The effect of confinement on days to puberty in gilts

In the late fall and winter of 1982 to 1983, 112 crossbred gilts were used in a factorially arranged experiment to determine the effect of confinement on the age at which a gilt reaches first estrus (puberty). Two environments (confinement and non-confinement) and three ages at movement to non-confinement (100, 140, and 180 d) were studied. No differences were detected (P greater than .05) between confinement and non-confinement in the proportions of gilts reaching puberty by 210 d of age. Gilts were older at puberty (P less than .05) in confinement than in non-confinement (192.0 vs 187.7 d) and had a longer interval (P less than .05) from first boar contact to first estrus (12.1 vs 7.8 d). Age at puberty (192.1 vs 187.0 vs 190.5 d) and the proportion reaching puberty (56.4 vs 45.7 vs 65.8%) were not different (P greater than .05) between age-of-movement groups. However, a higher (P less than .05) proportion of the non-confinement gilts reached puberty within 10 d after the beginning of boar exposure than confinement (44.6 vs 26.8%). Moving gilts from confinement to non-confinement (pasture) at 180 d appeared to be the most effective method tested for inducing puberty in gilts.     

Influence of manure gases on puberty in gilts

To determine whether manure gases can influence onset of puberty in gilts, 42 crossbred gilts were reared from 10 to 40 wk of age on concrete slats over a 1.22-m deep pit that was drained and refilled with clean water biweekly (clean group). Forty-one gilts were reared over a similar type pit where manure was allowed to accumulate (control group). Treatments were in two separate rooms of the same building with similar feeding, water, floor space, lighting and room temperature. Ventilation fans with timer controls in each room were set so fans in the clean environment ran twice as long as fans in the control environment. Aerial concentrations of ammonia in the control room were fourfold higher than in the clean room (21 vs 5 ppm), while aerial concentrations of hydrogen sulfide were similar. Average daily gain and feed efficiency were similar for both groups [.69 vs .72 kg/d (P = .31) and 1.61 vs 1.54 kg feed/kg gain (P = .52)]. From 20 to 40 wk of age, all gilts were exposed to a mature boar three times weekly, utilizing four boars in rotation. Blood samples were collected weekly from each gilt by venipuncture and analyzed for progesterone to establish time of first ovulation. A greater proportion of gilts in the clean group attained puberty by 24 to 26 wk (P less than .05) and 27 to 29 wk of age (P less than .10) compared with the control group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of elevated ambient temperatures on puberty in gilts

Effects of elevated ambient temperature on puberty and related physiological responses were studied in 40 gilts. Group 1 (n = 20) gilts were born in September and Group 2 (n = 20) gilts were born in March. Gilts were placed in environmentally controlled chambers at 140 d of age. After a 10-d acclimation period at 20 degrees C, 35% relative humidity (RH), and 12 h light (L)/12 h dark (D), gilts within each group were randomly assigned to one of two treatments: control (C; 15.6 degrees C, 35% RH, 12 h L/12 h D) or heat stress (HS; 33.3 degrees C, 35% RH, 12 h L/12 h D). Daily detection of estrus with a boar began at 180 d of age and continued for 50 d. All gilts not reaching puberty by 230 d of age received 1,000 IU pregnant mare serum gonadotropin (PMSG) and 7 d later were examined by laparotomy. Rectal temperatures (REC) and respiration rates (RESP) were taken twice daily. Food intake (FI) and water usage (WC) were recorded daily. Blood samples were collected weekly and BW recorded at 150, 190, and 230 d of age. No differences (P greater than .05) were observed due to season of birth. Heat-stressed gilts had greater (P less than .001) REC and RESP and consumed more (P less than .01) water than C gilts. Food intake and ADG were not different between treatments (P greater than .05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of active immunization against growth-hormone releasing factor on puberty and reproductive development in gilts.

