Nitrate poisoning in cattle grazing crops

Extract

Although nitrate/nitrite poisoning of cattle, sheep and pigs has been recognized in New Zealand for many years, it has become more widely publicized in the past 2 years owing to the greater prevalence of poisoning and the involvement of hitherto unsuspected crops, notably ‘Grasslands Tama’ ryegrass. In this review, experiences with recent outbreaks of nitrate poisoning are compared with published observations. Throughout this paper the disease will be referred to as nitrate poisoning.     

春草嫩绿应操心防制黄牛亚硝酸盐中毒

为了提高春季黄牛嫩绿牧草亚硝酸盐中毒的防制意识和诊治水平,杜绝亚硝酸盐中毒给黄牛养殖带来重大损失,文章阐述了黄牛亚硝酸盐中毒的发病机理,分析了病因,描述了现场检查方法,提出了急救措施,具体了源头预防,对防制黄牛亚硝酸 盐中毒有一定的实际指导意义。     

Lantana poisoning of cattle and sheep in New Zealand

The investigation of a field case of Lantana camara poisoning in cattle is reported. Toxicity was confirmed by the experimental dosing of two sheep with dried leaf powder at 6 and 12 mg/kg body weight. Marked cholestatic hepatophy and renal tubular disease resulted. This is the first reported case of toxicity due to grazing a Lantana camara variety grown in New Zealand.     

Self-Regulation of Supplemental Feed Intake by Grazing Dairy Cows and its Effect on Animal Performance

Abstract

Grazing Norwegian Red dairy cows were offered one of two roughage supplements ‘baled silage (S) or ryegrass (R)’ on an ad libitum basis for a limited period daily. A third group received concentrate (C). Milk and FCM yields were significantly (P<0.05) influenced by treatment (23.65 and 22.81, 23.20 and 22.05 and 22.58 and 22.73 kg d^?1, for S, C and R, respectively). Milk composition was unaltered. The cattle offered ryegrass consumed significantly (P<0.05) more supplementary feed and less pasture, and spent less time grazing and more time ruminating than the other two groups. Cattle with high initial yields, despite higher intakes of both pasture and supplement, had reduced liveweight gains and a faster decline in milk production in comparison with low yielders.     

Conditioned feed aversion as a means to prevent tulp (Homeria pallida) poisoning in cattle

Conditioned feed aversion was investigated as a means to prevent tulp (Homeria pallida) poisoning in cattle on tulp-infested grazing. Aversion treatment with a combination of epoxyscillirosidin and lithium chloride together with a tulp-hexane extract, which served as identification factor for tulp, resulted in a significantly lower (P < 0.001) proportion of severe tulp poisoning. In a first trial where 21 averted and 21 non-averted control cattle were exposed to a tulp-infested grass pasture, only two of the averted cattle were severely poisoned compared to 13 of the non-averted control cattle. In a second trial, with cattle being exposed to a pure stand of tulp supplemented with maize residues, only two of 21 averted cattle were severely poisoned compared to 14 of 21 non-averted control cattle. Occurrence of mild tulp poisoning, however, did not differ much between averted and non-averted control cattle. The results show that conditioned feed aversion effectively restricted severe poisoning in cattle on tulp-infested grazing.     

Effect of grazing frequency and intensity on Lolium perenne L. pastures under subtropical conditions: Herbage quality

Abstract

The cellulase dry matter disappearance (CDMD) and herbage nitrogen (N) of Lolium perenne (perennial ryegrass) were evaluated for pastures grown under subtropical conditions for two years, under five combinations of grazing frequency and intensity, each applied in a rotational grazing system. These quality factors were also evaluated for a simulated continuous grazing (CG) system. Low frequency, low intensity grazing produced lower CDMD and herbage N levels than higher grazing frequencies and intensities. These differences were, however, generally small. Overall, levels of herbage digestibility (estimated by CDMD) and N fell within similar ranges to those observed for perennial ryegrass in temperate environments. Seasonal trends in quality were characterized by high levels during late autumn to early summer (May to October) and low levels during mid‐summer to early autumn (January to April). These data would tend to support high frequency grazing as part of the management programme for perennial ryegrass. It is cautioned, however, that for subtropical conditions in South Africa, adopting frequent grazing may reduce persistence of perennial ryegrass.     

