Effect of husbandry methods on seropositivity to African swine fever virus in Sardinian swine herds

Multiple logistic regression was used on serological data collected in the context of the Sardinian African swine fever (ASF) eradication program from pig farms in the province of Nuoro, Sardinia. The monthly percentage of ASFV-positive herds decreased significantly from October 1994 through March 1996 (P < 0.001). The farm-level risk of seropositivity to African swine fever virus (ASFV) was higher in free-range farms than in partial-confinement farms (odds ratios (OR) varied between 4.9 in October 1994, and 5.7 in March 1996, P < 0.001). The risk of infection for total-confinement farms was one-fifth of the risk for partial-confinement farms in October 1994 (OR = 0.2, P < 0.001), whereas in March 1996, the estimated OR was 0.57 and not significant (upper confidence limit = 1.1). The maintenance of ASFV in Sardinia was primarily associated with free-range pig farms. The natural logarithm of the number of pigs tested per visit in a farm was positively associated with the risk of herd seropositivity (OR = 2.6, P < 0.001).     

Prolactin signaling in porcine adrenocortical cells: involvement of protein kinases

Prolactin (PRL) was found to have a stimulatory effect on adrenal steroidogenesis in vivo and in vitro in several species including pigs. PRL signal transduction pathways, however, in adrenocortical cells are poorly recognized. Therefore, the goal of this paper is to ascertain the involvement of protein kinase C (PKC) and tyrosine kinases in PRL signaling in porcine adrenal cortex. Adrenals were harvested from locally slaughtered mature gilts. Cortical cells were dispersed by sequential treatment with collagenase. The cells were seeded into 24-well culture plates at a density of 3×10⁵/mL. Cells were incubated with or without PRL (500 ng/mL), ACTH (5 nM—a positive control), tyrosine kinase inhibitor—genistein (1; 2.5 or 5 μM), PKC inhibitor—sphingosine (20–1000 nM) and PKC activators—diacylglycerol (DiC8; 10–100 μM) and phorbol ester (PMA; 1–1000 nM). All incubations were performed for 8 h (95% air and 5% CO₂, 37°C). PRL and ACTH (P<0.05) increased cortisol and androstenedione (A₄) secretion. DiC8 and PMA mimicked the stimulatory effect of PRL. Sphingosine (P<0.05) suppressed basal and PRL-stimulated steroid secretion. Genistein inhibited (P<0.05) PRL-stimulated cortisol secretion and enhanced (P<0.05) basal and PRL-stimulated A₄ secretion. Moreover, PKC activation was assessed by measuring the specific association of [³H]phorbol dibutyrate ([³H]PDBu) with adrenocortical cells after treatment with PRL or ionomycin (a positive control). PRL (within 2–3 min) and ionomycin (within 2–5 min) increased (P<0.05) specific binding of [³H]PDBu to the porcine adrenocortical cells. In addition, PRL did not augment the cortisol and A₄ secretion by PKC-deficient adrenocortical cells. In conclusion, presented results support the hypothesis that PKC and tyrosine kinases are involved in PRL signaling in adrenocortical cells in pigs. Moreover, activation of PKC is associated with the increased secretion of cortisol and A₄.     

Plasma concentrations of ACTH precursors correlate with pituitary size and resistance to dexamethasone in dogs with pituitary-dependent hyperadrenocorticism

