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.     

Administration of RRR‐α‐tocopherol to pregnant mares stimulates maternal IgG and IgM production in colostrum and enhances vitamin E and IgM status in foals

This study assessed the effect of a vitamin E supplement given to pregnant mares on immunoglobulins (Ig) levels in foals. In addition, the fatty acid (FA) content and composition of the mares’ milk was assessed. Milk α‐tocopherol concentrations were compared between pregnant Danish Warmblood mares (n = 17) given a daily oral supplement of 2500 international units (IU) RRR‐α‐tocopherol in the last 4 weeks of pregnancy and a group of unsupplemented mares (n = 17) receiving 170–320 IU vitamin E daily originating from the feed. Milk α‐tocopherol was higher in supplemented mares (36.7, 12.4 and 9.8 μmol/l respectively) in relation to control mares (13.1, 6.4 and 5.8 μmol/l on days 1, 2 and 3 respectively; p < 0.001). Milk IgG was higher on days 2 and 3 post‐partum (PP) in supplemented mares (1.03 and 0.73 mg/ml respectively) in relation to control mares (0.79 and 0.56 mg/ml respectively; p < 0.05). Milk IgM was higher on days 2 and 3 post‐partum (PP) in supplemented mares (0.19 and 0.17 mg/ml) in relation to control mares (0.13 and 0.11 mg/ml respectively; p < 0.05). Plasma α‐tocopherol in foals was higher from supplemented mares on days 1, 2 and 3 (5.7, 14.8 and 19.2 μmol/l respectively) in relation to foals from control mares (3.6, 6.1 and 7.6 respectively; p < 0.001). Foal plasma IgM was higher from supplemented mares on day 3 (0.50 mg/ml) in relation to foals from control mares (0.32 mg/ml; p < 0.001). The total FA content in milk was highest on day 1 (21.6 g FA/kg milk) in relation to days 2 and 3 (13.6 and 13.5 g FA/kg milk respectively; p < 0.001). In conclusion, a daily oral supplement of 2500 IU RRR‐α‐tocopherol increased α‐tocopherol content in mare milk and foal plasma, IgG and IgM in mare milk and IgM in foal plasma.     

Determination of the digestible energy intake and apparent absorption of macroelements in pasture-fed lactating Thoroughbred mares

AIM: To measure the nutritive value of pasture in terms of digestible energy (DE) intake (DEI) and dry matter (DM) digestibility, and to determine the apparent absorption of macroelements in lactating Thoroughbred mares grazed on pasture. METHODS: DM intake (DMI) and DEI were determined from daily faecal DM output measured in grazing mares, divided by the DM indigestible fraction (1-digestible DM), measured in a digestibility trial using pasture-fed mares. Eight lactating mares and their foals, that had a mean age of 40 days, were grazed separately on 50x100 m areas of pasture and daily faecal DM outputs were recorded for 8 days. Five mares and their foals were then placed in individual bare 20x20 m corrals containing custom-made feeding stations for 14 days to determine the indigestible DM fraction. DM, gross energy content, crude protein (CP), soluble carbohydrate, acid detergent fibre (ADF), neutral detergent fibre (NDF), lipid, and macroelement composition of the pasture offered and faeces were determined and their digestibility and/or apparent absorption calculated. RESULTS: DM digestibility of the pasture was 0.6 and the DMI and DEI of a grazing 560 kg mare in early lactation nursing a foal growing at 1.34 kg/day was 13.6 (SE 0.8) kg/day and 146.9 (SE 8.4) MJ DE/day, respectively. Apparent absorptions of the macroelements measured were: Ca 0.75, P 0.43, Mg 0.63, Na 0.78, and K 0.72. CONCLUSIONS: Good quality ryegrass-white clover pasture that had a DE content of 10.8 MJ/kg DM, and a macroelement composition (g/kg) of Ca 3.33, P 3.0, Mg 1.67, Na 1.67, and K 24.2, will provide adequate DMI, DEI, and macroelement intake to lactating Thoroughbred mares.     

