Dexamethasone acutely regulates endocrine parameters in stallions and subsequently affects gene expression in testicular germ cells.

Testicular steroidogenesis and spermatogenesis are negatively impacted by stress-related hormones such as glucocorticoids. The effects of two injections of a therapeutic dose of dexamethasone (a synthetic glucocorticoid, 0.1mg/kg; i.v.) given 24h apart to each of three stallions were investigated and compared to three saline-injected control stallions. Dexamethasone decreased circulating concentrations of cortisol by 50% at 24h after the initial injection. Serum testosterone decreased by a maximum of 94% from 4 to 20h after the initial injection of dexamethasone. Semen parameters of the dexamethasone-treated stallions were unchanged in the subsequent two weeks. Two weeks after treatment, stallions were castrated. Functional genomic analyses of the testes revealed that, of eight gene products analyzed, dexamethasone depressed concentrations of heat shock protein DNAJC4 and sperm-specific calcium channel CATSPER1 mRNAs by more than 60%. Both genes are expressed in germ cells during spermiogenesis and have been related to male fertility in other species, including humans. This is the first report of decreased DNAJC4 and CATSPER1 mRNA concentrations in testes weeks after dexamethasone treatment. Concentrations of these mRNAs in sperm may be useful as novel markers of fertility in stallions.

Temporal changes in histomorphology and gene expression in goat testes during postnatal development.

Testicular cell proliferation and differentiation is critical for development of normal testicular function and male reproductive maturity. The objective of the current study was to evaluate histoarchitecture and expression of genes marking specific cells and important functions as well as testosterone production of the developing goat testes. Testes were harvested from Alpine bucks at 0, 2, 4, 6, and 8 mo of age (n = 5/age group). Paired testes weight increased from 2 to 4 (P < 0.001) and 4 to 6 mo (P < 0.01). The greatest increases in seminiferous tubule and lumen diameters and height of the seminiferous epithelium occurred between 2 and 4 mo (P < 0.001). Genes expressed in haploid germ cells (Protamine1 [PRM1], Outer Dense Fiber protein 2 [ODF2], and Stimulated by Retinoic Acid gene 8 [STRA8]) increased dramatically at the same time (P < 0.001). Expression of other genes decreased (P < 0.05) during testicular maturation. These genes included P450 side chain cleavage (CYP11A1), Sex determining region Y-box 9 (SOX9), Insulin-like Growth Factor 1 Receptor (IGF1R), and Heat Shock Protein A8 (HSPA8). The Glutathione S-Transferase A3 (GSTA3) gene, whose product was recently recognized as a primary enzyme involved in isomerization of androstenedione in man and livestock species including goats, sheep, cattle, pigs, and horses, uniquely peaked in expression at 2 mo (P < 0.05). Follicle-Stimulating Hormone Receptor (FSHR) mRNA abundance tended to steadily decrease with age (P = 0.1), while Luteinizing Hormone Receptor (LHCGR) mRNA abundance in testes was not significantly different across the ages. Testosterone content per gram of testicular tissue varied among individuals. However, testosterone content per testis tended to increase at 6 mo (P = 0.06). In conclusion, major changes in cellular structure and gene expression in goat testes were observed at 4 mo of age, when spermatogenesis was initiated. Male goats mature rapidly and represent a good model species for the study of agents that enhance or impair development of testicular functions.

Dense spermatozoa in stallion ejaculates contain lower concentrations of mRNAs encoding the sperm specific calcium channel 1, ornithine decarboxylase antizyme 3, aromatase, and estrogen receptor alpha than less dense spermatozoa.

Stallions are unique among livestock in that, like men, they commonly receive medical treatment for subfertility. In both species, about 15% of individuals have normal semen parameters but are subfertile, indicating a need for novel analyses of spermatozoa function. One procedure for improving fertilizing capability of stallions and men is isolation of dense spermatozoa from an ejaculate for use in artificial insemination. In the current study, dense and less dense spermatozoa were purified by density gradient centrifugation from individual ejaculates from seven reproductively normal adult stallions. The RNA isolated from the spermatozoa seemed to be naturally fragmented to an average length of 250 bases, consistent with reports of spermatozoa RNA from other species. The DNAse treatment of RNA prepared from spermatozoa removed any genomic DNA contamination, as assessed by PCR with intron spanning primers for the protamine 1 (PRM1) gene. Concentrations of seven mRNAs in spermatozoa, correlated with the fertility of men and bulls, were quantified by reverse transcription polymerase chain reaction in dense and less dense spermatozoa. Concentrations of four mRNAs were two- to four-fold lower in dense spermatozoa compared with less dense spermatozoa: Encoding the spermatozoa-specific calcium channel (P < 0.03), ornithine decarboxylase antizyme 3 (P < 0.02), aromatase (P < 0.02), and estrogen receptor alpha (P < 0.08). In contrast, concentrations of three other mRNAs, encoding PRM1 and heat shock proteins HSPA8 and DNAJC4, were not different (P > 0.1). These results identify new differences in mRNA concentrations in populations of spermatozoa with dissimilar densities.

