Interferon-gamma, interleukin-4 and interleukin-10 production by T helper cells reveals intact Th1 and regulatory TR1 cell activation and a delay of the Th2 cell response in equine neonates and foals

Cytokines produced by T helper (Th) cells are important in orchestrating the immune response during health and disease. Recent reports indicated that cytokine mRNA expression in foals is often quantitatively lower than that of adult horses suggesting that foal T cells are not fully mature. Here, peripheral blood mononuclear cells from foals and adult horses were stimulated with phorbol 12-myristate 13-acetate and analyzed for intracellular interferon-gamma (IFN-γ), interleukin-4 (IL-4) and IL-10 production, representing the Th1, Th2 and regulatory T_R1 cell phenotypes respectively, by flow cytometry. In agreement with previous reports, all three cytokines were quantitatively reduced in foals compared to adults. However, the balance between Th1 and Th2 cytokines (IFN-γ/IL-4 ratio) showed a clear Th1-biased response in foals by 6 and 12 weeks of life, while similar IFN-γ/IL-10 ratios were found in foals and adult horses. By day 5 after birth, intracellular IFN-γ production by foal CD4⁺ and CD8⁺ T cells resembled that in adults. Overall, IL-4 production was low in foals. IL-4⁺ cells peaked at day 5 of age when IL-4 was mainly produced by IgE⁺ cells. Relative percentages of IL-4⁺ Th2 cells were significantly lower in foals at all time points. The data suggested that equine neonates and young foals have an impaired Th2 response, that the immune response of foals is Th1 biased, that IFN-γ production by Th and cytotoxic T cells is qualitatively similar to adult horses, and regulatory IL-10 production by T cells is developmentally mature in foals during the first three months of life.     

Importance of milk replacer intake and composition in rearing orphan foals

Effects of milk replacer composition and intake on the growth of orphan foals were evaluated. Twenty foals were assigned to four treatments: 1) mare-nursed, 2) commercial foal milk replacer at recommended intakes (standard), 3) commercial foal milk replacer at high intakes (high), and 4) acidified replacer at recommended intakes (acidified). Foals fed milk replacer diets were weaned at 12-24 hours postpartum and fed milk replacer for 50 days. Mare-nursed foals were weaned between 52 and 56 days of age. Foals fed replacer diets gained 12% to 28% less weight than mare-nursed foals up to two weeks of age. However, by four months of age, weights of replacer-fed foals were similar to those of mare-nursed foals and 32 other mare-nursed foals at the farm weaned between three and four months postparium. Foals drank 10 to 12 L/100 kg body weight (BW) in fluid replacer daily over the trial period. During the first week, high intake foals consumed 26% more replacer (p<0.05) than foals fed acidified or standard diets. This higher intake resulted in diarrhea earlier (6-11 days vs 11-22 days) and for a longer time (6.3 days vs 2.5-3.6 days) than in foals fed recommended amounts. Mare-nursed foals developed “foal heat scours” in the second week postpartum. After the first week, foals fed high replacer diet voluntarily consumed the same volume of fluid replacer as foals fed the standard intake. Foals ate less than 1 kg grain mix/100 kg BW daily to one month of age, then increased intake to 1.5-2 kg/ 100 kg BW to weaning. Water intake was 20-40% of daily fluid intake and was correlated (r = 0.85) to dry matter intake. Foals in the high intake group ate less (p<0.05) solid feed and drank less water than foals fed the standard and acidified diets. The foal's stomach capacity appears to limit meal size and thus replacer intake. If recommended feeding intervals are used, replacer intakes by foals are less than 15% BW daily. High volume intakes appeared to prolong diarrhea. Normal growth rates occur when replacer and good-quality feeds are fed concurrently.     

