Reproductive Performance Of Beef Cows Research Articles

28 Investigating the effects of Chromium Propionate supplementation on reproductive performance of beef cows

Abstract The objective of this study was to explore the effects on reproductive performance of beef cows supplemented with Chromium Propionate during the post-partum and breeding periods. A total of 955 multiparous suckled beef cows located at eight locations were enrolled in the study. Within location cows were stratified based on parity, body condition score (BCS), and days postpartum (DPP) and randomly assigned to one of two treatments: 1) Control- supplementation of a mineral product at 113 g animal/d (n = 484 cows; 16 experimental units); or 2) CrP - supplementation of mineral product at 113 g animal/d containing Chromium Propionate (0.4% animal/d, KemTRACE, Kemin Industries; n = 471 cows; 16 experimental units). Mineral supplementation was offered starting at 45 d pre-breeding, during the breeding season, and until weaning for a total of approximately 150 d. Cows were enrolled in a fixed-time artificial insemination (TAI) using the 7-d CO-Synch+CIDR protocol followed by natural service with clean-up bulls 7 d after TAI, for a 70-d total breeding season. Pregnancy diagnosis was performed by ultrasonography 55 d after TAI and again approximately 40 d after the end of the breeding season. Cow body weight (BW) and BCS were recorded at the beginning of the experiment (d -45), at the initiation of the TAI protocol (d -10), at each pregnancy diagnosis (d 55 and 110), and at weaning (d 150). Mineral intake was estimated based on the difference in weight between offered mineral and refusals. Data were analyzed using the GLIMMIX, for binomial data, and MIXED, for continuous data, procedures of SAS. Cow initial BW and DPP were similar (P > 0.10) between treatments (584 ± 198 kg and 78 ± 3 d, respectively). Estimated mineral intake was similar (P = 0.52) between treatments (119.6 ± 10.3 g and 124.5 ± 10.4 g animal/d, for Control and CrP, respectively). Supplementation of CrP did not influence estrus expression (58.3% vs 61.0% ± 2.5 %; P = 0.45), TAI pregnancy rates (63.1% vs 60.1 % ± 2.9 %; P = 0.56), or final breeding season pregnancy rates (94.2% vs 94.7% ± 2.9 %; P = 0.86), for CrP and Control, respectively. Chromium Propionate supplementation did not affect (P > 0.10) final cow BCS and BW (5.2 ± 0.03; 562.9 ± 169.93 kg). In conclusion, Chromium Propionate supplementation delivered via an oral mineral supplement during the pre-breeding and breeding periods did not influence reproductive performance and changes in BW and BCS of beef cows.

Effect of Vitamin A on Estrous Intensity, Number of Follicles, Follicles Diameter and Pregnancy Rate in Beef Cows

Moringa leaves are used as feed to increase the intensity of estrus. It is assumed that the positive effect on the Moringa leaves is due to the presence of vitamin A. This study aims to see the response of vitamin A as a supplement feed to the reproductive performance of beef cows including estrous intensity, number of follicles, follicle diameter, and pregnancy rate. The research was conducted in September-November 2022 in Lappariaja District, Bone Regency, South Sulawesi Province. 10 cows were used which were divided into 2 groups, each group consisting of 5 cows. Group 1 was the control group without vitamin A and group 2 was supplemented with vitamin A. The data on estrus intensity, number of follicles and pregnancy rate obtained were processed using the Chi-square analysis of 2x2 contingency tables. If the Chi-square test does not meet the requirements, the formula used is the Fisher exact test. While the data on the diameter of the follicles were analyzed by ANOVA test. The results of the research data showed that supplementation of vitamin A had a significant difference (P<0.05) on the intensity of estrous. Meanwhile, the results of the chi-square test on the number of follicles and pregnancy rates (P>0.05) showed that there was no significant difference. Likewise, the ANOVA test on follicle diameter between control cows and vitamin A treated cows did not have a significant difference. Although in this study it did not affect the number of follicles, follicle diameter and pregnancy rate. However, it has an economic effect of 20% on the pregnancy rate in the livestock industry scale.