Relationships between feed efficiency, scrotal circumference, and semen quality traits in yearling bulls.

A meta-analysis was conducted to examine phenotypic relationships between feed efficiency, scrotal circumference, and semen quality traits in yearling bulls. Data evaluated were obtained from 5 postweaning trials involving Angus (n = 92), Bonsmara (n = 62), and Santa Gertrudis (n = 50) bulls fed diets that ranged from 1.70 to 2.85 Mcal ME/kg DM. After an adaptation period of 24 to 28 d, feed intake was measured daily, and BW was measured at 7- or 14-d intervals during the 70- to 77-d trials. Ultrasound carcass traits (12th-rib back fat thickness, BF; LM area, LMA) and scrotal circumference (SC) were measured at the start and end of each trial. Semen samples were collected by electroejaculation within 51 d of the end of the trials when the age of bulls averaged from 365 to 444 d and were evaluated for progressive sperm motility and morphology. Residual feed intake (RFI) was calculated as the difference between actual DMI and expected DMI from linear regression of DMI on ADG and midtest BW(0.75), with trial, trial by ADG, and trial by midtest BW(0.75) as random effects. Across all studies, bulls with low RFI phenotypes (<0.5 SD below the mean RFI of 0) consumed 20% less DM and had 10% less BF but had similar ADG, SC, and semen quality traits compared with high-RFI bulls (>0.5 SD above the mean RFI of 0). Gain to feed ratio was strongly correlated with ADG (0.60) and weakly correlated with initial BW (-0.17) and DMI (-0.26). Residual feed intake was not correlated with ADG, initial age, or BW but was correlated with DMI (0.71), G:F (-0.70), and BF (0.20). Initial SC (-0.20), gain in SC (-0.28), and percent normal sperm (-0.17) were correlated with G:F, but only sperm morphology was found to be weakly associated with RFI (0.13). These data suggest that RFI is not phenotypically associated with SC or sperm motility but is weakly associated with sperm morphology.

Phenotypic and genetic relationships of residual feed intake with performance and ultrasound carcass traits in Brangus heifers.

The objective of this study was to characterize residual feed intake (RFI) and to estimate phenotypic and genetic correlations with performance and ultrasound carcass traits in growing heifers. Four postweaning feed efficiency trials were conducted using 468 Brangus heifers. The complete Brangus pedigree file from Camp Cooley Ranch (Franklin, TX), which included 31,215 animals, was used to generate genetic parameter estimates. The heifer progeny from 223 dams were sired by 36 bulls, whereas the complete pedigree file contained 1,710 sires and 8,191 dams. Heifers were individually fed a roughage-based diet (ME = 1.98 Mcal/kg of DM) using Calan gate feeders for 70 d. Heifer BW was recorded weekly and ultrasound measures of 12th- to 13th-rib fat thickness (BF) and LM area (LMA) obtained at d 0 and 70. Residual feed intake (RFIp) was computed as actual minus predicted DMI, with predicted DMI determined by linear regression of DMI on mid-test BW(0.75) (MBW) and ADG with trial, trial x MBW, and trial x ADG as random effects. Overall means for ADG, DMI, and RFI were 1.01 (SD = 0.15), 9.51 (SD = 1.02), and 0.00 (SD = 0.71) kg/d, respectively. Stepwise regression analysis revealed that inclusion of gain in BF and final LMA into the base model increased the R(2) (0.578 vs. 0.534) and accounted for 9% of the variation in DMI not explained by MBW and ADG (RFIp). Residual feed intake and carcass-adjusted RFI (RFIc) were strongly correlated phenotypically and genetically with DMI and FCR, but not with ADG or MBW. Gain in BF was phenotypically correlated (P < 0.05) with RFIp (0.22), but not with FCR or RFIc; however, final BF was genetically correlated (P < 0.05) with RFIp (0.36) and RFIc (0.39). Gain in LMA was weakly phenotypically correlated with FCR, but not with RFIp or RFIc; however, gain in LMA was strongly genetically correlated with RFIp (0.55) and RFIc (0.77). The Spearman rank correlation between RFIp and RFIc was high (0.96). These results suggest that adjusting RFI for ultrasound carcass composition traits will facilitate selection phenotypically independent of growth, body size, and carcass composition; however, genetic relationships may still exist between RFI and carcass composition.

