Photosensitization of cattle in southeast Texas: identification of phototoxic activity associated with Cooperia pedunculata

A microbiological assay (Candida albicans) was used to screen plants in southeast Texas where bovine photosensitization (PS) of unknown cause was a recurring problem. Phototoxic activity was identified associated with dead leaf tips of Cooperia pedunculata, a native, perennial forb of the Amaryllis family (Amaryllidaceae) from central, southeast, and south Texas and parts of Mexico. A syndrome compatible with naturally occurring PS in cattle was induced in laboratory mice after oral administration of dead leaf material from C pedunculata. Availability and phototoxic activity of dead leaf material of C pedunculata corresponded with occurrence of PS in cattle. Seemingly, C pedunculata was involved in recurring PS.     

Hematology and biochemistry reference values for female Holstein cattle.

Reference intervals are presented for 14 hematology and 32 biochemistry variables from four age groups of female Holstein cattle (n = 172) selected randomly from six well managed farms. Each animal was examined by a clinician and with the history available considered to be clinically normal at the time of blood collection. The variable observations were examined for outliers and Gaussian distribution prior to parametric or where necessary, nonparametric analysis. Many differences were noted between age groups but few between farms.     

Neutralising antibody to herpesviruses dervied from wildebeest and hartebeest in wild animals in East Africa.

The sera of 728 game animals, collected in East Africa, were tested for neutralising antibody to a strain (WC11) of wildebeest herpesvirus, which is an important cause of malignant catarrhal fever of cattle. In addition, 290 of these sera were tested for neutralising activity against a closely related herpesvirus (K/30) from hartebeest (Alcelaphus sp.). Antibody was frequently present in three species of the subfamily Alcelaphinae (wildebest, hartebeest and topi) and one of the subfamily Hippotraginae (oryx). No activity was found in the sera of nine other species of four additional subfamilies. The proportion of hartebeest sera positive for WC11 virus (60 per cent) was not significantly different from that neutralising the K/30 isolate (77 per cent) and antibody titres against the two agents did not differ significantly. Of 62 topi sera 40 per cent neutralised WC11 virus, while all of three oryx sera were positive. It is suggested that the antibody detected in hartebeest, topi and oryx was induced by infection with viruses related to, but not identical with, the WC11 and K/30 strains. Some characteristics of the latter indicated that it was not the usual herpesvirus of hartebeest and may have been derived from wildebeest. It is proposed that the group of viruses involved should be provisionally designated as 'alcelaphine herpesviruses' in order to separate them from the rest of the 'bovid' herpesviruses, a name proposed by the Herpesvirus Sbucommittee of the International Committee on the Nomenclature of Viruses.     

Haemonchus contortus infection in sheep: parasite fecundity correlates with worm size and host lymphocyte counts

Two experiments were conducted to elucidate the timing and nature of the sheep immune response to Haemonchus contortus (Barber's pole worm). The first experiment examined the establishment of H. contortus populations and the immune response by comparing a bolus infection of third-stage larvae in na?ve sheep with a group previously primed by a trickle infection. The second experiment used staggered doses of ivermectin-resistant larvae to compare the development of adult worms during different durations of trickle infection with ivermectin-sensitive larvae. Infections successfully generated pathological signs of haemonchosis such as anaemia. Image analysis software was used to measure the area and perimeter of worms collected at post-mortem, and the number of eggs present in individual adult females (fecundity) was significantly correlated with worm size. A significant inverse correlation was found between blood lymphocyte counts and worm fecundity. The absence of correlation between worm fecundity and other leukocyte and erythrocyte counts highlighted the specificity of the lymphocyte response. This is the first report of a link between haematology profiles and worm fecundity in haemonchosis. The correlation observed between adult worm size and egg content leads to the hypothesis that egg production in H. contortus is limited by immune regulation of worm size and presumably growth. Mean worm size and fecundity declined as sheep received more prolonged trickle infections before necropsy, confirming previous reports that immune responses to adult worms are enhanced by ongoing larval challenge. Immunohistochemical results showed trends consistent with a Th2 (humoral) immune response which has been implicated in reducing nematode burdens in several species.     

Effectiveness of controlled internal drug release device treatment to alleviate reproductive seasonality in anestrus lactating or dry Barki and Rahmani ewes during non‐breeding season

This study aimed to evaluate the effectiveness of hormonal treatments on ovarian activity and reproductive performance in Barki and Rahmani ewes during non‐breeding season. Forty‐eight multiparous ewes, 24 Barki and 24 Rahmani ewes were divided into two groups, 12 lactating and 12 dry ewes for each breed. Controlled internal drug release (CIDR) device was inserted in all ewes for 14 days in conjunction with intramuscular 500 IU equine chronic gonadotrophin (eCG) at day of CIDR removal. Data were analysed using PROC MIXED of SAS for repeated measures. Breed, physiological status and days were used as fixed effects and individual ewes as random effects. Barki ewes recorded higher (p < .05) total number of follicles, number of large follicles, serum estradiol concentration and estradiol: progesterone (E₂:P₄) ratio compared to Rahmani ewes. Lactating ewes recorded higher (p < .05) number of small follicles and lower concentration of total antioxidant capacity (TAC) compared to dry ewes. Number and diameter of large follicles recorded the highest (p < .05) values accompanied with disappearance of corpora lutea at day of mating. Serum progesterone concentration recorded lower (p < .05) value at day of mating and the highest (p < .05) value at day 35 after mating. CIDR‐eCG protocol induced 100% oestrous behaviour in both breeds, but Rahmani ewes recorded longer (p < .05) oestrous duration compared to Barki. Conception failure was higher (p < .05) in Barki compared to Rahmani ewes. In conclusion, CIDR‐eCG protocol was more potent in improving ovarian activity in Barki compared to Rahmani ewes, but this protocol seems to induce hormonal imbalance in Barki ewes that resulted in increasing conception failure compared to Rahmani ewes.