Efficacy of ivermectin in controlling Strongyloides westeri infections in foals

Twenty-eight foals whose dams were treated IM with ivermectin (200 micrograms/kg of body weight) on the day of parturition were compared with 35 foals whose dams were administered only the vehicle. The effect of ivermectin on the vertical transmission of Strongyloides westeri and foal heat diarrhea was determined by a comparison of results obtained in the 2 groups. Foals from treated mares had significantly fewer S westeri eggs per gram of feces from 17 to 28 days postpartum. There were no differences observed in the frequencies of severity of foal heat diarrhea between the treated and control groups. In another experiment, using the same foals, 32 foals were treated IM with ivermectin (200 micrograms/kg) at 21 days of age and were compared with 31 foals administered only the vehicle. Significantly fewer S westeri eggs were recovered from the ivermectin-treated foals on day 26 to day 32, the completion day of the trial.     

Cryptosporidium parvum infection in a mare and her foal with foal heat diarrhoea

Cryptosporidium infection was molecularly investigated in mares and in their neonatal foals for which the occurrence of foal heat diarrhoea was also assessed. Thirty-seven mare/foal pairs were included in the study. All foals were born in the same stud farm during 2006-2008 breeding seasons. Two faecal samples, one prior to and one after delivery were collected from each mare, whereas three faecal samples were taken from each foal, i.e. at 8, 10 and 12 days of age. All samples (74 from mares and 111 from foals) were divided into two aliquots, one of which was examined for the presence of Cryptosporidium by a commercially available microplate ELISA kit, while the second aliquot of all ELISA-positive samples was molecularly examined. Nine out of 37 examined foals presented foal heat diarrhoea and one of them scored positive for Cryptosporidium, together with its mare. More specifically, four samples belonging to the same mare/foal pair resulted positive for Cryptosporidium upon both ELISA and PCR. The sequence analysis of the COWP gene showed the occurrence of the zoonotic species Cryptosporidium parvum. The possibility that foal heat diarrhoea-like episodes may be due to neonatal cryptosporidiosis and their relevance for the health of horses and of humans handling diarrhoeic neonatal foals and their mares are discussed.     

Changes in faecal bacteria and metabolic parameters in foals during the first six weeks of life

Many foals develop diarrhoea within the first two weeks of life which has been suggested to coincide with postpartum oestrus in their dams. To analyse the pathogenesis of this diarrhoea we have determined faecal bacteria in foals and their dams (n=30 each), and serum IGF-1 and γ-globulins for 6 weeks after birth. In addition, effects of β-carotene supplementation to mares (group 1: 1000 mg/day, n=15, group 2: control, n=15) on diarrhoea in foals were studied. Diarrhoea occurred in 92 and 79% of foals in groups 1 and 2, respectively, but was not correlated with oestrus in mares. Beta-carotene supplementation was without effect on foal diarrhoea. In mares, bacterial flora remained stable. The percentage of foals with cultures positive for E. coli was low at birth but increased within one day, the percentage positive for Enterococcus sp. was low for 10 days and for Streptococcus sp. and Staphylococcus sp. was low for 2-4 weeks. By 4 weeks of age, bacterial flora in foals resembled an adult pattern. Concentration of serum IGF-1 was low at birth (group 1: 149 ± 11, group 2: 166 ± 17ng/ml), increased after day 1 (day 7 group 1: 384 ± 30, group 2: 372 ± 36) but at no time differed between groups. Serum γ-globulin concentration in foals was low before colostrum intake and highest on day 1 (p<0.001 over time). In conclusion, neonatal diarrhoea in foals does not coincide with postpartum oestrus in their dams but with changes in intestinal bacteria and is not influenced by β-carotene supplementation given to mares.     

