The effect of transport by road and sea on physiology, immunity and behaviour of beef cattle.

The objective of the study was to investigate the physiological, haematological and immunological responses of weanling heifers transported from Ireland to a feedlot in Spain, and of weanling bulls transported from Ireland to a feedlot in Italy. Physiological variables (including interferon-γ production, cortisol, protein, urea, white blood cell numbers and differentials, and acute phase proteins (haptoglobin and fibrinogen) were used to evaluate the welfare status of animals, before, during and after the respective transport journeys. Age-matched control animals were blood sampled for the same measurements at times corresponding to the transported animals that were retained in Ireland. Heifers transported to Spain lost 7.6% of their initial live weight during the sea crossing to France. However, by the time of their arrival in Spain they had regained 3.3% of their initial live weight and had fully recovered to their pre-transport live weight values within 6 days of arriving in Spain. Weanling bulls lost 7.0% of their live weight during the sea crossing from Ireland to France. The live weight loss in control animals ranged from 1% to 2% during the same period. The percentage of time that bulls spent lying was 63.5% for the sea journey and 35.4% for the journey from the French lairage to the Italian feedlot. The average daily gain (kg) of transported animals was greater (P ≤ 0.05) than control animals from day 11 to 38 (Spain) and day 11 to 40 (Italy), respectively. While transient changes in physiological, haematological and immunological variables were found in the transported and control animals relative to baseline levels, the values were within the normal physiological range for the age and weight of animals involved. Physiological measurements made after the road and sea journeys indicated that the 24h rest in the lairage, with hay and water freely available, allowed animals to recover substantially.

The effect of sea transport from Ireland to the Lebanon on inflammatory, adrenocortical, metabolic and behavioural responses of bulls.

The objective was to investigate the effect of sea transport on the physiological, behavioural and performance responses of bulls. One-hundred and eleven bulls (mean body weight (standard error of the mean) 429 (5.7 kg)) were randomly assigned to one of three treatments; control (C; n=54) bulls were housed in 6 pens at Teagasc, Grange Research Centre at a stocking density of (1), 1.7 m(2)/head (C1.7; 3 pens) and (2), 3.4 m(2)/head (C3.4; 3 pens) and (3), transported (T) bulls (n=57) were penned at a space allowance of 1.7 m(2)/head (6 pens) and allocated to one of five decks on the shipping vessel. C and T bulls were subjected to the same live weight (d -2), blood sampling and rectal temperature (d -1) measurements pre-transport and on d 3, d 6, d 9 and d 11 of the study. T bulls had greater (P<0.05) live weight gain (+4.4%) compared with C1.7 bulls (-2.0%) and C3.4 (+0.13%)). Time spent lying was greater (P<0.05) among C1.7 and C3.4 bulls (9.9% and 53.3%, respectively) compared with T bulls (45.8%). Rectal body temperature was not different (P>0.05) among treatment groups throughout the study. At d 11, neutrophil % was greater (P<0.05) in transported bulls on decks 1, 2, 4 and 5 compared with C1.7 and C3.4 treatments. Plasma cortisol concentrations were not different (P>0.05) between control and transported bulls. Plasma creatine kinase (CK) activity was lower (P<0.05) among C3.4 and T bulls on decks 2, 3, 4 and 5 compared with d 3 values. In conclusion, the welfare of bulls transported by sea on the sea journey was not adversely affected. Housing control bulls at a reduced space allowance (1.7 m(2)) had a negative effect on live weight gain.

Energy level in winter diets of Fallow deer: effect on plasma levels of insulin-like growth factor-I and sex ratio of their offspring.

