Over 2 years (Year 1, 2009-2010; Year 2, 2010-2011), two separate experiments were conducted to evaluate the effects of winter feeding system (n=3) on beef cow performance, reproductive performance, economics and forage degradability. The three systems (treatments) were grazing pea crop residue (PEA) cv. ‘Performance 40-10’ (Year 1, TDN = 50.2%, CP = 7.3%; Year 2, TDN = 56.9%, CP = 8.9%) in field paddocks, grazing oat crop residue (OAT) cv. ‘Baler’ (Year 1, TDN = 59.1%, CP = 2.9%; Year 2, TDN = 66.9%, CP = 5.3%) in field paddocks, and feeding mixed grass-legume hay in drylot pens (DL) (Year 1, TDN = 61.4%; CP = 8.8%; Year 2, TDN = 52.3%, CP = 12.3%). In the first experiment, 90 dry, pregnant Black Angus cows (Year 1, 629 kg ± 74 kg; Year 2, 665 ± 69 kg) stratified by body weight (BW) and days pregnant were randomly allocated to 1 of the 3 systems. Cows were allocated feed in the field or pen on a 3 d basis and supplemented oat grain daily at 0.4-0.6% BW depending on environmental conditions. Dry matter intake (DMI) was estimated for each system using the herbage weight disappearance method. Cow BW, body condition score (BCS), and rib and rump fat were measured at start and end of trial and cow BW was corrected for conceptus gain based on calving data. When data from the first 20 d were pooled over 2 years, initial cow BW was greater (P < 0.01) for the DL and OAT cows compared to the PEA cows and final cow BW was different (P < 0.01) between all 3 winter feeding systems. The change in BW was also greater (P < 0.01) for DL cows compared to cows on the OAT and PEA treatments. Analysis of the first 20 d of Year 1 study period and the total Year 2 study period, showed a significant (P < 0.01) year by treatment interaction for final BW and BW change. The differences (P < 0.01) in initial BW, final BW and BW change between the first 20 d of Year 1 study period and the total Year 2 study period (20 d) suggest feed quality, animal preference and weather conditions may cause difficulties when grazing residues in winter grazing systems. Analysis of the entire trial period in Year 1 (62 d) indicates differences (P < 0.01) for final BW and BW change between cows on all three systems. The change in rib and rump fat was also different (P < 0.01) between cows in all 3 systems. In Year 2 (20 d), initial BW, final BW and BW change were different (P < 0.01) between DL and PEA cows, and between (P < 0.01) OAT and PEA cows. No difference (P > 0.05) was found for cow rib and rump fat in Year 2 and no difference (P > 0.05) was found for BCS in either Year 1 or Year 2 for cows managed in all 3 systems. Differences (P < 0.05) were observed for calving rate and calf birth weight between the DL and OAT system cows, but not between (P > 0.05) cows managed in the DL and PEA or OAT and PEA systems. Costs per cow per day were $1.22, $1.01 and $2.77 for PEA, OAT and DL systems in Year 1, respectively. In Year 2, cow costs per day were $1.59, $1.44 and $1.84 for PEA, OAT and DL systems, respectively. In experiment 2, three ruminally cannulated, dry Holstein cows were fed a silage based total mixed ration (TMR) of 22 kg barley silage, 7 kg chopped alfalfa hay and 1 kg energy supplement (DAC-485). In-situ degradability was studied to determine the extent of degradation of pea, oat and grass-legume hay collected at start (SOT) and end of test (EOT) in experiment one. Rate of degradation (Kd) of DM was greater (P < 0.01) for PEA EOT compared to HAY, OAT SOT and OAT EOT. Dry matter rate of degradation for PEA SOT was greater (P < 0.05) compared to OAT SOT and OAT EOT. The effectively degradable fraction of CP was greater (P = 0.03) for HAY compared to PEA EOT. The ruminally undegradable fraction of CP was greater (P = 0.03) for PEA EOT compared to HAY. Acid detergent fiber rate of degradation (Kd) was greater (P = 0.01) for PEA EOT compared to HAY, OAT SOT and OAT EOT. Acid detergent fiber rate of degradation for PEA SOT was greater (P < 0.05) compared to OAT SOT and OAT EOT. No differences (P > 0.05) were observed between either OAT SOT and OAT EOT or PEA SOT and PEA EOT for S, D, U, ED or RU suggesting that weathering did not have an effect on the degradability of the forages. The results of these experiments show that it is possible to maintain cow BW through the winter months in Western Canada by grazing oat crop residues, which have the potential to reduce winter feeding costs.

