Trichostrongyle larval populations on herbage from grazed and ungrazed cattle pastures in south west Scotland

In the course of studies on the control of bovine parasitic gastroenteritis in south west Scotland using a morantel sustained release bolus the populations of trichostrongyle infective larvae on herbage were monitored over a two-year period. From the results of the herbage analysis and the worm burdens in parasite naive tracer calves introduced at the end of 18 months, it was clear that considerable numbers of infective larvae of Ostertagia ostertagi and Cooperia oncophora survived for at least 18 months on pastures not grazed at all. The results suggest that in south west Scotland after one, or even two, seasons with no further contamination of grazing, permanent cattle pastures cannot be assumed to be helminthologically 'safe' and that this should be taken into consideration when determining prophylactic strategies.     

Very low helminth infection in sheep grazed on pastures fertilised by sewage sludge or cattle slurry

Helminth infection acquired by lambs grazing on pastures fertilised either by urban sewage sludge or cattle slurry were studied in temperate Central Western France. The aim was to assess the risk of larval cestodoses in lambs after sewage application and of digestive tract nematode infection following the slurry application. Twenty-six sheep were allocated on two paddocks of 0.7 ha, one fertilised with sludge and the other with cattle slurry. The delay between application and actual grazing was 6 weeks; grazing on these paddocks extended from mid July to beginning of November 2002. The herbage biomass was slightly increased in the sludge paddock but it did not result in an increase of lamb live weight, compared with the slurry paddock. The lambs did not acquire cysticercosis or any other larval cestodoses in the sewage sludge group and only very limited infections with Cooperia spp. and Nematodirus spp. were observed in the slurry group. It was concluded that in our conditions the helminth risk was extremely low and was not a cause of restriction of the use of these biowastes.     

Analysis of factors affecting milk yield of Ankole cows grazed on natural range pastures in Uganda

Effects of seasonal rainfall (RF) and maximum temperature (T_m) variations on milk yield of Ankole cows grazed solely on range pastures were investigated. The resulting changes in herbage growth (HG), herbage yields (HY), herbage crude protein (CP_h) and neutral detergent fibre (NDF_h), as well as body condition score (BCS) of ten milking cows taken every two weeks were analysed for their correlation with milk yield (MY). Results showed that MY was significantly correlated (P = 0.05) with BCS and NDF_h, but not with RF and CP_h. The correlation with T_m, HY and HG were not significant.

Multiple linear regression analysis showed that milk yield increased with body condition and declined with herbage yield according to the model: MY = 3.70?BCS–3.90?HY–6.67. This implied that throughout most of the year, cows depended on mobilisation of body reserves built in the wet season to meet the requirements for milk production. As herbage matured, milk yield declined because cows could not maintain the dietary quality needed for optimal digestion and feed intake. Cows fed to maintain good body condition yielded more milk. Therefore, to minimise maturity, appropriate stocking rates should be applied to maintain young herbage and sustain milk yield.     

Faecal excretion of Salmonella hadar from calves grazed on pastures fertilised with S. hadar-contaminated broiler litter

The risk of Salmonella hadar infection in weaned calves grazed on pasture artificially contaminated with the organism via broiler litter applied at commercial dressing rates was assessed. A group of four calves was grazed on artificially contaminated pasture and a control group was grazed on an adjacent identical paddock. A ninth calf was given S. hadar together with an anthelmintic drench, and a tenth was fed on a mixture of contaminated broiler litter and hay for 36 hours. Rectal swabs were collected from the calves at weekly intervals and examined for the presence of salmonellae. Two of the calves in the group on contaminated pasture and both the control positive calves shed S. hadar in their faeces on at least one occasion. The S. hadar contamination was detectable on the pasture for at least 42 days after application of the contaminated litter.     

Efficiency of Duddingtonia flagrans against Trichostrongyle infections of sheep on mountain pastures

The control of sheep nematode parasites in extensive mountain/transhumant management systems using the nematophagous fungus Duddingtonia flagrans was assessed in this study. Two groups of Churra Tensina ewes were allowed to graze for 8 weeks in autumn on two separate paddocks of infected pasture near their winter sheds in the valley. At lambing, ewes and their twin lambs were turned out into the same paddocks for the following 12 weeks. One group of ewes received a daily dose of 5 x 10(5) chlamydospores of Duddingtonia flagrans/kg live weight per day both in autumn and in spring, while the other group was used as a non-treated control. Daily dosing of grazing ewes with the fungus D. flagrans had a clear effect on reducing autumn pasture contamination. This had a subsequent effect on the over-wintering larvae population that was confirmed by a 20% lower worm burden of tracer lambs kept in early spring on the paddock previously grazed by fungus treated ewes. In spring, pasture contamination was also significantly reduced in the paddock grazed by fungi-treated ewes and their lambs showed a 61% lower worm burden and a better performance than the control lambs. Results herein show that fungal spores fed to sheep at critical times with regard to the epidemiology of parasite infection, can have a significant effect on the infective larvae present on pasture, which could further improve lambs performance. This novel approach to parasite control would be of interest amongst both organic and conventional sheep farmers operating in mountain regions.     

