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Se evaluaron dos fuentes de Cu, Se y Zn en combinación con vitamina E sobre la calidad y estabilidad oxidativa de carne de bovino. Se usaron 799 bovinos (cebú x europeo) aleatorizados a 16 corrales en una engorda comercial de Veracruz. Treinta (30) días previos a la matanza, los tratamientos fueron: suplementación mineral, adicional a la tradicional, con las mismas dosis de Cu, Se y Zn, de fuente quelada o de fuente inorgánica, con y sin vitamina E. El peso a la matanza fue de 450.5 + 30.5 kg. Se seleccionaron aleatoriamente 12 bovinos por cada tratamiento para evaluar variables de calidad en la carne del músculo largo dorsal (rib eye). La carne se mantuvo a -20 °C hasta su proceso. En laboratorio se descongeló y maduró por uno y ocho días a 4 °C. La carne de animales que consumieron minerales inorgánicos tuvo la menor pérdida de agua por descongelación (P

Veterinaria Mexico OA ISSN: 2448-6760 Cite this as: Veterinaria Mexico OA ISSN: 2448-6760 Cite this as: Lassala A, Hernandez-Ceron J, Pedernera M, Gonzalez-Padilla E, Gutierrez CG. Cow-calf management practices in Mexico: Reproduction and breeding. Veterinaria Mexico OA. 2020;7(1). doi: 10.22201/fmvz.24486760e.2020.1.839 . Beef cattle breeding has developed in extensive grazing systems in Mexico, concerning the livelihood of over one million families and affecting the use of natural resources. Reproductive efficiency is a major determinant of both the environmental impact of the herd, and the economic viability of the cow-calf production system. However, as reproductive traits have low heritability, reproductive efficiency can be largely influenced by herd management practices. Thus, a questionnaire was administered as personal interviews to 3280 producers, to investigate the prevalence of practices that could directly influence the reproductive outcome of their cattle. Results show that year-round breeding (93%) and natural service by the bull (97.4%) are the most common mating methods. However, only 41% of producers evaluate the breeding soundness of their bulls, and diagnostic testing for specific reproductive diseases of the sires is barely performed in 20% of the farms. The main declared reason for replacing the bull is old age (26.8%), which is followed by to avoid inbreeding (68.4%). Less than 10% of the operations use methods for the synchronization of the estrous cycle, and most farmers breed their heifers for the first time after 2 years of age (73%). Diagnosis of pregnancy is performed in merely 31% of operations, with 23% of the producers declaring to discard non-pregnant cows. Energy or protein feed supplements are provided to the cattle in 63% of the production units, whilst mineral supplements are given in 79% of the farms. Calves are typically weaned between 6 months and a year of age (85%). Only 16% of operations vaccinate against brucellosis and 17.5% against other reproductive diseases (IBR-DVB-VSR and Leptospirosis). The present study showcases a low frequency of adoption of basic reproductive management practices by cow-calf operations in Mexico. Advancement of these practices, as well as implementation and promotion of associated technologies, denotes an area of opportunity to improve the reproductive efficiency of the national herd.

Veterinaria Mexico OA ISSN: 2448-6760 Cite this as: Gonzalez-Padilla E, Lassala A, Pedernera M, Gutierrez CG. Cow-calf management practices in Mexico: Farm organization and infrastructure. VetMexOA. 2019;6(3). doi: 10.22201/fmvz.24486760e.2019.3.677 . Beef cattle breeding has developed in extensive grazing systems in Mexico, concerning the livelihood of over one million families and affecting the use of natural resources. The diversity of climate, region, land tenure, herd size and poverty level potentially influence livestock farming. To detect areas of opportunity in the use of human, animal and natural resources, and to determine the degree of technological penetration, a structured questionnaire was administered as personal interviews to 3280 producers. Over 50% of farmers have an activity other than cattle breeding, mostly raising crops and other livestock. Weaned calves, primarily destined for the national market, are the foremost commercial product. Nevertheless, 20% of farmers in the northern region export their calves. European X Zebu crossbred cattle are widespread (over 45% of operations), followed by Bos taurus taurus breeds (22%). Criollo and predominantly Zebu cattle are present in

Energy reserve, estimated as body condition score (BCS), is the major determinant of the re-initiation of ovarian activity in postpartum cows. Leptin, IGF-I and insulin are positively related to BCS and are putative mediators between BCS and reproductive function. However, when BCS and body composition dissociates, concentrations of these metabolic hormones are altered. We hypothesized that increasing lean muscle tissue, but not fat tissue, would diminish the reproductive response to oestrus induction treatments. Thirty lactating beef cows with BCS of 3.10±1.21 and 75.94±12 days postpartum were divided in two groups. Control cows (n=15) were supplemented with 10.20 kg of concentrate daily for 60 days. Treated cows (n=15) were supplemented equally, and received a β-adrenergic receptor agonist (β-AA; 0.15 mg/kg BW) to achieve accretion of lean tissue mass and not fat tissue mass. Twelve days after ending concentrate supplementation/β-AA treatment, cows received a progestin implant to induce oestrus. Cows displaying oestrus were inseminated during the following 60 days, and maintained with a fertile bull for a further 21 days. Cows in both groups gained weight during the supplementation period (Daily weight gain: Control=0.75 kg v. β-AA=0.89 kg). Cows treated with β-AA had a larger increase in BCS (i.e. change in BCS: control=1 point (score 4.13) v. β-AA=2 points (score 5.06; P0.05) did not differ between groups. However, the number of cows displaying oestrus (control 13/15 v. β-AA 8/15; P