An in vitro biomechanical investigation of an intramedullary nailing technique for repair of third metacarpal and metatarsal fractures in neonates and foals

OBJECTIVE: To evaluate a dorsoproximal extra-articular approach for insertion of 8.25-mm, solid-titanium, intramedullary (IM) interlocking nails into ostectomized foal third metacarpal (MC3) and third metatarsal (MT3) bones; to compare the monotonic mechanical properties of IM nail constructs with paired intact bones; and to determine the effects of age, body weight, fore- or hindlimb, and left or right limb on the mechanical testing variables. ANIMAL OR SAMPLE POPULATION: Twenty bone pairs (10 MC3, 10 MT3) collected from 10 foals of various weights and ages. METHODS: One bone from each pair was randomly selected to be ostectomized and stabilized using an 8.25-mm, solid-titanium IM nail, and four 3.7-mm titanium interlocking screws (construct). Constructs and contralateral intact bone specimens were tested in axial compression and palmaro-/plantarodorsal (PD) 4-point bending. Monotonic mechanical properties were compared between intact specimens and constructs with an ANOVA; significance was set at P <.05. RESULTS: Nail insertion caused bone failure in 6 MC3 and 2 MT3. In general, mean mechanical testing values indicated that intact specimens were significantly stronger and stiffer than constructs for all age and weight ranges when tested in compression and PD 4-point bending (P <.05). Bone strength and stiffness of intact specimens tested in compression and bending tended to increase linearly with age and weight. CONCLUSION: IM interlocking nail fixation of gap-ostectomized MC3 and MT3 with 8.25-mm IM nails and 3.7-mm interlocking screws did not achieve sufficient strength or stiffness to be recommended as the sole means of repair for comminuted MC3 and MT3 fractures in young foals. CLINICAL RELEVANCE: IM interlocking nail fixation of foal cannon bone fractures may be useful to decrease soft-tissue disruption at the fracture site; however, there is a risk of bone failure associated with extra-articular insertion. This method should be combined with other forms of external coaptation for added stability in axial compression and PD bending.     

RADIOGRAPHIC APPEARANCE OF THE EQUINE STIFLE FROM BIRTH TO 6 MONTHS

Lateromedial radiographs of 74 stifles from foals with no stifle swelling or lameness were evaluated to determine the range of normal variation. Foals ranged in age from 0 to 25 weeks with approximately one half of the foals being younger than 11 weeks of age. Nine breeds were represented, with Standardbred and Quarter horse being the most common. Femoral trochlear ridges and patellas were graded on a scale of 1–4 from regular and well defined (1) to very irregular (4). Femoral and tibial condyles were evaluated for irregularity. Twelve stifles were evaluated at necropsy. Irregular to very irregular patellas and trochlear ridges were found in foals up to 20 weeks of age. In foals younger than 11 weeks of age, 77% of bone borders were irregular or very irregular, whereas only 23% of bone borders from foals 11–25 weeks of age had irregular borders. A grade of very irregular was found in 33% of bone borders of foals younger than 11 weeks old, whereas only 1.25% of bone borders of older foals were graded very irregular. Asymmetry in the bone borders between left and right stifle was evident in 36% of the studies, but did not vary by more than one grade. Femoral and tibial condyles were nearly all regular and well defined regardless of age. These findings suggest that obvious irregularities of the femoral or tibial condyles in foals should be interpreted as pathologic. Patellas and trochlear ridges were ranked smooth in 3% of foals younger than 11 weeks of age and in 55% of bone borders of foals 11–25 weeks of age. Obvious irregularities of the patellas or femoral trochlear ridges may be well within normal limits in foals younger than 5 months. Consistent and diagnostic radiographic studies can be obtained safely in most standing foals with little or no sedation.     

Mild exercise early in life produces changes in bone size and strength but not density in proximal phalangeal, third metacarpal and third carpal bones of foals