Raising the orphan foal

Orphan foals are best reared by fostering them onto a brood mare of appropriate size. If no foster mother is available, they can be reared on 2 per cent fat skimmed cow's milk fortified with dextrose at the rate of 20 gm per L. This should be slowly increased from 10 per cent of body weight at 1 day of age to 25 per cent of body weight at 10 days of age. The amount should then be held constant until weaning. Alternatively, foals can be reared on milk replacers. Manufacturers' feeding instructions rarely mimic the milk intake obtained by a foal nursing her dam, and problems have been observed in milk replacer fed foals. It may be better to feed milk replacers at 1- to 2-hour intervals as a 12.5 per cent solution. The volume fed can be slowly increased from 5 per cent of body weight at day 1 to 20 per cent of body weight at day 10. Fresh water, hay, and good-quality creep feed with at least an 18 per cent crude protein should be offered from 2 weeks of age. Foals can be weaned at 8 to 12 weeks of age.     

Serum antibodies in mares and foals to Actinobacillus equuli whole cells, outer membrane proteins, and Aqx toxin

Actinobacillus equuli is carried in the alimentary tract of mares and can cause severe septicemia of neonatal foals. A hemolytic subspecies, A. equuli subsp. haemolyticus, and a non-hemolytic subspecies, A. equuli subsp. equuli, have been identified. Hemolytic strains produce the RTX toxin Aqx. The purpose of this study was to demonstrate sequentially in two sets of mare-foal pairs antibodies to A. equuli whole bacterial cells, outer membrane proteins, and recombinant Aqx and to compare the transfer of antibodies to these antigens between mares and their foals. Two mare/foal sets of sera were evaluated. Cohort A consisted of 18 mare-foal pairs obtained in the spring of 2005. Cohort B consisted of 10 mare-foal pairs obtained in the spring of 2006. For both sets, mare and foal sera were obtained immediately after foaling and prior to nursing (time 0) as well as at 12 and 24h and daily thereafter for 7 days. For Cohort B, sera were also obtained 30 days after birth. At parturition all mares had detectable antibodies to A. equuli whole cells and outer membranes; however, of those mares, two in Cohort A had undetectable antibodies to Aqx and their foals likewise had undetectable anti-Aqx antibodies. Antibodies against whole cells, outer membrane proteins, and Aqx were readily transferred from mares to foals. In most cases, there were significant correlations (p<0.05) between antibodies against whole cells, outer membrane proteins, and Aqx in mares' sera at the time of parturition and foal sera 24 after birth. Antibodies against the three antigen preparations had declined insignificantly (p>0.05) by day 30.     

West Nile Virus Antibody Titers and Total Immunoglobulin G Concentrations in Foals from Mares Vaccinated in Late Gestation

This study was conducted to determine whether prepartum vaccination of mares would enhance passive transfer of West Nile virus (WNV)-specific antibodies and to characterize the pattern of decline for maternally derived WNV antibodies in foals. Seventeen light horse mares were allocated to WNV or control treatments. At 30 days before expected foaling, mares were vaccinated for encephalomyelitis, tetanus, herpesvirus, and influenza. At this time, WNV mares were vaccinated with a killed WNV vaccine. Blood samples were taken from mares 30 days before expected foaling, from mares and foals within 24 hours of foaling (0 days), and from foals at 7, 30, 60, 90, 120, 150, and 180 days of age as well as 30 days after an initial (PV1) and subsequent (PV2) WNV vaccination. Serum was analyzed for titer to WNV and total immunoglobulin G (IgG). Although WNV titer did not change over time in control mares, an increase (P < .05) was observed in WNV titer for WNV mares vaccinated 30 days before expected foaling. Foals of WNV dams had greater (P < .05) WNV titers than foals of control dams. Mean WNV titers of all foals increased from 0 to 7 days and declined through 180 days of age. Total IgG of foals increased from days 0 to 7, declined from days 30 to 120, and increased from days 150 through PV2. These results suggest that vaccination of mares for WNV in late gestation has a beneficial effect on foal WNV titer.     