Hormones within the somatotropin cascade influence several physiological traits, including growth and reproduction. Active immunization against growth hormone-releasing factor (GRFi) initiated at 3 or 6 mo of age decreased weight gain, increased deposition of fat, and delayed puberty in heifers. Two experiments were conducted to investigate the effects of GRFi on puberty and subsequent ovulation rate in gilts. Crossbred gilts were actively immunized against GRF-(1-29)-(Gly)2-Cys-NH2 conjugated to human serum albumin (GRFi) or against human serum albumin alone (HSAi). In Exp. 1, gilts were immunized against GRF (n = 12) or HSA (n = 12) at 92 +/- 1 d of age. At 191 d of age, antibody titers against GRF were greater (P < .05) in GRFi (55.5 +/- 1.3%) than in HSAi (.4 +/- 2%) gilts. The GRFi decreased (P < .05) BW (86 +/- 3 vs 104 +/- 3 kg) by 181 d of age and increased (P < .05) backfat depth (15.7 +/- .4 vs 14.8 +/- .4 mm) by 130 d of age. At 181 d of age, GRFi reduced the frequency of ST release (1.0 +/- .5 vs 5.0 +/- .5, peaks/24 h; P < .0001) and decreased (P < .01) ST (1.1 +/- .06 vs 1.7 +/- .06 ng/mL), IGF-I (29 +/- 2 vs 107 +/- 2 ng/mL), and insulin concentrations (3.5 +/- .2 vs 6.3 +/- .2 ng/mL). The GRFi decreased (P < .05) feed conversion efficiency but did not alter age at puberty (GRFi = 199 +/- 5 d vs HSAi = 202 +/- 5 d) or ovulation rate after second estrus (GRFi = 10.7 +/- .4 vs HSAi = 11.8 +/- .5). In Exp. 2, gilts were immunized against GRF (n = 35) or HSA (n = 35) at 35 +/- 1 d of age. The GRFi at 35 d of age did not alter the number of surface follicles or uterine weight between 93 and 102 d of age, but GRFi decreased (P < .05) ovarian weight (.41 +/- .08 vs 1.58 +/- .4 g) and uterine length (17.2 +/- 1.1 vs 25.3 +/- 2.3 cm). Immunization against GRF reduced (P < .05) serum IGF-I (GRFi = 50 +/- 4 vs HSAi = 137 +/- 4 ng/mL) and BW (GRFi = 71 +/- 3 vs HSAi = 105 +/- 3 kg) and increased (P < .05) backfat depth (GRFi = .38 +/- .03 vs HSAi = .25 +/- .02 mm/kg). Age at puberty was similar in GRFi and HSAi gilts, but ovulation rate was lower (P < .05) after third estrus in GRFi (11.3 +/- .8) than in HSAi (13.8 +/- .8) gilts. Thus, GRFi at 92 or 35 d of age decreased serum ST, IGF-I, and BW in prepubertal gilts without altering age of puberty. However, GRFi at 35 d of age, but not 92 d of age, decreased ovulation rate. These results indicate that alterations in the somatotropic axis at 1 mo of age can influence reproductive development in pubertal gilts.     

Effect of confinement method on physiology and production of gestating gilts

Four replicates of 12 Dekalb crossbred gilts were blocked by breeding dates and randomly allotted to four treatments: tethers, crates, loose stalls and dirtlot. Ear vein cannulas were established and blood samples obtained from each gilt on d 2, 9 and 65 of treatment Blood cell counts, blood chemistry profile (12 items), triiodothyronine (T3), thyroxine (T4), basal cortisol and cortisol in response to administration of adrenocorticotrophic hormone (CR-ACTH) were determined. Tethered gilts had depressed CR-ACTH at d 2, probably related to their active struggles against the tethers during the initial period following restraint. Triiodothyronine was greatest in gilts housed loose with access to stalls, probably reflecting the fighting that often occurred among those gilts, and was lowest in gilts on dirtlot on d 2. Glutamic pyruvate transaminase was elevated in gilts on dirtlot at d 9 and 65, probably a result of their increased exercise. Behaviors indicative of "restlessness" were negatively correlated with CR-ACTH at d 9 and 65. Gilts were initially stressed when restrained in tethers, but their CR-ACTH became equivalent to that of gilts in other housing by 9 d. Housing had no effect on production.     

Follicular fluid concentrations of estradiol-17 beta and progesterone and secretory patterns of LH and FSH in prepubertal gilts reared in confinement or outdoor lots

One-hundred-twenty crossbred gilts from two experiments were assigned randomly to a 2 X 5 factorial experiment. Gilts were reared in two environments (confinement or outside) and assigned to be slaughtered at 4, 5, 6, 7 or 8 mo of age. Beginning at 6 mo of age, blood samples were taken at weekly intervals from each gilt via venipuncture. Serum concentrations of progesterone were analyzed to determine when gilts attained puberty. On the day prior to slaughter, six pigs within a treatment group were cannulated and blood samples were taken at 20-min intervals for 4 h. At slaughter, follicular fluid (FF) was aspirated and the volume determined from those follicles having a diameter of at least 4 mm. No effect of environment was found on the proportion of gilts that attained puberty by 8 mo of age. For the 12 gilts that reached puberty during the study, the age at puberty for gilts reared in outdoor lots (202 +/- 5 d) was less (P less than .05) than those reared in confinement (224 +/- 8 d). Mean concentrations of serum luteinizing hormone (LH; P = 98) and number of secretory spikes of LH (P = .76) were similar between gilts reared in confinement and those reared in outdoor lots. No differences in average serum concentrations of follicle stimulating hormone (FSH) or number of secretory spikes of FSH were found between gilts subjected to these environments (P = .95). Concentrations of estradiol-17 beta in FF were not affected by environment or age (P greater than .25).(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of lean growth rate on puberty attainment in gilts

