total bronchoalveolar IgA and IgG were measured. RESULTS: The IN vaccine increased neutrophil cellularity at D7 and D21 and total IgA at D3 in BALF. Total IgA in BALF also increased at D3 and oxidative metabolism of bronchoalveolar cells at D21 lowered compared to the CO group. Following IM vaccination there was no alteration of immunoglobulins or cell oxidative metabolism in BALF. Both vaccines reduced the number of alveolar macrophages. CONCLUSION: Both vaccines induced bronchoalveolar inflammation during the establishment of the vaccine immunity, which was more expressive in the IN protocol.

Genetic traceability of Staphylococcus aureus strains isolated from primiparous dairy cows mastitis, humans and environment in the Northeast region of Brazil / Rastreabilidade genética de cepas de Staphylococcus aureus isoladas de mastite de vacas primíparas, ordenhadores e ambiente de ordenha na região Nordeste do Brasil

This research aimed to investigate the genotypic relatedness of 18 Staphylococcus aureus strains isolated from intramammary infections in primiparous cows and extramammary sites on five dairy herds by rep-PCR using RW3A primers, and by PFGE using the endonuclease SmaI. The isolates were also evaluated in vitro for the susceptibility against beta-lactam antimicrobials drugs (penicillin and oxacillin), considering that beta-lactams are frequently used for treating staphylococcal intrammamary infections. The rep-PCR typing was highly discriminatory (D value= 0.9804) and a total of 15 patterns were detected. The PFGE method was also highly discriminatory (D value= 0.9667) and a total of 13 patterns were observed. A total of 15 out of 18 (83%) isolates were resistant to penicillin and one out of 18 (6%) to oxacillin. In conclusion, these findings confirmed the occurrence of a high genetic diversity of S. aureus strains at the herds and the presence of clonally-related strains only at the same herd, emphasizing a variety of genotypic profiles among the isolates.(AU)

Objetivou-se com este estudo investigar a correlação genética de 18 cepas de Staphylococcus aureus isoladas de infecções intramamárias em vacas primíparas e de locais extramamários em cinco propriedades leiteiras através das técnicas de PCR por sequências palindrômicas extragênicas repetitivas (rep-PCR), usando iniciadores RW3A, e de eletroforese em gel de campo pulsado (PFGE), usando a endonuclease SmaI. Os isolados também foram avaliados in vitro quanto à suscetibilidade aos antimicrobianos beta-lactâmicos (penicilina e oxacilina). A tipagem por rep-PCR foi altamente discriminatória (valor D = 0,9804) e um total de 15 padrões foram detectados. Os isolados de S. aureus foram agrupados em três grupos diferentes (A a C), com 80% de similaridade. A técnica de PFGE também foi altamente discriminatória (valor D = 0,9667) e um total de 13 padrões foi observado. A análise do dendrograma com um coeficiente de similaridade de 80% gerou dois grupos diferentes (A e B). Além disso, cepas clonais isoladas do leite foram identificadas na mesma propriedade pelos dois métodos de tipificação e, apesar da presença de cepas dominantes, nossos resultados sugerem uma alta diversidade genética dentre as cepas de S. aureus analisadas. Um total de 15, dos 18 (83%) isolados, eram resistentes à penicilina e um dos 18 (6%) à oxacilina. Assim, esses achados confirmam a ocorrência de uma alta diversidade genética de cepas de S. aureus nas propriedades e a presença de cepas clonalmente relacionadas apenas na mesma propriedade, enfatizando uma variedade de perfis genotípicos entre os isolados.(AU)

Genetic traceability of Staphylococcus aureus strains isolated from primiparous dairy cows mastitis, humans and environment in the Northeast region of Brazil / Rastreabilidade genética de cepas de Staphylococcus aureus isoladas de mastite de vacas primíparas, ordenhadores e ambiente de ordenha na região Nordeste do Brasil

ABSTRACT: This research aimed to investigate the genotypic relatedness of 18 Staphylococcus aureus strains isolated from intramammary infections in primiparous cows and extramammary sites on five dairy herds by rep-PCR using RW3A primers, and by PFGE using the endonuclease SmaI. The isolates were also evaluated in vitro for the susceptibility against beta-lactam antimicrobials drugs (penicillin and oxacillin), considering that beta-lactams are frequently used for treating staphylococcal intrammamary infections. The rep-PCR typing was highly discriminatory (D value= 0.9804) and a total of 15 patterns were detected. The PFGE method was also highly discriminatory (D value= 0.9667) and a total of 13 patterns were observed. A total of 15 out of 18 (83%) isolates were resistant to penicillin and one out of 18 (6%) to oxacillin. In conclusion, these findings confirmed the occurrence of a high genetic diversity of S. aureus strains at the herds and the presence of clonally-related strains only at the same herd, emphasizing a variety of genotypic profiles among the isolates.