Exercise or lack of it in early life affects chondro-osseous development. Two groups of horses were used to investigate the effects of age and exercise regimen on bone parameters of diaphyseal, metaphyseal, epiphyseal and cuboidal bones of the distal limb of Thoroughbreds. One group had exercised only spontaneously from an early age at pasture (PASTEX group), while the other group of horses were exposed to a 30% greater workload through additional defined exercise (CONDEX). Longitudinal data from peripheral quantitative computed tomography (pQCT) were obtained from eight scan sites of the left forelimb (proximal phalangeal (P_p; 1 site), third metacarpal (Mc3; six sites) and third carpal (C₃; one site) bones) of 32 Thoroughbred foals scanned five times from ∼3 weeks to 17 months of age. The primary outcome measures were bone mineral content (BMC), bone area (BA), and periosteal circumference (Peri C) in diaphyseal bone, with cortical thickness (CortTh), volumetric bone mineral density (BMD_v) and a bone strength index (SSI) also being analysed.At the P_p site within the model there was a significant effect (P = 0.00–0.025) of conditioning exercise increasing bone parameters, except endosteal circumference (Endo C) and BMD_v. The BMC, BA, and SSI of P_p were significantly greater in the CONDEX than PASTEX groups at 12 and 17 months (P = 0.015–0.042) and CortTh at 17 months (P = 0.033). At the M55 site of Mc3 BMC, BA and SSI (P = 0.02–0.04), and at the M33 site, SSI (P = 0.05) were higher in the CONDEX than PASTEX group. The adaptive responses, consistent with diaphyseal strengthening, were more marked in the diaphysis of P_p than Mc3. In the Mc3, metaphysis, trabecular BMD_v was less in the CONDEX than PASTEX group, associated with greater bone mineral accretion in the outer cortical-sub-cortical bone in the CONDEX group. There were no significant between-group differences in any epiphyseal or cuboidal bone parameter. Although the early imposed exercise regimen was not intensive, it had significant effects on diaphyseal bone strength, through change in size but not bone density.     

A survey of reproductive performance in Thoroughbred mares and morbidity, mortality and athletic potential of their foals

A survey was performed to evaluate the reproductive performance of Thoroughbred mares, estimate risks of dystocia and of morbidity and mortality in foals during the first year post partum and their physical acceptability at age one year. The study population consisted of registered Thoroughbred mares and their foals owned by residents of 4 Western Canadian provinces. Owners were identified using information obtained from the North American Jockey Club, and questionnaires were mailed regarding mares bred in 1988 and their foals born in 1989. Eighty-three per cent of mares were reported to be pregnant at some stage following breeding, and 80% of pregnant mares subsequently gave birth to live foals. Estimates of morbidity and mortality were greater than previously reported, 25% of foals had health problems and 5% died during the first 2 weeks postpartum. Twenty-seven per cent of foals surviving 2 weeks were reportedly affected by some health problem between age 15 days and one year, and 6% died during this period. The case fatality rates of horses with upper respiratory tract infections and diarrhoea were much lower than case fatality rates for infectious diseases occurring less frequently. The rate of death or euthanasia among horses with musculoskeletal problems was relatively high after age 2 weeks. Foals with health problems up to age 2 weeks, or between age 15 days and one year were 5 to 7 times more likely to be classified as physically unacceptable for athletic use. Angular limb deformity was the health problem most commonly reported in foals receiving unacceptable physical assessments, and assessments of longterm athletic potential were apparently not affected by the occurrence of infectious diseases.     

Serially determined plasma alpha-tocopherol concentrations and results of the oral vitamin E absorption test in clinically normal horses and in horses with degenerative myeloencephalopathy

Plasma alpha-tocopherol (vitamin E) values were monitored serially in 9 foals sired by a stallion with equine degenerative myeloencephalopathy (EDM) and in 5 age-matched control foals (sired by a clinically normal stallion) raised in the same environment for the first year of life. Clinical evaluation determined that 8 of the 9 foals sired by the stallion with EDM had neurologic deficits consistent with the disease on one or more occasions during the study period, whereas control foals had normal gait. From 6 weeks to 10 months of age, plasma alpha-tocopherol values in foals with signs of EDM were significantly (P less than 0.001) lower than those in control foals. An oral vitamin E absorption test was performed, and results for 8 of the affected horses and the affected stallion were compared with results for 4 of the monitored control horses and 4 additional control horses. Significant differences were not evident in any of the absorption indices. On the basis of data from this study and supported by reported prophylactic and therapeutic benefits of supplemented vitamin E, low plasma concentration of vitamin E is concluded to be a factor in the development of EDM in the first year of life of hereditarily predisposed foals. It was also concluded that the significantly lower alpha-tocopherol values seen in the foals in this study did not reflect a primary gastrointestinal tract absorption problem.     

