Abstract The high temperatures recorded during the summer season in hot regions compromise the reproductive capacity of domestic animals. In rams, heat stress (HS) causes in the body a series of physiological, metabolic, endocrine and molecular adjustments in order to maintain normothermia and survive; however, several of these changes are negatively associated with their fertility, mainly endocrine ones. HS in rams causes a decrease in blood testosterone concentrations through different mechanisms, and this is negatively reflected on the process of spermatogenesis and sexual behavior. Consequently, heat-stressed rams exhibit low seminal quality and libido; at the sperm level, structural and DNA damage has been observed. Given this situation, the use of HS mitigation strategies during the summer in sheep farms in hot regions is recommended, such as the use of shades in pens, administration of antioxidants or modifications in the diet. Therefore, the objective of this document is to review the current knowledge regarding the effect of HS on the thermoregulation and reproductive capacity of rams, as well as the application of strategies for its mitigation.

Resumen Las temperaturas elevadas registradas durante la época de verano en las regiones cálidas comprometen la capacidad reproductiva de los animales domésticos. En carneros, el estrés por calor (EC) causa en el organismo una serie de ajustes fisiológicos, metabólicos, endocrinos y moleculares con el objeto de mantener normotermia y sobrevivir; sin embargo, varios de estos cambios se asocian negativamente con su fertilidad, principalmente los endocrinos. El EC en carneros provoca una disminución en las concentraciones sanguíneas de testosterona a través de diferentes mecanismos, y esto se refleja negativamente en el proceso de espermatogénesis y en la conducta sexual. En consecuencia, los carneros estresados por calor presentan baja calidad seminal y apetito sexual; a nivel de espermatozoides se ha observado daño estructural y en el ADN. Dada esta situación, se recomienda el uso de estrategias de mitigación del EC durante el verano en las explotaciones ovinas de regiones cálidas, tales como el uso de sombras en corrales, la administración de antioxidantes o modificaciones en la alimentación. Por lo tanto, el objetivo de este documento es revisar el conocimiento actual en relación al efecto del EC sobre la capacidad de termorregulación y reproductiva de los carneros, así como la aplicación de estrategias para su mitigación.

Abstract The aim was to evaluate if 1-2 propanodiol plus calcium propionate (glycogenic precursor) supplementation during the transition period in high yielding dairy cows reduces metabolic and reproductive dysfunctions during early lactation. Cows (n= 202) were divided into two homogeneous groups regarding number of lactations and body condition score. 1) Treated group (GG; n= 112) received 60 g/cow/d for15 d of a glycogenic precursor during the transition period. 2) Control group (GC; n= 90) received no treatment. Postpartum levels of beta hydroxybutyrate (BHB) (GG= 0.9 ± 0.2 mmol/L vs GC =1.3 ± 0.2 mmol/L; P<0.05), and non-esterified fatty acids (NEFA) (GG= 0.6 ± 0.1 mEq/L vs GC = 0.8 ± 0.1 mEq/L; P<0.05) were higher in the GC-group. Similarly, GC-cows had a higher percentage of retained placenta (23 % vs 13 %; P≤0.06) subclinical ketosis (GG= 10 %, GC= 56 %; P<0.05), and mastitis (GG= 8 %, GC= 16 %; P<0.05). Metritis, dystocia, abortions, clinical ketosis, hypocalcemia and ruminal acidosis showed no differences between groups. Administration of a glycogenic precursor during the transition period demonstrated a positive effect upon BHB and NEFA blood levels during early lactation, with parallel decreases of subclinical ketosis and retained placenta; this could be an alternative to enhance the dairy herd reproductive efficiency.

