Non-supplemented Lambs Research Articles

A new insight about the selection and intake of forage by ewes and lambs in different production systems on pasture

Keeping lambs with their dams and providing concentrate supplement for weaned lambs are two strategies used in lamb meat production systems on pasture that may affect the way that lambs explore, select, and ingest the forage while grazing. Thus, this study aimed to evaluate the selection and intake of forage by ewes and lambs using the continuous bite monitoring method in two pasture-based production systems: non-weaned and non-supplemented lambs (NW); and weaned lambs supplemented with concentrate (WS). Continuous bite monitoring is based on a bite-coding grid that allows the estimation of bite mass, intake rate, selection of plant species and plant parts by grazing animals. Two experiments were carried out during September–November of two subsequent years on a mixed pasture of black oat (Avena strigosa Schreb.) and annual ryegrass (Lolium multiflorum Lam.) established over a perennial Tifton 85 (Cynodon spp.) pasture. On the second year, a third treatment including only the dams of weaned lambs – dry ewes – was also evaluated. In the WS system, lambs were supplemented with concentrate feed at 2% of body weight (BW)/day on a dry matter (DM) basis. Both experiments lasted 46 days, and a continuous stocking management with the forage allowance maintained at 16% BW in DM/day for all treatments. There was a high degree of variability on botanical and morphological composition of forage that was ingested by lambs and ewes, with ranges of 3–14 and 8–11 bite categories for NW lambs and ewes, respectively; 12–15 bite categories for WS lambs, and 8 bite categories for dry ewes. There was similarity between the forage ingested by lambs and ewes in the NW system, except for inflorescences of black oat and annual ryegrass, that were ingested in greater proportions by ewes. WS lambs ingested the most diverse forage diet, which appeared to explore the superior strata of pasture (above 10–15 cm of height) more frequently, and grazed inflorescences and senescent material in higher proportions than NW lambs. Dry ewes showed higher intake of Paspalum spp., Kikuyu grass and other voluntary species and weeds compared to NW ewes. These results suggest that the production system affects the way that lambs explore the pasture and compose their forage diet, with WS lambs ingesting the most diverse diet. The increased intake of inflorescence and, eventually, voluntary species and weeds may be a strategy used by lactating and dry ewes to extend the vegetative stage of high-quality forage species and reduce the population of low-quality plant species on pasture.

Weaning and concentrate supplementation on the characteristics of carcass cuts and longissimus muscle of Suffolk lambs finished on pasture

The aim of this study was to evaluate the influence of weaning and concentrate supplementation on the characteristics of carcass cuts and longissimus muscle of Suffolk lambs finished on a Tifton 85 (Cynodon spp.) pasture. Weaning and concentrate supplementation strategies were evaluated in four finishing systems: i) non-weaned and non-supplemented lambs; ii) non-weaned lambs supplemented with concentrate in creep feeding; iii) weaned and non-supplemented lambs; and iv) weaned lambs supplemented with concentrate. In the systems with weaning, lambs were weaned at 46 ± 6 days of age. In the systems with supplementation, the concentrate was offered daily at 2% of lambs’ body weight. Weaning led to a decrease, whereas supplementation led to an increase in carcass cut weights. Supplemented lambs had lower yields of neck and uncovered ribs, and higher yields of breast + flank and loin. The characteristics of loin eye and fat thickness over the longissimus muscle presented lower values in weaned lambs and higher values in supplemented lambs. Keeping lambs with their dams and offering concentrate supplementation until slaughter are strategies recommended to obtain heavier cuts with increased muscularity and fat content.

The effects of protein supplementation and pasture maintenance on the growth, parasite burden, and economic return of pasture-raised lambs.

