The effect of progestin and GnRH treatments on ovarian function and reproductive hormone secretions of anestrous postpartum suckled beef cows.

Eighteen anestrous crossbred suckled beef cows were assigned to one of three treatment groups. Treatments were as follows: Group 1 cows (n = 3) were untreated and served as controls, Groups 2 cows (n = 6) were intramuscularly administered 250 mug GnRH, and Group 3 cows (n = 9) were subcutaneously administered a progestin ear implant for eight days prior to the administration of 250 mug GnRH. The GnRH was given to cows in Group 3 24 h after the time of progestin implant removal. Cows were 21 to 31 days postpartum at the time of GnRH treatment. The percent of cows that ovulated after the time of GnRH treatment was 0%, 83% and 100% for Groups 1, 2 and 3, respectively. For the cows that ovulated, more (P < 0.05) cows in Group 2 (80%) had abnormal luteal phases than in Group 3 (33%). The GnRH-induced LH release and peak LH concentrations were greater (P < 0.01) in the cows in Group 3 (214.3 +/- 37.1 ng/ml) than in the cows in Group 2 (142.7 +/- 19.0 ng/ml). The LH concentrations of the control cows remained very low throughout the sampling period. Although prostaglandin metabolite (PGFM) concentrations were not significantly (P > 0.10) different among groups, mean concentrations were higher and more variable for cows in Groups 1 (39.2 +/- 5.2 pg/ml) and 2 (39.4 + 6.1 pg/ml) than for cows in Group 3 (25.1 + 1.4 pg/ml).

The effect of days postpartum, indomethacin and oxytocin on prostaglandin metabolite concentrations in postpartum suckled beef cows.

In Experiment 1, blood samples were collected on days 1, 4, 7, 10, 13, 16, 19, 22, and 25 postpartum from the jugular veins of 10 suckled beef cows to determine 13, 14-dihydro-15-keto prostaglandin F2alpha (PGFM) concentrations during the early postpartum period. PGFM concentrations on days 1 and 4 were 207.8+/-33.9 and 283.6+/-45.6 pg/ml and then declined linearly (r=-0.71; P<0.05) to 44.1+/-5.7 and 44.0+/-5.3 pg/ml on days 22 and 25 postpartum. Two groups of postpartum (25.3+/-0.5 and 37.7+/-1.1 days) suckled beef cows (10 cows/group) were used in the second experiment. Five cows of each group received intrauterine infusions of indomethacin for 5.5 days while the other five cows of each group served as controls. All cows had calves removed at the time of the last indomethacin infusion and were subcutaneously administered oxytocin six hours later. During the infusion period, PGFM concentrations decreased (P<0.01) across time for both groups of indomethacin-treated cows. Concentrations of PGFM increased (P<0.05) after oxytocin treatment for both groups of control and indomethacin-treated cows, but concentrations were higher for the control cows than for the indomethacin-treated cows.

Effect of days postpartum and exogenous GnRH on reproductive hormone and ovarian changes in postpartum suckled beef cows.

Two experiments were conducted to determine the effect of days postpartum and exogenous gonadotropin releasing hormone (GnRH) on reproductive hormone and ovarian changes in postpartum suckled beef cows. In experiment 1, eight suckled cows were bled at .5 hour intervals for 4 hours on days 7, 14, 21 and 28 postpartum. Although mean concentrations of plasma luteinizing hormone (LH) were positively correlated with days postpartum, mean concentrations did not differ. The mean maximum change and the variance of plasma LH were low on days 7, 14, 21 and 28 postpartum. Although the number of cows with an ovarian follicle and follicular size increased with days postpartum, mean concentrations of estradiol-17beta did not change. The interval from parturition to the first detected ovarian follicle and the first postpartum estrus was 17.5 +/- 2.6 days and 36.0 +/- 2.2 days, respectively. An elevation in plasma progesterone was detected about one week prior to the first postpartum estrus in 6 of the eight cows in the absence of corpora lutea. In experiment 2, gonadotropin releasing hormone (GnRH) induced ovulation in 4 of the 8 cows treated on day 27, 28 or 29 postpartum whereas none of the 8 saline treated cows ovulated to treatment. The interval from parturition to first estrus and conception were similar for both groups (P >.10).