To determine the effect of dietary energy level in the first winter on subsequent puberty onset, pregnancy, growth, and secretion of progesterone and insulin-like growth factor-I (IGF-I) in Fallow deer, prepubertal deer were fed either a high (H) or a low (L) energy diet in a randomised complete block design. June-born female Fallow deer were fed ad libitum either 12.5MJ/kg DM (H, n=29) or 10MJ/kg DM (L, n=29) in pelleted rations once per day during the winter (approximately 4-10 months of age) preceding puberty. Blood samples were collected twice weekly during the peripubertal period. During the winter feeding period, DM intake was similar for both groups but average daily gain was greater (P<0.05) for deer fed the H versus L diet. Onset of puberty was not affected (P>0.10) by dietary treatment. Concentrations of progesterone in plasma did not differ (P>0.10) between dietary treatments before or after puberty, increasing after puberty in both groups, and reaching maximal levels 8-12 days after the onset of puberty. Concentrations of plasma IGF-I increased (P<0.05) before puberty in both groups reaching maximal levels 3-4 days before the onset of puberty but did not differ (P>0.10) between H and L diets before or after puberty. Of the 28 does fed the H diet that calved, 75% of the calves born were male versus 46% in the L diet (P<0.05). In conclusion, increased plasma IGF-I concentrations were associated with the onset of puberty in Fallow deer regardless of the level of dietary energy intake during the preceding winter. Increased dietary energy during winter does not alter pregnancy rates but does alter sex ratio of calves born.

Effects of suppressing cortisol following castration of bull calves on adrenocorticotropic hormone, in vitro interferon-gamma production, leukocytes, acute-phase proteins, growth, and feed intake.

The objective was to determine the effects of reducing the plasma cortisol rise in calves following castration on plasma ACTH concentrations, keyhole limpet hemocyanin (KLH)- and concanavalin A (Con A)-induced in vitro interferon (IFN)-gamma production, white blood cell (WBC) numbers, neutrophil:lymphocyte (N:L) ratio, plasma haptoglobin and fibrinogen concentrations, ADG, and ADFI. Forty 5-mo-old Friesian bull calves (169 +/- 1.7 kg) were assigned to four treatments: 1) control (CON); 2) oral metyrapone administration (MET); 3) surgical castration at 0 h on d 0 (SURG); and 4) oral metyrapone administration and surgical castration (MET+SURG). Cortisol, ACTH, IFN-gamma production, haptoglobin, fibrinogen, ADFI, and ADG were not different between CON and MET animals. The MET+SURG calves had lower (P < .001) peak and mean cortisol during .25 to 1.5 h than SURG animals, but area under the cortisol vs time curve from 0 to 12 h did not differ (P > .39) between SURG and MET+SURG calves. Peak ACTH concentrations and area under the ACTH vs time curve from 0 to 6 h were greater (P < .05) for MET+SURG than for SURG calves. There were no differences between MET+SURG and SURG animals in IFN-gamma production, WBC numbers, and ADFI. On d 1, MET+SURG and SURG animals had lower (P < .01) KLH- and Con A-induced IFN-gamma production and higher (P < .05) neutrophil numbers and N:L ratio compared with CON animals. Plasma haptoglobin on d 1 and 3 and fibrinogen concentrations on d 3 and 7 were elevated (P < .05) for MET+SURG and SURG compared with CON animals, whereas SURG animals had greater (P < .05) haptoglobin and fibrinogen concentrations than MET+SURG animals on d 7. The ADG of SURG calves was lower (P < .05) than that of MET+SURG calves during d 0 to 7. Metyrapone treatment partially suppressed cortisol and increased ACTH in castrated calves but did not alter the castration-induced suppression of IFN-gamma and increases in neutrophil numbers and the N:L ratio.

Normal or induced secretory patterns of luteinising hormone and follicle-stimulating hormone in anoestrous gonadotrophin-releasing hormone-immunised and cyclic control heifers.