Improving fertility in beef cow recipients.

In the 1970s, bovine embryo transfer (ET) shifted from research in a laboratory environment to commercialization of this technology for beef producers. With the quarantine requirements and expense of importing Continental breeds of cattle from Europe, embryo transfer became the logical means to reproduce greater numbers of these animals at a lower cost. The ET industry grew very rapidly and soon would become what it is today, a common practice utilized by select ranchers and breeders. Research over the years has primarily focused on methods to increase the number of ovulations and fertilized ova from the donor female, but the total number of transferable embryos has not changed markedly in the last 20 years. More recent advances have been in the area of in vitro production of embryos that allow for greater numbers of embryos to be produced and easier accessibility to incorporate technologies such as sexed sperm, sperm injection, or transgenics. This paper will focus on the second part of the equation, the recipient, and decisions that will enable both the customers and practitioners to most efficiently utilize embryos from superovulation, in vitro production, or nuclear transfer, so that the maximum number of pregnancies can be produced.

Preweaning growth of F1 tropically adapted beef cattle breeds x Angus and reproductive performance of their Angus dams in arid rangeland.

The objective of this study was to determine the preweaning performance of F1 Brahman (Bos indicus)-, Senepol (Bos taurus)-, and Tuli (Sanga)-Angus calves under semiarid south Texas conditions and to evaluate the reproductive performance of their Angus dams. Four hundred eighty-nine records collected over 4 yr were analyzed. The statistical model for performance traits included the effects of breed of sire, year, sex, age of dam, and breed of sire x year. Year effects were important (P < 0.05) for performance traits but could be explained, at least partially, by differences between years in rainfall patterns. Brahman F1 calves were 13% less (P < 0.05) vigorous at birth, 4.7 kg heavier (P < 0.05) at birth, 13.5 kg heavier (P < 0.05) at weaning, 0.25 units lower (P < 0.05) in body condition score (BCS) at weaning, and 1.75 units greater (P < 0.05) in frame score (scores of 1 to 9) at weaning than Tuli and Senepol F1 calves. Senepol F1 calves were intermediate (P < 0.05) between the Brahman and Tuli F1 calves for birth and weaning weight but had 11% more (P < 0.05) vigor at birth than the other two crossbreds. Tuli and Senepol F1 were similar (P > 0.05) in BCS and frame size at weaning. Males were 3.3 kg heavier (P = 0.12) at birth than females, especially for the F1 Brahman males that were 4.5 kg heavier (P < 0.05) than their counterparts. Brahman F1 weaned 19.9 kg heavier (P < 0.05) than the average of the other two F1 in the year of the greatest rainfall (1994), whereas the average advantage in other years was 11.4 kg. This difference gave rise to a breed of sire x year interaction (P < 0.003). Brahman F1 were heavier at every measurement and appeared to be later-maturing and more able to excel under good forage conditions than the other two F1 breed types; Senepol and Tuli F1 were similar (P > 0.05) in these respects but appeared to be more competitive in relative growth rate to the Brahman F1 calves in years of greater nutritional stress. Angus females were observed to have a relatively low reproductive rate and high apparent fetal loss at the first (27.5%) and second (19.2%) compared with the third or later pregnancy (11.2%). Angus females that gave birth to Brahman F1 calves had 20.1% lower (P < 0.05) pregnancy rates in the succeeding year than those that had given birth to the other two breeds.

Pregnancy rate in beef heifers after synchronization to either random or programmed estrous cycles.

