Intraruminal Capsule Research Articles

Development and application of a delayed-release anthelmintic intra-ruminal bolus system for experimental manipulation of nematode worm burdens

In order to quantify the impact of parasites on host population dynamics, experimental manipulations that perturb the parasite-host relationship are needed but, logistically, this is difficult for wild hosts. Here, we describe the use of a delayed-release anthelmintic delivery system that can be administered when the hosts can be captured and its activity delayed until a more appropriate period in the host-parasite cycle. Our model system is Svalbard reindeer infected with a nematode parasite, Marshallagia marshalli, which appears to accumulate during the Arctic winter. To determine the extent to which this occurs and the effect on host fitness, reindeer need to be treated with anthelmintics in late autumn but they can only be caught and handled in April. To solve this problem, we devised an intra-ruminal capsule that releases the anthelmintic from up to 6 months after being administered. The capsule was trialed in cannulated sheep and red deer to determine optimum capsule orifice size and release rates. Capsules were estimated to release placebo for 100-153 days followed by abamectin for 22-34 days. To test the efficacy of treatment in reindeer, capsules were administered in April and retrieved in October. All capsules had fully released the anthelmintic and treated reindeer had significantly lower worm burdens than controls. Thus, success of this system allows repeated treatment over several years to test the effect of winter parasitism on host fitness.

Using n-alkane markers to estimate forage intake of mule deer

Dry matter intake (DMI) of free-ranging mule deer ( Odocoileus hemionus (Rafinesque, 1817)) in the aspen parkland of east-central Alberta was estimated using the double n-alkane ratio and bite count methods. Eleven female mule deer were given an intraruminal capsule containing synthetic n-alkanes and released into 4–8 ha paddocks. Known concentration of even-chained carbon (C32) was released from the capsules and recovered 7–10 days later from freshly voided faeces. Odd carbon chains of adjacent length (C31:C33) were extracted from vegetation samples gathered during behavioural observations of four tame deer. Calculations from the pairings (C31:C32; C33:C32) provided estimates of DMI that ranged from 1.29 to 2.73 kg/day. DMI was highest during autumn, possibly to prepare for increased energy demands for the upcoming winter. No differences were found in seasonal or annual comparisons of bite rates, but bite sizes differed in all comparisons, suggesting bite size was a critical factor affecting consumption rates for mule deer on northern ranges. Maximum bite sizes rose from 49 ± 5 mg/bite in July to 213 ± 58 mg/bite in October. Maximum consumption rates were in October of both years (3.6–4.4 g/min) and occasionally approached theoretical maxima (14.3–15.6 g/min).

Greenhouse gas mitigation opportunities with immediate application to pastoral grazing for ruminants

Many of the greenhouse gas (GHG) mitigating options proposed by researchers have little immediate application to ruminant production from grazed pastures. Many grazing systems have low inputs and ruminants may have infrequent human intervention, which poses a challenge for mitigating GHG. Farmers must be aware of a need for mitigation, but adoption will only occur if the benefits for profitability exceed the costs of implementation and many potential mitigants are either too expensive (organic acids), have variable responses in vivo (ionophors, oils), are impractical under extensive grazing or are unlikely to be available in the near future (vaccines, methanogen inhibitors). Practical GHG reduction will depend on improvements in animal and dietary management, selection of individuals having low emissions/unit feed eaten, and possible release of mitigants through controlled release intra-ruminal capsules.

Control of gastro-intestinal parasitism in sheep with ivermectin delivered via an intraruminal controlled-release capsule

The efficacy of ivermectin delivered by an intraruminal controlled-release capsule against gastro-intestinal nematodes of sheep was evaluated under controlled conditions. In seven Australian studies involving 170 Merino or Merino × Border Leicester sheep, intraruminal capsules developed for 20–40 kg or 40–80 kg sheep, and delivering 0.8 or 1.6 mg of ivermectin/day respectively for 100 days (minimum dose 20 μg/kg/day), were evaluated. Studies were designed to test the therapeutic efficacy against naturally acquired and induced infections treated at the adult and fourth larval stage, and the prophylactic efficacy against naturally acquired and induced infections with third stage infective larvae. The predominant pathogenic nematodes of sheep were represented. Two studies included known benzimidazole- and levamisole-resistant nematode strains. Sheep were necropsied for total nematode counts 21–8.5 days after treatment. The efficacy of the ivermectin controlled-release capsule was generally >99% against all nematode species tested, including those confirmed to be benzimidazole- and levamisole-resistant. High therapeutic activity was demonstrated against existing adult and fourth larval stage nematode infections at the time of treatment, and high prophylactic efficacy was shown against incoming third stage larvae of all species and strains tested.