Guinea-pig productivity under traditional management

Results of a 12 month study of traditional guinea-pig production in the western highlands of Cameroon are reported. The mean age of guinea-pigs (Cavia porcellus L.) at first parturition, kidding interval and litter size at birth were 126.30±10.40 d, 64.8±1.70 d and 1.63±0.26 kids respectively. The annual reproductive rate was 9.18 kids/breeding doe while the doe post-partum weight was 530 g. Mean body weights at birth, presumed weaning (21 d) and 15 weeks of age were 78.36±3.20, 147.51±8.10 and 418.88±32 g respectively. Type of birth and sex had a significant effect on body weight at all ages. Birth weight dropped significantly from 83.88±2.87 g for singles to 81.57±3.40 g for twins, 74.25±2.39 g for triplets and 73.75±4.12 g for quadruplets. These differences were maintained to maturity (15 weeks). Males were generally heavier than females. Mortality rates were relatively high among kids: 24% at birth, 39% at 3 weeks and 40% at 15 weeks. Productivity indices were 0.827 kg of young weaned per doe per year, 1560 g of young weaned per kg of doe per year and 2.52 kg of young weaned per kg metabolic weight (kg^0.75) of female per year.     

The effect of two different weaning procedures on the growth of pasture-reared Thoroughbred foals in New Zealand

AIM: To identify if there was a significant difference in the average daily liveweight gain (ADG) between Thoroughbred foals weaned using two weaning protocols commonly used in New Zealand.

METHODS: Sixteen Thoroughbred foals were blocked for sex and age, randomly allocated into progressive (187, SD 33 days; three colts, five fillies) or abrupt (182, SD 28 days; four colts, four fillies) weaning groups, and weighed every second day for 2 weeks either side of weaning, then fortnightly from birth to 480 (SD 31) days old. ADG was calculated to examine the short-term (10 days before weaning, 5 and 10 days post weaning) and long-term (0–6 and 6–16 months of age) effect of the two weaning treatments.

RESULTS: ADG was 1.10 (SD 0.091) kg/day before weaning (0–6 months of age) and 0.59 (SD 0.06) kg/day from weaning to 480 (SD 31) days old. At the start of weaning, liveweights of the progressive and abrupt weaning groups were 276.5 (SD 40.3) kg and 257 (SD 15) kg, respectively (p=0.23). For the 5-day period during weaning, irrespective of treatment, there was a significant decrease in ADG of –0.29 (SD 0.49) kg/day and –0.15 (SD 0.30) kg/day for progressive and abrupt weaning, respectively. There was no significant difference in ADG between weaning methods at any measurement period (short or long term) during and after weaning. However, there was large variation between foals in ADG in the 10 days after the weaning process, which may indicate variation in individual foals' responses to being weaned, rather than the weaning treatment.

CONCLUSIONS: Weaning, irrespective of method, was associated with a decrease in ADG in the first week after weaning. The method of weaning had no effect on post-weaning ADG either short term, 10 days after weaning, or long term up to 480 days of age. Practically, it may be more important to consider maturity and liveweight as criteria for weaning foals rather than age alone.     

Evaluation of the influences of exercise, birth date, and osteochondrosis on plasma bone marker concentrations in Hanoverian Warmblood foals

OBJECTIVE: To determine whether plasma concentrations of bone turnover markers in growing Hanoverian foals are influenced by age, housing conditions, or osteochondrosis. ANIMALS: 165 healthy foals and 119 foals with osteochondrosis. PROCEDURES: Foals were allocated according to birth date and housing management into groups of early-born (born before March 31, 2001; n = 154 foals, 88 of which were healthy and 66 of which had osteochondrosis) and late-born (born after March 31, 2001; 130 foals, 77 of which were healthy and 53 of which had osteochondrosis) foals. Plasma osteocalcin and carboxyterminal propeptide of type I collagen concentrations were analyzed as markers of bone formation, and carboxyterminal telopeptide of type I collagen concentration was analyzed as a marker of bone resorption. Foals underwent radiographic evaluation to screen for osteochondrosis. RESULTS: Plasma concentrations of osteocalcin, carboxyterminal propeptide of type I collagen, and carboxyterminal telopeptide of type I collagen decreased with age, but these changes were more distinct in late-born foals than in early-born foals. Neither sex nor predisposition to develop osteochondrosis affected the pattern of bone marker changes in either group. CONCLUSIONS AND CLINICAL RELEVANCE: An age-related decrease in concentrations of bone markers was seen during the first 200 days of life. Changes in bone marker concentrations were similar for foals with osteochondrosis and healthy foals. The correlation between the decrease in bone marker concentration and date of birth indicates that there are differences in skeletal development between early- and late-born foals.     