RESUMO: Objetivou-se com este estudo investigar a correlação genética de 18 cepas de Staphylococcus aureus isoladas de infecções intramamárias em vacas primíparas e de locais extramamários em cinco propriedades leiteiras através das técnicas de PCR por sequências palindrômicas extragênicas repetitivas (rep-PCR), usando iniciadores RW3A, e de eletroforese em gel de campo pulsado (PFGE), usando a endonuclease SmaI. Os isolados também foram avaliados in vitro quanto à suscetibilidade aos antimicrobianos beta-lactâmicos (penicilina e oxacilina). A tipagem por rep-PCR foi altamente discriminatória (valor D = 0,9804) e um total de 15 padrões foram detectados. Os isolados de S. aureus foram agrupados em três grupos diferentes (A a C), com 80% de similaridade. A técnica de PFGE também foi altamente discriminatória (valor D = 0,9667) e um total de 13 padrões foi observado. A análise do dendrograma com um coeficiente de similaridade de 80% gerou dois grupos diferentes (A e B). Além disso, cepas clonais isoladas do leite foram identificadas na mesma propriedade pelos dois métodos de tipificação e, apesar da presença de cepas dominantes, nossos resultados sugerem uma alta diversidade genética dentre as cepas de S. aureus analisadas. Um total de 15, dos 18 (83%) isolados, eram resistentes à penicilina e um dos 18 (6%) à oxacilina. Assim, esses achados confirmam a ocorrência de uma alta diversidade genética de cepas de S. aureus nas propriedades e a presença de cepas clonalmente relacionadas apenas na mesma propriedade, enfatizando uma variedade de perfis genotípicos entre os isolados.

Evaluation of performance and carcass traits for a five-cohort All Heifer, No Cow beef production system demonstration herd.

The All Heifer, No Cow (AHNC) beef production system is an alternative to conventional cow/calf production that involves insemination of nulliparous heifers with sexed semen to produce female calves that are early weaned at 3 mo of age. Dams are finished on a high-concentrate diet and harvested before reaching 30 mo of age. Objectives of this research were to document reproductive, feedyard, calf, and carcass performance of an AHNC herd; evaluate effects of carcass maturity on carcass quality; and determine if performance of initial cohorts (i.e., cohorts 1 and 2) differed from sustaining cohorts (i.e., cohorts 3-5). A total of 272 heifers were enrolled in the AHNC system via five annual cohorts. The system was initiated with 51 yearling, Angus-based heifers, and a replicate set (n = 56) was started 12 mo after. Heifers in cohorts 3 (n = 53), 4 (n = 56), and 5 (n = 56) were primarily offspring of prior cohorts (i.e., cohort 3 heifers born to cohort 1 females), but some were purchased to maintain inventory. Angus replacement heifers were purchased in cohorts 3 (n = 26), 4 (n = 26), and 5 (n = 28). Mean (±standard deviation) pregnancy rate at 30 d after fixed-time artificial insemination (AI) with sexed semen was 50.8% ± 9.4%, and 140-d pregnancy rate was 93.0% ± 1.5%. With AHNC, 61.0% ± 6.5% of females replaced themselves with a heifer. During finishing, average daily gain (ADG) was 1.9 ± 0.4 kg • d-1 and dry matter intake (DMI) was 14.9 ± 1.9 kg • d-1. Hot carcass weight (HCW) was 367 ± 35 kg. The USDA grading system classified 20.5% of all carcasses (n = 220) as C maturity (A00 = 100, B00 = 200, etc.), 62.4% ± 29.1% of carcasses as USDA Choice. USDA yield grade (YG) was 2.6 ± 0.7. Based on cohorts 1 and 2, there were no differences (P = 0.96) in Warner-Bratzler shear force values between A and B maturity vs. C maturity carcasses. Across all cohorts, there were no differences in USDA YG, marbling score (MA), and lean maturity between A and B maturity vs. C maturity carcasses; there were differences in age (P < 0.001), bone maturity (P < 0.001), and overall maturity (P <0.001). A comparison of initial vs. sustaining cohorts showed that initial cohorts had lower (P < 0.001) DMI, heavier (P < 0.001) HCW, and more advanced (P < 0.05) bone maturity. However, there were no differences for 30- and 140-d pregnancy rates, ADG, USDA YG, and MA between initial and sustaining cohorts. The AHNC beef production system can effectively produce female calves and quality carcasses for harvest.