Resumen El objetivo fue evaluar si la suplementación del 1-2 propanodiol más propionato de calcio (precursores glucogénicos) durante el periodo de transición en vacas altas productoras disminuye la incidencia de enfermedades metabólicas y reproductivas durante el inicio de la lactancia. Las vacas se dividieron en dos grupos homogéneos respecto al número de lactancias, y condición corporal. 1) Grupo tratado (GG; n= 112): por 15 días durante el periodo de transición se les administraron 60 g/vaca/día del precursor glucogénico, el cual fue adicionado en la dieta. 2) Grupo control (GC; n= 90): no se le administro ningún tratamiento. Los niveles de beta hidroxibutirato (BHB) (GG= 0.9 ± 0.2 mmol/L vs GC= 1.3 ± 0.2 mmol/L; P<0.05), y ácidos grasos no esterificados (AGNES) (GG= 0.6 ± 0.1 mEq/L vs GC= 0.8 ± 0.1 mEq/L; P<0.05) posparto fueron más altos en el GC que en el GG. Igualmente el GC (23 %) tuvo mayor porcentaje de hembras con retención de placenta que el GG (GG= 13 %; P≤0.06). Mientras que no existió diferencia en metritis, distocia y aborto entre grupos (P>0.05). Sin embargo, la cetosis subclínica (GG= 10 %, GC= 56 %; P<0.05), y la mastitis (GG= 8 %, GC= 16 %; P<0.05) fueron más altas en GC que en el GG. Mientras que, para cetosis clínica, hipocalcemia y acidosis ruminal no existió diferencia entre los grupos (P>0.05). La administración del precursor redujo los niveles de BHB y AGNES, así como el porcentaje de cetosis subclínica y retención de placenta, lo cual puede ser una alternativa para para mejorar la eficiencia reproductiva.

ABSTRACT: The objective of this study was to analyse the reproductive performance of hybrid (Yorkshire x Landrace) gilts/ sows in relation to temperature-humidity index (THI) at artificial insemination (AI), season of AI, occurrence of estrus >8 d post- weaning, repeated estrus, insemination technique (cervical, CAI or post-cervical, PCAI) and parity. Data included 8851 reproductive records (1771 for gilts and 7080 for sows) from a pig farm in a sub-tropical zone (THI ranged from 72.9 in January to 81.8 in June). A decrease in pregnancy rate (PR, 89.8 vs 93.0%; P<0.01) and a tendency to decline farrowing rate (FR, 87.9 vs 90.3%; P=0.07) following AI during high THI (>82), compared to AI at <74 THI were observed. The spring and summer season were associated with decreased (P<0.01) PR compared with fall and winter (90.0% vs 93.0%). Likewise, FR decreased in spring and summer compared to fall and winter (88.5% vs. 90.9%). FR was higher (P<0.01) in non-repeat breeders compared with that of repeat-breeders (90.3% vs 76.2%). Litter size increased (P<0.01) from 10.8 ± 3.2 to 11.1 ± 3.1 pigs when the interval from weaning to estrus was >8 d. The insemination technique did not affect PR and FR but the litter size decreased (P<0.05) from 11.3 ± 3.0 to 11.1 ± 2.9 pigs when PCAI was used compared to CAI. This study reaffirms the negative effects of the hot season on reproductive performance of gilts/sows, although thermal stress at AI did not cause foetal losses. Also, there is no advantage in using the PCAI as compared to the CAI in gilts/sows with high numbers of sperm cells per AI.

Abstract: A total of 48 Katahdin x Pelibuey multiparous ewes were used to evaluate the effect of nutritional restriction (40 %) before (30 d, RT), after (50 d, TR) or both periods (80 d, RR) compared with a control group on maternal body status, early fetal growth and lamb birth weights. Only twin bearing ewes were selected at d 50 of pregnancy for fetal measurements by ultrasonography and record of birth weight. Compared with control ewes, lower (p < 0.05) weight and body condition score had RT and RR ewes at mating time, likewise, TR and RR ewes at d 50 post-conception. There were mainly differences between fetuses from control and RT ewes, being higher (p < 0.05) the vesicular, abdominal and fetal area, as well as crown-rump length and birth weight for RT fetuses. In conclusión, preconception undernutrition positively altered the early fetal growth and lamb birth weights in hair ewes pregnant with twins.