The objective of this experiment was to evaluate the impact of protein supplementation and pasture contamination with gastrointestinal nematodes on the mitigation of parasitic infection in grazing lambs. We hypothesized that there would be no difference between protein supplementation and newly sown pasture in evaluating lamb growth and health parameters associated with parasitism. Furthermore, we questioned if there would be an interaction between protein supplementation and pasture type. A total of 192, 60-d-old lambs (28.3 ± 5.1 kg) were randomly assigned to one of four treatments: 1) new pasture without supplementation (NN); 2) new pasture with supplementation (NS); 3) established pasture without supplementation (EN); and 4) established pasture with supplementation (ES) and grazed for 112 d. Lambs were supplemented at a rate of 1% body weight/d. Supplemented lambs had greater body weight (BW) and average daily gain (ADG) when compared with non-supplemented lambs (P < 0.04). Additionally, lambs on newly sown pasture demonstrated greater BW and ADG when compared with lambs grazing on established pasture (P < 0.05). For lamb health, lambs in the EN treatment group had the greatest FAMACHA eye scores and lowest packed cell volume (PCV) over the course of the 112-d grazing period (P < 0.05). Moreover, NS and ES treatment lambs demonstrated similar FAMACHA eye scores when compared with NN treatment lambs; however, NN treatment lambs showed lower PCV when compared with NS and ES treatment lambs (P < 0.05). In evaluating fecal egg counts (FEC), lambs on new pasture or given supplement demonstrated lesser FEC when compared with those lambs on established pasture or not given supplement (P < 0.05). Sixty-four lambs were harvested to evaluate total abomasum nematode counts which demonstrated that Haemonchus contortus represented approximately 80% of total nematodes. Furthermore, based upon gross margin analysis, lambs given a protein rich supplement on pasture had a 9.3 kg increase in lamb BW whereas newly sown pasture had a 1.3 kg increase in lamb BW. A protein rich supplement given to lambs grazing pastures contaminated primarily with H. contortus or placing lambs on newly sown pasture increases lamb BW and improves parasite resiliency. Selection of parasite management strategies may be influenced by cost of production and market opportunities.

How lamb production systems can affect the characteristics and sward structure of Tifton 85 pasture?

Abstract Aimed at understanding how lamb production systems can affect sward structure in tropical grass pastures, the productive, structural and morphological characteristics of Tifton 85 (Cynodon spp.) pasture were evaluated in four systems: non-weaned and non-supplemented lambs (NW); non-weaned lambs receiving concentrate supplementation in creep feeding (CF); early-weaned lambs not supplemented (W); and early-weaned lambs supplemented with concentrate (WS). The trial lasted 105 days and was set out in a randomized block design with four treatments (systems), three replications (paddocks) and five lambs per replication. In the systems with weaning, lambs were weaned at 46 ± 6 days of age and immediately allocated to the paddocks; in the systems with supplementation, lambs received daily a protein–energy concentrate at 2% body weight (BW) on a dry matter (DM) basis. Continuous stocking management was used and the forage allowance was kept at 12% BW in DM/day in all systems. Changes in the structural and morphological characteristics of pasture were more intense up to 63 days of grazing. Sward height and forage mass were higher in WS compared to NW and CF systems, and forage accumulation rate was also higher in WS compared to the other systems. The mass of leaves and stems were higher in the WS system than in NW. Higher heterogeneity of pasture morphological characteristics was observed when weaning was performed. Forage mass was concentrated up to 20 cm sward height in the systems without weaning, with stem mass concentrated in the 0–10 cm stratum and leaf mass highly exposed to grazing in the 10–20 cm stratum. The systems with weaning presented the greatest dispersion of leaves and stems in all sward strata, which increased when the concentrate supplementation was provided to the lambs. Independent of concentrate supplementation to the lambs, the systems without weaning resulted in a better sward structure, with higher leaf/stem ratio for the animals on Tifton 85 pasture. In addition, supplementation of weaned lambs had a deleterious effect on sward structure.

Body and wool growth of lambs grazing on native pastures can be improved with energy and protein supplementation

In a completely randomized experimental design with two replicates, the impact of iso-energetic supplements with different protein levels on body and wool growth was studied in eighty crossbreed (Merino Dohne × Corriedale) castrated male lambs (24.5 ± 4.4 kg of body weight, BW, 4 months of age) in summer (103 days) for three years. Animals were randomly allotted to four treatments (n = 20). All lambs grazed native pastures (NP) and animals in three treatments were daily supplemented (2% BW) with an iso-energetic supplement of different CP levels: control (CON, non supplemented), 12% CP (12CP), 16% CP (16CP) and 20% CP (20CP). Supplemented lambs had higher final BW (36.0, 36.4 and 37.7 kg for 12, 16 and 20CP, respectively) than CON lambs (28.9 kg) (P < 0.05). Among supplemented lambs, the 12CP group had the lowest BW (P < 0.05), without differences between 16CP and 20CP. Supplemented lambs had greater body-weight gain, body condition score, rib eye area and fat thickness than CON lambs (P < 0.05). Wool growth was 40% greater in supplemented lambs compared to CON lambs (P < 0.05), while 20CP animals had the greatest growth. Iso-energetic supplementation with different CP (12, 16 and 20%) levels improved body and wool growth of lambs grazing NP compared to non-supplemented lambs in summer after weaning. Wool growth was greatest when 20% CP supplement was used.