We hypothesized that heifers in diestrus at the beginning of a Syncro-Mate-B (SMB) regimen would have higher pregnancy rates to AI than heifers not in diestrus and that administration of a PGF2alpha analogue 11 d before a SMB regimen would increase pregnancy rates to AI. In both replicate years of Exp. 1, heifers (n = 150) were classified by stage of the estrous cycle at the beginning of a SMB regimen (d 0). Following implant removal (d 9), heifers were artificially inseminated 12 h after the onset of estrus (95.5% in estrus by 72 h). Blood samples were collected for progesterone (P4) analysis on d 0, 9, and 20. Pregnancy rates did not differ between yr 1 and 2. Pregnancy rate for heifers classified in diestrus (53.6%; n = 69) was higher (P = 0.06) than for heifers in metestrus (43.7%; n = 48). Pregnancy rate for proestrus (44.4%; n = 18) heifers was not different from that for heifers in the metestrus or diestrus groups. Mean plasma P4 concentration was affected by both treatment and day. Pregnancy rate was higher (P < 0.01) for heifers with P4 > 1 ng/mL plasma (51.6%; n = 120) than for heifers with P4 < or = 1 ng/mL plasma (23.3%; n = 30) on d 0. In Exp. 2, beef heifers (Santa Cruz; n = 195) were allotted to two treatments. Heifers (n = 98) in the control group were administered a conventional SMB treatment. Heifers (n = 97) in the PGF group were injected with PGF2alpha 11 d (d -11) before a SMB regimen. Progesterone concentration was determined from blood samples collected on d -11, -2, 0, and 9. All heifers were artificially inseminated 48 to 50 h after implant removal. At the beginning of the SMB regimen (d 0), a greater (P < 0.05) percentage of PGF (74.2%) than of control heifers (59.2%) were in diestrus (P4 > 1 ng/mL). Mean P4 concentration was not affected by treatment or day x treatment but differed (P < 0.05) among days. Pregnancy rate of cycling heifers was similar for PGF (36%) and control heifers (35.9%). Pregnancy rate was higher (P < 0.01) for heifers with P4 > 1 ng/mL plasma (37.6%) than for heifers with P4 < or = 1 ng/mL plasma (18.5%) on d 0. These results support the hypothesis that fertility is enhanced when a progestin synchrony regimen is initiated during diestrus, but methods to program estrous cycles to increase fertility warrant investigation.

Artificial insemination outcomes in beef females using bovine sperm with a detectable fertility-associated antigen.

In this study, semen samples from 25 bulls that had passed a breeding soundness evaluation were analyzed for the presence or absence of a 31-kDa protein, known as fertility-associated antigen (FAA), on spermatozoal membranes. Eighteen bulls had FAA on sperm (FAA-positive) and seven were devoid of FAA on sperm (FAA-negative). A single ejaculate from each bull was extended and frozen with 25 to 30 x 10(6) sperm in .5-mL straws. Crossbred replacement heifers (n = 865) were estrus-synchronized and artificially inseminated either at timed AI or 12 h after they were detected in estrus. Mature cows (n = 285) were inseminated 12 h after they were detected in estrus during a 45-d AI period. Pregnancy rates (pooled) to first AI service for females (n = 764) inseminated with FAA-positive sperm were 65.6% and were 49.7% for females (n = 386) inseminated with FAA-negative sperm (P < .005). Among the estrus-synchronized replacement heifers, pregnancy rates to synchronized AI service for heifers (n = 550) inseminated with FAA-positive sperm were 62% and were 45.7% for heifers (n = 315) inseminated with FAA-negative sperm (P < .005). These data indicate that pregnancy rates to first AI service at spontaneous and synchronized estrus are higher when using semen from bulls with detectable FAA on spermatozoal membranes compared to semen from bulls devoid of FAA on membranes. Fertility-associated antigen is an important determinant for fertility potential of sperm from bulls to be used in AI breeding programs.

Fertility-associated antigen on bull sperm indicates fertility potential.

A 30-kDa heparin-binding protein named fertility-associated antigen (FAA) was identified in sperm membranes of beef bulls with greater fertility potential. In a survey of 2,191 beef bulls, 88% had FAA present in sperm membranes (FAA-positive), and 12% were FAA-negative. In the first study, 54 Santa Gertrudis and 51 Santa Cruz bulls were grouped (1 to 14 bulls per group) according to FAA profiles and were bred to 2,403 cows at ratios of 1 bull: 25 cows. Fertility for 14 groups of FAA-positive bulls averaged 88%, whereas three groups of FAA-negative bulls impregnated 79% of the cows. Thus, FAA-positive bulls were nine percentage points more (P < .01) fertile than FAA-negative bulls. In the second study, 2-yr-old Santa Cruz bulls (n = 26) were grouped according to FAA profiles and serving capacity. The fertility of the group of 12 high-serving-capacity, FAA-positive bulls was 87% of 270 cows. The group of six FAA-negative bulls with high serving capacity impregnated 78% of 143 cows. Among the groups of bulls with high serving capacity, FAA-positive bulls were nine percentage points more (P < .05) fertile than FAA-negative bulls. The group of eight FAA-positive bulls with low serving capacity impregnated the least (P < .01) percentage (69%) of 238 cows. Serving capacity of bulls should be considered when optimizing fertility potential. Among bulls with acceptable physical characteristics and serving capacity, determination of FAA profiles in sperm can be used as a tool to identify subfertile bulls.