Resumen: Se usaron 48 ovejas multíparas Katahdin x Pelibuey para evaluar el efecto del 40 % de restricción nutricional antes (30 d, RT), después (50 d, TR) o antes y después de la concepción (80 d, RR), comparado con un grupo testigo sobre el estado corporal materno, crecimiento fetal temprano y peso al nacimiento de las crías. Solo ovejas con preñez gemelar fueron seleccionadas al día 50 post-monta para mediciones fetales por ultrasonografía y registro de peso al nacimiento. Las ovejas RT y RR tuvieron menor (p < 0.05) peso y condición corporal al empadre, mientras que las ovejas TR y RR a los 50 días post-concepción tuvieron menor peso que las ovejas de los otros tratamientos. Se observaron diferencias entre fetos de ovejas testigo y RT, siendo mayor (p < 0.05) el área vesicular, abdominal y fetal, además de la longitud cráneo-caudal y los pesos al nacimiento en fetos de ovejas RT. La desnutrición pre-concepción alteró de forma positiva el crecimiento fetal temprano y el peso al nacimiento de las crías en ovejas de pelo con preñez gemelar.

Abstract This research shows the analysis of the effects of the simulation of the increase of $1 per liter to the price of sodas. The simulation was performed in a characteristic rural community of Mexico. The general computable rural equilibrium model was used under two scenarios: In perfect competition and in absence of markets. The main effect under the two scenarios was a drop of 14.29% in consumption; without consequences on the agricultural, livestock and factor markets. This drink behaved as an inelastic good in the magnitude of -0.85. The soda tax discouraged consumption; however, an effective reduction would require combined strategies.

Resumen En esta investigación se muestra el análisis de los efectos de la simulación del incremento en $1 por litro al precio de los refrescos. La simulación se realizó en una comunidad rural característica de México. Se utilizó el modelo de equilibrio general computable rural bajo dos escenarios: En competencia perfecta y con ausencia de mercados. El efecto principal bajo los dos escenarios fue una caída de 14.29% en el consumo; sin consecuencias en el mercado agrícola, ganadero y de factores. Esta bebida se comportó como un bien inelástico en la magnitud de -0.85. El impuesto a los refrescos desincentivó el consumo; no obstante, para una reducción efectiva se requieren estrategias combinadas.

Taxonomic classification problems are frequent in the case of nopal (Opuntia spp.), as well as for many other genera; this complicates the accurate identification of cultivars. This study was done with the objective of detecting polymorphism in nine nopal cultivars of the 0. amyclaea Ten. (0. albicarpa), 0. megacantha, 0. crassa and 0. ficus-indica (L.) Mill, species located in the germplasm reserve of the Unidad Regional Universitaria de Zonas Aridas of the Universidad Autonoma Chapingo. The soluble protein of the roots was separated through electrophoresis to evaluate the presence of nine enzyme systems. Among these, phosphoglucomutase (PGM), 6- phosphogluconate dehydrogenase (6-PGD), glutamate oxaloacetate transaminase (GOT) and malate dehydrogenase (MDH) showed a sufficient reaction for the identification of bands of enzymatic activity. The malic enzymes (ME) and aconitase (ACO) did not present polymorphism; they are therefore not recommended for the classification of nopal cultivars. In contrast, PGM, 6-PGD, GOT and MDH presented differences or undetermined polymorphism in their band pattern; they are therefore considered relevant for the taxonomic identification and evaluation of the genetic variability of nopal.

