Reproductive performance of postpartum ewes treated with insulin or progesterone hormones in association with ram effect

The reproductive performance of postpartum Santa Inês (SI) and Morada Nova (MN) ewes treated with insulin or progesterone hormones in association with ram effect was evaluated. Ewes from SI (n = 69) and MN (n = 69) breeds were randomly allocated to three groups of each breed (T1—ram effect only; T2—ram effect + insulin; T3—ram effect + progesterone). Progesterone concentrations (ηg/ml; mean ± SD) before and after introduction of rams (n = 6) were 0.51 ± 0.22 and 3.78 ± 0.68 (T1), 0.65 ± 0.21 and 3.77 ± 0.78 (T2) and 0.52 ± 0.21 and 3.84 ± 0.84 (T3) in SI ewes and 0.74 ± 0.19 and 3.71 ± 0.56 (T1), 0.70 ± 0.21 and 3.79 ± 0.75 (T2) and 0.81 ± 0.14 and 3.87 ± 0.80 (T3) in MN ewes, respectively. Thus, lower progesterone concentrations were found before the introduction of rams (p < .05). After the introduction of rams, preovulatory peaks of LH (ηg/ml) occurred at 28 (T1), 44 (T2) and 48 (T3) hr in SI ewes and at 64 (T1), 40 (T2) and 44 (T3) hr in MN ewes. The mean number of ovulations was similar between groups (p > .05), was 1.3 ± 0.51 (T1), 1.5 ± 0.54 (T2) and 1.6 ± 0.51 (T3) in SI ewes and 1.3 ± 0.51 (T1), 1.6 ± 0.51 (T2) and 1.6 ± 0.51 (T3) in MN ewes. In conclusion, the ram effect alone is effective at inducing and synchronizing oestrus in sheep under postpartum anoestrus, irrespective of hormone treatments.     

Reproductive characteristics of endophyte-infected or novel tall fescue fed ewes

Reduced pregnancy rates often occur in ruminants grazing endophyte-infected (EI) tall fescue. The objectives were to characterize basal and oxytocin-induced PGF_2α concentrations in serum and reproductive function in ewes fed tall fescue seed and to determine whether addition of fish meal (FM) to a diet of EI fescue would alter PGF_2α production. Ewes were fed a diet with novel or non-toxic endophyte-infected (NE) or EI tall fescue seed containing either corn gluten meal (CG) or FM. Serum concentrations of prolactin, a measure of severity of fescue toxins, were reduced in ewes fed EI compared with NE forage seed (forage × day, P < 0.02) and were greater in NEFM than NECG-fed ewes (P < 0.03). Size and number of corpora lutea (CL), determined by trans-rectal ultrasonography, were similar between diets (P > 0.10). Serum concentrations of progesterone were reduced in ewes with two CL fed EI compared with NE seed (forage × CL number × day, P < 0.001). Oxytocin-induced PGFM concentrations during the luteal phase were determined as a measure of uterine function. On the day of oxytocin administration, peak plasma concentrations of PGFM were reduced in EI compared with NE-fed ewes (forage × time, P < 0.003), but FM did not influence PGFM concentrations. Estrous cycle length was more variable in EI than NE-fed ewes. There appears to be some asynchrony between NE and EI-fed ewes leading to changes in uterine responsiveness to oxytocin. Inclusion of FM did not alter uterine responsiveness to oxytocin.     

Reproductive performance of layer chickens reared on deep litter system with or without access to grass or legume pasture