Effects of sodium monensin on reproductive performance of dairy cattle. I. Effects on conception rates, calving‐to‐conception intervals, calving‐to‐heat and milk production in dairy cows

A total of 1061 lactating dairy cows in six different herds were randomly allocated to treatment and control groups. One herd was lot-fed on total mixed rations; three herds were fed on pasture with significant amounts of supplementary concentrates, and two herds were primarily pasture fed. Treated cows received a slow-release, intraruminal capsule containing 32 g sodium monensin within 7 days of calving. Conception rates at first service, days to first oestrus and calving-to-conception interval did not differ significantly between untreated and monensin-treated cows in the 5 herds, 3 herds and 4 herds, respectively, in which these outcomes were examined. Treatment of lactating cows immediately after calving may not be the optimal method to achieve fertility responses with capsules containing sodium monensin. Monensin treatment significantly increased milk yield in one of the six herds. Milk fat or milk protein production was not significantly affected by treatment.

Monensin controlled‐release intraruminal capsule for control of bloat in pastured dairy cows

Monensin, a polyether ionophore antibiotic, is potentially an important agent for bloat relief in dairy cows grazing temperate legume-based pasture. A series of studies was undertaken to determine the effect of monensin, when delivered continuously in the rumen of lactating dairy cows by means of controlled-release capsules (monensin CRC). Such devices release approximately 300 mg/head/day for 100 d. A short-term pilot study made at Ruakura, New Zealand, tested monensin CRC in cows selected for high susceptibility to bloat and grazing lucerne (Medicago sativa) or red clover (Trifolium pratense). Treatment significantly reduced the incidence of bloat, while milk yield and protein yield were increased. There was no effect on fat yield. Following the pilot study, 6 large-scale field experiments involving a total of 368 lactating dairy cows, were made in Australia and New Zealand to confirm the effectiveness of monensin CRC for bloat control and to measure the effect of such treatment on milk production and composition. A severe bloat problem occurred in 2 experiments, mild bloat occurred in 2 others, while no visual signs of bloat were observed in the remaining 2 experiments. Bloat was significantly (P less than 0.05) reduced by monensin CRC treatment when data was pooled over the 4 experiments in which bloat occurred. Daily milk yield was increased in all experiments from a mean of 17.7 in untreated groups to 18.8 kg/head/day (P less than 0.05) in monensin CRC-treated cows. Protein percentage was not affected by treatment, while there was a decrease from 4.29 to 4.10% fat, although total fat yield was not affected.(ABSTRACT TRUNCATED AT 250 WORDS)

Intraruminal controlled release of cyromazine for the prevention of Lucilia cuprina myiasis in sheep

The efficacy of cyromazine, continuously released from intraruminal capsules at dose rates from 0.5 to 2 mg kg-1 d-1, was evaluated against implants of eggs and first instar larvae of Lucilia cuprina on Merino sheep. Estimates from the non-linear relationship between the success of implants and plasma concentrations showed that 95 per cent protection of sheep could be achieved at a mean release rate of 1.39 mg kg-1 d-1 cyromazine which gave rise to a mean plasma concentration of 0.26 mg litre-1. Present formulations allowed protection for about 90 days in a 40 kg sheep. The 'square wave' type of release profile provided negligible suboptimal dosing thus limiting the potential for selection of resistance. Systemic application of cyromazine provides control of covert and overt strike among sheep and could be used in ecologically based strategies for the control of L. cuprina populations.

