Ruminants

This study assessed the productive and structural traits of the forage canopy and the performance of heifers grazing Marandu grass pastures overseeded with winter forages during the dry–wet transition in a tropical region. A completely randomized split-plot design with three replicates was used to compare three systems: Marandu grass overseeded with Oats and Ryegrass; Marandu grass overseeded with Oats and Clovers; and Marandu grass in monoculture. Holstein × Gyr heifers, averaging nine months of age with an initial body weight of 225.42 ± 50.27 kg, were managed under irrigated rotational grazing, with two days of occupation and 28 days of rest. Measurements were taken over three grazing cycles. Total forage mass and Marandu grass mass increased in the final cycle, with no differences among systems. The proportion and mass of winter forages did not differ between treatments, although overseeded pastures maintained about one-third of their composition as winter species. Animal performance was similar across systems, with greater body weight observed at the end of the experimental period. In conclusion, overseeding winter forages in irrigated Marandu grass pastures does not increase forage production or animal performance but does promote botanical diversification, with Oats showing better adaptation under these conditions. Full article

The highly compact chromatin and naturally fragmented RNA content of bovine sperm make it difficult to obtain sufficient total RNA for transcriptome sequencing. Bovine sperm studies have mostly adapted the somatic-cell protocol and used generic kits. To date, no commercial extraction kit is available for total RNA from sperm. These limitations prompted optimization of a sperm total RNA isolation protocol, tested using both fresh and cryopreserved sperm. Ejaculates were collected from two Girolando bulls (Bos taurus × Bos indicus) and were subsequently processed for cryopreservation. In total, eight RNA extraction protocols were tested, namely four TRIzol^®-based (GP) protocols and four spin-column (SC) methods. Across both fresh and cryopreserved sperm, Protocol D of SC protocols (SC-D) was the most suitable choice for total RNA sequencing. For fresh sperm, ~25–29 million filtered reads were obtained, and cryopreserved sperm yielded ~83–125 million filtered reads, indicating that cryopreserved sperm is also a good source of sperm RNA based on initial sequencing metrics. By pinpointing SC-D as the optimal balance in terms of yield and sequencing performance, and by identifying practical solutions for DNA carryover and storage-related duplication, the study’s results provide a streamlined protocol and quality control framework for total RNA sequencing of Girolando sperm. Full article

This study evaluated the effects of replacing soybean meal with cashew nut roasting residue (CNRR) on feed intake, nutrient digestibility, rumen fermentation, blood metabolites, and economic efficiency in lactating crossbred Saanen goats. Fifteen does were assigned to a completely randomized design with three treatments: 0% CNRR (T1), 10% replacement of soybean meal protein (T2), and 20% replacement (T3). Goats were fed pangola hay ad libitum and concentrate according to milk yield (1:2). Total dry matter, organic matter, crude protein, and fiber intake were not affected by dietary treatments (p > 0.05). However, crude protein digestibility decreased from 68.83% in the control group to 52.72% and 51.21% in the CNRR treatments (p < 0.05). Rumen pH and total volatile fatty acids remained within normal physiological ranges, suggesting stable rumen fermentation. Blood parameters, including packed cell volume, glucose, and blood urea nitrogen, were not influenced by CNRR supplementation (p > 0.05). Economic analysis showed reduced feed cost with increasing CNRR inclusion. In conclusion, CNRR can replace soybean meal protein at rates of up to 20% without affecting feed intake, ruminal pH, or measured blood metabolites; however, crude protein digestibility was reduced, indicating that dietary formulation may require adjustment. Full article