En nopal (Opuntia spp.) como en muchos géneros, los problemas de clasificación taxonómica son frecuentes, esto complica la identificación correcta de cultivares. Este estudio se realizó con la finalidad de detectar polimorfismo en nueve cultivares de nopal de las especies O. amyclaea Ten. (O. albicarpa), O. megacantha, O. crassa y O. ficus-indica (L.) Mili., ubicados en la reserva de germoplasma de la Unidad Regional Universitaria de Zonas Áridas de la Universidad Autónoma Chapingo. La proteína soluble de las raíces se separó por electroforesis para evaluar la presencia de nueve sistemas enzimáticos. De estos, fosfoglucomutasa (PGM), 6-fosfogluconato deshidrogenasa (6-PGD), glutamato oxaloacetato transaminasa (GOT) y malato deshidrogenasa (MDH) expresaron reacción suficiente para una identificación de bandas de actividad enzimática. Las enzimas málicas (ME) y aconitasa (ACO) no presentaron polimorfismo, por tanto no se recomiendan para la clasificación de cultivares de nopal. En contraste, PGM, 6-PGD, GOT y MDH presentaron diferencias o polimorfismo indeterminado en su patrón de bandeo, por lo que se consideran relevantes para la identificación taxonómica y evaluación de la variabilidad genética de nopal.

O objetivo deste trabalho foi obter estimativas de prevalência de muco vaginal turvo durante o estro em vacas Holandesas criadas sob intenso calor, para avaliar o efeito das condições climáticas sobre sua ocorrência durante o estro e determinar seu efeito sobre a taxa de concepção. Em um primeiro estudo, foi estabelecida a associação entre a ocorrência de muco vaginal turvo durante o estro e a taxa de concepção de vacas inseminadas (18.620 serviços), criadas sob intenso calor (temperatura média anual de 22°C), em fazendas altamente tecnificadas, na região árida do norte do México. Em um segundo estudo, os dados desses grandes estábulos leiteiros foram utilizados para avaliar o efeito das condições climáticas, ao longo do ano, na ocorrência de muco vaginal turvo durante a inseminação artificial (76.899 cios). A taxa global de cios com muco vaginal turvo foi de 21,4% (16.470/76.899; intervalo de confiança de 95% = 21,1-21,7%). A taxa de concepção das vacas com muco vaginal límpido foi maior que a de vacas com muco anormal (30,6 vs. 22%). A prevalência de estros com muco vaginal turvo foi fortemente dependente de elevada temperatura ambiente, e significativamente maior em maio e junho. Taxas de concepção aceitáveis de vacas Holandesas com elevada produção de leite somente são obtidas em vacas que apresentem muco translúcido durante a inseminação artificial.

The objective of this work was to obtain prevalence estimates of cloudy vaginal mucus in artificially inseminated Holstein cows raised under intense heat, in order to assess the effect of meteorological conditions on its occurrence during estrus and to determine its effect on conception rate. In a first study, an association was established between the occurrence of cloudy vaginal mucus during estrus and the conception rate of inseminated cows (18,620 services), raised under intense heat (mean annual temperature of 22°C), at highly technified farms, in the arid region of northern Mexico. In a second study, data from these large dairy operations were used to assess the effect of meteorological conditions throughout the year on the occurrence of cloudy vaginal mucus during artificial insemination (76,899 estruses). The overall rate of estruses with cloudy vaginal mucus was 21.4% (16,470/76,899; 95% confidence interval = 21.1-21.7%). The conception rate of cows with clean vaginal mucus was higher than that of cows with abnormal mucus (30.6 vs. 22%). Prevalence of estruses with cloudy vaginal mucus was strongly dependent on high ambient temperature and markedly higher in May and June. Acceptable conception rates in high milk-yielding Holstein cows can only be obtained with cows showing clear and translucid mucus at artificial insemination.

