Gastrointestinal parasites presence during the peripartum decreases total milk production in grazing dairy Holstein cows

Parasitism in cattle is known to impair growth and development. Recent findings suggest that productivity of adult animals is also affected, but little is known about the physiological mechanisms involved. Furthermore, development of nematode resistance to drugs makes imperative the search of management practices that avoid whole herd treatment. We undertook an epidemiological and endocrine study in a grass based dairy farm in Argentina to study the effect of parasites on milk production and the underlying mechanisms involved, and identify individual animals that would benefit from antiparasitic treatment. All the cows in the dairy were followed monthly for egg parasite output in feces. Samples were cultured for genera determination. Milk production and reproductive results were recorded and periodical bleedings for hormone determination were performed. Nematode egg output (EPG) was maximal in late Summer and Autumn and minimal in Spring in coincidence with the Ostertagia inhibition-disinhibition cycle as this genus had the highest prevalence in all the study. The highest proportion of positive samples was found in the high producing herd and maximal counts were found in the peripartal period. Milk production did not correlate with EPG mean values but, when cows were grouped by EPG positivity around parturition, a significant difference in total milk production between EPG null and positive cows was observed. Positive cows produced 7%, 12% or 15% less milk than null EPG cows, depending on the sampling month/s chosen for classification. The highest difference was seen when both prepartum and postpartum samples were taken into account. No difference in lactation length and a marginal effect on partum to first service interval were encountered. Endocrine studies revealed a decrease in serum growth hormone (GH), type I insulin-like growth factor (IGF-I) and prolactin during lactation in cows with positive EPG in the first postpartum sample with respect to null EPG cows at that time. GH levels decreased and prolactin and IGF-I levels increased in both groups of cows from month 0 to 6 in milk. Serum insulin levels remained stable throughout lactation and were similar in both groups of cows. In conclusion, EPG around parturition may be a useful tool for identifying cows that will have a decrease in productivity due to parasite effects and would possibly benefit from an antiparasitic treatment. Besides, our results suggest that detrimental effect of parasites on milk production may be mediated by GH, IGF-I and prolactin serum levels.     

Evaluation of 2 sources of Angus cattle under South Florida subtropical conditions

The objective of this study was to compare performance and aspects of adaptability attributes of cattle from a Florida Angus bloodline (local source from a mostly closed herd for over 50 yr) to cattle that are representative of modern Angus bloodlines (outside source) in US subtropical conditions. Embryos from both sources were transferred to Brahman-crossbred cows in South Florida, and calves (n=82) were born in 3 yr. Before weaning, summer tympanic temperatures were recorded hourly for 3 d in each year. Heifers were placed with fertile bulls until diagnosed pregnant. Traits relative to sexual maturation of bulls were recorded at 1- or 2-mo intervals until approximately 17 mo of age. Calves from outside sources had greater hip height at weaning than calves from the local source (P<0.001; 108.8 ± 0.62 and 104.7 ± 0.68 cm, respectively). Local-source calves (n=37) had greater (P=0.03) exit velocity (2.7 ± 0.3 m/s) than outside-source (n=45) calves (2.0 ± 0.29 m/s), which may be indicative of more nervous or temperamental disposition. However, no source differences were detected for other assessments of disposition (chute or pen score, P>0.8). Few source differences for minimum, maximum, or range of daily tympanic (inner ear) temperatures were detected. At 17 mo of age, outside-source heifers were heavier (P = 0.05) and had greater (P<0.001) hip height than Angus heifers from the local source. Heifers from the outside source were younger (P<0.001) at the time of their first conception (454 ± 17.5 d) than heifers from the local source (550 ± 16.9 d). Outside-source heifers also had greater (P<0.02) pregnancy and calving rates (0.7 ± 0.119 and 0.62 ± 0.125, respectively) from exposure to bulls within a year from weaning than the heifers from the local source (0.29 ± 0.089 and 0.19 ± 0.077, respectively). Bulls from the outside source were heavier (P=0.05) at 320 d of age than local-source bulls. From 14 through 17 mo of age, outside-source bulls had greater (P≤0.05) scrotal circumference and tended (P≤0.15) to be heavier than local-source bulls. There appeared to be no performance or adaptation advantages for the local-source Angus through 17 mo of age. The large source difference for age at first conception in heifers merits additional attention and comparison with cow lifetime production performance for the 2 sources.     

