Beef cattle husbandry practices across Ecoregions of Canada in 2011

Sheppard, S. C., Bittman, S., Donohoe, G., Flaten, D., Wittenberg, K. M., Small, J. A., Berthiaume, R., McAllister, T. A., Beauchemin, K. A., McKinnon, J., Amiro, B. D., MacDonald, D., Mattos, F. and Ominski, K. H. 2015. Beef cattle husbandry practices across Ecoregions of Canada in 2011. Can. J. Anim. Sci. 95: 305–321. Beef production in Canada is diverse in many dimensions with numbers of cattle per operation ranging over 10 000-fold, pasture usage from nil to 100%, and types of operations from solely cow–calf to exclusively feedlot finishing. This study summarizes management information obtained from a survey conducted in 2012 (about 2011) on 1009 beef operations in Canada. Many of the results clearly differentiate the practices in the Prairies from those in Ontario and Quebec. Compared to eastern Canada, the Prairies had earlier and shorter calving seasons, higher weaning weights, utilized more winter grazing with a variety of strategies, grew and fed more barley than corn, used more seasonal feeding areas and feedlots (and hence fewer barns), and more commonly spread manure in the fall. Many of the management practices used by cow–calf operations would have low environmental impact, including extensive use of grazing even in winter, low fertilizer inputs and feeding perennial forages with a high content of legumes. Some practices such as not covering forages or manure storage structures were common and could be changed to improve forage quality and reduce manure emissions. Most forage was harvested 3–7 d after full bloom. Earlier harvest has the potential to improve forage quality, which could reduce dependence on arable crops. Finishing operations used more housing, fed more arable-land crops and less perennial forages, and practiced little grazing. Rationale regarding the adoption of many of the management strategies was reported by the producers. For example, winter grazing was adopted primarily to reduce costs and labour, but for some it was also linked to a late calving season. Preferred sources of technical information included their own experience, farm print media, producer organisations and demonstrations at field days. The survey also identified several areas in which the industry may realize improved sustainability.

Effects of presynchronization and eCG on pregnancy rates to GnRH-based, fixed-time artificial insemination in beef heifers

Three experiments were conducted to determine the effects of presynchronization and treatment with equine chorionic gonadotropin (eCG) on corpus luteum (CL) and ovarian follicular development, plasma progesterone concentrations, and pregnancy rates in beef heifers subjected to a gonadotropin releasing hormone (GnRH)-based, fixed-timed AI (TAI) protocol. All heifers were given GnRH on day 0, prostaglandin F2α (PGF) on day 7, and a second GnRH on day 9 concurrent with TAI (54 h after PGF). In exp. 1 (N = 148), presynchronization with PGF (days -22 and -11) decreased the percentage of heifers with non-luteal plasma progesterone concentrations on day 0 (5.4 vs 29.7%) and day 7 (0 vs 11.6%; P < 0.05), but not on day 9 (74.3 vs. 66.2%; P > 0.20), and reduced the number of heifers in estrus and bred before TAI (P < 0.05). Although presynchronization reduced preovulatory follicle diameter (12.9 ± 0.3 vs. 14.9 ± 0.3 mm; mean ± SEM; P < 0.01), it did not affect TAI pregnancy rates (36.5 vs. 29.7%; P > 0.20). In exp. 2, heifers (N = 128) were presynchronized with melengestrol acetate (MGA) (days -27 to -12), and received a controlled internal drug release (CIDR) on day 0; on day 7, half were given 300 IU of eCG at CIDR removal. Treatment with eCG tended to increase preovulatory follicle diameter in heifers that did not ovulate to GnRH on day 0 (P = 0.06), but did not affect the percentage of heifers with non-luteal plasma progesterone concentrations on day 9 (57.8 vs. 57.8%) or TAI pregnancy rates (48.4 vs. 53.1%; P > 0.20). Experiment 3 was a 2 × 2 factorial arrangement of presynchronization (PGF concurrent with a CIDR on day -7) and eCG treatments (on day 7) applied to heifers in three herds (A, N = 150, B, N = 260 and C, N = 40). All heifers had a once-used CIDR from days 0 to 7. Presynchronization increased the percentage of heifers (Herd A) with low-luteal plasma progesterone concentrations on day 0 (70.7 vs. 22.7%) and day 7 (90.7 vs. 53.3%; P < 0.01), but did not affect the percentage of heifers with non-luteal concentrations of progesterone on day 9 (97.3 vs. 93.3%; P > 0.20). Combined for all herds, presynchronization reduced the prevalence of a CL on day 0 (23.5 vs. 73.7%; P < 0.01), and increased the prevalence of follicles ≥ 10 mm on day 7 (96.8 vs. 86.7%; P < 0.01); however, TAI pregnancy rates (195/439 = 44.4%) were not improved by either presynchronization or eCG treatment (P > 0.20).Key words: Presynchronization, equine chorionic gonadotropin, GnRH, fixed-time artificial insemination, progesterone

Core body temperature monitoring with passive transponder boluses in beef heifers

Experiments were conducted over 82 d (Nov. 04 to Jan. 24, 49°N, mean ambient temperature -3.6 to -12.6 ± 1.6°C) to determine the effects of fever, photoperiod and pen setup on the rate (MR) and frequency (MF) with which heifers were monitored and the body (rumen) temperatures (BTr) obtained with a cattle temperature moniotoring system (MaGiiX). Magnetic, inductively coupled full duplex radio-frequency identification (RFID) transponder boluses containing thermistors were administered per os to 72 heifers (7.9 ± 0.5 mo of age and 283 ± 23 kg body weight) housed in one of four pens, in outdoor shed-lot facilities, each with a panel reader co-located with the waterbowl. A mixed ration (59% dry matter) was provided at 1500 daily. Fencing was arranged within pens for water motivated (WM) acquisitions during exps. 1 (Initial), 2 (Fever) and 3 (Photoperiod), or for either WM or activity motivated (AM) acquisitions during exp. 4 (Pen setup). Overall, most heifers were monitored daily (Mode MR 100%), several times perday (MF 7.8 ± 0.5), mostly during the afternoon and evening rather than night and morning 6-h periods, and BTr (37.8 ± 0.2°C, range 22 to 42°C) were usually lower (P < 0.05) for the afternoon than night. A 2°C increase in mean BTr caused by fever was detected (P < 0.05) when monitoring was scheduled rather than unscheduled. Extended (16h) in contrast to natural (8h) photoperiod increased (P < 0.05) evening MR (96.8 vs.83.5 ± 1.9%) and MF (3.8 vs. 2.5 ± 0.2), and morning-BTr (38.0 vs. 37.4 ± 0.11°C). Pen setup for AM in contrast to WM acquisitions increased (P < 0.05) MR and MF and BTr (by 1°C) in all periods of the day. The technology has excellent potential for non-invasive monitoring of BTr in heifers. Key words: Radio-frequency identification, cattle, transponder bolus, body temperature, rumen

Effects of flaxseed supplementation on endometrial expression of ISG17 and intrauterine prostaglandin concentrations in primiparous dairy cows submitted to GnRH-based synchronized ovulation