Data from 75 F2 Brahman-Hereford cows of four specific breed combinations, F2 HB (produced by F1 HB sires x F1 HB dams, where “HB” refers to cattle sired by Hereford bulls and out of Brahman cows), F2 BH (produced by F1 BH sires x F1 BH dams), HB x BH and BH x HB, were evaluated for maternal performance at the Texas A&M Research Center near McGregor. Differences between breed combinations were analyzed for calf crop born (CCB), calf crop weaned (CCW), calf survival (CS), birth weight (BW), weaning weight (WW), and cow weight at palpation (PW). The adjusted means for F2 HB, F2 BH, HB x BH, and BH x HB were 0.84 ± 0.06, 0.57 ± 0.07, 0.82 ± 0.06, and 0.62 ± 0.08, respectively, for CCW. F2 HB cows had a 0.27 ± 0.09 higher percent calf crop weaned than F2 BH cows (P < 0.01) and a 0.22 ± 0.11 higher percent calf crop weaned than BH x HB cows (P < 0.05). HB x BH cows had a 0.25 ± 0.08 higher percent calf crop weaned than F2 BH (P < 0.01) and a 0.20 ± 0.10 higher percent calf crop weaned than BH x HB cows (P < 0.05). As 6-year-olds, the adjusted means for cow weight at palpation for F2 HB, F2 BH, HB x BH, and BH x HB cows were 523.65 ± 20.49 kg, 602.61 ± 23.63 kg, 492.84 ± 16.98 kg, and 515.93 ± 22.96 kg, respectively. Averaged across all ages, HB x BH cows weighed 56.59 ± 15.29 kg less than F2 BH cows (P < 0.001) and 41.11 ± 18.92 kg less than BH x HB cows (P < 0.05). Also, F2 HB cows weighed 40.45 ± 17.68 kg less than F2 BH cows (P < 0.05). In this herd, HB-sired cows had higher reproductive efficiency than BH-sired cows. Also, HB-sired cows tended to be lighter than BH-sired cows. Although these differences existed, exact causes could not be determined primarily due to confounding between the birth year of the cow and the sire breed of the cow.

Despite an increase in domestic milk production, the dairy industry in the Dominican Republic (D. R.) has not been able to adequately meet the demand of the ever-growing Dominican population, prompting the government and milk processing plants to sponsor programs which will increase the national production of milk and eventually lead to milk self-sufficiency. One obstacle to this goal is a very low reproductive rate in cows and heifers due in part to the tropical setting. Year-round heat stress may result in abnormal follicular dynamics and decreased oocyte and sperm quality causing reproductive efficiency to decline drastically. The specific purpose of this project was to examine and characterize the reproductive practices and outcomes of the Dominican dairy industry by region and to attempt to identify factors that influence dairy reproductive efficiency. During the course of the study, 43 farms were visited over a 10-week period and evaluated. Farms were chosen throughout 4 of the 5 regions of the country and were selected based on their size (preferably 40 adult cows or more), availability of data, and demonstrated motivation by the owner in improving the herd. Individual herd evaluation was broken into four major components: owner interview, farm evaluation, collection of individual cow reproductive data, and adult cow evaluation. Once observations had been made and catalogued, all data were summarized on the herd level and analyzed descriptively. In addition to descriptive analysis, multiple regression techniques were used to select independent variables which explain most of the variance for each of four reproductive outcomes: days to first service, services per pregnancy, projected calving interval, and service rate. In general, reproductive management practices varied depending on region and farm size. Average lameness within the herd was the most important factor in explaining the variability within services per pregnancy and projected calving interval. As average herd lameness increases by 1 point (based on a 1 to 4 scale), services per pregnancy and projected calving interval increase by 0.65 services per pregnancy and 61.1 days respectively according to the model formulated. Increase in the number of employees involved in estrus detection resulted in higher days to first service. The Santo Domingo region had lower days to first service possibly due to widespread reproductive hormone use within the region. The percentage of Holsteins within the herd was associated with increased services per pregnancy and projected calving interval. Increases in service rate were most closely associated with the type of record category used, indicating that a larger sample population with thorough insemination records may be needed to adequately assess this outcome. In part, reproductive efficiency in the Dominican Republic can be potentially improved by enhancing methods for estrus detection. Mechanical aids to estrus detection (tailhead chalk, K-mar® patches, etc.) may help increase estrus detection efficiency in herds currently only relying on visual observation. Assigning 1-2 people primarily to estrus detection and increasing the frequency of hormone usage may also improve estrus detection efficiency. The main emphasis for Dominican dairy producers, however, should be on preventing new lameness and culling chronically lame cows once it is economically feasible to do so. Reducing the incidence of lameness could, in itself, dramatically improve reproductive efficiency in the Dominican Republic. / Master of Science

The objective of the present study was to evaluate the effects of low input development protocols on Southeastern replacement beef females and their offspring. Fall and spring calving crossbred beef heifers managed through one of two heifer development programs (low input, LOW or conventionally developed, CON) were evaluated for metrics of uterine artery hemodynamics, patterns of heifer and offspring growth, postpartum reproductive performance, and economic efficiency. There were significant treatment × season (P = 0.0001) and season × day (P = 0.003) interactions on heifer body weight (BW) during gestation. There was a season × day interaction on total blood flow (TBF; P = 0.05) whereby TBF increased as gestation progressed and spring calving heifers displayed increased TBF. When adjusted for BW, an additional main effect of treatment was observed (P = 0.0007) in which LOW heifers had increased TBF compared to CON heifers. There were no significant main effects of treatment or season or interactions thereof on the proportion of females cycling at the start of the breeding season (P > 0.05). Additionally, there were main effects of treatment (P = 0.0095; P = 0.02) and season (P = 0.012; P = 0.007) on calf ADG and weaning weights, respectively whereby calves born to CON females grew faster than calves born to LOW heifers, and SPRING calves gained more rapidly than FALL calves. Partial budgeting demonstrated that LOW bred heifers were $250/hd less expensive to purchase than CON heifers due to lighter BW. Calves born to LOW females yielded $6.38 less per calf compared to CON calves. The discrepancy in reproductive efficiency coupled with the failure of LOW females to achieve BW similar to CON females resulted in a difference of $403/hd in average cull value between LOW and CON females in which CON females were worth more. Thus, CON females were $159.18 more profitable than LOW females when purchased as bred heifers and sold at the weaning of their first calf. In conclusion, though uterine artery BF was not negatively affected, low input heifer development resulted in sub-optimal heifer growth, poor first calf performance, and inadequate reproductive efficiency.

