RESUMO: O estudo teve como objetivo avaliar o efeito do sexo e do peso ao abate sobre as características de carcaça e componentes não-carcaça de 1.489 cavalos (739 machos castrados e 750 fêmeas, classificados em oito grupos de acordo com o peso). Os dados foram analisados em um desenho inteiramente casualizado. Os semeadores apresentaram maior rendimento de carcaça quente (HCY) e fria (CCY) do que as fêmeas, porém o amarelecimento da gordura (b*) foi maior nas fêmeas. O peso ao abate (SW) afetou as características de carcaça. HCW, CCW, HCY e CCY aumentaram de acordo com o peso de abate, enquanto CL% foi menor em equinos com peso superior a 300 kg. Além disso, os componentes não-carcaça diminuíram com o aumento do peso dos cavalos. Em conclusão, sexo e peso corporal são fatores a serem considerados na produção de carne equina, uma vez que afetam as características da carcaça e seus componentes.

ABSTRACT: The study evaluated the effect of sex and slaughter weight on carcass traits and non-carcass components of 1,489 horses (739 geldings and 750 females, classified into eight groups according to their weight). Data were analyzed under a completely randomized design. Geldings had a higher (P < 0.05) hot carcass yield (HCY) and cold carcass yield (CCY) than females; however, fat yellowness values (b*) were greater (P < 0.05) in females. Slaughter weight (SW) affected the carcass characteristics. Hot carcass weight (HCW), cold carcass weight (CCW), HCY, and CCY increased (P < 0.05) in accordance with slaughter weight, while cool loss percentage (CL%) was lower (P < 0.05) in horses weighing more than 300 kg. In addition, the non-carcass components decreased (P < 0.05) as the weight of the horses increased. In conclusion, sex and body weight are factors to consider in the production of equine meat since they affect carcass characteristics and non-carcass components.

ABSTRACT The objective of this study was to evaluate the effect of milking hygiene practices, herd size, water hardness, and temperature-humidity index (THI) on the physicochemical and microbiological characteristics of raw milk, and standard plate count (SPC) in milking machines of dairy farms in the central region of Mexico. Data were collected from fifty-three dairy farms during one year. The evaluated effects included milking hygiene conditions (good, medium, poor), herd size (1-50, 51-100, 101-150, ≥151 heads), water hardness (soft or moderately hard), and THI (comfortable or stressful). The increase in milking hygiene produced greater milk yield (MY) and energy corrected milk (ECM) but lower protein content, and decreased the individual bacterial count (IBC) and somatic cell count (SCC). The MY, ECM, protein content, IBC, and SCC were higher on bigger farms. The use of soft water reduced MY, IBC, and SCC, but improved fat, lactose, total solids (TS), and non-fat solids (NFS). Heat stress negatively affected fat, protein, TS, NFS, acidity, freezing point (FP), SCC, and methylene blue dye reduction test. Poor milking hygiene contributes to higher SPC in milking machine parts. Water hardness and THI did not affect SPC in all milking machine parts. Proper milking hygiene practices, larger herd size, softer water, lower THI, and adequate cleaning and disinfection of the milking machine parts benefits the physicochemical and microbiological quality of the milk.

Abstract Calcium (Ca) levels decrease in blood and cytosol at the time of calving, altering nerve impulse transmission, muscle contraction, and immune cell activity. In the nervous system, Ca participates in the conduction of stimuli. In the muscular system, it decreases contractions, causing alterations in smooth muscle, uterus and mammary gland. In the uterus, there is retention and storage of uterine fluids and waste, with bacterial complications. In the immune system, the function of neutrophils is important, and it manifests itself with a decrease in cells engaged in phagocytosis, predisposing to mastitis and metritis. In bovine hypocalcemia, two manifestations are distinguished: clinical and subclinical. In the clinical one (Ca values less than 5.5 mg/dl), homeostasis alters, with loss of appetite, decubitus and lethargy. Subclinical hypocalcemia is more common (Ca between 8.0 and 5.5 mg/dl), and homeostasis does not alter, but muscle contraction and immune function decrease. The treatment is based on the application of calcium orally in standing cows, and intravenously in prostrate cows. Prevention depends on the inclusion of rations that contain anionic salts, which favors the stimulus to maintain blood Ca levels to control the level of cations and anions. In addition, Ca can be administered orally. Calcium homeostasis in lactation is regulated by the serotonin hormone, which stimulates the parathyroid hormone and bone resorption in osteoclasts.