The objective of the experiment was to determine the effects of feeding whole flaxseed on ovarian function and uterine concentration of prostaglandins on the 17th day post-ovulation. Fortyeight primiparous Holstein cows averaging 550 kg of body weight (BW) were allotted at 2 wk postpartum to two groups of 24 animals: a control diet with no added fat (CON) or a diet with 9% whole flaxseed (FLA). At 6 wk postpartum cows were subjected to a Presynch-Ovsynch protocol with and without artificial insemination on day 0. Real-time transrectal ultrasonography and plasma progesterone concentrations were used to evaluate ovarian function. On day 17, uterine flushings and biopsies of uterine endometrium were collected. Synchronized ovulation rates based on low and high plasma progesterone concentrations on days 0 and 7, respectively, were the same for cows fed CON and those fed FLA (87.5 vs. 87.5%). The 13,14-dihydro-15-keto-PGF2α (PGFM) to prostaglandin E metabolite (PGEM) ratio in uterine flush was significantly higher for non-inseminated cows fed CON (32.0) than for non-inseminated cows fed FLA (17.5) and there was no difference between pregnant cows fed CON (12.2) and those fed FLA (12.0). Feeding flaxseed before breeding may contribute to increased fertility by improving uterine conditions for embryo survival. Key words: Flaxseed, dairy cattle, ovarian function, prostaglandins

18 THE EFFECTS OF CIDR AND eCG TREATMENTS IN A GnRH-BASED PROTOCOL FOR TIMED AI OR EMBRYO TRANSFER ON PREGNANCY RATES IN LACTATING BEEF COWS

Two experiments were conducted to determine the effects of the addition of a progestin, equine chorionic gonadotropin (eCG), or both, in a GnRH-based protocol for timed AI (TAI) or timed embryo transfer (TET). In both experiments, Angus, Gelbvieh, and Simmental cross-bred cows were randomized by breed and postpartum interval [50 � 10 days (mean � SD); range, 27 to 89] into 4 groups in a 2 � 2 factorial design. All injections were given IM. In Experiment 1, 288 cows (89.6% cycling) were given 25 mg dinoprost (PGF; Lutalyse�; Pfizer Animal Health, Montreal, Quebec, Canada) on Day –11; on Day 0, they were given 100 �g GnRH (Cystorelin�; Merial Canada, Pointe-Claire, Quebec, Canada), with or without concomitant insertion of a CIDR (1.9 g progesterone; Pfizer Animal Health, Montreal, Quebec, Canada). On Day 7, CIDR inserts were removed and cows were given PGF, with or without concomitant injection of 400 IU of eCG (Pregnecol�; Bioniche Animal Health, Belleville, Ontario, Canada). On Day 9 (54-56 h after PGF), TAI was done, with concomitant injection of 100 �g GnRH. Ultrasonographic examination of 147 cows on Day 7 revealed that 62.4% had ovulated in response to the first GnRH. Pregnancy rates (ultrasonographic examination) on Day 38 did not differ between cows with or without a CIDR (52.9 and 51.4%, rspectively; P ≥ 0.64), with or without eCG treatment (53.5 and 50.7%, respectively; P ≥ 0.28), in cycling vs. anestrous cows (51.6 vs 56.7%, respectively; P ≥ 0.76), and in cows that had ovulated (58.1%) or did not ovulate (50.0%) after the first GnRH treatment (P ≥ 0.58). In Experiment 2, 151 cows were given 500 �g cloprostenol (PGF; Estrumate�; Schering–Plough Animal Health, Pointe-Claire, Quebec, Canada) on Day –12, 100 �g GnRH on Day 0, with or without concomitant insertion of a CIDR. On Day 3, half of the cows were given 400 IU eCG. On Day 7, CIDRs were removed and cows were given PGF; on Day 9 (54–56 h after PGF), all cows were given 100 �g GnRH. On Day 15, ultrasonography was done to select suitable recipients for transfer of frozen–thawed embryos on Day 16 (part of another experiment, balanced across synchronization groups). Recipient selection rates did not differ whether cows received or did not receive a CIDR (93.4% vs 85.5%, respectively; P ≥ 0.27) or eCG (91.0 vs 87.8%, respectively; P ≥ 0.67). In addition, pregnancy rates on Day 43 did not differ whether cows received or did not receive a CIDR (32.3 vs 32.4%, respectively; P ≥ 0.52) or eCG (35.2 and 29.2%, respectively; P ≥ 0.21). In summary, the addition of a CIDR or eCG to a GnRH-based synchronization protocol initiated after PGF presynchronization in lactating beef cattle yielded no improvement in pregnancy rates following TAI, or recipient selection and pregnancy rates following TET.

Lower Pregnancy Losses in Lactating Dairy Cows Fed a Diet Enriched in α-Linolenic Acid

The objectives were to determine if a diet enriched in alpha-linolenic acid (ALA) would influence ovarian function, early embryo survival, conception rates, and pregnancy losses in lactating dairy cows. Beginning 28 d before breeding, Holstein cows (55 +/- 22 d postpartum; mean +/- SD) were assigned to diets supplemented with either rolled flaxseed (FLAX; 56.7% ALA, n = 62) or rolled sunflower seed (SUNF; 0.1% ALA, n = 59) to provide approximately 750 g of oil/d. Diets continued for 32 d after timed artificial insemination (TAI, d 0) following a Presynch/Ovsynch protocol. Barley silage- and barley grain-based TMR were formulated to meet or exceed National Research Council requirements. Metabolizable protein and net energy for lactation concentrations were similar in the 2 diets. Based upon a mean dry matter intake of 22 kg/d, cows fed FLAX or SUNF consumed > 410 g or < 1 g of ALA, respectively. Pregnancy was confirmed by ultrasound 32 d after TAI. Nonpregnant cows were placed on a second Ovsynch regimen and reinseminated 42 d after first TAI, and received oilseeds for 32 d after second TAI. Relative to prediet levels, FLAX increased the ALA content of milk by 187%. Ovarian ultrasonography was performed in 8 cows per diet; the mean diameter of ovulatory follicles was larger in cows fed FLAX compared with SUNF (16.9 +/- 0.9 vs. 14.1 +/- 0.9 mm), but follicle number, corpus luteum size, and plasma progesterone concentrations remained unaffected. Presumptive conception (progesterone < 1 ng/mL on d 0 and > 1 ng/mL on d 21) rates to first TAI were greater in FLAX than in SUNF (72.6 vs. 47.5%). Pregnancy losses were lower in cows fed FLAX (9.8%) compared with those fed SUNF (27.3%). Including flaxseed in the ration of dairy cows increased the size of the ovulatory follicle and reduced pregnancy losses.

