Estrés por calor en ganado lechero con énfasis en la producción de leche y los hábitos de consumo de alimento y agua. Revisión

The negative impact of heat stress (HS) in dairy cattle results in considerable economic losses at world level, as it reduces the milk production, reproductive efficiency, and productive life in the cows. In addition, the continuous genetic improvement results in highly productive cows, which are, however, less tolerant to HS because they produce greater metabolic heat. This, together with global warming, will turn HS into a hard-to-control challenge for the daily industry. In response dependent on the degree of HS, the dairy cattle carry out a series of physiological, metabolic and behavioral adjustments as thermoregulatory mechanisms for removing excess body heat and reducing the endogenous production of body heat, in order to maintain the normothermia. However, fertility and milk secretion decrease as a direct effect of hyperthermia and an indirect effect of lower dietary nutrient intake. Food and water intake are closely associated to the reduction of the productivity of dairy cattle exposed to HS. Notably, the impact of HS on productivity of dairy cattle varies among breeds, among which Bos taurus, particularly the Holstein breed, are less tolerant to HS. The identification of genes associated to thermotolerance utilized in selection programs using genetic markers to breed high milk-producing cows in warm climates is currently being studied. Therefore, the purpose of this review is to carry out a comprehensive analysis of the effects of HS on milk production, activation of thermoregulatory mechanisms and feed intake behavior in dairy cattle.El impacto negativo del estrés por calor (EC) en la ganadería lechera repercute en cuantiosas pérdidas económicas a nivel mundial, dado que reduce la producción de leche, la eficiencia reproductiva y la vida productiva de las vacas. Adicionalmente, el mejoramiento genético continuo resulta en vacas muy productivas, pero menos tolerantes al EC debido a que producen mayor calor metabólico. Esto en conjunto con el calentamiento global convertirá al EC en un reto difícil de controlar para la industria lechera. Como respuesta dependiente del grado de EC, el ganado lechero realiza una serie de ajustes fisiológicos, metabólicos y conductuales como mecanismos de termorregulación para disipar el exceso de calor corporal y reducir la producción endógena del mismo, todo dirigido a mantener la normotermia. Sin embargo, la secreción láctea y la fertilidad se reducen por efecto directo de la hipertermia e indirectamente por la reducción en el consumo de nutrientes dietéticos. Los consumos de alimento y de agua están asociados estrechamente con la reducción de la productividad en ganado lechero expuesto a EC. Cabe mencionar que el impacto del EC en la productividad del ganado lechero varía entre razas, siendo las razas Bos taurus menos tolerantes al EC, particularmente la raza Holstein. Actualmente, se investiga en la identificación de genes asociados con la termotolerancia, los cuales son empleados en programas de selección por marcadores genéticos para producir vacas altas productoras de leche en climas cálidos. Por lo tanto, el objetivo de esta revisión es hacer un análisis comprensivo de los efectos del EC sobre la producción de leche, activación de mecanismos de termorregulación y conducta de ingesta en ganado lechero

Prevalence and risk factors for stillbirths in Holstein cows in a hot environment

Risk factors for stillbirth were studied in a dairy operation in northern Mexico (25°N). Data set consisted of 29406 full term calving records. Factors affecting stillbirths were analyzed using a step-wise multivariable logistic regression models. The predictive indicators of stillbirth risk were: temperature-humidity index (THI) during pregnancy and at calving, season of calving, calf birth weight, gestation length, semen characteristics (conventional or sexed), gender of calves, hour of calving and type of parturition (normal or dystocic). Throughout the study period, 7.3 (95%, confidence interval= 7.0–7.6) of every 100 calving events had a stillborn calf. Stillborns were higher with severe dystocia compared with non-assisted births (29.0% vs. 6.2%, p<0.0001) and calves with birth weights <35 kg compared with heavier calves at calving (19.3% vs. 2.3%, p<0.0001), and was lower in calves whose gestation length was >278 d compared with calves with shorter gestation periods (2.8% vs. 30.0%, p<0.0001). Cows in a severe state of heat stress prenatally and at birth (THI >83 units) had 1.3 higher risk of stillbirths than cows suffering reduced heat stress (p<0.0001). Evidence for a greater (p<0.001) stillbirth rates in cows with parturitions between 18:00 and 19:00 h compared with cows calving during other hours of the day was found (9.1% vs. 7.1%). Together, these results demonstrate that ameliorating heat stress during the peripartum period is an important management practice to reduce stillbirths in Holstein cows in this warm climate. Additionally, a greater attention of parturition around sunset can lower the current stillbirth rates

Usporedba djelovanja korionskog gonadotropina konja (eCG) i estradiol cipionata primijenjenih 24 sata nakon prestanka kontrolirane primjene progesterona kao dijela protokola za sinkronizaciju estrusa i umjetno osjemenjivanje meksičkog Criollo goveda.

