PSVI-20 - Effect of Skin Thickness and Rumen-protected Methionine on Body Temperature of Nelore Cows Keep on Tropical Environment

Abstract: The aim of this study was to evaluate the effect of rumen-protected (RPM) supplementation on body temperature, as well as the relationship between skin thickness and body temperature of Nelore cows in a tropical climate. The study was carried out at the Hildegard Georgina Von Pritzelwitz Agrozootechnical Experimental Station (Fazenda Figueira), located in southern Brazil (23º34'26" S; 50º58'14" W), during the 2020/2021 breeding season. In the period from d-28, 28 days after the FTAI protocol, the animals were divided into 2 treatments: the Control Group (CG) receiving 100g/cow/day of mineral salt, and the Methionine group (MG) with the same mineral salt supplementation plus 3g RPM. Between d-9 and d-2 FTAI the body temperature was measured using a data logger coupled to the progesterone device, with assessment of vaginal temperature every 30 minutes. The skin was measured in millimeters (mm) with a cutimeter in the scapular region at the same day of pregnancy diagnosis (d28). The mean plus one standard deviation of the skin thickness was used to categorize the animals with thick skin and thin skin corresponding to (CG: 5.09% of 530 animals; GM: 5.28% of 530 animals) leaving a total of 55 animals in total, GC=27 and MG=28. Data were analyzed using Mixed Models in JMP, considering the body temperature as the random variable; group, day, quartile and their interactions with fixed effects; animals were included as a random effect. Body temperature was different between GC (38.878±0.028) and GM (38.784±0.028), P< 0.05. The interaction between group and skin category was different between GC-thin skin (38.92±0.041) and MG-thin skin (38.74±0.037; P< 0.05), the other categories showed no difference (P > 0.05). The other evaluations did not show difference (P >0.05). In conclusion, methionine was able to reduce the internal body temperature of Nelore cows at tropical temperatures, mainly in those with thin skin thickness.