Resynchronization of previously timed-inseminated beef heifers with progestins

The objective was to determine the efficacy of a previously used CIDR or melengestrol acetate (MGA; 0.5mg/head/day) for resynchronization of estrus in beef heifers not pregnant to timed-AI (TAI). In three experiments and a field trial, heifers were reinseminated 6-12 h after first detection of estrus. Pregnancy diagnosis was done from approximately 25-43 days after either TAI or reinsemination. In Experiment 1, 79 heifers received a once-used CIDR from 13 to 20 days after TAI and 80 heifers were untreated controls. For these two groups, there were 34 and 35 heifers, respectively, not pregnant to TAI; median +/- S.E. intervals from TAI to onset of estrus were 22 +/- 0.2 days versus 20 +/- 0.6 days (P < 0.001); estrus rates were 70.6% versus 85.7% (P = 0.1); conception rates were 62.5% versus 76.7% (P < 0.3); and pregnancy rates were 44.1% versus 65.7% (P = 0.07), for CIDR and untreated (control) groups, respectively. In Experiment 2, heifers (n = 651) were TAI (Day 0) and 13 days later randomly assigned to one of seven groups (n = 93 per group) to receive a once-used CIDR (three groups; Days 13-20), MGA (three groups; Days 13-19), or no treatment (control group). Groups given a CIDR or MGA also received: no further treatment (CIDR or MGA alone); 1.5mg estradiol-17beta (E-17beta) and 50 mg progesterone (P4) in 2 mL canola oil on Day 13; or E-17beta and P4 on Day 13 and 0.5 mg E-17beta on Day 21 (24 h after CIDR removal or 48 h after the last feeding of MGA). Pregnancy rate to TAI was lowest (P < 0.05) for the group given a CIDR plus E-17beta and P4 on Day 13 and E-17beta on Day 21. Variability in return to estrus was greater (P < 0.001) in the control and MGA groups than in CIDR groups. Conception and pregnancy rates in heifers given a CIDR (65.1 and 61.4%) were higher (P<0.01) than those fed MGA (49.6 and 40.4%), but not different from controls (62.2 and 54.9%, respectively). In Experiment 3, 616 heifers received a once- or twice-used CIDR for 7 days, beginning 13+/-1 days after TAI, with or without a concurrent injection of 150 mg of P4 (2 x 2 factorial design). Pregnancy rate to TAI was 47.2%. In heifers that returned to estrus, there was no significant difference between a once- or twice-used CIDR for rates of estrus (68.8%, P < 0.3), conception (65.9%, P < 0.6) and pregnancy (45.3%, P < 0.8). Injecting progesterone at CIDR insertion increased the median interval from CIDR removal to onset of estrus (P < 0.05) and reduced rates of estrus (63.8% versus 73.8%, P<0.05), conception (60.5% versus 70.6%, P = 0.1) and pregnancy (38.6% versus 52.2%, P < 0.02). In a field trial, 983 heifers received a once-used CIDR for 7 days, beginning 13 +/- 1 days after TAI. Pregnancy rate to TAI was 55.2%. The median (and mode) of the interval from CIDR removal to estrus was 2.5 days. Estrus, conception and pregnancy rates were 78.2, 70.3 and 55.0% (overall pregnancy rate to TAI and rebreeding, 78.7%). In summary, a once- or twice-used CIDR for 7 days, starting 13 +/- 1 days after TAI resulted in the majority of nonpregnant heifers detected in estrus over a 4-day interval, with acceptable conception rates; however, injecting progesterone at CIDR insertion significantly reduced both estrus and pregnancy rates, and estradiol treatment after CIDR removal was associated with a decreased pregnancy rate to TAI. Fertility was higher in heifers resynchronized with a once-used CIDR than with MGA.

Effect of once daily 5-h or 10-h cold-exposures on body temperature and resting heat production of beef cattle

Twelve yearling crossbred beef heifers weighing 454 ± 31 kg were randomly assigned to either 0 h (control), 5 h (5CE; 0800 to 1300) or 10 h (10CE; 0800 to 1800) of cold exposure (-20°C) daily to determine the effect of daily cold exposures of different durations on body core temperature and resting heat production of beef cattle. Treatments were imposed for a 21-d period (seven intervals of 3 d duration) using two replications with two heifers per treatment × replication combination. Heifers were group housed outdoors in a pen with overhead shade at one end and were moved daily at 0800 to a group pen in either a control room or an environmental chamber set at -20°C. After the 21-d period was completed, resting heat production was measured in a thermal neutral environment for 5 h. Vaginal temperature (Tvag) was continuously monitored using radiotransmitters. Treatment did not affect daily maximum, mean or minimum Tvag, the amount of time spent at Tvag exceeding daily mean Tvag, or the variability of Tvag (P ≥ 0.29). However, when examined within specific phases of the day, treatment effects on Tvag were found. Tvag was elevated 0.24°C (5CE) and 0.35°C (10CE) during the daily first 5 h of cold-exposure (10CE = 5CE > control; P = 0.02) throughout the entire 21-d trial. During other times of the day there was no effect of treatment on Tvag but treatment × interval was significant (P ≤ 0.02) during the 6–10 h from initiation of cold-exposure when the 10CE group remained in the cold but the 5CE group had been returned to the outdoor pen. The Tvag of the 10CE and 5CE heifers was elevated at this time of day compared to control heifers, but only during the first 4 to 6 d (5CE) or 7 to 9 d (10CE) of the trial. These results indicate that thermoregulatory mechanisms that control core body temperature undergo habituation and the timecourse of habituation depends on the duration of daily cold- exposure. Resting heat production was unaffected by the two durations of cold-exposure examined (P = 0.55), suggesting that metabolic acclimation does not occur in response to intermittent cold-exposure of beef cattle. Key words: Beef heifers, vaginal temperature, resting heat production, environment, cold duration

Effect of estradiol valerate on ovarian follicle dynamics and superovulatory response in progestin-treated cattle