There is growing concern that antimicrobial use (AMU) in livestock may contribute to antimicrobial resistance (AMR) in humans and lead to the consumption of animal-derived foods contaminated with antimicrobial residues. As stakeholders in the livestock industry, farmers must participate in the joint effort to reduce AMU. This cross-sectional study, based on a survey questionnaire, was conducted to evaluate the biosafety measures implemented on small ruminant farms and to assess the knowledge, attitudes and practices (KAP) of small ruminant farmers regarding AMU, AMR and residues. The mean biosafety score obtained was 8.4 points on a 0–17 scale. Some biosafety measures appeared difficult to implement, namely vehicle disinfection, requiring visitors to change clothing and footwear at the farm entrance, cleaning and disinfecting farm facilities, using high-pressure washing equipment, and requiring employees to change clothing and footwear upon entering the farm. Although farmers self-reported moderate levels of knowledge (4.9 points on a 0–7 scale) and positive attitudes (5.8 points on a 0–7 scale), significant gaps in knowledge about antibiotics and antimicrobial stewardship persisted. Practices received lower scores (4.7 on a 0–7 scale), especially regarding medication recording, leftover antibiotic management, and waste disposal. Cluster analysis identified distinct farmer profiles with different patterns of knowledge and practices. These findings underscore the importance of considering farmer heterogeneity when designing interventions aimed at improving AMU. Full article

The objective of this study was to evaluate the productive performance, ruminal fermentation, in vivo digestibility, carcass yield, and physicochemical variables of meat when bovine rumen content (BRC) was included in the diet of lambs. Thirty-six Pelibuey-Dorper crossbred lambs of both sexes, with an average weight of 19.5 ± 1.5 kg, were used in a generalized randomized block design with the sex of the lambs as a blocking factor with four treatments: BRC₀, BRC₁₅, BRC₃₀, and BRC₄₅, corresponding to 0%, 15%, 30%, and 45% BRC inclusion in the diet, respectively. The results indicate that the dietary effect was not significant for any of the evaluated variables, whereas sex showed significant differences in final body weight, average daily gain, dry matter intake, and hot and cold carcass yield. Although specific treatment-sex combinations significantly influenced productive performance variables such as average daily gain, dry matter intake and ruminal fermentation parameters, such as propionic acid, there is no consistent evidence that the inclusion of bovine rumen content promotes superior productive performance or carcass quality in fattening lambs. Full article

Several studies have shown that supplementation with 100 to 130 mg of 3-nitrooxypropanol (3-NOP)/kg diet acts as a mitigating factor of enteric CH₄ production in ruminants. From an energy perspective, this effect could indicate improved feed energy utilization. Feed additives that reduce the acetate-to-propionate molar ratio and/or CH₄ production generally increase the efficiency of feed energy utilization and can alleviate the negative impact of high ambient heat loads on ruminant productivity. In seeking to test this assumption, the impact of supplementing 3-NOP in growing–finishing diets was evaluated in 24 intact male lambs (31.92 ± 3.77 kg). The experiment lasted 61 days. Treatments consisted of supplementing a total mixed growing–finishing diet (30:70 forage-to-concentrate ratio) with zero or 115 mg 3-NOP/kg diet. Lambs were assigned to 12 pens (two lambs/pen, six replicates per treatment). The temperature–humidity index (THI) during the experiment averaged 83.37 ± 6.4. The inclusion of 3-NOP tended to increase final weight (2.6%, p = 0.06) but increased dry matter intake by 10.6% (p = 0.03), thus decreasing the efficiency of dietary net energy utilization by 2.3% and 3%, respectively (p = 0.04). Lambs fed with 3-NOP showed greater (6.2%, p = 0.04) carcass weight and dressing percentage (3.3%, p = 0.03) without effects on the tissue shoulder composition. Supplemented lambs showed lower gastrointestinal (GIT) fill (9.3%, p = 0.02) and greater (1.3%) empty body weight (EBW, p < 0.01). Visceral organ mass (expressed as g/kg EBW) was not affected by 3-NOP supplementation. It was concluded that supplemental 3-NOP did not improve feed efficiency nor the efficiency of dietary energy utilization, but did improve carcass weight and dressing percentage in lambs fattened under high ambient heat load. The greater carcass weight observed in the present experiment was due mainly to a tendency for a greater final weight (p = 0.06) for 3-NOP lambs, whereas the improvement in dressing percentage was due mainly to a lower (p = 0.02) GIT fill. It is crucial to highlight that this is a pioneering study on the effect of 3-NOP on the productive efficiency of lambs subjected to high ambient heat loads. It is also important to note that enteric methane production was not measured in this experiment. Although the doses used in this experiment have consistently reduced methane production in several studies conducted under favorable climatic conditions, we cannot precisely determine the role of CH₄ production in the dietary net energy efficiency observed in lambs that received 3-NOP. The results presented here provide a basis for future research evaluating the anti-methanogenic and productive responses to the use of 3-NOP under high ambient temperature conditions. Full article