Supplementation of broodmares with copper, zinc, iron, manganese, cobalt, iodine, and selenium

In experiment 1, 6 pregnant mares received a concentrate that contained a trace mineral premix that provided 14.3 mg Cu, 40 mg Zn, 28 mg Fe, 28 mg Mn, 0.08 mg Co, 0.16 mg I, and 0.16 mg Se/kg concentrate (group A). Seven mares received the same concentrate plus 502 mg Zn and 127 mg Cu once daily (group B). No differences (P > .05) in foal growth data, or Cu, Zn, and Fe concentrations of mare milk, mare serum, or foal serum were observed. In experiment 2, 6 pregnant mares received the same concentrate as group A (group C), and 8 mares received the same concentrate fortified with 4× the trace mineral premix (group D). Group C mares had higher serum Zn concentration at 1 day (P < 0.01) and 56 days (P < 0.04). Group C mares had higher milk Fe concentration at 28 days (P < .01), and group D mares had higher milk Cu concentration at 56 days (P < .01). Group C foals had higher serum Cu concentration at 14 days (P < .03). The results from this study provide no evidence to indicate that supplementing late gestating and lactating mares with higher dietary trace mineral levels than those recommended currently by NRC has any influence on foal growth and development, or on the Cu, Zn, and Fe concentrations of the mare milk, mare serum, or foal serum.     

The ontogeny of serum insulin-like growth factor-I concentration in foals: Effects of dam parity,diet, and age at weaning

The effects of dam parity, age at weaning, and preweaning diet were examined in the ontogeny of serum insulin-like growth factor-I (IGF-I) concentrations in foals. Foals born to 13 primiparous and 19 multiparous draft-cross mares were weighed and bled near birth. About one-half of the foals in each group were weaned early (about 13 wk old); the remaining foals were weaned late (about 16 wk of age). Pooled values for serum IGF-I concentrations between birth and 17 wk of age were higher (P < 0.065) for foals born to multiparous (386 ng/ml) than to primiparous mares (237.5 ng/ml). Colts (378 ng/ml) had higher (P < 0.05) serum IGF-I concentrations than fillies (254.5 ng/ml), regardless of dam parity. Colts (173.5 kg) also tended (P = 0.12) to be heavier than fillies (159.2 kg). Weaning, whether at 13 or 16 wk of age, reduced (P < 0.05) growth rates and serum IGF-I concentrations. Serum IGF-I values recovered to preweaning values within 1–3 wk postweaning concurrent to an improved weight gain. Fifteen 1-d-old foals in a second study were fed milk replacer for 7 wk and were compared with five foals that nursed their mares for 8 wk. During the first 2 wk, replacer-fed foals (0.46 kg/d) did not gain as rapidly (P < 0.03) as mare-nursed foals (1.73 kg/d). The associated serum IGF-I values for replacer foals (139.4 ng/ml) were lower (P < 0.0001) than values for mare-nursed foals (317.4 ng/ml). Despite similarity in gains for both groups thereafter, serum IGF-I concentrations of replacer-fed foals were only 36 and 60% of values obtained for mare-nursed foals at 8 (weaning) and 18 wk of age, respectively. The intrinsic differences between mare-nursed and milk-replacer foals in serum IGF-I concentrations persisted to 1 yr of age despite similarities in dietary management and body weight of the foals. At 1 yr of age, the serum IGF-I concentration of mare-nursed foals (1,203 ng/ml) was 48% higher than that of replacer-fed foals (815 ng/ml). These data indicate that dam parity, sex of foal, and preweaning nutrition affect the ontogeny of serum IGF-I concentration in the foal. The chronic, persistent difference in serum IGF-I values created by the early nutritional management of growing animals has implications in the interpretation of longitudinal serum IGF-I studies in all species.     