Predicting end-of-test semen quality in bulls prior to performance testing.

The first objective of this study was to determine if serum concentrations of specific hormones (testosterone, progesterone and androstenedione) in bulls at the start of performance testing could predict semen quality at the end-of-test when used in a multivariate model. The second objective was to evaluate other clinical measurements (breed, age, body weight, hip height and scrotal circumference) for predicting end-of-test semen quality. End-of-test semen quality was related to steroid concentrations and several pre-testing measurements, including age, body weight, hip height and scrotal circumference (SC). Combining the 3 steroid concentrations into a predictive test had a sensitivity of 0.6 and specificity of 0.5 at its most accurate point. The repeatability of the test result was extremely low (r(2) = 0.16; P < 0.05). In multivariate analyses, breed and start-of-test SC remained significant predictors of end-of-test semen quality (P < 0.05) while the other variables were nonsignificant (P > 0.1), suggesting that start-of-test SC was the most accurate predictor of end-of-test semen quality. Removing bulls at the start-of-test that had scrotal measurements of less than 20 cm, 24 cm, 28 cm or 32 cm resulted in sensitivities and specificities of 0.19, 0.94; 0.41, 0.81; 0.64, 0.56; and 0.94, 0.12, respectively. No cut-point had both adequate sensitivity and specificity. Because clinical tests were correlated, combining the tests to improve accuracy was not justified.

Temporal aspects of ovarian follicular growth and steroidogenesis following exogenous follicle-stimulating hormone in Angus heifers.

Ultrasonography and endocrine assay techniques were used to monitor structural and hormonal alterations made by the ovary in response to the biological actions of pituitary-derived follicle-stimulating hormone (FSH-P). Angus heifers (n = 36) were allotted to receive injections (twice per day) of either FSH-P (up to a total of 28 mg over a maximum of 4 days beginning on Day 10 of a synchronized estrous cycle) or saline in order to quantify temporal relationships among follicle growth and steroid hormone profiles. Transrectal ultrasonography was utilized at 12-h intervals to monitor and record follicle growth. Plasma was collected every 12 h for the first 48 h of the experiment and then every 6 h for the remainder of the experiment. At 48 and 60 h after the onset of treatments, prostaglandin F2 alpha (PGF2 alpha; 25 mg) was administered (i.m.). FSH-treated heifers (n = 6 at each time) were terminated at 24, 48, 72 and 96 h following the onset of treatment. Saline-treated heifers were terminated at 24 and 96 h (n = 6 at each time). After ovaries were obtained, follicular number and size were recorded and follicular fluid (FF) was collected. Plasma concentration of progesterone (P) and estradiol (E2) and FF concentration of P, E2, estrone, testosterone and androstenedione were determined by radioimmunoassays. Plasma concentration of E2 increased (P < 0.05) within 36 h of initiation of FSH treatment. Plasma P decreased (P < 0.0001) by 12 h post-PGF2 alpha. Ultrasonographic examination revealed a significant decrease in the number of small follicles by 48 h, whereas the number of medium follicles increased (P < 0.05) by 60 h after the initiation of FSH treatment. The number of large follicles (LF > or = 10 mm diameter) increased (P < 0.01) over the course of the experiment. The total number of ovarian follicles (TF) 24 h after the start of FSH treatment was correlated (r = 0.99; P < 0.0001) with the number of small follicles (SF < or = 5 mm). At 72 h after the onset of FSH treatment, the number of medium follicles (i.e. 6-9 mm) was correlated with TF (r = 0.97; P < 0.0001). Estradiol was the predominant FF steroid. Follicular fluid E2 was greatest in follicles at 72 h after FSH treatment. Follicular fluid E2 and plasma E2 were positively correlated (r = 0.66; P < 0.001). Follicular aromatase activity was estimated by evaluating the ratio of FF estrogens (E) to androgens (A). Elevated aromatase activity (E:A ratio > 1.0) was detected in 196 of 206 follicles. The estrogen to progesterone ratio was used as an estimate of follicle viability. Eighty-five percent of the follicles were estimated to be viable (E:P ratio > 1.0). The peak E:A ratio in LF preceded by 24 h the peak concentration in FF E2 and plasma E2. In MF and SF the E:A ratio increased by 72 h. Enhancement of ovarian follicular growth (i.e. increased number and size of follicles; increased steroidogenesis) by exogenous, pituitary-derived FSH is characterized by (1) increased activity of aromatase, and (2) accumulation of FF E2, events which temporally preceded the increase in plasma concentration of E2. These observations will aid efforts to incorporate recombinant bovine FSH and somatotropin in an effort to develop more predictable superstimulation and ovulation induction protocols.