The Hippo pathway effector Yes-associated protein (YAP), acting through TEA domain (TEAD) transcription factors, regulates transcriptional programs in ovarian tissues; however, its role in interferon tau (IFNT) signaling within bovine luteal cells has not been investigated. This study aimed to determine whether YAP-TEAD interaction is required for IFNT-induced interferon-stimulated gene (ISG) expression in primary bovine luteal cells and to perform an exploratory assessment of selected receptor genes (ITGB1, GRP78, VEGFR2). Primary luteal cells were treated with recombinant ovine IFNT (roIFNT; 1 ng/mL) in the presence or absence of verteporfin (VP; 0.1, 0.5, or 1.0 µM), a pharmacological YAP-TEAD inhibitor, and mRNA expression was quantified by RT-qPCR. VP dose-dependently suppressed YAP target genes (YAP1, CTGF, ANKRD1) and reduced roIFNT-induced expression of MX1, MX2, and OAS1, whereas ISG15 was unaffected. Steroidogenic gene expression (3β-HSD, P450scc, StAR) remained unchanged across treatments, indicating preserved cell viability. Among the exploratory receptor endpoints, VP decreased ITGB1 and increased GRP78 at the highest concentration, while VEGFR2 was unaffected. These findings indicate that YAP-TEAD activity contributes to IFNT-induced ISG responsiveness in bovine luteal cells, with preliminary evidence of effects on integrin-mediated signaling pathways. Full article

Milk production in tropical smallholder systems is constrained by limited high-quality roughage during the hot–dry season. Sweet sorghum silage is drought-tolerant and may replace corn stover silage. Twelve Holstein–Friesian crossbred cows were assigned to the same commercial concentrate plus either corn stover silage or sweet sorghum silage as the primary roughage source (n = 6 per diet). Intake, apparent digestibility, milk yield and composition, and feed-use efficiency were evaluated on day 15 and 30 and analyzed using linear mixed-effects models with cow as a random effect. Compared with corn stover silage, sweet sorghum silage increased dry matter intake (p < 0.05) and improved the digestibility of fibre fractions, including crude fibre, NDF and ADF (p ≤ 0.003), while crude protein- and nitrogen-free extract digestibility were not different (p > 0.05). Milk yield, 4% fat-corrected milk, energy-corrected milk, and feed-use efficiency indices were unaffected by silage source (p > 0.05). Milk protein concentration was higher with sweet sorghum silage (treatment effect p < 0.05), whereas milk fat and lactose were unchanged. Sweet sorghum silage can therefore replace corn stover silage in tropical dairy diets, improving intake and fibre utilization without compromising milk output. Full article