This study was performed to determine whether in dogs with pituitary-dependent hyperadrenocorticism (PDH) excessive release of adrenocorticotrophic hormone (ACTH) is accompanied by secretion of ACTH precursor molecules. In addition, we investigated whether the plasma ACTH precursor concentrations were correlated with the size of the pituitary gland and with the degree of resistance to negative glucocorticoid feedback. In 72 dogs with PDH, the plasma ACTH precursor concentration was determined by calculating the difference between the results of a radioimmunoassay (RIA) in which besides ACTH, ACTH precursors were also measured and a highly specific immunoradiometric assay (IRMA) using a polyclonal antibody against ACTH. The degree of resistance to glucocorticoid feedback was established by determining the effect of dexamethasone administration (0.1 mg/kg) on the urinary corticoid/creatinine ratio. The pituitary height/brain area (P/B) ratio, determined by computed tomography, was used as a measure for the size of the pituitary gland. The plasma ACTH precursors concentration ranged from 18 to 2233 ng/L (median 93 ng/L). In 38 dogs, the pituitary was enlarged and plasma ACTH precursors concentrations in these dogs (median 130 ng/L, range 24–2233 ng/L) were significantly (P<0.05) higher than those in the dogs without pituitary enlargement (median 72 ng/L, range 18–481 ng/L). In concordance, P/B ratios correlated significantly with plasma ACTH precursor concentrations (r=0.35, P<0.01). In addition, the P/B ratios were significantly correlated with the degree of dexamethasone resistance (r=0.42, P<0.001). Plasma ACTH precursor concentrations in the dexamethasone-resistant dogs (median 210 ng/L, range 24–628 ng/L) were significantly higher (P<0.01) than those in the dexamethasone-sensitive dogs (median 72 ng/L, range 18–2233 ng/L). Similarly, the degree of dexamethasone resistance was also significantly correlated with the plasma ACTH precursor concentrations (r=0.33, P<0.01). Dogs with an elevated plasma -MSH concentration (n=14) had significantly (P<0.001) higher plasma ACTH precursor concentrations (median 271 ng/L, range 86–2233 ng/L) than dogs with non-elevated -MSH (median 73 ng/L, range 18–481 ng/L). In addition, the plasma concentrations of -MSH correlated significantly with both plasma ACTH precursor concentrations (r=0.53, P<0.001) and P/B ratios (r=0.26, P<0.05). In conclusion, in all dogs with PDH the ACTH concentrations determined by the RIA were higher than the concentrations measured by IRMA indicating the presence of circulating ACTH precursors. High plasma ACTH precursor concentrations were especially found in dexamethasone-resistant dogs with large corticotroph adenomas, some of them probably of PI origin. In the association of large corticotroph adenoma, dexamethasone resistance and high plasma concentrations of ACTH precursors, the decreased sensitivity of the corticotroph cells to glucocorticoid feedback may play a pivotal role.     

Mammary uptake and excretion of prostanoids in relation to mammary blood flow and milk yield during pregnancy-lactation and somatotropin treatment in dairy goats

Mammary arterious − venous differences (A − V) and excretion into milk of four prostanoids were related to changes in milk yield and milk vein blood velocity (MBV) in goats at different stages of pregnancy and lactation, and during somatotropin (ST) treatment in mid-lactation. Arterial concentrations and mammary A − V for the vasodilators prostacyclin (PGI₂) and prostaglandin (PG) E₂ (measured as 6-keto-PGF₁ and bicyclic PGE₂, respectively) decreased from late pregnancy to lactation. A − V were negatively correlated to MBV (r = −0.32 to −0.34). Arterial concentrations of the vasoconstrictors PGF₂ and TXA₂ (measured as TXB₂) changed similarly, but no A − V across the mammary gland were found. The vasodilator to vasoconstrictor ratio in plasma was around 1:1, and in skimmed milk around 0.29–0.49 due to significantly higher TXB₂ levels in milk compared to plasma. Close linear correlations were established between milk yield and excretion of TXB₂ into milk (r = 0.80, P < 0.001), and between MBV and PGE₂ excretion into milk (r = 0.69, P < 0.001). ST treatment stimulated MBV and mammary prostanoid supply, and decreased prostanoid concentration in milk vein plasma. The high arterial levels of prostaglandins during pregnancy most likely reflected uterine synthesis. Our results support a role for PGI₂ and PGE₂ in local mammary blood flow regulation during lactation. Increased mammary uptake of these two prostanoids may be involved in the mammary blood flow response to ST. TXA₂ may be synthesized by mammary epithelial as well as vascular cells, and TXA₂ may be an important factor in regulation of mammary function.     

Effect of progressive cachectic parasitism and growth hormone treatment on hepatic 5'-deiodinase activity in calves

Thyroid status is compromised in a variety of acute and chronic infections. Conversion of thyroxine (T₄) into the metabolically active hormone, triiodothyronine (T₃), is catalyzed by 5′-deiodinase (5′D) mainly in extrathyroidal tissues. The objective of this study was to examine the effect of protozoan parasitic infection (Sarcocystis cruzi) on hepatic 5′D (type I) activity and plasma concentrations of T₃ and T₄ in placebo- or bovine GH (bGH)-injected calves. Holstein bull calves (127.5±2.0 kg BW) were assigned to control (C, ad libitum fed), infected (I, 250,000 S. cruzi sporocysts per os, ad libitum fed), and pair-fed (PF, non-infected, fed to intake of I treatment) groups placebo-injected, and three similar groups injected daily with pituitary-derived bGH (USDA-B-1, 0.1 mg/kg, i.m.) designated as C_GH, I_GH and PF_GH. GH injections were initiated on day 20 post-infection (PI), 3–4 days prior to the onset of clinical signs of the acute phase response (APR), and were continued to day 56 PI at which time calves were euthanized for liver collection. Blood samples were collected on day 0, 28, and 55 PI. Alterations in nutritional intake did not affect type I 5′D in liver. Treatment with bGH increased (P<0.05) 5′D activity in C (24.6%) and PF (25.5%) but not in I calves. Compared to PF calves, infection with S. cruzi reduced 5′D activity 25% (P<0.05) and 47.8% (P<0.01) in placebo- and bGH-injected calves, respectively. Neither nutrition nor bGH treatment significantly affected plasma concentrations of T₄ and T₃ on day 28 and 55 PI. However, plasma thyroid hormones were reduced by infection. On day 28 PI, the average plasma concentrations of T₃ and T₄ were reduced in infected calves (I and I_GH) 36.4% (P<0.01) and 29.4% (P<0.05), respectively, compared to pair-fed calves (PF and PF_GH). On day 55 PI, plasma T₃ still remained lower (23.7%, P<0.01 versus PF) in infected calves while plasma T₄ returned to control values. The data suggest that parasitic infection in growing calves inhibits both thyroidal secretion and extrathyroidal T₄ to T₃ conversion during the APR. After recovery from the APR, thyroidal secretion returns to normal but basal and bGH-stimulated generation of T₃ in liver remains impaired.     