Orientador: Mário De Beni Arrigoni / Resumo: Foi avaliado o desempenho reprodutivo de matrizes Brangus de primeira cria, submetidas a dois níveis de suplementação de proteína e energia no pré e pós-parto e, taxas de prenhez ao primeiro serviço frente a um programa de inseminação artificial em tempo fixo. Cento e vinte novilhas Brangus, prenhes, com idade entre 17 e 19 meses, foram divididas entre 3 grupos de tratamento. A distribuição dos animais dentro de cada grupo se deu mediante uma avaliação prévia subjetiva do escore de condição corporal (ECC) e medidas ultrasonográficas da área de olho de lombo (AOL) e espessura de gordura subcutânea (EGS) e estágios de prenhez. O grupo AS, com 43 matrizes. recebeu uma dieta programada para uma ingestão animal/dia, de 0,185 kg de proteína bruta e 0,700 kg de NDT. O grupo T, com 38 animais permaneceu sem suplementação alguma recebendo apenas sal mineral e, para o grupo BS, com 39 cabeças foi fornecida uma dieta para permitir a ingestão animal/dia de 0,122 kg de proteína bruta e 0,105 kg de NDT. Os resultados mostraram diferença significativa para ECC acima de 5,0 com taxa de prenhez em 63 % e ECC abaixo de 5,0 com taxa de prenhes em 41 %. Da mesma forma, animais que obtiveram ganhos no ECC ao longo do experimento mostraram taxas de prenhez de 56 %, enquanto que para animais que perderam ECC, a taxa ficou em 35 %. Para as medidas de AOL e EGS não houve diferenças significativas tendo esta última mostrando taxas de prenhez de 58 % igual e acima de 3,2 mm e 44 % para abaixo de 3,2 mm. Conclui-se que o aumento do ECC teve efeito positivo na taxa de prenhez. / Abstract: Our objective was to study the reproductive performance of primiparous Brangus heifers, assigned to different levels of protein and energy supplementation during the pre and postpartum period. First service pregnancy rates were evaluated and a fixed time artificial insemination protocol was used. One hundred and twenty pregnant Brangus heifers (90 to 150 days pregnant), between 17 and 19 months old, were sorted into three treatments. The body condition score, backfat thickness, rib eye area and days pregnant were used as criteria to sort the heifers among the treatments. A beef scale (1-9) was used to evaluate the body condition score (BCS) and backfat thickness (BT) and rib eye areas (REA) were evaluated by ultrasound. The group AS, with 43 animals, received a supplement that allowed an intake of 185 grams of crude protein and 700 grams of TDN. The group BS, with 39 heifers, received a supplement that allowed an intake of 122 grams of crude protein and 105 grams of TDN and the group T, with 38 animals, rested without supplementation except mineral salt. There was a significant effect for BCS above 5,0 with 63 % pregnancy rate and below 5,0 with 41 % conception rate. The heifers that gained BCS had a pregnancy rate of 56 %, and the heifers that lost BCS had a lower pregnancy rate (35 %), showing the positive effect of the BCS on the pregnancy rates. The REA and BT did not differ between the treatments. Heifers which BT greater than 3,2 mm had a pregnancy rate of 58% and heifers with less than 3,2 mm had 44 % pregnancy rate. It can be concluded that the increase of BCS had a positive effect in conception rate. / Mestre

O presente experimento foi realizado com o objetivo de avaliar o impacto da inseminação artificial em tempo fixo (IATF) na eficiência reprodutiva de vacas de leite de alta produção inseminadas no período pós-parto. Vacas Holandesas com média de 50 dias pós-parto foram distribuídas homogeneamente em um de dois grupos experimentais, levando em consideração a presença ou ausência de corpo lúteo (CL), o escore de condição corporal e a produção de leite. No grupo Controle (G-Controle; n = 490), as vacas foram submetidas à observação do comportamento de aceitação de monta (duas vezes ao dia por uma hora) e inseminadas 12 horas após a primeira detecção. No grupo IATF (G-IATF; n = 495), as vacas receberam um implante auricular de norgestomet, mantido por oito dias, e 2 mg de benzoato de estradiol IM no dia 0 (D0; dia aleatório do ciclo estral). No momento da retirada do implante (D8) foram administrados 150 &micro;g de prostaglandina F2&alpha;, 400 UI de gonadotrofina coriônica eqüina e 1 mg de cipionato de estradiol. A IATF foi realizada de 54 a 56 h após a retirada do implante auricular, concomitante à administração de 100 &micro;g de gonadorelina. Após a IATF, as vacas foram submetidas à observação de cio com subseqüente inseminação, seguindo os mesmos critérios descritos para o G-Controle. Amostras de sangue foram colhidas de um subgrupo de animais (G-Controle, n = 50; G-IATF, n = 58) 5 e 11 dias após a primeira inseminação artificial (IA) para dosagem de progesterona (P4) circulante. Todos os animais foram mantidos no experimento até a terceira IA ou 150 dias após o parto e os tratamentos foram realizados no inverno e no verão. O diagnóstico de gestação foi realizado aos 30 dias pós-IA por ultrassonografia e aos 60 dias pós-IA por palpação transretal. Os dados binomiais foram analisados por regressão logística utilizando o PROC GLIMMIX e as variáveis contínuas por ANOVA utilizando PROC GLM do SAS. Não se verificou interação entre estação do ano e tratamento na análise das taxas de concepção, perda gestacional, intervalo entre IAs, intervalo parto-concepção (IPC) e taxa de prenhez aos 150 dias pós-parto. Os resultados são indicativos de que não existem diferenças nas taxas de concepção entre os diferentes grupos após as IAs (primeira, segunda e terceira). A perda gestacional relativa à primeira IA foi maior nas vacas do G-IATF. Os intervalos parto-primeira IA, parto-segunda IA e parto-concepção foram inferiores para as vacas do G-IATF. Entretanto, o intervalo entre a primeira e a segunda IA foi maior para o G-IATF. Não houve diferença na taxa de prenhez aos 150 dias entre os grupos. Ainda, a taxa de serviço (TS) nos primeiros 21 dias após o período voluntário de espera (PVE) foi maior para o grupo IATF. Entretanto, a TS entre 21 e 42 dias após o PVE foi maior para o G-Controle. As concentrações circulantes de P4 não diferiram entre os grupos e as estações do ano. Concluiu-se que o emprego da IATF 60 dias pós-parto foi eficiente para diminuir o IPC. Contudo, a porcentagem de vacas prenhes aos 150 pós-parto foi semelhante entre os dois tratamentos (Controle e IATF) / The aim of the present study was evaluate the impact of fixed-time artificial insemination (FTAI) on reproductive efficiency of high-producing dairy cows inseminated during the postpartum period. Holstein cows with average 50 days in milk were allocated to one of two groups considering the presence or absence of corpus luteum (CL), body condition score and milk production. On Control group (Control-G; n = 490), the cows were submitted to estrus detection twice per day for one h and were inseminated 12 hours after the first detection. On FTAI group (FTAI-G; n = 495), the cows received a norgestomet ear implant (kept for eight days) plus administration of 2 mg of estradiol benzoate i.m. on Day 0 (random day of the estrous cycle). The implant was removed on Day 8 followed by FTAI 54 to 56 h later and the administration of 100 &micro;g of gonadorelin. On Day 8, cows received 400 IU eCG, 150 &micro:g of prostaglandin F2&alpha; and 1 mg of estradiol cypionate. After FTAI, cows were submitted to estrus detection and artificial insemination (AI) 12 h after. Blood samples were collected from a subset of animals (Control-G, n = 50; FTAI-G, n = 58) on Day 5 and 11 after the first AI to investigate serum progesterone concentration (P4). All animals were maintained on the experiment until 150 days post-partum and the treatments were conducted during the winter and summer. Pregnancy diagnosis was performed by ultrasonography 30 days after AI (Day 30) and by rectal palpation 60 days after AI (Day 60). Binomial data were analyzed by logistic regression using the PROC GLIMMIX and continuous variables by ANOVA using PROC GLM of SAS. No interaction was found between season and treatment when conception rate, pregnancy loss, interval between inseminations, interval from calving to conception and pregnancy rate 150 post-partum were analysed. The results indicate no differences on conception rate among both experimental groups after AI (first, second and third). However, the interval from calving to first and second AI and interval from calving to conception were lower on FTAI-G. No difference on pregnancy rate 150 days post-partum was found among groups. Pregnancy loss after first AI was greater on FTAI-G. The interval from calving to first AI, from calving to second AI and the interval from calving to conception were shorter on FTAI-G. However, the interval between first and second AI was longer on FTAI-G. There was no difference on pregnancy rate 150 days post-partum among treatments. Also, the service rate (SR) 21 days after the voluntary waiting period (VWP) was greater on FTAI-G compared to Control-G. Conversely, the SR was lower between 21 and 42 days after the VWP on FTAI-G. No difference was found in serum concentration of P4 among treatment groups and season. Thus, the use of FTAI 60 days post-partum was efficient to anticipate the conception of high-producing dairy cattle by reducing the interval from calving to conception, but did not increase the pregnancy rate 150 days post-partum