Cool-season annual pastures with clovers to supplement wintering beef cows nursing calves

In December of 3 years, 87 beef cows with nursing calves (594 ± 9.8 kg; calving season, September to November) at side were stratified by body condition score, body weight, cow age, and calf gender and divided randomly into 6 groups assigned to 1 of 6 cool-season annual pastures (0.45 ha/cow) that had been interseeded into a dormant common bermudagrass (Cynodon dactylon [L.] Pers.)/bahiagrass (Paspalum notatum Flugge) sod. Pastures contained 1 of the following 3 seeding mixtures (2 pastures/mixture): 1) wheat (Triticum aestivum L.) and ryegrass (Lolium multiflorum Lam., WRG), 2) wheat and ryegrass plus red clover (Trifolium pretense L., WRR), or 3) wheat and ryegrass plus white (Trifolium repens L.) and crimson clovers (Trifolium incarnatum L., WRW). All groups had ad libitum access to grass hay (12% crude protein; 58% total digestible nutrients). The second week in December, cow estrous cycles were synchronized and artificially inseminated. In late December, a bull was placed with each group for 60-d. Data were analyzed with an analysis of variance using a mixed model containing treatment as the fixed effect and year as the random effect. Body weight and condition scores did not differ (P≥0.27) among cows between February and June. Calf birth weights or average daily gain did not differ (P≥0.17) among treatments; however, calves grazing pastures with clovers did tend (P=0.06) to weigh more than calves grazing grass only. Weaning weight per cow exposed to a bull was greater (P=0.02) for WRR and WRW than WRG. Cows grazing winter-annual pastures containing clovers tended to wean more calf body weight per cow exposed to a bull than cows grazing the grass only pastures.     

Seasonal prevalence of gastrointestinal nematodes of beef calves grazed on irrigated pastures in the lower Sacramento Valley of California

Two worm-free calves were allowed to graze on irrigated pasture with a naturally infected herd for each of 34 one-month periods from November 1979 to August 1982. After each grazing period, the calves were transferred to a cement-floored pen for 3 weeks and then were euthanatized and necropsied. Ostertagia ostertagi and Cooperia oncophora were the most prevalent species of nematodes recovered. Adults and larvae of Ostertagia spp and Cooperia spp were most numerous in winter and spring and least numerous during summer. The proportions of Ostertagia spp that were inhibited as fourth-stage larvae increased in late fall, peaked from March through April, and then decreased to low values during summer. The maximal inhibition in 1980, 1981, and 1982 was 72, 65, and 62%, respectively. The number of larval Cooperia spp was highest in winter months and, except for one grazing period when 55% of the Cooperia spp were larvae, the total numbers represented less than 15% of the nematode population during all grazing periods. Other nematodes encountered were Trichostrongylus axei, Haemonchus spp, O lyrata, and O occidentalis in the abomasum; C surnabata, C punctata, Nematodirus helvetianus, T colubriformis, and Bunostomum phlebotomum in the small intestine; and Oesophagostomum venulosum and Trichuris ovis in the large intestine.     

Cool-season annual pastures with clovers to supplement wintering beef cows nursing calves