Changes in liver copper concentration of thoroughbred foals from birth to 160 days of age and the effect of prenatal copper supplementation of their dams

OBJECTIVES: To monitor the change in liver copper concentration of Thoroughbred foals from birth to 160 days of age and to determine the effects of supplementation by two injections of copper edetate given to dams in late gestation on the liver copper concentration of their foals at birth. PROCEDURE: Ten mares pregnant to the same stallion were randomised into two groups on the basis of age, liver copper concentration and expected foaling date. The treatment group mares were given 100 mg and 250 mg copper edetate intramuscularly during the ninth and tenth months of gestation respectively. Foals had liver biopsies taken weekly in the first month of life, then monthly for four months. Foals were euthanased at 160 days of age; liver samples were taken and the copper concentrations were determined. RESULTS: Two distinct patterns of age dependent decline in liver copper concentration were evident. The mean (+/- SD) liver copper concentration of the foals was high at birth (374 +/- 130 mg/kg DM), and for seven it declined to adult values by 160 days of age (21 +/- 6 mg/kg DM). In three foals the decline was at a slower rate than in the other seven and at 160 days of age the mean concentration was 162 +/- 32 mg/kg DM. Repeated measures analysis showed significant differences between each biopsy (P < 0.01) and between 'normal' and 'accumulator' foals (P < 0.002). Copper injections given to mares in late pregnancy had no effect on the liver copper concentration of foals at birth. CONCLUSIONS: The significance of the two patterns of age dependant decline in liver copper concentration is unknown. Parenteral copper supplementation of the dam in late gestation had no effect on the liver copper concentration of the foal at birth.     

Pharmacokinetics of gentamicin in newborn to 30-day-old foals

Gentamicin sulfate, equivalent to 4 mg of gentamicin base/kg of body weight, was administered IV to 6 Thoroughbred foals on day 1 (12 to 24 hours of age) and at 5, 10, 15, and 30 days after birth. On day 40 after parturition, gentamicin was given to the mares at a dosage similar to that used in foals. Decay of serum gentamicin concentrations was best described by a 2-compartment model. Among foals, the overall elimination rate constant at 30 days of age was significantly (P less than 0.05) greater than at days 1, 10, and 15. There was, however, no difference in the overall elimination rate constant between foals and mares. The volume of distribution (Vd), determined on the basis of total area under the disposition curve, did not change between day 1 and day 30. Mean values of Vd of foals were between 1.5 and 2.5 times higher than the mean Vd of the mares; however, only values from the foals at days 5 and 10 were significantly greater. Both age and interindividual differences were reflected in the total body clearance (ClB) of gentamicin. Total body clearance of gentamicin of foals on day 1 was less than that of foals on days 5, 10, and 30. Additionally, C1B of gentamicin on day 15 was less than that on day 30. There was no significant difference between ClB of foals and mares except for the day-30 group, which had a higher clearance rate than did the adults. Protein binding of gentamicin was less than 30% in all groups, and there were no apparent age-related differences.     

Influence of liver copper status of mare and newborn foal on the development of osteochondrotic lesions

REASON FOR PERFORMING STUDY: To elucidate the highly contentious role of copper in the pathogenesis of osteochondrosis. HYPOTHESIS: There would be no relationship between liver copper concentration of mares and foals and incidence of radiographically detectable osteochondrotic lesions in foals and yearlings was tested. METHODS: Liver copper concentration was assessed in biopsies taken within 4 days after birth from both mares and foals and from the same foals at age 5 months. Biopsies were taken in the standing, sedated animal under ultrasonographic guidance. Radiographs were taken of both hocks (lateromedial, dorsoplantar and dorsomedial-plantarolateral oblique views) and stifles (lateromedial and caudolateral-craniomedial oblique views) at ages 5 and 11 months and scored for the presence and severity of osteochondrotic lesions. RESULTS: Copper concentrations in newborn foals were high with a large variation (351 +/- 201 mg/kg DM). They declined until reaching values comparable to those in mature animals at 5 months (20 +/- 8 mg/kg DM; mares: 19 +/- 20 mg/kg DM). Radiographic osteochondrotic lesions decreased in number and severity from 5 to 11 months. This pattern was more predominant in the stifle than in the hock, as has been described previously. CONCLUSIONS: There was no relationship between foal or mare liver copper concentration and osteochondrosis status at either 5 or 11 months. However, osteochondrotic lesions in foals with low-level copper status at birth decreased significantly less in number and severity than those in foals with high-level copper status at birth. POTENTIAL RELEVANCE: It is concluded that copper is not likely to be an important factor in the aetiopathogenesis of osteochondrosis, but this study indicates that there may be a significant effect of high copper status on the natural process of repair of early lesions.     