Ryegrass staggers in Canadian wapiti deer

Extract

Sir:- We would like to report an outbreak of ryegrass staggers in Canadian wapiti (Cervus elaphus mannitobensis) which occurred at the Invermay Agricultural Research Centre, Mosgiel. As far as we are aware this is the first recorded case of ryegrass staggers in deer associated with grazing perennial rye grass (Lolium perenne L.).     

Consumption of Low Larkspur (Delphinium nuttallianum) by Grazing Sheep

Low larkspur (Delphinium nuttallianum Pritz.) poisoning causes serious economic loss to livestock producers that graze cattle on foothill and mountain ranges in western North America. In general, all Delphinium spp. are five times less toxic to sheep than to cattle. Because low larkspurs are less toxic to sheep than cattle, grazing sheep before cattle on rangelands with dense populations of low larkspur can reduce larkspur density and risk of poisoning to grazing cattle. All previous published work on sheep and larkspur interactions has involved tall larkspurs. This series of studies was conducted to determine if sheep would consume sufficient low larkspur to reduce subsequent risk to cattle. Four summer trials were conducted in Collbran, Colorado, and Soda Springs, Idaho on pastures with dense (> 9 plants · m^?2) low larkspur populations. In all trials, sheep ate very little low larkspur (< 0.5% of bites). During one final trial using high sheep density (two sheep · 0.015 ha^?1 for 9 d), sheep consumed little low larkspur, but animals appeared to trample much of the low larkspur. Toxic alkaloid concentrations in low larkspur ranged from 1.1 mg · g^?1 to 1.6 mg · g^?1 in all trials. The use of sheep to graze low larkspurs to reduce subsequent consumption by grazing cattle does not appear to be a viable option.     

Increase in plasma total antioxidant capacity of grazing Japanese Black heifers and cows in forestland in Japan

Blood total antioxidant capacity (TAC) has become a key bio‐marker for animal health. Forest‐grazing cattle are known to forage various native plants that have high TAC. This study evaluated differences of plasma TAC between forest‐grazing (FG) and pasture‐grazing cattle (PG). Experiment 1 monitored the plasma TAC levels of 32 Japanese Black cattle. The level in PG did not change throughout the grazing period. However, that in FG, which increased from summer, was significantly higher than that in PG through fall (P < 0.05). In experiment 2, we used nine Japanese Black heifers and investigated their blood antioxidant parameters and the TAC in plants that the cattle consumed in late June and September. The plasma TAC levels in FG were significantly higher than those in PG in both periods (P < 0.05). Plasma levels of lipid peroxidation in FG tended to be lower than that in PG (P = 0.098). Furthermore, the TAC levels in various species of shrubs and trees consumed by FG were higher than those in pasture grasses. Results of this study show that plasma TAC of grazing Japanese Black cattle in forestland increase from summer through fall.     

Prolactin assay for fescue toxicity in sheep

Fungal endophyte (Acremonium spp.) toxicity affects sheep and cattle grazing a number of forages, including ryegrasses (Lolium spp.) and tall fescue (Festuca nrundinacea). The endophyte in tall fescue is responsible for ill thrift, as indicated by low weight gains or weight loss⁽¹⁾ and decreased reproductive efficiency⁽²⁾, and is associated with increased body temperatures. Extensive research has been undertaken in the USA to determine ways of reducing the impact of fescue toxicity on the beef industry⁽³⁾, whilst New Zealand research is directed toward both ryegrass and fescue endophyte toxicity and its impact on sheep⁽⁴⁾⁽⁵⁾ and cattle⁽⁶⁾ production. Much of this work involves field evaluations of productive performance in animals fed toxic and non-toxic forage, so that it is important to be sure that treatment effects are due to the endophyte.     