Testicular and epididymal function during the peripuberal period in Brahman bulls receiving various amounts of protein degradable in the rumen.

Thirty-nine Brahman bulls with an initial age and weight of 301.7 +/- 4.1 d and 202.7 +/- 4.7 kg, respectively, were randomly allocated to 1 of 2 dietary treatment groups within age, weight and sire in order to study the influence of source of protein and stage of peripuberal period on testicular and epididymal function. In the soybean meal treatment the amount of protein undegradable in the rumen averaged 47%, while it was 72% in the fish meal treatment. The supplements were isocaloric and isonitrogenous. Bulls were electroejaculated, and castrations were performed randomly in a predetermined order when the first ejaculate with the first motile sperm cells (Stage 1), 10 to 25 million (Stage 2), and 50 million or more sperm cells (Stage 3 - puberty) was obtained. Testicular and epididymal traits were analyzed for a single testicle and epididymis. Daily sperm production, daily sperm production per gram of testicular parenchyma, testicular weight and testicular parenchyma weight were not affected by treatment. Bulls receiving fish meal had heavier (P < 0.01) epididymis than soybean meal-fed bulls (6.6 +/- 1.0 vs 3.9 +/- 0.6 g) but similar (P > 0.05) epididymal sperm reserves. Daily sperm production (1 testicle) was 115.2 +/- 0.1, 447.4 +/- 0.1, 792.7 +/- 0.1 million sperm cells, and daily sperm production per gram of testicular parenchyma was 1.5 +/- 0.5, 3.2 +/- 0.6 and 6.4 +/- 0.6 million sperm cells for bulls at Stage 1, 2 and 3, respectively. Sire and amount of undegradable intake protein had significant (P < 0.05) affects on the distribution of epididymal sperm reserves, with soybean meal-fed bulls having the higher proportions of epididymal sperm reserves in the cauda epididymis.

Reproductive performance of synchronized beef cows as affected by inhibition of suckling with nose tags or temporary calf removal.

A study was conducted to determine whether presence of the calf during suckling inhibition influences the response to estrus synchronization in beef cows. Angus or Hereford cows (n=89) were administered Syncro-Mate-B (SMB), which consisted of a 6-mg norgestomet ear implant (in situ 9 d) in conjunction with 5 mg of estradiol valerate and 3 mg (im) of norgestomet. Cows were allotted by breed, body condition, stage of the estrous cycle, parity and date of parturition to 1 of 3 treatments: 48-h calf removal; ad libitum suckling; or inhibition of suckling with a nose tag for 48 h. Calves were weighed at time of SMB implant removal, 48 h later and at weaning. Cows were mated via AI approximately 12 h after detection of estrus during a 30-d period after implant removal followed by a natural service period of 35 d. At 48 h after implant removal, calf removal and nose tag calves had lost an average of 3.6 and 0.9 kg, respectively, while the suckled calves gained 1.8 kg (P < 0.01). Mean calf weight at weaning did not differ among treatments. Synchronized estrous response (within 5 d of implant removal) was not different among treatments. Pregnancy rate for cows exhibiting a synchronized estrus (5 d AI) for calf removal, nose tag and suckled cows was 76, 48 and 48%, respectively (P>0.10). Treatment did not affect the 30-d AI or overall 65-d pregnancy rate. In this study, there were no differences observed in the percentage of synchronized or pregnant cows following suckling inhibition by either a nose tag or calf removal. Transient reductions of calf body weight during the 48-h calf removal period did occur in both the nose tag and calf removal groups.

Effect of ruminally undegradable protein from fish meal on growth and reproduction of peripuberal Brahman bulls.

