PS9-22. Influence of Birth Type on Biochemical Indicators of Passive Transfer of Immunity in Lambs.

Abstract Efficient neonatal management is essential for improving survival and productivity in sheep production systems. Although multiple births contribute to higher flock productivity, they may negatively affect neonatal development due to limited intrauterine space, lower birth weight, and increased competition for colostrum intake. In ruminants, the syndesmochorial placenta prevents prenatal transfer of immunoglobulins, making the ingestion of adequate colostrum immediately after birth essential for the establishment of passive transfer of immunity. Therefore, the objective of this study was to evaluate the influence of birth type on biochemical indicators associated with passive transfer of immunity in lambs. The study was conducted at the Rive Experimental Farm of the Federal University of Espírito Santo, located in Alegre, Brazil, and approved by the Institutional Animal Care and Use Committee (CEUA protocol 005/2022). Data were collected during the lambing seasons of 2024/2 and 2025/1. A total of 144 lambs born from 48 ewes were evaluated. At birth, lamb vitality was assessed using the APGAR score (Appearance, Pulse, Grimace, Activity and Respiration) and birth weight was recorded. Blood samples were collected to determine serum total protein (STP), albumin concentration, and gamma-glutamyl transferase (GGT) activity as indicators associated with passive immunity transfer. Blood samples were obtained within the first 24 hours of life to evaluate the success of colostrum intake. Twin births were the most frequent (55.6%), followed by singleton births (18.1%) and triplet births (16.7%). Quadruplet and sextuplet births occurred at lower frequencies, representing approximately 10% of the cases, but with mortality rates close to 100%. Mean birth weight was 4.42, 3.76, and 3.36 kg for singleton, twin, and triplet lambs, respectively. Mean serum total protein (STP) concentrations measured at 24 h of age were 7.32, 6.62, and 6.67 g/dL for singleton, twin, and triplet lambs, respectively. Albumin concentrations were 4.72, 4.02, and 4.37 g/dL, respectively. Gamma-glutamyl transferase activity averaged 3104.4, 1941.3, and 2058.6 IU/L for singleton, twin, and triplet lambs, respectively. The results indicate that lambs born from multiple births tend to present lower concentrations of biochemical markers associated with passive transfer of immunity. These findings suggest that lambs originating from multiple births are at greater risk of failure of passive transfer of immunity, likely due to lower birth weight and increased competition for colostrum intake. Therefore, targeted neonatal management strategies, including assisted colostrum intake and closer monitoring during the first hours of life, are essential to improve passive immunity transfer and lamb survival.