Although an increase in VEGF expression and synthesis in association with LH has been established; it is unknown if all LH isoforms act similarly. This study evaluated the production of cAMP and VEGF among LH isoforms in two in vitro bioassays. The LH was obtained from hypophyses and the group of isoforms was isolated by chromatofocusing. cAMP production was assessed using the in vitro bioassay of HEK-293 cells and VEGF production was evaluated in granulosa cells. Immunological activity was measured with a homologous RIA. Immunoactivity and bioactivity for each isoform were compared against a standard, by estimating the IC50 and the EC50. The basic isoforms were more immunoactive than the standard. The neutral and the moderately acidic had an immunological activity similar to the standard. The acidic isoform was the least immunoreactive. cAMP production at the EC50 dose was similar among the basic isoforms, the moderately acidic and the standard; for the neutral and the acidic, the EC50 dose was higher. It was observed that compared with the control, VEGF production at the lowest LH dose was no different in the standard and each isoform. In the intermediate dose, a positive response was caused in the standard and the neutral and basic isoforms. Although the acidic isoform showed a dose-dependent response, it was not significant relative to the control. In conclusion, the basic isoform generated the greatest cAMP and VEGF production, similar to the reference standard, and the acidic the smallest.

The aim of this study was to determine the effect of tamoxifen (Tx) and its vehicle, soybean oil (SO), during the critical period of hypothalamic sexual differentiation in newborn male rats, regarding gonadal histomorphology during adulthood. The animals were randomly divided into 3 groups (n = 5 each). An hour after birth, one group was treated subcutaneously with 200 μg of Tx, using commercial SO (20 uL) as a vehicle; another group was treated with only 20 μL of SO; the control group received no treatment. All rats were weighed and sacrificed by cervical dislocation on day 90 post-treatment. Testicles were removed, weighed and processed for histological evaluation. The single administration of Tx and/or SO during the critical period of sexual differentiation of the hypothalamus permanently altered testicular histomorphology, spermatogenesis, and body weight in adulthood. Alterations included vacuolization and reduction in the number of spermatogonia and Sertoli cells. The administration of Tx reduced the testicular weight, the diameter and area of the seminiferous tubules, and the height of the germinal epithelium, and increased the intertubular space. Soybean oil by itself reduced the number of spermatocytes and spermatids more than Tx did. There was no effect on the number of Leydig cells. The possibility that soybean oil can act as an endocrine disruptor deserves greater attention and opens the possibility for the development of new methods of pest control.

The objective of the present study was to determine the relative proportion of gonadotropin isoforms in bovine pituitary glands affected by progesterone. Twelve postpubertal heifers (Swiss-Zebu) were assigned to three groups (n=4): intact animals in the luteal phase of the estrous cycle (diestrus group); ovariectomized heifers with (OVXP) or without progesterone treatment (OVX). Prior to pituitary gland collection, a blood sample was taken from each animal to determine the circulating progesterone concentration. Pituitary protein extractions processed by chromatofocusing were eluted with a pH gradient ranging from 10.5 to 3.5. The LH and FSH eluent was grouped on the basis of the following three criteria: (1) as either a basic (pHor=7.5), neutral (pH 7.4-6.5) and acid (pHor=6.4); (2) according to the pH unit (pHor=10.5-3.5); (3) on the basis of distinct isoforms 12 peaks of which (A-L) were identified for LH and 11 (I-XI) for FSH. The analysis by range of pH and by pH of elution in the OVX and OVXP groups showed no difference in the LH and FSH isoform ratio, but diestrus cattle differs having a greater ratio (p0.05) of basic LH isoforms (87.5+/-0.4%) and lesser ratio (p0.05) of acid isoforms (5.4+/-0.7%). In the diestrus group, the ratio of acid FSH isoform increased (62.1+/-1.7%), while neutral isoforms decreased (5.7+/-0.4%, P0.05). The analysis by isoform type of LH revealed a greater proportion of isoforms C (pH 9.4) and E (pH 9.0) in the groups with circulating progesterone when compared to the OVX group. The heterogeneity of FSH was quantitatively similar in most isoforms in the three groups, with the exception of the predominant isoform (VIII, pH 4.9) that was more abundant in the diestrus group (p0.05). These results indicate that progesterone with other gonad factors influence the pituitary glicosylation altering the relative proportions of gonadotropin isoforms.

This study was aimed at comparing the temporal relationship between estrus, the LH peak and ovulation following estrous synchronization in goats using medroxiprogesterone acetate (MGA) or fluorogestone acetate (FGA). Twenty-four cyclic goats were randomly assigned to two treatments: MGA group (n = 12) that individually received a daily oral dose of 0.22 mg MGA for 12 days, and a FGA group (n = 12) treated for 12 days with intravaginal sponges containing 45 mg FGA. The goats from both groups were treated with a prostaglandin analogue (75g Cloprostenol i.m.) during the last day of their progesterone treatment. Estrous detection was carried out every 4 h after the end of the treatment, and blood samples for the determination of the serum LH concentrations collected at 2 h intervals for 24 h from the onset of estrus. Ovulation was detected with the aid of transrectal ultrasonography, performed every 4 h starting 15 h after the onset of estrus. All goats showed estrus. In the MGA group the onset of estrus occurred later and was more variable in relation to the end of treatment (86.7 ± 3.9 h), compared to the FGA group (44.4 ± 1.5 h; P < 0.01). The interval between the LH peak and ovulation was significantly (P < 0.05) longer in the MGA group (26.2 ± 1.1 h) than the FGA group (22.4 ± 0.8 h). There were no differences regarding the intervals from the onset of estrus to the LH peak (14.9 ± 1.8 and 15.3 ± 0.9 h) and to ovulation (40.1 ± 2.3 and 37.6 ± 0.5 h) for the MGA and FGA groups, respectively. The amplitude of the LH peak was not different between groups. It could be concluded that the timing of the LH peak and ovulation is not related to the end of treatment, but with the time of onset of estrus. The longer and more variable interval for estrous demonstration following MGA treatment, represents a serious limitation for its use in synchronization programs in goats, where mating is to be performed on a fixed-time basis.