Effect of menhaden fish oil supplementation and lipopolysaccharide exposure on nursery pigs. I. Effects on the immune axis when fed diets containing spray-dried plasma

The objective of the present study was to evaluate the potential immunological benefit of adding menhaden fish oil to the diet of weaned pigs. Twenty-four crossbred male pigs were weaned at approximately 18 days of age and placed on a complex nursery diet containing 30% lactose and 7% plasma protein with 6% corn oil as the fat source (Cont, n=12) or with 5% menhaden fish oil and 1% corn oil as the fat source (MFO, n=12) for a period of 15 days. Body weights did not differ (P>0.78) between dietary groups either at the beginning or end of the 15 days feeding period. On day 15, all pigs were non-surgically fitted with an indwelling jugular catheter. On d 16, pigs received an i.v. injection of either saline (n=6/dietary group) or lipopolysaccharide (LPS; 150 μg/kg body weight; n=6/dietary group) and blood samples were collected at 30 min intervals for a period of 5 h. Serum was harvested and stored at −80 °C for analysis of cortisol (CS), corticosteroid-binding globulin (CBG), tumor necrosis factor-alpha (TNF-) and interferon-gamma (IFN-γ). There was no significant effect of diet on basal concentrations (Time 0) of any of the blood parameters analyzed. A Time×Treatment×Diet interaction (P<0.03) was observed for serum CS such that those pigs which consumed the MFO diet followed by LPS treatment had a reduced CS response as compared to the LPS-treated pigs on the Cont diet. A Time×Treatment interaction (P<0.01) was observed for serum CBG such that LPS treatment reduced circulating CBG as compared to the saline-treated pigs. Time×Treatment×Diet interactions were also observed for serum concentrations of TNF- (P=0.084) and IFN-γ (P=0.022) such that both the TNF- and IFN-γ response to the LPS challenge was lower in those pigs receiving the MFO diet as compared to the LPS-treated pigs on the Cont diet. Overall, serum CS was negatively correlated with the CBG response (r=−0.40, P<0.001), however, the strongest negative correlation was observed in the LPS-treated pigs which consumed the MFO diet (r=−0.63, P<0.001). While further studies are needed to evaluate the immunological response of including MFO in the nursery pig diet, the present study demonstrates that supplementation with MFO does indeed alter the immunological response to an LPS challenge.     

Administration of recombinant porcine somatotropin (rpST) changes hormone and metabolic status during early pregnancy

The objective of this study was to examine the effects of somatotropin (ST) on porcine reproductive and metabolic statuses during early pregnancy. Four pregnant crossbred gilts received 6 mg of recombinant porcine somatotropin (rpST) daily from days 10 to 27 after artificial insemination while six pregnant gilts served as controls. Blood samples were taken on days 8, 10, 12, 14, 18, 22, and 27 prior to rpST injections (8:00 h) and subsequently at 9:00, 10:00, 12:00, 14:00, 16:00, 18:00, and 20:00 h. On all remaining days of treatment, samples were taken once daily before injections (8:00 h). The samples were assayed for the metabolic hormones: ST, insulin-like growth factor I (IGF-I), insulin, thyroxine (T₄), triiodothyronine (T₃), and cortisol; for metabolites: free fatty acids (FFA) and glucose; and for the reproductive hormones: luteinizing hormone (LH), progesterone, estradiol-17β, estrone sulfate, and prostaglandin F₂. Delivery of rpST daily induced a 20- to 40-fold increase in plasma ST concentrations. Moreover, repeated administration of rpST resulted in a continuous increase in plasma IGF-I concentration (P<0.001), from 191.0±22.3–340.0±15.3 ng/mL 24 h after initial injection to 591.3±46.8 ng/mL after final injections. Mean serum insulin tended to be greater in rpST-treated gilts. Blood concentrations of T₄ were reduced (P<0.05) from day 14 of gestation in treated gilts while T₃ concentrations remained unchanged. Concentrations of both glucose and FFA were greater (P<0.01) and cortisol concentrations were unchanged in treated gilts. Changes in reproductive steroid hormones were minimally affected. Circulating progesterone (P=0.078), and estradiol-17β (P=0.087) concentrations tended to be lower in treated animals. These data show that treatment of pregnant gilts with rpST during early gestation mainly impacts metabolic rather than reproductive status.     

