The first complete T2T Assemblies of Cattle and Sheep Y-Chromosomes uncover remarkable divergence in structure and gene content.

Reference genomes of cattle and sheep have lacked contiguous assemblies of the sex-determining Y chromosome. We assembled complete and gapless telomere to telomere (T2T) Y chromosomes for these species. The pseudo-autosomal regions were similar in length, but the total chromosome size was substantially different, with the cattle Y more than twice the length of the sheep Y. The length disparity was accounted for by expanded ampliconic region in cattle. The genic amplification in cattle contrasts with pseudogenization in sheep suggesting opposite evolutionary mechanisms since their divergence 18MYA. The centromeres also differed dramatically despite the close relationship between these species at the overall genome sequence level. These Y chromosome have been added to the current reference assemblies in GenBank opening new opportunities for the study of evolution and variation while supporting efforts to improve sustainability in these important livestock species that generally use sire-driven genetic improvement strategies.

Effects of wildfire smoke PM2.5 on indicators of inflammation, health, and metabolism of preweaned Holstein heifers.

Wildfires are a growing concern as large, catastrophic fires are becoming more commonplace. Wildfire smoke consists of fine particulate matter (PM2.5), which can cause immune responses and disease in humans. However, the present knowledge of the effects of wildfire PM2.5 on dairy cattle is sparse. The present study aimed to elucidate the effects of wildfire-PM2.5 exposure on dairy calf health and performance. Preweaned Holstein heifers (N = 15) were assessed from birth through weaning, coinciding with the 2021 wildfire season. Respiratory rate, heart rate, rectal temperatures, and health scores were recorded and blood samples were collected weekly or twice a week for analysis of hematology, blood metabolites, and acute phase proteins. Hourly PM2.5 concentrations and meteorological data were obtained, and temperature-humidity index (THI) was calculated. Contribution of wildfires to PM2.5 fluxes were determined utilizing AirNowTech Navigator and HYSPLIT modeling. Mixed models were used for data analysis, with separate models for lags of up to 7 d, and fixed effects of daily average PM2.5, THI, and PM2.5 × THI, and calf as a random effect. THI ranged from 48 to 73, while PM2.5 reached concentrations up to 118.8 µg/m3 during active wildfires. PM2.5 and THI positively interacted to elevate respiratory rate, heart rate, rectal temperature, and eosinophils on lag day 0 (day of exposure; all P < 0.05). There was a negative interactive effect of PM2.5 and THI on lymphocytes after a 2-d lag (P = 0.03), and total white blood cells, neutrophils, hemoglobin, and hematocrit after a 3-d lag (all P < 0.02), whereas there was a positive interactive effect on cough scores and eye scores on lag day 3 (all P < 0.02). Glucose and NEFA were increased as a result of combined elevated PM2.5 and THI on lag day 1, whereas BHB was decreased (all P < 0.05). Contrarily, on lag day 3 and 6, there was a negative interactive effect of PM2.5 and THI on glucose and NEFA, but a positive interactive effect on BHB (all P < 0.03). Serum amyloid A was decreased whereas haptoglobin was increased with elevated PM2.5 and THI together on lag days 0 to 4 (all P < 0.05). These findings indicate that exposure to wildfire-derived PM2.5, along with increased THI during the summer months, elicits negative effects on preweaned calf health and performance both during and following exposure.

Wildfires contribute to fine particulate matter (PM2.5) pollution throughout the United States. Wildfire-PM2.5 exposure negatively affects human health and dairy cow production; however, the effects on calves are not known. We monitored preweaned calves exposed to natural wildfires to understand how wildfire-PM2.5 exposure affects calf health and performance. Calves exposed to wildfire PM2.5 and elevated temperature­humidity index (THI) experienced respiratory symptoms, alterations in blood cell composition and metabolism, and changes in circulating inflammatory proteins. These results suggest that PM2.5 along with increased THI induced an inflammatory response and alterations in energy metabolism that may contribute to calf health and performance deficits.

Mitochondrial Bioenergetics of Extramammary Tissues in Lactating Dairy Cattle.