Two experiments were conducted to evaluate the effect of administering equine chorionic gonadotropin (eCG) in substitution of estradiol, 24 h after the removal of a progesterone intravaginal device, on estrus and ovulatory response, and pregnancy rates of Rodeo Criollo cows (exp. 1, n = 21) and heifers (exp. 2, n = 39) subjected to a synchronization protocol (estradiol + CIDR + PGF2α) with estrus-detected artificial insemination. All females were inseminated 12 h after detected estrus. In cows, estrus and ovulation response, and maximum pre-ovulatory follicle diameter were similar (P>0.05) between equine chorionic gonadotropin and estradiol groups. However, the time to estrus was shorter (P0.05) in ovulation rate. Both treatments resulted in low pregnancy rates, with a significantly lower (P0,05) u skupinama krava kod kojih je bio primijenjen korionski gonadrotropin ili estradiol. Međutim, u skupini kod koje je bio primijenjen estradiol vrijeme do estrusa je bilo kraće (P0,05) u stopi ovulacije. Oba su postupka dovela do niže stope gravidnosti, pri čemu je smanjenje kod junica kojima je bio primijenjen korionski gonadotropin konja bilo signifikantno (P<0,05). Zaključno, primjena korionskog gonadotropina konja, kao zamjene za estradiol nakon uklanjanja sredstva za otpuštanje progesterona, dovela je u sklopu protokola za otkrivanje estrusa i umjetno osjemenjivanje do povećanog grupiranja estrusa i ovulacije te posljedično veće stope gravidnosti u krava, ali ne i u junica

Usporedba djelovanja korionskog gonadotropina konja (eCG) i estradiol cipionata primijenjenih 24 sata nakon prestanka kontrolirane primjene progesterona kao dijela protokola za sinkronizaciju estrusa i umjetno osjemenjivanje meksičkog Criollo goveda.

Two experiments were conducted to evaluate the effect of administering equine chorionic gonadotropin (eCG) in substitution of estradiol, 24 h after the removal of a progesterone intravaginal device, on estrus and ovulatory response, and pregnancy rates of Rodeo Criollo cows (exp. 1, n = 21) and heifers (exp. 2, n = 39) subjected to a synchronization protocol (estradiol + CIDR + PGF2α) with estrus-detected artificial insemination. All females were inseminated 12 h after detected estrus. In cows, estrus and ovulation response, and maximum pre-ovulatory follicle diameter were similar (P>0.05) between equine chorionic gonadotropin and estradiol groups. However, the time to estrus was shorter (P0.05) in ovulation rate. Both treatments resulted in low pregnancy rates, with a significantly lower (P0,05) u skupinama krava kod kojih je bio primijenjen korionski gonadrotropin ili estradiol. Međutim, u skupini kod koje je bio primijenjen estradiol vrijeme do estrusa je bilo kraće (P0,05) u stopi ovulacije. Oba su postupka dovela do niže stope gravidnosti, pri čemu je smanjenje kod junica kojima je bio primijenjen korionski gonadotropin konja bilo signifikantno (P<0,05). Zaključno, primjena korionskog gonadotropina konja, kao zamjene za estradiol nakon uklanjanja sredstva za otpuštanje progesterona, dovela je u sklopu protokola za otkrivanje estrusa i umjetno osjemenjivanje do povećanog grupiranja estrusa i ovulacije te posljedično veće stope gravidnosti u krava, ali ne i u junica

Análisis económico del uso de clorhidrato de zilpaterol en la alimentación de corderas

Con el objetivo de realizar un análisis económico sobre el uso de clorhidrato de zilpaterol en ovinos se realizó una investigación con datos provenientes de la engorda de 24 corderas Dorper - Pelibuey en finalización mediante la técnica de costos, ingresos y rentabilidad. Los animales se dividieron en dos grupos de 12 corderas cada uno: Testigo (T1), alimentados con una dieta basal + 100 g de trigo molido, y (T2), que recibieron la dieta basal + 100 g de trigo molido con 10 mg de clorhidrato de zilpaterol (CZ) cada animal durante 24 horas, por 34 días. El contenido de la dieta tuvo 15.8% de proteína cruda (PC) y 2.8 Mcal/kg de energía metabolizable (EM), con un costo de producción de $3.96 por kg. Las variables de interés fueron peso inicial, peso final, ganancia de peso, conversión alimenticia y peso en canal. Para T1 el costo de producción, ingreso y ganancia/animal, por venta en canal, fueron de$823.1, $918.4 y$95.3, mientras que para T2 fueron de $863.8,$1,111.0 y $247.1, respectivamente. Asimismo,la relación beneficio-costo (RB/C) en canal para T1 fue de 1.11 y para T2 de 1.29. Se concluye que la rentabilidad fue mayor en animales suplementados en la dieta con clorhidrato de zilpaterol en relación con los animales testigo