Resumen Los niveles de calcio (Ca) disminuyen en sangre y citosol al momento del parto, alterando la transmisión del impulso nervioso, la contracción muscular y la actividad de las células inmunes. En el sistema nervioso el Ca participa en la conducción de estímulos. En el sistema muscular disminuye la contracción causando alteraciones en músculo liso, útero y glándula mamaria. En el útero hay retención y almacenamiento de fluidos y desechos uterinos, con complicaciones bacterianas. En el sistema inmune, es importante la función de los neutrófilos y se manifiesta con una disminución de células dedicadas a la fagocitosis predisponiendo a mastitis y metritis. En la hipocalcemia bovina se distinguen dos presentaciones: clínica y subclínica. En la clínica (valores de Ca inferiores a 5.5 mg/dl) se altera la homeostasis con pérdida de apetito, decúbito y letargo. La hipocalcemia subclínica es más común (Ca entre 8.0 y 5.5 mg/dl), y no se altera la homeostasis, pero si se reduce la contracción muscular y la función inmune. El tratamiento se basa en la aplicación de calcio vía oral en vacas de pie, y vía endovenosa en las vacas postradas. La prevención depende de la inclusión de raciones que contengan sales aniónicas con lo cual se favorece el estímulo de mantener los niveles de Ca sanguíneos para controlar el nivel de cationes y aniones. Además, se puede administrar Ca vía oral. La homeostasis de calcio en la lactancia es regulada por la hormona serotonina, que estimula a la hormona paratiroidea y la reabsorción ósea en los osteoclastos.

Resumo Este estudo foi realizado no âmbito da Unidade Académica de Medicina Veterinária e Zootécnica da Universidade Autónoma de Zacatecas, onde foi lançado o Programa de Tutoria Institucional do Centro Académico de Serviços Escolares (CASE), cuja função é orientar e acompanhar novos alunos. Os mentores da unidade em questão aconselham os novos alunos academicamente. Por isso, para a realização deste trabalho, é necessário que os alunos mentores identifiquem os seus direitos e deveres. Ao conhecer os benefícios e responsabilidades do mentor, espera-se que os alunos se sintam ainda mais motivados para desempenhar este nobre papel, bem como, quantitativamente, obtenham maior participação e melhor desempenho acadêmico. O estudo tem abordagem metodológica qualitativa, e baseia-se no método bibliográfico, analítico, sintético e descritivo. No âmbito das conclusões, considera-se necessário que o aluno orientador conheça os seus direitos e deveres para que o processo de acompanhamento seja realizado de forma eficaz e que os alunos orientados melhorem o seu rendimento escolar, a sua adaptação social e o desenvolvimento de competências.

Abstract This study was carried out in the context of the Unidad Académica de Medicina Veterinaria y Zootecnia of the Universidad Autónoma de Zacatecas, where the Institutional Mentoring Program of the Academic Center for School Services (CASE, by its acronym in Spanish) has been launched, whose function is orient and mentor new students. The mentors of the unit in question give academic advice to new students. This is why, in order to carry out this work, it is necessary for the student mentors to identify their rights and obligations. At the same time, by knowing the benefits and responsibilities of the mentor, it is expected that students feel even more motivated to exercise this noble role, as well as, quantitatively, obtain greater participation and better academic performance. The study has a qualitative methodological approach, and relies on the bibliographic, analytical, synthetic and descriptive method. As part of the conclusions, it is considered necessary for the mentor student to know their rights and obligations so that the mentoring process is carried out effectively and that the mentor students improve their academic performance, their social adaptation and development of skills.

Resumen El presente estudio se llevó a cabo en el contexto de la Unidad Académica de Medicina Veterinaria y Zootecnia de la Universidad Autónoma de Zacatecas, donde se ha puesto en marcha el Programa Institucional de Mentorías del Centro Académico de Servicios Escolares (CASE), cuya función es orientar y dar acompañamiento a estudiantes de nuevo ingreso. Los mentores de la unidad en cuestión asesoran académicamente a los estudiantes de nuevo ingreso. Es por ello por lo que, para llevar esta labor, es necesario que los estudiantes mentores identifiquen sus derechos y obligaciones. Al conocer los beneficios y las responsabilidades del mentor, se espera que los alumnos se sientan aún más motivados para ejercer esta noble función, así como, cuantitativamente, obtener una mayor participación y un mejor rendimiento académico. El estudio tiene un enfoque metodológico cualitativo, y se apoya del método bibliográfico, analítico, sintético y descriptivo. Como parte de las conclusiones, se considera necesario que el estudiante mentor conozca sus derechos y obligaciones para que el proceso de acompañamiento se lleve a cabo eficazmente y que los estudiantes mentorados mejoren su rendimiento académico, su adaptación social y desarrollo de competencias.