Despite several studies carried out to investigate the effects of access to pasture on poultry performance, there is a dearth of information on the comparative benefit of grass and legumes. This study investigated the effects of rearing systems [deep litter system (DL), deep litter with access to legumes (LP) or grass (GP) pastures] on the performance of ISA Brown layers. Two hundred and forty 12‐week‐old pullets were housed for this study. They were reared until 60 weeks of age. Eighty birds were assigned to each treatment; each treatment had four replicates of 20 birds each. Two birds per replicate were slaughtered at weeks 20, 35 and 58 for determination of the weights of liver, ovary, oviduct and the number of follicles. Daily egg production records were kept from the day of first egg to 42 weeks in lay. Body weights were recorded weekly. Results indicated that at 20 weeks of age, the hens kept in the LP had higher (p < 0.05) ovary weight (g) (34.98 ± 1.4), oviduct weight (52.55 ± 2.28) and oviduct length (cm) (49.73 ± 11.34), and higher number of large yellow follicles (3.75 ± 1.31) and small yellow follicles (12.75 ± 5.17) than those in the GP (0.83 ± 0.02, 1.68 ± 0.19, 16.38 ± 1.14, 0.00 and 0.00), and DL (1.03 ± 0.11, 1.48 ± 0.48, 14.43 ± 0.58, 0.00 and 0.00) respectively. The age (days) at first oviposition was earlier (p < 0.05) in the LP (139.25 ± 0.85) than that in the GP (146.75 ± 0.48) and DL (146.75 ± 0.48). The hen‐day egg production was lower (p < 0.05) in GP (74.19 ± 1.25) than that in the DL (78.82 ± 0.78) and LP (79.93 ± 1.13) at mid‐laying phase. Concentrate feed intake was lower (p < 0.05) in LP and GP than DL suggesting economic benefit. It was concluded that access to LP enhanced the performance of layers than DL and GP as indicated by the parameters measured.     

舍饲因素对妊娠后期繁殖母羊生产性能影响研究

本项研究的目标是通过试验分析,找出舍饲条件中对繁殖母羊生产性能起主导作用的影响因素,并探索应对措施以指导生产。为此,笔者于2009年末开始在洮南市向阳乡开展了舍饲对母羊生产性能影响要素研究试验。结合我省西部的气候和饲料资源条件,总结试验结果,我们推荐在生产中使用代谢能8.50MJ/kg、粗蛋白9.50%、环境温度＋4℃、饲养密度0.8只/m2、环境湿度60%的参数,对妊娠后期繁殖母羊有较好的增产效果。     

A clinical trial using a regimen which includes a norgestomet implant and norgestomet plus oestradiol valerate injection as a treatment for anoestrus in dairy cows

In seasonally calving dairy herds in the Macalister Irrigation Area of Gippsland, Victoria, cows that had not been observed in oestrus by the start of the mating season and which had inactive ovaries based on rectal palpation and progesterone assay were treated with a hormonal treatment (n = 49). Mature cows had calved at least 40 days previously and 2-year-olds had been calved at least 60 days. The treatment consisted of a norgestomet implant and a norgestomet and oestradiol injection on day 1; prostaglandin analogue Prosolvin) on day 8; withdrawal of implant on day 10 and an injection of PMSG; and fixed time artificial insemination 54 to 56 h after implant withdrawal. This treatment was called the Syncro-mate regimen. Control cows (n = 46) were injected with water on days 1, 8 and 10 and artificially inseminated or served by a bull when seen on heat. Forty seven percent of the treated cows became pregnant within 14 days from the start of treatment compared with 20% of control cows (P less than 0.01). There was an effect of age group on the response to treatment. A greater proportion of 2-year-old cows than mature cows became pregnant within 14 days of treatment (79% of 19 v. 27% of 20; Chi square interaction, treatment by age, 6.4, P less than 0.05). In the younger cows there was also a gain of 22 days in the treatment to conception interval over the control cows (P less than 0.001). It was concluded that the Syncro-mate regimen can be an effective treatment for post partum anoestrus in dairy cows under certain conditions.     

Synchronization of estrus and reproductive performance of ewes treated with synthetic progestogens administered by subcutaneous ear implant or by intravaginal sponge pessary