The effect of method of GnRH administration and short-term calf removal on ovarian function and reproductive performance in postpartum suckled beef cows administered PGF(2)alpha for estrous synchronization.

The first experiment was a 2 x 2 factorial experiment with calf removal (none or short-term) and method of GnRH administration (intramuscularly in saline or subcutaneously in gelatin capsules) as main effects. The durations of the GnRH-induced LH surges were similar among groups but the LH surges were delayed in the cows that received GnRH subcutaneously in gelatin capsules. Calf removal enhanced the GnRH-induced LH release for cows administered GnRH subcutaneously in a gelatin capsule but not for cows administered GnRH intramuscularly in saline. In the second experiment, 191 postpartum suckled beef cows were administered two injections of prostaglandin F(2)alpha(PGF(2)alpha) 11 days apart. After the second PGF(2)alpha injection, the cows were assigned to a 2 x 2 factorial experiment as in Experiment 1 plus one control group. Short-term calf removal (47 h) began 28 h after the second PGF(2)alpha injection. GnRH was administered 30 h after the time of calf removal. The number of cows that ovulated following the time of the GnRH treatment, the number that had abnormal luteal phases and the first-service pregnancy rates among treatment groups within the anestrous and cyclic cows classifications were not significantly different. However, several effects were detected and are reported.

Detection of estrus with cows administered testosterone via injections and/or silastic implants.

Over a three year period 8 cows and 2 heifers were administered testosterone via injections and/or silastic implants. During and subsequent to treatments, blood samples were collected for determination of testosterone and cows were observed for male sex behavior. Male sex behavior was induced by administering 200 mg of testosterone propionate every other day for 20 days, and once induced, male sex behavior was maintained by injections of 200 mg of testosterone propionate every 10 days or by two 15 cm silastic implants containing testosterone propionate. Male sex behavior was also induced and maintained by administering an injection of testosterone enanthate (1 gm) and testosterone propionate (200 mg) and two 15 cm silastic implants containing testosterone propionate at the same time. Cows which are administered testosterone in this manner detected 94% of 231 females that were in estrus 342 times.

Reproductive hormone secretions and first service conception rate subsequent to ovulation control with Synchro-Mate B.

Two groups of beef females receiving suboptimal energy diets were treated with Synchro-Mate B to control ovulation. The first group consisted of 30 suckled cows and 16 heifers. These females were bled 10 days and immediately prior to the implantation of norgestomet implants, at implant removal, 24, 27, 30, 33 and 36 hours and 9 and 16 days post-implant removal. The second group which consisted of 40 cows and 8 heifers was handled in the same manner except no blood samples were collected from 24 to 36 hours following implant removal. Calves were removed from all the cows for 48 hours, beginning at implant removal. All animals were artifically inseminated 48 hours following implant removal. Blood plasma was assayed for concentrations of progesterone and LH. The first service conception rate was 21% and 40% for groups 1 and 2. Several factors were identified that reduced the first service conception rate. In summary, Snychro-Mate B is an effective method to synchronize estrus in cattle. However, stress subsequent to implant removal should be avoided in order to obtain a higher first service conception rate.

Ability of indomethacin to alter prostaglandin metabolite concentrations and to enhance the function of corpora lutea induced in postpartum suckled beef cows.

Fourteen anovulatory postpartum (38.0 +/- 1.9 d) beef cows that ovulated after an injection of 250 micrograms gonadotropin releasing hormone (GnRH) in saline were used to examine the influence of indomethacin on luteal function. Beginning the d after GnRH, 6 cows were given intrauterine infusions of indomethacin for 14 d and the other eight cows received vehicle. After GnRH treatment, concentrations of progesterone in serum were elevated longer (P less than .01) for indometacin-treated cows than for vehicle-treated cows. At the same time prostaglandin metabolite (PGFM) concentrations were lower (P less than .01) in indomethacin-treated cows than in vehicle-treated cows. In summary, indomethacin suppressed PGFM concentrations and enhanced function of corpora lutea induced in postpartum suckled beef cows.