Oral Infection of Weanling Foals with an Equine Isolate of Lawsonia intracellularis,Agent of Equine Proliferative Enteropathy

Background: Equine proliferative enteropathy (EPE) is an emerging disease of weanling foals. Objectives: Describe clinical, hematologic, biochemical, serologic, molecular, and ultrasonographic findings in foals experimentally infected with Lawsonia intracellularis. Animals: Eight foals. Methods: Recently weaned foals were assigned to either the challenge (n = 3), the sentinel (n = 3), or the control (n = 2) group. Foals were experimentally challenged via intragastric inoculation of 3 × 10¹⁰L. intracellularis organisms grown in culture. Each experimentally infected foal was housed with a sentinel foal in order to assess feco‐oral transmission. All foals were monitored daily for the development of clinical abnormalities and were weighed once weekly for the duration of the study (90 days). Abdominal ultrasound examination was performed weekly. Feces were collected every other day for 60 days, then weekly for an additional 30 days for the quantitative molecular detection of L. intracellularis. Blood was collected weekly for hematologic, biochemical, and serologic analysis. Results: Only challenged foals developed transient clinical signs of EPE consisting of anorexia, lethargy, fever, loose feces, and peripheral edema. Two challenged foals developed transient hypoalbuminemia. Fecal shedding of L. intracellularis was first detected in the challenged foals between days 12 and 18 postinoculation and lasted for 7–21 days. Seroconversion was documented in all challenged foals and in 1 sentinel foal. The remaining sentinel and control foals remained unaffected. Conclusions and Clinical Importance: Clinical EPE of variable severity was induced in all foals infected with L. intracellularis. Furthermore, L. intracellularis can be transmitted via the feco‐oral route to susceptible herdmates.     

Nitrogenous constituents in plasma of foals weaned at three, four or six months of age

A study was conducted to measure the nitrogenous constituents in the blood of foals weaned at 3, 4 or 6 months of age (four foals per weaning age).Jugular blood was sampled from one week prior to weaning until one month post-weaning, and was analyzed for total protein, albumin, creatinine, urea Nitrogen and free amino acid content. Results indicated that the concentrations of most of the constituents in the blood of foals were not altered by the age of weaning, however, free amino acids decreased as age at weaning increased and creatinine was significantly higher in foals weaned at 6 months of age. Plasma creatinine, lysine and methionine levels generally decreased between pre-weaning and one month post-weaning. These data establish baseline values for blood nitrogenous constituents in foals at weaning.     

Recognition of a B‐cell Epitope of the VapA Protein of Rhodococcus equi in Newborn and Experimentally Infected Foals

The aim of this study was to evaluate the usefulness of the previously identified B‐cell epitope TSLNLQKDEPNGRASDTAGQ of the VapA protein of Rhodococcus equi and its association with R. equi pneumonia. A modified peptide designated PN11‐14 corresponding to the epitope was recognized by all sera from experimentally infected foals with virulent R. equi ATCC103⁺ containing the virulence plasmid but not by its plasmid‐cured derivative ATCC103^? strain. Marked levels of VapA‐specific immunoglobulin (Ig)G were detected in all sera from the ATCC103⁺ infected foals at 2 weeks after the infection. One control animal had high titres as determined by the peptide enzyme‐linked immunosorbent assay (ELISA), indicating the ELISA may not absolutely differentiate between foals with R. equi pneumonia and healthy exposed foals in farms where the prevalence of disease is high. However, numbers of animals used were small. Further evaluation of the peptide ELISA with field samples is necessary to determine whether the assay is diagnostically useful. This study showed that levels of passive transfer of maternal IgG antibodies to the epitope in newborn foals could be measured. Interestingly, the maternally derived antibodies were found to significantly (P < 0.05 by Student's t‐test) decline 2 weeks after birth. Seroconversion against naturally occurring VapA expressing R. equi could be detected in some foals at 4 weeks of age. Antibodies to the epitope peaked and were significantly (P < 0.05) greater in foals aged between 6 and 8 weeks. These results indicated that the peptide ELISA could be used to monitor anti‐VapA antibodies in foals, particularly those at the age of 4–6 weeks. It is possible that the ELISA may be of some use as a diagnostic test on farms where R. equi is non‐endemic. Further studies using large number of field samples are needed to verify this assumption.     