Reproductive Performance of Beef Cows in Peatlands of Central Kalimantan, Indonesia

Reproductive Performance of Beef Cows in Peatlands of Central Kalimantan, Indonesia

Effect of a Trace Mineral Injection on Performance and Trace Mineral Status of Beef Cows and Calves.

Simple SummaryOften the forage alone does not provide enough trace minerals to meet the needs of grazing cows and their calves, specifically copper and zinc are almost always deficient, with Se varying among geographical locations. The trace mineral status of cows can affect their ability to get and stay pregnant as well as the health of their calf in early life. Injectable trace minerals can provide additional supplemental trace minerals and allow for a known amount of trace minerals to be delivered to each animal. The objective of this trial was to determine the effects of a trace mineral injection on the trace mineral status of cows and calves and the resulting impacts on the reproductive performance of the cows and the growth of their nursing calves. In this study, use of an injectable trace mineral increased the cow’s trace mineral stores, but the non-injected cows had adequate copper and zinc status due to free-choice mineral consumption, and no performance benefits of an injectable trace mineral were observed.The objective was to determine the effects of an injectable trace mineral (TMI; Multimin 90) containing copper (Cu), manganese (Mn), selenium (Se), and zinc (Zn) on trace mineral status and the resulting impacts on reproduction of beef cows and the growth of their calves. Beef cows (n = 200) were assigned to receive TMI or no injection (CON) prior to calving and breeding over two consecutive years. Calves born to cows receiving TMI also received TMI at birth in both years and at 49 ± 1.3 days of age in year 1. The TMI increased (p = 0.01) liver Zn and tended (p = 0.06) to increase liver Cu concentrations. Short-lived effects of TMI on Se were observed. Liver Cu and Zn would have been considered adequate and Se marginal in the CON. Pregnancy due to artificial insemination and overall pregnancy rate did not differ (p ≥ 0.36) between treatments. Use of TMI did not increase calf pre-weaning gain. These data indicate that TMI does not improve the reproductive performance of beef cows with adequate trace mineral status or the pre-weaning performance of their calves.

Silvopastoral system is an alternative to improve animal welfare and productive performance in meat production systems

Climate change is a reality and global surface temperature is projected to rise substantially in the next 80 years. Agriculture practices will have to adapt to climate change, and also help to mitigate this effect using, among other strategies, forest conservation and management. Silvopastoral systems have been adopted in tropical climate livestock areas but their benefits on thermal comfort and reproductive performance of beef cows are not completely known. Therefore, our aims were to compare the microclimate of silvopastoral and intensive rotational unshaded grazing systems in different months and to evaluate physiological variables (Exp. 1 and 2), metabolism, and in vitro embryo production (Exp. 2) in crossbred beef females. Our hypothesis is that the silvopastoral system can improve the thermal comfort of beef heifers and cows and, consequently, also improve dry matter intake, body weight gain, and in vitro embryo production when compared to the unshaded rotational grazing system. In Exp 1, the silvopastoral system decreased body temperature and increased welfare and performance of heifers. In Exp. 2, the silvopastoral system enhanced the body weight but did not affect metabolism and the general reproductive performance, but increased the recovery rate of oocytes in primiparous cows.

The Effect of Supplementary Feeding on the Reproductive Performance of Beef Cows in Supporting the Siwab Program

This study aims to determine the effect of supplementary feeding on the reproductive performance of beef cattle and calf birth weight. Additional feed is given to cows who are pregnant (8-9 months) and after giving birth for 3 months. Additional feed provided is a complete feed prepared from local feed ingredients. The objectives of this supplementary feeding are: maintaining the condition of the mother's body, maintaining normal embryo growth, and accelerating postpartum estrus, as has been done in Megal Village, Pamotan District, Rembang Regency. Provision of additional feed to old pregnant beef cattle (8-9 months) and after giving birth for 3 months in Megal Village, Pamotan District, Rembang Regency. The conclusion of this study is that the provision of additional feed 5 kg / head / day to old pregnant beef cattle and after giving birth for 3 months can reduce the weight loss of beef cattle broods when the availability of feed is limited, increase birth weight of calves and accelerate postpartum estrus. estrus for the first time after childbirth). Provision of additional feed to late pregnant beef cattle and after giving birth is highly recommended, especially in areas where the availability of feed fluctuates.Key words: supplementary feed, reproduction, beef cattle