Ovulation and reproductive hormones following steroid pretreatment, calf removal and GnRH in postpartum suckled beef cows.

Two experiments were conducted to determine the effect of calf removal, steroid pretreatment and treatment with gonadotropin releasing hormone (GnRH) on subsequent reproductive hormone secretion and ovulation. In the first experiment, GnRH was administered to postpartum beef cows at two levels (100 and 250 microgram) and in two carrier vehicles (saline and carboxymethylcellulose [CMC]). Although peak luteinizing hormone (LH) concentrations were similar for all cows, the interval from treatment to peak LH release and the duration of the LH release was prolonged (P < .05) in the cows that were given GnRH in CMC. In the second experiment, 30 postpartum suckled beef cows were assigned to a 2 X 3 factorial experiment, with calf removal (none or short-term) and steroid pretreatment (none, norgestomet implant or Synchro-Mate B) as main effects. Short-term calf removal consisted of a 36-hr nonsuckling period beginning at the time of implant removal. GnRH (250 microgram in CMC) was injected subcutaneously 24 hr after implant and calf removal. An increased GnRH-induced LH release due to short-term calf removal (P < .05) and steroid pretreatment (P < .10) was detected. The interaction was not significant, however, (P < .25). Therefore, the suckling-induced suppression of pituitary LH release to exogenous GnRH can be at least partially eliminated within 24 hr of calf separation of norgestomet implant removal. The GnRH-induced LH release was correlated with pretreatment concentrations of estradiol-17 beta for cows that were not separated from their calves (r = .61; P < .05) but not for cows that were subjected to short-term calf removal (r = .28; P > .10). Ovulation occurred in all cows (100%) that were separated from their calves and given GnRH, whereas only 67% of cows not subjected to calf removal ovulated following GnRH treatment. Although the ovulation responses differed (P < .025) between cows that were and were not separated from their calves, ovulation response was not affected by steroid pretreatment (P > .10).

Norgestomet and gonadotropin-releasing hormone enhance corpus luteum function and fertility of postpartum suckled beef cows.

In Exp. 1,101 suckled beef cows were administered two injections of prostaglandin F2 alpha (PGF2 alpha) 11 d apart. Cows in Group 1 received no additional treatment. Cows in Groups 2 and 3 received 250 micrograms of GnRH plus 47-h calf removal. Cows in Group 3 also received a norgestomet ear implant that was inserted 4 d after the first PGF2 alpha injection and left in situ for 8 d. The second PGF2 alpha injection was administered approximately 28 h before the time of norgestomet implant removal. The GnRH was administered approximately 30 h after the time of norgestomet implant removal (or 58 h after the second PGF2 alpha injection). Calf removal was the period from the time of implant removal to AI. All cows were artificially inseminated once 75 h after the second PGF2 alpha injection (47 h after implant removal). Reproductive status before the time of GnRH treatment (presynchronization) was determined by multiple sampling (2, 13, and 23 d before GnRH treatment) for blood progesterone concentrations (62% anestrous and 38% cyclic). The GnRH treatment increased (P < .01) the ovulation response and norgestomet reduced (P < .01) the incidence of short luteal phases in the presynchronization anestrous cows. Norgestomet treatment increased (P < .05) the timed breeding pregnancy rates for both presynchronization anestrous and cyclic cows. In Exp. 2, 174 suckled beef cows were administered Syncro-Mate B (which includes norgestomet). Cows in Group 1 received no additional treatment, whereas cows in Group 2 received 250 micrograms of GnRH (30 h after norgestomet implant removal).(ABSTRACT TRUNCATED AT 250 WORDS)

Clostridial antibody response from injection-site lesions in beef cattle, long-term response to single or multiple doses, and response in newborn beef calves.