Factors associated with time under quarantine for swine herds in the voluntary phase of the Illinois pseudorabies eradication program

The association of herd characteristics and intervention strategies with time under quarantine was evaluated for 163 farrow-to-finish swine herds enrolled in the voluntary phase (1986–1987) of the pseudorabies virus (PRV) eradication program in the state of Illinois (USA). Vaccination was the intervention strategy used most widely (69% of herds), particularly in larger herds. Depopulation was used primarily when PRV seroprevalence was high, and test-and-removal when seroprevalence was low. Approximately 50% of the herds were released from quarantine within 3 years of developing a herd clean-up plan.

Multiple regression analysis using the Cox proportional hazards model indicated the following. Vaccination had a strong association with a longer time until release from quarantine (P<0.001). This is attributed to the lack of a vaccine differential test during this time, which made diagnosis of natural infection more difficult. Offspring segragation was associated with a longer time under quarantine (all herds: P=0.05; non-vaccinated herds: P=0.004). Delay in implementation of a herd clean-up plan was also associated with longer time under quarantine (all herds: P=0.012; non-vaccinated herds: P<0.001). Herds with higher seroprevalence at the time of agreement to a herd plan required a longer time under quarantine (all herds: P<0.001). This result was apparent for non-vaccinated herds (P=0.001), and thus is not merely a consequence of vaccination. Herds in areas with a high geographic density of quarantined herds required a longer time before release from quarantine (all herds: P=0.003), although this trend was not apparent for non-vaccinated herds (P=0.39). After taking PRV seroprevalence into account, there was no apparent association of time under quarantine with sow herd size (all herds: P=0.057; non-vaccinated herds: P=0.81) or confinement housing (all herds: P=0.19; non-vaccinated herds: P=0.91).     

Release of tumor necrosis factor-alpha from bovine alveolar macrophages stimulated with bovine respiratory viruses and bacterial endotoxins

The release of tumor necrosis factor-alpha (TNF-) from cultured bovine alveolar macrophages (BAM) was evaluated following stimulation of BAM with bovine herpesvirus-1 (BHV-1), parainfluenza-3 (PI-3) virus, bovine respiratory syncytial virus (BRSV), Escherichia coli 0111:B4 endotoxin, Pasteurella haemolytica type 1 endotoxin, Pasteurella multocida endotoxin, and virus/endotoxin combinations. A cytotoxic assay system using Georgia bovine kidney cells as targets was used to measure TNF- activity. The cytotoxic activity was neutralized by an anti-human TNF- monoclonal antibody.

Stimulation of BAM with 1 median tissue culture infectious dose (TCID₅₀) of live or ultraviolet (UV)-inactivated PI-3 virus/cell resulted in release of TNF- in significantly (P<0.05) higher amounts than sham-induced BAM. The quantities of TNF- released after live or UV-inactivated BHV-1 or BRSV induction were not significantly higher than sham-induced BAM. E. coli 0111:B4, P. haemolytica type 1 and P. multocida endotoxins stimulated TNF- release in a dose-dependent manner. Sequential exposure of BAM to 1 TCID₅₀ per cell of either live BHV-1, PI-3 virus or BRSV and then 5 μg ml⁻¹ of either E. coli 0111:B4, P. haemolytica type 1 or P. multocida endotoxin caused a significant (P<0.05) reduction in detectable TNF- in seven of nine virus/endotoxin combinations tested, when compared with 5 μg ml⁻¹ of endotoxin alone. Parainfluenza-3 virus/endotoxin combinations stimulated higher TNF- release when compared with other virus/endotoxin combinations. Five out of six test animals had serum-neutralizing antibodies to PI-3 virus, one out of six had serum-neutralizing antibodies to BHV-1, and two out of six had serum-neutralizing antibodies to BRSV, suggesting a possible relationship between serum neutralizing antibodies and TNF- release from in vitro cultivated BAM.     