403 Supplementing omega-6 fatty acids to enhance reproductive performance of beef cows

Abstract Our research group has focused on how Ca salts of soybean oil (CSSO) supplementation, a source of omega-6 fatty acids (FA), impacts reproductive performance of beef cows. In Nelore (Bos indicus) grazing cows assigned to fixed-time artificial insemination (AI), supplementing 100 g/d (as-fed basis) of CSSO for 21 d after AI increased (P < 0.01) pregnancy rates from 38.1% (623/1635 as pregnant/total non-supplemented cows) to 49.0% (843/1720 as pregnant/total CSSO-supplemented cows). These outcomes were later associated with enhanced early embryonic development and pregnancy establishment from supplemental omega-6 FA. More specifically, supplementing 100 g/d of CSSO to Nelore cows increased (P ≤ 0.05) incorporation of omega-6 FA in circulation and in the conceptus, increased (P ≤ 0.04) conceptus length (2.2-fold increase), and upregulated mRNA expression of interferon-tau (4.1-fold increase) on d 15 of gestation. Similar outcomes were noted in B. taurus beef cows receiving 100 g/d of CSSO for 21 d after AI. Supplementing CSSO to Angus-influenced cows increased (P = 0.01) pregnancy rates from 51.7% (193/388 as pregnant/total non-supplemented cows) to 60.2% (226/383 as pregnant/total CSSO-supplemented cows), increased (P < 0.01) plasma concentrations of omega-6 FA, and upregulated (P = 0.05) mRNA expression of interferon-tau in d 15 conceptuses (1.8-fold increase). Across these research efforts, CSSO was mixed with granular feed ingredients and hand-fed to cows, which demands labor and may discourage the use of CSSO supplementation by commercial cow-calf producers. Accordingly, our research group also demonstrated that CSSO inclusion into a self-fed low-moisture block resulted in similar incorporation (P ≥ 0.35) of omega-6 FA in the circulation of Angus-influenced cows compared with CSSO inclusion into a hand-fed granular concentrate. Collectively, CSSO improves reproductive performance of B. indicus and B. taurus beef cows, and may be supplemented via self-fed low-moisture blocks to minimize labor needs.

Effect of live weight of beef cows on calf production efficiency

The objective was to evaluate the development and reproductive performance of beef cows of different body weights at calving were evaluated. Milk yield and calf production efficiency were assessed in secundiparous Braford cows classified at calving according to weight as Light (325.2±3.7 kg), Moderate (347.7±4.0 kg), and Heavy (384.2±4.1 kg). Heavy cows had higher total milk yield than Light cows, but did not differ from Moderate, reflecting in calves weighing at weaning 82.1, 76.6, and 76.9 kg, respectively. Differences on pregnancy rates for Light (90.0%, 18 pregnant cows/2 of eligible cows), Moderate (70.2%, 12 pregnant cows/5 of eligible cows), and Heavy (62.5%, 10 pregnant cows/6 of eligible cows) were not detected. Light cows were more productive and efficient when production performance was adjusted for the pregnancy rates than Moderate and Heavy cows. Production of kilograms of calves adjusted for pregnancy was 20.5, 16.2±0.5, and 14.0±0.5 kg for the Light, Moderate, and Heavy cows, respectively. Heavy and Moderate cows were less efficient as compared with the Light ones for production of calves adjusted for their calving interval. Light cows produce more kilograms of calf/cow, requiring the same amount of milk to produce one kilogram of calf. Light cows also have higher efficiency converting milk into calf weight than Moderate and Heavy cows. The productivity and efficiency of breeding herds should be evaluated by the combination of pregnancy rate and kilograms of weaned calves per cow exposed to breeding.