Experiments were conducted to compare clostridial antibody response of beef heifers that do and do not develop injection-site lesions, evaluate long-term antibody response of a single- and multiple-dose toxoid, and evaluate the ability of a clostridial toxoid to elicit an active antibody response in newborn calves. In Exp. 1, 37 weaned heifers were vaccinated (d 0) with a clostridial vaccine (Alpha-7, 2 mL, s.c.). Serum samples were collected on d 0, 28, 56, 84, and 112 to determine clostridial antibody titers. On d 28, heifers were visually inspected and palpated for injection-site lesions. The percentage of heifers that developed lesions was 64.9%. Lesioned heifers had elevated antibody titers for Clostridium chauvoei (CC) on d 28 (P < 0.08) and 84 (P < 0.07) compared with non-lesioned heifers. Clostridium sordellii (CS) and perfringens type D (CPD) antibody titers were greater in lesioned heifers than in non-lesioned heifers on d 28 and 56. In Exp. 2, long-term antibody response of Alpha-7 (A7) and Ultrabac 7 (UB7) was investigated in stocker heifers. The A7 heifers (n = 15) received one 2-mL vaccination (d 0), and the UB7 heifers (n = 15) received a 5-mL vaccination on d 0 and 28. Blood samples were collected on d 0, 28, 56, 84, 112, 140, and 180. Clostridium chauvoei, CPD, and Cl. novyi (CN) antibody titers from the A7 heifers were greater than those from the UB7 heifers on d 28. Due to the second UB7 injection, CC, CS, CN, and Cl. perfringens type C (CPC) antibody titers were greater in UB7 heifers than in A7 heifers on d 56. By d 112, titers were not different, and by d 140 all antibody titers were below detectable levels. In Exp. 3, 58 pregnant, mature, crossbred cows were vaccinated with A7 before calving. At birth, calves were carefully observed to ensure consumption of colostrum. Calves were blocked according to parturition date, and calves in each block were randomly allocated to receive A7 (s.c. at 3 +/- 3 d of age) or remain unvaccinated controls. Calves were bled at the time of vaccination (d 0) and on d 28, 56, 84, and 112. Antibody titers for CC, CPC, and CPD were elevated on d 0 and decreased throughout the experimental period (P < 0.01), but no titer differences (P > 0.10) were detected between treatment groups on any of the days sampled. These data indicated that antibody titers against clostridial diseases are enhanced when injection-site lesions develop. One injection of Alpha-7 seemed to provide the same length of protection as two injections of Ultrabac 7.

Clostridial vaccination efficacy on stimulating and maintaining an immune response in beef cows and calves.

Experiments were conducted to determine the efficacy in stimulating and maintaining an immune response in the presence of maternal antibodies, compare the extent of the anamnestic responses to revaccination, and compare the maternal antibody response of 2- or 5-mL clostridial vaccination. In Exp. 1, 118 nursing calves were randomly assigned to receive a 2-mL (Alpha-7, A7) or a 5-mL clostridial vaccine (Ultrabac 7; UB7) at 50.4 +/- 15.30 (X +/- SD) d of age (d 0 = date of calving). Calves were revaccinated with the same treatment on d 170. Blood samples were collected from 10 calves of each treatment group on d 50, 170, and 191 to determine antitoxin units for Clostridium perfringens type C (PC) and D (PD) and agglutination titers for Cl. chauvoei (CC). The A7-treated calves tended (P < .10) to have higher PC units on d 170, an increased rate of change in PD units from d 170 to d 191 (P < .06), and a tendency (P < .10) for enhanced CC titers on d 191 compared with UB7-treated calves. In Exp. 2, 109 pregnant cows and 83 pregnant heifers were randomly assigned within a 2 x 2 x 2 factorial design. The main effects were dam age (cow or heifer), dam treatment (A7 or UB7), and calf treatment (A7 or UB7). Dams were vaccinated with A7 or UB7 d 124 prepartum (d -124) and d 53 after birth. At d 53.4 +/- 12.88, calves were vaccinated with A7 or UB7 (d 53). Calves were revaccinated with the same treatment on d 173. Blood samples were collected from 10 dams per treatment group on d -124, 53, and 173 and from their calves on d 53, 173, and 194. Cows had higher antitoxin levels for PC (P < .01) and PD (P < .05) than heifers. The A7-treated dams had higher (P < .01) PD units on d 53 and d 173 and CC on d 173 than did UB7-treated dams. Calves from A7-treated cows had higher (P < .03) PD units on d 53 than calves from UB7-treated cows. The A7-treated calves had higher titers for CC (P < .01) on d 173 than did UB7-treated calves, and this enhanced level seemed to continue to d 194 (P < .08). In conclusion, titers for clostridial diseases in 50- to 53-d-old calves can be enhanced if dams are vaccinated approximately 4 mo before calving, and 120 d between clostridial vaccinations seems to be too long for adequate protection.