Feeding and drinking behavior of mares and foals with free access to pasture and water

The feeding and drinking behavior of 11 mares and 15 foals living on pasture with free access to water was recorded during 2,340 15-min focal samples taken over 2 yr. Lactating mares on pasture spent about 70% of the day feeding. Foals began feeding on their first day of life. As they grew older, they spent progressively more time feeding, but still spent only 47 +/- 6% of the time feeding by 21 wk of age. Foals fed primarily during the early morning and evening. While grass formed the major proportion of the diet of both foals and mares, they also ate clay, humus, feces, bark, leaves and twigs. Almost all feeding by foals was done while their mothers were feeding. Movement to water sources was frequently, but not invariably, carried out by an entire herd. Frequency (P = .005) but not duration (P greater than .05) of drinking bouts by mares increased as the temperature increased. Frequency was greatest at 30 to 35 C, at which temperature mares drank once every 1.8 h. Frequency of drinking varied with the time of day (P less than .01), being rarest during the early morning (0500 to 0900 h eastern daylight time) and most frequent during the afternoon (1300 to 1700 h). Drinking by foals was very rare. The youngest age at which a foal was observed to drink was 3 wk, and 8 of 15 foals were never observed to drink before weaning.     

Dietary yeast culture supplementation of mares during late gestation and early lactation: Effects on milk production, milk composition, weight gain and linear growth of nursing foals

This study examined the effects of dietary supplementation of pregnant and lactating mares with concentrated dried live yeast culture on the nutrient content and rate of production of milk during early lactation and on the growth of their nursing foals. Pregnant mares were fed the same diets, with or without 20 g/day of yeast culture, from 4 weeks before foaling through the eighth week of lactation. Milk production at the onset of lactation, as measured by the weigh-suckle-weigh technique, was significantly stimulated by yeast culture supplementation, although the effect was only temporary. However, the nutrient composition of mares milk was altered by continued yeast culture supplementation through at least the eighth week of lactation. Gross energy (kcal/100 g milk), sugar, fat, protein and total amino acid contents (g/100 g milk) were significantly increased. The concentrations of a number of individual amino acids tended to be greater in the milk of supplemented mares, but most of these individual differences were not statistically significant. The intakes of energy (Mcal/day), sugars, fat, protein, total amino acids, leucine, lysine, serine and valine (g/day) were significantly greater by the foals nursing supplemented mares through 8 weeks. The foals nursing supplemented mares exhibited significantly greater rates of gain by the fourth week of life, and faster growth at the withers after 6 weeks. The efficiency of converting mare feed to neonatal body mass was 24% greater in the foals of supplemented mares, These data indicate that supplementing mares with dietary yeast culture during early lactation resulted in more efficient and rapid growth of their nurslings.     

