106 Comparative growth rates and haematological parameters from calves born by transfer of vitrified in vitro-produced embryos and stepbrother calves born by AI

Abstract

Assisted reproductive technologies (ART) are being extensively used to produce cattle offspring. However, as shown by Siqueira et al. (2017 J. Dairy Sci. 100, 5899-5908; https://doi.org/10.3168/jds.2016-12539), phenotypical and performance differences between cows derived from distinct ART can be found at different stages of development. Thus, in an attempt to mimic the natural environment, reproductive fluids (oviductal (SOF) and uterine fluids) were added as supplementation to embryo culture media. Our hypothesis was that this improved culture media would produce calves more similar to the ones produced by AI. In vitro-produced (IVP) beef embryos were produced using SOF media supplemented with reproductive fluids (RF) or standard protocol (BSA), vitrified and later warmed and transferred to synchronized dairy recipients. Simultaneously, other dairy recipients were inseminated (AI) with the same bull used to produce IVP embryos. A total of 19 calves are included in this study (RF n = 5, BSA n = 7, AI n = 7). Calves that did not reach 45 days of life were excluded from these data. All animals received the same feeding and housing conditions. Calves were examined at Days 0, 3, 7, 15, 30, and 45 of life. Each examination included weight, height at withers, thorax circumference, heart and respiratory rates, body temperature, and a blood sample from the jugular vein to perform a general haematological analysis (Siemens ADVIA 120) and glucose levels. A non-parametric test (Mann-Whitney U) was used to compare paired samples, with significance assumed when P < 0.05. Since day is a factor that influences growth, it was assumed as a fixed factor, and data were analysed per day. In terms of growth development, AI calves were significantly taller than BSA calves in all days, and in general taller than RF calves, with the exception of Days 3 and 7. Thorax circumference was significantly smaller for BSA versus AI calves only on Days 15 and 45. Respiratory rate was higher for RF calves at birth and for BSA calves at Day 3 when both were compared with AI calves, but we found no difference between them. Heart rate was higher for RF calves on Day 7 compared with BSA and AI, and higher again on Day 15 compared with AI. Regarding haematological parameters, significant differences were found on Day 0, with platelet counts being lower for BSA calves. On Day 7, mean corpuscular volume from AI calves was lower than either BSA or RF calves, and on Day 15, eosinophils were lower for RF calves compared with AI. At Day 30, white blood cells and lymphocyte concentration were lower for BSA than for AI calves. Glucose levels were higher for RF calves than for AI calves on Day 45. Overall, all haematology and clinical values seem to match the values of healthy calves (Brun-Hansen et al. 2006 Vet. Clin. Pathol. 35, 182-187; https://doi.org/10.1111/j.1939-165X.2006.tb00111.x), and the differences found were not clinically relevant. In conclusion, at the moment and from the analysed criteria of development during the first 45 days of life, there seems to exist no difference between calves born by IVP with RF as supplement to culture media and their in vitro or in vivo controls.