The pattern of distribution of circulating luteinizing hormone (LH) isoforms in cattle during estrus and the luteal phase was investigated. In each stage, the stage of the estrous cycle was synchronized in seven Holstein heifers with a prostaglandin analogue. After estrus was detected, blood samples were taken at 2-h intervals for 24h. In the luteal phase, animals received 250 microg i.v. of GnRH and blood samples were collected every 15 min for 5h. LH concentration in the samples was determined. Samples with the greatest LH concentration in estrus (pre-ovulatory peak) and those collected 60 min after GnRH administration (luteal phase) were analyzed by chromatofocusing, eluted with a pH gradient from 10.5 to 3.5. Eluted LH was grouped into basic (pH > or = 7.5), neutral (pH 7.4-6.5) and acidic isoforms (pH < or = 6.4) as well as by pH unit. In both phases, basic forms were the most abundant, and these were greater (P < 0.05) during the luteal phase (78.4 +/- 4.2%) as compared with during estrus (57.1 +/- 6.2%); the proportion of neutral and acidic isoforms in estrus (13.7 +/- 2.6%; 28.5 +/- 2.8%) was greater (P < 0.05) as compared with the luteal phase (3.0 +/- 0.7; 18.7 +/- 3.4). These results indicate that the relative proportion of LH isoforms secreted by the adenohypophysis differ by stage of estrous cycle. The addition of excess of NaCl to the column modifies the antigen-antibody binding in the RIA, and the proteins eluted are erroneously quantified as LH; this is an artifact of the technique.

The objective of the present study was to compare the effectiveness of ultrasound measurements (ULT), body condition score (BCS) and body mass index (BMI) to predict body fat and muscle in goats. Twenty-four adult, ovariectomized, creole goats were fed individually to achieve dissimilar stable body weights (26 to 66 kg). After a six-week period of stabilization BCS was evaluated (average of 4 separate evaluations) and BMI calculated (BW/(length x height)x10; average of 2 independent length and height measurements). Fat and muscle coverage over the dorsal (12-13th), lumbar (1st) and coxal (1st) vertebrae were measured by ultrasound imaging. Animals were slaughtered and visceral fat dissected and weighed. Left half carcass weights were obtained and muscle and fat were dissected and weighed. Left half carcass data were adjusted to whole carcass data. Simple  regression analyses were performed with ULT, BCS and BMI as predictors and visceral (VF), carcass (CF) and total fat (TF), and muscle (MU) as response variables. Coefficients of variation (CV) were calculated for BCS and BMI estimations. ULT measurement of total tissue (fat + muscle) coverage over dorsal vertebrae presented the highest predictive value for ULT measurements; thus this measurement is the only reported. Coefficients of determination (R2) for VF, CF and TF were .55, .76 and .68; .78, .82 and .87; .81, .81 and .88 for ULT, BCS and BMI as predictors. R2 for MU were .67, .84 and .76 using ULT, BCS and BMI as predictors. R2 for proportions of VF/BW, CF/BW and TF/BW were .47, .73 and .65; .75, .78 and .88; .74, .71 and .85; when ULT, BCS and BMI were used as predictors. R2 for MS/BW were ≤ .10 using ULT, BCS and BMI as predictors. CV was greater in BCS estimation as compared to BMI estimation (9.7 vs. 3.1 %). BCS and BMI were more accurate in vivo predictors than ULT for body fat content, fat as proportion of BW and body muscle content. ULT, BCS and BMI were completely worthless for predicting muscle as proportion of BW. BMI estimation was less variable than BCS estimation. This study, for the first time, provides a predictive value of BMI for body fat and muscle content in goats.

La hormona luteinizante (LH) sufre modificaciones postraduccionales que dan origen a isoformas de carga. El estudio determinó la actividad biológica (B) e inmunológica (I) de distintas isoformas de LH bovina. Las isoformas se aislaron mediante el cromatoenfoque a partir del extracto glicoprotéico obtenido de lóbulos anteriores de hipófisis de bovino.La actividad biológica se evaluó en un bioensayo in vitro midiendo la producción de AMPc. La actividad inmunológica se midió con un radioinmunoensayo (RIA) específico para LH. El USDA-bLH-B5 se utilizó como referencia. Las isoformas se agruparon tomando como referencia el rango de pH de elución, en básicas (A, pH, 10.75-9.75; B, pH, 9.58-8.41), neutras (C, pH, 7.98-6.89) y ácidas (D, pH, 6.88-5.41; E, pH, 5.36-3.46). El peso molecular del heterodímero de cada isoforma y del estándar fue similar, estimado en 36.5 kDa. La actividad inmunológica y biológica se comportó de forma dosis-dependiente. Con respecto al estándar, se requirió una mayor concentración de proteína de cada isoforma para obtener el IC50 en la curva de inhibición. En el bioensayo, el valor EC50 para la producción de AMPc fue significativamente diferente entre isoformas; la isoforma neutra mostró un EC50 inferior lo que se interpretó como la proteína más bioactiva, en contraste, la isoforma ácida, mostró un valor de EC50 superior y resultó ser la menos bioactiva; la básica tuvo un comportamiento intermedio (P

In beef cows, reduced energy intake delays first ovulation postpartum and is associated with lesser insulin, IGF-I and leptin concentrations. However, the close relationship among these hormones mask their individual roles in the reinitiation of ovarian activity. A β-adrenergic receptor agonist (βAR) was used to increase body condition score (BCS) and yet reduce body fat and leptin serum concentration to determine the specific role of leptin in the postpartum ovarian activity. Beef cows (n=77) with BCS 3.1 ± 1.4 received 2 kg/day of feed containing 0 or 0.15 mg/kg of zilpaterol (a synthethic βAR), for 33 days. Estrus was induced with a progestin implant applied for 9 d and cows in estrus were bred by artificial insemination (AI). Zilpaterol administration increased (P0.05) daily weight gain, muscle depth and BCS, with no changes in back fat depth, reducing fat to muscle ratio (P0.05). At the time of AI, insulin (38%) and IGF-I (26%) concentrations were less in zilpaterol-treated cows (P0.05), but leptin concentration was unaffected. Ovulation rate and animal with luteal activity after estrus induction were also reduced by 35% (P=0.05) and 56.5% (P=0.007), respectively, in zilpaterol-treated cows. Logistic regression estimates for BCS (P=0.016) and IGF-I concentration (P=0.03) were positively related with the occurrence of luteal activity. In addition, whilst back fat (P=0.009) had a positive effect on luteal activity, leptin concentration did not show a significant relationship. In conclusion, despite an increase in body weight and a positive change in BCS, the reduction in insulin and IGF-I concentrations, associated with βAR treatment, reduced the response to induction of estrus. However only IGF-I, but not leptin or insulin, significantly influenced the odds for the occurrence of luteal activity after estrous induction in cattle with poor BCS.