Experiments were conducted to compare the efficacy of synthetic progestogens administered by subcutaneous ear implant or intravaginal sponge to induce a synchronized estrus in adult ewes and ewe lambs and to evaluate reproductive performance (fertility and litter size) to breeding at the synchronized estrus. Experimental animals were representative of three strains maintained in total confinement and exposed to a synthetic light regimen which alternated at intervals of 4 mo from 18 h day length to 10 h day length/24 h. Treatments were applied at different times of the year at the end of a low light cycle. Implants contained Norgestomet (3 mg) impregnated in a polymethacrylate polymer (Implant H) or impregnated in a silastic polymer containing 1.05 (Implant S1), 1.78 (Implant S2) or 2.60 mg (Implant S3) Norgestomet, respectively. Intravaginal sponges contained 40 mg Fluorogestone Acetate. Implants or sponges were left in situ for 12 d and 500 IU pregnant mares' serum gonadotropin was injected im at the time of removal. Following treatment with Implant H, 96% of ewes were judged to be in estrus at 48 h after implant removal. Fertility of adult ewes and ewe lambs (6 to 7 mo of age at time of breeding) at the synchronized estrus were similar after implant H or sponge treatment, but litter size was higher (P less than .05) for adult ewes treated with sponges. The percentages of adult ewes marked by rams within 60 h after removal of silastic implants or intravaginal sponges were similar. There was a tendency for ewe lambs to be marked later than adult ewes and for adult ewes treated with Implant S1 and Implant S2 to be marked earlier than ewes treated with Implant S3 or sponges. Higher percentages (P less than .05) of adult ewes and ewe lambs lambed to breeding at the synchronized estrus after treatment with Implant S2 or Implant S3, respectively, than after treatment with Implants S2 or sponges.     

Reproductive performance and genetic parameters in first cross ewes from different maternal genotypes

The reproduction of 2,846 crossbreed ewes with 7,899 records is reported. The ewes were progeny of mainly Merino dams and 91 sires from several maternal sire breeds including Border Leicester, East Friesian, Finnsheep, Coopworth, Corriedale, Booroola Leicester, and several others. There were 3 cohorts of ewes at each of 3 sites that were bred naturally to meat-type rams for each of 3 yr to evaluate reproduction and lamb production. At 2 sites, the ewes were mated in the autumn, first at 7 mo of age, and at 2 sites the ewes were mated in the spring, first at 14 or 17 mo of age. The cohorts of ewes and sites were genetically linked by 3 common sires. Mixed linear models were used to analyze ultrasound scanned pregnancy rate, fetal number, fertility (ewes lambing), litter size, lamb survival, number of lambs born (NLBj), number of lambs weaned (NLWj), and total weight of lamb weaned (TWWj) per ewe bred. Fixed effects included sire breed (1 to 10), environment (1 to 4, site and season of breeding: autumn, spring), breeding (1 to 3), cohort (1 to 3), and their interactions. The REML procedures were used to estimate (co)variance components. Ewe sire breed effects were significant (P < 0.01) for all the reproductive traits and breed means ranged from 0.75 to 0.96 for fertility, 1.22 to 2.08 for litter size, 0.70 to 0.90 for lamb survival, 0.99 to 1.66 for NLBj, 0.87 to 1.26 for NLWj, and 22.9 to 33.8 kg for TWWj, with the ranking of sire breeds varying for different traits. For all traits except lamb survival, the contrast between breeding 1 vs. 2 and 3 was considerably greater than the contrast between breeding 2 vs. 3, with significant environment x breeding interactions (P < 0.01). Estimates of heritability for the components of reproduction ranged from 0.03 +/- 0.02 for lamb survival to 0.19 +/- 0.05 for litter size, and those for the composite traits were 0.17 +/- 0.04 for NLBj, 0.13 +/- 0.04 for NLWj, and 0.17 +/- 0.04 for TWWj, with repeatability ranging from 0.10 to 0.19. Genetic and phenotypic correlations among the traits are reported. The significant variation among sire breeds of the crossbred ewes can be used to improve reproduction, although there was a change in the rank of the breeds for the various traits. There was considerable overlap between the breeds, and additional improvement could be achieved by exploiting the genetic variation between sires within breeds for all the ewe reproductive traits.     

Superovulatory response and embryo quality in Katahdin ewes treated with FSH or FSH plus eCG during non-breeding season