Three experiments evaluated the effects of estradiol valerate (EV) on ovarian follicular and CL dynamics, intervals to estrus and ovulation, and superovulatory response in cattle. Experiment 1 compared the efficacy of two norgestomet ear implants (Crestar and Syncro-Mate B; SMB) for 9 d (with PGF at implant removal), combined with either 5 mg estradiol-17beta and 100 mg progesterone (EP) or 5 mg EV and 3mg norgestomet (EN) im at the time of implant insertion on CL diameter and follicular wave dynamics. Ovaries were monitored by ultrasonography. There was no effect of norgestomet implant. Diameter of the CL decreased following EN treatment (P < 0.01). Mean (+/- S.D.) day of follicular wave emergence (FWE) was earlier (P < 0.0001) and less variable (P < 0.0001) in EP- (3.6 +/- 0.5 d) than in EN- (5.7 +/- 1.5 d) treated heifers. Intervals from implant removal to estrus (P < 0.001) and ovulation (P < 0.01) were shorter in EN- (45.7 +/- 11.7 and 74.3 +/- 12.6 h, respectively) than in EP- (56.4 +/- 14.1 and 83.3 +/- 17.0 h, respectively) treated heifers. Experiment 2 compared the efficacy of EP versus EN in synchronizing FWE for superovulation in SMB-implanted cows. At random stages of the estrous cycle, Holstein cows (n = 78) received two SMB implants (Day 0) and were randomly assigned to receive EN on Day 0 or EP on Day 1. Folltropin-V treatments were initiated on the evening of Day 5, with PGF in the morning and evening of Day 8, when SMB were removed. Cows were inseminated after the onset of estrus and embryos were recovered 7 d later. Non-lactating cows had more CL (16.7 +/- 11.3 versus 8.3 +/- 4.9) and total ova/embryos (14.7 +/- 9.5 versus 7.9 +/- 4.6) than lactating cows (P < 0.05). EP-treated cows tended (P = 0.09) to yield more transferable embryos (5.6 +/- 5.2) than EN-treated cows (4.0 +/- 3.7). Experiment 3 compared the effect of dose of EV on ovarian follicle and CL growth profiles and synchrony of estrus and ovulation in CIDR-treated beef cows (n = 43). At random stages of the estrous cycle (Day 0), cows received a CIDR and no further treatment (Control), or an injection of 1, 2, or 5 mg im of EV. On Day 7, CIDR were removed and cows received PGF. Follicular wave emergence occurred within 7 d in 7/10 Control cows and 31/32 EV-treated cows (P < 0.05). In responding cows, interval from treatment to FWE was longer (P < 0.05) in those treated with 5 mg EV (4.8 +/- 1.2 d) than in those treated with 1 mg (3.2 +/- 0.9 d) or 2 mg (3.4 +/- 0.8 d) EV, while Control cows were intermediate (3.8 +/- 2.0 d). Diameter of the dominant follicle was smaller (P < 0.05) at CIDR removal and tended (P = 0.08) to be smaller just prior to ovulation in the 5 mg EV group (8.5 +/- 2.2 and 13.2 +/- 0.6 mm, respectively) than in the Control (11.8 +/- 4.6 and 15.5 +/- 2.9 mm, respectively) or 1mg EV (11.7 +/- 2.5 and 15.1 +/- 2.2 mm, respectively) groups, with the 2mg EV group (10.7 +/- 1.5 and 14.3 +/- 1.7 mm, respectively) intermediate. Diameter of the dominant follicle at CIDR removal was less variable (P < 0.01) in the 2 and 5mg EV groups than in the Control group, and intermediate in the 1mg EV group. In summary, treatment with 5mg EV resulted in a longer and more variable interval to follicular wave emergence than treatment with 5mg estradiol-17beta, which affected preovulatory dominant follicle size following progestin removal, and may have also affected superstimulatory response in Holstein cows. Additionally, 5 mg EV appeared to induce luteolysis in heifers, reducing the interval to ovulation following norgestomet removal. Conversely, intervals to, and synchrony of, follicular wave emergence, estrus and ovulation following treatment with 1 or 2 mg EV suggested that reduced doses of EV may be more useful for the synchronization of follicular wave emergence in progestogen-treated cattle.

In vitro assessment of corpus luteum function in cattle following Ovsynch and CIDR ovulation synchronization protocols

Non-lactating beef cows (N = 40) were used to determine in vitro production of progesterone by CLs collected on days 6–8, 13–15 and 19–20, following Ovsynch or CIDR ovulation synchronization protocols. Progesterone released by the CL tissues into the medium was measured after 1 h of incubation (control) and after 6 h of hormone treatments (LH, PGF2α or LH + PGF2α). In vitro progesterone production did not differ (P > 0.05) between Ovsynch and CIDR ovulation synchronization protocols. Pooled data, irrespective of ovulation synchronization treatments, showed interaction (P < 0.05) between hormone treatment and stage of CL. Key words: Corpus luteum, progesterone, cows, ovulation synchronization

Effects of evening feeding and extended photoperiod on growth, feed efficiency, live animal carcass traits and plasma prolactin of beef heifers housed outdoors during two Manitoba winters

The effects of evening feeding and extended photoperiod on feedlot performance, live animal carcass traits and plasma prolactin were investigated in crossbred beef heifers in two consecutive Manitoba winters (1998–1999; exp. 1 and 1999–2000; exp. 2) using a 2 × 2 factorial design. Heifers were fed in the morning (1000 exp. 1 and 0900 exp. 2) or evening (2000) and exposed to natural winter photoperiod (NP) of <15 h or extended winter photoperiod (EP) of 16–19 h (65 lux exp. 1, 51 lux exp. 2) in outdoor partially covered pens. Heifers (n = 48; 276.9 ± 19.4 kg, mean ± SD) in exp. 1 were given a 60% forage: 40% concentrate backgrounding ration for 56 d followed by a 25% forage: 75% concentrate finishing ration for 70 d. In exp. 2, heifers (n = 48; 228.8 ± 18.8kg) were given the backgrounding ration for 170 d. Mean ambient temperature during the backgrounding and finishing periods in exp. 1 was -13.7 and 0.5°C, respectively. During the backgrounding period of exp. 1, evening feeding increased (P = 0.05) growth rate 10.1%, and tended (P = 0.08) to improve feed efficiency by 9.0%; EP tended (P = 0.08) to improve feed efficiency by 9.0%. During the finishing period there was a time of feeding × photoperiod interaction (P = 0.02) for feed efficiency with a tendency for most efficient gains in the morning-fed NP heifers. There were no main or interaction effects of time of feeding and photoperiod on ultrasonically measured subcutaneous fat depth or longissimus dorsi muscle area in exp. 1. Plasma prolactin was elevated by EP on day 42 (photoperiod × day; P < 0.01) of exp. 1. Mean ambient temperature during exp. 2 was -5.1°C, and there were no main or interaction effects of time of feeding or photoperiod on weight gain, dry matter intake or feed efficiency. However, subcutaneous fat depth was reduced by EP on day 156 (photoperiod × day; P < 0.01). Plasma prolactin did not change during the first 107 d of exp. 2, but subsequently rose in all but the morning-fed EP treatment group. The results indicate that both evening feeding and extended photoperiod can impact growth and feed efficiency of beef cattle during winter-feeding. Key words: Feedlot heifers, beef cattle, evening feeding, extended photoperiod, light, prolactin

Effect of low and high forage diet on enteric and manure pack greenhouse gas emissions from a feedlot

The objectives of this study were to assess enteric methane (CH4) production by beef steers fed one of two isocaloric diets with different forage:grain ratios and to quantify greenhouse gas (GHG) emissions from bedded manure packs in the eight feedlot pens holding these steers (14 head pen-1). Five animals (252 ± 20 kg) in each pen were randomly selected for measurement of CH4 emissions over the course of the 126-d feeding trial. Two 24-h gas collections were completed for each steer in each of three collection periods using the sulfur hexafluoride tracer gas technique. The fluxes of nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2) from bedding packs were measured using vented static chambers in each sampling period. Methane production (L d-1) was 42% higher (P < 0.05) from steers fed the low forage:grain ratio than from steers fed the high forage:grain ratio. Overall, methane production (% of gross energy intake) ranged from 0.9 to 6.9% on the low forage:grain diet and from 0.7 to 4.9% on the high forage:grain diet. Daily CH4 emissions were similar in the first two periods and increased during the third sampling period. There was no effect of diet on manure pack temperature during sampling, however, the manure pack was deeper (P < 0.05) in pens holding animals fed the high forage:grain diet. Furthermore, diet had no effect on the manure pack fluxes. Total daily non-CO2 emissions from enteric and manure pack sources (CO2 equivalent) were different (P < 0.05) between dietary treatments and averaged 1931 ± 81 g head-1 d-1 for the low forage:grain and 1394 ± 81 g head-1 d-1 for the high forage:grain diet. Key words: Feedlot steers, greenhouse gases, enteric fermentation, manure packs

Time of feeding and growth promotant effects on the winter growth performance and carcass traits of steers