Environmental temperature-induced metabolic changes in dams can be reflected by alterations in metabolomic and fatty acid profiles in colostrum. The colostrum from 13 Black Bengal (BB) dams was collected on the day of parturition at two consecutive parities during the hot conditions (HCs) of summer or rainy seasons and the cold conditions (CCs) of winter. The metabolomic and fatty acid profiles were analyzed using nuclear magnetic resonance (NMR) and gas chromatography–mass spectrometry, respectively. The results showed significantly higher sarcosine, tyrosine, citrate, succinate, galactose, acetylglucosamine, carnitine, choline, glycerophosphocholine, and trimethylamine N-oxide during CCs than HCs; potential discriminant metabolites according to VIP scores were sarcosine, succinate, and choline. Colostrum from CCs had significantly lower levels of saturated fatty acids (SFAs), including butyric acid (C4:0), myristic acid (C14:0), and pentadecanoic acid (C15:0), but higher omega-9 monounsaturated fatty acids (MUFAs), especially oleic acid (C18:1n9c), elaidic acid (C18:1n9t), and eicosenoic acid (C20:1n9), than in HC. Linoleic acid (C18:2n6c) and the omega 6/omega 3 PUFA ratio were higher during CCs than HCs. It is concluded that a metabolic shift for nutrient utilization occurs, from glucose during HCs toward fat during CCs, which may not be due to the diet but rather neurohumoral alterations occurring during temperature adaptation. Full article

This study evaluated the effects of including palm kernel oil in the diets of pasture-raised sheep on carcass characteristics, meat quality, and fatty acid profiles. A completely randomized design with four treatments was used, consisting of 0, 20, 40, and 60 g/kg of palm kernel oil in the dry matter of the supplement, with eight replicates. Thirty-two uncastrated Santa Inês sheep, with an average initial body weight of 23.2 ± 2.6 kg, were used in this study. The animals were kept on Aruana grass (Panicum maximum (syn. Megathyrsus maximum) cv. Aruana) pastures under continuous stocking for 59 days (preceded by 15 days of adaptation), with each one fed supplements (1.4% of body weight) at 8 am. At the end of the experimental period, the animals were slaughtered in a commercial slaughterhouse for carcass and meat quality evaluation. The inclusion of palm kernel oil had a decreasing linear effect on hot and cold carcass weight (p = 0.0403) (p = 0.0398), but it did not affect hot or cold carcass yields or carcass morphometric measurements, commercial cut weights, pH, or loin area (p > 0.05). However, it affected the color of the L. lumborum muscle, showing an increasing linear effect on yellow intensity (b*) (p = 0.002) and on the centesimal composition, with an increasing linear effect on ether extract content (p = 0.006). Shear force, cooking loss, and water-holding capacity were not affected (p > 0.05). Fatty acid profiles, the atherogenicity and thrombogenicity indices, and the ratio of hypocholesterolemic to hypercholesterolemic fatty acids (h:H) were also unaffected by the inclusion of palm kernel oil (p > 0.05). The inclusion of up to 60 g/kg of palm kernel oil in the diets of pasture-raised sheep had an effect on carcass weight but not yield. It also had an effect on the color and chemical composition of L. lumborum muscle, but these changes did not compromise the overall quality of the meat. Full article

MYO16 has previously been identified as a candidate gene in studies of meat productivity in sheep, but its complete sequence and the potential impact of polymorphisms on the functional properties of the gene in sheep remain understudied. The aim of this study was to analyze genetic variation in the MYO16 gene region in sheep and to identify polymorphisms that, according to bioinformatic prediction, are capable of changing the amino acid sequence of the protein or are associated with allele-specific differences in transcription factor binding motifs potentially significant for gene regulation or protein structure. Whole-genome sequencing was performed for genomic DNA from Manych Merino rams (n = 30) on an Illumina NovaSeq 6000 platform. Variants within the MYO16 region were extracted and annotated. For each variant, ±30 bp reference and alternative sequences were scanned with FIMO using the JASPAR 2020 Vertebrates PWMs to detect allele-specific gain or loss of significant motif hits. TFLink (Mus musculus) was used to retain only TFs with MYO16 listed as a target. In the MYO16 gene region, 10,318 variants were detected. The coding region contained 54 SNPs, including 15 missense variants. In silico TFBS scanning identified 23 variants showing allele-specific gain or loss of significant motif hits, involving motifs for EBF1, CTCF, NRF1, SPI1, NFE2L2, JUN, and GFI1. We examined polymorphism in the ovine MYO16 gene region and identified candidate variants to be tested for association with productivity traits in future genotype–phenotype studies. Full article