Abstract Three reproductive protocols were evaluated: 1) PG: injection of PGF2α on d-50 postpartum and insemination (AI) based on estrus detection. 2) OVS (Ovsynch: d 0, GnRH; d 7, PGF2α; d 9, GnRH; d 10, AI); 3) ROV (GnRH + Ovsynch: d- 7, GnRH; d 0, GnRH; d 7 PGF2α; d 9, GnRB; d 10, AI). In addition, the effect of somatotropin (bST) to AI, on fertility at first postpartum service (FERT), and pregnancy rate at 99 d postpartum (PP) FERT was similar in ROV and OVS (36.2 vs 36.6 %) (P>0.05); and higher than PG (27.3 %) (P<0.05). Likewise, FERT was similar with and without bST (36.2 vs 30.6 %, P>0.05). PG and without bST (22.5 %) was lower than OVS with (38.5 %) and without bST (33.7 %), as well as than ROV with (37.0 %) and without bST (36.1 %), and PG with bST (32.9 %). The pregnancy rate at 99 d was: OVS (60.6 %); ROV (54.3 %), higher than PG group (46.8 %) (P>0.05). OVS with (64.7 %) and without bST (56.5 %) and ROV without bST were higher than PG without bST (41.1 %, P<0.05). In conclusion, GnRH before Ovsynch (ROV) and bST at AI did not increase fertility at the first service in Holstein cows under heat stress. OVS and ROV increased fertility of first service postpartum and pregnancy rate to 99 d postpartum. Somatotropin increased fertility of first postpartum service only in PG treated cows.

Resumen: Tres protocolos reproductivos fueron evaluados: 1) PG: inyección de PGF2α en el día 50 posparto e inseminación (IA) en base a detección del estro. 2) OVS (Ovsynch: día 0, GnRH; día 7, PGF2α; día 9, GnRH; día 10, IA); y 3) ROV (GnRH + Ovsynch: día- 7, GnRH; día 0, GnRH; día 7, PGF2α; día 9, GnRH; día 10, IA). Además, el efecto de la somatotropina (bST) a la IA, sobre la fertilidad al primer servicio posparto (FERT), y la tasa de preñez a 99 días posparto (PP). FERT fue similar en ROV y OVS (36.2 vs 36.6 %) (P>0.05); y mayor a PG (27.3 %) (P<0.05). Igualmente, FERT fue similar con bST y sin bST (36.2 vs 30.6 %, P>0.05). PG y sin bST (22.5 %) fue menor que OVS con (38.5 %), y sin bST (33.7 %); y que ROV con bST (37.0 %) y sin bST (36.1 %); y PG con bST (32.9 %) (P<0.05). La tasa de preñez a 99 días PP fue: OVS (60.6 %); ROV (54.3 %), superior al grupo PG (46.8 %) (P<0.05). OVS con bST (64.7 %), y sin bST (56.5 %), y ROV sin bST fueron mayores que PG sin bST (41.1 %, P<0.05). En conclusión, GnRH previo al Ovsynch (ROV) y la bST al momento de la IA no incrementaron la fertilidad del primer servicio en vacas Holstein en estrés calórico. OVS y ROV incrementaron la fertilidad del primer servicio posparto y la tasa de preñez a 99 días posparto. La somatotropina incrementó la fertilidad del primer servicio posparto solo en vacas tratadas con PG.

Abstract: The aim of this study was to determine the number of adult bees, brood areas, honey and pollen from 150 honey bee (Apis mellifera) colonies in spring and fall in the temperate semidry, temperate sub-humid and semi-warm semi-dry regions of Zacatecas, Mexico. The colonies in the semi-warm semi-dry region had significantly more bees and brood in the fall than those in the other regions (P=0.001). In the spring, colony populations in the temperate semi-dry and semi-warm semi-dry regions were similar and significantly greater than those in the temperate sub-humid region (P<0.01). There was significantly less honey and more pollen stored in the fall, in hives of the semi-warm semi-dry region than in hives of the other regions (P=0.001). In the spring, the area of stored pollen in colonies of the temperate semidry region was significantly greater than that of colonies from the other regions (P<0.0001). The population of adult bees and brood areas of colonies in the fall correlated positively with bee population, brood and honey areas in the spring (P<0.001). In the fall, the semi-warm semi-dry region had better conditions for developing and reproducing colonies than the other regions. However, the population sizes of the colonies studied (21,000 to 35,000 bees/hive) are not considered optimal (>50,000), and thus, it is suggested that previous to blossom seasons, strategies aimed at increasing bee population and food stores, that contribute to winter colony survival and to improve their productivity, are implemented.

