Rayanne C. Castanheira

This study represents the second phase of a longitudinal experiment evaluating the long-term cumulative effects of feeding strategies initiated at birth on the body development, metabolic profile, and feed efficiency of Gir dairy heifers during the rearing period. Thirty-four Gir dairy heifers participated in this study, which took place over a period of 133 days (21 days of adaptation and 112 days of data collection). A randomized block design was used with two treatments applied at birth: a conventional feeding plan (CF), offering 4% of body weight (BW) as dry matter (DM), and an optimized feeding plan (OF), offering 5% of BW as DM. Growth, feed efficiency, metabolic profile, and vulvar and teat morphometry were evaluated. Data were analyzed using linear and generalized mixed models. Average DM intake was 2.51% and 2.46% of BW for OF and CF, respectively. Heifers on OF showed a greater average chest circumference than those on CF. No differences were observed between treatments for residual feed intake, feed efficiency and feed conversion, teat and vulvar morphometry, or blood parameters. Our findings indicate that the growth differences established under the feeding plan initiated at birth were maintained throughout the rearing period, with no effects on feed efficiency, metabolic profile, or mammary gland development.

Detecting and monitoring pregnancy in cattle is essential and can be achieved through various methods. In recent years, new technologies have been explored to better understand reproductive phenomena, with particular attention given to non-invasive approaches. This study reports thermographic and clinical findings of two Zebu cows (Cow 1: spontaneous abortion; and Cow 2: pregnant) at 236 days of gestation. Eight hours after abortion, thermal imaging and rectal temperature were recorded (First Trial) and compared with the pregnant cow, kept under the same housing and dietary conditions. A second evaluation was conducted five days later (Second Trial). No clinical abnormalities or fever were observed in either cow. In both trials, the pregnant cow consistently showed a 0.9°C higher average abdominal temperature compared with the cow that experienced spontaneous abortion. This difference may be related to increased blood flow and metabolic activity in the uterus during gestation, resulting in greater heat conduction to the body surface. Despite the short interval post-abortion, thermography detected temperature differences suggestive of reproductive status. These findings support the potential of infrared thermography as a non-invasive tool for assessing reproductive status and thermal physiology in cattle.