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Two experiments examined effects of GnRH administered within 3 h after onset of estrus (OE) on ovulation and conception in dairy cows. In experiment 1, 46 cows received either saline, 250 microg of GnRH, or 10 microg of the GnRH analogue, Buserelin. Cows were observed for estrus, blood samples were collected, and ovulations were monitored by ultrasound. In controls, 76% of cows had intervals from estrus to ovulation of < or = 30 h and 24% had intervals > 30 h. Treatment with either GnRH or GnRH analogue (data combined) increased magnitude of LH surges and decreased intervals from estrus to LH surge or to ovulation. Treated cows all ovulated < or = 30 h after OE. Among control cows, plasma estradiol concentrations before estrus correlated positively with amplitudes of LH surges. Higher plasma progesterone was observed in the subsequent estrous cycle in GnRH-treated cows compared to control cows with delayed ovulations. Experiment 2 included 152 primiparous and 211 multiparous cows in summer and winter. Injection of GnRH analogue at OE increased conception rates (CR) from 41.3 to 55.5% across seasons. In summer, GnRH treatment increased CR from 35.1 to 51.6%. Across seasons, GnRH increased CR from 36.0 to 61.5% in cows with lower body condition at insemination and GnRH increased CR (63.2 vs. 42.2%) in primiparous cows compared to controls. Use of GnRH eliminated differences in CR for cows inseminated early or late relative to OE and increased CR in cows having postpartum reproductive disorders. In conclusion, GnRH at onset of estrus increased LH surges, prevented delayed ovulation, and may increase subsequent progesterone concentrations. Treatments with GnRH increased conception in primiparous cows, during summer, and in cows with lower body condition.

Short fertile half-lives of the male and female gametes in the female tract necessitate accurate timing of artificial insemination. We examined the possible association between extension of the estrus to ovulation (E-O) interval and alterations in concentrations of estradiol, progesterone, and the preovulatory LH surge before estrus and ovulation. High-yielding Holstein cows (n = 74 from a total of 106) were synchronized and were examined around the time of the subsequent estrus. They were observed continuously for estrual behavior. Blood samples were collected before and after estrus, and ultrasound checks for ovulation were made every 4 h. About three-quarters of the cows exhibited short (but normal) E-O intervals of 22 to 25 h (25%) or normal intervals of 25 to 30 h (47%); 17% of them displayed a long (but normal) E-O interval of 31 to 35 h, and about 10% exhibited a very long E-O interval of 35 to 50 h. Extended E-O interval comprised estrus-to-LH surge and LH surge-to-ovulation intervals that were both longer than normal. Pronounced changes in hormonal concentrations were noted before ovulation in the very long E-O interval group of cows: progesterone and estradiol concentrations were reduced, and the preovulatory LH peak surge was markedly less than in the other 3 groups. Postovulation progesterone concentrations during the midluteal phase were lesser in the very long and the long E-O interval groups compared with those in the short and normal interval groups. Season, parity, milk yield, and body condition did not affect the estrus to LH surge, LH surge to ovulation, and E-O intervals. The results indicate an association between preovulatory-reduced estradiol concentrations and a small preovulatory LH surge, on the one hand, and an extended E-O interval, on the other hand. Delayed ovulation could cause nonoptimal timing of AI, a less than normal preovulatory LH surge that may be associated with suboptimal maturation of the oocyte before ovulation, or reduced progesterone concentrations before and after ovulation. All may be factors associated with poor fertility in cows with a very long E-O interval.

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This study presents a novel method for use of the wild plant species Cephalaria joppensis (CJ) as agricultural forage for ruminants. Domesticated CJ tends to have higher crop mass yield per hectare than a commercial wheat variety (W) but is similar in in vitro dry matter (DM) digestibility. This study was composed of 3 experiments. Experiment 1 aimed to measure effects of ensiling CJ versus W in packed polyethylene-wrapped bales. Three types of ensiled bales were produced for each plant: 1) direct-cut CJ versus W packed solely; 2) direct-cut CJ versus W mixed as sole roughage source together with dietary ingredient and packed in bales to create CJ total mixed ration (CJ-TMR) or W-TMR; 3) CJ silage versus W silage mixed as one-third of dietary roughage source together with two-thirds sorghum (S) silage and additional dietary ingredients and packed in bales to create CJ-S-TMR or W-S-TMR. Data showed that packing and wrapping created anaerobic conditions within the 4 types of TMR bales while reducing pH (4.12 to 4.37). Dry matter loss during ensilage was higher for the 2 types of TMR containing W compared with CJ. Ensilage decreased soluble nitrate content as well as yeast and mold contamination, and the 4 types of TMR bales were characterized by a long outdoor shelf life (3 mo) and high stability under aerobic exposure. Experiment 2 aimed to measure the intake and digestibility by sheep of the 4 types of packed TMR after 90 d of ensiling. Data demonstrated higher voluntary intake of the CJ-TMR compared with the other TMR types. The CJ-TMR was characterized by higher digestibility of DM, crude protein, and neutral detergent fiber components compared with the CJ-S-TMR. Experiment 3 examined intake, digestibility, and milk production by 21 pairs of lactating cows individually fed CJ-S-TMR versus W-S-TMR. Similar intake (21.6 to 22.0 kg/d) and digestibility of DM and crude protein were observed in cows fed the 2 TMR types (68 to 69% and 66 to 68%, respectively). However, neutral detergent fiber and cellulose digestibility were slightly higher in the cows fed W-S-TMR and this was reflected in a small increase in their milk and energy-corrected milk yield (36.5 and 31.4 kg/cow per day, respectively) compared with cows fed CJ-S-TMR (35.5 and 30.4 kg/cow per day, respectively). Results demonstrate that direct-cut CJ used as is, or CJ silage can be included and ensiled in TMR bales for feeding productive ruminants as a substitute for wheat silage.