Ermes Ramiro Rodas–Carpio

The dry period of a dairy cow is the time between the end of one lactation (when the cow is no longer milking) and the start of the next calving and lactation. The objective of this study was to evaluate the effect of heat stress during the dry period on milk production and reproductive performance during the first 100 days of the subsequent lactation in crossbred dairy cows managed in a pasture-based herd in Santa Fe, Argentina. Ninety-five multiparous cows were classified into three groups based on their exposure to heat stress: no stress, low stress, and high stress. Cows in the no stress group produced 274 kg more milk than those in the high stress group (P < 0.05) and showed higher conception rate at first service (P < 0.05). Heat stress during the dry period negatively affected early productive and reproductive performance, emphasizing the importance of mitigating heat stress in dry cows under pasture-based systems. Highlights: Heat stress (HS) during the dry period on dairy pastured based cows reduces milk production during the first 100 days on milk. Cows without HS had a higher conception rate at first service than cows exposed to high heat stress 95 multiparous crossbred cows were classified as No stress, Low stress, or High stress according to the number of dry-period days with (Temperature-Humidity Index) THI >72. Milk yield during the first 100 days in milk (DIM) was estimated, using a third order orthogonal polynomial fitted individually for each cow.

In cattle, the transfer of passive immunity from mother to calf across the placenta is limited. Therefore, providing quality colostrum or supplementing with additives that enhance this attribute is crucial to optimise the transfer of passive immunity (TPI). The objective of the present study was to investigate the effect of capsaicin on the absorption of immunoglobulins, metabolites, and enzymes to optimise TPI in neonatal calves, and to assess its impact on selected physiological parameters. Two experimental groups were established: a control group (CON; n = 8), which received colostrum in three feedings (at 1, 12, and 20 h after calving), and a capsaicin group (CAP; n = 8) which received 40 mg of capsaicin per kilogram of body weight added to the colostrum. Birth weight (CON = 36.7 ± 1.10 kg; CAP = 36.2 ± 2.64 kg) and weight at 48 h of age (CON = 38.5 ± 1.11 kg; CAP = 38.0 ± 2.82 kg) were similar between the two experimental groups. At 48 h post-colostrum feeding, the CAP group exhibited significantly higher serum concentrations of IgG, total protein, and albumin—up to 23.4 times greater than those observed in the CON group (p < 0.001). Moreover, levels of glucose, cholesterol, and triglycerides were significantly elevated in the CAP group compared to the CON group (p < 0.05). Similarly, higher concentrations of alkaline phosphatase, aspartate aminotransferase, and alanine aminotransferase were observed in the CAP group. These findings suggest that the inclusion of 40 mg of capsaicin per kilogram of body weight in colostrum is safe and contributes positively to improving TPI in crossbred Holstein calves raised at altitudes higher than 2500 m above sea level.

Se determinó la respuesta neuro–endócrina de la donadora al reducir el número de aplicaciones de hormona folículo–estimulante (FSH) como factor de superovulación. Ocho vacas Holstein mestizas fueron distribuidas aleatoriamente en dos tratamientos (T): T1 (n=4) recibieron una dosis de 200 mg de FSH vía epidural (EP) en el día 4 del protocolo de superovulación (SOV), en T2 se administró 300 mg de FSH repartidas en 8 dosis decrecientes vía intramuscular (IM), los días 4; 5; 6 y 7 del protocolo en la mañana y tarde. La concentración de cortisol se determinó a las 0; 2; 4; 6 ,24; 26; 28; 30; 48; 50; 52; 64; 72; 74; 76 y 78 horas (h) del día 4. La frecuencia cardiaca (FC), respiratoria (FR) y los niveles de glucosa fueron evaluados el día 4 a las 05h45; 06h05; 08h00; 10h00; 12h00; 17h45 y 18h05. El cortisol a las 0h fue similar en los dos T: T1 (10,9 ± 0,24 µg·dL-1) y T2 (10,8 ± 0,33 µg·dL-1) y alcanzó su mayor nivel a las 4h en T1 (15,8 ± 1,39 µg·dL-1) y en T2 (16,4 ± 0,28 µg·dL-1) sin diferencia entre T (P>0,05). En las siguientes valoraciones, el cortisol disminuyó a niveles basales en los dos T. La FC a las 05h45, mostró valores similares en T1 (65,3 ± 1,65 pul·min-1) y en T2 (66,3 ± 1,43 pul·min-1); sin embargo, a las 06h05 FC se incrementó en T1 (74,3 ± 1,54 pul·min-1) y en T2 (84,2 ± 1,73 pul·min-1) y disminuyó a partir de las 08h00. Igual comportamiento fue observado con la FR y la glucosa. Se concluye que llevar a la donadora a la manga de sujeción para administrar FSH, constituye un factor estresante que incrementa la FC, FR, cortisol y glucosa, factores que influyen sobre el porcentaje de ovulaciones en los dos T.