John Montoya-Zuluaga

The bovine cervix undergoes endocrine-dependent physiological changes that may influence local immune activity and complicate the interpretation of cervical inflammation. This study evaluated the relationships among macroscopic cervical appearance, cervical neutrophil infiltration, reproductive stage, and endometrial inflammation in postpartum grazing dairy cows. Non-pregnant lactating Holstein × Jersey crossbred cows (n = 80) ≥ 45 days in milk underwent reproductive examination, cervical video-endoscopy, ultrasonography, cervical and endometrial cytology, and serum progesterone determination. Macroscopic cervical appearance was classified as C0, C1, or C2, whereas cervical polymorphonuclear neutrophil (PMN) percentage was analyzed as the primary proportional outcome using adjusted fractional logistic regression. A ≥5% cervical PMN threshold was used operationally for secondary analyses. C0, C1, and C2 occurred in 30.0%, 50.0%, and 20.0% of cows, respectively, and 20.0% had cervical PMN ≥ 5%. Macroscopic cervical appearance was not associated with cervical PMN percentage (p = 0.931) or cervical PMN ≥ 5% (p = 1.000). Cervical PMN percentage was higher in follicular-stage than in luteal-stage cows (p < 0.001). This association persisted after adjustment for parity and cytological endometritis using fractional logistic regression (β = 2.42; 95% CI, 0.81–4.03; p = 0.003), with an adjusted marginal difference of 10.48 percentage points (95% CI, 1.42–19.54; p = 0.023). A complementary two-part analysis supported this association, showing higher odds of detectable cervical PMNs (OR = 4.71; 95% CI, 1.73–12.82; p = 0.002) and higher mean PMN proportions among positive observations (mean ratio = 4.11; 95% CI, 1.40–12.06; p = 0.010) during the follicular stage. In secondary Firth penalized logistic regression, follicular stage remained associated with cervical PMN ≥ 5% (aOR = 5.38; 95% CI, 1.39–20.83; p = 0.015). Cervical and endometrial PMN percentages were weakly positively correlated (ρ = 0.240; p = 0.033), while agreement between cervical PMN ≥ 5% and cytological endometritis was limited (κ = 0.258). Neither cervical neutrophil infiltration nor cytological endometritis was associated with subsequent pregnancy, whereas serum progesterone concentration showed a positive exploratory association with pregnancy. Cervical neutrophil infiltration is associated with reproductive stage independently of parity and cytological endometritis, without relying on an unvalidated diagnostic threshold. Cervical cytology should therefore be interpreted within the reproductive and physiological context of the cow.

Musical exposure in dairy cattle has been associated with potential effects on milk production, behavior, and physiological regulation; however, available evidence remains heterogeneous and potentially affected by biological and environmental confounding. In high-tropical grazing systems, these responses are simultaneously influenced by stress physiology, disease, nutrition, management, climatic variability, and individual adaptation. This review integrated causal inference and graphical epidemiology to develop biologically grounded directed acyclic graphs (DAGs) representing hypothesized causal pathways between musical exposure and milk production, behavior, and heart rate variability (HRV). An analytical narrative synthesis of physiological, ethological, autonomic, and epidemiological evidence was conducted, and three independent DAGs were constructed using DAGitty version 3.1. Variables were classified according to their epidemiological roles. The production DAG identified stress as a major integrative node linking disease, nutrition, reproductive physiology, management, and milk yield. The behavioral DAG highlighted the roles of ecological organization, resource access, social interaction, and environmental instability. The HRV DAG treated HRV as beat-to-beat variation in cardiac intervals that provides a non-invasive index of autonomic nervous system (ANS) modulation, including sympathetic and parasympathetic influences, and indicated that responses may occur through indirect modulation of stress physiology and vagal activity. We conclude that musical interventions should be interpreted as context-dependent sensory exposures rather than isolated causal determinants; the proposed DAGs provide an explicit basis for selecting covariates, avoiding inappropriate adjustment, and designing future studies of dairy cattle welfare and production.

Dual-purpose livestock farming in the Colombian low tropics faces nutritional limitations that affect productivity and increase enteric methane (CH₄) emissions. Therefore, it is necessary to evaluate supplementation strategies that optimize the use of nutrients and reduce environmental impacts. The objective of this study was to evaluate the effects of three types of dietary supplementation—mineralized salt (MS), proteinized salt (PS), and concentrated feed (CO)—on milk production, efficiency in the deposition of dairy nutrients, and enteric CH₄ emissions in dual-purpose grazing cows in the Colombian Amazon. Twenty-four F1 Holstein × Gyr cows were used in a completely randomized block design. Nutrient intake, digestibility, composition, and efficiency in the milk deposition of Ca, P, K, and N were measured; additionally, CH₄ emissions were assessed using a portable electronic spirometry mask. The results indicated that the treatments did not modify the total intake of dry matter or the production and composition of milk. CO and MS supplementation improved the efficiency of Ca and P (p < 0.03) deposition in milk, while no differences were observed for N and K. CH₄ emissions (196 ± 17.9 g/cow/day) were not affected by the supplements and were within the ranges reported for dual-purpose tropical systems. However, with the supplementation with CO was a lower losses of gross energy intake as CH₄ (Y_m) (p < 0.05). In conclusion, supplementation with the evaluated products did not impact milk production or CH₄ emissions, although with CO was lower energy losses as CH₄ and, CO and MS improved the use of Ca and P, which highlights the importance of adjusting supplementation to optimize nutritional efficiency without increasing greenhouse gas emissions.

Background and Aim: Milk contamination for human consumption is one of the biggest concerns worldwide. To prevent milk contamination, it is important to implement sustainable production practices that ensure animal health and guarantee veterinary drugs have been used properly. This study aimed to detect antibiotic residues and microbial contamination in commercially available pasteurized whole milk intended for human consumption. Materials and Methods: We conducted a cross-sectional study on all brands of pasteurized milk (n = 17) for human consumption in Medellin, Colombia, from February 30 to April 30, 2022. Six milk samples of each brand were collected every 15 days, resulting in 102 samples. IDEXX SNAPduo ST Plus test (IDEXX Laboratories Inc, Maine, USA) was used to detect cephalosporins residues to detect beta-lactam and tetracyclines. We detected mesophilic aerobic bacteria and coliforms using Chromocult Coliform Agar (Merck KGaA, Darmstadt, Germany) and Plate-Count Agar (Merck KGaA), respectively. Results: Beta-lactam residues were found in 24.4% of the brands. No tetracyclines or cephalosporins were detected. Mesophilic aerobic bacteria and coliform contamination were detected in 42.6% and 12.8% of the brands, respectively. No fecal coliform contamination was detected. Conclusion: This study demonstrated the presence of antibiotic residues and microbial contamination in commercially available pasteurized whole milk intended for human consumption in the study area, highlighting its potential public health implications. Keywords: biological contamination, cow milk, drug residues, food safety.