A survey of gastrointestinal parasites in cattle of southeastern Nigeria

This paper presents the results of a survey of 1021 cattle in the southeastern area of Nigeria during August–October 1990 (wet season) and January–March 1991 (dry season) to study the effects of season, ecological zone, management system, breed and age on the occurrence of gastrointestinal parasites (GIP).

Strongyles (mainly Haemonchus spp.) were the commonest GIP (prevalence 47.8%; 95% CI; 44.8–51%; mean eggs per gram (epg) 387 ± SE 21.3) followed by coccidia (3.6%; 95% CI, 2.6–5%; mean oocysts per gram (opg) 2077 ± 778.4). The prevalence of other parasites encountered was comparatively very low. More infections were present in the wet than in the dry season (P<0.01). Whereas a higher prevalence (P<0.01) of strongyle infection was recorded in nomadic herds, that of coccidia was higher in sedentary herds. The prevalence of strongyle infection was lower in young animals (P<0.05), but they had higher epg (P<0.01) and also higher coccidia prevalences (P<0.01) than adults. Friesian and N'dama breeds under improved management in modern farms had lower strongyle and higher coccidia infections compared with zebu and muturu kept under the traditional management system The distribution of infection by ecological zone did not show any consistent trend, and this was attributed to the uneven distribution of the cattle breeds amongst the different zones.     

The repeatability of faecal egg counts in Polish Wrzosówka sheep

The number of nematode eggs in the faeces was estimated in Polish Wrzosówka sheep, in the spring and autumn of 1993 and again in 1994. The sheep had been naturally infected. The dominant species were Haemonchus contortus and Teladorsagia circumcincta, but Trichostrongylus spp., Cooperia curticei, Nematodirus spp. and Chabertia ovina were also present. Anthelmintics were not used. Egg counts were skewed, with a range of 0–4100 eggs g⁻¹ (EPG); most sheep had egg counts below 100 EPG. Egg counts were approximately four times higher in spring than in autumn. Repeatability values within a season were all significant and positive. The repeatability of egg counts between seasons was estimated from the correlation between the mean transformed value in spring and in autumn, and was 0.52 in 1993 (P < 0.001) and 0.41 in 1994 (P < 0.05). The results show that animals with higher than average values in spring are likely to have higher than average values in autumn, and suggest that similar mechanisms regulated egg counts in both seasons even though egg counts were much lower in autumn.     

Suboptimal reproductive performance of dairy cattle kept in smallholder herds in a rural highland area of northern Tanzania

The objectives of the present study were to assess the reproductive performance and cumulative incidence risk of reproductive disorders and to compare the success of artificial insemination (AI) to natural service (by handmating; NS) in dairy cattle kept in smallholder herds under a zero-grazing system in a rural highland area of Tanzania. Data on occurrence of all normal and abnormal reproductive events were collected for 215 adult animals belonging to 74 households.

The median and range of the intervals: intercalving, calving to first service, and calving to pregnancy were 477 (335–860), 154 (38–486) and 206 (61–567) days, respectively. Breed and parity did not affect the reproductive parameters (P>0.05). However, cows in the milked group had a shorter median calving interval than those in the suckled group (P<0.001). The overall percentage pregnant and the percentage pregnant to first service were higher in the NS than in the AI group (49 vs. 32%; P=0.007) and (67 vs. 25%; P<0.001), respectively. The median numbers of services per pregnancy were not different between the AI (3) and NS (2) groups (P=0.17). The cumulative incidence risk of abortion, dystocia, prolapse, retained fetal membranes, mastitis, milk fever and cyclic non-breeders were 16.0, 1.7, 2.5, 4.2, 5.0, 1.7, and 6.1%, respectively. Hoof overgrowth (4.6%) and hoof deviation (4.6%) were the most-frequent digital problems. We concluded that reproductive parameters and cumulative incidence risk of abortion show suboptimal reproductive performance in rural-based, zero-grazed smallholder dairy herds in Tanzania particularly those using AI.     

Influence of gonadotropins on insulin- and insulin-like growth factor-I (IGF-I)-induced steroid production by bovine granulosa cells