Controlled release of anthelmintic drugs: a new concept for prevention of helminthosis in sheep

Anthelmintic effects of oxfendazole continuously released at 0:17, 0.28 and 0.47 mg/kg/day from intraruminal capsules were assessed in groups of sheep artificially infected with Ostertagia circumcincta. Removal of worms was directly related to both release rate and plasma concentrations of drug. At the highest level, worm burdens were removed within seven days of administration and anthelmintic efficiency was 99.9 +/- 0.04, 99.3 +/- 0.5 and 98.9 +/- 0.7 per cent against adult worms, developing fourth stage and early fourth stage larvae respectively. In a field experiment, comparisons were made of the parasitological and animal production differences between groups of weaned lambs which were given no treatment, a single oral dose of 5 mg/kg oxfendazole and capsules releasing either 0.24 or 0.48 mg/kg oxfendazole daily. By four days after administration of capsules worm egg counts were reduced and remained below detectable levels for up to 86 days. Worm counts from 'tracer' and flock sheep showed a reduction in worm numbers, especially for Trichostrongylus spp. Compared with untreated controls, live weight gain and fleece weight of sheep given capsules releasing 0.48 mg/kg oxfendazole daily was increased.

The response of cattle on a sorghum-based feedlot diet to monensin supplied either via intraruminal capsules or in the feed

A feedlot experiment with Hereford steers of initial liveweight of 249 � SE 3.0 kg was done to investigate the production responses to the addition of monensin either in the feed (30 ppm) or in intraruminal controlled-release capsules (CRC). The ration was 90% concentrate (94.3% sorghum, 3% tallow, 2.7% minerals), 10% cotton seed hulls with the following treatments: (A) control, (B) 30 ppm monensin in feed, (C) 50 mg monensin day-1 CRC, (D) 100 mg day-1 CRC, (E) 200 mg day-1 CRC, and (F) 300 mg day-1 CRC. The dry matter intakes and growth rates of the six groups (A to F) were 7.57 and 1.32; 6.56 and 1 .I 3; 7.60 and 1.35; 7.08 and 1.24; 7.39 and 1.35; and 7.05 and 1.23 kg day-1, respectively, with the dry matter intakes for monensin in feed (B) being lower (P < 0.05) than the remaining treatments, and for the same treatment the growth rates were lower (P < 0.05) than treatments A, C and E. The apparent feed conversion ratios (DMI kg-I LW gain) were 5.75, 5.92, 5.78, 5.86, 5.61 and 5.79, respectively, and did not differ (P > 0.05). Generally, the addition of monensin had no effect on carcase characteristics or on liver abscesses. It was concluded that the addition of tallow to the diet may have altered the rumen fermentation pattern sufficiently to prevent further benefit from the addition of monensin.

Beef production from lucerne and subterranean clover pastures. 2. Bloat occurrence and effect of anti-bloat capsules

Over 3 years (1975-77), the occurrence of bloat was recorded in steers grazing two legumedominant pastures, one (LC) containing lucerne (Medicago sativa) and subterranean clover (Trifolium subterraneum) and the other (C) subterranean clover. The effect of intraruminal capsules on both the occurrence of sub-lethal bloat and liveweight gain was assessed in spring 1976 (anti-bloat capsules), and in spring 1977 (anti-bloat and monensin capsules, singly and together). In unprotected steers, bloat occurred only during winter or early spring on both pastures. Over the 3 years, seven steers died from bloat on LC, and three on C. Sub-lethal bloat (rumen distention) was more frequent and severe on LC than on C in 1975 and 1976. However, in 1977 it was more frequent on LC in June-July, but more frequent on C in August-September; there was no difference in severity between pastures. The anti-bloat capsules halved the rumen distention index and improved liveweight gain by an average of 0.2-0.3 kg/head day-1 for short periods in October 1976 and August 1977. The results with monensin capsules were inconclusive. Bloat occurrence is discussed in relation to pasture and environmental conditions, and to beef production on lucerne-clover and clover pastures.

Activity against Ostertagia ostertagi of low doses of oxfendazole continuously released from intraruminal capsules in cattle.

Slow release from intraruminal capsules of 0.48 mg/kg oxfendazole per day for 5.5 days gave percentage efficiencies of 99 +/- 0.6, 86.6 +/- 6.3 and 93.1 +/- 4.5 for the removal of adult worms, developing 4th stages and inhibited larvae of Ostertagia ostertagi respectively. These efficiencies were not significantly different from those obtained from a single oral dose of 2.5 mg/kg. Peak plasma levels of oxfendazole were similar for the 2 types of administration but high levels were maintained longer in cattle given capsules.