Em relação à reprodução, notamos que os equídeos, ao contrário dos bovinos e outros animais de produção, não são selecionados para tal característica. Isto se deve ao fomento das competições equestres onde são julgadas características de performance atlética, conformação, pelagem e andamento. Neste contexto, o presente trabalho teve como objetivo avaliar por meio de estudo retrospectivo, durante 10 estações de monta, os aspectos reprodutivos dos equídeos do Setor de Equideocultura da Prefeitura do Campus Fernando Costa da Universidade de São Paulo, localizado na cidade de Pirassununga, SP. Foram utilizados 60 éguas, Puro Sangue Inglês, Brasileiro de Hipismo e mestiças com faixas etárias variando de 2 a 23 anos. Ainda, 13 garanhões e 2 jumentos. Para as análises estatísticas foi utilizado o programa SAS (versão 9.3, SAS Institute Inc., Cary, NC, USA), onde probabilidades de P&le;0,05 e entre P&gt;0,05 e &lt; 0,10 indicaram diferenças significativas e tendências, respectivamente. A incidência de perda embrionária precoce entre 14 e 35 dias de gestação (PEP de 14 a 35d) foi maior (P&le;0,05) quando as éguas apresentaram dupla ovulação, éguas que receberam de 4 a 7 aplicações da hCG ao longo vida reprodutiva apresentaram diminuição significativa (P&le;0,05) da resposta esperada, a idade das éguas (2 a 4, 5 a 8 e 9 a 23 anos) não influenciou (P&gt;0,05) no desenvolvimento de folículos hemorrágicos anovulatórios, a presença de cistos endometriais influenciou (P&le;0,05) nos índices de PEP de 14 a 35d, éguas inseminadas artificialmente com sêmen in natura diluído apresentaram maior (P&le;0,05) incidência de endometrite pós-cobertura, éguas de 9 a 23 anos de idade apresentaram maior (P&le;0,05) incidência de infecção uterina, a endometrite influenciou (P&le;0,05) na maior ocorrência de PEP de 14 a 35d e quanto maior o diâmetro do folículo dominantes menores são as chances da égua desenvolver endometrite. O intervalo entre o parto e a primeira ovulação não sofreu efeito (P&gt;0,05) da faixa etária das éguas, não há diferença quanto à fertilidade do primeiro estro após o parto e demais ciclos, não houve efeito (P&gt;0,05) do reprodutor (garanhão ou jumento) no tempo das éguas estudadas, éguas de 9 a 23 anos de idade apresentaram tempo de gestação maior (P&le;0,05) aquelas de 2 a 4 e 5 a 8 anos. Éguas de 9 a 23 anos apresentaram menor (P&le;0,05) taxa de prenhez aos 60 dias e, por fim, todas as estações reprodutivas estudas apresentaram taxa de prenhez próximo ou superior a 80%, exceto a estação reprodutiva 2012/2013. Os resultados obtidos indicam quais possíveis fatores podem interferir nos aspectos reprodutivos e, consequentemente, na eficiência reprodutiva de criações de equídeos. / Regarding reproduction, it has been noticed that equidae, unlike cattle and other farm animals, are not selected for this characteristic. This is due to the promotion of equestrian competitions where athletic performance, conformation, coat and pace are evaluated. In this context, the present work had as objective to evaluate through the retrospective study along 10 breeding seasons, the reproductive aspects of equidae bred in the equideocultural sector of the Fernando Costa Campus administration of the University of São Paulo, located at Pirassununga, SP. Sixty Thoroughbred, Brazilian Sport Horse and mixed breed mares were used, with ages varying from 2 to 23 years. Also, 13 stallions and 2 donkeys were used. Statistical analyzes were performed by SAS program (version 9.3, SAS Institute Inc., Cary, NC, USA), where probabilities of P&le;0.05 and between P&gt;0.05 and &lt;0.10 indicated significant differences and tendencies, respectively. The incidence of early embryonic loss between 14 and 35 days of gestation (PEP from 14 to 35 d) was higher (P&le;0.05) when mares presented double ovulation, mares that received 4 to 7 hCG applications throughout their reproductive life showed a significant decrease (P&le;0.05) of the expected response, the age of the mares (2 to 4, 5 to 8 and 9 to 23 years) did not influence (P&gt; 0.05) the development of anovulatory haemorrhagic follicles, presence of endometrial cysts influenced (P&le;0.05) in PEP rates from 14 to 35 d, artificially inseminated mares with diluted semen showed higher (P&le;0.05) incidence of postbreed endometritis, mares from 9 to 23 years (P&le;0.05) had a higher (P&le;0.05) incidence of uterine infection, endometritis influenced (P&le;0.05) on higher occurrence of PEP from 14 to 35d and the larger the diameter of the dominant follicle the lower