Effects of concentrate or ryegrass-based diets (Lolium multiflorum) on the meat quality of lambs grazing on semi-natural pastures

Abstract

With the objective of studying the effects of production systems on meat quality, 75 Norwegian White Sheep lambs were subjected to one of the following treatments: continuous grazing on a semi-natural lowland pasture until slaughtering (Control); continuous grazing followed by either stall-feeding on concentrate and grass silage or grazing ryegrass pasture for 44 or 24 days before slaughtering (Conc44, Conc24, Rye44, Rye24). Loin samples of M. longissimus dorsi including the subcutaneous fat were analysed for sensory attributes and fatty acid composition. Compared with the control group, a lower intensity of acid taste (P<0.05) and a lower content of C18:3n-6 fatty acids (P<0.001) were observed in the Conc44 group. The n-6/n-3 ratio was higher (P<0.001) in meat tested from the concentrate treatments compared to the ryegrass treatments. These findings indicate that the fattening of lambs on improved pastures or a concentrate-based diet prior to slaughter may alter meat characteristics.     

Seasonal variations in the cyanide content of Poa aquatica

Abstract

Extract

Sir,—Cattle deaths from cyanide poisoning have resulted from the ingestion of reed sweet-grass, Poa aquatica (Sharman, 1967 Sharman, J. R. 1967. Cyanide poisoning in cattle grazing reed sweet-grass. N.Z. vet. J., 15: 7–7. [Taylor &; Francis Online] , [Google Scholar]). Samples of leaves from this plant, gathered at approximately monthly intervals throughout the year, have now been analysed for their cyanide content.     

肉牛食用桃树叶中毒的诊治体会

桃树是我国广泛分布的树种,当牛在放牧或圈养时食用了较多的桃树枝叶,可引起中毒,以春季新鲜牧草缺乏时发病较多,且不分品种和年龄均可发病,多于采食后数小时至数天内发病。笔者从医几年来,偶遇两例牛误食桃树枝叶中毒病例,现将诊治体会分享如下。     

A survey of bovine cysticercosis/human taeniosis in Northern Turkana District, Kenya

Bovine cysticercosis is a zoonosis that is mainly of socioeconomic and public health importance. A survey of this disease was carried out in Northern Turkana District, Kenya to estimate the prevalence through both serology and meat inspection, to determine the prevalence of the adult tapeworm in the human definitive host, and to determine risk factors for cattle seropositivity. This information is of public health importance and will be of use in assessing economic losses due to downgrading, refrigeration or condemnation of infested carcasses.The study area was stratified into the three livestock grazing regions of Oropoi to the south, Lokichoggio–Mogilla centrally and Kibish in the north for the purposes of the serological and questionnaire (n = 53 herd owners) data. Five adakaars (grazing units) were selected and 34, 63, 49, 75 and 571 cattle serum samples obtained from these. The slaughter slabs of Lokichoggio and Kakuma were visited and 188 serum samples were obtained from slaughter cattle and compared to results of meat inspection. Human stool samples were collected in each of the three grazing areas and 66, 97 and 78 samples were obtained.The seroprevalence of cysticercosis in cattle was estimated at 16.7% (95% CI 13–20.9%) using a secretory–excretory antigen detection ELISA. There was poor agreement between meat inspection and serology (k = 0.025; p = 0.2797). The prevalence of taeniosis was estimated as 2.5% (95% CI 0.8–5.6%) by microscopy.A backwards elimination logistic regression analysis indicated that the grazing unit (Adakaar), the deworming history of household members and the distance (>2 km) of grazing fields from the homestead were significant explanatory variables for cattle being found to be positive on serology. An intra-cluster correlation coefficient (ICC) of 0.07 (0.02–0.12); p < 0.0001 was calculated for bovine cysticercosis in this area.     