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

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

Kinerja Reproduksi Induk Sapi Potong pada Usaha Peternakan Rakyat di Kecamatan Mojogedang

<p>This study aims to determine of the reproductive performance of beef cows consists are Simpo<br />cow, Limpo cow and PO cow reared on the livestock. The research was conducted by survey on beef<br />cattle 60 head in the District Mojogedang, Central Java Province from December 2014 through<br />February 2015. The research parameter is post partum estrus (PPE), post partum mating (PPM),<br />service per conception ( S / C), days open (DO). Results of the study were analyzed descriptively.<br />Reproductive performance of Simpo cow, Limpo cow and PO cow are consecutive PPE: 3:56 ± 0.73<br />months, 3.93 ± 0:40 months, and 6.75 ± 4.68 months, PPM: 3.85 ± 0.70 months, 3.79 ± 0:51 months,<br />and 4:42 ± 1.23 months, S / C: 1.45 ± 0:20 times, 1.74 ± 0:07 time, and 1:38 ± 0:38 times, DO: 5:33 ±<br />0:58 months, 8:44 ± 4.65 months, and 9:27 ± 5.93 months, CI: 14:33 ± 0:58 months, 14:44 ± 0.66<br />months, and 14:44 ± 0.66 months. The conclusion shows that the reproductive performance of the<br />Simpo cow, Limpo cow and PO cow in District Mojogedang appears that the value of post-partum<br />estrus (PPE) and post partum mating (PPM) is panjang.Service per conception (S / C) is high. Days<br />open (DO) and calving interval (CI) are both still long.</p>

Agreement among bacteriological findings, vaginal discharges, and endometrial cytology for endometritis detection in postpartum beef cows.

This study aims to demonstrate the relationship among vaginal discharges, bacteriological contamination, and endometrial cytology during 20–30 days postpartum in beef cows. A total of 82 beef cows, aged 3 years to 7 years and at 20–30 days post-calving, were enrolled in this study. All the cows were checked by transrectal palpation, ultrasound, and vaginal discharge collection. Endometrial cytology and bacteriological samples were then collected using a cytobrush technique. Nine of 82 beef cows (10.97%) had abnormal vaginal discharges and clinical endometritis (CE), and nine of 73 clinically healthy cows (12.32%) had subclinical endometritis (SCE). The agreement among endometrial examination, polymorphonuclear neutrophil percentage (PMN %), and vaginal discharge score (0–3) was moderate (k = 0.48, p < 0.01), whereas that between vaginal discharge score (0–3) and bacteriological finding was poor (k = 0.032, p = 0.51). The agreement between bacterial finding and PMN % was also poor (k = 0.15, p = 0.02). Escherichia coli was the most common bacteria isolated from healthy (14.6 %), CE (38.8 %), and SCE (42.8 %) cows. Moreover, E. coli was the major bacteriological risk factor for SCE occurrence. E. coli and Staphylococcus aureus were the most common risk factors for the occurrence of CE. The reproductive performance of beef cows was insignificantly affected by CE and SCE.

Temperament Affects Rangeland Use Patterns and Reproductive Performance of Beef Cows

On the Ground The American beef industry is paying more attention to cattle temperament, but studies examining relationships between temperaments and grazing behavior or animal performance on rangelands are limited. We studied range beef cow temperaments using the behavioral syndromes framework. Cows classified into behavioral type groups on the basis of a suite of correlated behaviors showed contrasting rangeland use patterns and different reproductive efficiency. These differences resulted in temperament-related culling rates over time. We argue that the behavioral syndromes conceptual framework could be a valuable tool to advance current understanding about how cattle temperaments are related to grazing patterns and animal performance on rangeland.

Calm temperament improves reproductive performance of beef cows.