Lactation is physiologically demanding, requiring increased nutrient and energy use. Mammary and extramammary tissues undergo metabolic changes for lactation. Although it has long been recognized that mitochondria play a critical role in lactation, the mitochondrial adaptations for milk synthesis in supporting tissues, such as liver and skeletal muscle are relatively understudied. In this study, we assessed the mitochondrial function in these tissues across lactation in dairy cattle. Tissue biopsies were taken at 8 ± 2 d (early, n = 11), 75 ± 4 d (peak, n = 11) and 199 ± 6 d (late, n = 11) in milk. Early lactation biopsies were harvested from one group of cows and the peak and late biopsies from a second cohort. Milk yield (MY) was recorded at each milking and milk samples were collected for composition analysis. Mitochondrial efficiency was quantified as the respiratory control ratio (RCR), comparing maximal to resting respiration rates. Liver complex II RCR was positively associated with MY. Liver ROS emission increased across lactation whereas liver antioxidant activity was similar across lactation. No change was detected in skeletal muscle RCR or ROS emission, but muscle GPx activity decreased across lactation and muscle SOD was negatively associated with MY. Muscle oxidative damage was elevated at early and late lactation. Across lactation, genes involved in mitochondrial biogenesis were upregulated in the liver. Our results indicate that during lactation, liver mitochondrial biogenesis and efficiency are increased, which is associated with greater milk yield. In contrast, the mitochondrial efficiency in skeletal muscle remains consistent across lactation, but undergoes oxidative damage, which is associated with reduced antioxidant activity.

Expression and distribution of the complement receptor gC1qR bovine sperm

El gC1qR, un receptor para el dominio globular del C1q, es una proteína multicompartamental y multifuncional, cuya intervención en el proceso de fecundación en humanos se ha demostrado recientemente. Los objetivos de esta investigación fueron describir la distribución de gC1qR y valorar su expresión en la membrana plasmática de espermatozoides bovinos antes y después del tratamiento con heparina. La capacitación de espermatozoides provenientes de semen descongelado bovino se indujo con una incubación con heparina y su efectividad se evaluó con la tinción CTC. Posteriormente, se realizaron ensayos de inmunofluorescencia indirecta con el anticuerpo monoclonal 60.11 (anti-gC1qR). El análisis de los datos demostró que el gC1qR es una molécula ubicada en la membrana plasmática de los espermatozoides bovinos que presentauna redistribución tras la capacitación, concentrándose en la región acrosomal: 175 espermatozoides en las alícuotas incubadas con heparina vs. 109 en el control (P<0,05; n=300) presentaron fluorescencia en la región acrosomal; esta distribución es semejante a la documentada en humanos. Igualmente, el nivel de expresión o de accesibilidad de gC1qR en el espermatozoide bovino aumentó tras la capacitación, hecho que se ha observado también en humanos. Estos resultados sugieren que el gC1qR podría participar en la interacción primaria entre el espermatozoide y el ovocito en bovinos.

The complement receptor gC1qR/p33, which recognizes the globular heads of C1q, is a multicompartmental and multifunctional protein and has been shown to play a role in reproduction in humans. The objective of this research was to determine the gC1qR distribution and expression on plasma membrane in bovine sperm before and after heparin treatment. Thus, capacitation of sperm derived from frozen-thawed bovine semen was induced through heparin incubation and its effectiveness was assessed with a CTC stain. Subsequently, indirect immunofluorescence assays were conducted with mAb (60.11, anti-gC1qR) to assess gC1qR distribution and expression. Data analysis demonstrated that gC1qR is expressed on the plasma membrane of bovine sperm. gC1qR showed a capacitation-related redistribution, migrating to the acrosome region: 175 sperm in heparin-incubated aliquots vs. 109 in control (P<0.05, n=300) showed fluorescence over the acrosome region. This distribution is similar to that reported in humans. Similarly, either gC1qR expression or its accessibility to antibodies increased after capacitation. This also correlates with what has been observed in humans. These results suggest that gC1qR could participate in primary sperm-oocyte interaction in bovines.