Survey of brucellosis at the wildlife–livestock interface on the Zimbabwean side of the Great Limpopo Transfrontier Conservation Area

A cross-sectional study was conducted to determine the seroprevalence of bovine brucellosis in communal cattle and wildlife at a wildlife–livestock interface in the southeast lowveld of Zimbabwe, part of the Great Limpopo Transfrontier Conservation Area. RBT and c-Elisa were used in serial for detection of antibodies against Brucella spp. Between July 2007 and October 2009, a total of 1,158 cattle were tested and the overall seroprevalence of brucellosis was 9.9%. A total of 97 wild animals (African buffaloes (n = 47), impala (n = 33), kudu (n = 16), and giraffe (n = 1)) were tested and only one animal (giraffe) was seropositive for brucellosis (1.03%). Brucella seroprevalence showed an increasing trend with age, with adult cattle (>6 years) recording the highest seroprevalence (11.1%), but the differences were not statistically significant. Similarly, female cattle recorded a relatively higher seroprevalence (10.8%) compared to males (7.9%), but the difference was not significant. However, a significant (P < 0.001) association between Brucella seropositivity and abortion history was recorded in female cattle. Similarly, Brucella seropositivity was significantly (P < 0.01) associated with a history of grazing in the park for female cattle. Overall, from the interface area, cattle with a history of grazing in the park recorded a significantly (P < 0.01) higher Brucella seroprevalence (13.5%) compared to those with no history of grazing in the park (4.9%). The significant association between abortion history and seropositivity observed in this study illustrates the potential economic significance of Brucella in cattle in this area. Hence, public awareness and further epidemiological studies of the disease in wildlife, livestock, and humans in the study area are of great importance.     

The effect of mixed or sequential grazing of cattle and sheep on the faecal egg counts and growth rates of weaned lambs when treated with anthelmintics

An experiment was conducted over two successive years (2002 and 2003) to investigate the effects of grazing improved permanent pasture (mainly perennial ryegrass/white clover) by cattle or sheep, either sequentially or mixed, on the faecal egg counts and growth rates of weaned lambs when treated with anthelmintics. The grazing season was divided into two parts, May-July then July-October, relating to the pre- and post-weaning of the lambs. Four grazing regimes, replicated three times, were compared: (1) sheep only from May to October (SS); (2) cattle May to July followed by lambs until October (C/S); (3) cattle and sheep May to July followed by lambs until October (C+S/S); and (4) cattle and sheep May to July followed by cattle and lambs until October (C+S/C+S). Sward height was maintained at 6 cm using a "put and take" stocking system. At weaning, lambs were weighed and treated with an anthelmintic (0.08% ivermectin drench, Oramec) before being allocated to plots. They were then weighed and drenched every 28 days until the end of the experiment (Day 84). Faecal egg counts (FEC) were measured in all lambs immediately prior to each anthelmintic treatment. In 2002 and 2003, there were differences between the groups in FEC, with the SS lambs having the highest values and C/S lambs the lowest (P<0.01). There were also differences in the rate of liveweight gain of the lambs in each of the study years: for this parameter SS lambs had the lowest growth rate but the fastest growth was in C+S/C+S lambs not C/S lambs (P<0.01), indicating that these differences were due to factors other than parasite infection. Overall, sequential grazing of pastures with cattle then sheep reduced the faecal egg counts in lambs regularly treated with anthelmintics when compared with lambs grazing in mixed systems with cattle and sheep or with sheep only systems, however, the highest growth rates were observed in lambs in the mixed cattle/sheep grazing system throughout.     