To determine the effect of gonadotropins on insulin- and insulin-like growth factor (IGF-I)-induced bovine granulosa cell functions, granulosa cells from bovine ovarian follicles were cultured for 2 days in the presence of 10% fetal calf serum (FCS), and then cultured for an additional 2 days in serum-free medium with added hormones. In the presence of 0 or 1 ng/mL of insulin or IGF-I, FSH had little or no effect (P>0.05) on estradiol production by granulosa cells from both small (1–5 mm) and large (≥8 mm) follicles. However, in the presence of ≥3 ng/mL of insulin, FSH increased (P<0.05) estradiol production by granulosa cells from small and large follicles such that the estimated dose (ED₅₀) of insulin necessary to stimulate 50% of the maximum estradiol production was decreased by 2- to 3-fold from 22 to 28 ng/mL in the absence of FSH to 7–14 ng/mL in the presence of FSH. Similarly, in the presence of ≥3 ng/mL of IGF-I, FSH increased (P<0.05) estradiol production by granulosa cells from small and large follicles such that the ED₅₀ of IGF-I for estradiol production was decreased by 4- to 5-fold from 25 to 36 ng/mL in the absence of FSH to 5–6 ng/mL in the presence of FSH. In the presence of FSH, the maximal effect of insulin on estradiol production was much greater than that of IGF-I (137- versus 12-fold increase) and were not additive; when combined, 100 ng/mL of IGF-I completely blocked the stimulatory effect of 100 ng/mL of insulin. In the absence of FSH, the maximal effect of insulin and IGF-I on estradiol production was similar. Concomitant treatment with 30 ng/mL of LH reduced (P<0.05) insulin-stimulated estradiol production by 52% on day 1 and 19% on day 2 of treatment. Insulin, IGF-I and FSH also increased (P<0.05) granulosa cell numbers and progesterone production but their maximal effects were less (i.e., <4-fold increase) than their effects on estradiol production. In conclusion, insulin and IGF-I synergize with FSH to directly regulate ovarian follicular function in cattle, particularly granulosa cell aromatase activity.     

Intrauterine infusion of BQ-610, an endothelin type A receptor antagonist, delays luteolysis in dairy heifers

Three separate in vivo experiments were conducted to evaluate the putative role of endothelin-1 (ET-1) during luteal regression in heifers. In Experiment 1, a single intraluteal injection of 500 μg BQ-610 [(N,N-hexamethylene) carbamoyl-Leu-d-Trp (CHO)-d-Trp], a highly specific endothelin A (ET_A) receptor antagonist, did not diminish the decline in plasma progesterone following a single exogenous injection of 25 mg prostaglandin F2 alpha (PGF₂) administered at midcycle of the estrous cycle. In Experiment 2, six intrauterine infusions of 500 μg BQ-610 given every 12 h on days 16–18 delayed spontaneous luteolysis, as evidenced by an extended elevation (P = 0.054) of plasma progesterone concentration. In Experiment 3, heifers were administered six intrauterine infusions of BQ-610 or saline on days 16–19, and peripheral blood samples were collected from day 11 to 16 (before infusion), hourly on days 16–19 (during infusion), and on days 20–25 (after infusion). BQ-610 treated heifers had markedly higher (P < 0.0001) levels of plasma progesterone compared with saline controls, and this effect was most notable during the infusion period (treatment by period interaction; P ≤ 0.05). Heifers infused with BQ-610 also had higher progesterone levels on day 21 (treatment by time interaction; P ≤ 0.05). Mean plasma concentrations of 13,14-dihydro-15-keto-PGF₂ (PGFM), the primary metabolite of PGF₂, were measured in the samples collected hourly and were not different (P ≥ 0.05) between treatments. These results indicate that the in vivo antagonism of the ET_A receptor can delay functional luteolysis, and supports the theory that ET-1 regulates luteal function in ruminants.     

Correlation between carcass conformation and fat cover degree, and muscle fatty acid profile of yearling bulls depending on breed and mh-genotype

The objective was to study the relationships between the actual European beef carcass classification scale, which classifies carcasses with regard to conformation and degree of fat cover scores, and muscle fat quality, depending on breed and mh-genotype. For this purpose samples from 100 yearling bulls from “Asturiana de los Valles” (24 AV(mh/mh), 26 AV(mh/+), 25 AV (+/+)) and “Asturiana de la Montaña” (25 AM) were analysed. The results of the study showed that breed or genotype affect carcass measurement scores and muscle fatty acid profile through its important effect on animal overall fatness. Homozygous double-muscled animals produced carcasses with high conformation and low intramuscular (IM) fat content. While early-maturing and rustic AM animals produced low carcass yield and high IM fat content. The other genotypes (mh/+, +/+) showed, in general, intermediate characteristics. Referring to correlations, carcass conformation was negatively related to saturated (SFA) (r = − 0.69, P < 0.001) and monounsaturated fatty acid (MUFA) (r = − 0.69, P < 0.001) groups, and positively to polyunsaturated (PUFA) (r = 0.72), n-6 (r = 0.72), n-3 (r = 0.71) and unsaturated fatty acid (UFA) (r = 0.69) groups, being all of them significant (P < 0.001). However, carcass degree of fat cover was positively related to SFA (r = 0.53, P < 0.001) and MUFA (r = 0.62, P < 0.001), and negatively to PUFA (r = − 0.61), n-6 (r = − 0.60), n-3 (r = − 0.62) and UFA (r = − 0.53) groups, being all of them significant. Moreover, simple and low-cost prediction equations were calculated for a rapid and sufficiently accurate fatty acid group (SFA, MUFA, PUFA, n-6, n-3, UFA) estimation (R² > 0.46, P < 0.001). In general, meat obtained from double-muscled animals display a more appropriate IM fatty acid profile from the nutritional point of view according to actual recommendations, but it could happen the disability of these lean animals to deposit sufficient IM fat to ensure consumer overall liking or acceptability.     