Matua bromegrass hay for mares in gestation and lactation

Matua bromegrass hay (Bromus willdenowii Kunth) is a high quality forage, but its value for mares during gestation and lactation is not well known. Intake, rate of passage, performance, and reproduction by gestating and lactating Quarter Horse mares fed the hay was investigated. In this experiment, 12, 2- to 12-yr-old gravid mares (mean BW = 553 kg, SD = 36) were fed Matua hay (CP = 11.5%) or alfalfa hay (Medicago sativa L.) (CP = 15.4%) for variable days prepartum (mean 59.9 d; SD = 23.5) and for 70 d postpartum. Matua and alfalfa hay were fed as the roughage portion of the diet with a grain supplement. Mares, blocked by age, expected date of foaling, and BW, were assigned randomly within blocks to treatments (six mares per treatment). Forage type did not affect intake, gestation length, birth weight, number of foals, foal weight gain, day of first postpartum ovulation, cycles per conception, or pregnancy rate at 70 d. On d 1, milk from mares fed alfalfa hay contained less (P < 0.03) CP than milk from mares fed Matua hay. Milk CP decreased (P < 0.01) in all mares over time. In a separate experiment, voluntary intake and rate of passage of Matua (CP = 15.5%), alfalfa (CP = 24.9%), and Timothy (Phleum pratense L.) (CP = 4.1%) hays were determined in nine 2-yr-old pregnant mares (mean BW = 447 kg; SD = 21). Diets were 100% forage. Timothy hay did not meet CP requirements for mares. Voluntary intake of alfalfa hay was higher (P < 0.01) than Matua hay. Intake of Timothy hay was lower (P < 0.01) than the mean of alfalfa and Matua hay. Rate of passage offorage was measured by passage of Cr-mordanted fiber. Passage rate and retention time did not differ between Matua and alfalfa hay; however, the retention times of Matua and alfalfa hays were shorter (P < 0.01) than for Timothy hay. Our results indicate that Matua hay is a forage that can be used safely for mares during gestation and early lactation and for their young foals.     

Epidemiological studies of equine herpesvirus 1 (EHV-1) in Thoroughbred foals: a review of studies conducted in the Hunter Valley of New South Wales between 1995 and 1997.

Sero-epidemiological studies conducted between 1995 and 1997 on two large Thoroughbred stud farms in the Hunter Valley of NSW showed clear evidence of EHV-1 infection in foals as young as 30 days of age. Similarly, serological evidence suggested that these foals were infected with EHV-1 from their dams or from other lactating mares in the group, with subsequent foal to foal spread of infection prior to weaning. These studies also provided evidence of EHV-1 infection of foals at and subsequent to weaning, with foal to foal spread of EHV-1 amongst the weanlings. These data indicated that the mare and foal population was a reservoir of EHV-1, from which new cases of infection propagated through the foal population both before and after weaning. The results of these studies support the long standing management practices of separating pregnant mares from other groups of horses to reduce the incidence of EHV-1 abortion. Also, these results have important implications for currently recommended vaccination regimens, as the efficacy of vaccination in already latently infected horses is unknown.     

不同品种泌乳母马不同泌乳月产奶量及乳成分的比较

[目的]研究伊犁马和哈萨克马泌乳母马在不同泌乳月产奶量及乳成分的差异,为开发利用伊犁马和哈萨克马乳用特性提供参考。[方法]随机选择年龄和胎次相近、产驹时间接近、健康的伊犁母马和哈萨克母马各12匹,在日粮营养水平和饲养管理水平相同的条件下,记录2个品种母马在泌乳30、60、90 d的产奶量;采集乳样,测定2个品种母马不同泌乳时间的乳中体细胞数、乳脂率、乳蛋白率、乳糖率和总固形物含量。[结果]泌乳30 d时,哈萨克马的产奶量高于伊犁马（P>0.05）,乳脂率极显著（P<0.01）高于伊犁马,乳中体细胞数显著（P<0.05）高于伊犁马,其他乳成分指标高于伊犁马（P>0.05）。泌乳60 d时,伊犁马的产奶量和乳糖率极显著（P<0.01）高于哈萨克马,乳脂率和乳蛋白率高于哈萨克马（P>0.05）,乳中体细胞数和总固形物含量低于哈萨克马（P>0.05）。泌乳90 d时,伊犁马的产奶量显著（P<0.05）高于哈萨克马,乳糖率、总固形物含量极显著（P<0.01）高于哈萨克马,乳脂率和乳体细胞数极显著（P<0.01）低于哈萨克马,乳蛋白率高于哈萨克马（P>0.05）。[结论]泌乳初期（30 d）,哈萨克马的产奶量和乳营养成分含量高于伊犁马;泌乳中期（60、90 d）,伊犁马的泌乳性能整体优于哈萨克马。在观察期内,哈萨克马的乳体细胞数大于伊犁马。     