Two hundred sixteen prepubertal Genex Manor hybrid F1 gilts were used to determine the impact of lean growth rate on sexual development of gilts. This study was composed of two experiments (Exp. 1 and Exp. 2). In Exp. 1, at approximately 96 d of age and 54 kg weight, gilts were allocated with respect to growth rate and litter origin to one of two dietary treatments: 1) a diet formulated to maximize lean growth potential (LP; n = 84) or 2) a diet formulated to produce a lower lean growth rate (LL; n = 84). In Exp. 2, at approximately 88 d of age and 50 kg weight, gilts were allocated with respect to growth rate and litter origin to one of two dietary treatments: 1) a diet formulated to maximize lean growth potential (LP; n = 24) or 2) a diet formulated to restrict lean growth further than was achieved in LL in Exp. 1 (RL; n = 24). All gilts were fed treatment diets for ad libitum consumption and housed in groups of six. Weight, backfat depth and loin depth, and feed intake were measured weekly. Starting at 135 d of age, gilts received 20 min of direct daily exposure to a boar as a pen group for pubertal stimulation. Puberty attainment was determined as the day gilts first exhibited the standing reflex in response to contact with a boar. At pubertal estrus, body weight, backfat depth, and loin depths were recorded. Diet affected (P < or = 0.05) estimated fat-free lean gain (LP, 424 vs LL, 347 g/d, Exp. 1; LP, 397 vs RL, 376 g/d, Exp. 2) during the growth period (start to stimulation). However, age at puberty was not affected by diet (LP, 157.3 vs LL, 157.6, Exp. 1; LP, 166.7 vs RL, 167.3, Exp. 2) or overall lean growth at stimulation (P > or = 0.05 in both experiments), confirming that innate variability in sexual development of commercial genotypes, rather than growth performance, determines onset of sexual maturity. A negative correlation between age at puberty and growth rate from 50 kg until puberty (P < or = 0.05) (LP, r = -0.40, LL, r = -0.36, Exp. 1; LP, r = -0.64, RL, r = -0.48, Exp. 2) was a consequence of reduced lean tissue growth during the stimulation period in later-maturing gilts.     

后备母猪初情期启动分子营养调控机制的研究进展

后备母猪种质的好坏直接影响着规模化猪场的非生产天数的多少,其中能量、蛋白质和维生素对后备母猪初情期启动机制影响很大,因此可通过精准营养供给模式合理调控后备母猪初情期启动过程。本文对影响后备母猪初情期启动的因素以及分子营养对初情期启动机制的调控进行综述,旨在为规模化猪场后备母猪营养调控提供技术参考。     

The effect of transportation/relocation on cortisol, CBG and induction of puberty in gilts with delayed puberty

Twenty-seven Swedish purebred Yorkshire gilts were transported 12 km to the clinic. In 8 gilts (Group A), blood samples were drawn in connection with transportation, while in the remaining 19 gilts (Group B) no samples were drawn at this time. After transportation the gilts were examined by laparoscopy and catheterized. Blood samples were then drawn 3 times and oestrus detection was performed twice daily. After 1 week the laparoscopy was repeated.Twenty gilts (74 %) showed oestrus within 1 week, on average 5.4 days (4–7.5 days) after transportation. Elevated oestradiol-17β levels were seen in those gilts approximately 2 days after transportation. The Cortisol level was significantly higher (p < 0.001) on day 1 (the day of transportation) than on day 2 and a markedly higher level of Cortisol was seen on days 1 and 2 in the gilts which did not show oestrus (2 gilts), compared with the gilts in which oestrus was induced (6 gilts) by transportation. The difference was significant on day 2 (p < 0.05). The CBG level was significantly decreased (p < 0.001) on day 2 for all 8 gilts. During day 3 to day 8 there was no difference in the Cortisol level between days (groups A and B, 27 gilts), and no differences were seen in the levels of Cortisol and CBG between gilts showing (20 gilts) and not showing oestrus (7 gilts). The hypothesis propounded that the higher levels of Cortisol on days 1 and 2 inhibited induction of oestrus in those gilts which did not show oestrus after transportation.     