The aim of this study was to evaluate the effect of a co-treatment of follicle-stimulating hormone (FSH) plus equine chorionic gonadotrophin (eCG) on serum insulin and insulin-like growth factor 1 (IGF-1) concentrations, superovulatory response, ovulatory rate, and number and production of embryos in Katahdin breed ewes during the non-breeding season. Twenty Katahdin ewes were synchronized with progestagens (CIDR) and assigned to two superovulation treatments (n = 10): (1): ewes treated with 200 mg ewe⁻¹ of FSH from day 5 to 8 after CIDR insertion at decreasing doses every 12 h (FSH group) and (2) ewes treated as FSH group plus 300 IU of eCG on day 5 after CIDR insertion (FSH + eCG group). Estrous behavior was monitored and direct mating was performed. On days − 7 (CIDR insertion), 0 (CIDR withdrawal), and 7 (embryo recovery), blood samples were collected to determine serum hormone concentrations. Co-treatment with eCG (FSH group) did not affect (P > 0.05) serum hormone levels. Superovulation response, ovulation rate, recovery rate, fertilization, and number of embryos were also similar (P > 0.05) between treatments. Compared with FSH group, FSH + eCG ewes had lower (P < 0.05) number of transferable embryos and higher (P < 0.05) number of oocyte and a tendency to increase the number of degenerated embryos (P = 0.07). Overall results suggest that the administration of eCG is not beneficial either to improve the ovulatory response or the amount of transferable embryos in Katahdin ewes superovulated with a protocol using progesterone and FSH at decreasing doses.

     

Intervals from norgestomet withdrawal and injection of equine chorionic gonadotropin or P.G. 600 to estrus and ovulation in ewes

Synchronization of estrus and ovulation is essential for AI of ewes during a predetermined time frame, and progestogen-eCG treatments are typically used to prepare the ewes. However, eCG is not readily available in the United States, but P.G. 600 (400 IU of eCG and 200 IU of hCG) is available. Thus, we conducted a study to determine the effects of eCG and P.G. 600 on the timing of estrus and ovulation after progestogen withdrawal. Ewes were assigned to two replicates of an experiment with the following treatments: 1) 3-mg norgestomet implant (i.e., one-half of a Syncro-Mate-B [SMB] implant) for 10 d, plus 2 mL of saline i.m. at SMB removal (n = 11); 2) 3-mg SMB implant for 10 d, plus 400 IU of eCG i.m. at SMB removal (n = 13); and 3) 3-mg SMB implant for 10 d, plus P.G. 600 i.m. at implant removal (n = 9). On d 6 after SMB insertion, PGF2alpha was used to induce luteolysis. Beginning 12 h after implant removal, vasectomized rams were used at 12-h intervals to check for estrus. When a ewe was detected in estrus, each ovary was evaluated ultrasonically. Ovaries were evaluated again 16 h later and then at 8-h intervals until ovulation. Treatment altered the interval from implant removal to estrus (less [P < 0.05] in SMB + eCG than in the other two groups) and to ovulation (greatest [P < 0.05] in SMB). However, the treatment x replicate interaction was significant for the intervals from implant removal to estrus (P < 0.03) and from implant removal to ovulation (P < 0.05). An inconsistent response in the SMB-treated ewes seemed to be primarily responsible for the interaction. The intervals to estrus and to ovulation for the SMB-treated ewes were shorter (P < 0.05) in Replicate 1 than in Replicate 2. Also, both intervals seemed to be less consistent between replicates for the SMB + P.G. 600- than for the SMB + eCG-treated ewes; that is, eCG seemed to increase the predictability of the intervals to estrus and to ovulation. Neither the main effects of treatment and replicate nor their interaction were significant for the interval from estrus to ovulation (38.4 /- 3.3 h), size of the ovulatory follicle (7.7 +/- 0.8 mm), or ovulation rate (1.6 +/- 0.2). We concluded from this experiment that eCG is a better choice than P.G. 600 as the gonadotropin to use at the time of progestogen withdrawal to prepare ewes for AI during a predetermined interval.     

Reproductive performance of seasonal ewes and does fed dry fat during their postpartum period