the chances of the mare to develop endometritis. The interval between birth and first ovulation did not showed effect (P&gt;0.05) on the age of the mares, there was no difference in the fertility of the first estrus after foaling and other cycles, there was no effect (P&gt;0.05) of the reproductor (stallion or donkey) in the gestation period of the studied mares, mares from 9 to 23 years of age showed a longer gestation period (P&le;0.05 ) than those from 2 to 4 and 5 to 8 years old. Mares aged 9 to 23 years presented lower (P&le;0.05) pregnancy rate at 60 days and, finally, all the reproductive seasons studied presented pregnancy rate close to or greater than 80%, except the reproductive season 2012/2013. The results indicate which possible factors may interfere in the reproductive aspects and, consequently, on the reproductive efficiency of equine breeding.

O presente experimento foi realizado com o objetivo de avaliar o impacto da inseminação artificial em tempo fixo (IATF) na eficiência reprodutiva de vacas de leite de alta produção inseminadas no período pós-parto. Vacas Holandesas com média de 50 dias pós-parto foram distribuídas homogeneamente em um de dois grupos experimentais, levando em consideração a presença ou ausência de corpo lúteo (CL), o escore de condição corporal e a produção de leite. No grupo Controle (G-Controle; n = 490), as vacas foram submetidas à observação do comportamento de aceitação de monta (duas vezes ao dia por uma hora) e inseminadas 12 horas após a primeira detecção. No grupo IATF (G-IATF; n = 495), as vacas receberam um implante auricular de norgestomet, mantido por oito dias, e 2 mg de benzoato de estradiol IM no dia 0 (D0; dia aleatório do ciclo estral). No momento da retirada do implante (D8) foram administrados 150 &micro;g de prostaglandina F2&alpha;, 400 UI de gonadotrofina coriônica eqüina e 1 mg de cipionato de estradiol. A IATF foi realizada de 54 a 56 h após a retirada do implante auricular, concomitante à administração de 100 &micro;g de gonadorelina. Após a IATF, as vacas foram submetidas à observação de cio com subseqüente inseminação, seguindo os mesmos critérios descritos para o G-Controle. Amostras de sangue foram colhidas de um subgrupo de animais (G-Controle, n = 50; G-IATF, n = 58) 5 e 11 dias após a primeira inseminação artificial (IA) para dosagem de progesterona (P4) circulante. Todos os animais foram mantidos no experimento até a terceira IA ou 150 dias após o parto e os tratamentos foram realizados no inverno e no verão. O diagnóstico de gestação foi realizado aos 30 dias pós-IA por ultrassonografia e aos 60 dias pós-IA por palpação transretal. Os dados binomiais foram analisados por regressão logística utilizando o PROC GLIMMIX e as variáveis contínuas por ANOVA utilizando PROC GLM do SAS. Não se verificou interação entre estação do ano e tratamento na análise das taxas de concepção, perda gestacional, intervalo entre IAs, intervalo parto-concepção (IPC) e taxa de prenhez aos 150 dias pós-parto. Os resultados são indicativos de que não existem diferenças nas taxas de concepção entre os diferentes grupos após as IAs (primeira, segunda e terceira). A perda gestacional relativa à primeira IA foi maior nas vacas do G-IATF. Os intervalos parto-primeira IA, parto-segunda IA e parto-concepção foram inferiores para as vacas do G-IATF. Entretanto, o intervalo entre a primeira e a segunda IA foi maior para o G-IATF. Não houve diferença na taxa de prenhez aos 150 dias entre os grupos. Ainda, a taxa de serviço (TS) nos primeiros 21 dias após o período voluntário de espera (PVE) foi maior para o grupo IATF. Entretanto, a TS entre 21 e 42 dias após o PVE foi maior para o G-Controle. As concentrações circulantes de P4 não diferiram entre os grupos e as estações do ano. Concluiu-se que o emprego da IATF 60 dias pós-parto foi eficiente para diminuir o IPC. Contudo, a porcentagem de vacas prenhes aos 150 pós-parto foi semelhante entre os dois tratamentos (Controle e IATF) / The aim of the present study was evaluate the impact of fixed-time artificial insemination (FTAI) on reproductive efficiency of high-producing dairy cows inseminated during the postpartum period. Holstein cows with average 50 days in milk were allocated to one of two groups considering the presence or absence of corpus luteum (CL), body condition score and milk production. On Control group (Control-G; n = 490), the cows were submitted to estrus detection twice per day for one h and were inseminated 12 hours after the first detection. On FTAI group (FTAI-G; n = 495), the cows received a norgestomet ear implant (kept for eight days) plus administration of 2 mg of