The effect of artificial rearing on the growth of foals

Fourteen Quarter Horse foals were used to evaluate the effects of artificial rearing on growth. Seven foals were removed from their dams at 3 d of age and fed a reconstituted 26% crude protein (CP) milk replacer free choice for 1 mo, at which time ad libitum solid feeding began. Controls were weaned from their dams at 2 mo of age and fed a 21% CP concentrate ad libitum until the end of the trial. Variables measured during the 26-wk trial were live body weight, height at the withers and length of body from point of shoulder to point of hip. No significant differences were found between the two groups, except during wk 8 where 2-mo weaned foals were slightly heavier (P less than .10). Average daily gains for artificially reared and 2-mo weaned foals were .95 and .98 kg, respectively.     

Cellular constituents of clinically normal foal bronchoalveolar lavage fluid during postnatal maturation

Bronchoalveolar lavage was performed 5 times, sequentially, on 3 healthy foals when each was between 2 and 63 days of age. Total and differential counts were performed on recovered cells. The lungs of foals less than 19 days of age contained few alveolar macrophages recoverable by bronchoalveolar lavage. This number increased sharply during the first 2 to 3 weeks of life, but remained relatively constant subsequently. Approximately 86% of the alveolar cells in the lungs of foals up to 3 weeks of age were alveolar macrophages. During the first 2 months of life, this number decreased to approximately 71%, whereas the relative percentage of lymphocytes increased from 5% to 20%.     

Effect of prepubertal ovariohysterectomy on bone mineral density and bone mineral content in puppies

In this study, dual energy X-ray absorptiometry (DXA) was performed on the calcaneus (CAL) and accessory carpal bone (ACB) of early-age neutered (n = 11) and sham-operated puppies (n = 10) to investigate changes in bone mineral density (BMD) and bone mineral content (BMC) over time. Prepubertal ovariohysterectomy and sham surgery were performed at 10 weeks, while BMD and BMC were measured at 12, 16, 20 and 24 weeks of age. BMD and BMC of CAL and ACB of ovariohysterectomised puppies were found to be higher. The differences between the groups were statistically unimportant; however, the fourth measurement of the ACB showed a significant (P < 0.05) difference. Sexually intact puppies weighed less than gonadectomised puppies in all measurements. Because of the positive correlations between body weight and bone mineral density, BMD and BMC of early-age neutered puppies were found to be higher. These results suggest that BMD and BMC are not affected by prepubertal ovariohysterectomy until six months of age in mixed-breed puppies.     

Effects of oral supplementation of probiotic strains of Lactobacillus rhamnosus and Enterococcus faecium on diarrhoea events of foals in their first weeks of life

Foal first diarrhoea is one of the most prominent problems in the early life of horses. Probiotics might have the potency to prevent or at least diminish neonatal diarrhoea. We hypothesised that the treatment of foals with probiotic strains of Lactobacillus rhamnosus and Enterococcus faecium starting early after birth and then daily over 2 weeks would prevent or mitigate foal heat diarrhoea. The influence of this probiotic treatment on diarrhoea incidence and growth and health performance of young foals was investigated. Thirty‐four foals were randomly allocated to two groups. From day 1 to 14 of life, the foals received either placebo (PG, n = 16) or the probiotic treatment (TG, n = 18). Clinical examination was performed, and the faeces consistency score (FCS, 1–5; with diarrhoea defined by ≤3) was recorded once per day in weeks 1 and 2 and once weekly in weeks 3–8 of life (WL). The body height was measured at birth and after two and eight WL. Diarrhoea occurred in the 1st WL in 19% and 61% of PG and TG foals respectively. In the 1st WL, diarrhoea lasted 0.3 ± 0.8 and 1.6 ± 1.4 days in PG and TG foals respectively. In the 2nd WL, diarrhoea occurred in 94% and 84% of PG and TG foals, respectively, and lasted for 3.0 ± 1.5 and 3.7 ± 1.6 days respectively. At least two periods of diarrhoea developed in 33% and 65% of PG and TG foals respectively. The TG foals grew slightly slower than the PG foals. The results indicated that the probiotic treatment of neonatal foals as performed in this study was not suitable to reduce diarrhoea within the first two WL, because contrary to the hypothesis, the TG foals suffered more frequently and for longer periods from diarrhoea than the PG foals.