The effects of time of day of feeding and estrogenic growth promotant on growth performance and carcass traits were determined in three experiments conducted over 3 yr (winters 1998–1999, 1999–2000, 2000–2001). Crossbred steers (year 1, n = 144, year 2, n = 128, year 3, n = 144) were assigned at fall weaning on the basis of sire, age (190 ± 21 d, mean ± SD), and body weight (244 ± 34 kg) to one of eight pens in an outdoor lot at the Brandon Research Centre (49°54′N). In years 1 and 2, pens were assigned to either morning-fed (MF, 0900) or evening-fed (EF, 2000) treatments, and steers within pen were assigned to either Synovex Plus® (TAE) or Synovex S® (PE) growth promotants. In year 3, pens were assigned to either TAE or PE treatments and all were evening-fed. Beginning on Nov. 09 (0 d), steers were given a 20% hay, 80% concentrate (79.2% barley, 0.8% premix) mixed ration (88.6% dry matter, 13.7 MJ kg-1 digestible energy, 124 g kg-1 crude protein, 33.6 mg kg-1 lasalocid). Diets were fed, once daily, in amounts that were consumed before the next feeding, until steers were marketed. Growth promotants were administered at 0 and 84 d. The winter of year 2 was warmer (P < 0.05) than, and years 1 and 3 similar (P > 0.05) to, the 30-yr average ambient temperature (-8.8°C and -12.9°C, respectively). Evening feeding increased (P < 0.05) gain in body weight, especially in year 2 and backfat, especially in year 1, and this was reflected in heavier (P < 0.05) carcass weight in year 2, and whiter (P < 0.05) fat and greater (P < 0.05) rib eye moisture in year 1 and overall reduced (P < 0.05) feed cost of gain in winter. In all 3 yr TAE, relative to PE, produced greater (P < 0.05) body weight gain, and heavier, leaner carcasses with greater (P < 0.05) rib eye area, coarser (P < 0.05) meat texture and greater (P < 0.05) shear force, and reduced (P < 0.05) the feed cost of gain. Time of feeding and choice of growth promotant have significant potential to reduce the business risk of feeding steers in winter. Key words: Beef steer, growth implant, feeding strategy, growth promotant, carcass trait

Photoperiod effects on the development of beef heifers

Crossbred beef heifers (n = 144) were assigned at weaning (187 ± 14 d of age) by body weight (225 ± 23 kg) and sire breed (British/Continental) to one of two photoperiod treatments from 21 Decem ber 1998 (0 wk) until 10 May 1999 (20 wk): natural photoperiod (NP) that gradually increased from 8.1 h (0 wk) to 15.2 h (20 wk) and, extended photoperiod (EP) that consisted of natural + supplemental light (400 lx, 1 m above ground) to extend photoperiod to 16 h. Rations were formulated for two-steps of body weight gain (0.6 and 1.2 kg d-1) to achieve 60% of mature weight at 18 wk. Visual observations of estrus behavior were made twice daily and confirmed by serum progesterone. Body weight, backfat and serum prolactin data were determined for each 4-wk period. Ambient temperatures averaged -12.2 ± 6°C in winter (0 to 12 wk) and 4.2 ± 5°C in spring (12 to 20 wk). Gain in body weight was greater (P < 0.05) and backfat lower (P < 0.05) for EP than NP treatments from -2 to 6 wk and only 1% of heifers had attained puberty during this period. However, as yearlings at similar (P > 0.05) body weight and backfat, more (P < 0.05) EP than NP heifers had attained puberty (84.7% vs. 69.4%). Prolactin was greater (P < 0.05) for EP than NP treatments from 2 to 6 wk (10.3 vs 5.5 ± 1.2 ng mL-1). Management of photoperiod influences attainment of puberty and prolactin secretion in beef heifers housed in an outdoor environment. Key words: Photoperiod, puberty, estrus, beef heifers, prolactin

The Analysis of Particles at Low Accelerating Voltages (≤ 10 kV) With Energy Dispersive X-Ray Spectroscopy (EDS)

In recent years, there have been a series of advancements in electron beam instruments and x-ray detectors which may make it possible to improve significantly the quality of results from the quantitative electron-probe analysis of individual particles. These advances include: (1) field-emission gun electron beam instruments such as scanning electron microscopes (FEG-SEMs) that have high brightness electron guns with excellent performance at low beam energies, E 0 ≤ 10 keV and (2) high-resolution energy-dispersive x-ray spectrometers, like the microcalorimeter detector, that provide high-resolution (< 10 eV) parallel x-ray collection. These devices make it possible to separate low energy (< 4 keV) x-ray lines including the K lines of carbon, nitrogen and oxygen and the L and M lines for elements with atomic numbers in the range of 25 to 83. In light of these advances, this paper investigates the possibility of using accelerating voltages ≤ 10 kV, as a method to improve the accuracy of elemental analysis for micrometer-sized particles.

Improving the quality of electron backscatter diffraction (EBSD) patterns from nanoparticles

In this study, we investigated the relative contributions of atomic number (Z) and density (rho) to the degradation of the electron backscatter diffraction (EBSD) pattern quality for nanoparticles < 500 nm in diameter. This was accomplished by minimizing the diffuse scattering from the conventional thick mounting substrate through the design of a sample holder that can accommodate particles mounted on thin-film TEM substrates. With this design, the contributions of incoherently scattered electrons that result in the diffuse background are minimized. Qualitative and quantitative comparisons were made of the EBSD pattern quality obtained from Al(2)O(3) particles approximately 200 nm in diameter mounted on both thick- and thin-film C substrates. For the quantitative comparison we developed a 'quality' factor for EBSD patterns that is based on the ratio of two Hough transforms derived from a given EBSD pattern image. The calculated quality factor is directly proportional to the signal-to-noise ratio for the EBSD pattern. In addition to the comparison of the thick and thin mounting substrates, we also estimated the effects of Z and rho by comparing the EBSD pattern quality from the Al(2)O(3) particles mounted on thin-film substrates with the quality of patterns obtained from Fe-Co nanoparticles approximately 120 nm in diameter. The results indicate that the increased background generated in EBSD patterns by the electrons escaping through the bottom of the small particles is the dominant reason for the poor EBSD pattern quality from nanoparticles < 500 nm in size. This was supported by the fact that we were able to obtain usable EBSD patterns from Al(2)O(3) particles as small as 130 nm using the thin-film mounting method.