estradiol benzoate i.m. on Day 0 (random day of the estrous cycle). The implant was removed on Day 8 followed by FTAI 54 to 56 h later and the administration of 100 &micro;g of gonadorelin. On Day 8, cows received 400 IU eCG, 150 &micro:g of prostaglandin F2&alpha; and 1 mg of estradiol cypionate. After FTAI, cows were submitted to estrus detection and artificial insemination (AI) 12 h after. Blood samples were collected from a subset of animals (Control-G, n = 50; FTAI-G, n = 58) on Day 5 and 11 after the first AI to investigate serum progesterone concentration (P4). All animals were maintained on the experiment until 150 days post-partum and the treatments were conducted during the winter and summer. Pregnancy diagnosis was performed by ultrasonography 30 days after AI (Day 30) and by rectal palpation 60 days after AI (Day 60). Binomial data were analyzed by logistic regression using the PROC GLIMMIX and continuous variables by ANOVA using PROC GLM of SAS. No interaction was found between season and treatment when conception rate, pregnancy loss, interval between inseminations, interval from calving to conception and pregnancy rate 150 post-partum were analysed. The results indicate no differences on conception rate among both experimental groups after AI (first, second and third). However, the interval from calving to first and second AI and interval from calving to conception were lower on FTAI-G. No difference on pregnancy rate 150 days post-partum was found among groups. Pregnancy loss after first AI was greater on FTAI-G. The interval from calving to first AI, from calving to second AI and the interval from calving to conception were shorter on FTAI-G. However, the interval between first and second AI was longer on FTAI-G. There was no difference on pregnancy rate 150 days post-partum among treatments. Also, the service rate (SR) 21 days after the voluntary waiting period (VWP) was greater on FTAI-G compared to Control-G. Conversely, the SR was lower between 21 and 42 days after the VWP on FTAI-G. No difference was found in serum concentration of P4 among treatment groups and season. Thus, the use of FTAI 60 days post-partum was efficient to anticipate the conception of high-producing dairy cattle by reducing the interval from calving to conception, but did not increase the pregnancy rate 150 days post-partum

Em relação à reprodução, notamos que os equídeos, ao contrário dos bovinos e outros animais de produção, não são selecionados para tal característica. Isto se deve ao fomento das competições equestres onde são julgadas características de performance atlética, conformação, pelagem e andamento. Neste contexto, o presente trabalho teve como objetivo avaliar por meio de estudo retrospectivo, durante 10 estações de monta, os aspectos reprodutivos dos equídeos do Setor de Equideocultura da Prefeitura do Campus Fernando Costa da Universidade de São Paulo, localizado na cidade de Pirassununga, SP. Foram utilizados 60 éguas, Puro Sangue Inglês, Brasileiro de Hipismo e mestiças com faixas etárias variando de 2 a 23 anos. Ainda, 13 garanhões e 2 jumentos. Para as análises estatísticas foi utilizado o programa SAS (versão 9.3, SAS Institute Inc., Cary, NC, USA), onde probabilidades de P&le;0,05 e entre P&gt;0,05 e &lt; 0,10 indicaram diferenças significativas e tendências, respectivamente. A incidência de perda embrionária precoce entre 14 e 35 dias de gestação (PEP de 14 a 35d) foi maior (P&le;0,05) quando as éguas apresentaram dupla ovulação, éguas que receberam de 4 a 7 aplicações da hCG ao longo vida reprodutiva apresentaram diminuição significativa (P&le;0,05) da resposta esperada, a idade das éguas (2 a 4, 5 a 8 e 9 a 23 anos) não influenciou (P&gt;0,05) no desenvolvimento de folículos hemorrágicos anovulatórios, a presença de cistos endometriais influenciou (P&le;0,05) nos índices de PEP de 14 a 35d, éguas inseminadas artificialmente com sêmen in natura diluído apresentaram maior (P&le;0,05) incidência de endometrite pós-cobertura, éguas de 9 a 23 anos de idade apresentaram maior (P&le;0,05) incidência de infecção uterina, a endometrite influenciou (P&le;0,05) na maior ocorrência de PEP de 14 a 35d e quanto maior o diâmetro do folículo dominantes menores são as chances da égua desenvolver endometrite. O intervalo entre o parto e a primeira ovulação não sofreu efeito (P&gt;0,05) da faixa etária das éguas, não há diferença quanto à fertilidade do primeiro estro após o parto e demais ciclos, não houve efeito (P&gt;0,05) do reprodutor (garanhão ou jumento) no tempo das éguas estudadas, éguas de 9 a 23 anos de idade apresentaram tempo de gestação maior (P&le;0,05) aquelas