Comportamento ingestivo e desempenho produtivo de cordeiros mantidos em pastagem tropical e recebendo diferentes suplementações

Avaliaram-se os efeitos dos tipos de suplementação sobre o desempenho produtivo e o comportamento ingestivo diurno de cordeiros mestiços Santa Inês mantidos em pastagem de capim-aruana (Panicum maximum cv. Aruana) sobressemeado com aveia branca (Avena sativa L.) e azevém (Lolium multiflorum Lam.), em um delineamento inteiramente ao acaso, com três tratamentos e três repetições. Os cordeiros foram distribuídos aleatoriamente em três sistemas alimentares, com seis animais cada, sendo: PAST - cordeiros mantidos exclusivamente a pasto; SIL - cordeiros mantidos em pastagem recebendo suplementação (1,0% do peso vivo) com silagem de milho; CONC - cordeiros mantidos em pastagem recebendo suplementação (1,0% do peso vivo) com concentrado. Os cordeiros suplementados com concentrado apresentaram ganho de peso médio diário 37,5% superior aos mantidos em pastagem, mas não diferiram da suplementação com silagem de milho. O tempo de pastejo foi superior para os animais não suplementados quando comparados aos animais suplementados. Cordeiros mantidos a pasto e suplementados com silagem de milho ou concentrado ganham mais peso do que os cordeiros não suplementados.

A 'protein bank' of Lotus uliginosus cv. Maku as an alternative to conventional protein supplements for weaned lambs grazing on natural pastures during summer and autumn

The aim of this study was to evaluate the use of restricted grazing of an improved natural pasture as an alternative to conventional protein supplements for weaned lambs grazing natural pastures during summer–autumn. Two natural pastures that differed in dry matter allowances were used as basal diets. Sixty Corriedale lambs, 3 months old, were divided into 10 homogeneous groups. For each natural pasture, one group of lambs was randomly assigned to one of the following treatments (at 10 lambs/ha): continuous grazing (control); control + protein block (150 g/lamb. day); control + soybean meal (100 g/lamb. day); control + supplemental protein obtained from grazing for 3 h/day a natural pasture improved with Lotus uliginosus cv. Maku; or same as previous, except that grazing was allowed 1 in 3 days. Performance results (final bodyweight, average daily gain, and difference between initial and final body scores) were analysed as a completely randomised block design with subsampling. Lambs grazing 3 h/day or 1 in 3 days on improved pasture or supplemented with soybean meal showed better (P &lt; 0.05) performance than non-supplemented lambs. Lambs consuming the protein block performed similarly (P &gt; 0.05) to control lambs. The experiment demonstrated that feeding strategies using controlled grazing of natural pastures improved with lotus Maku or soybean meal supplementation are effective to achieve target growth rates of weaned lambs grazing natural pastures in summer–autumn.

Growth rate of weaned lambs grazing brown midrib sorghum (Sorghum bicolor) supplemented with increasing levels of soybean meal

The aim of the present study was to describe the relationship between increasing levels of soybean meal (SBM) supplementation and the growth rate of weaned lambs grazing brown midrib (BMR) sorghum. Sixty Corriedale weaned lambs (3 months old) were divided into 12 homogeneous groups and allocated into three blocks of BMR sorghum (stocking density: 50 lambs/ha) of four plots each. In each block, lambs were assigned (5 lambs/plot.block) to one of the following treatments: grazing sorghum, grazing sorghum + 115 g SBM/lamb.day, grazing sorghum + 230 g SBM/lamb.day, and grazing sorghum + 345 g SBM/lamb.day. Rotational grazing management was implemented. Lambs were weighed at the beginning of the experiment. Final bodyweight and average daily gain (ADG) were analysed according to a completely randomised block design. The relationship between SBM supplementation level and ADG was tested and a non-linear fit with a prediction model of first-order kinetics was determined. Supplemented lambs had a higher (P &lt; 0.036) final bodyweight and presented higher (P &lt; 0.001) ADG than did non-supplemented lambs (31 kg and 120 g/lamb.day vs 26 kg and 55 g/lamb.day in supplemented and non-supplemented lambs, respectively). An asymptotic ADG value estimated by the model of 143.26 g/lamb.day BMR sorghum appeared to be an adequate summer grazing alternative for weaning lambs. SBM supplementation would improve the performance of animals however the level of supplementation would depend on the productive goal.