The effects of gonadotrophin releasing hormone in prostaglandin F2α-based timed insemination programs for beef cattle

Trials were conducted in the spring (May; n = 324) and fall (October; n = 132) with crossbred continental-type beef cows assigned on the basis of parity and postpartum interval to one of three timed-AI treatments and one of two post-AI treatments. The timed-AI treatments were: (DPG) double (14 d apart) PGF2α (Lutalyse®) and AI (day = 0) 72 h after the second PGF2α (day –3); (OVS) Ovsynch® with the second GnRH (Factrel®) at 48 h and AI at 66 h; and (BRC) the same as OVS except that the second GnRH was given at the time of AI. Half of the cows within each treatment were given GnRH on day 14. Plasma progesterone concentrations were determined for the day of the first injection and on days –3, 0, 14, and 21. Timed-AI pregnancy was diagnosed by ultrasonography at day 42 and confirmed at calving. For DPG, OVS and BRC, PGF2α responder rates were 75.9, 51.4 and 71.3%, respectively, in spring (P < 0.05) and 70.4, 70.4 and 59.1% in fall (P > 0.05), and AI pregnancy rates were 28.7, 44.9 and 44.4% in spring (P< 0.05) and 25.0, 40.9 and 43.2% in fall (P > 0.05). Post-AI GnRH had no significant effect on pregnancy or conception rates or day 21 progesterone. The use of GnRH in the PGF2α based timed-AI program improved pregnancy rates and the BRC treatment was as effective as OVS. Neither postpartum interval nor initial progesterone concentration influenced (P >0.05) the effect of GnRH on AI pregnancy rate, and GnRH had no effect (P > 0.05) on twinning rate or gender ratio. Key words: Beef cows, estrous synchronization, pregnancy, timed-AI, progesterone

Phase identification of individual crystalline particles by electron backscatter diffraction

Recently, an electron backscatter diffraction (EBSD) system was developed that uses a 1024 x 1024 CCD camera coupled to a thin phosphor. This camera has been shown to produce excellent EBSD patterns. In this system, crystallographic information is determined from the EBSD pattern and coupled with the elemental information from energy or wavelength dispersive X-ray spectrometry. Identification of the crystalline phase of a sample is then made through a link to a commercial diffraction database. To date, this system has been applied almost exclusively to conventional, bulk samples that have been polished to a flat surface. In this investigation, we report on the application of the EBSD system to the phase identification analysis of individual micrometre and submicrometre particles rather than flat surfaces.

The effects of bull exposure and lasalocid on the development of replacement beef heifers

At weaning in the fall, crossbred heifers (n = 224), born in either the winter (January–February) or spring (March–April), were assigned on the basis of age, sire-breed and body weight to one of two similar winter housing facilities (with or without sterilized bulls), and to one of two forage-based (87%) diets (with or without lasalocid, 200 mg d−1) within each housing facility. Observations for estrus were made twice daily. Timed AI (66 h after PGF2α) was used to breed heifers for the first time at 14 mo of age. Plasma progesterone concentrations were used to confirm estrus/ovulation and to determine the PGF2α response rate. Bull exposure advanced puberty in winter-born heifers, but delayed puberty in spring-born heifers (P ≤ 0.029). Similarly, timed AI pregnancy for winter-born heifers was higher with than without bull exposure (58.9 vs. 32.5 ± 5.3%; P = 0.017) while the opposite occurred for the spring-born group (27.1 vs. 59.1 ± 4.7%; P < 0.001). Bull-exposed spring-born heifers were the oldest at calving, the latest to calve, and their calves had the slowest growth and lowest weaning weight means (P < 0.027). Lasalocid did not influence puberty (P ≥ 0.273), had a small effect on body weight gain (P ≥ 0.033) that did not limit attainment of optimal body weight or condition at AI, but enhanced response rate for spring-born heifers (P = 0.075) and conception rate for winter-born heifers (P = 0.047). The efficacy of bull exposure and lasalocid is dependent upon the proximity of heifers to the attainment of puberty when the treatments are introduced; further research is required to determine the most appropriate use of either management tool for developing beef replacement heifers. Key words: Puberty, heifer development, bull exposure, ionophore, estrus, conception

The performance of primiparous and multiparous beef cows rearing single and simulated-twin calves

One hundred and eighteen Hereford-cross heifers (n = 70) and cows (n = 48) and their offspring were used to evaluate the impact of simulated twinning on weaned calf production and reproductive performance. Twin-calf rearing was simulated by the adoption of a second calf born within 24 h of the birth of the dam's natural calf. In each of 4 yr, cows calved in winter (January–February), were turned out in spring (late May) to rotationally graze grass-legume pastures until weaning in the fall (late September). From calving until turnout cows were given a forage-based diet consisting of either grass-legume silage or hay offered free choice, plus concentrate, the amount of which was 75 or 100% higher for dams in the simulated-twin (ST) than the single (S) treatment. All calves had access to the conserved forage and were given the concentrate ration as creep feed. Estrus detection was performed twice daily beginning 3 wk before and continuing for 4 wk into the breeding season, which consisted of AI for the first 25 d and bull service for the remaining 22 d. In years 2 and 3, the postpartum anestrous period was determined by serum progesterone concentrations. At weaning, S calves weighed more than natural or adopted calves in the ST treatment because weight gain was greater for S calves from birth to turnout. However calf production efficiency (total kilograms calf weaned per kilogram dam weight) was greater for primiparous and multiparous ST than S groups (primiparous 0.85 vs. 0.43 and multiparous 1.62 vs. 0.49; P < 0.05). The ST treatment had no negative effect (P > 0.05) on reproductive performance. As a research tool, this study suggests there are large potential benefits to beef cows raising two, as opposed to one calf. Simulated twinning poses severe management challenges and is not being proposed as a commercial option. However, advances in reproductive technology that could control twinning (e.g., transfer of an embryo a week following AI or twin-transfer of sexed embryos) mean that in future, twin rearing of beef calves may become a feasible option and this study provides valuable information on the post-natal management of cows rearing two calves. Key words: Simulated-twin, progesterone, post-partum, weaning, cow-calf, calves

Sentence repetition and processing resources in Alzheimer's disease

Sentence processing in Alzheimer's disease (AD) has been found to be influenced by several grammatical and extragrammatical factors, including phrase structure and verb-argument relations, number of propositions/verbs, and processing resource capacity. This study examines the effects of these variables on sentence production in AD. Normal control and AD subjects were asked to repeat six types of sentences varying along the above dimensions of complexity. Subjects' processing resource capacity was measured using several verbal working memory tests. AD subjects' sentence-repetition performance was impaired compared to the normal control group. Significant effects were observed for branching direction of phrase structure, canonicity of verb-argument relations, and serial position of errors. Sentence-repetition performance significantly correlated with working memory scores. The findings are interpreted within a resource capacity theory of sentence processing.

Beef cattle management in Manitoba

A survey was conducted to document general characteristics of beef cattle management and identify producer concerns in Manitoba. The survey was divided into five sections: (i) characterization of farm operation, (ii) winter management, (iii) forage and pasture management, (iv) reproductive management and (v) factors limiting profitability and the use of non-traditional management tools. The surveyprovided base information for measuring change in the industry and identified cost of production, pasture, and reproduction as the top three factors that producers consider limiting the profitability of beef operations in Manitoba. Key words: Beef cattle, forage, pasture, reproduction, nutrition, survey

Influence of post-calving supplemental protein on calf performance and reproductive efficiency for beef cows fed silage