Effects of sheep and cattle alternate grazing on sheep parasitism and production

Production of sheep (nursing ewes) grazing alternately with cattle (growing weaned heifers) was compared to the production of sheep or cattle grazing alone (controls). Pasture production and sheep parasitism were also monitored. The herbage allowance was higher for the control heifers than for the alternate heifers, but the leaf to green material ratio (LGMR) was lower, and no difference on heifer growth was revealed (443 vs. 431g.d^-1, P = 0.54). The LGMR was higher for the alternate sheep (+3 points) than for the control sheep, except during the dry season, when the herbage density was lower. The effects of parasitism on the packed cell volume of alternate ewes and lambs were lower than those of control ewes and lambs. However, the infection of sheep by Cooperia sp. (better adapted to cattle) was significantly higher for the alternate sheep than for the controls, and some indication of cattle infection by Haemonchus contortus was suggested. The 70-day lamb weight was higher in the alternate grazing system than in the control (+0.76,+1.11 and+0.61kg for the dry, intermediate and rainy seasons, respectively), and the average 70-day lamb production per ewe exposed was 21.42kg in the alternate grazing system vs. 18.59kg in the control (P = 0.003).     

Risk Factors Associated with the Occurrence of Bovine Tuberculosis in Cattle in the Southern Highlands of Tanzania

A study was conducted in the Southern Highlands of Tanzania to determine the prevalence of bovine tuberculosis and the risk factors associated with the occurrence of the disease in cattle of different categories and in different climatic zones. The overall prevalence of the disease was 13.2%, and 51% of the herds tested contained reactor cattle. Assessment of risk factors was based on comparisons of the reactivity of the cattle in the single comparative intradermal tuberculin test (SCITT). Older cattle were more affected by the disease than yearlings and calves (p<0.0001). There were significant differences between male and female cattle (p<0.05) and between cattle with exotic blood compared to indigenous Short Horn Zebu (SHZ) cattle (p<0.05). The castrated bulls, often used for draught power, were more frequently (p<0.01) affected than the entire bulls, mainly used for breeding. Reactivity to tuberculin did not appear to be influenced by the reproductive status of the animal. The reactivity to tuberculin of pregnant cattle was not significantly different from that of the rest of the cows (p>0.05). However, significantly more (14.6%) lactating cattle reacted in the SCITT than did non-lactating cows (12.0%) (p<0.05). There was a highly significant difference (p<0.001) between reactivity in the SCITT among cattle grazing in the hot and dry lower lands (14.0%) and that in those grazing in the cool and wet highlands (8.7%).     

Ethics,legislation and profit as determinants of conservation farming

Grazing behaviour and diet selection of cattle were studied on a communally grazed floodplain and its adjacent wooded uplands in western Zambia to identify the interaction between basic herd management practices, foraging behaviour and body condition of cattle. On average, the cattle spent nine hours and 29 minutes (SD = 27 minutes) outside the kraal, with a range from about 8 hours in the dry season to almost 11 hours in the wet season, depending on the morning temperature and milking time. A significant (P<0.001) linear relationship between the time spent outside the kraal and time spent grazing was found. The Echinochloa spp.-Vossia cuspidata grass association was intensively grazed for the largest part of the year (44% of the total grazing time). During the flood season cattle grazed largely along the floodplain edge instead of the adjacent woodlands, which resulted in a negligible intake of browse. Body condition of all categories of cattle was significantly lower during the flood season. It was concluded that during this season cattle should graze more hours daily than they presently do, to minimise the drop in body condition as much as possible, and to make more intense use of the forage resource of the woodland.     

Poisoning of cattle by amaranthus

Extract

Sir, — The July issue of the journal contained a letter on the above subject that caught my attention. It seems that the author is unaware of reports of poisoning by redroot in New Zealand and I thought it appropriate to draw his attention to them. Brackenridge (1956 Brackenridge, D. T. 1956. Nitrate poisoning caused by turnips and red-root. N.Z. vet. J., 4: 165–166.  [Google Scholar]) reported an outbreak of nitrate poisoning in cattle grazing redroot and turnip tops and the following year Coup and I published on poisoning by these two plants and green oats. We also reported experimental poisoning of three cows with red root. Duckworth's findings are similar to those reported in previous outbreaks. As I recall, in the 9 years I was in the diagnostic section at Ruakura, these were the only recorded cases of nitrate poisoning in cattle. The infrequency of redroot poisoning may be a reflection of the small chance that all the conditions necessary to induce it rarely occur at the same time.