Feed-conversion ratio of finisher pigs in the USA

Although the feed-conversion ratio is recognized as a prominent indicator of profitability for pork producers, only 212 (50.7%) of 418 producers who were asked the feed-conversion ratio for finisher pigs provided a response during the USA National Animal Health Monitoring System 1995 National Swine Study. Of these, 126 (59.4%) producers furnished a feed-conversion ratio which they characterized as having been calculated from records, while 86 (40.6%) gave a response that they characterized as estimated or guessed. Feed-conversion ratios ranged from 2.18 to 5.91 kg of feed fed for each kg of live-body weight gained during the grower/finisher phase, with a mean of 3.28 and a standard deviation of 0.52. Stepwise regression revealed the following management factors to be associated with improved feed-conversion ratios: ≥3 different rations fed during the grower/finisher phase (P<0.01); no rations mixed on the farm (P<0.05); and not giving chlortetracycline in feed or water as a disease preventive or growth promotant (P<0.01). In addition, operations where ≥3000 pigs entered the grower/finisher-production phase during the six-month period prior to interview had a better mean feed-conversion ratio than operations where <3000 pigs entered the grower/finisher phase (P<0.01).     

Prevalence and epidemiology of selected enteric infections of livestock in Trinidad

In a study of diarrhoeic and non-diarrhoeic livestock (cattle, pigs and sheep) from 50 farms in Trinidad, the prevalence of bacterial (Campylobacter, Salmonella, Yersinia and Escherichia coli), parasitic (coccidia, Cryptosporidium and enteric helminths) and viral (rotavirus) enteropathogens in faeces or rectal swabs was determined. Occurrence of the enteropathogens was tested for association with age, health status, animal species and mixed infections.

Of 423 diarrhoeic animals tested, Salmonella was isolated from 21 (5.0%), Campylobacter from 191 (45.2%) and Yersinia from three (0.7%), while the corresponding prevalence from 270 non-diarrhoeic controls was eight (3.0%) (χ² 1.19, P = 0.28), 119 (44.1%) (χ² 0.04, P = 0.85) and four (1.5%) (χ² 0.8, P = 0.39), respectively. Verocytotoxigenic E. coli and heat-labile toxin-producing E. coli were isolated from 51 (13.7%) and five (1.3%), respectively, of 373 diarrhoeic animals but the corresponding prevalence from 258 non-diarrhoeic animals was 39 (15.1%) (χ² 0.15, P = 0.7) and five (1.9%) (χ² 0.07, P = 0.8), respectively. Cryptosporidium oocytes were detected in 67 (16.5%) of 406 diarrhoeic animals and from 31 (12.1%) of 257 non-diarrhoeic animals (χ² 2.13, P = 0.15). For 147 diarrhoeic animals tested for coccidia, 64 (43.5%) were positive compared with 34 (37.8%) of 90 non-diarrhoeic animals (χ² 0.54, P = 0.49).

The prevalence of rotavirus infection was significantly (P 0.001, χ² 37.8) higher in diarrhoeic animals (39.9%, 112 of 281) than in non-diarrhoeic animals (13.4%, 26 of 194).     

Effect of exogenous thyrotropin-releasing hormone (TRH) administration on plasma levels of triiodothyronine (T3), thyroxine (T4) and growth hormone (GH) in chronically catheterized suckling piglets.

