The effect of weaning age on animal performance in lambs exposed to naturally acquired nematode infections.

The effects of mixed gastrointestinal nematode (GIN) infections on animal growth and post-weaning activity patterns were investigated in grazing intact ram lambs when naturally exposed to two different infection levels and weaned at different ages. Ewes and their twin-born lambs were turned-out to graze in two permanent pasture enclosures naturally contaminated with GIN the previous year. Ewes and lambs in the low parasite exposure group (LP) were drenched before turn-out and at weaning, respectively, with 0.2 mg ivermectin per kg body weight, whereas those in the high parasite exposure group (HP) were left untreated. Two weaning ages were applied, early weaning (EW) (10 weeks) and late weaning (LW) (14 weeks), respectively. The lambs were then allocated to one out of four groups based on parasite exposure level and weaning age (EW-HP, n = 12; LW-HP, n = 11; EW-LP, n = 13; LW-LP, n = 13). Body weight gain (BWG) and faecal egg counts (FEC) were monitored, in all groups, from the day of early weaning and every four weeks, for 10 weeks. In addition, nematode composition was determined using droplet digital PCR. Activity patterns measured as Motion Index (MI; the absolute value of the 3D acceleration) and lying time were monitored continuously from the day of weaning until four weeks post-weaning using IceQube® sensors. Statistical analyses were performed in RStudio, using mixed models with repeated measures. BWG was 11% lower in EW-HP compared with EW-LP (P = 0.0079) and 12% lower compared with LW-HP (P = 0.018), respectively. In contrast, no difference in BWG was observed between LW-HP and LW-LP (P = 0.97). The average EPG was higher in EW-HP compared with EW-LP (P < 0.001), as well as in EW-HP compared with LW-HP (P = 0.021), and LW-HP compared with LW-LP (P = 0.0022). The molecular investigation showed that animals in LW-HP had a higher proportion of Haemonchus contortus compared with EW-HP. MI was 19% lower in EW-HP compared with EW-LP (P = 0.0004). Daily lying time was 15% shorter in EW-HP compared with EW-LP (P = 0.0070). In contrast, no difference in MI (P = 0.13) and lying time (P = 0.99) between LW-HP and LW-LP was observed. The results suggest that a delayed weaning age may reduce the adverse effects of GIN infection on BWG. Contrarily, an earlier weaning age may reduce the risk of H. contortus infection in lambs. Moreover, the results demonstrates a potential use of automated behaviour recordings as a diagnostic tool for the detection of nematode infections in sheep.

Subclinical nematode parasitism affects activity and rumination patterns in first-season grazing cattle.

Sickness behaviour has been suggested as an applicable indicator for monitoring disease. Deviating feeding behaviour and activity can provide information about animals' health and welfare status. Recent advances in sensor technology enable monitoring of such behaviours and could potentially be utilized as an indicator of gastrointestinal nematode (GIN) infections. This study investigated activity and rumination patterns in first-season grazing steers exposed to subclinical infection levels of the GIN Ostertagia ostertagi and Cooperia oncophora. At turnout, animals were allocated to one of four experimental groups and were faced with "high" (H1, n = 15; H2, n = 17) or "low" (L1, n = 17; L2, n = 11) levels of parasite exposure by grazing in similar enclosures contaminated with overwintering third stage (L3) GIN larvae. Animals in H1 and H2 (HP) received a 1:1 mix of approximately 10,000 O. ostertagi and C. oncophora L3 at turnout; whereas the animals in L1 and L2 (LP) were treated monthly with ivermectin. Activity and rumination patterns were monitored by fitting animals with leg- (IceQube) and neck-mounted (Heatime) sensors. BW was recorded every fortnight, whereas faecal and blood samples were examined every four weeks for nematode faecal egg count and serum pepsinogen concentrations (SPCs). There was an interaction effect of exposure level and period (P < 0.0001) on average lying daily time across the entire grazing time. A higher mean daily lying time (P = 0.0037) was found in HP compared with LP during the first 40 days on pasture. There was also interaction effects of treatment and day since turnout on rumination time (P < 0.0001) and rumination change (P = 0.0008). Also mean daily steps (P < 0.0001) and mean daily motion index (P < 0.0001) were markedly higher in HP during days 62-69, coinciding with peaking SPC in HP. Strongyle eggs were observed both in HP and LP from 31 days after turnout. Eggs per gram (EPG) differed between parasite exposure levels (P < 0.0001), with mean EPG remaining low in LP throughout the experiment. Similarly, an increase in SPC was observed (P < 0.0001), but only in HP where it peaked at day 56. In contrast, no difference in BW gain (BWG) (P = 0.78) between HP and LP was observed. In conclusion, this study shows that behavioural measurements monitored with sensors were affected even at low infection levels not affecting BWG. These combined results demonstrate the potential of automated behavioural recordings as a tool for detection of subclinical parasitism.