Early weaning and concentrate supplementation on the performance and metabolic profile of grazing lambs

This study was designed to investigate the effect of early weaning and concentrate supplementation on performance and metabolic profile of lambs in four production systems on pasture: suckling lambs not supplemented until slaughter; suckling lambs supplemented with concentrate in creep feeding until slaughter; early weaned lambs not supplemented until slaughter; early weaned lambs supplemented with concentrate until slaughter. Performance was assessed by average daily gain (ADG) and body condition score (BCS) measurements. Metabolic profile was delineated by measuring serum albumin, urea, creatinine, cholesterol, glucose and aspartate aminotransferase. Weaning reduced ADG by 92 g/d and the ADG for weaned and suckling lambs were 113 g/d and 205 g/d, respectively. Supplementation increased ADG by 117 g/d and the ADG was 99 g/d for non-supplemented and 216 g/d for supplemented lambs. Body weight and BCS at the end of trial were lower in weaned and non-supplemented animals (20.7 kg and 1.5 points), and higher in those on creep feeding (35.3 kg and 3.3 points). Weaning decreased serum levels of albumin, cholesterol and aspartate aminotransferase. Supplementation increased serum albumin and decreased serum aspartate aminotransferase. Serum urea was not affected by weaning or supplementation and remained high during the trial. Serum creatinine and glucose were lower in weaned and non-supplemented lambs. Early weaning generates unsuitable metabolic profile and low performance and may not be recommended as single strategy to produce lambs on pasture. Concentrate supplementation has similar response to suckling on the performance and metabolic profile of animals, and may be considered an efficient strategy to improve the nutritional status of early weaned lambs.

Comportamento ingestivo de cordeiros em terminação a pasto

The objective of this study was to evaluate intake behavior of lambs in pasture systems: (1) lambs kept with their dams in ryegrass (Lolium multiflorum Lam.) without supplementation; (2) lambs kept with their dams in the same pasture but supplemented in creep feeding; (3) lambs kept with their dams in the same pasture but supplemented in creep grazing with white clover. Three evaluations of intake behavior were performed to check the activities carried out by animals (grazing, rumination, suckling and other activities). Grazing, rumination and other activities times were different (p < 0.05) for non-supplemented lambs. For these lambs, grazing and rumination times were longer than other activities time compared to other systems. Creep feeding reduced grazing time (p < 0.05), probably due to easy access and quality of concentrate. Lambs in creep grazing had reduced (p < 0.05) rumination time. Bite mass in creep grazing was higher (p < 0.05), probably due to easy harvesting of leaves by lambs. It was concluded that the production system affects feeding strategy of lambs and the preference for legumes suggests the use of creep grazing for finishing lambs.

Effect of dietary supplementation with vitamin E on characteristics of vacuum-packed lamb

The effect of dietary vitamin E supplementation on lamb during vacuum-packed storage was studied. Thirty-six weaned male Manchego breed lambs were offered four dietary treatments (20, 270, 520 and 1020 mg vitamin E kg−1 feed). Lambs were fed the vitamin E-supplemented diet from 13 until 26 kg live weight. Pieces of M. longissimus dorsi were stored under vacuum at 2 ± 1 °C in the dark and meat quality was assessed after 5, 14 and 28 days of storage. Dietary supplementation significantly increased the α-tocopherol concentration in the muscle (P < 0.001). Initially, lipid oxidation, meat colour and bacterial load were similar in all groups. In meat of non-supplemented lambs the thiobarbituric acid reactive substance value increased throughout storage, whereas in meat of supplemented lambs it did not increase. Meat pigments and discolouration proportion were significantly affected by storage time (P < 0.001). The bacterial load was low initially, but after 28 days of storage it was close to 7 log10 colony-forming units (cfu) cm−2 and Enterobacteriaceae surpassed the limit of acceptability of 2.5 log10 cfu cm−2, making the lamb unsuitable for human consumption. Meat of supplemented lambs displayed less lipid oxidation than that of their non-supplemented counterparts, while meat colour and bacterial load were not affected by supplementation. Copyright © 2007 Society of Chemical Industry

Performance and grazing behaviour of Churra Tensina sheep stocked under different management systems during lactation on Spanish mountain pastures