This study was carried out to evaluate the effect of feeding a dry fat source to seasonal ewes and does on their postpartum reproductive performance. Forty five multiparous Awassi ewes (LW = 60.1 ± 3.2 kg) and 45 Shami does (LW = 49.6 ± 2.4 kg) were randomly assigned into 3 dietary treatments (n = 15/spp) for 60 days postpartum in a completely randomized design (CRD) set. Females were housed with their offsprings and fed one of three isonitrogenous total mixed rations (TMR) containing 0, 3, or 5% of dry fat. Blood samples were taken individually every 3 days to determine serum progesterone concentration levels starting one week postparturition via radioimmunoassay kits. Progesterone concentrations increased (P < 0.05) in ewes fed 3% fat addition but not for 5% level. Meanwhile, those of doe were not affected by adding supplemental fat. No differences were observed in days to 1st or 2nd postpartum ovulation in both species. Milk production was higher (P < 0.05) for fat treated ewes with no differences between the 2 fat levels, while it was not different among does groups. Final live weight of females in both species was also not affected by fat supplementation. However, live weight changes were higher (P < 0.05) for ewes with no differences between 3% fat level and control groups, and lower in does with increased fat level and with no differences between the 2 treatment groups. Weaning weight and average daily gain of the newborn in both species were not affected by fat supplementation. Litter weight was not different for ewes, but it was higher (P < 0.05) for treated does with no differences between 3% and 5% supplemented fat groups. Therefore, one can conclude that supplemental fat to ewes at 3% during their postpartum period might recover their cyclicity late in the breeding season, but not at high levels (5%), and can improve their milk production and affect live weight change during that period with no effect on weaning weight or litter weight of lambs. For does, supplemental fat is not capable of affecting their postpartum cyclicity, milk production, and weaning weight of their kids, but reduces their live weight change and litter weight.     

Luteal function and reproductive response in suckled beef cows after metestrus administration of a norgestomet implant and injection of estradiol valerate with various dosages of injectable norgestomet.

In an experiment replicated over 2 yr, 149 suckled beef cows were administered Syncro-Mate-B (SMB), a 6-mg Norgestomet (NOR) ear implant (in situ 9 d) in conjunction with an i.m. injection of 5 mg of estradiol valerate (EV), and either 3.0, 4.5, or 6.0 mg of NOR, 2 d after estrus. All cows were artificially inseminated at 48 h (timed insemination; TI) after implant removal (IR) and cows were reinseminated at any estrus subsequent to 24 h of TI through 30 d. Blood samples collected before treatment, every 3 d through IR, and at TI were assayed for progesterone (P4). At TI, 44, 39, and 12% of cows treated with 3.0, 4.5, or 6.0 mg of NOR, respectively, had serum concentrations of P4 greater than 1 ng/mL (3.0 and 4.5 mg vs 6.0 mg, P less than .01). Fifty-eight, 63, and 84% of cows treated with 3.0, 4.5, or 6.0 mg of NOR, respectively, exhibited a synchronized (within 5 d of IR) estrus (3.0 and 4.5 mg vs 6.0 mg, P less than .05). Pregnancy rates for the 5-d synchronized period were 38, 45, and 66% for cows treated with 3.0, 4.5, or 6.0 mg of NOR, respectively (3.0 and 4.5 mg vs 6.0 mg, P less than .05). First-service pregnancy rates were 66, 71, and 79% for cows treated with 3.0, 4.5, or 6.0 mg of NOR, respectively (P greater than .10).(ABSTRACT TRUNCATED AT 250 WORDS)     

冷季补饲对放牧后备母羊生产性能和血液生化指标的影响

为研究放牧地区冷季后备母羊适宜的补饲配方,试验选取体重相近的8月龄阿勒泰后备母羊40只,随机分为4组,每组10只,在放牧条件下,补饲组每只羊每日补饲精料350 g,设置全价日粮瘤胃可降解氮（RDN）:可发酵有机物（FOM）分别为35、30和25共3组,记作R:F₃₅组、R:F₃₀组和R:F₂₅组,对照组不补饲,试验期45 d。结果表明：1)试验末期,R:F₃₅组、R:F₃₀组、R:F₂₅组的体重较对照组分别提高了20.48%、19.24%和17.90%,差异极显著（P <0.01）;日增重较对照组极显著提高（P <0.01）。2) R:F₃₅组、R:F₃₀组极显著提高了试验羊的血清葡萄糖（GLU）(P <0.01)。3) R:F₃₅组、R:F30组的血清尿素氮（SUN）含量显著高于对照组（P <0.05）,R:F₃₅组的谷丙转氨酶（ALT）显著高...     