Nematode parasitism affects lying time and overall activity patterns in lambs following pasture exposure around weaning.

We investigated the effects of gastrointestinal nematode (GIN) challenge on activity in first season grazing lambs naturally exposed to two different levels of multispecies GIN infections. Ewes and their twin-born lambs were turned-out to graze in two permanent pasture enclosures naturally contaminated with GIN the previous year, thereby exposing them to overwintering strongyle larvae. Animals in the low parasite exposure group (LP) were dewormed monthly with 0.2 mg ivermectin (Ivomec® vet, oral suspension) per kg body weight, whereas those in high parasite exposure group (HP) were left untreated. At weaning, lambs were allocated to one out of four groups based on weight and sex (HPE, n = 15; HPR, n = 15; LPE, n = 14; LPR, n = 14), in four nearby non-contaminated ley enclosures of similar size. Activity patterns were monitored from day -7, i.e. 7 days pre-weaning, until day 49, i.e. 49 days post-weaning, by fitting all lambs with IceQube sensors (IceRobotics). Body weight was monitored weekly from day -21, whereas faecal samples were investigated at days -21, 7, 35 and 49 for nematode faecal egg counts (EPG) using McMaster-technology and a validated Droplet Digital PCR protocol to determine nematode composition. All statistical analyses were performed in R studio, using mixed models with repeated measures. In the data analyses, weekly recordings was treated as a period, generating a total of eight periods. Average daily lying time had a significant interaction between parasite exposure and period (P = 0.0013), with animals in HP having a 101 ± 31 min shorter daily lying time compared to LP. Motion Index (MI; absolute value of the 3-D acceleration) had a significant interaction between parasite exposure and period (P = 0.0001) with lambs in group HP having a lower average daily MI compared with LP. Both body weight gain and EPG levels were significantly different (P<0.0001) between HP and LP groups during the course of the study. The molecular investigation showed that animals were predominantly infected with Teladorsagia spp., combined with low proportions of Haemonchus spp. In conclusion, this study shows that lying time and Motion Index of lambs around weaning was affected by moderate nematode infections. This indicates that there is a potential use of automated behaviour recordings as a diagnostic tool for detection of nematode parasites in lambs even at moderate infection levels.

The Effect of Feeding Roughages of Varying Digestibility Prepartum on Energy Status and Metabolic Profiles in Beef Cows around Parturition.

Resource efficient winter-feeding of mature pregnant beef cows requires knowledge of how different roughage-based feeding strategies affect cow intake and energy status. Four diets based on traditional timothy-meadow fescue silage (TM), festulolium silage plus urea (FE), reed canarygrass silage (RC) or barley straw supplemented with urea and rapeseed meal (BR), were fed ad libitum for 16 weeks prepartum to 36 Hereford cows. Postpartum, cows were fed the same diet before release on pasture. Individual data on cow intake, changes in body weight (BW), body condition score (BCS) and plasma metabolites, calf birth and weaning weights were recorded. The TM and FE diets resulted in increased BW and BCS prepartum (p < 0.001), while the RC and BR diets resulted in a catabolic state, as indicated by a loss of BCS, lower insulin levels and higher non-esterified fatty acid levels in cows fed BR (p < 0.001). There were no dietary effects on calf parameters (p > 0.29). Feeding RC or BR prepartum might be a possible alternative to traditional timothy-meadow fescue silage if cows are allowed to regain lost BCS during the grazing period. The influence on cow reproductive- and calf performance should be considered before making this management change.

Beef Production Systems with Steers of Dairy and Dairy × Beef Breeds Based on Forage and Semi-Natural Pastures.

