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Effect of supplementing methionine hydroxy analog on beef cow performance, milk production and reproduction
Mature Simmental × Angus cows (n = 214; 635 ± 7.4 kg) were utilized to determine the effects of late gestation and early postpartum supplementation of methionine hydroxy analog (MFP; Novus International, Inc.) on cow BW, BCS, milk production, milk composition, reproduction, and calf performance until weaning in a fall-calving, cool-season grazing system. Cows were confirmed pregnant prior to experiment, stratified by BW, cow age and AI sire, and assigned to one of twelve pastures (17 or 18 cows·pasture-1). Pastures were randomly allotted to one of two treatments: control (0.45 kg·cow-1·d-1 of wheat mid based pellets, n = 6) or supplement including MFP (0.45 kg·cow-1·d-1 of wheat mid based pellets including 10 g MFP, n = 6). Treatments were fed 23 ± 1 d prior to calving through 72 ± 1 d postpartum. Cows were weighed post-calving, at supplementation end, AI breeding, AI pregnancy check, and the end of trial (192 and 193 ± 1 d postpartum). A subset of cow-calf pairs were used in a weigh-suckle-weigh 74 d postpartum to determine milk production; milk samples were taken to determine milk composition (n = 45·treatment-1). A serum P4 assay was utilized to determine cow cyclicity. After supplementation, all cow-calf pairs were managed as a common group until weaning (191 ± 1 d of age). Cows were bred via AI 97 ± 1 d postpartum, clean up bulls were turned out 11 d post AI for a 55 d breeding season. Cow and calf performance were analyzed using MIXED procedure in SAS (SAS Inst. Inc., Cary, NC) and cow reproductive performance and calf health were analyzed using GLIMMIX procedure. Cow BW and BCS was not different (P ≥ 0.10) at any time points between treatments. There was no treatment effect (P ≥ 0.62) on calf birth BW, calf weaning BW (191 ± 1 d of age), or calf ADG. Calculated 24 h milk production did not differ (P = 0.76) nor did milk composition or component production (P ≥ 0.21). There was no difference (P = 0.69) in percentage of cows cycling between treatments. Cow AI conception rate and overall pregnancy rate were not different (P ≥ 0.50) between treatments. No differences (P ≥ 0.61) in calf health were observed. Supplementation of MFP during late gestation continuing through estimated peak lactation did not affect cow performance, cow milk production, or calf performance when fall-calving cows grazed cool-season forages.
Keywords: cow-calf, methionine hydroxy analog, late gestatation supplementation