The objective was to determine the effect of gonadotrophin-releasing hormone (GnRH), GnRH analogue (GnRH-A) or oestradiol administration on luteinising hormone (LH) and follicle-stimulating hormone (FSH) release in GnRH-immunised anoestrous and control cyclic heifers. Thirty-two heifers (477 +/- 7.1 kg) were immunised against either human serum albumin (HSA; controls; n = 8), or a HSA-GnRH conjugate. On day 70 after primary immunisation, control heifers (n = 4 per treatment; day 3 of cycle) received either (a) 2.5 micrograms GnRH or (b) 2.5 micrograms of GnRH-A (Buserelin) and GnRH-immunised heifers (blocked by GnRH antibody titre; n = 6 per treatment) received either (c) saline, (d) 2.5 micrograms GnRH, (e) 25 micrograms GnRH or (f) 2.5 micrograms GnRH-A, intravenously. On day 105, 1 mg oestradiol was injected (intramuscularly) into control (n = 6) and GnRH-immunised anoestrous heifers with either low (13.4 +/- 1.9% binding at 1:640; n = 6) or high GnRH antibody titres (33.4 +/- 4.8% binding; n = 6). Data were analysed by ANOVA. Mean plasma LH and FSH concentrations on day 69 were higher (P < 0.05) in control than in GnRH-immunised heifers (3.1 +/- 0.16 vs. 2.5 +/- 0.12 ng LH ml-1 and 22.5 +/- 0.73 vs. 17.1 +/- 0.64 ng FSH ml-1, respectively). The number of LH pulses was higher (P < 0.05) in control than in GnRH-immunised heifers on day 69 (3.4 +/- 0.45 and 1.0 +/- 0.26 pulses per 6 h, respectively). On day 70, 2.5 micrograms GnRH increased (P < 0.05) LH concentrations in control but not in GnRH-immunised heifers, while both 25 micrograms GnRH and 2.5 micrograms GnRH-A increased (P < 0.05) LH concentrations in GnRH-immunised heifers, and 2.5 micrograms GnRH-A increased LH in controls. FSH was increased (P < 0.05) in GnRH-immunised heifers following 25 micrograms GnRH and 2.5 micrograms GnRH-A. Oestradiol challenge increased (P < 0.05) LH concentrations during the 13-24 h period after challenge with a greater (P < 0.05) increase in control than in GnRH-immunised heifers. FSH concentrations were decreased (P < 0.05) for at least 30 h after oestradiol challenge. In conclusion, GnRH immunisation decreased LH pulsatility and mean LH and FSH concentrations. GnRH antibodies neutralised low doses of GnRH (2.5 micrograms), but not high doses of GnRH (25 micrograms) and GnRH-A (2.5 micrograms). GnRH immunisation decreased the rise in LH concentrations following oestradiol challenge.

Immunization of prepubertal beef heifers against gonadotropin-releasing hormone: immune, estrus, ovarian, and growth responses.

To develop an effective immunization protocol against human serum albumin-Cys-Gly-GnRH (HSA-GnRH) conjugate to delay the onset of puberty in heifers, 58 heifers (8 mo of age; mean +/- SE BW = 203 +/- 1 kg) were randomly assigned to each of six treatments: 1) controls, .1 mg of HSA, with diethylaminoethyl (DEAE)-dextran as adjuvant, on d 0 and 28; 2) .1 mg of HSA-GnRH, with DEAE-dextran, on d 0; 3) as 2) and booster on d 28; 4) as 3) but boosters also on d 84, 140, 196, and 252; 5) as 2) but half the conjugate given with DEAE-dextran adjuvant and half with non-ulcerative Freund's adjuvant (NUFA), injected in two separate sites; and 6) as 2) but the conjugate given with DEAE-dextran and NUFA, emulsified and injected in two sites. The duration of the experiment was 342 d. Mean plasma GnRH antibody titers (samples every 2 wk) for heifers in Treatments 2 to 6 were 9.4 +/- 1.16, 20.6 +/- 2.21, 43.9 +/- 2.86, 27.9 +/- 2.67, and 44.5 +/- 3.75% binding at a plasma dilution of 1:640. The mean number of times estrus was observed in heifers was less (P < .05; pooled SEM = .53) in Treatments 4 (.2) and 6 (2.4) than in Treatments 1, 2, 3, and 5 (7.8, 7.0, 7.0, and 6.6, respectively). The mean interval to the onset of puberty (the first increase in plasma progesterone > or = .5 ng/mL for > or = 10 d with samples at 3- to 4-d intervals) was greater (P < .05; pooled SEM = 11.6) for heifers in treatments 4 (339 d) and 6 (276 d) than for heifers in Treatments 1, 2, 3, and 5 (164, 159, 165, and 170 d, respectively). Mean ADG of heifers was reduced (P < .05) in treatments 2, 3, 4, and 6 (.71, .72, .68, and .69 kg, respectively) compared with controls (.77). In summary, the multiple booster immunization treatment induced and maintained sufficient anti-GnRH titer to delay puberty for 175 d; a single immunization against GnRH with DEAE and NUFA increased antibody titers enough to delay puberty for 112 d. However, GnRH immunization treatments reduced ADG of heifers in Treatments 2, 3, 4, and 6.

Immunization of heifers against gonadotropin-releasing hormone: antibody titers, ovarian function, body growth, and carcass characteristics.

