The challenge of the genetic selection of animals that tolerate heat stress. The case of dairy cattle

The physiological stress produced by exposure to high thermal loads has negative effects on the productive and reproductive performance of livestock, as well as on the morbidity and mortality rate. The animals specialized in dairy production suffer to a greater extent the negative effects of heat than animals of meat breeds due to the high metabolic heat that is generated during the production of milk. In addition, the high selection pressure to increase milk production in cattle intensifies the vulnerability of these animals to heat stress (HS). Furthermore, predictions about the consequences of climate change are expected to exacerbate the problem of HS in dairy farms in the future. The negative impact of the HS can be mitigated in several ways, through improvements in livestock housing, through the genetic selection of heat-tolerant animals or the use of breeds adapted to heat and through the management of food. The path of genetic selection of tolerant animals represents a cumulative and permanent effect, with a relatively low associated cost if it is integrated into selection schemes already established for other characters. The selection of HS-tolerant animals, however, presents a series of challenges derived from the complexity of the mechanisms that determine this tolerance and the antagonism with the level of production. This paper summarizes the results of previous studies on the physiological response and genes associated with HS, as well as the possible approaches to the genetic improvement of heat tolerance, including the use of new genomic and transcriptomic information tools and the so-called fine phenotyping

Determination of faecal dry matter digestibility two weeks after weaning in twenty five day old weaned rabbits

[EN] The aim of this work was to analyse the evolution from 26 to 40 d of age of apparent faecal dry matter digestibility (DMd) in rabbits weaned at 25 d of age to define how to determine nutrient digestibility in the post-weaning period. Fifteen New Zealand ' Californian rabbits from five litters (3 rabbits/litter) weaned at 25 d of age and weighing 602±75g were fed ad libitum a commercial diet containing 20.0% crude protein and 33.5% NDF (on DM basis). Feed intake and faeces excretion were recorded daily from 25 to 40 d of age and DM digestibility determined. Litter affected DM intake and excretion (P = 0.013 and 0.014, respectively), and tended to affect DMd (P = 0.061), whereas age influenced all these traits (P < 0.001). Dry matter intake and DM excretion increased from 26 to 40 d of age by 158 and 480%, respectively. During the first week after weaning, DM intake increased more slowly than DM excretion (55 vs. 245%), but in the second week after weaning both increased by 67%. The correlation between daily feed intake was higher with the faeces excretion of the same day than with faeces excretion of the next day, and the first values were used to determine daily DMd. A broken line regression model was fitted to daily DMd, which decreased linearly from weaning to 32 d of age (2.17 ± 0.25 percentage units per day), whereas from 32 to 40 d it remained constant (69.4 ± 0.47%). Accordingly, for 25-d old weaned rabbits it would be advisable to begin a digestibility trial not before 32 d of age, using the first week after weaning as adaptation period. Average standard deviation of DMd decreased by 54% when the length of the collection period increased from 2 to 6 d. Consequently, the number of animals required to detect a significant difference among means depends on the length of the collection period. For a conventional collection period of four days, a difference of 2 percentage units could be detected by using 14 animals/treatment.Gómez-Conde, M.; García, J.; Villamide, M.; Carabaño, R. (2011). Determination of faecal dry matter digestibility two weeks after weaning in twenty five day old weaned rabbits. World Rabbit Science. 19(1):43-48. doi:10.4995/wrs.2011.816SWORD434819

A comprehensive characterisation of the fibre composition and properties of a limb (Flexor digitorum superficialis, membri thoraci) and a trunk (Psoas major) muscle in cattle

<p>Abstract</p> <p>Background</p> <p>The fibre type attributes and the relationships among their properties play an important role in the differences in muscle capabilities and features. Comprehensive characterisation of the skeletal muscles should study the degree of association between them and their involvement in muscle functionality. The purposes of the present study were to characterise the fibre type composition of a trunk (<it>Psoas major</it>, PM) and a limb (<it>Flexor digitorum, membri thoraci</it>, FD) muscle in the bovine species and to study the degree of coordination among contractile, metabolic and histological properties of fibre types. Immunohistochemical, histochemical and histological techniques were used.</p> <p>Results</p> <p>The fibre type composition was delineated immunohistochemically in calf muscle samples, identifying three pure (I, IIA, and IIX) and two hybrid type fibres (I+IIA, and IIAX). Most of the fibres in FD were types I and IIA, while pure IIX were absent. All fibre types were found in PM, the IIX type being the most frequent. Compared to other species, small populations of hybrid fibres were detected. The five fibre types, previously identified, were ascribed to three different acid and alkaline mATPase activity patterns. Type I fibres had the highest oxidative capacity and the lowest glycolytic capacity. The reverse was true for the IIX fibres, whereas the type IIA fibres showed intermediate properties. Regarding the histological properties, type I fibres tended to be more capillarised than the II types. Correlations among contractile, metabolic and histological features on individual fibres were significantly different from zero (r values varied between -0.31 and 0.78). Hybrid fibre values were positioned between their corresponding pure types, and their positions were different regarding their metabolic and contractile properties.</p> <p>Conclusion</p> <p>Coordination among the contractile, metabolic and histological properties of fibres has been observed. However, the magnitude of the correlation among them is always below 0.8, suggesting that the properties of muscles are not fully explained by the fibre composition. These results support the concept that, to some extent, muscle plasticity can be explained by the fibre type composition, and by the properties derived from their metabolic and histological profiles.</p