Thirty-nine Brahman bulls (301.7 +/- 4.1 d; 202.7 +/- 4.7 kg) were allotted to one of two treatments and fed soybean meal (SBM)- or fish meal (FIS)-based supplements and hay to examine the effects of source of protein on growth and reproductive development. The fish meal supplement had 72% ruminally undegradable protein (RUP) and the soybean meal supplement had 47% RUP. Bulls assigned to the FIS treatment had higher (P < .01) total weight gain (81.2 +/- 1.4 vs 71.2 +/- 2.2 kg), higher (P < .01) ADG (.97 +/- .02 vs .85 +/- .03 kg), and better (P < .05) feed:gain ratio (7.6 +/- .1 vs 8.6 +/- .1 feed/BW gain for FIS vs SBM, respectively). Age at first motile spermatozoa was not affected (P > .05) by source of protein (429.9 +/- 9.6 vs 427.2 +/- 9.5 d, for bulls receiving FIS or SBM supplements, respectively). Likewise, age at puberty (473.3 +/- 21.7 d vs 465.9 +/- 12.9 d for bulls receiving FIS and SBM supplements, respectively) was similar for both treatment groups. There were no differences between treatments in scrotal circumference at those stages. At puberty semen quality was similar for bulls receiving FIS or SBM treatments, and no differences existed in LH and testosterone concentrations between treatments. We conclude that fish meal supplement increased growth but did not alter reproductive parameters in Brahman bulls.

Herbage allowance x yearling heifer phenotype interactions for preweaning calf growth on humid pasture and semiarid rangeland.

Preweaning growth data were obtained during 4 yr on 349 Braford-sired calves from Brahman-Hereford F1 first-calf females. These females were allotted to either semiarid rangeland (Uvalde) or humid improved pasture (Overton) as weanlings and to one of four herbage allowance levels at each location as yearlings. Females were wintered on systems in local industry practice and maintained on various allotted herbage levels both as yearlings and during first lactation. The desired range in herbage allowance (400 to 2,800 kg of DM per 100 kg of BW at Uvalde and 80 to 460 kg of DM per 100 kg of BW at Overton) was accomplished by adjusting stocking rate monthly from April to weaning (October). Herbage allowance and yearling heifer characteristics (hook height, condition score, or weight) were treated as continuous, independent variables in regression analyses. Preweaning daily gain responded to increased herbage allowance differently for the two locations. Generally, at Overton, herbage allowance influenced suckling calf growth to a greater extent than for the F1 yearling variables, but at Uvalde this trend was reversed. Heifers with larger yearling heights had first calves that grew faster to weaning for both locations and all herbage allowances, although the relationship was stronger for greater herbage allowances at Overton (herbage allowance x yearling weight interaction, P < .07). This interaction was not detected (P > .15) at Uvalde. Interactions between herbage allowance and yearling condition score were detected (P < .05) at both Overton and Uvalde, but these interactions were different (P < .15) at the two locations.(ABSTRACT TRUNCATED AT 250 WORDS)

Ratios of serum concentrations of testosterone and progesterone from yearling bulls with small testes.

Thirty crossbred bulls, 12 to 13 mo of age, were used to examine the relationship of testosterone and progesterone concentrations and testosterone: progesterone ratio to measurements of testicular function. Bulls were allotted to 1 of 2 groups based on scrotal circumferences (SC) as follows: the Small SC (n=20) group had scrotal circumference less than 28 cm while the Large SC (n=10) group had scrotal circumference greater than 28 cm. All bulls were administered GnRH (100 mug, im), and blood was obtained immediately prior to injection (t=0), 30 min after injection (t=30) and 2 to 3 h after injection (t=150). Serum was assayed for concentrations of testosterone and progesterone. Semen was evaluated for the percentage of morphologically normal spermatozoa. Testicular parenchyma was sectioned and stained, and 300 cross sections per testis of seminiferous tubules were examined under a light microscope and classified as either active (spermatocytes and spermatids present) or inactive (no spermatocytes or spermatids present). Although progesterone concentrations varied widely (range: 21 pg/ml to 1070 pg/ml), repeated measurements from individual bulls were highly correlated (r(2)=0.74) and did not change significantly (P > 0.1) in response to GnRH treatment. Small SC bulls had a higher percentage of inactive seminiferous tubules (P < 0.001) and a lower percentage morphologically normal spermatozoa (P < 0.001) than Large SC bulls, but no differences in testosterone or progesterone concentrations or in the ratio of testosterone: progesterone were detected. Mean serum testosterone concentration increased (P < 0.0001) by 30 min after GnRH treatment and continued to increase (P < 0.0001) through t=150 but did not differ (p > 0.1) between groups. Normal testosterone secretion in response to GnRH injection suggested that no biochemical lesions in the testosterone production pathway were present in bulls with very small scrotal circumference.

Correlation of in vivo testicle and seminal vesicle size with post mortem dimensions in bulls.

