The objective was to evaluate the effects of peripartum supplementation of methionine hydroxy analog (MFP; Novus International, Inc. St. Charles, MO) to nulliparous beef females on dam and progeny performance. Yearling Angus heifers (n = 60) were blocked by expected parturition date, stratified by body weight (BW) and body condition score (BCS), and randomized to 1 of 15 pens (4 females/pen). Pens were randomly assigned to 1 of 3 dietary treatments; a basal diet supplemented with either 1) 0 g ïÿý animal-1 ïÿý d-1 of MFP (M0); 2) 15 g ïÿý animal-1 ïÿý d-1 of MFP (M15); or 3) 30 g ïÿý animal-1 ïÿý d-1 of MFP (M30). The basal diet consisted of ground hay, silage, and distillers grains and was formulated to maintain similar BW across treatments. Diets were fed from 45 ïÿý 13 d prior to average parturition date through 81 ïÿý 13 d postpartum (DPP) when all cow-calf pairs were commingled and managed as a singular group on pasture until weaning (199 ïÿý 13 DPP). Dam BW, BCS, and blood samples were taken at six predetermined timepoints throughout the study. Progeny data collection occurred at birth, two intermediate timepoints, and at weaning. Milk samples were collected for component analysis at 7 ïÿý 2 DPP and at 55 ïÿý 5 DPP. Serial blood samples were analyzed to establish resumption of postpartum cyclicity, and ultrasonography was performed at 55 ïÿý 5 DPP to evaluate ovarian function. Cows were artificially inseminated at 82 ïÿý 13 DPP and turned out with bulls for a 55-d breeding season. Continuous and categorical data were analyzed using the MIXED and GLIMMIX procedures of SAS, respectively. Dam BW and BCS were not different (P ≥ 0.24) across treatments throughout the study. Week 1 milk fat increased (P = 0.05) linearly and total solids tended to increase (P = 0.07) as MFP increased in the diet; however, no other milk components differed (P ≥ 0.16) as a result of treatment. No differences (P ≥ 0.16) in dam reproductive parameters or progeny performance were observed. At breeding (the conclusion of dietary treatments) blood urea nitrogen (BUN) concentrations linearly decreased (P = 0.03) with increased supplementation of MFP and non-esterified fatty acids (NEFA) concentrations were lower (P = 0.04) in MFP-supplemented dams compared to dams receiving no MFP. Concentrations of BUN and NEFA were not different (P ≥ 0.22) at any other remaining timepoint nor were glucose and methionine (Met) concentrations different (P ≥ 0.15) at any point. These data indicate that supplementation of MFP in late gestation and early lactation may increase milk fat components immediately after calving but does not translate to significant changes in progeny growth or dam reproductive performance