This study evaluated the effects of forage-free diets with reduced starch levels on the productive performance, metabolism, ruminal fermentation, nutrient digestibility, and meat quality of feedlot beef cattle. Two experiments were conducted. In Experiment 1, forty uncastrated Nellore steers were distributed into 20 pens in a completely randomized design, receiving diets with increasing inclusion levels of ground corn in the total diet: C400 (400 g kg⁻¹), C200 (200 g kg⁻¹), C100 (100 g kg⁻¹), and C50 (50 g kg⁻¹), formulated without forage and based on fibrous co-products. Increasing ground corn inclusion promoted linear improvements in final body weight and average daily gain, while dry matter intake and feed efficiency showed quadratic responses. Meat quality parameters were not affected by dietary treatments. In Experiment 2, eight crossbred steers were assigned to a double 4 × 4 Latin square design and fed the same experimental diets. Higher corn inclusion increased starch and fat intake, whereas dry matter, organic matter, and protein intake showed quadratic responses. Apparent total-tract digestibility of dry matter, organic matter, and starch also followed a quadratic pattern. Ruminal fermentation parameters were affected by dietary treatments, with greater ammoniacal nitrogen concentrations at higher corn levels and quadratic responses for propionate, butyrate, and methane production. Nitrogen metabolism indicated increased urinary nitrogen and uric acid excretion with increasing dietary corn inclusion. These results demonstrate that forage-free diets based on citrus pulp and soybean hulls with different levels of ground corn can be effectively used in finishing beef cattle, improving performance without impairing meat quality while modulating ruminal fermentation and nutrient utilization. Full article

The objective of this study was to evaluate the effects of zilpaterol hydrochloride supplementation strategies on growth performance, dietary energetics, carcass traits, and meat quality in feedlot finishing lambs. Twenty-four Dorper × Katahdin crossbred male lambs (45.5 ± 4.53 kg, mean ± SD) were used in a 27 d feeding trial. The zilpaterol supplementation strategies were: (1) control, no zilpaterol supplementation (CON); (2) zilpaterol administered once daily as a full dose in the morning feeding (ZMOR); (3) zilpaterol incorporated into the total mixed ration and continuously available throughout the day (ZMIX); and (4) intermittent zilpaterol supplementation applied in a daily alternating pattern, one day on, one day off (ZINT). A target dose of 0.20 mg/kg live weight of zilpaterol hydrochloride per administration was used for all supplemented treatments, with daily administration in ZMOR and ZMIX and alternate-day administration in ZINT. Compared to the CON, zilpaterol supplementation through the ZMOR + ZMIX strategies improved average daily gain (ADG) and feed efficiency (FE) by 28.6% and 18.5%, respectively. Additionally, dressing percentage and longissimus thoracis muscle area increased by 3.2% and 17.0%, respectively. The ZINT strategy also enhanced ADG by 20.9% and FE by 15.4%. However, ZINT did not improve hot carcass weight or dressing percentage. All zilpaterol supplementation strategies increased meat toughness by up to 39.2%. Results indicate that both the ZMOR and ZMIX strategies optimize the response to zilpaterol, with no evidence that ZMOR supplementation results in a diminished response. Full article