ABSTRACT: In December of 3 years, 87 beef cows with nursing calves (594 +/- 9.8 kg; calving season, September to November) at side were stratified by body condition score, body weight, cow age, and calf gender and divided randomly into 6 groups assigned to 1 of 6 cool-season annual pastures (0.45 ha/cow) that had been interseeded into a dormant common bermudagrass (Cynodon dactylon [L.] Pers.)/bahiagrass (Paspalum notatum Flugge) sod. Pastures contained 1 of the following 3 seeding mixtures (2 pastures/mixture): 1) wheat (Triticum aestivum L.) and ryegrass (Lolium multiflorum Lam., WRG), 2) wheat and ryegrass plus red clover (Trifolium pretense L., WRR), or 3) wheat and ryegrass plus white (Trifolium repens L.) and crimson clovers (Trifolium incarnatum L., WRW). All groups had ad libitum access to grass hay (12% crude protein; 58% total digestible nutrients). The second week in December, cow estrous cycles were synchronized and artificially inseminated. In late December, a bull was placed with each group for 60-d. Data were analyzed with an analysis of variance using a mixed model containing treatment as the fixed effect and year as the random effect. Body weight and condition scores did not differ (P > 0.27) among cows between February and June. Calf birth weights or average daily gain did not differ (P [greater than or equal to] 0.17) among treatments; however, calves grazing pastures with clovers did tend (P = 0.06) to weigh more than calves grazing grass only. Weaning weight per cow exposed to a bull was greater (P = 0.02) for WRR and WRW than WRG. Cows grazing winter-annual pastures containing clovers tended to wean more calf body weight per cow exposed to a bull than cows grazing the grass only pastures.     

Serum antibody levels to Taenia saginata in cattle grazed on Scottish pastures

The serum antibody levels to Taenia saginata of three groups of cattle were assessed by an enzyme-linked immunosorbent assay (ELISA). The first group of cattle were from four farms which had a confirmed T saginata cysticercosis outbreak, all of which had cattle classed as infected by ELISA. The second group were from four farms where sewage sludge had been applied to pasture subsequently grazed by the cattle. One of these farms had cattle classed as infected by ELISA. The control cattle, which were all classed as uninfected by ELISA, came from five farms whose pasture had not been treated with sewage sludge. In a wider survey, involving sera from 47 additional farms, the majority could not be distinguished from the control farms in the earlier survey. However, samples from three of the farms had a similar number of positives to two of the known infected farms in the initial survey. Since the ELISA assay may indicate infected herds, farms such as these warrant further investigation.     

Seasonal occurrence of infective nematode larvae in California Sierra foothill pastures grazed by cattle

Worm-free Holstein tracer calves were used to assess the seasonal variation in number and course of development of nematode parasites of cattle on an irrigated pasture located in the California Sierra foothills. The most common genera of nematodes found in the abomasum and small intestine were Ostertagia and Cooperia, respectively. The infective Ostertagia larvae on herbage were most numerous in early spring and lowest in summer months. Arrested development of Ostertagia occurred in mid-to-late spring. The percentage of the population of Ostertagia found to be arrested larvae was constant (73% to 95%) over 4 years, even though the total number of nematodes in the genus was markedly different. Levels of infection with Ostertagia and Cooperia were found to correlate with pasture contamination occurring in the preceding fall and concurrent winter months. In the cecum and large intestine, Oesophagostomum venulosum was found to be the most common nematode. It is suggested that this species may replace Os radiatum as the cattle nodular worm in regions where climate is similar to that of the southwestern coast of North America. Evidence of seasonal hypobiotic development of Oe venulosum was found. Other genera of nematodes observed in tracer calves were Trichostrongylus, Haemonchus, Bunostomum, Trichuris, and Dictyocaulus.     

Decomposition of cattle dung on grazed signalgrass (Brachiaria decumbens Stapf) pastures in monoculture or intercropped with tree legumes

Livestock excreta is one of the major nutrient sources in natural grasslands. Understanding how livestock diet and season affects the decomposition dynamics is critical to nutrient cycling models. We hypothesised that livestock diet and season of the year affect dung decomposition. This study evaluated the decomposition and release of N, P, K, Ca, Mg, and Na from faeces of cattle collected in dry and wet seasons. Treatments were signalgrass (Brachiaria decumbens Stapf) in monoculture or mixed with sabiá (Mimosa caesalpiniifolia Benth.) or gliricidia (Gliricidia sepium (Jacq.) Kunth ex Walp.). Excreta samples were incubated in nylon bags for 0, 2, 4, 8, 16, 32, 64, 128 and 256 d. The single negative exponential mathematical model was adequate (P < 0.0001) to explain the decomposition. The relative rate of dung decomposition (k) was greater for samples that originated from cattle grazed on signalgrass (k = 0.00284 g g^?1 d^?1), followed by sabiá (k = 0.00233 g g^?1 d^?1), and gliricidia (k = 0.00200 g g^?1 d^?1) pastures. The rate of nutrient release showed a time effect for all variables and interaction between time and season for Ca (P = 0.0042) and Mg (P = 0.0013). Faeces collected from cattle grazing/browsing intercropped pastures tended to have lower decomposition rates.     