This study was conducted to quantify the relationships between in vivo measurements of testicular and seminal vesicle size and post mortem size of these organs in 30 Santa Gertrudis bulls. The in vivo measurements of testicles were obtained by transrectal ultrasonography and palpation per rectum, while scrotal circumference was measured by scrotal tape. Linear post mortem dimensions were obtained by direct measurements of the excised organs. Volume was assessed by water displacement while the testicles were weighed. Seminal vesicle length, determined by palpation, had the highest correlation with post mortem measurements (r = 0.70; P = 0.0001). Accurate estimation of the thickness of the vesicles (1.47 vs 1.55 cm for in vivo and post mortem, respectively) was performed by ultrasonograph. Of all seminal vesicle linear measurements, width had the highest correlations with volume measured by water displacement (r = 0.67; P = 0.0001 and r = 0.38; P = 0.04 for post mortem and in vivo, respectively). Testicular diameter was accurately measured by ultrasonography (5.54 vs 4.58 cm in vivo and post mortem, respectively) and was highly correlated (range r = 0.84 to 0.89; P = 0.0001) with post mortem measurements of testicular volume, weight and circumference. The correlation between scrotal circumference and diameter of the testicle was 0.75 (P = 0.0001). The correlations of testicular diameter measured by ultrasound with the post mortem measurements of testicular weight and circumference were similar to the correlations between scrotal circumference and those 2 post mortem measurements. We conclude that palpation of vesicle length is highly correlated with volume of the seminal vesicle in situ. Individual linear measurements do not seem to be an accurate predictor of the relativ size of the seminal vesicle. Furthermore, ultrasonography does not seem to be a more accurate measure of testicular size than scrotal circumference for evaluation of breeding soundness.

Relationships between seminal vesicle size and copulatory activity in bulls.

Two experiments were designed to investigate the hypothesis that dimensions of the seminal vesicle are positively correlated with copulatory behavior in bulls. In Experiment 1, thirty Santa Gertrudis bulls (16.5 mo old) were used to study the relationship between copulatory activity and seminal vesicle length and width (palpation per rectum), seminal vesicle thickness (ultrasonography), and volume. The bulls showed a low level of copulatory activity (6.0+/-1.5, 0.8+/-0.3 and 0.3+/-0.1 for mean number of mounts, intromissions and ejaculations, respectively) in 2 tests. The mean number of mounts but not the mean number of intromissions or ejaculations differed (P<0.01) among bulls. No significant correlations were found between seminal vesicle size and any of the variables of sexual behavior. In Experiment 2, 16 beef bulls (18 mo old) were used to study the relationship between copulatory activity and seminal vesicle length (palpation) or dorso-ventral thickness (ultrasonography). Differences were detected (P<0.01) among bulls in mean number of mounts, intromissions and ejaculations achieved in 2 serving capacity tests. No significant correlations were found between copulatory activity and seminal vesicle length or thickness. These data do not support the hypothesis of a positive relationship between seminal vesicle length or thickness with copulatory activity, even for bulls with marked diffences in intensity of sexual behavior.

Luteinizing hormone-releasing hormone gene expression in the bovine brain: anatomical localization and regulation by ovarian state.

Experiments were conducted to identify neurons in the bovine brain that express the LHRH gene and to determine whether LHRH mRNA levels are influenced by the ovaries. Two groups of postpubertal heifers were utilized: heifers killed during the mid-luteal phase of the estrous cycle (LUTEAL, n = 5) and heifers killed 14-16 wk following ovariectomy (OVX, n = 5). In situ hybridization was performed through use of a 32P-end-labeled deoxyoligonucleotide (59 mer) complementary to the human LHRH mRNA sequence. LHRH-expressing neurons were identified in the diagonal band of Broca, the preoptic area, and the anterior hypothalamus in a manner consistent with immunocytochemical localization. Reduced silver grains, proportional to LHRH mRNA content, were quantified (in pixels, 45x objective) with an image analysis system. Expected serum hormone concentration differences between endocrine states were confirmed by radioimmunoassay for progesterone (LUTEAL > OVX, p < 0.01) and for LH (OVX > LUTEAL, p < 0.01). Compared to the OVX group, LUTEAL heifers had 34% fewer LHRH-expressing neurons (p < 0.05); on the average, these neurons possessed 28% fewer pixels/cell (p < 0.01), indicating fewer copies of LHRH mRNA per cell. When the numbers of pixels in all labeled cells were totalled, LUTEAL animals had 57% fewer pixels (p < 0.05) than did the OVX females--probably reflecting a decrease in LHRH synthetic capacity in the LUTEAL animals. Therefore, during the mid-luteal phase of the bovine estrous cycle, ovarian steroid (i.e., luteal progesterone) suppression of LHRH release (as reflected by serum LH) is coincident with decreased LHRH mRNA in the brain.(ABSTRACT TRUNCATED AT 250 WORDS)