Reproductive performance of anovulatory anoestrous postpartum dairy cows following treatment with two progesterone and oestradiol benzoate-based protocols, with or without resynchrony

AIMS: (a) To compare the reproductive performance of anovulatory anoestrous (AA) postpartum dairy cows following treatment with 1 of 2 progesterone (P4) and oestradiol benzoate (ODB)-based treatment regimens; (b) To determine whether resynchronisation of cows initially treated for AA would improve reproductive performance and; (c) to determine whether cows not detected in oestrus but with a corpus luteum (CL) present (NDO/CL+), treated with P4 and ODB, would conceive earlier than untreated controls. METHODS: Cows (n=1386) from 11 herds, that had not been detected in oestrus before the start of the seasonal mating period (PSM) and in which a CL was not detected were diagnosed AA, blocked by age (2 or >2 years old), then randomly assigned to be treated with an intravaginal P4-releasing device for either 6 (6-Day group) or 8 days (8-Day group). Cows in the 8-Day group were injected intramuscularly (IM) with 2 mg ODB at device insertion and all cows were injected with 1 mg ODB 24 h after device removal (Day 0). Cows detected in oestrus from Days 0-3 were subsequently assigned to be either resynchronised or left as untreated controls. Resynchronised cows had a used P4-releasing device reinserted on Day 14 for 8 days and were injected with 1 mg ODB at device reinsertion and again 24 h after device removal. NDO/CL+ cows were assigned to be either treated the same as the 8-Day group or left as untreated controls. All cows were inseminated on detection of oestrus and pregnancy tested approximately 10 weeks after the PSM and again 6-8 weeks after the end of the mating period. RESULTS: For AA cows, the 14-day submission rate was similar between 6-Day and 8-Day groups (p0.1). However, the pregnancy rate by Day 14 was higher for the 8-Day than the 6Day group (43.0% vs 35.2%; p=0.006). Resynchrony treatment decreased the 14-day pregnancy rate compared with untreated controls (35.2% vs 42.5%; p=0.026). The resynchrony treatment increased the submission rate between Days 14-28 for non-pregnant cows compared with untreated controls (80.6% vs 57.4%; p=0.049). However, conception rate to resynchronised heats was lower than for cows that returned to oestrus naturally (56.6% vs 67.9%; p=0.025). Neither initial treatment type nor resynchrony treatment increased the 28-day pregnancy rate (p>0.1). There were no differences between treatment groups in the final non-pregnant rate (4.5% vs 4.6%; p>0.1). Treated NDO/CL+ cows had a higher 14-day submission rate (88.1% vs 49.4%; p>0.001), higher 14-day and 28-day pregnancy rates (42.9% vs 20.7%, p>0.001 and; 56.0% vs 42.5%, p=0.094, respectively) and conceived earlier (21 vs 36 days from PSM to median day of conception; p>0.05), than untreated NDO/CL+ cows. CONCLUSIONS: The 8-Day, ODB-P4-ODB treatment regimen resulted in a higher pregnancy rate by 14 days but not 28 days than the 6-Day, P4-ODB treatment. The resynchrony treatment increased the proportion of non-pregnant cows inseminated on days 14-28, but did not increase the 28-day pregnancy rate or final pregnancy rate. Treatment of NDO/CL+ cows with the 8-Day, ODB-P4-ODB treatment improved reproductive performance compared with no treatment.     

Reproductive performance of sows with and without PRRS modified live virus vaccination in PRRS-virus-seropositive herds

Porcine reproductive and respiratory syndrome (PRRS) virus infection causes reproductive failures including return to oestrus, abortion, mummified foetuses, stillborn, and weak-born piglets. The objective of the present study was to investigate reproductive performance of sows in PRRS-virus-seropositive herds with and without PRRS modified live virus (PRRS-MLV) vaccination. The study was conducted in 20 PRRS-virus-seropositive commercial swine herds in Thailand. The data included 211,009 mating and 180,935 farrowing records. The analysed variables included farrowing rate (FR), return rate (RR), abortion rate (AR), total number of piglets born per litter (TB), number of piglets born alive per litter (BA), percentage of stillborn (SB), percentage of mummified foetuses (MM), and number of piglets weaned per litter (WP). The results revealed that FR in non-vaccinated sows was lower than that in vaccinated sows (85.0 vs 89.7 %, respectively, P?<?0.001), and RR in non-vaccinated sows was higher than that in vaccinated sows (6.9 vs 3.7 %, respectively, P?<?0.001). AR did not differ significantly between non-vaccinated and vaccinated sows (1.6 and 2.0 %, respectively, P?=?0.964). TB (11.2 and 11.5, respectively, P?<?0.001), BA (10.0 and 10.6, respectively, P?<?0.001), and WP (9.2 and 9.6, respectively, P?<?0.001) in non-vaccinated sows were lower than those in vaccinated sows. SB (6.9 and 5.1 %, respectively, P?<?0.001) and MM (3.2 and 2.2 %, respectively, P?<?0.001) in PRRS-MLV-vaccinated sows were higher than those in non-vaccinated sows. The improvement in sow reproductive performance in PRRS-MLV-vaccinated herds was most pronounced in gilts and primiparous sows.     