To investigate the effects of active immunization of cyclic beef heifers with different doses of a human serum albumin-Cys-Gly-GnRH (HSA-GnRH) conjugate on antibody titers, ovarian function, body growth, and carcass characteristics, 32 heifers (BW = 477 +/- 7.1 kg; mean +/- SE) were assigned to one of four immunization treatments: .1 mg of HSA or .01, .1, or 1.0 mg of HSA-GnRH, respectively. All heifers received a primary (d 0) and booster (d 28) immunization using DEAE-dextran as adjuvant. The duration of the experiment was 158 d. Overall antibody titers against GnRH were greater (P < .05) for heifers immunized against GnRH (13 +/- 3.3, 22 +/- 3.8, and 19 +/- 2.8% binding at a plasma dilution of 1: 640 for Treatments 2 to 4, respectively) than for controls (1 +/- .1%). The numbers of heifers that became anestrous (plasma progesterone < .5 ng/mL for > 21 d) were 1/8, 8/8, 7/8, and 8/8, respectively. The interval from primary immunization to anestrus (40.7 +/- 6 d) and the duration of anestrus (78 +/- 7 d) were not affected by dose of HSA-GnRH conjugate. The number of ovulations detected was reduced (P < .05) in GnRH-immunized (4.6 +/- .64, 4.0 +/- .70, and 3.6 +/- .60 for Treatments 2 to 4, respectively) compared with control heifers (9.4 +/- .20). During induced anestrus, follicular growth was generally arrested (< 5 mm in diameter) and plasma estradiol decreased.(ABSTRACT TRUNCATED AT 250 WORDS)

Active immunization against prostaglandin F2 alpha: effect of conjugate dose and booster interval on antibody titers and estrous behavior in postpubertal beef heifers.

To optimize the prostaglandin F2 alpha (PGF) immunization protocol (conjugate [PGF-human serum albumin; PGF-HSA] dose and immunization regimen) to achieve prolonged suppression of estrous behavior (EB) in beef heifers, 56, 14-mo-old cyclic heifers were assigned (n = 7 per treatment) to eight treatments: 1) 3.3 mg of PGF-HSA on d 0 (single); 2) 3.3 mg of PGF-HSA on d 0 and 28 (booster; B); 3) as (2) except on d 0 and 55; 4) as (2) except on d 0 and 83; and 5 to 8) as in Treatments 1 to 4 except using 10 mg of PGF-HSA. The adjuvant was diethylaminoethyl-dextran, and duration of the experiment was 170 d. Heifers were checked twice daily for EB. A persistent corpus luteum (CL) was considered present when progesterone (P4) was > or = .5 ng/mL for > or = six consecutive samples (every 3 to 4 d). Data were analyzed using ANOVA for a factorial plan. All heifers produced plasma antibody titers (samples every 2 wk) against PGF (peak range: 7 to 84% binding at 1: 1,250). There were no effects (P > .10) of conjugate dose and no interactions between dose and immunization regimen for any variable; therefore, data were combined across dose. Mean and peak titers were greater (P < .05) in heifers in 55- and 83-d B treatments than those in single immunization and 28-d B treatments. Overall, 48/55 heifers formed a persistent CL (41/41 for B heifers). In the single, and 55- and 83-d B treatments, 23/42 heifers formed persistent CL in response to single/primary immunization. There was no difference between immunization regimens in duration (133 +/- 4.4 d) of persistent CL.(ABSTRACT TRUNCATED AT 250 WORDS)

Interaction between dietary intake and ovariectomy on concentrations of insulin-like growth factor-I, GH and LH in plasma of heifers.