Retinol, β-carotene and β-tocopherol concentrations in mare and foal plasma and in colostrum

Fat-soluble vitamins transfer poorly across the diffuse epitheliochorial placenta of the mare, so the neonatal foal is dependent on its supply via colostrum. Concentrations of retinol (RT), β-carotene (BC), and β-tocopherol (AT) were assayed in samples of plasma, colostrum and milk from nine mares of mixed light breeding and their foals at parturition and days 1, 2, and 4 postpartum. Samples were analyzed simultaneously for RT, BC, and AT using a new, less time-consuming reverse phase high-pressure liquid chromatography (HPLC) method. Feeds were analyzed, and mean daily intakes calculated. Mare plasma RT increased from day 1 to day 4 (P = .033), and plasma AT declined linearly from day 0 to day 4 (P = .006). Colostrum concentrations of all vitamins increased from parturition to day 1, and then declined rapidly over the 4 days. Foal plasma BC increased from parturition to day 4 (P = .080), and plasma AT increased from parturition to day 2 (P < .001), and 4 (P = .060). These observations suggest that three times the current recommendation of vitamin A is sufficient for pregnant mares, in keeping with previous studies of growth, pregnancy, and lactation. In contrast, the linear decrease in mare plasma AT suggests that 1.2 times the current recommendation of vitamin E may be less than optimal for pregnant mares.

Introduction

The diffuse epitheliochorial placenta of the mare does not allow fat-soluble vitamins to cross with ease to the fetus,[1] so their status in the neonatal foal is dependent on colostrum. This first milk contains these vitamins, which are necessary for many functions.Vitamin A is required for vision, reproduction, growth, development, and maintenance of epithelial cells, and osteoclast activity in bone formation. In addition, vitamin A deficiencies reduce resistance to disease, can cause neurological degeneration, and congenital defects.[2] Vitamin E, an antioxidant, prevents lipid peroxidation and cell membrane damage. Its deficiency in horses has been associated with a form of muscular dystrophy and impaired immune function. [3]Studies on the mare and foal have described blood concentrations of one or two of these vitamins,[4, 5 and 6] but only one involved all three. [7] In that study, vitamin concentrations were assayed in mare blood and milk, but only once in foal blood at parturition, so data during the periparturant period is incomplete.The objectives of this enumerative study were to determine concentrations of RT, BC, AT in plasma and colostrum, to evaluate colostral transfer of these vitamins, to assess the adequacy of vitamin intakes of mares, and to develop a time-saving single-run HPLC method.

Materials and methods

Animals

Nine healthy aged multiparous mares of mixed light breeding (13.6 ± 1.5 years, 592 ± 20 kg body mass) and their foals were sampled. The institutional animal care and use committee approved the protocol. Mares were kept on meager late-winter mixed grass pasture, with free access to round bale orchard and fescue grass hay, water, and trace mineral/vitamin salt. They were fed 2 kg of concentrate twice daily at 7:00 and 3:00 . The diet met or exceeded current recommendations for pregnant mares at 11 months gestation for energy.[8] Samples of hay and concentrate were submitted for partial proximate analysis to the Virginia Tech Forage Testing Laboratory where standard AOAC [9] methods are used ( Table 1). Samples of feeds were also taken for analysis of RT, BC, and AT ( Table 2).