Effects of exercise during the growing-finishing period on performance, age at puberty and conception rate of gilts

Littermate gilts were used to study the effects of exercise during the growing-finishing period on performance, age at puberty and conception rate. In trial 1, 12 gilts walked 15 min daily on a treadmill 6 d/wk (Monday through Saturday) until they attained body weights of about 100 kg, while 12 littermate gilts were not forced to exercise. Initial weight and age averaged 24.7 kg and 74 d, respectively. For trial 2, 12 gilts walked 30 min daily 6 d/wk (Monday through Saturday) on a treadmill, while 12 littermate gilts were not exercised. Initial weight and age of these gilts averaged 26.8 kg and 76 d, respectively. The treadmill was operated at 0 slope and at a speed of 2.6 km/h. Within trial, there were no differences (P greater than .05) in weight gain, average daily gain, feed consumed, feed to gain ratio, average backfat depth of loin eye area between gilts exercised and those not exercised. In both trials, there were no differences (P greater than .05) in age at puberty between exercised and nonexercised gilts. In trial 2, 10 gilts were selected in each of the exercised and nonexercised groups and were hand-mated to the same boar on the second estrous cycle. Eight gilts from the exercised group conceived, while nine from the nonexercised group conceived. Four gilts from the nonexercised groups had severe locomotor problems while only one gilt from the exercised groups had difficulty walking.     

Effect of prepubertal consumption of zearalenone on puberty and subsequent reproduction of gilts

Forty-eight prepubertal gilts (178.7 +/- 4.1 d; 94.2 +/- 4.1 kg), 16 in each of three trials, were assigned randomly to receive 0 (C) or 10 ppm zearalenone (Z) daily in 2.5 kg of a 14% protein finishing ration for 2 wk. Blood samples were collected at 20-min intervals for 4 h 1 wk after the start of the experiment and 1 wk after Z was withdrawn. Two weeks after Z was withdrawn, gilts were exposed to mature boars 15 min per day for 3 wk. Gilts in estrus were mated to two different boars 12 h apart. Twice each week, blood was sampled and analyzed for progesterone to establish age of puberty. Age at puberty differed (P = .008) among replicates but was similar (P = .13) between Z and C gilts within each replicate. Mean serum concentrations of LH were suppressed (P = .025) during consumption of Z (.25 vs .42 ng/ml) but were similar (P = .16) to concentrations in C gilts 1 wk after Z was withdrawn (.35 vs .45 ng/ml). Frequency and amplitude of LH secretory spikes did not differ (P greater than .50) between Z and C gilts during either sampling period. Mean serum concentrations of FSH were similar (P = .25) between Z and C gilts. Number of corpora lutea and live fetuses were similar (P = .29 and P = .94, respectively) between Z and C gilts. Fetal weights were greater (P = .025) and crown to rump length tended to be greater (P = .10) in fetuses from Z gilts.(ABSTRACT TRUNCATED AT 250 WORDS)     

Contact with oestrous female pigs stimulates and synchronises puberty in gilts.

Three experiments, using a total of 132 pre-pubertal gilts, were carried out to investigate the influence of contact with oestrous female pigs on the attainment of puberty by gilts. Experiment 1 compared the effect of removing the gilts from their groups as they reached puberty in response to exposure to a boar, with leaving the gilts in their groups for five to 15 days after puberty or five to 15 days after second oestrus. All the groups exposed to boars reached puberty significantly earlier than controls (P less than 0.05) but there was no difference between these groups in their mean age at puberty. However, the synchrony of puberty was significantly greater among the gilts which remained in their groups after puberty (P less than 0.01) or second oestrus (P less than 0.001) than among the gilts which were removed at puberty. Experiment 2 investigated the influence of housing pre-pubertal gilts with penmates induced into puberty with injections of oestradiol benzoate. Puberty was significantly advanced by the presence of penmates regularly exhibiting oestrous periods. Experiment 3 compared the effect of daily exposure to an anoestrous ovariectomised sow, an oestrous ovariectomised sow or a boar, on the attainment of puberty by gilts. Gilts exposed to either an oestrous sow or a boar were significantly younger at puberty than isolated control animals (P less than 0.05) whereas the mean age at puberty of gilts exposed to an anoestrous sow was not significantly different from that of controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

Onset of puberty in young gilts kept under conditions of intensive husbandry

Gilts that had already reached sexual maturity at the time of insemination showed a higher rate of oestrus and better litter size than immature animals. Therefore animals selected for breeding should have had at least one oestrous cycle. Onset of puberty can be judged by the occurence of a first oestrous with pronounced redness and swelling of the vulva, but without willingness to be mounted. Changing the housing or exercising the gilts, rendered necessary by the production process, had a stimulating effect on the onset of puberal oestrus. Age at onset of sexual maturity did not affect the performance of gilts in their first production cycle, but litter size was greater when the rate of weigth gain was high.