Apoptosis of granulosa cells during follicular atresia is preceded by oxidative stress, partly due to a drop in the antioxidant glutathione (GSH). Under oxidative stress, GSH regeneration is dependent on the adequate supply of NADPH by glucose-6-phosphate dehydrogenase (G6PD). In this study, we analyzed the changes of G6PD, GSH, and oxidative stress of granulosa cells and follicular liquid and its association with apoptosis during atresia of small (4–6 mm) and large (>6 mm) sheep antral follicles. G6PD activity was found to be higher in granulosa cells of healthy small rather than large follicles, with similar GSH concentration in both cases. During atresia, increased apoptosis and protein oxidation, as well as a drop in GSH levels, were observed in follicles of both sizes. Furthermore, the activity of G6PD decreased in atretic small follicles, but not in large ones. GSH decreased and protein oxidation increased in follicular fluid. This was dependent on the degree of atresia, whereas the changes in G6PD activity were based on the type of follicle. The higher G6PD activity in the small follicles could be related to granulosa cell proliferation, follicular growth, and a lower sensitivity to oxidative stress when compared with large follicles. The results also indicate that GSH concentration in atretic follicles depends on other factors in addition to G6PD, such asde novosynthesis or activity of other NADPH-producing enzymes. Finally, lower G6PD activity in large follicles indicating a higher susceptibility to oxidative stress associated to apoptosis progression in follicle atresia.

"Se evaluó la eficacia biológica de dos sistemas de apareamiento en ovinos del altiplano central de México. Un total de 300 ovejas adultas y 60 de reemplazo de la raza Columbia se distribuyeron al azar en dos grupos de 150 adultas y 30 jóvenes (edad promedio al primer parto de 18 meses). En el primer grupo (sistema intensivo) se realizaron empadres de 36 días, con monta natural cada ocho meses (marzo, noviembre y julio), mientras que en el segundo grupo (sistema anual) se llevó a cabo un empadre de 45 días, iniciando en noviembre de cada año. En todos los casos, quince días antes del empadre se introdujeron machos marcadores, que en la fecha de inicio del empadre se sustituían por sementales en proporción de un macho por cada 20 hembras. Mensualmente se evaluó la condición física de todas las hembras. Los animales pastorearon de ocho a nueve horas diarias en praderas de alfalfa (Medicago sativa) y pastos orchard (Dactylis glomerata) y rye grass (Lolium perenne) irrigadas por aspersión. Solamente las ovejas del sistema intensivo recibieron complemento durante la lactancia y el reempadre. En los dos sistemas se lograron apareamientos en todas las épocas, la fertilidad en los tres empadres del sistema intensivo fue de 83.9%, mientras que el promedio de los dos empadres anuales fue de 88.3% (P < 0.05). En el mismo orden, la prolifi cidad fue de 1.12 vs 1.32 (P < 0.05); la mortalidad al destete, 5.3% vs 6.4% (P > 0.05); la tasa de destete, 0.89 vs 1.09 (P < 0.05); el número de corderos destetados por oveja en dos años fue de 2.5 vs 2.0, y de kg de cordero de 55.9 vs 44.4 kg (P < 0.05). Independientemente del tipo de empadre, las ovejas adultas fueron superiores a las jóvenes en todos los parámetros evaluados (P < 0.05). Los resultados de este estudio permiten comparar la eficacia biológica entre un sistema de apareamiento intensivo cada ocho meses y uno anual, también muestra la posibilidad de aparear ovejas de la raza Columbia en forma intensiva."

Se evaluó el efecto de consumo de trigo protegido contra la degradación ruminal sobre la actividad ovárica. Cuarenta (40) cabras criollas recibieron 11 días previos al estro 33.2 g/kg.75 de trigo cristalino mezclado con formaldehído al 5% y 15 % de sebo saponificado (TT) o trigo cristalino molido, y por separado 15 % de sebo saponificado (TST). Los días 0, 2, 4 y 6 postestro se caracterizaron las poblaciones foliculares ováricas, y el día 9 el número de ovulaciones. Se colectaron muestras sanguíneas seriadas post-consumo de trigos en cuatro animales/grupo determinándose las concentraciones séricas de insulina y glucosa. Para el análisis estadístico se aplicó la Prueba de Fisher o ANDEVA para un diseño completamente al azar. No se encontraron diferencias (P0.20) en el número de ovulaciones ni en las concentraciones de glucosa post-consumo de trigos. Las concentraciones de insulina fueron mayores (P0.05) en el grupo TT vs TST durante el periodo de 0-8 h post-consumo de trigos (6.61 vs 4.82 µUI/ml). El número de folículos 4 mm el día 0 post-estro fue mayor en TT vs TST (7.60 vs 7.00 folículos; P0.01) y el número de folículos totales al día 0 y el diámetro del 2ndo folículo en tamaño al día 6 post-estro tendieron a ser mayores en TT vs TST (9.70 vs 9.21 folículos y 2.89 vs 2.75 mm; P0.10). El consumo por períodos cortos de TT, es capaz de influenciar el desarrollo folicular en cabras criollas sin alterar la tasa ovulatoria o el ingreso de glucosa a la circulación periférica, pero sí incrementando temporalmente la secreción de insulina