Grape pomace is an agri-industrial by-product rich in fatty acids with the potential to be used in diets for goats and increase the nutraceutical properties of milk. This study aimed to investigate the effect of incorporating dehydrated grape pomace (DGP) into the diets of Saanen goats on the composition, fatty acid profile, nutritional indices of fatty acids, and antioxidant capacity of their milk. Eight multiparous Saanen goats, averaging approximately four years of age and weighing 41.2 ± 15.7 kg, were used in a double Latin square (4 × 4) design. Diets were formulated with increasing levels of grape pomace (0, 90, 150, and 210 g/kg Dry Matter—DM), replacing cactus. The data underwent analysis of variance using GLM procedure and regression analysis (both linear and quadratic) using REG procedure at a significant level of 5%. The concentration of C18:2 n-6 cis and C18:3 n-3 increased (+20.1 and +15.5%, respectively) with the grape pomace inclusion. There was a reduction in the atherogenic (−24.0%) and thrombogenic (−9.9%) indices of goat milk with the increase in DGP levels. There was a reduction in de novo fatty acids (−10.5%), Δ⁻⁹ desaturase of C14 (−21.8%) and C18 (−9.5%) indexes with the highest level of DGP. There was a quadratic effect for Ferric Reducing Antioxidant Power (FRAP) and a linear effect for phenolic compounds (PC), where the highest values were observed at the estimated levels of 160 g/kg and 210 g/kg DM, respectively. Supplementing dairy goats’ diets with dehydrated grape pomace up to 210 g/kg dry matter enhances the fatty acid profile and nutritional indices of fatty acids of Saanen goat milk without altering its basic composition. As grape production is prevalent in low rainfall regions, pomace may provide an alternative feed in areas with forage production constraints. Additionally, grape residue could establish a link between the wine and dairy sectors for cheese production, expanding markets for farmers. Full article

Growth traits in goats are impacted by both genetic and non-genetic variables; as such, it is critical to separate direct and maternal effects for reliable genetic assessment. This study determined the phenotypic and genetic characteristics for birth weight (BW), weaning weight (WW), and average daily gain (ADG) in Salem Black goats. The MTDFREML software was used to evaluate data from 930 kids, the progeny of 147 bucks and 804 does, gathered between 2004 and 2019. Three models were compared: Model 1 (direct genetic effects only), Model 2 (adding permanent environmental effects), and Model 3 (adding maternal genetic effects and direct–maternal covariance). The overall mean was 2.21 kg for BW, 9.23 kg for WW, and 78.27 g/day for ADG. The direct heritability estimates for BW, WW, and ADG were 0.06–0.22, 0.13–0.40, and 0.11–0.16 across models, respectively, whereas maternal heritability ranged from 0.01 to 0.13. The study revealed maternal genetic effects on birth weight but their total contribution to growth trait variation is modest, and model parsimony suggests that maternal effects on WW and ADG be excluded. Breeding programs should therefore prioritize direct selection for growth performance, whereas management strategies such as enhanced nutrition, targeted kidding, and support for first-parity do provide more rapid and effective avenues to improve pre-weaning developmental outcomes. Hence, a pragmatic approach that combines direct genetic selection and environmental optimization would result in greater genetic gain and support long-term meat production in Salem Black goats. Full article

A multitude of factors affect the optimum calving season, requiring site-specific systems analysis. The objective of this study was to determine the effects of the calving season (S1 and S2) and the timing of calving within the season on production parameters and economics in southwest Missouri. A five-year study was conducted from 2014 to 2018 using field data recorded for 1979 Hereford cow–calf pairs. Cows were categorized by calving season and 21 d calving periods within season (Periods 1–5) in which they calved. Data were analyzed under a completely randomized design with effects of season, period, calf sex, and two and three-way interactions with the calving year as a random effect. The Cattle Value Discovery System (CVDS) beef cow model was used to estimate required cow feed and feed intake. Historical cattle market prices were used, along with total feed costs, to calculate net returns. Calving in later periods reduced the pregnancy percentage in S1 but not S2. Cows calving earlier in both seasons weaned heavier calves. Feed costs were greater in S2, but replacement heifer costs were greater in S1, especially in later calving periods. Overall, net returns were not different between S1 and S2 cows, but net returns declined in later calving periods in S1, whereas there was no difference in S2. In conclusion, at the latitude of southwest Missouri for a forage species with a bimodal growth curve, the calving period affected cow productivity and profitability in Season 1 but less so in Season 2 cows, with no difference in profitability between calving seasons. Full article

