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Effect of methionine and choline supplementation on postpartum follicular development in Holstein cows
The aim of this study was to determine the effects of methionine, choline and both methionine and choline supplementation during the transition period on postpartum follicular development in Holstein cows. Cows on their 2nd or greater lactation were assigned in a randomized block design into four treatments from -28 days relative to calving to 30 ± 1 DIM. Treatments were control (CON; n = 10, fed a basal diet and no supplemental methionine or choline), methionine (MET; n = 9, fed the basal diet and top-dressed with 0,08% of DM of diet/d of methionine, Smartamine M®); choline (CHOL; n = 9, fed the basal diet and top-dressed with 60g/d of choline, Reassure®), and methionine and choline (MET+CHOL; n = 12, fed the basal diet and top-dressed with 0,08% of DM of diet/d of methionine and 60 g/d choline). Follicular development was monitored via ultrasound every 2 days starting at 7 DIM until first ovulation occurrence. At each examination, a sketch of each ovary was made, and the diameter and location of follicles >3mm in diameter were recorded. Ovulation was defined as the disappearance (from one examination to the next) of a previously identified follicle >8mm in diameter along with the detection of a CL in the same ovary in a further examination. Statistical analysis was performed using the MIXED procedure of SAS. Supplementation of methionine, choline and both methionine and choline during the transition period did not affect the moment of the first postpartum ovulation (CON 14.93 ± 1.07 d, MET 14.28 ± 1.10 d, CHOL 14.30 ± 1.15 d and MET+CHOL 13.35 ± 1.00 d; P = 0.7385), the number of cows that ovulated the first follicular wave (CON 5/10 cows, MET 5/9 cows, CHOL 5/9 and MET+CHOL 7/12 cows; P = 0.1817), the diameter of the first postpartum dominant follicle (CON 20.51 ± 3.52 mm, MET 22.59 ± 3.52 mm, CHOL 15.83 ± 3.94 mm, and MET+CHOL 17.27 ± 2.78 mm; P = 0.5362), or the growing rate of the first postpartum dominant follicle (CON 1.09 ± 0.20 mm/d, MET 1.36 ± 0. mm/d, CHOL 1.17 ± 0.23 mm/d, and MET+CHOL 1.01 ± 0.16 mm/d; P = 0.6246). In conclusion, supplementing methionine, choline or both methionine and choline during the transition period seemed not to have effect on postpartum follicular development of the 1st wave in Holstein cows.
Keywords: dairy cows, follicle, methionine, choline, transition period