PSIX-25 Interaction between maternal parity and creep feeding supplementation on the productive performance and metabolism of grazing Nellore cow-calf pairs.

Abstract Maternal nutrient availability and body condition (BCS) during the peripartum period can influence the postpartum performance of beef cows and the growth and metabolism of their progeny. Maternal parity may also impact these responses, yet the mechanisms remain unclear. Furthermore, the effect of calf supplementation on maternal performance according to parity shows conflicting results, particularly in primiparous cows. This study aimed to evaluate the interaction between maternal parity and creep feeding supplementation on the productive performance and metabolism of grazing Nellore cow-calf pairs. A total of 54 pregnant Nellore cows (24 primiparous and 30 multiparous, average gestational age 230 days) were monitored from 60 days into prepartum until 240 days postpartum. At 100 days old, calves were divided into two groups: Control (n=25) receiving ad libitum mineral mix, and Supplemented (n=27) receiving a daily protein-energy supplement (6 g/kg of body weight (BW); 270 g of crude protein/kg dry matter). Cow BW was recorded every 30 days, and BCS was assessed at -60, -30, 1, 30, 60, and 240 days relative to calving. Milk production was measured at 30, 100, and 240 days, while colostrum Brix value was assessed 12-24 hours postpartum. Cow blood samples were taken at -20, 1, 20, 40, and 240 days relative to calving to analyze glucose, blood urea nitrogen (BUN), total proteins, and protein fractions. Calves were weighed every 30 days, and blood samples were collected at 1, 8, 20, 100, and 240 days of age to assess glucose, total proteins and fractions, and ceruloplasmin concentrations. Data were analyzed using a completely randomized design with the GLIMMIX procedure of SAS (version 9.4), with statistical significance declared at (P < 0.05). Multiparous cows had greater BW (P < 0.05) throughout and greater BCS at weaning (P < 0.05). Primiparous cows had higher BCS at 60 days prepartum (P < 0.05). A significant interaction (P < 0.05) was observed between parity and milk collection day, with multiparous cows producing more milk (P < 0.05) at 100 days. Parity and collection day affected albumin and BUN levels (P < 0.05), but not for other metabolites (P > 0.05). Colostrum Brix values did not differ by parity (P > 0.05). Calf supplementation improved BW (P < 0.05) from 150 to 240 days of age, regardless of parity (P > 0.05). Supplemented calves also had greater BUN levels (P < 0.05). However, supplementation had no effect on serum glucose, total proteins, albumin, globulins, and ceruloplasmin (P > 0.05). Maternal parity influenced cow BCS, BW, and milk yield, with multiparous advantages over primiparous cows. Creep feeding supplementation improved calf growth but had minimal metabolic effects. The findings highlight the importance of managing nutritional strategies in cow-calf systems to optimize productive efficiency.