Resumen: Se estimó la población de abejas, áreas con cría, miel y polen en 150 colonias de abejas melíferas (Apis mellifera) establecidas en las regiones semiseca templada, subhúmeda templada y semiseca semicálida de Zacatecas, México, durante las épocas de primavera y otoño. Las colonias de la región semiseca semicálida tuvieron significativamente más abejas y cría en otoño que las colonias de las otras regiones (P(0.001). En primavera, la población de abejas en las colonias de las regiones semiseca templada y semiseca semicálida fue similar, y significativamente mayor que en la región subhúmeda templada (P(0.01). Se registró menos miel y más polen almacenados en otoño en colonias de la región semiseca semicálida que en las otras regiones (P(0.001). En primavera, el área de polen almacenado en colonias de la región semiseca templada fue significativamente mayor que en las otras regiones (P<0.0001). La población de abejas y áreas de cría de las colonias en otoño, se correlacionaron positivamente con la población de abejas, áreas de cría y miel de la primavera (P<0.001). En otoño, la región semiseca semicálida tuvo mejores condiciones para el desarrollo y reproducción de colonias que las otras regiones. Sin embargo, el tamaño poblacional de las colonias estudiadas (21,000 a 35,000 abejas/colmena) no es considerado óptimo ((50,000), por lo que se sugiere que previo a floraciones se implementen estrategias tendientes a incrementar la población y reservas de alimento que contribuyan a la sobrevivencia de las colonias en el invierno y a mejorar su productividad.

RESUMO: O objetivo deste estudo foi avaliar o efeito do gênero e peso vivo (PV) nas características da carcaça, componentes não-carcaça e cor da carne e gordura dos burros (Equus africanus asinus). Foram utilizados 189 animais de sexo castrado ou feminino. Os castrados tiveram peso de carcaça maior (P <0,05), molho de carcaça e uma gordura subcutânea luminosa (valor L) nas fêmeas. As fêmeas apresentaram perda de resfriamento maior (P <0,05), *valor de cor do músculo semitendinoso e b* valor de cor da gordura subcutânea. A gordura subcutânea apresentou maior (P <0,05) b* em animais idosos. Os burros com mais de 126kg de PV apresentaram maior peso de carcaça (P <0,05), curativo de carcaça e menor (P <0,05) perda de resfriamento em comparação com burros mais leves. O músculo semitendinoso e a gordura abdominal foram avermelhadas (P <0,05), maior valor de *, em burros mais pesados (>151kg). Enquanto isso, o PV não afetou a cor (valores de L *, a * e b *) de gordura subcutânea (P> 0,05). O peso maior da carcaça e o curativo com efeitos limitados em componentes não carcaça, cor de carne e gordura foram observados em castrados com peso vivo superior a 126kg.

ABSTRACT: One hundred eighty-nine Catalan crossbreed donkeys (Equus africanus asinus) were used to evaluate the effect of gender (gelding, n=106; or female, n=83) and live weight at slaughter (LW) (<100kg, n=25; 101 to 125kg, n=42; 126 to 150kg, n=85; and 151>kg, n=37) on carcass characteristics, non-carcass components and meat and fat color. Geldings had greater (P<0.05) carcass weight, carcass dressing and *L value of subcutaneous fat than females; but females had greater (P<0.05) cooling loss, a* value of semitendinosus muscle and b* value of subcutaneous fat. Donkeys with more than 126kg of LW showed greater (P<0.05) carcass weight and dressing and lower (P<0.05) cooling loss compared to lighter donkeys. The a* value of semitendinosus muscle and abdominal fat was greater in heaviest donkeys (>151kg). Meanwhile, the LW did not affect the color (L*, a* and b* values) of subcutaneous fat (P>0.05). These results suggested that both gender and live weight should be considered when producing meat from donkeys. It is advisable to use geldings weighing more than 126kg at slaughter to obtain the greatest weight and carcass yield.