This study evaluated the effects of four macroalgae (Colaconema spp., Ulva intestinalis, Ceramium spp., Pylaiella litoralis) and two microalgae (Haematococcus pluvialis, Porphyridium purpureum), chosen due to their local cultivability in the southern Baltic Sea region and potential gas-reducing properties reported for their taxa, on rumen fermentation and methane production. Therefore, the in vitro ANKOM Rf gas production system was used; three trials were conducted and gas kinetics, gas composition after 48 h of incubation, and short-chain fatty acids (SCFAs) were analyzed. For Trial 1.1, the algae biomasses were added at 4% to a conventional dairy diet and incubated in buffered rumen fluid for 48 h, to evaluate their potential as a supplement. In Trial 1.2, the polysaccharide-enriched algae extracts were added at 2% to the base diet using the same procedure, to investigate the role of the polysaccharide content. For Trial 2, the macroalgae biomasses were evaluated solely to assess their fermentation potential. The addition of the red alga Colaconema spp. (Colaconema) altered the SCFA profile with a shift towards propionate (rate of change in propionate concentration, ΔC3 = 1.216; p < 0.001), without compromising total SCFA yield. The same could be assessed for Ulva intestinalis (U. intestinalis), limited to Trial 2 (ΔC3 = 0.516; p < 0.001). The addition of U. intestinalis led to reduced initial gas production (p = 0.003), reaching the maximum gas production rate at 5.8 h of incubation, 0.3–0.7 h later than the others (5.1–5.5 h). While there was no significant methane reduction at the chosen inclusion rates, the results indicate that both algae influence the SCFA profile and therefore fermentation pattern, with U. intestinalis warranting further investigation on gas production dynamics. Full article

The objective of this study was to evaluate the impact of summer calving on reproductive performance, milk yield, and culling risk in U.S. organic dairy herds. Data were obtained from the Dairy Herd Improvement records of 434 organic dairy herds across 31 states, comprising 287,927 calving records from 2018 to 2022. Calving months were categorized as winter, spring, summer, or fall. Mixed models were used to analyze the 305 d milk yield, 305 d energy-corrected milk yield, peak milk DIM, peak test-day milk yield and logistic regression, and survival analyseswere applied to analyze calving difficulty, abortion, pregnancy diagnosis, and culling outcomes. Cows calving during summer had fewer days to first service and fewer days open compared with cows calving in other seasons; however, their odds of being diagnosed as pregnant were significantly lower. Summer-calving cows produced lower 305 d milk and energy-corrected milk yields, reached peak milk production later, and had a lower peak test-day milk yield. Calving during summer was also associated with increased odds of calving difficulty and a higher risk of culling. These findings indicate that summer calving poses distinct challenges for organic dairy cows, with cumulative effects on fertility, milk production, and survivability, underscoring the need for season-specific management strategies in organic dairy systems. Full article

Lactation is a dynamic process characterised by a production peak at 6–8 weeks, followed by a steady decline. To understand the molecular drivers of these phases and the influence of production systems, this study aims to provide a transcriptomic characterisation of bovine milk somatic cells (BMSCs) in Holstein (HO), Simmental (SM), Simmental × Holstein crossbreed (SM × HO), and Podolica (POD) cows at 60 and 120 days in milk (DIM). Total RNA was sequenced at high coverage, and differential expression and functional enrichment analyses were performed. While a core set of milk protein and fatty acid genes was identified, breed-specific analysis showed SM × HO had the highest variation (677 differentially expressed genes, DEGs). Genes upregulated at 120 DIM involved mitochondrial metabolism and oxidative phosphorylation, while downregulated genes were associated with nuclear transcriptional regulation. At 60 DIM, SM × HO vs. HO showed 66 DEGs, with upregulated genes linked to chromatin remodelling and immune regulation. Comparing production systems, 28 DEGs between POD and HO/SM highlighted differences in mitochondrial activity and transcriptional regulation. This study bridges a knowledge gap by profiling the milk transcriptome of unexplored cattle breeds, providing novel insights into the molecular regulation of lactation. Full article