This study compared animal performance and carcass characteristics in steers born to a dairy breed dam and a dairy or beef breed sire allocated to one out of two production systems, both including grazing semi-natural pastures during summer. Spring-born groups comprising 16 purebred dairy (D) steers and 16 dairy × Charolais crossbreeds (C) were allocated to moderately high indoor feed intensity with slaughter at 21 months of age (H), while two corresponding autumn-born groups of 16 D and 16 C animals were allocated to low indoor feed intensity with slaughter at 28 months of age (L). The animals were mainly fed grass-clover silage while housed. The H steers grazed semi-natural pastures for one summer, whereas the L steers grazed semi-natural pastures for two summers. From weaning to slaughter, liveweight gain was 0.94 and 0.77 kg day-1 for H and L steers, respectively (p < 0.0001), with no breed effect on weight gain. However, C carcasses had a higher weight, conformation score, and proportion of high-valued retail cuts than D carcasses (p ≤ 0.004). Moreover, conformation differed more between LC and LD than between HC and HD. From this study on forage and pasture-based beef production, we concluded that breed had no effect on the performance of living animals, but that dairy × beef crossbred steers produced heavier and higher-quality carcasses than pure-bred dairy steers.

Effects of nematode parasitism on activity patterns in first-season grazing cattle.

We investigated the effects of gastrointestinal nematode (GIN) challenge on activity patterns in first season grazing (FSG) steers exposed to two different levels of Ostertagia ostertagi and Cooperia oncophora. At turn-out, experimental animals were allocated to one of two treatment groups grazing in different enclosures each with 32 animals. The first group (High) received 5000 third stage (L3) O. ostertagi (50%) and C. onchophora (50%) larvae; whereas the second group (Low) were dewormed monthly with 0.5 mg ivermectin (Noromectin®, Pour-on) per kg bodyweight. Activity patterns were monitored by fitting some animals in each group (High, n = 10; Low, n = 8) with leg mounted sensors (IceTag® 3D-accelerometers) during three two-week periods. In animals fitted with sensors body weight gain (BWG) was recorded every fortnight, whereas faecal and blood samples were collected every four weeks for nematode faecal egg count (FEC) and serum pepsinogen concentrations (SPC). Differences between the periods in daily (P = 0.046) and diurnal (P = 0.0502) activities were recorded between groups during the course of the study. A significant (P = 0.038) increase in the number of lying bouts was recorded in group High during the second period (days 74-86), which was correlated (r = 0.55, P = 0.018) to an increase in SPC ≈ 85 days after turn-out. BWG was reduced (P = 0.037) in group High compared to group Low, deviating from day 45. Strongyle nematode eggs were observed in both groups 29 days after turn-out, however the mean EPG remained low in group Low throughout the experiment. An increase in SPC was observed (P < 0.0038) in group High with levels peaking on day 58. In conclusion, our data supports that changes in activity patterns monitored with sensors could contribute to the identification of animals challenged with GIN, but also improve our understanding in the potential welfare impairments caused by such infections.

Effects of nematode parasitism on activity patterns in first-season grazing cattle.

We investigated the effects of gastrointestinal nematode (GIN) challenge on activity patterns in first season grazing (FSG) steers exposed to two different levels of Ostertagia ostertagi and Cooperia oncophora. At turn-out, experimental animals were allocated to one of two treatment groups grazing in different enclosures each with 32 animals. The first group (High) received 5000 third stage (L3) O. ostertagi (50%) and C. onchophora (50%) larvae; whereas the second group (Low) were dewormed monthly with 0.5 mg ivermectin (Noromectin®, Pour-on) per kg bodyweight. Activity patterns were monitored by fitting some animals in each group (High, n = 10; Low, n = 8) with leg mounted sensors (IceTag® 3D-accelerometers) during three two-week periods. In animals fitted with sensors body weight gain (BWG) was recorded every fortnight, whereas faecal and blood samples were collected every four weeks for nematode faecal egg count (FEC) and serum pepsinogen concentrations (SPC). Differences between the periods in daily (P = 0.046) and diurnal (P = 0.0502) activities were recorded between groups during the course of the study. A significant (P = 0.038) increase in the number of lying bouts was recorded in group High during the second period (days 74-86), which was correlated (r = 0.55, P = 0.018) to an increase in SPC ≈ 85 days after turn-out. BWG was reduced (P = 0.037) in group High compared to group Low, deviating from day 45. Strongyle nematode eggs were observed in both groups 29 days after turn-out, however the mean EPG remained low in group Low throughout the experiment. An increase in SPC was observed (P < 0.0038) in group High with levels peaking on day 58. In conclusion, our data supports that changes in activity patterns monitored with sensors could contribute to the identification of animals challenged with GIN, but also improve our understanding in the potential welfare impairments caused by such infections.

