Effects of Parity Order on Performance, Metabolic, and Hormonal Parameters of Grazing Beef Cows During Pre-calving and Lactation Periods

Abstract

Background: Metabolic profile evaluation is a tool widely used in ruminant nutrition as metabolic cues that relate nutrition to physiology. Metabolic and hormonal traits change during pre-partum and lactation according to parity in dairy cows, but studies of beef cows under grazing are scarce. The present study aimed to evaluate how metabolic and hormonal traits change over time, their relationship to performance, and determine if these factors differ according to the parity order of grazing beef cows. Thirty-six pregnant Nellore cows (12 nulliparous, 12 primiparous, and 12 multiparous) were used. The study started at 60 d prepartum until 203 d of lactation.Results: The initial body weight (BW) and final BW were higher for multiparous cows (P > 0.05). An interaction occurred between parity and day (P <.0001) for body condition score (BCS). Nulliparous and primiparous BCS were reduced from -60 prepartum to 30 postpartum, then stabilized 60 postpartum (P < 0.05), while multiparous maintained BCS from -60 days until 60 days postpartum (P > 0.05). Calf BW, final BW, and ADG did not differ between parities (P > 0.05). Effect of day (P < 0.05) was detected for NEFA, triglycerides, total cholesterol, LDL, VLDL, progesterone, and insulin. An interaction was observed between parity and days for glucose, βHB, creatinine and IGF-1 (P < 0.05). Parity affected SUN, total proteins, albumin, and globulins (P < 0.05). Parity and day relative to calving did not impact total T3 and T4 (P > 0.05). Conclusions: Hormonal and metabolic profile is strongly influenced by the stage of lactation. Time effects (pre-partum and lactation period) were more pronounced in nulliparous since they displayed more unbalanced metabolic and hormonal traits and lowered BCS pre- and postpartum.