de 2 a 4 e 5 a 8 anos. Éguas de 9 a 23 anos apresentaram menor (P&le;0,05) taxa de prenhez aos 60 dias e, por fim, todas as estações reprodutivas estudas apresentaram taxa de prenhez próximo ou superior a 80%, exceto a estação reprodutiva 2012/2013. Os resultados obtidos indicam quais possíveis fatores podem interferir nos aspectos reprodutivos e, consequentemente, na eficiência reprodutiva de criações de equídeos. / Regarding reproduction, it has been noticed that equidae, unlike cattle and other farm animals, are not selected for this characteristic. This is due to the promotion of equestrian competitions where athletic performance, conformation, coat and pace are evaluated. In this context, the present work had as objective to evaluate through the retrospective study along 10 breeding seasons, the reproductive aspects of equidae bred in the equideocultural sector of the Fernando Costa Campus administration of the University of São Paulo, located at Pirassununga, SP. Sixty Thoroughbred, Brazilian Sport Horse and mixed breed mares were used, with ages varying from 2 to 23 years. Also, 13 stallions and 2 donkeys were used. Statistical analyzes were performed by SAS program (version 9.3, SAS Institute Inc., Cary, NC, USA), where probabilities of P&le;0.05 and between P&gt;0.05 and &lt;0.10 indicated significant differences and tendencies, respectively. The incidence of early embryonic loss between 14 and 35 days of gestation (PEP from 14 to 35 d) was higher (P&le;0.05) when mares presented double ovulation, mares that received 4 to 7 hCG applications throughout their reproductive life showed a significant decrease (P&le;0.05) of the expected response, the age of the mares (2 to 4, 5 to 8 and 9 to 23 years) did not influence (P&gt; 0.05) the development of anovulatory haemorrhagic follicles, presence of endometrial cysts influenced (P&le;0.05) in PEP rates from 14 to 35 d, artificially inseminated mares with diluted semen showed higher (P&le;0.05) incidence of postbreed endometritis, mares from 9 to 23 years (P&le;0.05) had a higher (P&le;0.05) incidence of uterine infection, endometritis influenced (P&le;0.05) on higher occurrence of PEP from 14 to 35d and the larger the diameter of the dominant follicle the lower the chances of the mare to develop endometritis. The interval between birth and first ovulation did not showed effect (P&gt;0.05) on the age of the mares, there was no difference in the fertility of the first estrus after foaling and other cycles, there was no effect (P&gt;0.05) of the reproductor (stallion or donkey) in the gestation period of the studied mares, mares from 9 to 23 years of age showed a longer gestation period (P&le;0.05 ) than those from 2 to 4 and 5 to 8 years old. Mares aged 9 to 23 years presented lower (P&le;0.05) pregnancy rate at 60 days and, finally, all the reproductive seasons studied presented pregnancy rate close to or greater than 80%, except the reproductive season 2012/2013. The results indicate which possible factors may interfere in the reproductive aspects and, consequently, on the reproductive efficiency of equine breeding.

Biological factors regulating feed efficiency were investigated in replacement beef heifers to establish factors that differ between efficient and less efficient animals. Feed efficiency, measured as residual feed intake (RFI) adjusted for body ultrasound measurements, was determined in forty-seven cross-bred heifers. Reproductive differences between efficient (low RFI) and less efficient (high RFI) heifers were examined. Low RFI heifers had an earlier age at both sexual maturity (P=0.08) and conception (P=0.08), and delivered heavier calves (P=0.006). The potential of fecal progesterone metabolites (FP4M) as an indicator of sexual maturity was examined. Measurements of FP4M present a promising non-invasive alternative technique for determining the onset of sexual maturity. A subset of 36 heifers was used to determine if plasma triiodothyronine (T3) concentrations could be used to predict feed efficiency. Triiodothyronine concentrations a correlation of 0.58 (P=0.001) to those from a quadratic prediction model of RFI in heifers sampled as yearlings. / Research into reproductive characteristics associated with residual feed intake, and to determine the effectiveness of the thyroid hormones as a screening tool for feed efficient animals. / OMAFRA (Ontario Ministry of Agriculture, Food, and Rural Affairs) through the Farm Innovation Program, Agriculture Canada through the Growing Forward Project, the Canadian Cattlemen’s Association through the Beef Cattle Research Council, and the Ontario Cattlemen’s Association.