Intake and feed utilization in two breeds of pregnant beef cows fed forages with high-fiber concentrations.

Hereford and Charolais beef cows (n = 24 per breed) were used to study the effect of breed and to evaluate late-cut reed canarygrass (RC) and whole-crop oats plus urea (WCO) compared with late-cut timothy (TG) with respect to feed intake and digestibility, rumination time, fecal particle size (PS) distribution, N excretion, and ruminal microbial CP production (MCP). The TG and RC were cut at flowering and WCO at hard dough stage of maturity. Cows were group-housed, 6 groups per breed, and fed 3 diets ad libitum in 3 periods. The study was designed as two 3 × 3 Latin squares amalgamated to form a 3 × 6 rectangle for each breed. All data were statistically analyzed on group level. Indigestible NDF (iNDF) and urinary creatinine excretion were used as markers to estimate apparent diet digestibility and daily urine volume, respectively. Fecal PS distribution was determined by dry sieving, and ruminal MCP synthesis was estimated based on urinary output of purine derivatives. The TG diet had a higher apparent digestibility of OM and NDF (P < 0.001) than RC and WCO, which did not differ. The TG diet resulted in the greatest daily DMI, followed by WCO and RC (P < 0.001). Intake of NDF (NDFI, kg/d and % of BW) was greatest for TG, followed by RC and WCO (P < 0.001). Rumination time per kg DMI was longest for RC (P < 0.001), and RC and WCO resulted in longest rumination time per kg NDFI (P < 0.001). The WCO diet resulted in the largest geometric mean fecal PS and proportion of large particles and in the smallest proportion of small particles, whereas the opposite was found for RC, with TG being intermediate (P < 0.001). Intakes in kg per day were higher for Charolais than for Hereford (P = 0.002), but no breed effect was detected when intake was expressed in relation to BW. Charolais ruminated longer per kg NDFI corrected for BW (P = 0.02) and had smaller mean fecal PS (P = 0.049) than Hereford. Total N excretion was highest for RC and lowest for WCO (P < 0.001). The TG diet stimulated MCP production to a greater extent than RC and WCO (P < 0.001). The results indicate that late-cut RC and WCO could be suitable alternatives to late-cut TG for ad libitum feeding of early pregnant beef cows, and that intake was associated with cow BW, but not with breed. The variations in NDF and iNDF concentrations between forage diets were reflected in their effects on intake, rumination, apparent digestibility, and fecal PS.

Weight gain and resistance to gastrointestinal nematode infections in two genetically diverse groups of cattle.

Body weight gain (BWG) and gastrointestinal nematode challenge (GIN) were investigated in two genetically diverse groups of cattle. Thirty-two dairy calves (D=Swedish Red/Holstein) and 31 dairy×beef crosses (C=Swedish Red/Holstein×Charolais) pairwise matched by dam breed and birth dates, were monitored for ≈20 weeks on a pasture grazed by cattle in the previous year. At turn-out, animals (between 6 and 12 months age) from each genotype were either infected with 5000 third stage (L3) Ostertagia ostertagi (50%) and Cooperia oncophora (50%) larvae (H, high-exposure); or treated monthly with 0.5mg ivermectin (Noromectin®, Pour-on) per kg bodyweight to remove worms ingested (L, low-exposure). Animals were weighed every fortnight and individual BWG was calculated. Faecal and blood samples were collected every four weeks throughout the experiment for nematode faecal egg counts (FEC) and larvae cultures and serum pepsinogen concentrations (SPC), respectively. Nematode eggs were observed 29 days post turn-out in both H groups. FEC peaked to around 200 eggs per gram (epg) on days 58 and 85 respectively in both H groups. FEC were also observed in the L groups at the same time, but mean epg remained very low (<20epg) and constituted exclusively of C. oncophora. Although, there was no significant difference in SPC values in animals of the different genotypes, ten animals of CH showed a SPC >3.5 IU tyrosine whereas only six DH animals reached similar pepsinogen levels. The level of infection (H and L) significantly affected BWG in both genotypes. Even though there was no statistically significant genotype (C or D)×treatment (H or L) interaction, there was a larger difference in body weight of H and L in C (37kg) compared to D (17kg) genotypes at the end of the experiment. Our data collectively support the view crossbred (C) animals experience the impact of gastrointestinal parasitism more severely compared to pure dairy (D) first season grazers. The mechanisms that underpin this remains speculative.

