Ketogenesis is a secondary metabolic pathway to provide energy to dairy cows during early lactation; however when the production of ketone bodies (acetoacetate, acetone, ß- hydroxybutyrate) is above certain levels a subclinical disorder may appear. The aim of the present study was to investigate the association between serum concentrations of ß- hydroxybutyrate (BHBA) and fatty acid (FA) profile of milk with emphasis in conjugated linoleic acid (CLA) in a population of early lactation Holstein cows. Fifty cows between parity 1 and 5, ranging from 14 to 21 days in milk, were randomly selected from 3 farms of the central area of Chile for determination of serum BHBA concentrations, milk fat content, and milk FA profiles. Cows were divided in low (n = 26) and high (n = 24) BHBA groups considering the median value of the serum concentration of BHBA (0.7 mmol/L) (SEM = 0.094). Mean milk fat % was 3.45 % and 3.60 % for cows in the low and high BHBA groups, respectively (P = 0.15). Concentrations of several FA were significantly different between both groups. Specifically, mean CLA concentrations were 0.40 % (4 ± 0.03 g/kg) and 0.33 % (3.3 ± 0.03 g/kg) for the low and high BHBA groups, respectively (P = 0.05). It is concluded that early postpartum cows with serum BHBA > 0.7 mmol/L tended to have higher milk fat % and had significantly lower concentrations of CLA than early postpartum cows with BHBA ≤ 0.7 mmol/L.

El objetivo de este estudio fue determinar la relación entre ácidos grasos no esterificados (AGNE) al parto, reservas corporales (CC) y producción de leche en vacas Holstein en Chile central. Este estudio se realizó en dos rebaños lecheros comerciales con una producción promedio de leche de 8000 kg por lactación. Las vacas fueron alimentadas con ración completa basada en heno de alfalfa (heno y cortada en verde), ensilaje de maíz y concentrado comercial. Se obtuvieron muestras de sangre de 350 vacas al momento del parto para la determinación de AGNE. Se determinó CC al parto y a los 60 días posparto y producción de leche acumulada a los 30, 60 y 100 días. Los datos fueron analizados utilizando el procedimiento de modelos mixtos de SAS (2003). Los valores promedio de AGNE al parto y la CC fueron de 0,90 ± 0,47 meq/l y 3,6 ± 0,3, respectivamente. Considerando la CC al parto y el número de partos como variables independientes en un modelo multivariado, la relación entre los AGNE al parto y la producción de leche a los 100 días de lactación fue de tipo cuadrática, es decir, para valores tanto bajos como altos de AGNE, la producción acumulada fue menor en comparación a niveles intermedios (R²= 0,27; p<0,001). Se observó una correlación positiva entre CC y AGNE al parto (r= 0,26; p<0,05). Se determinó una tendencia a que en la medida que los valores de AGNE son mayores, el cambio en la CC es mayor. Se concluye que los AGNE al parto se asocian en forma cuadrática con la producción de leche acumulada a los 100 días.

The objective of this study was to investigate the effect of a fine needle liver biopsy (FNB) on the behavior and milk production of postpartum dairy cows during and after the procedure. In Experiment 1, cows at 10 ± 1.1 days in milk were assigned to receive either a FNB (n = 26), involving collection of a liver sample using an 18G spinal needle under local anesthesia, or a sham procedure (n = 26). Behavioral responses during the procedure, such as vocalizations, kicking, and abrupt movements, were recorded and analyzed by a trained observer. In Experiment 2, a separate group of cows (n = 48), also at 10 ± 1.1 days in milk, underwent a FNB, and their daily lying behavior, rumination, and milk yield were monitored using automated sensors over three consecutive days: the day before (day -1, baseline), the day of (day 0), and the day after the procedure (day +1). No significant differences were observed in the behavioral responses between cows that received FNB and those that underwent the sham procedure. Post-procedure, daily lying time, rumination time, and milk yield remained stable compared to baseline values. On day +1, an increase in the number of lying bouts and a decrease in bout duration were noted. The results of this study indicate that liver FNB has little immediate or short-term effect on behavior or milk production, suggesting that it is a minimally painful procedure, supporting its suitability for clinical and research applications.

The aim of this study was to evaluate the relationship between cows’ hepatic lipid content (HLC) at 10 days in milk (DIM) and their metabolic status, health, and production during transition and early lactation periods. HLC was determined in 103 cows from a grazing Chilean dairy herd via cytologic examination of the liver through fine needle biopsies, categorized as mild, moderate, or severe. Blood metabolites were evaluated in the transition period, together with diseases in the postpartum period and milk production during the first 90 DIM. In pre-partum and postpartum periods, primiparous cows with severe HLC showed higher plasma cholesterol than multiparous cows with mild HLC. Postpartum, cows with severe HLC had higher serum non-esterified fatty acids (NEFAs) and NEFA/cholesterol ratios than those with mild HLC. Similarly, cows with moderate and severe HLC presented higher plasma β-hydroxybutyrate and greater risk of subclinical ketosis than cows with mild HLC. Additionally, cows with severe HLC had higher milk production and lower milk protein content than those with mild HLC. These results indicate that moderate to severe HLC at 10 DIM was associated with negative energy balance and subclinical ketosis, whereas severe HLC was associated with increased milk production and decreased milk protein content.