Relationships of barometric pressure and environmental temperature with incidence of parturition in beef cows.

The relationship between barometric pressure (BARO) and maximum (MAX_T) and minimum (MIN_T) environmental temperatures with the incidence of parturition in beef cows was examined through exploratory data analysis. Spring- and fall-calving records from a 5-yr period (2005 through 2009) collected at the University of Arkansas, Livestock and Forestry Research Station (Batesville) and the Department of Animal Science Savoy Research Unit (Savoy, AR) were used. All cows were multiparous, predominantly Angus, and naturally bred. During this period, 2,210 calves were born over a cumulative 1,547 d. Local weather station BARO and MAX_T and MIN_T data were obtained from the Southern Regional Climate Center, Louisiana State University, Baton Rouge. The combined calving record and climate variables were used to determine differences in BARO, MAX_T, and MIN_T on d 0 (d of calving) and -1, -2, or -3 d, respectively, before calving occurred (CALFD) or did not occur (NOCALFD). Location and season also were included in the model. For fall-calving cows, BARO on d 0 and -1, -2, or -3 was not different between CALFD and NOCALFD (P > 0.10). For spring-calving cows, BARO on d 0, -1, -2, and -3 was greater (P < 0.05) for CALFD compared with NOCALFD. The MAX_T was greater on d -1 (24.4 vs. 22.9°C) and -3 (24.8 vs. 23.4°C) for CALFD in the fall compared with NOCALFD (P < 0.05). No differences were detected in the fall for MAX_T on d 0 or -2 (P > 0.10). In the spring, a decreased MAX_T was associated with CALFD. Maximum environmental temperatures on d 0 (14.7 vs. 16.0°C), -1 (14.4 vs. 16.0°C), and -3 (14.0 vs. 15.7°C) were less for CALFD compared with NOCALFD (P < 0.05). No difference was detected on d -2 (P > 0.10). For fall, MIN_T was greater on d -1 (12.8 vs. 11.3°C), -2 (13.0 vs. 11.4°C), and -3 (13.1 vs. 11.7°C) for CALFD compared with NOCALFD (P < 0.05). In spring, MIN_T for d 0 (2.6 vs. 3.9°C), -1 (2.5 vs. 3.7°C), -2 (2.1 vs. 3.7°C), and -3 (1.8 vs. 3.8°C) were lesser (P < 0.05) for CALFD vs. NOCALFD. These data indicate that for spring-calving cows, a greater BARO and decreased MAX_T and MIN_T were associated with CALFD, whereas for fall-calving cows, an increase in MAX_T and MIN_T was associated with CALFD. Therefore, monitoring weather conditions may assist producers in preparing for the obstetric assistance of beef cattle.

Comparing the 2000 and 2005 factors affecting the selling price of feeder cattle sold at Arkansas livestock auctions.