Abstract Thirty-six adult ewes rearing single male lambs were randomly allocated to three paddocks (n = 12) grazing permanent Pyrenean pastures in spring (0.5 ha/lot). Treatments were rationed grazing (Rat-Gr) in which lambs remained indoors and ewes grazed during 8 h/day (08:00–16:00 h) and were supplemented 0.5 kg/day of barley meal; continuously grazing ewes rearing non-supplemented lambs (Gr) and continuously grazing ewes rearing supplemented lambs in creep feeders at pasture (Gr + S). Grazing behaviour was registered at weekly intervals by direct observation during the outdoor time in Rat-Gr and from dawn to dusk in Gr and Gr + S. Sward height of Rat-Gr became higher than the rest (P 0.05), while milk yield was higher in Gr + S (P 0.05). Ewes biting rate was greater in Gr (P

Intake and digestion by lambs of dwarf elephant grass ( Pennisetum purpureum Schum. cv. Mott) hay or hay supplemented with urea and different levels of cracked corn grain

This study was carried out to evaluate intake, digestibility, ruminal fermentation, nitrogen (N) retention and ruminal microbial protein synthesis in lambs fed dwarf elephant grass ( Pennisetum purpureum Schum. cv. Mott) hay or hay supplemented with urea and 0, 5, 10 or 15 g/kg of live weight (LW) of cracked corn grain. Ten lambs (mean LW of 28 ± 0.9 kg), housed in metabolic cages, were used in a double 5 × 5 Latin Square experiment. Except fibre intake and digestibility, which was higher, the intake and digestibility of the others feed components, as well as ruminal microbial protein synthesis and N retention were lower in non-supplemented lambs. Corn supplementation increased total dry matter (DM) ( P<0.05), organic matter (OM), non-structural carbohydrate (NSC) and energy intake ( P<0.01) but decreased total neutral detergent fibre (aNDFom) ( P<0.01) intake, as well as OM and aNDFom intake from the hay ( P<0.01). Apparent DM, OM and energy digestibility, as well as OM true digestibility (OMTD) increased ( P<0.01), and aNDFom digestibility decreased linearly ( P<0.01) as corn supplementation increased. Total N intake was not influenced but, apparent and true N digestibility, as well as urinary N excretion decreased ( P<0.01), and ruminal microbial N entering the small intestine increased linearly ( P<0.01) as corn supplementation increased. However, the efficiency of ruminal microbial protein synthesis was similar for all treatments. Mean ruminal pH values and ammonia N concentrations decreased linearly ( P<0.01) with level of corn supplementation. Ammonia N and amino acid, as well as peptide concentrations in ruminal fluid were quadratically related ( P<0.01) with the time after feeding. Corn supplementation had a linear additive effect on total dry matter and digestible energy intake, as well as on N retention, but a linear negative effect on hay intake and on fibre digestibility. However, decreased forage digestibility by animals was probably neither related to lower ruminal pH, which values were always higher than 7.0, nor related to ruminal sugar concentrations, which were similar for all treatments.

Effect of dietary supplementation of vitamin E on characteristics of lamb meat packed under modified atmosphere

The effect of dietary vitamin E supplementation on modified-atmosphere packed lamb meat during storage was studied. Thirty-six weaned male Manchego breed lambs were fed diets supplemented with three different vitamin E concentrations (0, 250, 500 and 1000 mg/kg feed) for an average of 37 days, in the 13–26 kg live weight growth range. Slices of m. longissimus dorsi were packaged under modified atmosphere (70% O 2 and 30% CO 2), stored at 2 ± 1 °C in darkness for 14 and 28 days. Meat quality parameters after both storage periods were assessed. Dietary vitamin E supplementation significantly increased α-tocopherol concentration in muscle. Initially, lipid oxidation (TBARS), meat colour and bacterial load were similar in all groups. Lipid and colour oxidation of meat increased significantly ( P < 0.001) throughout storage. The increase was greater in non-supplemented lambs than in supplemented ones. The bacterial counts after 28 days of storage reached the limit for microbiological shelf life (7 log 10cfu/cm 2). Dietary vitamin E supplementation increased the shelf life of meat packaged under modified atmosphere to 14 days. TBARS, pigment oxidation and bacterial load were inside the acceptable limit. The meat maintained its quality for 28 days of storage only when lambs were fed with the 1000 mg/kg dietary supplement, though the bacterial load was at the limit of acceptability.