Cytomegalovirus erosive gastritis in a healthy infant: update about a case

El citomegalovirus es un virus ADN de la familia Herpesviridae que puede afectar al tubo digestivo. Dentro de éste, las dianas de afectación suelen ser el colon, el esófago y el estómago. Se ha descrito ampliamente su asociación con el síndrome de Ménétrier (hiperplasia foveolar con pérdida de proteínas), si bien también puede producir cuadros de gastritis erosiva. En el presente artículo se describe un caso de gastritis erosiva en una lactante sana de 4 meses de edad, que se inició en forma de hemorragia digestiva alta. A partir de este caso, se lleva a cabo una puesta al día de este subgrupo de infecciones por citomegalovirusCytomegalovirus is a DNA Herpesviridae family which can affect the digestive tract. From the standpoint of the stomach, has been widely described his association with Ménétrier syndrome (foveolar hyperplasia with protein-losing) but can also produce erosive gastritis. This article describes a case of erosive gastritis in a healthy 4 months infant which debuted as upper gastrointestinal bleeding. In addition we perform an update of this subgroup of cytomegalovirus infection

Evolución con la edad de los mecanismos de barrera intestinal

Se destetaron 106 gazapos de 20 camadas a los 26 d de edad con un peso de 429 ± 57 g y se sacrificó 1 animal por camada a los 26, 31, 38, 45 y 52 d de edad. La longitud de las vellosidades intestinales y la profundidad de las criptas en el yeyuno se redujeron entre los 26 y los 31 d en un 26 y 9% respectivamente. De los 31 a los 38 días se observó un aumento tanto de la longitud de las vellosidades como de las criptas. A partir de esta edad no se observaron cambios en las vellosidades, que mostraron valores similares a las determinadas en el destete, mientras que las criptas siguieron aumentando ligeramente (9%). El grado de similitud de la microbiota cecal entre animales de la misma edad (que varió entre un 89, 1 y un 95,3%) fue superior al grado de similitud entre animales de diferentes edades (que varió entre un 82,3% y un 92,5%). La variabilidad en la composición de la microbiota fue menor a los 45 y 52 d de edad (mostrando un grado de similitud del 92,5% entre ambas edades) en comparación con la observada entre las primeras edades (26, 31 y 38 d, que varió entre 82,3 y 86,7%). Los menores grados de similitud se observaron entre los animales lactantes y los animales de 31 y 38 d de edad

Characterisation of Goats’ Response to Heat Stress: Tools to Improve Heat Tolerance

This chapter aims to review present knowledge about the effects of heat stress on goats, summarising what is known about its measurement, its impact on the performances of the animals, mainly milk traits, the physiological and genetic bases of the animals’ response and the improvement of resilience through selection. A short historic review of the climatic indexes used to measure heat stress, with special emphasis on the temperature humidity indexes, and the main consequences on milk yield and composition are followed by a description of the results of experiments carried out to study the physiological and metabolic consequences of heat stress. The results of the quantitative analyses of the genetic bases of heat stress using norm of reaction models and of the application of omic techniques, particularly transcriptomic and genomic, to understand the complexity of the genetic background of animal’s reaction to thermal stress, constitute the next points. The chapter ends treating the possible ways and difficulties of applying selection to increase resilience to heat stress