Assessment of stability of ketamine-xylazine preparations with or without acepromazine using high performance liquid chromatography-mass spectrometry

The objective of this study was to evaluate the stability of 3 distinct preparations of ketamine and xylazine, with or without acepromazine, stored at room temperature or at 4°C for 1, 2, and 3 mo. Drug concentrations were compared to fresh solutions, using a high performance liquid chromatography-mass spectrometry/selected-ion monitoring (HPLC-MS/SIM) assay. The concentrations of ketamine and xylazine, diluted in physiological saline, did not change over time at room temperature or at 4°C. However, acepromazine concentrations decreased over time when stored at room temperature. In contrast, undiluted ketamine-xylazine preparations gradually decreased in concentration when stored at room temperature. All of the drug concentrations remained above 90% of their original concentration when stored at 4°C. In conclusion, when diluted in physiological saline, ketamine-xylazine cocktails can be stored for 3 mo, whereas undiluted cocktails can lose efficacy over 3 mo at room temperature. Storage at 4°C could preserve drug stability.     

Reproductive performance and profitability of heifers fed to weigh 272 or 318 kg at the start of the first breeding season

Reproductive performance and weaning weight of the first calf was determined in 221 Brahman crossbred heifers fed to weigh either 272 (TW1) or 318 kg (TW2) at the start of their first breeding season (target weight). Heifers were divided into light- (below average) and heavyweight (above average) groups on the basis of initial weight. Within each target weight, heifers were fed in three lots. One lot contained lightweight heifers, the second contained heavy heifers and the third was composed of one-half heavy- and one-half lightweight heifers. Heifers were fed for 200 d before the start of the first breeding season. More heifers in TW2 showed estrus and became pregnant in the first 20 d of the breeding season and more were pregnant at the end of the first breeding season. These same differences in reproductive performance were also noted the second year. Each heifer exposed in TW2 weaned 43.4 kg more calf than those in TW1. An average heifer in TW2 was fed 220 kg more corn and 100 kg less hay than a corresponding heifer in TW1. Estrus and pregnancy rate for lightweight heifers in TW1 and TW2 were not improved by sorting and feeding them separately.     

Reproductive response of ewes to immunization with Fecundin (ovandrotone)

Ewes of five crossbred genotypes (total of 221 ewes) were immunized with a commercial preparation of androstenedione-7HSA in DEAE dextran adjuvant in a 2-yr trial. In yr 1 ewes were allocated within genotype to a 2 x 2 application of immunization and premating flushing. In yr 2 they were allocated within previous Fecundin treatment into either Fecundin-treated or control groups. First-time immunization with Fecundin increased ovulation rate by .70 ova/ewe in yr 1 and by .85 ova/ewe in yr 2 (P less than .05). Ewes treated in both years produced fewer ova than those treated in the 2nd yr only (P less than .05), but they did not differ in litter size. Although Fecundin reduced conception to first mating, the overall conception rate was not affected. Litter size of treated ewes was increased by .19 and .38 lambs/ewe lambing (P less than .05) in yr 1 and yr 2, respectively. Fecundin treatment in yr 1 produced a carry-over effect in yr 2 by increasing litter size by .26 lamb/ewe (P less than .05) while reducing conception to first mating. The litter size of ewes with two ovulations was reduced by Fecundin treatment in yr 1 (P less than .05) but showed no consistent pattern in yr 2. Overall, ewes with two ovulations produced .7 to .8 more lambs than ewes with one ovulation, and ewes with three ovulations produced .4 more lambs than those with two ovulations. Ewes of different genotypes did not differ in their response to Fecundin.