Weight gain-based targeted selective treatments (TST) of gastrointestinal nematodes in first-season grazing cattle.

A three-year trial was performed in south-western Sweden to compare animal performance and levels of parasite control in three grazing groups, each with 18-24 first-season grazing (FSG) calves in similar set-stocked pasture enclosures. These groups were subjected to: (1) no parasite control (NT), (2) monthly repeated doramectin (Dectomax(®)) injections (SP), or (3) targeted selective weight gain-based anthelmintic treatments (TST) but only when individual calf performance was inferior to the average of the poorer 50% of those calves in group SP. In each year, weight and parasitological variables were measured at turn-out and then at predetermined intervals for 22-24 weeks during the grazing season. The dewormed calves in group SP had a higher average weight gain at housing (range 0.39-0.61 kg/day) than those in TST (0.36-0.50 kg/day), which in turn always exceeded the NT group (0.23-0.42 kg/day). This indicates that the parasite challenge in the NT group was sufficiently high to result in production loss. However, the average cumulative faecal egg counts (FEC) at housing in NT were in the range 1271-1953 eggs per gram faeces (epg) and in TST 1221-1968 epg. In contrast, parasite eggs were rarely recorded in group SP and then only during the first two years (on average 12 and 38 epg). There were also no significant differences in FEC or serum pepsinogen levels between FSG in groups NT and TST. The animals in SP received 7 doses of doramectin each year, whereas those in TST received an average of 0.5 doses. Thus, the TST approach represented a 92% reduction in anthelmintic use. The average weight gain in animals subjected to TST was always significantly lower than in animals dewormed regularly. In addition, there were no signs of short-term selection for anthelmintic resistance in the group SP animals, despite the fairly intensive use of injectable doramectin.

Antibodies to major pasture borne helminth infections in bulk-tank milk samples from organic and nearby conventional dairy herds in south-central Sweden.

The objective of this randomised pairwise survey was to compare the regional distribution of antibody levels against the three most important helminth infections in organic and conventional dairy herds in Sweden. Bulk-tank milk from 105 organic farms and 105 neighbouring conventional dairy farms with access to pasture in south-central Sweden were collected in September 2008. Samples were also collected from 8 organic and 8 conventional herds located in a much more restricted area, on the same as well as 3 additional occasions during the grazing season, to reveal evidence for seasonal patterns against cattle stomach worm (Ostertagia ostertagi). Antibody levels to the stomach worm (O. ostertagi), liver fluke (Fasciola hepatica) and lungworm (Dictyocaulus viviparus) were then determined by detection of specific antibodies using three different enzyme-linked immunosorbent assays (ELISAs). According to the Svanovir Ostertagia ELISA, the mean optical density ratio (ODR) was significantly higher in the milk from organic compared to conventional herds, i.e. 0.82 (95% CL=0.78-0.86) versus 0.66 (0.61-0.71). However, no significant differences were observed in the samples collected at different time points from the same 16 herds (F(3,39)=1.18, P=0.32). Antibodies to D. viviparus infection were diagnosed with an ELISA based on recombinant major sperm protein (MSP), and seropositivity was found in 21 (18%) of the 113 organic herds and 11 (9%) of the 113 conventional herds. The seroprevalence of D. viviparus was somewhat higher in the organic herds (Chi-square=3.65, P=0.056), but with the positive conventional herds were located in the vicinity of infected organic herds. Of the 16 herds that were sampled on repeated occasions, as many as 10 (63%), were seropositive on at least one sampling occasion. Many of these turned positive towards the end of the grazing season. Only one herd was positive in all 4 samples and 3 were positive only at turn-out. Considering F. hepatica there was no difference in seroprevalence between organic and conventional herds according to the Institute Pourquier ELISA. In general, liver fluke infection was low and it was only diagnosed in 8 (7%) organic and 7 (6%) conventional herds.