<Emphasis Type="Italic">Streptococcus uberis</Emphasis>-specific T cells are present in mammary gland secretions of cows and can be activated to kill <Emphasis Type="Italic">S. uberis</Emphasis>

The presence, phenotype and function of Streptococcus uberis-specific T cells in the mammary gland secretion (MGS) and blood of cows exposed to S. uberis were assessed. MGS T cells in the udder were purified and incubated with autologous blood monocytes as antigen-presenting cells (APC). Most cows, irrespective of prior S. uberis infection status and lactation status, were shown to have S. uberis-specific T cells both in MGS and in the blood. When cells from a subgroup of cows were studied, it was found that the S. uberis-specific T cells produced high levels of interferon-gamma (IFN-γ), but low levels of interleukin-10 (IL-10). A high percentage of responding T cells were of the CD8 ⁺ memory (CD45RO) subset. T cells from the MGS specific for S. uberis were propagated from animals during the drying off period and expanded in vitro using interleukin-2 (IL-2) and S. uberis antigens. This led to the accumulation of T cells of the CD8 ⁺ subset bearing memory cell markers (CD45A ⁻ , CD45RO ⁺ ), which released high levels of IFN-γ. Four of the five T cell lines derived from the MGS of three animals had substantial direct killing activity towards S. uberis in vitro. It is concluded that there is an emergence of S. uberis-specific bactericidal T cells in the MGS of cows after infection or environmental exposure to S. uberis. Vaccines aimed at activating and expanding this T cell population in the mammary glands of cattle may offer an avenue for the prevention of mastitis caused by S. uberis.     

Leukocyte counts in bronchoalveolar lavage fluid obtained from normal and Maedi–Visna‐infected sheep

Background: Bronchoalveolar lavage has proven helpful for the diagnosis of certain ovine diseases of the lungs. There is insufficient data concerning the leukocyte profile of bronchoalveolar lavage fluid (BALF) from MaediVisna infected sheep. Objective: The objective of this study was to assess the differential leukocyte profile of BALF associated with Maedi virus infection in sheep and to determine whether cytologic examination of BALF is an effective way to diagnose Maedi or determine the severity of lung lesions. Methods: BALF and serum samples were analyzed from 400 sheep. Sediment smears of bronchoalveolar lavage were stained with Diff‐Quik and examined microscopically to obtain a 200‐cell differential cell count. Serum was tested using a commercial kit for Maedi–Visna virus antibodies. Lung samples obtained at the time of slaughter were weighed and examined histologically. Results: Maedi‐infected sheep (n=267; seropositive with lung lesions) had a significantly higher percentage of lymphocytes and lower percentage of macrophages in BALF than normal sheep (n=133; seronegative and no lung lesions). These differences were significantly more severe in animals with advanced vs moderate lung lesions. Using classification trees, a cut‐off of 13.5% lymphocytes was predictive of Maedi infection and a cut‐off of 24.5% lymphocytes was predictive of advanced lung lesions. Conclusions: Cytologic examination of BALF is useful for the clinical diagnosis of Maedi in sheep and provides important information about the severity of the lung lesions.     

Diagnosis and surgical treatment of epidural neoplasms in two ataxic horses

Two cases of ataxia caused by epidural neoplasia diagnosed with myelography and histopathology are presented in this report. One horse was diagnosed with lymphohistiocytic lymphosarcoma and the other with haemangiosarcoma. In both cases, subtotal dorsal decompression was performed as part of their treatment protocol. One horse was subjected to euthanasia immediately after surgery; however, the other horse recovered well, with no gait abnormalities and a normal myelographic dye column seen at 6 months post surgery. Although both horses were ultimately subjected to euthanasia, subtotal dorsal decompression provides a potential surgical treatment for epidural neoplasia.     