The objective of this study was to determine if alterations in dietary intake and(or) ovariectomy influence plasma concentrations of IGF-I, GH and LH in heifers. Cyclic heifers (n = 23) were individually fed for 10 wk either 1) 1.8% of body weight in dry matter per day (GAIN; n = 7) 2) 1.1% of body weight in dry matter per day (MAINT; n = 8); or 3) 0.7% of body weight in dry matter per day (LOSE; n = 8). After 10 wk of dietary treatment, heifers were ovariectomized 36 to 40 h following the second injection of prostaglandin F2alpha analog (2 injections 11 d apart). Heifers weighed 444 +/- 13, 387 +/- 8, and 349 +/- 9 kg in the GAIN, MAINT and LOSE groups, respectively, at the time of ovariectomy; the average daily weight gains during the 10-wk period were 0.96, 0.17 and -0.31 kg, respectively (P < 0.001), for the 3 groups. Blood plasma was collected for 6 h at 15-min intervals 1 d before and 2 wk after ovariectomy. The MAINT group of heifers had greater IGF-I concentrations than either the LOSE or GAIN groups; IGF-I decreased (P < 0.05) by 23 and 35% after ovariectomy in the MAINT and GAIN groups, respectively, but did not change (P > 0.10) in the LOSE groups. Dietary restriction tended to increase (P < 0.10) GH pulse frequency and mean GH. Ovariectomy had no effect (P > 0.10) on mean GH or GH pulse frequency but increased (P < 0.05) GH pulse amplitude in the GAIN groups. Dietary treatment had no effect (P > 0.10) on mean LH, or LH pulse amplitude and frequency. However, across dietary treatments, ovariectomy increased mean LH and LH pulse frequency but did not affect (P > 0.10) LH pulse amplitude. In summary, dietary restriction increased GH secretion while ovariectomy increased LH secretion. There appears to be a dichotomy of response between GH and IGF-I in the way heifers respond to dietary treatment and(or) ovariectomy.

Effects of growth hormone-releasing factor and(or) thyrotropin-releasing hormone on growth, feed efficiency, carcass characteristics, and blood hormones and metabolites in beef heifers.

The objective of this study was to determine the effect of long-term administration of a growth hormone (GH)-releasing factor analog (GRFa) and(or) thyrotropin-releasing hormone (TRH) on growth, feed efficiency, carcass characteristics, and blood hormones and metabolites in beef heifers. Crossbred heifers (n = 48; 345.9 +/- 2.8 kg) were divided into four equal groups: control (vehicle), 1 microgram of GRFa (human GRF 1-29 analog).kg BW-1.d-1, 1 microgram of TRH.kg BW-1.d-1, or GRFa + TRH. Daily s.c. injections continued for 86 d. Blood samples were collected from half of the heifers after injection on d 1, 36, and 78. On d 89, all heifers were slaughtered. Treatments did not affect (P > .05) ADG but GRFa + TRH decreased (P < .05) ADFI relative to all other treatments. Feed conversion efficiency tended (P < .10) to be improved in the groups given GRFa alone or TRH alone. Treatment with GRFa and(or) TRH did not affect carcass weight, dressing percentage, conformation score, backfat thickness, or weights of liver, kidneys, pituitary, and ovaries. The GRFa + TRH treatment reduced (P < .05) fat score and increased (P < .05) longissimus muscle area relative to other treatments. The GRFa treatments reduced (P < .05) the weight and fat percentage of the mammary gland and increased (P < .05) heart weight. Treatment with TRH alone failed to stimulate GH on d 1, 36, and 78. Treatment with GRFa alone increased (P < .05) GH above controls on d 36, whereas GRFa + TRH increased (P < .05) GH on d 1, 36, and 78. Treatment with GRFa alone increased (P < .05) IGF-I only on d 1, whereas GRFa + TRH was without effect on all days. Across sampling days, treatments had little effect on blood concentrations of insulin, triiodothyronine, nonesterified fatty acids, urea nitrogen, and glucose. The GRFa alone and GRFa + TRH decreased (P < .05) and TRH alone increased (P < .05) thyroxine concentrations. In conclusion, with the dose and administration regimen used, GRFa and(or) TRH yielded small but positive improvements in animal performance.

Systemic but not intraovarian concentrations of insulin-like growth factor-I are affected by short-term fasting.