Assessment of heterogeneity of residual variances using changepoint techniques

Several studies using test-day models show clear heterogeneity of residual variance along lactation. A changepoint technique to account for this heterogeneity is proposed. The data set included 100 744 test-day records of 10 869 Holstein-Friesian cows from northern Spain. A three-stage hierarchical model using the Wood lactation function was employed. Two unknown changepoints at times T1 and T2, (0 <T1 <T2 <tmax), with continuity of residual variance at these points, were assumed. Also, a nonlinear relationship between residual variance and the number of days of milking t was postulated. The residual variance at a time t() in the lactation phase i was modeled as: for (i = 1, 2, 3), where λι is a phase-specific parameter. A Bayesian analysis using Gibbs sampling and the Metropolis-Hastings algorithm for marginalization was implemented. After a burn-in of 20 000 iterations, 40 000 samples were drawn to estimate posterior features. The posterior modes of T1, T2, λ1, λ2, λ3, , , were 53.2 and 248.2 days; 0.575, -0.406, 0.797 and 0.702, 34.63 and 0.0455 kg2, respectively. The residual variance predicted using these point estimates were 2.64, 6.88, 3.59 and 4.35 kg2 at days of milking 10, 53, 248 and 305, respectively. This technique requires less restrictive assumptions and the model has fewer parameters than other methods proposed to account for the heterogeneity of residual variance during lactation

Objectives, organization and limiting factors of selection programs for indigenous breeds in Spain

Ponencia publicada en ITEA, vol.104En esta ponencia invitada se resumen las principales características de los programas de selección de las razas autóctonas que se están llevando a cabo en España. Se describen para cada una de ellas la población controlada, los caracteres registrados, los objetivos y criterios de selección, la valoración genética de los reproductores, los aspectos organizativos, la utilización de la información por parte de los ganaderos y los factores limitantes del progreso genético. Los más antiguos de estos programa comenzaron al principio de la década de los 80 del pasado siglo, la mayoría lo hicieron al final de dicha década o en la siguiente y unos pocos en la década actual. Debido a esta disparidad de fechas de iniciación y a otros factores estructurales y organizativos, sus niveles de desarrollo y efectividad son muy variables. Entre los factores limitantes de dicho desarrollo y efectividad más frecuentemente citados se encuentran los reducidos tamaños de los núcleos de selección, la reducida implantación de la I.A. y, consecuentemente, el bajo número de sementales en prueba de descendencia y las bajas fiabilidades de las valoraciones genéticas, la escasa utilización por parte algunos de los ganaderos de las valoraciones genéticas de sus animales para elegir la reposición en los rebaños y, en un cierto número de casos, la escasa participación e interés de los mismos.This invited contribution summarizes the most important characteristics of selection programs being applied to Spanish indigenous breeds. Population and traits being recorded, selection objectives and criteria, breeding values estimation, managing aspects, diffusion to and use of genetic information by breeders and constraints to genetic progress are synthetically described for each breed. The oldest programs started at the beginning of the eighties of the last century. Most of them began at the end of the eighties or in the nineties and a few were initiated within present decade. Due to these age differences, and to other structural and managing factors, their developmental and effectiveness levels are very variable. Small number of animals being registered and, therefore, selected, low number of dams inseminated an its consequence on the capacity to sire testing and on the reliability of estimated breeding values, the scanty use that some of the breeders make of the genetic evaluations and the low participation of farmers in the programs, are among the most important factors limiting their development and their effectiveness in terms of genetic progress obtained

Modélisation des performances de reproduction de la population caprine locale dans les régions arides tunisiennes

La présente étude vise à illustrer l’action qualitative et quantitative de facteurs d’aridité et des modes de conduite sur les performances reproductives de la chèvre locale. Un total de 462 mises bas provenant de l'accouplement de 11 boucs et 185 chèvres, ont été recueillies durant la période 1999-2014. Deux caractères ont été choisis pour analyser les performances de reproduction :la taille de la portée et l’intervalle entre deux mises bas successives. Les facteurs fixes inclus dans le modèle sont l’âge et la parité de la chèvre et l’interaction année × mois de mise bas.  Les moyennes de l’IMB et de la TP sont respectivement 13,85 ± 5,20 mois et de 1,33 ± 0,49 chevreaux. Les jeunes femelles ont montré des performances de reproduction relativement plus faibles que celles des chèvres âgées, indiquant des conflits possibles entre les besoins de croissance et la disponibilité alimentaire. Les performances de reproduction de la chèvre locale affichent des valeurs justifiables par les conditions naturelles hostiles. Il semble avoir une augmentation générale du TP à mesure que la parité progresse jusqu'à la cinquième parité. Une large valeur d’IMB a été observée pour la deuxième parité puis elle tend à diminuer. Le cycle reproductif des chèvres est essentiellement soumis aux effets des facteurs qui agissent sur les ressources pastorales et le stress climatique. Ces constations sont capitales pour l’élaboration des procédures d’évaluation et de choix des reproducteurs dans le cadre d’un schéma de sélection