Profitability of a beef operation is determined by the proportion of cows attaining pregnancy early in the breeding season and those that are pregnant at the end of breeding season. Many factors, including temperament, contribute to those reproductive parameters. The objective of this study was to evaluate effects of temperament on reproductive performance of beef cows. In Experiment 1, Angus and Angus-cross beef cows (n = 1546) from eight locations were assigned a body condition score (BCS; 1 = emaciated; 9 = obese) and chute exit and gait score (1 = slow exit, walk; calm temperament; 2 = jump, trot or run; excitable temperament). Cows were grouped with bulls (1 : 25 to 1 : 30; with satisfactory breeding potential and free of venereal disease) for an 85-day breeding season. Pregnancy status and stage of gestation were determined (transrectal palpation) 35 days after the end of the breeding season. Controlling for BCS (p < 0.01) and handling facility (p < 0.0001) and handling facility by temperament score interaction (p < 0.001), breeding season pregnancy rate was lower in excited versus calm cows [88.6% (798/901) vs 94.1% (607/645); p < 0.001]. Cows with an excitable temperament took 24 more days to become pregnant compared to calm cows (median days to pregnancy, 35 vs 59 days; p < 0.0001). In Experiment 2, Angus and Angus-cross beef cows (n = 1407) from 8 locations were assigned scores for body condition and chute exit and gait (as described in Experiment 1) and assigned to bulls (breeding sound and free of venereal disease; 1 : 25 to 1 : 30) for 85 days. Pregnancy status was determined by transrectal palpation at 2 and 6 months after the onset of the breeding season. Controlling for BCS (p < 0.05), pregnancy loss was higher in excited versus calm cows [5.5% (36/651) vs 3.2% (20/623), p < 0.0001]. In conclusion, beef cows with an excitable temperament had significantly lower reproductive performance than calmer cows. The modified two-point chute exit-gait scoring method was repeatable and identified cattle with an excitable temperament.

Suplementação com gordura protegida para vacas de corte desmamadas precocemente mantidas em pastagem natural

Avaliaram-se os desempenhos produtivo e reprodutivo de vacas de corte, bem como o desempenho de seus bezerros, de acordo com os tratamentos alimentares: PRE: suplementação com gordura protegida (GP) 45 dias antes do parto; PREPOS: suplementação com GP 45 dias antes do parto e 63 dias pós-parto; POS: suplementação com GP 63 dias pós-parto; PN: sem suplementação. O desempenho produtivo das vacas não foi influenciado pelo manejo alimentar (P&gt;0,05), exceto para o escore da condição corporal (ECC) no final do período de acasalamento, que foi mais baixo para as vacas do PRE e do PREPOS, sendo que esta última apresentou ECC semelhante ao das vacas do POS e do PN. O intervalo entre partos foi menor para as vacas do tratamento PREPOS - 376 dias -, não diferindo das vacas do PN - 383 dias. As vacas do PREPOS desmamaram 4,4% mais quilos de bezerro para cada 100kg de vaca ao parto - 22,6kg - do que as vacas do PRE e do POS - 21,6kg e 21,6kg, respectivamente - e 8,4% mais quilos de bezerro para cada 100kg de vaca ao parto do que as vacas mantidas em pastagem nativa - 20,7kg. A suplementação com gordura protegida durante os períodos pré e/ou pós-parto não afeta o desempenho de vacas e bezerros.

Optimising reproductive performance of beef cows and replacement heifers

A reproductively efficient beef cow herd is fundamental to meeting the protein and specifically, red meat demand of an ever increasing global population. However, attaining a high level of reproductive efficiency is underpinned by producers being cognisant of and achieving many key targets throughout the production cycle and requires significant technical competency. The lifetime productivity of the beef bred female commences from the onset of puberty and will be dictated by subsequent critical events including age at first calving, duration of the postpartum interval for each successive calving, conception and pregnancy rate and ultimately manifested as length of intercalving intervals and number of calves weaned over her lifetime. Puberty in heifers is a consequence of the interactive effects of genetics and both pre- and post-weaning nutrition. Early onset of puberty is essential to achieving the first main reproductive target for beef cow herds; first calving at 2 years of age. In calved heifers and mature cows, the onset of ovarian activity, postpartum is a key event dictating the calving interval. Again, this will be the product mainly of prepartum nutrition, manifested through body condition and the strength of the maternal bond between cow and calf, though there is increasing evidence of a modest genetic influence on this trait. Following the initiation of postpartum ovarian cyclicity, conception and subsequent pregnancy rate is generally a function of bull fertility in natural service herds and heat detection and timing of insemination in herds bred through artificial insemination. Cows and heifers should be maintained on a steady plane of nutrition during the breeding season, but the contribution of significant excesses or deficiencies of nutrients including protein and trace elements is likely to be minor where adequate pasture is available. While, increased efforts are being made internationally to genetically identify and select for more reproductively efficient beef cows, this is a more long-term strategy and will not replace the need for a high level of technical efficiency and management practice at farm level.