To determine whether systemic and/or intraovarian concentrations of insulin-like growth factor-I (IGF-I) are affected by short-term fasting, 24 heifers were blocked by weight and, within block, were assigned to one of three treatments: fasted for 0 h (controls; n = 8), fasted for 24 h (n = 8), or fasted for 48 h (n = 8). Blood plasma was collected every 8 h from -64 h to 0 h before ovariectomy (OVEX). OVEX was performed per vagina under local anesthesia during the follicular phase of an estrous cycle (36-42 h after synchronization with prostaglandin-F2 alpha). Follicular fluid (FFL) and granulosa cells were collected individually from follicles greater than or equal to 6 mm (large), and FFL was pooled from follicles 1.0-5.9 mm (small) in diameter. Fasting did not affect (p greater than 0.20) the number (mean +/- SE) of small (52 +/- 7) or large (1.5 +/- 0.4) follicles per heifer, specific binding of 125I-hCG to granulosa cells of follicles greater than or equal to 8 mm in diameter, or concentrations of progesterone in FFL of small follicles. At OVEX, body weight was less (p less than 0.01) for 24 h- and 48 h-fasted heifers (412 +/- 7 kg and 399 +/- 7 kg, respectively) than for 0 h-fasted heifers (442 +/- 7 kg). At OVEX, plasma concentrations of IGF-I were lower (p less than 0.05) in the 48 h-fasted group (105 +/- 8 ng/ml) than in the 0 h-fasted group (140 +/- 8 ng/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of estradiol, trenbolone acetate, or zeranol on growth rate, mammary development, carcass traits, and plasma estradiol concentrations of beef heifers.

The effect of a single implantation (on d 1) with one or two long-acting, biodegradable estradiol implants (1E or 2E) on plasma estradiol concentrations in beef heifers was determined. The growth rates of these (2E) heifers, and of heifers repeatedly implanted with trenbolone acetate (TBA) or zeranol (Z) on d 1, 84, 168, and 252 of the trial, were compared to growth rates of controls. Trenbolone acetate alone was compared to TBA + 2E, and 2E was compared to 1E. At a mean age of 84 d (d 1 of experiment), 81 Hereford x Friesian heifers were allocated at random to the following treatments: Control (n = 15); TBA (n = 15); 1E (n = 12); 2E (n = 15); Z (n = 13); or TBA + 2E (n = 11). Mean live weight (kg) prior to slaughter on d 368 and hot carcass weight (kg) for heifers assigned to treatment Groups 1 to 6, respectively, were 366 and 200, 391 and 212, 374 and 201, 386 and 207, 387 and 210, and 391 and 208 (residual SD = 30.3 and 20.2). Heifers assigned to both the 2E and Z treatments were heavier on d 368 (P less than .05) and had longer teats on d 279 (P less than .05), less pelvic fat (P less than .05), and heavier kidneys (P less than .005) than control heifers. Heifers assigned to the TBA treatment had shorter teats on d 279 (P less than .001) but greater final live weight (P less than .05) and carcass weight than control heifers. Heifers given TBA alone had more pelvic fat (P less than .05) and lighter kidneys (P less than .05) than those given TBA + 2E. Mean estradiol concentrations in both the ipsilateral and contralateral jugular veins of heifers assigned to the 2E and TBA + 2E treatments, and in the ipsilateral jugular veins of heifers given 1E, were greater (P less than .05) than those in control heifers; concentrations did not decline during the experiment.

Effects of oestradiol, zeranol or trenbolone acetate implants on puberty, reproduction and fertility in heifers.

The effects of anabolic agents on reproduction in beef heifers were determined by using 300 mg trenbolone acetate (TBA), 36 mg zeranol and 19 mg oestradiol-17 beta in a biodegradable pellet (1E: American Cyanamid, USA), or two such pellets (2E). On Day 1 of experiment, 81 Hereford x Friesian heifers (mean age = 84 +/- 1.2 days) were allocated at random to the following treatments: (1) controls (N = 15); (2) TBA (N = 15); (3) 1E (N = 12); (4) 2E (N = 15); (5) zeranol (N = 13); (6) TBA + 2E (N = 11). The 1 (1E), or 2 (2E) oestradiol implants were administered on Day 1 of the experiment only. Heifers assigned to receive TBA and zeranol were implanted on Days 1, 84, 168 and 252. Blood progesterone concentrations and oestrous activity were monitored from Days 137 and 200 respectively. Mean age (days) and weight (kg) at puberty (first ovulation), for heifers that reached puberty in Groups 1-6 respectively were 352 and 308, 419 and 356, 373 and 325, 381 and 331, 400 and 353, 423 and 383 [residual standard deviation (r.s.d.) = 43.8 and 39.4 for age and weight respectively]. Heifers in Group 4 were older (P less than 0.05), but not heavier (P greater than 0.05), while those in Groups 2 and 5 were both older (P less than 0.005) and heavier (P less than 0.005) than the controls at puberty. Age and weight at puberty were not different in heifers assigned to Groups 3 and 4, or to Groups 2 and 6. The proportion of heifers showing oestrus before puberty (prepubertal oestrus) were 3/15, 12/15, 6/12, 7/15, 10/13 and 11/11 in Groups 1-6 respectively. Heifers in Groups 2 and 5 had higher incidences of prepubertal oestrus than controls, while those in other treatment groups were not different. There was no treatment effect on the incidence of silent ovulations, but the incidence of non-ovulatory oestrus, after puberty, was increased from 4/48 in Group 1 to 26/40 (P less than 0.001), 15/56 (P less than 0.05) and 34/57 (P less than 0.001) in Groups 2, 4 and 5, respectively. Heifers in Group 6 had a higher incidence of non-ovulatory oestrus (P less than 0.05), but not of prepubertal oestrus, than did those in Group 2.(ABSTRACT TRUNCATED AT 400 WORDS)