Toxocara vitulorum in beef calves kept on effluent-irrigated pastures in Zimbabwe

Faeces from 20 calves aged 13 +/- 5 days were examined for Toxocara vitulorum eggs fortnightly for a period of 20 weeks. The age of calves when eggs were first detected varied from 24 to 110 days (mean 41 +/- 20 days). The mean egg count varied from 257 to 19,821 g-1 of faeces with a highest count of 68,400. The patency period of T. vitulorum lasted from 14 to 112 days (mean 65 +/- 30 days). None of the calves showed clinical signs of illness.     

Restricted suckling of tropical dairy cows by their own calf or other cows' calves

The objective of this study was to compare restricted suckling of tropical cows by their own or another cow's calf with artificial rearing of the calves and no suckling. In Exp. 1, cows were mechanically milked twice daily, after which for 15 min they were either suckled by their own calf (Treatment O) or multiple-suckled by other cows' calves (Treatment M) or unsuckled, with the calves reared artificially (Treatment A). Machine milk yield was similar for the three treatments, but in the two suckling treatments the additional milk consumed by the calf increased (P = 0.02) total production (2,682, 2,634, and 2,336 kg/lactation for Treatments O, M, and A, respectively). Machine milk fat concentration was reduced (P = 0.05) by suckling (2.90, 3.07, and 3.20% for Treatments 0, M, and A, respectively), but the milk sampled just before suckling (to represent that taken by the calves) had a high fat concentration (mean 7.9%). Machine milk somatic cell count was also reduced (P = 0.05) by suckling, from 106,000/mL (Treatment A) to 85,000/mL (Treatment M) and 95,000 (Treatment O). Cows suckling their own calf lost more weight and body condition than cows whose calves were reared artificially, with multiple-suckled calves intermediate. Cows suckling their own calf had postpartum interval to first estrus increased (P = 0.01) by 31 d and conception rates to first service of 44% compared to 77% for the other two treatments (P = 0.01). The growth of the suckled calves was compared with that of the artificially reared calves, which were given recommended milk allowances. The artificially reared calves consumed more milk and concentrates, which were available ad libitum to all calves, and gained (P = 0.03) 0.07 kg/d more weight than suckled calves. A second experiment determined that suckling once daily did not reduce reproductive performance compared to artificial rearing. We conclude that suckling cows twice daily increases total milk production but reduces body weight in early lactation. Cows suckling their own calves have reduced reproductive performance compared to those suckling other calves or reared artificially.     

Genotype x environment interactions in Angus, Brahman, and reciprocal-cross cows and their calves grazing common bermudagrass, endophyte-infected tall fescue pastures, or both forages

Reproductive and preweaning data on 190 Angus (A x A), Brahman (B x B), and reciprocal-cross cows (A x B and B x A) and 434 two- and three-breed-cross calves managed on common bermudagrass (BG), endophyte-infected tall fescue (E+), or a combination of both forages (ROT) were used to evaluate the interaction of forage type with individual and maternal heterosis and maternal and grandmaternal breed effects. Cows were born from 1988 to 1991, and calves sired by 13 Polled Hereford bulls were born from 1995 to 1997. Heterosis for calving rate was larger on E+ than on BG or ROT (P < .05), whereas maternal effects were larger on BG than on ROT (P < .10). Maternal heterosis for birth weight was negative on BG (P < .11) but positive on E+ and ROT (P < .10). Grandmaternal effects were evident on BG (P < .10) and E+ (P < .01) but not on ROT. Forage effects were generally substantial for 205-d weight, calf weaning hip height, and calf weaning weight:height ratio; BG was highest, ROT was intermediate, and E+ was lowest. Maternal heterosis for these traits was generally greater on E+ than on BG (P < .10). Grandmaternal effects for 205-d weight, hip height, and weight:height ratio were not important on any forage. Heterosis for weaning weight per cow exposed was substantial on all forages (P < .01) and was significantly greater on E+ (P < .01) than on BG or ROT, but maternal effects were not significant. Thus, we observed more advantage to Brahman-cross cows over purebreds on E+ than on BG. We also observed that moving cows and calves from E+ to BG in the summer will alleviate some, but not all, of the deleterious effects of E+ on calf growth, although it may be more beneficial for reproductive traits in purebred cows.     