Follicular wave dynamics and Growth factors gene expression in Braford heifers.

The objectives of the present study were (experiment 1) to characterized development and dynamics of the dominant follicles (DF) and the corpus luteum (CL) to determine patterns of two (W2) and three (W3) follicular waves in beef heifers, and (experiment 2) to determine gene expression of growth factors gene expression in follicular cells of W2 and W3 heifer. Twenty-eight Braford heifers were used. Dominant follicular and CL were monitored daily by ultrasonography to identify the development W2 and W3 in heifers. Pre-ovulatory DF were aspirated on day 19 in W2 and on day 22 in W3 heifers. In W2 and W3, follicular cells (FC) of gene expression of growth differentiation factor 9, bone morphogenetic protein 15 (BMP15), fibroblast growth factor basic, transforming growth factor beta receptor 1, bone morphogenetic protein receptor type IB and fibroblast growth factor receptor 2 were evaluated. The regression of the DF of the first follicular wave and the emergency of the DF of the second follicular wave began later in the heifers W2 than in W3 (p = .02 and p < .01). The regression of the CL began earlier in the W2 than in W3 group (p < .01). Gene expression of growth factors and receptors was similar between groups. However, higher relative levels of BMP15 was observed in W2 group (p = .07). Results propose that wave patterns were regulated by the development time of the DF in the first wave and the life of the CL. Furthermore, higher levels of BMP15 could produce shorter life of CL. The present work suggest that ultrasonography associated with molecular assays could be used as an easy and effective tool to characterize follicular wave patterns.

Risk factors of S. aureus intramammary infection in pre partum dairy heifers under grazing conditions and molecular characterization of isolates from heifers and cows.

The aims of the research reported here were to identify potential risk factors associated with the presence of Staphylococcus aureus intramammary infection (IMI) in pre partum dairy heifers on 17 dairy farms from three provinces of Argentina and to characterize, at molecular level, isolates from those heifers and lactating cows from two selected herds. A total of 1474 heifers and 4878 lactating cows were studied. The prevalence of Staphylococcus aureus IMI in the heifers, heifers at quarter level and lactating cow mammary quarters was 14.41, 4.82, and 14.65%, respectively. Univariate analysis showed the key variables associated with S. aureus IMI presence in the heifers were: S. aureus IMI prevalence in cows of the lactating herd, the time calves stayed with their dam after birth, the calf rearing system, the place of rearing (own farm or other dairy farm) and fly control on the farm. None of the variables included in the multivariable analysis was associated with the presence of S. aureus IMI in the pre partum heifers, probably due to low variability among management practices used by the farms for rearing the heifer calves. At the molecular level, S. aureus isolates were grouped into three main PFGE clusters and several genotypes within the clusters. Isolates from mammary secretion of pre partum heifers and milk of lactating cows comprised different PFGE clusters in both herds, although two exceptions occurred. The absence of gene fnbpB, which codifies for a virulence factor protein involved in cell invasion by S. aureus, was significantly more frequent in pre partum heifer secretion isolates than in isolates from lactating cow milk. These results suggest that, under these management conditions, isolates from mammary secretions of pre partum heifers do not originate from the milk of lactating cows, but rather other sources to which the heifer is exposed.

Application of longitudinal data analysis allows to detect differences in pre-breeding growing curves of 24-month calving Angus heifers under two pasture-based systems with differential puberty onset.