Control of estrus in dairy cows with a synthetic analogue of prostaglandin F2 alpha.

Trials were carried out on 1184 dairy cows calved at least six weeks before treatment and 255 heifers to determine effectiveness of the prostaglandin analogue, cloprostenol to control estrus. In trial 1, following two injections of cloprostenol given 12 days apart, there was no difference in calving rate following AI either at 72 and 96 hr after treatment (71 163 ) or at a detected estrus (53 118 ) compared to control cows bred at estrus (54 110 ). In trial 2, treated cows were injected once after 5 to 7 days of estrous detection and AI. The calving rate following AI either at 72 and 96 hr after cloprostenol (46 100 ) or at a detected estrus (39 71 ) was similar to that in control cows bred at estrus (45 86 ). In trial 3, cows were bred at a detected estrus after the first cloprostenol injection. Twelve days after this injection, cows not bred were given a second injection and bred 72 and 96 hr later. The calving rate in treated cows bred at estrus after the first injection (66 138 ) was similar to calving rate in controls (55 95 ). However, calving rate in cows given a second injection and bred 72 and 96 hr later was significantly (P angle 0.05) lower (30 98 ). Similar results were obtained in heifers, except calving rate in trial 3 after the second cloprostenol injection was not reduced.

Synchronisation of oestrus and pregnancy diagnosis in heifers bred in autumn and winter.

The calving rate to artificial insemination following administration of progesterone or prostaglandin was influenced by ovarian activity at the start of the treatment. Significantly more heifers inseminated on a fixed time basis after a 12-day progesterone treatment calved compared to synchronised or control heifers inseminated at a detected oestrus. Administration of 10 mg oestrogen intravaginally by gelatin capsule attached to the progesterone-containing coil or injection of 5 mg oestrogen and 200 mg progesterone at the start of the 12-day progesterone treatment did not influence the oestrous response of calving rate. The accuracy of detection of non-pregnant heifers by oestrous detection, measurement of progesterone in blood 21 days after AI or rectal examination varied from 90 to 93 per cent. However, both oestrous detection and the progesterone test identified significantly fewer non-pregnant heifers. Rectal examination as a method of diagnosing pregnant heifers was significantly more accurate than either of the above.

Calving rate following fixed time insemination after a 12-day progesterone treatment in dairy cows, beef cows and heifers.

Farm trials were carried out to determine if cows and heifers could be inseminated on a fixed time basis following a 12-day treatment with progesterone coils and an injection of 5 mg oestradiol benzoate and 200 mg progesterone at the start of treatment. The retention rate of the coils was significantly higher (P less than 0.05) when a 5.5 cm diameter was used compared with a diameter of 7.0 cm. Calving rate was similar in treated cows bred at a detected oestrus, at 56 + 74 hours after treatment or at 56 hours after treatment and injection of 100 microgram gonadotrophin releasing hormone 20 hours previously and in control cows bred at oestrus. Fertility to the first repeat oestrus was also similar in treated and control cows. Significantly (P less than 0.05) more synchronised cows calved following fixed time AI compared with the calving rate in control cows inseminated for a 24-day experimental period. In beef suckler cows, calved at least 50 days, and dairy heifers weighing over 280 kg, calving rate was similar in treated animals bred at 56 and 74 hours after treatment compared to calving rate in control animals bred at oestrus.