Antecedentes: la asociación entre temperaturas ambientales elevadas y alta humedad conduce a fallas reproductivas, disminuyendo la fertilidad de hatos lecheros. Objetivo: determinar el efecto de temperaturas ambientales elevadas sobre el comportamiento reproductivo de vacas Holstein mantenidas en un ambiente árido y cálido y tratadas con hormona del crecimiento (rbST) durante toda la lactancia. Métodos: las variables reproductivas (n=18037 servicios) de una explotación comercial fueron evaluadas con respecto al máximo índice temperatura humedad (THI) antes, durante y después de la inseminación de las vacas. El procedimiento GENMOD de SAS se utilizó para determinar el efecto del THI y el mes de inseminación sobre las tasas de preñez (P/AI). Resultados: el incremento del THI de ≤ 70 a ≥ 95 unidades se asoció con una disminución en el P/AI de 47% a 26%. El P/AI para las vacas inseminadas en días con un ITH de 85 a 90, pero con temperaturas menos cálidas antes de la inseminación, fue de seis puntos porcentuales más altos (30% vs. 36%) que en las vacas expuestas a ITH más altos antes de la inseminación. El P/AI fue mayor (p<0,05) de enero a marzo (39% a 41%) comparado con el resto de los meses del año (27-35%). El número de servicios por preñez fue mayor (p<0,05) de mayo a julio (3,0 a 3,4) que en los otros meses del año (2,1 a 3,0). Conclusiones: en este ambiente extremadamente caliente (temperaturas máximas > 38 °C la mayor parte del año) y árido (promedio de precipitación anual de 230 mm), el estrés calórico poco antes o después de la inseminación disminuye drásticamente las probabilidades de establecer una gestación en vacas de alta producción de leche.

Background: high environmental temperature coupled with high humidity can result in reproductive failure in dairy cattle, with a drastic reduction in reproductive efficiency of dairy herds. Objective: to study the effect of high environmental temperature on reproduction performance of Holstein cows treated with recombinant bovine somatotropin (rbST) throughout lactation in an arid environment. Methods: reproductive variables (n=18,037 services) from a large dairy herd were evaluated with respect to the maximum temperaturehumidity index (THI) prior to breeding, on the breeding day, and after breeding. The GENMOD procedure of SAS was used to assess the effect of THI and month of breeding on pregnancy by artificial insemination (P/AI). Results: increased THI from ≤ 70 to ≥ 95 units was associated with a decrease in P/AI from 47% to 26%. P/AI for cows inseminated on extremely hot days (THI= 85 to 90) preceded by cooler temperatures was six percent points higher than cows subjected to high temperatures before breeding. P/AI was higher (p<0.05) from January to March (39% to 41%) compared with the rest of the year (27% to 35%). The average number of inseminations per pregnancy was higher (p<0.05) from May to July (3.0 to 3.4) compared to other months (2.1 to 3.0). Conclusions: in this particular hot-arid environment (maximum temperature >38 ºC most of the year, and 230 mm mean annual rainfall), heat stress shortly before or after breeding severely compromises the breeding success of high yielding Holstein cows.

Antecedentes: a associação entre alta temperatura e umidade no ambiente pode originar problemas reprodutivos, diminuindo o índice de fertilidade dos rebanhos leiteiros. Objetivo: avaliar o efeito da elevada temperatura ambiente sobre o desempenho reprodutivo de vacas da raça Holandês mantidas num ambiente quente e árido, as quais foram tratadas com somatotropina bovina recombinante (rBST) durante toda a lactação. Métodos: as variáveis reprodutivas (n = 18037 serviços) de um rebanho leiteiro foram avaliadas em relação ao máximo índice de temperatura-umidade (THI), antes, durante e depois da inseminação artificial das vacas. O procedimento GENMOD do SAS foi usado para avaliar o efeito do THI e do mês de reprodução sobre as taxas de gestação por inseminação artificial (P/AI). Resultados: o aumento do THI de ≤ 70 para ≥ 95 unidades foi associado com a diminuição no índice P/AI, de 47% a 26%. Em dias com THI de 85 - 90, mas com menor temperatura ambiental antes da inseminação, o índice P/AI foi 6% maior do que nas vacas expostas a superior THI. O índice P/AI foi maior (p<0,05) de janeiro a março (39% a 41%), em comparação aos outros meses do ano (27 a 35%). O número médio de inseminações por prenhez foi superior (p<0,05) de maio a julho (3,0 a 3,4) quando comparado aos outros meses do ano (2,1 a 3,0). Conclusões: em ambiente quente e seco (temperaturas máximas > 38°C a maior parte do ano, média de precipitação anual de 230 mm) o estresse térmico antes e depois da inseminação reduz drasticamente a possibilidade de estabelecer uma gestação em vacas de alta produção de leite.