The purpose of this work was to estimate the prevalence of the Translocation 1;29 (t rob 1;29) in cattle herds in the Mexican state of Zacatecas. Blood samples were obtained from 661 bovines of eight breeds: Holstein (n= 284), American Swiss (n= 213), Braunvieh (n= 69), Simmental (n= 13), Angus (n= 5), Creole (n= 65), Chianina (n= 3) and Charolais (n= 9). Sampling was conducted in nine municipalities of the state of Zacatecas and one in the state of Aguascalientes. Age, sex and productive purpose were also recorded. Identification of the t rob 1;29 was performed by conventional cytogenetic technique. An overall prevalence of 4.1 %, with no differences between males and females (6.0 vs 3.4 % respectively), although greater (P<0.10) in young animals vs adults (5.4 vs 2.6 % respectively) was observed. Breed differences (P<0.001) were observed with a greater prevalence in the Criollo breed (12.3 %), followed by Swiss American breed (7.5 %) and lower among Braunvieh (1.4 %), Holstein (0.4 %) and others breeds (0.0 %). According to productive purpose a greater prevalence (P<0.001) was observed in dual purpose farms (12.3 %) than dedicated exclusively to the milk (3.3 %) or beef (2.4 %) production. Based on these results and because of the potential negative effects on herd productivity, a chromosomal analysis of breeding animals is recommended as a routine practice, to identify animals carrying the t rob 1;29, mainly in sires.

El objetivo del trabajo fue determinar la prevalencia de la Translocación robertsoniana 1;29 (t rob 1;29) en hatos ganaderos del estado de Zacatecas, México. Se obtuvieron muestras sanguíneas de 661 bovinos de las razas Holstein (n= 284), Suizo Americano (n= 213), Suizo Europeo (n= 69), Simmental (n= 13), Angus (n= 5), Criollo (n= 65), Chianina (n= 3) y Charolais (n= 9). Los muestreos se realizaron en nueve municipios de Zacatecas y uno de Agusacalientes. Se registró además la edad, el sexo y el propósito productivo. La identificación de la t rob 1;29 se realizó mediante técnica convencional de citogenética. Se observó una prevalencia general del 4.1 %, sin diferencias (P>0.05) entre machos y hembras (6.0 vs 3.4 % respectivamente), aunque superior (P<0.10) en animales jóvenes vs adultos (5.4 vs 2.6 % respectivamente). Se observaron diferencias raciales (P<0.001), con una mayor prevalencia en la raza Criollo (12.3 %), seguida de la raza Suizo Americano (7.5 %) y menor entre las razas Suizo Europeo (1.4 %), Holstein (0.4 %) y otras (0.0 %). De acuerdo al propósito productivo se encontró una mayor prevalencia (P<0.001) en las explotaciones de doble propósito (12.3 %) que en los dedicadas exclusivamente a la producción de leche (3.3 %) o carne (2.4 %). Con base en estos resultados y debido a los potenciales efectos negativos sobre la productividad del hato, es recomendable el análisis cromosómico de los animales reproductores como práctica rutinaria de identificación de animales portadores de la t rob 1;29, principalmente en los sementales.

Influence of a sexually-active male buck was evaluated on the onset of reproductive function (hypothalamic and ovarian activity) and estrous cycles progression in Criollo goats from the northen Mexican desert, exposed to an alternated (decreasing/increasing) artificially controlled photoperiod fluctuating within 13.4 to 10.6 light hours per day until fulfilling 6 photoperiodic cycles of 90 d each cycle: ascending (n=3); and descending (n=3). Mexican-native Criollo goats (n=30) were randomly assigned into 2 treatment groups: 1) goats exposed to a sexually-active male buck (n=15); 2) goats not exposed to a male buck (absence of a male buck; n=15). Each experimental group of goats included ovariectomized goats (OVX, n=5), ovariectomized and estradiol-implanted goats (OVX + E2, n=5), and intact-ovaries goats (Control, n=5). Blood samples were taken from OVX and OVX + E2 goats, every four weeks, during 6 h at 15 min intervals (i.e., 24 samples/day), to determine frequency (FREQ), amplitude (AMP), and concentration (CONC) of luteinizing hormone (LH). For Control goats, blood samples were taken twice every week in order to quantify serum-progesterone levels through radioimmunoanalysis (RIA). Goats implanted with E2 (OVX + E2-goats) showed an increased LH pulse frequency compared to OVX-goats without an E2 implant (2.0 ± 0.5 vs. 0.7 ± 0.1 LH pulses/ 6 h). Presence of a sexually-active male buck increased frequency, amplitude and concentration of LH in OVX goats compared to goats not exposed to males (Frequency: 3.2 ± 0.4 vs. 0.7 ± 0.1 pulses/6 h; Amplitude: 1.6 ± 0.1 vs. 0.8 ± 0.3 ng·mL-1; Concentration: 5.3 ± 0.6 vs. 2.0 ± 0.9 ng·mL-1) (P<0.001). In Control goats (intact ovaries), male exposure increased luteal activity and estrous cycle progression refected as a greater number of days in luteal activity (44 ± 9.05 vs. 32.3 ± 20.6); a reduced number of days in anestrous (4.0 ± 4.8 vs. 51.9 ± 28) and a greater number of luteal phases (15.7 ± 4.4 vs. 11.3 ± 8.7) without compromising serum progesterone levels (6.8 ± 0.8 vs. 7.3 ± 0.5) (P>0.05). In conclusion, presence of a sexually-active male buck induced a greater ovarian activity in Criollo goats, shortening seasonal anestrous even during an ascendent controlled-photoperiod. Such strategy, using a sexually-active male buck might be helpful to increase ovarian activity and reproductive function during the seasonal anestrous of Criollo goats from dry and arid areas of northern Mexico and similar regions of the world.