Protein supplementation for winter-calving beef cows between calving and turnout to pasture was studied in two trials. Changes in cow body weight (BW) and condition and calf BW gains were recorded from calving to weaning in the fall. Reproductive performance was monitored, and in trial 2, milk production was determined. In trial 1, multiparous silage-fed cows were allocated to one of five levels of corn gluten meal (CGM): 0, 200, 400, 600 and 800 g d−1. In the second trial, cows were allocated to either restricted or ad libitum silage feeding in combination with three protein supplements: no protein, 400 g d−1 CGM or 475 g d−1 soybean meal (SBM). In trial 1, cows gained weight during supplementation, but on pasture they lost weight (linear effect, P = 0.10). Calf gains and weights at turnout and weaning showed a quadratic response to protein supplementation (P < 0.05). There was a trend toward a linear decline in days to first service with increasing levels of CGM (P < 0.10). In trial 2, cows on restricted silage feeding lost weight (P < 0.05) and body condition (P < 0.10), whereas those fed ad libitum silage gained weight and condition. On pasture, this pattern of weight change was reversed (P < 0.05). Protein supplementation did not influence BW change but tended to cause a lower body condition score at turnout (P = 0.10). Restricting silage intake to the cow did not affect calf performance, but protein supplementation increased gains both during supplementation and on pasture, thus increasing weaning weights (P < 0.05). When silage was fed ad libitum, SBM was more effective than CGM for increasing calf gain. However, when silage was restricted, CGM was more effective. Restricting silage intake did not impair milk production, but feeding CGM increased milk production (P < 0.05). For ad libitum-fed cows, protein supplementation increased pregnancy rate; restricting feed had the opposite effect. Our data suggest that protein supplementation to silage-fed beef cows in good body condition can increase calf performance; however, the level of supplementation is critical, and possible adverse effects on breeding have to be taken into account, particularly with cows in negative energy balance after calving. Key words: Beef cow, protein, milk production, calf gains, silage

Measurement of vaginal temperature by radiotelemetry for the prediction of estrus in beef cows

Peaks in vaginal temperature were assessed as predictors of estrus in 22 suckled beef cows during 2 breeding seasons. A flexible plastic anchor was used to retain a temperature radiotransmitter within the cow vagina and vaginal temperature was monitored at 4-min intervals. Blood was collected twice weekly for analysis of serum progesterone to confirm the occurrence of estrus and ovarian status was checked weekly using transrectal ultrasonography. Visual observations of estrous behavior were made for 20 min/h between 0400 and 0800 h and casually from 0800 to 1600 h (4 to 6 times). Values for vaginal temperature were available for 47 estrous periods. The prediction of estrus based on vaginal temperature was excellent when an estral peak in vaginal temperature was defined as an increase of at least 0.4 degree C for 3 or more consecutive hours using the corresponding hourly means of a 2 or 3-d baseline. Combining the results of 2 separate years and using a 3-d baseline, a peak in vaginal temperature was found for 42 of 47 confirmed estrus periods (detection sensitivity of 89.4% and prediction power positive of 85.7%). Corresponding detection sensitivity and prediction power positive for visual observations of standing estrus were 53.2 and 96.2%, respectively. The mean maximal increase in vaginal temperature at estrus was 0.9 +/- 0.3 degree C and the mean duration of the estrual peak in vaginal temperature was 6.5 +/- 2.7 h. In addition, vaginal temperature was found to be significantly depressed for 3 d prior to estrus and significantly elevated at mid-cycle.

Grammatical abilities in Parkinson's disease: evidence from written sentences

This study examined the grammatical content of written sentences elicited from 96 Parkinson's patients, 30 Parkinson's with dementia patients and 167 control subjects. Parkinson's patients without dementia or with mild dementia presented no impairments in sentence length, syntactic complexity or amount of information content. Moderately demented Parkinson's patients showed reduced sentence length and information content but normal syntactic complexity. This pattern of results provides evidence that lexical-semantic content is more susceptible to decline than syntactic structure with the progression of dementia in Parkinson's disease.

Sentence comprehension in Alzheimer's disease: effects of grammatical complexity, speech rate, and repetition

Caregivers of patients diagnosed with Alzheimer's disease (AD) are often advised to modify their speech to facilitate the patients' sentence comprehension. Three common recommendations are to (a) speak in simple sentences, (b) speak slowly, and (c) repeat one's utterance, using the same words. These three speech modifications were experimentally manipulated in order to investigate their individual and combined effects on sentence comprehension in AD. Fifteen patients with mild to moderate AD and 20 healthy older persons were tested on a sentence comprehension task with sentences varying in terms of (a) degree of grammatical complexity, (b) rate of presentation (normal vs. slow), and (c) form of repetition (verbatim vs. paraphrase). The results indicated a significant decline in sentence comprehension for the AD group. Sentence comprehension improved, however, after the sentence was repeated in either verbatim or parapharsed form. However, the patients' comprehension did not improve for sentences presented at the slow speech rate. This pattern of results is explained via-à-vis the patients' working memory loss. The findings challenge the appropriateness of several clinical recommendations.

Sentence comprehension in Alzheimer's disease: effects of grammatical complexity, speech rate, and repetition

Caregivers of patients diagnosed with Alzheimer's disease (AD) are often advised to modify their speech to facilitate the patients' sentence comprehension. Three common recommendations are to (a) speak in simple sentences, (b) speak slowly, and (c) repeat one's utterance, using the same words. These three speech modifications were experimentally manipulated in order to investigate their individual and combined effects on sentence comprehension in AD. Fifteen patients with mild to moderate AD and 20 healthy older persons were tested on a sentence comprehension task with sentences varying in terms of (a) degree of grammatical complexity, (b) rate of presentation (normal vs. slow), and (c) form of repetition (verbatim vs. paraphrase). The results indicated a significant decline in sentence comprehension for the AD group. Sentence comprehension improved, however, after the sentence was repeated in either verbatim or parapharsed form. However, the patients' comprehension did not improve for sentences presented at the slow speech rate. This pattern of results is explained via-à-vis the patients' working memory loss. The findings challenge the appropriateness of several clinical recommendations.

Research on neuropsychiatric genetics: interests of the National Institute of Neurological Disorders and Stroke

The National Institute of Neurological Disorders and Stroke (NINDS) supports research concerning the determinants of normal and pathological development of the nervous system, from the genetic to the environmental. NINDS also funds basic and clinical research concerning the etiology, diagnosis, treatment, consequences, and prevention of the spectrum of neurodevelopmental disorders including neurobehavioral and neurodegenerative disorders (National Advisory Council Neurological Disorders and Stroke, 1989, 1992; Division of Convulsive, Developmental and Neuromuscular Disorders, NINDS, 1993).

Biochemical and cellular properties of three immortalized Schwann cell lines expressing different levels of the myelin-associated glycoprotein

Biochemical and cellular properties of three immortalized Schwann cell lines expressing different levels of the myelin-associated glycoprotein (MAG) were compared. The S16 line generated by repetitive passaging was described previously and expresses a level of MAG comparable to that in adult sciatic nerve. The S42 line was generated independently by the same procedure, divides more slowly than the S16 line, and expresses an even higher level of MAG. The S16Y line arose spontaneously from a passage of the S16 cells, divides much more rapidly, and does not express MAG. The levels of MAG expression in the three lines are inversely related to their rates of proliferation, and MAG mRNA levels parallel the amounts of MAG. The S16 and S42 lines consist mainly of flat cells at low density and develop many processes at high density, whereas most of the S16Y cells are spindle-shaped, resembling primary Schwann cells in appearance. Surface immunostaining with the O4 antibody was positive for the S16 and S42 cells and negative for the S16Y cells, but all three lines were negative for surface staining with the O1 antibody. The overall protein compositions of the three lines are very similar, but the S16 and S42 cells express larger amounts of several glycoproteins than the S16Y cells, including the adhesion proteins, neural cell adhesion molecule, L1, and laminin. S16 and S42 cells (but not S16Y cells) also express P0 glycoprotein, galactocerebroside, and sulfatide, but, unlike MAG, these other myelin-related components were present at much lower levels than in adult nerve. Myelin basic protein and proteolipid protein were not detected in any of the lines, although all three lines contained proteolipid protein mRNA. 2',3'-Cyclic nucleotide 3'-phosphodiesterase and glial fibrillary acidic protein were present in all three lines. Conditions have not yet been found in which any of the lines will myelinate dorsal root ganglion neurons in vitro, but the S16 and S42 cells differ from the S16Y cells by clustering around neurons after 1 week in coculture. In many respects, the S16 and S42 cells biochemically resemble Schwann cells at an early stage in their preparation to myelinate and should be useful for investigating the cell biology of MAG and other myelin-related components.