The objectives of the study were to determine how factors affecting the selling price of feeder calves changed from 2000 to 2005 and to examine the perception that discounts narrow or even disappear as calf supplies decrease and selling prices increase. Data from weekly Arkansas livestock auctions were collected from January 1 to December 31 in 2000 and 2005. Data included calf sex, breed type, color, muscle score, horn status, frame score, fill, condition, health, and BW. Mean selling prices for 2000 and 2005 were $92.91 +/- 15.05 and $118.32 +/- 15.13 (mean +/- SD; $/45.45 kg), respectively. Individual price observations were subtracted from the respective annual means and became the dependent variable. The selling prices for feeder calves sold in groups of 2 to 5 calves and in groups of >/= 6 calves were greater in 2005 than 2000 (P < 0.001). Steers received a greater premium ($6.48 +/- 0.09 vs. $6.02 +/- 0.08; mean +/- SE) and bull calves received greater discounts ($0.30 +/- 0.14 vs. $1.68 +/- 0.09) in 2005 than in 2000. Breeds types that increased in value from 2000 to 2005 were Angus x Hereford, Angus, Angus x Charolais, and Brahman (P < 0.001). Breed types that received a reduced selling price in 2005 compared with 2000 (P < 0.001) were one-fourth Brahman Cross, Charolais, Charolais x Limousin, Hereford x Limousin, Limousin, Limousin x one-fourth Brahman, Longhorn, Saler and Simmental. Yellow-white face, black-white face, black, and gray feeder calves received an increase in selling price from 2000 to 2005 (P < 0.001). Although fewer horned feeder calves were sold in 2005 (P < 0.01), they received greater discounts in 2005 than 2000 (-$2.86 +/- 0.16 and -$0.51 +/- 0.09; P < 0.001). In 2005, large-framed feeder calves did not receive the premium detected in 2000, but medium-framed feeder calves in 2005 received a greater selling price compared with 2000. Feeder calves with a muscle score of 1 received a greater premium in 2005 compared with 2000 ($2.58 +/- 0.06 and $0.02 +/- 0.09, respectively; P < 0.001). Feeder calves with a muscle score of 2 were discounted in both years, but the discount in 2005 was not as great as in 2000 (P < 0.001). Full and tanked feeder calves received greater discounts in 2005 than in 2000 (P < 0.001). Discounts for fleshy and fat feeder calves were greater in 2005 than in 2000. Most factors affecting the selling price of Arkansas feeder calves in 2000 affected the selling price in 2005. Although feeder calf supplies were smaller in 2005 than 2000, many discounts increased.

Factors affecting the selling price of feeder cattle sold at Arkansas livestock auctions in 2005.

Data were collected from 15 Arkansas livestock auctions to determine factors affecting selling price. Data included how calves were sold (single or groups), sex, breed or breed type, color, muscle thickness, horn status, frame score, fill, body condition, age, health, BW, and price. Data were randomly collected on 52,401 lots consisting of 105,542 calves. Selling prices for steers ($124.20 +/- 0.07), bulls ($117.93 +/- 0.12), and heifers ($112.81 +/- 0.07) were different from each other (P <0.001). Hereford x Charolais feeder calves sold for the highest price ($122.66 +/- 0.14) and Longhorns sold for the lowest price ($74.52 +/- 0.46). Yellow feeder cattle received the highest selling price ($96.47 +/- 0.12), and spotted or striped feeder cattle received the lowest price ($83.84 +/- 0.23). The selling price of singles was lower than the price for calves sold in groups of 6 or more ($117.26 +/- 0.06 vs. $122.61 +/- 0.21; P <0.001). For cattle classified as having muscle scores of 1, 2, 3, and 4, selling prices were $120.45 +/- 0.05, $111.31 +/- 0.09, $96.28 +/- 0.44, and $82.21 +/- 1.87, respectively. Polled feeder cattle sold for $118.57 +/- 0.05, and horned feeder cattle sold for $114.87 +/- 0.14 (P <0.001). Interactions (P <0.001) were detected between frame score and BW groups, and muscle score and BW groups on the selling price of cattle. A number of management and genetic factors affected the selling price of feeder cattle.