Serosurvey of five viruses in chickens on smallholdings in Bangladesh

A serologic survey was undertaken in chickens in smallholdings in Bangladesh for avian influenza A virus (AIV), egg drop syndrome '76 virus (EDS'76V), infectious bronchitis virus (IBV), Newcastle disease virus (NDV) and reovirus (RV) in three phases: January 2002-May 2003, September 2003-August 2004, and August 2005-March 2006. Four hundred thirty-six sera collected in the 2nd phase, 295 in the first phase, 755 in the 1st plus 2nd phases and 295 in the 1st phase were investigated for AIV, EDS'76V, IBV and RV, respectively, using enzyme linked immunosorbent assays. All 854 sera collected in the three phases were screened for NDV using hemagglutination inhibition test. In chickens 20% were seropositive to AIV, 3% to EDS'76V, 74% to IBV, 88% to NDV, and 47% to RV. The seroprevalence in flocks was 23% to AIV, 6% to EDS'76V, 79% to IBV, 89% to NDV and 56% to RV. Twenty-five percent chickens had > or = 10log(2)HI titers to NDV.     

Evaluation of estimated genetic merit for carcass weight in beef cattle: Blood metabolites, carcass measurements, carcass composition and selected non-carcass components

In Ireland, a new beef genetic index has been developed. Growth rate is expressed as expected progeny difference for carcass weight (EPD_CWT) and is estimated on an across-breed basis. Cross-breeding of dairy cows with both Aberdeen Angus and Belgian Blue beef sires is widely practised. The objective of this study was to compare blood metabolites, slaughter traits and carcass composition of progeny from Holstein–Friesian dairy cows and Aberdeen Angus (AA), Belgian Blue (BB), Friesian (FR) and Holstein (HO) sires. The AA and BB sires were selected, within breed, to be of either high (H) or low (L) estimated genetic merit for carcass weight. A total of 170 male progeny from spring-calving cows and 42 sires (10 AA, 13 BB, 7 FR and 12 HO) were artificially reared indoors and managed together until the end of their second grazing season when they were assigned to either a Light (560 kg) or Heavy (620 kg) slaughter weight. Blood metabolite concentrations were measured six times throughout life and feed intake was recorded during the first and second winter. Carcass measurements and selected non-carcass components were recorded after slaughter and the right side of each carcass was dissected into lean, fat and bone. Differences in blood metabolite concentrations amongst genetic groups were negligible although there were some effects of the prevailing level of nutrition. M. longissimus area scaled for carcass weight was 0.220, 0.221, 0.260, 0.255, 0.212 and 0.208 (SE 0.004) cm²/kg for AAH, AAL, BBH, BBL, FR and HO, respectively. Carcass measurements scaled for carcass weight were greater for L, AA, HO and the dairy strains than for H, BB, FR and the beef breeds, respectively. There was no effect of estimated genetic merit for carcass weight on carcass composition. Statistically significant interactions between genetic merit and beef breed existed for some traits with the genetic merit effect largely evident for AA only. BB and the beef breeds had more lean, less fat and more high value lean in the carcass than AA and the dairy strains, respectively. It is concluded that genetic group had little effect on blood metabolite concentrations but there were some feeding level effects. Estimated genetic merit for carcass weight affected carcass weight, m. longissimus area and carcass measurements scaled for carcass weight but the effects were confined to AA. There were large effects of beef breed and dairy strain on carcass composition.     

经人工授精传播的猪病及其预防措施

猪人工授精技术（Artificial insemination,AI）已在集约化养猪生产国中得到了广泛应用。人工授精是一种将优秀基因引入母猪群中的非常有效的工具,并能够将疾病传播的风险降至最小。然而,受到病原体污染的精液对生产实际的危害是巨大的。在已经从公猪精液中检测到的微生物中,大部分是非致病性的,但有一些是有名的病原体,如猪繁殖与呼吸综合症病毒,这部分病原体能给养猪业造成重大的经济损失。精液受到微生物的污染可能是由于公猪全身性感染和/或泌尿生殖道感染所致,或可能发生在精液采集、处理和存储过程中。这会导致精液品质下降,胚胎或胎儿死亡,以及受体母猪的子宫内膜炎和全身性感染和/或发病。用于从精液中分离细菌和病毒的常规技术因受多种原因的影响并不总是能获得理想的结果,这些原因包括所用技术缺乏敏感性和检测速度慢、对检测结果难以进行解释。近年来,PCR技术得到了普遍的应用,它们具有很高的敏感性,能很快获得检测结果,并且适合对大样本的检测。防止通过人工授精传播疾病的最佳方法是使用无特定病原体的公猪、对它们及其精液进行定期检测以及维持极高的生物安全水平。其它方法则应该侧重于利用合适的抗菌剂对精液进行处理,以及重点减少在采集、处理和存储过程中精液所受到的污染。