The objective was to characterize testicular development in Blackbelly sheep, focusing primarily on Sertoli cell number. Lambs ( n = 43) were allotted into eight groups, and surgically castrated at 0, 3, 6, 9, 12, 15,18 or 21 weeks of age ( n = 4–6 lambs per group). Testes were fixed and paraffin-embedded, cross-sections (5 μm) were stained and evaluated with quantitative morphometry techniques. Testis weight increased at a greater rate between 9 and 15 weeks of age, which was associated with remarkable changes in testicular histology, including increases in tubular tissue volume, and tubule diameter and length. Spermatogenesis started in a period between 9 and 12 weeks, lumen and elongated spermatids were observed for the first time at 12 weeks (78% of the tubules) and 15 weeks (37% of the tubules), respectively. Total number of Sertoli cells (mean ± S.E.M.) increased steadily from birth (531 ± 76 × 10 6 ) to 15 weeks (12,008 ± 1722 × 10 6 ), with no changes afterwards. Sertoli cell number per gram of testicular tissue decreased as lambs were older, with the most remarkable change occurring between Weeks 9 and 12. An early increase in serum LH was observed at 6 weeks of age, with testosterone (T) increasing at Weeks 12 and 21. In conclusion, Sertoli cells maintained the capacity of proliferating from birth to 15 weeks of age in Blackbelly sheep; furthermore, the period of accelerated testis growth was associated with increased serum T concentration and with important changes in testicular morphology, as a consequence of the beginning and establishment of spermatogenesis and Sertoli cell maturation.

The relative proportion of the circulating luteinizing hormone isoforms in goats during follicular phase (pre-ovulatory peak; F) and anestrus (A) was investigated. Estrus was synchronized in six goats with a prostaglandin analogue. After estrus was detected, blood samples were taken at 1 h intervals for 24 h. Four anestrous goats received 100 microg i.v. of GnRH and blood samples were collected every 15 min for 5 h. Samples with the greatest LH concentration in follicular phase and after GnRH administration (anestrus) were analyzed by chromatofocusing and eluted with a pH gradient from 10.5 to 3.5. For quantification purposes eluted LH was grouped into basic (pHor =7.5), neutral (pH 7.4-6.5) and acidic isoforms (pHor =6.4) as well as by pH unit. In both physiological conditions (PC), basic and acidic isoforms were greater than the neutral. With this grouping criteria, there was an interaction between PC and pH group, with the proportion of neutral isoforms being greater (p0.05) in A (12.0+/-0.8%) as compared with F (5+/-2%). Analysis by pH unit showed a very basic group of eluted isoforms (pHor =10), which amounted to a percentage of 6.0+/-0.4% of the total observed during A, and 3+/-1% during F (p0.05). Predominant isoforms in A eluted in the pH range 9.99-9.0 (42+/-3%) as compared to 7+/-3% (p0.01) in that pH range in F. In contrast, the predominant isoforms in F eluted in the pH range 8.99-8.0, representing 55+/-8%, while in A the proportion was 11+/-2% (p0.01). Isoforms eluted at the pH range 7.9-7 represented a significantly greater proportion during A (5.0+/-0.6%) as compared with F (3+/-1%). This is the first report on goat LH circulating isoforms. During A the LH isoforms secreted by the pituitary are more basic than during F.

The luteinizing hormone (LH) is secreted in multiple molecular forms into the blood stream; however, few studies have characterized the pattern of the circulating LH isoforms in domestic animals during different physiological stages. Most of the publications are related to the pattern of isoforms present in the anterior pituitary gland. This review includes recent evidence concerning the distribution of LH isoforms in the pituitary gland and serum in ruminants. The structural heterogeneity of this hormone is emphasized, including the glycosylation biosynthetic pathway, as well as the different proportions of oligosaccharides that confer particular functional characteristics to the heterodimer. Evidence for a regulating role of GnRH, estradiol and progesterone is discussed.

Los objetivos fueron determinar los efectos del estrés calórico, la producción láctea y sus interacciones con las prácticas de manejo, sobre la tasa de gestación (GEST) de vacas Holstein. Se analizaron 23,926 registros de inseminación artificial de nueve hatos lecheros de Cd. Delicias, Chihuahua. Por cada unidad de incremento del índice temperatura/humedad promedio del mes, la GEST disminuyó en 0.7 % (P0.01). La GEST se redujo a partir del mes de mayo y se mantuvo en ese nivel hasta el mes de octubre, cuyos valores fueron inferiores a lo observado de noviembre a abril (P0.01). Las vacas con producción de leche estimada a 305 días (PROD) superior a 11,000 L tuvieron menor GEST (P0.01). De junio a octubre las vacas con PROD superior a 10,000 L mantuvieron GEST por debajo a lo observado en vacas con menor nivel de PROD (P0.01). La GEST se redujo con índices temperatura/humedad en el día del servicio (THIS) de 72 y mayores (P0.01), cuyo efecto fue más severo cuando el THIS fue superior a 78 (P0.01), excepto en vacas con PROD menor a 7,000 L (P0.05). Las vacas multíparas tuvieron menor GEST a THIS superiores a 72, que las primíparas (P0.01). La administración de somatotropina bovina (BST), el número de ordeños por día y sus interacciones con THIS, así como tamaño del hato no afectaron la GEST (P0.05). La PROD fue mayor en vacas con más de dos partos, con administración de BST, con esquemas de tres ordeños por día y las que se manejaron en hatos grandes (P0.01).