Zilpaterol hydrochloride improves growth performance and carcass traits without affecting wholesale cut yields of hair sheep finished in feedlot

Growth of the sheep meat industry throughout the world has been slow compared with meat industries of other domestic animals. Therefore, increasing productivity and efficiency of sheep meat production are key factors to enhance the competi- tiveness of this industry (Montossi et al. 2013). The use of β2- adrenergic agonists (β2-AA) as growth promoters has demon- strated to increase sheep meat production by improving protein deposition in muscle (Domínguez-Vara et al. 2013). The use of such technology in the lamb fattening systems could be a nutritional strategy to improve their competitiveness.Fourteen Dorper × Pelibuey ram lambs (initial body weight [BW] = 37.4 ± 1.0 kg and age = 4.5 mo) were housed in individual pens during a 30-d feeding period, and then slaughtered to determine the effects of zilpaterol hydrochloride (ZH) supplementation on productive performance, carcass characteristics and wholesale cut yields. Lambs were assigned under a randomized complete block design (initial BW as blocking factor) to one of two dietary treatments: basal diet without (control) or with 10 mg daily of ZH/lamb. Lambs fed ZH had greater (P ≤ .04) final BW, average daily gain and dry matter intake, but similar (P = .24) feed efficiency compared with control lambs. Hot and cold carcass weight, dressing percentage, longissimus muscle area and leg perimeter were greater (P ≤ .05) for ZH-fed lambs than for control lambs. With exception of blood percentage which decreased (P < .01) with ZH, wholesale cut yields and non-carcass components were unaffected (P ≥ .12) by ZH supplementation. In conclusion, ZH can be used to improve growth rate and dressing percentage, but not to increase wholesale cut yields in feedlot finishing ram lambs.This study was supported by PROMEP-SEP under the thematic network ‘Uso de Promotores de Crecimiento en Ovinos de Pelo (2014–2017

Vaccination programs, parity, and calving season as factors affecting the risk of fetal losses and mummified fetuses in Holstein cows

Aim of the study: To investigate vaccination programs, parity, and calving season as factors affecting the risk of abortion and mummified fetuses in Holstein cows.Area of study: Hot zone of Northeast Mexico.Material and methods: Multiple logistic regression models were used to examine the relationship between peripartum disorders, parity, previous occurrence of abortion, season of calving, vaccination program, incidence of abortion, and mummified fetuses in Holstein cows.Main results: For 7014 pregnancies (2886 cows), the percentage of cows aborting and having mummified fetuses was 17.7% and 1.1%, respectively. As the number of brucellosis vaccinations increased, the incidence of abortion increased (10.4% for a single vaccination and 38.0% for 6 accumulated vaccinations). Abortion for cows having 1-2 previous abortions (56%) and &gt;2 abortions (77%) was fivefold and sevenfold greater (p&lt;0.01), respectively, than that for cows without previous abortion. Other important risk factors for abortion were number of calvings (19.8% for nulliparous and primiparous vs. 13.8% for &gt;3 parturitions; OR=1.7, p&lt;0.01), leptospirosis vaccine application &lt;55 days postpartum (dpp; OR=1.3, p&lt;0.05), viral vaccine application &gt;37 dpp (OR=1.3, p&lt;0.01), brucellosis vaccine application &gt;20 dpp (OR=1.6, p&lt;0.01), and no application of clostridial vaccine (OR=3.7, p&lt;0.01). Significant risk factors for mummified fetuses were application of ≥3 brucellosis vaccinations (OR=3.3, p&lt;0.01), no application of 10-way clostridial vaccine (OR=2.3, p&lt;0.01), &gt;2 previous abortions (OR=18.4, p&lt;0.01), and calving in autumn (OR=0.4, compared to winter, p&lt;0.05).Research highlights: Risk of abortion and mummified fetuses in Holstein cows has been found to be related to vaccination programs

La hipocalcemia en la vaca lechera. Revisión

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.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