Herbage intake and ruminal digestion of dairy cows grazed on perennial ryegrass pasture either in the morning or evening

This study aimed to clarify diurnal fluctuations of herbage intake, ruminal fermentation of herbage carbohydrates and proteins, and digesta particulate weight in the rumen of grazing dairy cows. Six ruminally cannulated, non‐lactating dairy cows were grazed on perennial ryegrass/white clover pasture either in the morning (04.00 to 08.00 hours) or the evening (16.00 to 20.00 hours). Cows grazed in the evening spent more time (P < 0.01) and consumed more herbage (P < 0.01) compared with cows grazed in the morning. Higher (P < 0.05) daily mean concentrations of total volatile fatty acid, propionate and n‐butyrate in rumen fluid were observed for cows grazed in the evening compared with cows grazed in the morning. Although cows grazed in the evening ingested more crude protein compared with cows grazed in the morning, no significant difference in NH₃‐N concentration in rumen fluid was observed between them. The ratio of purine‐derivative concentration to creatinine concentrations was higher (P < 0.01) in the urine of cows grazed in the evening than in cows grazed in the morning. These results clearly indicated that evening grazing was advantageous for dairy cows compared with morning grazing, in terms of ruminal fermentable energy intake and nitrogen utilization efficiency.     

Differences in plasma and abomasal kinetics of albendazole and its metabolites in calves grazed on pasture or fed a grain-based diet

We evaluated the comparative plasma and abomasal fluid disposition kinetics of albendazole (ABZ) and its metabolites in calves either grazing on pasture or fed a grain-based concentrate diet. Six male Holstein calves (weight 180 to 200 kg) were allowed to graze on lush pasture for three weeks before intraruminal administration of ABZ at 10 mg kg-1(pasture group). After a three-week wash-out period, the same animals were housed and fed on a grain-based concentrate diet for three weeks prior to receiving the same ABZ treatment (concentrate group). Jugular blood and abomasal fluid samples were collected over 120 hours post-treatment. Plasma and abomasal fluid samples were analysed by high performance liquid chromatography (HPLC). The digesta transit time was measured using cobalt (Co) as a fluid marker; abomasal fluid and faecal samples were collected and Co concentrations measured by atomic absorption spectrophotometry. Complementary studies of the in vitro dissolution of ABZ particles at different pH values were also conducted. The pH of abomasal fluid collected from animals kept under both feeding conditions was registered. Increased concentrations of ABZ sulphoxide (ABZSO) and sulphone (ABZSO2) in plasma, resulting in significantly higher Cmax and area under the curve (AUC) values for both metabolites, were obtained in calves fed on the concentrate diet compared to those grazing on pasture. Enhanced abomasal fluid levels of ABZ and ABZSO were observed in concentrate-fed calves. The mean retention time of the digestive fluid marker in the gastrointestinal (GI) tract was significantly longer in the animals fed the grain-based diet. The in vitro dissolution of ABZ at a pH value equivalent to that obtained in the abomasum of the concentrate-fed calves (1.75) was significantly greater than that obtained at the pH registered in pasture-fed animals (2.00). The characterisation of the kinetic/metabolic behaviours and the resultant efficacy of antiparasitic drugs in animals reared under different management conditions may be relevant in increasing parasite control in livestock.     

Effects of pre- or postpartum selenium supplementation on selenium status in beef cows and their calves

The effect of Se supplementation before or after calving on Se status in deficient cows and their calves was studied using 72 beef cows in two experiments. In Exp. 1, cows calving in February or March 1997 were supplemented orally for 15 d in late pregnancy with 13.0, 32.5, or 45.5 mg of Se/d as sodium selenite. Glutathione peroxidase (GSH-Px) activities were measured in red blood cells (RBC) or plasma of cows and calves at d 15 and between d 17 and 88 after calving. In Exp. 2, cows calving in January 1997 were supplemented orally with .0, 13.0, or 32.5 mg of Se/d for 15 d postpartum, and calves were injected with 1.38 mg of Se when 2 d old and at an average age of 49 d. The GSH-Px activities were measured in 30-d-old calves and in cows and calves between d 77 and 115 after calving. In both experiments, Se supplementation resulted in adequate Se status for the dams. The increase in RBC GSH-Px activity was faster with 45.5 mg of Se/d, and GSH-Px activities remained high for up to 98 d after the end of supplementation. The improvement in Se status in calves as a result of maternal supplementation was greater in Exp. 1 than in Exp. 2, suggesting that the placental transfer of Se is more efficient than milk transfer. Prepartum oral Se supplementation of deficient beef cows with 13.0 mg of Se/d for 15 d allowed adequate Se status of dams and calves, and 45.5 mg of Se/d resulted in a faster improvement of Se status. Parenteral administration of 1.38 mg of Se to newborn calves did not sustain normal Se status in calves issued from deficient cows.