Los objetivos del estudio fueron determinar los efectos del mes de servicio y los índices temperatura-humedad el día del servicio y sus interacciones con otras variables de manejo y productivas sobre la tasa de gestación (GEST) en vacas lecheras. El estudio se realizó en siete hatos lecheros de Aguascalientes. Una relación negativa fue observada entre el índice temperatura-humedad promedio del mes de servicio (THI) y la GEST (P 0.01), donde por cada unidad de incremento del THI se redujo la GEST en 1.03% (P 0.01). La GEST fue menor de mayo a septiembre que de octubre a abril (P 0.05). Las vacas con PROD mayor a 8 500 l tuvieron menor GEST en octubre, noviembre, diciembre y enero (P 0.05), que las de PROD menor. Los índices temperatura-humedad el día del servicio (THIS) afectó la GEST en vacas de todos los estratos de producción. Sin embargo, en vacas con producción mayor a 8 500 l, el THIS mostró efecto negativo en GEST a valores mayores a 75.9, en comparación con las vacas de menor producción que fueron afectadas desde THIS 74. Esto pudo deberse a la baja GEST de las vacas de alta producción ( 35%), aun en THIS confortables. A THIS mayores a 76 no se observaron diferencia en GEST debidas al nivel de producción. Las vacas primíparas mostraron mejor GEST que las multíparas (P 0.01). El uso de somatotropina no afectó la GEST (P 0.05). Las vacas con tres ordeños y hatos con más de 1 000 vacas tuvieron menor GEST (P 0.01). Las interacciones de THIS con el número de partos, con la administración de somatotropina o no y con el número de ordeños no fueron signifi cativas sobre GEST (P 0.05). La gestación fue afectada por el mes de servicio y por el índice temperatura-humedad. Sin embargo, el efecto es mayor y más perdurable en vacas con mayor PROD.

The study describes the purifi cation of fi ve LH isoforms from bovine pituitary extracts. Cationic interchange chromatography was used to obtain fractions at a pH of 6.8 and 9.5. These were then repurifi ed under identical conditions in DEAE-Sephacel to obtain LH-I (1.2 mg/kg of pituitary), and LH-II (1.8 mg/kg), LH-III (1.5 mg/kg), LH-IV (1.2 mg/kg) and LH-V (7.0 mg/kg), respectively. The relative mobility (Rf) of each isoform was determined using polyacrylamide gel electrophoresis under native conditions. LH-I presented an Rf of 0.16 cm; LH- II, LH-III and LH-IV had an Rf of 0.044 cm, while LH-V had a 0.11 cm Rf. The molecular weight (MW) of LH-I and LH-V was 37.5 kDa, while LH-II, LH-III and LH-IV had a MW of 38.5 kDa. The immunotransference analysis identifi ed MW bands weighing 59.0, 37.5 and 22.0 kDa in the standards as well as in the different isoforms. The in vivo biological potency corresponded to 1.04 U/mg (LH-I); 5.9 U/mg (LH-II); 0.16 U/mg (LH-III); 0.86 U/mg (LH-IV) and 1.4 U/mg (LH-V) and their LH radioinmmunoassay (RIA) 50% expected dose (ED50) were 2.27 ng/tube (LH-I), 1.19 ng/tube (LH-II), 1.35 ng/tube (LH-III), 0.66 ng/tube (LH-IV) and 1.71 ng/tube (LH-V). These data show that it is possible to obtain two LH isoforms at pH 6.8 (I and V) and three at pH 9.5 (II, III and IV), with heterogeneous charges, RIA and biological activity, with suffi cient yield as to try to develop simpler and more precise analytical methods.

Para establecer factores que influyen en el peso al nacimiento (PN) a los 30 d y 60 días, se utilizaron los registros de 917 corderos Columbia, producto de un sistema de apareamiento anual (S-A) con partos en abril y uno cada ocho meses (S-I), con partos en abril-mayo (A-M), diciembre-enero (D-E) y agosto-septiembre (A-S), bajo condiciones de pastoreo intensivo en praderas irrigadas de clima templado. Desde los 15 días, los corderos dispusieron de suplemento. En el análisis los efectos fijos incluyeron: Edad de la madre, tipo de parto, sexo y dentro de sistema, época o año. Se realizaron correlaciones lineales entre pesos al nacer 30 y 60 días y la condición corporal de las madres. El PN (5.7 ± 0.06 kg) y a 30 d (15.0 ± 0.17 kg) del S-I fue mayor (P 0.05) que del S-A (5.5 ± 0.06 kg y 13.8 ± 0.17 kg), desapareciendo la diferencia a 60 d (21.5 ± 0.25 kg vs. 21.4 ± 0.24 kg). Independientemente del sistema, los corderos únicos y los machos fueron más pesados del nacimiento a 60 días que los dobles o las hembras (P 0.05). El S-A no mostró diferencias entre años en PN o 60 días (P 0.05), pero sí a los 30 días (14.7 ± 0.22 kg vs. 13.2 ± 0.18 kg). En el S-I, los nacidos en D-E fueron más pesados (P 0.05) al nacimiento 30 días y 60 días que A-M y A-S (6.2 ± 0.08 kg, 5.3 ± 0.10 kg y 5.5 ± 0.09 kg; 16.2 ± 0.22 kg, 14.8 ± 0.27 kg y 13.8 ± 0.25kg; 22.2 ± 0.33kg, 21.3 ± 0.39 kg y 20.8 ± 0.36 kg, respectivamente) (P 0.05). Las correlaciones entre pesos fueron positivas y sólo en S-A fueron negativas entre peso y condición de la madre (P 0.05).