Se evaluó la influencia de un macho cabrío sexualmente activo sobre el inicio de la actividad reproductiva (actividad hipotalámica y ovárica) y la sucesión de los ciclos estrales en cabras criollas expuestas a fotoperiodo artificiales alternados (decreciente/creciente) en un rango de 13.4 a 10.6 horas de luz por día hasta completar 6 ciclos foto-periódicos de 90 d por cada ciclo: fotoperiodo creciente (n=3); fotoperiodo decreciente (n=3). Las cabras criollas procedentes del semidesierto zacatecano (n=30) fueron asignadas de manera aleatoria a dos grupos: 1) cabras expuestas a un macho cabrío sexualmente activo (n=15); 2) cabras no expuestas al macho cabrío (ausencia de macho cabrío; n=15). Dentro de cada grupo experimental existían cabras ovariectomizadas (OVX, n=5), cabras ovariectomizadas e implantadas con estradiol (OVX + E2, n=5), y cabras ovariointactas (testigo, n=5). Se recolectaron muestras de suero sanguíneo de las cabras OVX y OVX + E2, cada cuatro semanas, durante 6 h en intervalos de 15 min (es decir, 24 muestras/día), para determinar la frecuencia (FREQ), la amplitud (AMP) y la concentración (CONC) de la hormona luteinizante (LH). En las cabras testigo (no tratadas), se obtuvieron 2 muestras de sangre a la semana para cuantificar los niveles de progesterona en suero sanguíneo mediante un radioinmunoanálisis (RIA). Las cabras con implantes de E2 (cabras OVX + E2) mostraron un incremento en la frecuencia de los pulsos de la hormona luteinizante en comparación con las cabras OVX sin implante de E2 (2.0±0.5 vs.0.7 ± 0.1 LH pulsos/6 h). La presencia de un macho sexualmente activo aumenta la frecuencia, la amplitud y la concentración de la hormona luteinizante en cabras OVX en comparación con cabras no expuestas a machos (Frecuencia: 3.2 ± 0.4 vs. 0.7 ± 0.1 pulsos/6 h; Amplitud: 1.6 ± 0.1 vs. 0.8 ± 0.3 ng·mL-1; Concentración 5.3 ± 0.6 vs. 2.0 ± 0.9 ng·mL-1) (P<0.001). En las cabras testigo (con los ovarios intactos), la presencia y estímulo del "efecto macho" indujo una mayor función reproductiva (actividad lútea) y un incremento considerable en la sucesión de los ciclos estrales, mostrando un mayor número de días en actividad lútea (44 ± 9.05 vs. 32.3 ± 20.6); menor número de días en anestro (4.0 ± 4.8 vs. 51.9 ± 28) y un mayor número de fases lúteas (15.7 ± 4.4 vs. 11.3 ± 8.7). Todo ello sin afectar los niveles séricos de la hormona progesterona (6.8 ± 0.8 vs. 7.3 ± 0.5) (P>0.05). En conclusión, la presencia de un macho cabrío sexualmente activo estimuló una mayor actividad ovárica de las cabras, disminuyendo la duración del anestro estacional, incluso bajo condiciones de fotoperiodo artificial-controlado ascendente. Esta estrategia pudiera permitir incrementar la función reproductiva y de esa manera reducir la temporada de anestro o inactividad reproductiva de las cabras criollas del norte de México.