The purpose of the present study was to determine experimental conditions to stimulate secretion of thyroid hormones (T₃ and T₄) with thyrotropin-releasing hormone (TRH) injections in suckling piglets during the first weeks of postnatal life. Three consecutive experiments were conducted. Four 10–20 d old piglets were i.m. injected with 0, 20, 100, 500 μg (experiment 1) or 0, 4, 20, 100 μg TRH/kg BW (experiment 2) according to a 4 × 4 latin square design involving different litters in each experiment. Blood samples were taken −15, −1, 15, 30, 45, 60, 90, 120 180 and 300 min after TRH injection in experiment 1, and −.25, −.08, .25, .5, 1, 2, 4, 6, 8, 12, 24, 30, 36, 48, 60 and 72 hr after TRH injection in experiment 2. T₃ and T₄ levels were significantly (P<.01) increased as soon as 30 and 45 min after TRH injection, respectively. Maximal levels of T₃ and T₄ were obtained 2 and 4 hr after the injection of 100 μg TRH. T₃ and T₄ returned to basal levels within 6 and 8 hr post injection, respectively. Plasma pGH levels were significantly (P<.001) increased 15 min after TRH injection in piglets injected with 500 μg. In experiment 3, 100 μg TRH/kg BW were injected i.m. either daily or every other day from .0 to 23 days of age. Results showed that T₄ response to TRH did not decrease after repeated injections. These results indicate that daily i.m. injections of 100 μg TRH/kg BW can be used to increase thyroid hormone levels for at least 13 d in the young suckling piglet.     

Effects of outdoor winter housing and feeding level on performance and blood metabolites of suckler cows fed whole-crop barley silage

The experiment studied the effects of long-term cold climatic housing conditions at a latitude of 62°N on pregnant Hereford cows and their progeny. Thirty-five cows in their third parity were overwintered in outdoor facilities with either a rain-shelter or a three-wall shelter, or in an uninsulated barn. Whole-crop barley silage was offered to the cows either ad libitum or restricted supplemented with oats. The dry matter intake on the restricted diet was 75% of that on the ad libitum diet. The cow live weight (LW) averaged 670 kg at the onset of the experiment. During winter the cows outdoors on the restricted diet maintained their LW while those on the ad libitum diet gained LW (P < 0.05, − 3 vs. 41 kg). On pasture, the LW gain (LWG) was 61 and 32 kg (P < 0.05) for the cows overwintered outdoors on the restricted and on the ad libitum diets, respectively. The initial body condition score (BCS, Scale: 0–5) of the cows averaged 2.90. During winter the cows outdoors on the restricted diet decreased and those on the ad libitum diet increased the BCS (P < 0.01, − 0.14 vs. 0.21). On pasture, the cows overwintered outdoors on the restricted diet increased the BCS more than those overwintered on the ad libitum diet (P < 0.05, 0.31 vs. 0.08). No signs of extraordinary stress, massive consumption of energy stores, frequent muscle injuries or severe inflammations occurred in any of the groups according to blood analyses of cows, e.g. cortisol, long-chain fatty acids, aspartate aminotransferase, creatine kinase and white blood cell count. The calving period was from 11 March to 21 April. Only one indoor calving was classified as difficult due to faulty disposition leading to the loss of the calf. All outdoor calvings were easy. The LWG of the indoor calves of cows on the ad libitum diet was poorer (P < 0.05) pre the grazing period than that of the outdoor calves of cows on the ad libitum diet. On pasture and during the entire experiment the LWG was similar for all calves, averaging 1335 and 1251 g/d, respectively. The breeding season was 82 days. Thirty cows out of 33 were observed to be pregnant after the mating period. All the facilities offered adequate shelter for the mature, pregnant suckler cows. The restricted offering of whole-crop barley silage provided, on average, 101 MJ metabolizable energy/d and gave enough energy for the cows.     

Effects of feeding linseed and linseed expeller meal to newly weaned piglets on growth performance and gut health and function

The effects were evaluated of the inclusion of full fat linseed (125 g/kg) (LS) or linseed expeller meal (85 g/kg) (LSM) in diets for weaned piglets on growth performance and parameters of gut health and function. The diets were fed to groups of 12 post weaning single housed piglets. Three of the five treatments (Control (C)+, LS+, LSM+) were challenged with an enterotoxigenic strain of E. coli on day 6. Two treatments were not challenged (C− and LS−). The main response criteria were daily feed intake, body weight gain, faecal shedding of the E. coli, faecal consistency score, faecal nutrient digestibility and gut wall morphology and histology of the jejunal mucosa on day 18/19 of the study. Over the total experimental period (day 0–18) feed intake and body weight gain were highest in treatment C− and lowest in treatment LSM+ (P < 0.05). Feed conversion ratio did not differ between treatments over the total experimental period. Over day 10–12 of the study, the faecal digestibility of dry matter, ash and energy was higher for treatments C− and C+ compared to treatments LS−, LS+ and LSM+ (P < 0.05). There was no significant difference in the faecal shedding of E. coli between treatments C+, LS+ and LSM+. Intestinal mucosal histology and morphology were only slightly affected by the dietary treatments. It was concluded that the use of full fat linseed or linseed expeller meal did not show to be functional ingredients in diets for post-weaning piglet in terms of supporting gut health.