Se evaluó el uso de tratamientos hormonales (GnRH y PGF2 #945;) y antibióticos (oxitetraciclina) en vacas lecheras Holstein Friesian con infección uterina en el posparto temprano (16.2 ± 3.8 días). Tratamientos: 1) testigo positivo (infectadas, no tratadas; n=30); 2) hormona liberadora de gonadotropinas (GnRH; n=29); 3) Prostaglandina F2 #945; (Pg; n=25); 4) oxitetraciclina (Ab; n=38); 5) GnRH+Pg (n=25); 6) GnRH+Ab (n=33); 7) Ab+Pg (n=25); 8) GnRH+Ab+Pg (n=29) y 9) testigo negativo (no infectadas no tratadas; n=425). Se evaluó: intervalo del parto a primer celo (IPPC), a primer servicio (IPPS), y a concepción (IPC); número de servicios por concepción (NS) y porcentaje de gestantes (GES). El análisis fue como bloques (hato) al azar y con un arreglo factorial 2 x 2 x 2 (sólo vacas infectadas) y, como covariables la condición corporal al tratamiento (CC15) y la producción láctea (P305d). Se midió la correlación simple entre las variables. Los resultados fueron similares en ambos testigos y no hubo efecto benéfico con ningún tratamiento. GnRH mostró efectos desfavorables en todas las variables, con excepción de GES (P0.05). No hubo efecto de Pg, Ab, ni sus interacciones (P0.05). Hubo correlación entre IPPC, IPPS e IPC; y de IPC con NS. Es cuestionable la precisión del diagnóstico por simple observación del moco cervical. El uso preestablecido e indiscriminado de los tratamientos evaluados sólo incrementa los costos y puede ser detrimental para algunos animales.

Se realizaron dos experimentos para evaluar el efecto de dos esquemas de aplicación de gonadotropinas en cerdas primíparas sometidas a lactancias de diez días sobre: Intervalo destete-estro (IDE); porcentaje de estros durante la primera semana posdestete (PE); porcentaje de fertilidad al estro inducido (PF); porcentaje de gestación respecto del total de animales expuestos (PG); tamaño de camada expresado como el número de lechones nacidos vivos (LNV) y totales (LNT) y números de folículos por categoría de tamaño (FP, folículos pequeños; FM, folículos medianos; FG, folículos grandes); cuerpos hemorrágicos (CH); cuerpos lúteos (CL); y total de ovulaciones (TO) al día siete postservicio. En ambos experimentos los tratamientos fueron: Testigo (SS, solución salina), aplicación simultánea de gonadotropinas (GNS, 1 200 UI eCG + 500 UI hCG 24 h posdestete) y aplicación diferida de gonadotropinas (GND, 1 200 UI eCG 24 h posdestete + 500 UI hCG 96 h posdestete). Se detectaron estros cuatro veces al día y las cerdas recibieron servicios por inseminación artificial al menos en dos ocasiones. En el primer experimento se diagnosticó preñez el día 35 postservicio. En el segundo experimento las cerdas fueron sacrificadas el día siete postservicio para conteo de estructuras ováricas y diagnóstico de gestación. El PE fue mayor en GNS y GND que en SS (94.7, 90.0 y 65.0; 100.0, 100.0 y 71.4, experimentos 1 y 2) y el PF menor en GNS que en GND y SS (50.0, 88.9 y 84.6; 12.5, 100.0 y 100.0, experimentos 1 y 2). El PG tendió a ser mayor en GND que en SS y fue menor en GNS que en los otros grupos (80.0, 55.0 y 47.4; 100.0, 71.4 y 12.5, experimentos 1 y 2). El IDE fue más corto en GNS y GND que en SS (5.0, 4.7 y 7.7; 5.3, 5.2 y 7.4, experimentos 1 y 2) y el número de CH mayor en GND que en GNS y SS (9.0, 1.8 y 0.2). El TO fue mayor y el número de FM menor en GNS y GND que en SS (27.7, 35.8 y 15.3 para TO; 0, 0.9 y 4.6 para FM). El número y tamaño de FG fue mayor en GNS que en GND y SS (10.8, 2.8 y 0.9 folículos y 20.5, 8.7 y 7.5 mm). El número de LNV, LNT, FP y CL no difirió entre tratamientos. En conclusión, ambos esquemas de aplicación de gonadotropinas permiten inducir y sincronizar el estro posdestete asociado con un aumento en el número de ovulaciones en cerdas primíparas sometidas a lactancias cortas, sin influir en el tamaño de la camada. Sin embargo, solamente el esquema de aplicación diferida induce estros de fertilidad normal, por lo que representa una alternativa para facilitar el uso del destete precoz.

Se evaluó el efecto de la inyección im de 3 mg de norgestomet (NG) en la inducción de atresia del folículo dominante persistente (FDP) y la formación del cuerpo lúteo (Cl) que se desarrolla después de inducir la ovulación del FDP con hCG, en vacas sincronizadas con implantes de norgestomet. Se utilizaron 11 vaquillas y 20 vacas Holstein previamente sincronizados con doble inyección de PGF2a. El día 7 del ciclo (día 0 del experimento), se les insertóunimplante sc de 3mgde norgestomet (iNG) y recibieronPGF2a; posteriormente se asignaron al azar a los siguientes tratamientos: Para el tratamiento hCG (n = 8) el día tres se aplicaron 2 500 UI de hCG im; para el tratamiento hCG + NG (n = 8) el día tres se aplicaron 2 500 UI de hCG im y el día cinco recibieron 3 mg de norgestomet im; para el tratamiento NG (n = 8) el día cinco recibieron 3 mg im de norgestomet. Al grupo testigo (n = 7) se le aplicó solución salina im el día tres y el día cinco, 5 ml de aceite vegetal. El iNG se retiró nueve días después de su inserción. Diariamente, a partir de la inserción del iNG y hasta la presentación del estro, se realizaron ultrasonografías de los ovarios y se tomaron muestras sanguíneas, en las cuales se determinaron las concentraciones de progesterona. La proporción de animales en los cuales se eliminó el FDP y se promovió un recambio folicular fue similar (0.05 P 0.1) entre los tratamientos hCG (5/8), hCG ( NG (7/8) y NG (6/7), pero fue diferente (P 0.05) al grupo testigo, en el cual nose eliminó ningúnFDP(0/7). El porcentaje de concepción fue similar (P0.05) entre las vacas que ovularon un folículo nuevo (66.6%; 12/18) y aquellas que ovularon el FDP (53.8%; 7/13). En el grupo hCG (NG el tratamiento con norgestomet después de la inyección de hCG evitó el desarrollo del Cl, ya que sólo una vaca de seis que ovularon tuvo niveles 1 ng/ml de progesterona al retirar el iNG, mientras que en el grupo hCG los cinco animales que ovularon tuvieron niveles 1ng/ml de progesterona (P 0.05). Se concluye que la inyección de 3 mg de norgestomet el día cinco posterior a la inserción del iNG provocó la atresia del FDP y evitó el desarrollo del cuerpo lúteo inducido con hCG.