BACKGROUND: Longitudinal data analysis contributes to detect differences in the growing curve by exploiting all the information involved in repeated measurements, allowing to distinguish changes over time within individuals, from differences in the baseline levels among groups. In this research, longitudinal and cross-sectional analysis were compared to evaluate differences in growth in Angus heifers under two different grazing conditions, ad libitum (AG) and controlled (CG) to gain 0.5 kg day-1 . RESULTS: Longitudinal mixed models show differences in growing curve parameters between grazing conditions, that were not detected by cross-sectional analysis. Differences (P < 0.05) in first derivative of growth curves (daily gain) until 289 days were observed between treatments, AG being higher than CG. Correspondingly, pubertal heifer proportion was also higher in AG at the end of rearing (AG, 0.94; CG, 0.67). CONCLUSION: In longitudinal studies, the power to detect differences between groups increases by exploiting the whole information of repeated measures, modelling the relation between measurements performed on the same individual. Under a proper analysis, valid conclusion can be drawn with fewer animals in the trial, improving animal welfare and reducing investigation costs. © 2019 Society of Chemical Industry.

Calving probability in the first and second reproductive years of beef heifers that reached the recommended body weight at first breeding season

The objective was to evaluate factors that influence calving probability in the first and second reproductive years of beef heifers that reached the minimum recommended body weight (BW) in the first breeding season. Two hundred twenty-seven 24-month-old Charolais × Nellore heifers that mated between 2003 and 2012 were analyzed. The parameters evaluated were: year effect; individual and maternal heterozygosis; percentage of Charolais genotype; average daily gain (ADG) from weaning to the end of the first breeding season; BW at 18 and 24 months of age, end of breeding season, parturition, and weaning; Julian date of calving; and adjusted calf weight at weaning. These variables were subjected to logistic regression. Calving rates in the first and second reproductive years were 58.1 and 49.5%, respectively. Performance until the end of the first breeding season, BW before the first breeding season, and individual heterozygosis affected the calving probability in the first breeding season. In the second breeding season, BW variation from the first breeding season and calving, Julian date of calving, and BW at the end of the second breeding season influenced calving probability. Until the end of the first breeding season, ADG of beef heifers responded positively to the calving probability, even after reaching the usually recommended BW for the first breeding season. Primiparous cows calving at the beginning of the breeding season and gaining more BW between the first and second breeding season are more likely to give birth in the second breeding season.(AU)

Weight gain comparison between heifers fed colostrum or whole milk until weaning

Background: The milk-feeding phase, wherein whole milk is the natural food, is critical to calf development, health, andvitality. However, feeding milk to calves is costly in the rearing system because the milk supplied to calves is not sold. Infarms in which the average production is high, excess colostrum and transitional milk are produced that are used to feedcalves until weaning. The objective of this study was to evaluate the performance of heifers exclusively fed colostrum(including transitional milk) or raw whole milk.Materials, Methods & Results: Immediately after their birth, 83 ear-tagged healthy Holstein Friesian heifers adequatelyreceiving the initial colostrum were separated into two experimental groups. Group 1 (n = 34) was fed only fresh whole milkand group 2 (n = 49) was fed only colostrum diluted in water at a 2:1 ratio. Colostrum was removed from cows until the fifthday after birth and was stored in sanitized disposable plastic bottles, stored in a freezer at -20°C and before administration,the colostrum was thawed. Liquid diets were administered using a bottle twice a day during the first month, namely 2 L inthe morning and 2 L in the afternoon. During the second month, the heifers were fed 4 L once a day in the morning. Theheifers had access to an enclosure with fodder, in addition to concentrate specifically for heifers, which was placed in anindividual trough daily. The leftovers were weighed at the end of the afternoon. The heifers were abruptly weaned whenthey reached a daily intake of 1 kg of concentrate. The heifers were individually weighed at birth and at 30, 60, 90, 120,150, and 180 days. The average weights were 40.4, 54.1, 74.5, 95.1, 108.2, and 126.1 kg in group 1 and 45.4, 58.4, 78.2,95.9, 110.8, and 125.1 kg in group 2. The use of diluted colostrum was satisfactory...(AU)

Reproductive performance of heifers of different weight classes in the first and second mating / Desempenho reprodutivo de novilhas de distintas classes de peso no primeiro e segundo acasalamento