Limited data is available on reproductive seasonality in French Alpine goat bucks raised under intensive conditions in northern Mexico, at subtropical latitude (26° N). A study was done of eleven young French Alpine bucks subject to natural, regional photoperiod variations (13:41 h/light at summer solstice; 10:19 h/light at winter solstice). Animals were fed alfalfa hay (17% CP) ad libitum and a commercial supplement (14% CP) at 200 g animal-1 day-1 during the experimental period (December to September). Sperm motility increased (P<0.05) from 1.5 units from January to May to 2.5 units from July to September. Sperm viability also increased, from 25 % in January to May to 40 % in July to September. Ejaculate volume was 0.1 ± 0.03 ml ejaculate-1 from January to July, lower (P<0.05) than the 0.5 ± 0.04 ml ejaculate-1 recorded in August, September and December. Latency to ejaculate in an artificial vagina decreased (P<0.05) from 102 ± 7 sec in December to July, to 52 ± 1 sec in August and September. The studied French Alpine bucks exhibited seasonality in semen quality characteristics, body and testicular variables and sexual response, with generally lower variable values and less sexual activity from January to July followed by increased values and activity.

El objetivo del presente estudio fue determinar un posible patrón de estacionalidad reproductiva de los machos cabríos de la raza Alpino-Francés adaptados a condiciones intensivas del subtrópico Mexicano (26° LN). El estudio consideró 11 machos, los cuales fueron sometidos a las variaciones naturales del fotoperiodo de la Comarca Lagunera (13:41 h/luz durante el solsticio de verano y 10:19 h/luz en el solsticio de invierno). Los animales tuvieron libre acceso a heno de alfalfa (17 % PC) y 200 g de concentrado comercial (14 % PC) animal-1 día.1, durante todo el período experimental (diciembre a septiembre). Se observó una disminución (P<0.05) en la motilidad progresiva y el porcentaje de espermatozoides vivos al pasar de 1.4 ± 0.1 (escala de 1-5) y 21 ± 2 % de enero a junio, a valores de 2.5 ± 0.2 y del 49 ± 4 % durante julio a diciembre, respectivamente. La latencia a eyacular en vagina artificial fue de 102 ± 7 seg de diciembre a julio, observando una reducción a 52 ± 1 seg entre agosto y septiembre. El volumen del eyaculado fue de 0.1 ± 0.03 ml eyaculado-1 de enero a julio, observando un incremento a 0.5 ± 0.04 ml eyaculado-1 durante agosto, septiembre y diciembre. Los resultados del estudio demuestran que machos cabríos Alpino-Francés jóvenes criados con un esquema intensivo a 26° LN en el subtrópico mexicano muestran un patrón estacional con respecto a calidad espermática, libido y peso testicular que se extiende de enero a julio en esta latitud.

Recent developments in molecular biology and statistics have opened the possibility of identifying and using genomic variation and major genes for the genetic improvement of livestock. Information concerning the basis of these techniques and their applications to the genetic improvement of animals is reviewed. Main marker molecular marker systems in animals (RFPL and microsatellites), genome maps, methods for detecting marker major gene linkages and use of marker assisted selection, genetic fingerprinting and mixture models based on segregation analysis are analyzed. The characteristics where the application of marker assisted selection can be more effective are those that are expressed late in the life of the animal, or controlled by a few pairs of genes. The first example correspond to the longevity and carcass characteristics in meat producing animals, the second, to the resistance to certain diseases or defects of simple inheritance. The detection of major genes using mixture models with segregation analysis can direct the work of identification of DNA marker genotypes towards populations and characteristics with greater probability of detecting a major gene using molecular markers. The present trend indicates that molecular, pedigree and phenotypic information will be integrated in the future through mixture models of segregation analysis that might contain major gene effects through the markers, polygenic inheritance and uses powerful and flexible methods of estimation such as Gibbs Sampling.