The effect of cobalt supplementation on the immune response in vitamin B 12 deficient Texel lambs

The effect of cobalt supplementation on the immune reactivity in vitamin B 12 deficient lambs was measured by comparing the humoral and cell-mediated immune responses against bovine herpes virus type 1 and Mycobacterium paratuberculosis. In addition, faecal egg counts were performed after natural infection with gastrointestinal nematodes. The experiments were performed with registered Texel twin lambs of the same sex. One lamb of each twin received three cobalt pellets divided over the grazing period. The non-supplemented lambs had lower serum vitamin B 12 levels than their supplemented brother or sister. Our results demonstrate significantly lower lymphoblastic responses against Mycobacterium paratuberculosis in non-supplemented lambs compared with supplemented lambs 4 weeks after paratuberculosis vaccination. Vitamin B 12 deficient lambs in this study had significant higher faecal egg counts than their supplemented brother or sister after natural infection with gastrointestinal nematodes. No differences were found in total and differential white blood cell counts, in total protein, albumin, alpha-, beta- and gamma-globulin and in antibody production against bovine herpes virus type 1 and Mycobacterium paratuberculosis.

Improved Recovery of Vitamin E-Treated Lambs that have been Experimentally Infected with Intratracheal Chlamydia

In chlamydia-inoculated lambs, those supplemented with vitamin E had less extensive pneumonia, greater post-infection feed consumption and significantly ( P < 0∙05) heavier weight gains than non-supplemented lambs. Chlamydia were isolated from lungs of 40% of non-supplemented lambs but were not isolated from lungs of supplemented lambs.

Nickel for Ruminants I. Influence of Dietary Nickel on Ruminal Urease Activity

SUMMARY Various metal ions were added to incubating rumen fluid collected from an animal fed a purified diet low in nickel (.06 ppm). After 30 min incubation the rumen fluid was assayed for urease. Ruminal urease activity was low initially and none of the metal ions tested restored urease activity to a normal level, although Ba, Ni and Mn appeared to be slightly stimulatory. Cu, Zn and Cd were found to inhibit urease. In a second study lasting 28 days 5 ppm of supplemental nickel greatly increased ruminal urease activity in lambs fed a corn-based diet containing .32 ppm of nickel and 9.5% crude protein. Ruminal ammonia concentrations were higher in the nickel supplemented Iambs 2 hr postfeeding while serum urea-nitrogen concentrations tended to be slightly lower in this group. The nickel supplemented group also tended to consume more feed and gain faster than the non-supplemented lambs. Alanine transaminase activity and glucose concentrations in serum were not affected by treatment. These studies substantiate earlier work indicating that ruminal urease requires nickel and suggest that the increased urease activity noted after nickel supplementation is not due to activation of the enzyme by nickel.

Some Relationships Between Trichostrongylid Infestation and Cobalt Status in Lambs: II. Trichostrongylus Axei Infestation

Forty-four lambs were reared under worm-free conditions and fed on a diet low in cobalt. When their average age was 11 weeks they were randomly divided into four groups, two of which were fed a cobalt-supplemented diet. Five weeks later the lambs of one supplemented and of one non-supplemented group were given 3,000 Trichostrongylus axei infective larvae until a total of 51,000 had been given. Serum vitamin B 12 levels were indicative of pronounced cobalt deficiency in non-supplemented lambs. Parasitic infestation did not bring about any fall in serum vitamin B I2 in either cobalt-supplemented or cobalt-deficient lambs. Cobalt deficiency caused a highly significant reduction in growth. Infestation in cobalt-deficient lambs, however, caused no significant depression of live-weight at a time when a similar infestation was causing a highly significant decrease in the weight gain of cobalt-supplemented lambs. This result may mean that either a low cobalt status in the host or general malnutrition as a result of cobalt deficiency had the effect of reducing the pathogenicity of T . axei . Infestation, by causing dehydration and concomitant haemoconcentration tended to mask the anaemia due to cobalt deficiency.

Some Relationships Between Trichostrongylid Infestation and Cobalt Status in Lambs : Haemonchus Contortus Infestation

An experiment is described in which 28 lambs reared under worm-free conditions were fed on a low cobalt diet. When the lambs were approximately nine months of age they were randomly divided into four groups, two of which were supplemented with cobalt. Four weeks later the lambs of one supplemented and of one non-supplemented group were given 70,000 H. contortus infective larvae. Though there was no growth response to cobalt administration, liver cobalt levels of non-supplemented lambs were in the range associated with cobalt deficiency. In the early stages of infestation, cobalt-supplemented lambs showed higher egg counts, more severe anaemia and a 43 per cent mortality compared with lambs whose low cobalt diet was not supplemented and in which there was no mortality. It is concluded that a low level of cobalt in the diet of the host is detrimental to H. contortus.