The relative abundance of the different isoforms of pituitary and circulating luteinising hormone (LH) in ewes, at different times after the administration of gonadotrophin-releasing hormone (GnRH), during the luteal phase of the oestrous cycle was investigated. Sixteen ewes on Day 9 of their cycle were divided into four groups (n = 4). The control group (T0) received saline solution; the remaining animals received 100 microg GnRH (i.m.) 30, 90 or 180 min (T30, T90 and T180, respectively) before serum and pituitary gland collection. Luteinising hormone polymorphism was analysed by chromatofocusing (pH 10.5-3.5). The LH eluted from each chromatofocusing was grouped on the basis of the following three criteria: (1) according to the pH of elution (pHor = 10-3.5); (2) as either a basic (pHor = 7.5), neutral (pH 7.4-6.5) and acidic (pHor = 6.4) elution of LH of serum and hypophyseal origin; and (3) on the basis of distinct isoforms, of which 10 (A-J) were identifiable in hypophyseal extracts and four (A-D) were found in the serum. In general, the most abundant forms of LH in both the pituitary and serum, at all times, were basic. However, that proportion was greater in hypophyseal extracts (84 +/- 3%, 81 +/- 4%, 82 +/- 3% and 83 +/- 2% at T0, T30, T90 and T180, respectively) than in serum (51 +/- 5%, 48 +/- 10% and 54 +/- 6% at T30, T90 and T180, respectively). Neutral and acidic LH made up a larger proportion of the total LH in sera (neutral: 17 +/- 4%, 20 +/- 6% and 23 +/- 3% at T30, T90 and T180, respectively; acidic: 32 +/- 8%, 32 +/- 11% and 23 +/- 6% at T30, T90 and T180, respectively) than in the pituitary extracts (neutral: 4.0 +/- 0.7%, 10 +/- 4%, 7 +/- 2% and 5.0 +/- 0.5% at T0, T30, T90 and T180, respectively; acidic: 12 +/- 3%, 11 +/- 2%, 12 +/- 2% and 12 +/- 2% at T0, T30, T90 and T180, respectively) at all times. These data reveal that the relative composition of the LH present in the pituitary gland and the LH secreted into the circulation is different, with more neutral and acidic isoforms being secreted. The pattern of circulating LH isoforms changes between 30 and 180 min after GnRH peak induction, with a greater proportion of isoform C (eluting between pH 7.0 and 6.5) at T180 compared with T30 and T90.

Progesterone concentration in jugular blood of bred beef heifers was determined on days 9 and 16 in two trials. Human chorionic gonadotrophin (HCG) was administered to some of the heifers in each trial in an attempt to improve pregnancy percentage. In Trial 1, 183 heifers were divided into a control group and three groups of animals which were subjected to a 9-day estrous synchronization treatment prior to breeding. The treatment consisted of an ear implant containing 17 α acetoxy-11-beta-methyl 17 nor preg 4-ene 3, 20 dione (norgestomet) left in place for 9 days and an injection of 5 mg estradiol valerate (EV) and 3 mg of norgestomet given at the time of implantation. The heifers in one group received .25 mg estradiol-17β at time of implant removal; heifers in the 2nd group received 1500 IU of HCG in 5% beeswax and 95% sesame oil at breeding time, while heifers in the 3rd group received a placebo injection containing 5% beeswax and 95% sesame oil at breeding time. No differences in serum levels of progesterone were observed (P>0.5) between treatments or between pregnant and non-pregnant heifers on day 9 or 16 (P>.05). Pregnancy percentage in heifers receiving HCG was similar to that noted in the control heifers or the placebo injected heifers while injection of estradiol 17β decreased the proportion of heifers which became pregnant. In trial 2, 58 heifers which had been bred 1 or 2 times without becoming pregnant were divided into a control group and a group in which heifers received 1000 IU of HCG 96 hr. after observed estrus. In heifers receiving HCG, serum levels of progesterone were higher (P .05) between pregnant and non-pregnant heifers on day 9 or 16. The proportion pregnant did not differ (P>.05) between heifers receiving HCG and control heifers.

Colorado State University, s Fort Collins 80521 Summary By utilizing estrogen and progesterone, it appeared possible to mimic the changes occurring in blood hormone levels near puberty. This suggested the possibility of induction of puberty in beef heifers. Four trials were conducted to test this hypothesis and a fifth to explore the effect of treatment with steroids in induction of estrus in suckling anestrous cows.

"El objetivo fue evaluar la respuesta de LH, FSH y GH a kisspeptina - 10 (KISS) en becerras prepúberes de distintas edades, y su asociación con IGF - I, E2 y leptina circulantes. A 21 becerras de 4, 7 y 11 meses de edad se les aplicó una inyección i.v. de 5 μg de KISS/kg de peso. En suero obtenido de la yugular (cada 15 min, 4 h pre hasta 4 h post - KISS) se cuantificó LH, FSH y GH. En nueve muestras (tres pre y seis post - KISS) se determinó IGF - I, leptina y estradiol (E2) . En todas las becerras aumentó la LH post - KISS, con un valor máximo (6.1±1.3 a , 7.2±1.3 a , 11.6+1.3 b ng/ml) y duración de respuesta (64.3±20 a , 92±20 b , 132.9+20 c min) que aumentó ( P