The objective of this study was to evaluate the effect of live weight at first mating on reproductive performance in the first and second reproductive years. For that purpose, the reproductive history of 221 heifers mated for the first time between the years of 2003 and 2012 was evaluated. Heifers were grouped into three weight classes at the age of 24 months: 50-59.9% (55%), 60-69.9% (65%), and 70-80% (75%). The pregnancy rate in the first reproductive year in heifers from weight classes 55%, 65%, and 75% was 38.0%, 56.4%, and 69.0%, respectively. The pregnancy rate in the second reproductive year was not affected by weight at first mating (p > 0.05) and corresponded to 41.6%; 42.1%, and 50.4% in the three weight classes, respectively. The weight class of heifers before mating at the age of 24 months affected reproductive performance at first mating but did not increase the pregnancy rate in the second reproductive year.(AU)

Objetivou-se avaliar o efeito do peso vivo ao primeiro acasalamento de novilhas sobre o desempenho reprodutivo na primeira e segunda monta. Para isso, foi avaliado o histórico reprodutivo de 221 novilhas de corte acasaladas pela primeira vez entre os anos de 2003 até 2012. As novilhas foram agrupadas em três classes de peso vivo aos 24 meses de idade, sendo eles: entre 50 a 59,9% do peso adulto (55%); de 60 a 69,9% do peso adulto (65%) e entre 70 a 80% do peso adulto (75%). A taxa de prenhez no primeiro ano reprodutivo foi de 38,0%; 56,4% e 69,0% às acasaladas com faixa de peso de 55%, 65% e 75%; respectivamente. A taxa de prenhez no segundo ano reprodutivo não sofreu efeito da classe de peso ao primeiro acasalamento (p > 0,05) com valores de 41,6%; 42,1% e 50,4%. A classe de peso antes do acasalamento de novilhas aos dois anos de idade interfere no desempenho reprodutivo na primeira monta, mas não resulta em aumento na taxa de prenhez no segundo ano reprodutivo.(AU)

Reproductive performance of heifers of different weight classes in the first and second mating / Desempenho reprodutivo de novilhas de distintas classes de peso no primeiro e segundo acasalamento

The objective of this study was to evaluate the effect of live weight at first mating on reproductive performance in the first and second reproductive years. For that purpose, the reproductive history of 221 heifers mated for the first time between the years of 2003 and 2012 was evaluated. Heifers were grouped into three weight classes at the age of 24 months: 50-59.9% (55%), 60-69.9% (65%), and 70-80% (75%). The pregnancy rate in the first reproductive year in heifers from weight classes 55%, 65%, and 75% was 38.0%, 56.4%, and 69.0%, respectively. The pregnancy rate in the second reproductive year was not affected by weight at first mating (p > 0.05) and corresponded to 41.6%; 42.1%, and 50.4% in the three weight classes, respectively. The weight class of heifers before mating at the age of 24 months affected reproductive performance at first mating but did not increase the pregnancy rate in the second reproductive year.

Objetivou-se avaliar o efeito do peso vivo ao primeiro acasalamento de novilhas sobre o desempenho reprodutivo na primeira e segunda monta. Para isso, foi avaliado o histórico reprodutivo de 221 novilhas de corte acasaladas pela primeira vez entre os anos de 2003 até 2012. As novilhas foram agrupadas em três classes de peso vivo aos 24 meses de idade, sendo eles: entre 50 a 59,9% do peso adulto (55%); de 60 a 69,9% do peso adulto (65%) e entre 70 a 80% do peso adulto (75%). A taxa de prenhez no primeiro ano reprodutivo foi de 38,0%; 56,4% e 69,0% às acasaladas com faixa de peso de 55%, 65% e 75%; respectivamente. A taxa de prenhez no segundo ano reprodutivo não sofreu efeito da classe de peso ao primeiro acasalamento (p > 0,05) com valores de 41,6%; 42,1% e 50,4%. A classe de peso antes do acasalamento de novilhas aos dois anos de idade interfere no desempenho reprodutivo na primeira monta, mas não resulta em aumento na taxa de prenhez no segundo ano reprodutivo.