Desempenho de vacas de corte Purunã submetidas a diferentes manejos de amamentação

O objetivo deste trabalho foi avaliar o desempenho ponderal e reprodutivo de vacas de corte submetidas a diferentes manejos de amamentação. Durante a estação de monta, de 85 dias, foram avaliadas 161 vacas de corte da raça Purunã, de acordo com os seguintes manejos de amamentação: desmame precoce, vacas separadas dos seus bezerros aos 75 dias pós-parto; amamentação controlada, vacas separadas de seus bezerros aos 75 dias de idade, mas colocadas para amamentar uma vez ao dia durante a estação de monta; e desmame convencional, vacas mantidas com seus bezerros ao pé até o final da estação de monta, aos 160 dias de idade dos bezerros, em média. As taxas de prenhez não foram significativamente afetadas pelos manejos de amamentação, tendo sido de 97% no desmame precoce, de 96% na amamentação controlada e de 90% no desmame convencional. No entanto, o desmame precoce resultou em menor eficiência reprodutiva (28,26 kg), quando comparado à amamentação controlada (35,09 kg) e ao desmame convencional (35,34 kg). Vacas de corte mantidas em boas condições corporais ao parto e ao início da estação de monta apresentam alta taxa de fertilidade, independentemente do manejo de amamentação dos bezerros.

Effects of vaccination against reproductive diseases on reproductive performance of beef cows submitted to fixed-timed AI in Brazilian cow-calf operations

The objectives were to assess incidence of pregnancy losses, associate this outcome with immunization programs against reproductive diseases, and evaluate the effects of vaccination against bovine herpesvirus-1 (BoHV-1), bovine viral diarrhea virus (BVDV), and Leptospira spp., on reproductive efficiency of Brazilian cow-calf operations. In experiment 1, 7614 lactating Nelore cows from 18 ranches were assigned to the same estrus synchronization and fixed-time AI protocol (ESFTAI; Days −11 to 0). Pregnancy status was determined with transrectal ultrasonography on Days 30 and 120 after AI. Pregnancy loss was deemed to have occurred when cows were pregnant on Day 30 but nonpregnant on Day 120. Incidence of pregnancy loss across all ranches was 4.1%; pregnancy losses were detected (P < 0.10) in 14 ranches but not detected (P > 0.11) in four ranches. Pregnancy loss was lower (P ≤ 0.02) in ranches that vaccinated against BoHV-1, BVDV, and Leptospira spp. compared with ranches that did not vaccinate, or only vaccinated against Leptospira spp. In experiments 2 and 3, lactating Nelore cows (N = 1950 and 2793, respectively) from ranches that did not have a history of vaccinating against reproductive diseases (experiment 2), or only vaccinated against Leptospira spp. (experiment 3), were assigned to the same ESFTAI used in experiment 1. Within each ranch, cows received (VAC) or not (CON) vaccination against BoHV-1, BVDV, and Leptospira spp. at the beginning of the ESFTAI (Day −11) and 30 days after (Day 41) AI. In experiment 2, VAC cows had greater (P ≤ 0.05) pregnancy rates compared with CON on Days 30 and 120. In experiments 2 and 3, pregnancy loss was reduced (P ≤ 0.03) in primiparous VAC cows compared with CON cohorts. In experiment 4, 367 primiparous, lactating Nelore cows previously vaccinated against Leptospira spp. were assigned to the same ESFTAI used in experiment 1. Cows received VAC, or the same vaccine 30 days before (Day −41) and at the beginning (Day −11) of the ESFTAI (PREVAC). Pregnancy rates on Days 30 and 120 were greater (P ≤ 0.05) in PREVAC cows compared with VAC cows. In conclusion, pregnancy losses affected reproductive and overall efficiency of Brazilian cow-calf operations, and might be directly associated with BoHV-1, BVDV, and Leptospira spp. infections. Hence, vaccinating cows against these pathogens, particularly when both doses are administered before fixed-time AI, improved reproductive performance in Brazilian cow-calf systems.