Sequences in the visna virus long terminal repeat that control transcriptional activity and respond to viral trans-activation: involvement of AP-1 sites in basal activity and trans-activation

Visna virus is a pathogenic lentivirus of sheep whose gene expression is developmentally regulated in cells of the monocyte-macrophage lineage. Gene expression directed by the visna virus long terminal repeat (LTR) is increased in infected cells by a virus-encoded trans-acting protein. trans-Activation is mediated in part by increases in the steady-state level of mRNA. Deletion and linker-scanner mutants were constructed to locate sequences in the LTR that regulate transcription and are responsive to viral trans-activation. The activities of these mutants were tested by using them to drive transcription of the bacterial gene for chloramphenicol acetyltransferase in transient expression assays. Three regions located between-140 and the cap site were found to be important for basal transcriptional activity, and the importance of each region was found to be dependent on the cell type. Sequences responsive to viral trans-activation were found to be the same sequences required for basal transcriptional activity. The visna virus LTR contains six sequences that are homologous to the recognition site for cellular transcriptional factor AP-1 and a single sequence homologous to the recognition site for transcriptional factor AP-4. Both of these classes of binding sites appear to be important for regulating the basal level of transcription of visna virus. The AP-1-binding site most proximal to the TATA box was found to be one target for viral trans-activation. The visna virus promoter was found to be activated by serum; this serum response has also been mapped to the AP-1-related sequences in the LTR.

Regulation of the visna virus long terminal repeat in macrophages involves cellular factors that bind sequences containing AP-1 sites

Visna virus gene expression is highly restricted in monocytes but is induced by monocyte-macrophage differentiation in vivo. Deletion and linker-scanning mutants, gel shift assays, and DNase I footprinting were used to identify sequences in the visna virus long terminal repeat involved in the developmental regulation of gene expression in the U937 monocytic cell line. We found that an AP-1 and an AP-4 binding site were critical for basal activity and that the AP-1 site was required for phorbol ester-inducible gene expression. These results suggest that cellular factors that interact with AP-1 sites are involved in the developmental regulation of visna virus gene expression in macrophages.

The visna virus long terminal repeat directs expression of a reporter gene in activated macrophages, lymphocytes, and the central nervous systems of transgenic mice

Visna virus is a lentivirus which causes a slow progressive disease involving the immune system and the central nervous system. To determine the role of the viral long terminal repeat (LTR) in targeting the virus to specific host cells and tissues, transgenic mice were constructed which contained the visna virus LTR directing expression of the bacterial gene encoding chloramphenicol acetyltransferase (CAT). Analysis of the transgenic mouse tissues for CAT activity revealed that the viral LTR was responsible, in part, for the tropism of visna virus for macrophages and the central nervous system. Expression of the LTR required the macrophage to be in an activated state both in vivo and in vitro. Thioglycolate activation of peritoneal macrophages in vivo and 12-O-tetradecanoylphorbol 13-acetate treatment in vitro induced expression of the visna virus LTR. Lymphocytes from the spleens of the transgenic mice expressed CAT activity, suggesting that visna virus was able to replicate in lymphocytes, as did human immunodeficiency virus and simian immunodeficiency virus. These studies demonstrated that the lentivirus LTR was responsible, in part, for cell and tissue tropism in vivo.

Dysmyelination in transgenic mice containing JC virus early region

JC virus (JCV) causes the chronic human demyelinating disease progressive multifocal leukoencephalopathy. Because of host range restrictions, experimental models of JCV-induced demyelination have not been available. The restricted tropism of JCV infectivity has recently been overcome by the production of transgenic mice that contain the early region of JCV in all cells. This portion of the DNA encodes JCV T-antigens. These mice display a dysmyelinating phenotype, the severity of which is related to the level of JCV early region expression in brain. With the use of immunocytochemistry and in situ hybridization, we characterized morphologically myelin-specific and JCV gene expression in a severely affected strain of these mice. Our results suggest that expression of JCV T-antigens occurs predominantly in oligodendrocytes and is the primary cause of dysmyelination. Affected oligodendrocytes do not myelinate axons properly. However, they express myelin-specific genes and display some of the morphological phenotypes of early stages of myelination. A decreased ratio between levels of transcriptional and translational products of genes encoding the major structural proteins of central nervous system myelin was apparent. These results suggest that JCV T-antigens arrest the maturation of oligodendrocytes and inhibit the production of myelin. These results also demonstrate that JCV transgenic mice are a good model for investigating mechanisms of JCV-induced demyelinating lesions in progressive multifocal leukoencephalopathy.

Early regions of JC virus and BK virus induce distinct and tissue-specific tumors in transgenic mice

JC virus and BK virus are ubiquitous human viruses that share sequence and structural homology with simian virus 40. To characterize tissue-specific expression of these viruses and to establish model systems for the study of human viral-induced disease, transgenic mice containing early regions of each of the viruses were produced. The viral sequences induced tumors in a distinct and tissue-specific manner that was similar to their tissue tropism in humans. Ten JC virus-containing founder mice were produced, of which 5 survived to maturity. Four of them developed adrenal neuroblastomas, which metastasized to several other tissues. JC virus tumor-antigen RNA was detected at high levels in the tumor tissues and at low levels in the normal tissues of these mice. One of the three BK virus-containing mice was abnormally shaped and died at 2 weeks of age. The other two BK virus-containing mice developed primary hepatocellular carcinomas and renal tumors and died at 8-10 months of age. BK virus tumor-antigen RNA was expressed in tumor tissues of both mice. Since each of the viruses retained the general tissue tropism that it exhibits in humans, these data suggest that transgenic mice harboring human viruses will be useful as animal models for viral-induced diseases.

The early region of human papovavirus JC induces dysmyelination in transgenic mice

Transgenic mice containing the early region of human papovavirus JC were produced. Some of these mice exhibited a shaking disorder similar to the previously described mutant mice jimpy or quaking. Neuropathological analysis indicated a dysmyelination in the central nervous system, but not the peripheral nervous system. A high level of JCV T-antigen mRNA was present in the brains of the mice exhibiting the myelin disorder. JC virus is associated in humans with a degenerative demyelinating disease: progressive multifocal leukoencephalopathy. The JCV-containing transgenic mice may therefore provide an animal model for studying this disease.