Weight gain comparison between heifers fed colostrum or whole milk until weaning

Background: The milk-feeding phase, wherein whole milk is the natural food, is critical to calf development, health, andvitality. However, feeding milk to calves is costly in the rearing system because the milk supplied to calves is not sold. Infarms in which the average production is high, excess colostrum and transitional milk are produced that are used to feedcalves until weaning. The objective of this study was to evaluate the performance of heifers exclusively fed colostrum(including transitional milk) or raw whole milk.Materials, Methods & Results: Immediately after their birth, 83 ear-tagged healthy Holstein Friesian heifers adequatelyreceiving the initial colostrum were separated into two experimental groups. Group 1 (n = 34) was fed only fresh whole milkand group 2 (n = 49) was fed only colostrum diluted in water at a 2:1 ratio. Colostrum was removed from cows until the fifthday after birth and was stored in sanitized disposable plastic bottles, stored in a freezer at -20°C and before administration,the colostrum was thawed. Liquid diets were administered using a bottle twice a day during the first month, namely 2 L inthe morning and 2 L in the afternoon. During the second month, the heifers were fed 4 L once a day in the morning. Theheifers had access to an enclosure with fodder, in addition to concentrate specifically for heifers, which was placed in anindividual trough daily. The leftovers were weighed at the end of the afternoon. The heifers were abruptly weaned whenthey reached a daily intake of 1 kg of concentrate. The heifers were individually weighed at birth and at 30, 60, 90, 120,150, and 180 days. The average weights were 40.4, 54.1, 74.5, 95.1, 108.2, and 126.1 kg in group 1 and 45.4, 58.4, 78.2,95.9, 110.8, and 125.1 kg in group 2. The use of diluted colostrum was satisfactory...

Characterization of the factors associated with the growth phase of dairy cattle in family farming / Levantamento dos fatores associados à cria e recria de fêmeas bovinas de propriedades leiteiras familiares

The aim of this study was to characterize the factors associated with the growth phase of dairy cattle used in family farming. We investigated 20 family-run milk production systems located in the Conceição de Ipanema municipality, MG, Brazil. Farmers were interviewed using a semi-structured survey form containing 152 questions. The questions were aimed at characterizing the farmer, herd, and husbandry system at pre- and post-weaning phases. Data were processed by using Sphinx® software, and descriptive analyses were performed in MS Excel® software. The results showed strengths, including navel healing (100%), location of the calf housing above (45%) or next to the pen (35%), and existence of a sanitary calendar (90%). However, several limitations in the management of calves and heifers were identified, such as lack of zootechnical bookkeeping (55%), manual milking with calf at the foot (65%), absence of herd sizing (100%), no routine weighing of calves (95%), incorrect colostrum management (80%), non-supply of transition milk to calves (85%), and likely failure to diagnose diseases by a fraction of the farmers. Thus, training regarding adequate management practices by extension technicians is imperative, along with the formulation of public policies that comply with the aspirations of family farmers, while promoting their economic and social sustainability.(AU)

O objetivo deste estudo foi caracterizar os fatores associados à cria e recria de fêmeas bovinas de propriedades leiteiras em regime de economia familiar. Foram investigados 20 sistemas de produção de leite familiares localizados no município de Conceição de Ipanema, MG, Brasil. Os produtores rurais foram entrevistados utilizando-se um formulário de diagnóstico semiestruturado contendo 152 perguntas. As questões abordadas envolveram a caracterização do produtor, do rebanho e do sistema de criação de bezerras e novilhas. Os dados foram processados no software Sphinx® e as análises descritivas foram realizadas no software MS Excel®. Os resultados demonstraram pontos fortes, incluindo realização de cura de umbigo (100%), localização dos bezerreiros acima (45%) ou ao lado do curral (35%) e existência de calendário sanitário (90%). Porém, diversas limitações no manejo da criação de bezerras e novilhas foram identificadas, como a não realização de escrituração zootécnica (55%), ordenha manual com bezerro ao pé (65%), ausência de dimensionamento do rebanho (100%), não execução da pesagem rotineira das bezerras (95%), manejo da colostragem incorreto (80%), não fornecimento do leite de transição para as bezerras (85%), além de possível falha no diagnóstico de doenças por parte dos produtores. Assim, é imperativa a disseminação de práticas de manejo adequadas pelos técnicos extensionistas e a formulação de políticas públicas que atendam as aspirações e promovam a sustentabilidade econômica e social dos agricultores familiares.(AU)