Verificação e calibração do modelo de simulação do desempenho reprodutivo de vacas de corte baseado no escore de condição corporal avaliação interna

O trabalho foi desenvolvido com os objetivos de demonstrar e fazer a avaliação interna do modelo matemático desenvolvido para descrever o processo reprodutivo em sistemas de produção e simular o desempenho reprodutivo de vacas de corte a partir do escore de condição corporal ao parto (ECCPAR). O modelo é baseado na relação entre o ECCPAR e o intervalo parto-concepção (IPC) para vacas com cria ao pé; para novilhas e vacas vazias à concepção, foi baseado na probabilidade de ocorrência. Para a avaliação interna do modelo, foi utilizada a metodologia de verificação e calibração. O uso da técnica de variação dos dados de entrada foi feito por meio da construção de cenários, variando ECCPAR, data de início da estação reprodutiva (IER), data média do parto (DPAR) e ganho médio diário do nascimento ao desmame (GMDND). Esses cenários serviram também para demonstração do modelo. Por meio da calibração, foram escolhidos novos desvios-padrão para as variáveis: período de gestação, GMDND e data média do parto (DPAR). Os testes de degenerescência e independência de sementes geradoras de números aleatórios, após a calibração, comprovaram coerência do modelo na geração de aleatoriedade para as variáveis de interesse. A variação nos dados de entrada indicou eficácia do modelo para simular a dinâmica do processo reprodutivo, no entanto ajustes na taxa de concepção de primíparas são necessários para que o modelo simule valores compatíveis com a realidade.

Effects of the weaning age of calves on somatic development and on reproductive performance of beef cows

This study evaluated body development and reproductive performance of beef cows whose calves were submitted to early weaning (76 days of age), or conventional weaning (148 days of age). It was used 141 Braford cows that calved in 2004, 2005, and 2006 to evaluate weight at calving at 76 days, weight at calving at 148 days, weight at the beginning and end of the breeding season, variation of the average daily weight, body condition, pregnancy rate, and calving interval. Dams of calves weaned at 148 days of age showed daily weight gain higher body weight and better body condition at 148 days of age. The weights at the end of breeding season and average weight gain during the breeding season were higher in early weaning cows than in conventional cows. Pregnancy rate of early weaning cows (86.34%) was higher than those submitted to weaning at conventional age (55.45%). Pasture interval was similar among early weaning cows and conventional weaning cows. The best benefit on reducing weaning age in pregnancy rate was in primiparous cows. There was significant interaction between weaning age and the year for calving interval and milk production. The early weaning of calves carried out at 76 days of age allows cows to better weight recovery in the post-weaning and breeding periods, improving their body condition and consequently increasing pregnancy rate regarding to cows whose calves suckled until 148 days of age.

Modelo de simulação do desempenho reprodutivo de fêmeas bovinas de corte com base no escore de condição corporal

Os objetivos neste trabalho foram desenvolver um modelo matemático dinâmico para descrever o processo reprodutivo em sistemas de produção de bovinos de corte e simular o desempenho reprodutivo do rebanho, com base no desempenho individual das fêmeas, determinado a partir do escore de condição corporal ao parto e da maturidade sexual. Trata-se de um modelo empírico, dinâmico e que contém elementos determinísticos e estocásticos. O desenvolvimento do modelo foi baseado na relação entre o escore de condição corporal (ECC) e o intervalo parto-concepção (IPC) para vacas com cria ao pé. Para novilhas e vacas vazias, a concepção foi baseada na probabilidade de conceber, de modo que, para novilhas, a idade e/ou o peso à puberdade foram fatores limitantes. O modelo tem duas formas de leitura dos dados de entrada: uma do relatório de parição gerado pelo software; e a outra, a partir dos dados de entrada definidos pelo usuário. Os dados de entrada são considerados médias, com exceção dos referentes à estação reprodutiva, e o modelo atribui um desvio-padrão para cada variável, de modo que os dados utilizados na execução do modelo seguem uma distribuição normal. A saída final, em formato de relatórios, fornece, além de outras informações, o total de kg de bezerros desmamados/vaca/ano. É possível alterar valores de entrada para testar o impacto dessas mudanças nas variáveis de resposta. O desenvolvimento do modelo contribuiu para maior compreensão do sistema estudado e permitiu a simulação do desempenho reprodutivo de fêmeas bovinas de corte a partir do ECC ao parto (ECCPAR). Seu uso, para auxiliar no processo de tomadas de decisão no mundo real, depende das próximas etapas do trabalho, como verificação, calibração e validação.