Management and production characteristics impact conception rate to first service (CR1S) in small-scale dairy farms, but the impact of body condition score (BCS) and milk production levels on cows’ fertility is unknown. Our objective is to determine the effect of BCS and milk production on CR1S in small-scale dairy farms of western Mexico. Logistic regression models are used to determine the effect of BCS (at calving and first service), 60-d and 305-d milk production, protein and fat production, lactation number, and days at first service on CR1S. BCS at calving does not affect CR1S in cows with three or more lactations (39.5%; p > 0.1). However, first-lactation cows with BCS < 3.0 at calving and second lactation cows with BCS ≤ 2.5 at calving have higher CR1S (63.2 and 67.9%, respectively; p < 0.1). This result is perhaps due to reduced milk production, which leads to lower metabolic stress. BCS ≤ 2.5 at calving is associated (p < 0.05) with a reduced milk yield, explaining partially the observed higher CR1S in these groups. Cows with BCS ≤ 2.5 at first service in the higher quartile of 60-d milk production (≥ 28kg/day) show lower CR1S (23.9 and 51.1%, respectively; p < 0.01). In conclusion, BCS at calving and at first service, 60-d milk production, and lactation number are factors associated with CR1S.

The impact of assisted calving, retained fetal membranes (RFM) and calf sex on milk production in small-scale dairy systems remains unknown. This study evaluated their impact on early lactation milk production and standardized 305-day yield (305MY) using 279 lactation records from 23 farms over 18 months. Variables analyzed included assisted calving, RFM, calf sex, and lactation number, with milk production at 30 days and 305MY as response variables. General Linear Models were used for statistical analysis, with significance at P < 0.05, and trends at P < 0.1. Lactation number significantly affected early lactation milk production (P = 0.023), with RFM showing a trend toward significance (P = 0.078). Cows without RFM produced 21.8 ± 0.8 kg/day, while those with RFM produced 18.6 ± 1.7 kg/day. Assisted calving significantly affected 305MY (P < 0.05), with cows not requiring assistance having higher yields compared to those needing assistance. Interactions between assisted calving and lactation number (P = 0.099), as well as RFM and calf sex (P = 0.060), approached significance. In cows that did not require assisted calving, no significant differences in 305MY were found based on lactation number (P ≥ 0.05). However, in cows that required assisted calving, significant differences in 305MY (P < 0.05) were observed between first and third or higher lactations, with second-lactation cows having average values. Additionally, cows without RFM that gave birth to female calves had higher 305MY compared to cows with RFM or those that gave birth to male calves with RFM or without RFM. In conclusion, RFM reduces early lactation milk production by approximately 3.2 kg/day, and assisted calving impacts 305MY by about 1,069 kg/lactation.

El objetivo fue evaluar el impacto de factores asociados al manejo de la madre y la calidad del calostro sobre la crianza de reemplazos bovinos durante la lactancia, en el sistema de producción de leche a pequeña escala. En 13 unidades de producción se obtuvo información del crecimiento corporal, la alimentación con calostro e información asociada a la madre de 220 becerras Holstein. Las variables de interés fueron: morbilidad, concentración de inmunoglobulinas en el calostro (CIC; <110 mg/ml), concentración de proteína sérica (CPS; <6.6 g/dl), ganancia diaria de peso (GDP; <0.650 kg/día) y ganancia diaria de altura (GDA; <0.222 cm/día). Los factores de estudio fueron: peso corporal al nacimiento (PCN; <42 kg), altura al nacimiento (AN; <82 cm), calostro consumido el primer día (CCPD; <4 l), calostro consumido el primer día/kg de PV (CPDPV), condición corporal al parto (CCP; 68 días), vacas primíparas (VP) y vacas sin dieta de reto (VSDR). Para determinar el impacto de los factores de estudio sobre los eventos de interés, se obtuvo la razón de momios a partir de análisis de regresión logística múltiple. Los factores identificados para morbilidad fueron CCPD y VP (P<0.1). Los factores para CIC fueron la DPS y VSDR (P<0.1), mientras que para la GDP lo fue VSDR (P<0.1). Finalmente, los factores para GDA fueron VSDR, PCN, AN y CPDPV (P<0.1). Estos resultados sugieren que la nutrición de la madre durante la gestación tardía tiene un impacto importante sobre la salud y el desarrollo corporal de las becerras durante la lactancia. Estudios adicionales deberán determinar los efectos a largo plazo.

El objetivo fue determinar si una solución salina ozonizada (SSO3) incrementa los neutrófilos polimorfonucleares (NPMN) endometriales (Exp 1) y desafiar el efecto preventivo de SSO3 sobre la endometritis subclínica (ESC) (Exp 2). En el Exp 1 se utilizaron 38 vacas Holstein primíparas. Se incluyeron vacas con (CAM) y sin antecedentes de metritis postparto (SAM); posteriormente se repartieron en subgrupos control (CTRL, solución salina) o SSO3 (6.7 ± 0.3 ppm). A los 55 días postparto se aplicó 50 ml de CTRL o SSO3 intrauterinamente y a las 48 h se registró la cantidad de NPMN por citología endometrial. En el Exp 2 se utilizaron 26 vacas Holstein primíparas SAM. Las vacas se repartieron aleatoriamente en CTRL o SSO3. Se administraron dos dosis de 50 ml con intervalo de 7 días (primera aplicación 11.3 ± 0.4 días postparto). Al día 30 postparto se diagnosticó ESC (≥6% NPMN). Las vacas CAM tuvieron mayor número de NPMN endometriales comparado con vacas SAM (13.9 ± 6.2 vs 1.0±0.46, P<0.05). El grupo CAM-CTRL presentó mayor número de NPMN que el SAM-CTRL (17.0 ± 9.6 vs 0.1 ± 0.1, P0.05) y SAM-CTRL y SAM-SSO3 (0.1 ± 0.1 y 1.8 ± 4.8, P>0.05) no fueron diferentes. Se observó una tendencia estadística (P=0.09) de menor porcentaje de ESC en grupo CTRL comparado con SSO3 (15.4 y 46.2 %, respectivamente). En conclusión, la SSO3 por vía transcervical no incrementa el número de NPMN endometriales y el tratamiento preventivo con SSO3 aplicado a vacas SAM no disminuyó la ESC. Los resultados sugieren un posible efecto antiinflamatorio del tratamiento solución salina ionizada.

Modeling lactation curves with mathematical equations is useful to describe and predict the productivity of dairy cows. However, studies analyzing the performance of different models to describe lactation curves in small-scale dairy systems are sparse. Therefore, the objective of this study was to evaluate the capacity of five models to describe lactation curves of cows in a small-scale dairy system. Monthly milk weighins from 936 lactations were conducted in 23 farms in western Mexico. The Bayesian information criterion (BIC) and mean square prediction error (MSPE) were used to assess the fit of the models to the observed data, and the root mean square prediction error as a percentage of the observed mean (%RMSPE) was used to evaluate the accuracy of the models. The Gaines model had the best fit (lowest BIC and MSPE) for the first, second, and third or higher lactations. Regarding accuracy, the Sikka and Gaines models had the lowest RMSPE and %RMSPE. When classified by production level, the Gaines model had the best fit. The Gaines and Sikka models had the best accuracy across all three production levels. It was concluded that the Gaines model is the best option for representing lactation curves in a small-scale milk production system.