429 - The Effect of Melatonin Supplementation on Dam Milking Traits and Calf Performance in Beef Cattle

Melatonin has been documented to alleviate compromised pregnancies and enhance livestock performance traits. The objective of this study was to determine the effect of melatonin supplementation on milking traits in beef cattle dams and subsequent influence on calf performance. Cows (n = 60) were blocked based on embryo transfer donor and sire, potential calf breed and embryo grade. At day 190, 220 and 250 of gestation, dams were administered either 2 subdermal ear melatonin implants (preMEL) or no implants (preCON). After parturition, birth weights were recorded and calves randomly received either melatonin implants (posMEL) or none (posCON) on approximately day 0, 30, and 60. At approximately day 60 of lactation, a subset of dams (n = 32) were selected based on age, weight and calf sex for milk collection and analysis. At weaning, calf weight and morphometric data were collected and adjusted according to weaning age. Prenatal melatonin administration did not change calf birth weight (P = 0.956). Milk yield tended to decrease in the preMEL group (P = 0.054) at 2.368 kg ± 0.11 compared to preCON at 2.054 kg ± 0.11. Milk fat percent tended to decrease (P = 0.07) in preMEL at 3.25 ± 0.19 versus preCON at 3.92 ± 0.19. There were no differences in prenatal treatment in respect to milk protein, lactose, solid non-fats, somatic cell count, and urea nitrogen (P > 0.16). At weaning, calf head circumference decreased (P < 0.031) in the preMEL group at 77.92cm ± 0.42 versus preCON at 79.31cm ± 0.45. Otherwise, there were no prenatal or postnatal treatment differences in respect to weaning weight, crown-rump length, hip height and head length (P > 0.12). Previous studies show crown-to-rump length and ponderal index differences. Our lack of differences might be attributed to geographical locations that impact day length or endogenous melatonin status.