Marsupials give birth to immunologically naïve young after a relatively short gestation period compared to eutherians. Consequently, the joey significantly relies on maternal protection, which is the focus of the present review. The milk and the pouch environment are essential contributors to maternal protection for the healthy development of joeys. In this review, we discuss bioactive components found in the marsupial pouch and milk that form cornerstones of maternal protection. These bioactive components include immune cells, immunoglobulins, the s100 family of calcium-binding proteins, lysozymes, whey proteins, antimicrobial peptides and other immune proteins. Furthermore, we investigated the possibility of the presence of plurifunctional components in milk and pouches that are potentially bioactive. These compounds include caseins, vitamins and minerals, oligosaccharides, lipids, and microRNAs. Where applicable, this review addresses variability in bioactive components during different phases of lactation, designed to fulfil the immunological needs of the growing pouch young. Yet there are numerous additional research opportunities to pursue, including uncovering novel bioactive components, investigating their mode of action, dynamics, stability, and ability to penetrate the gut epithelium ensuring systemic actions.

Colostrum-derived passive immunity is central to the health, performance and welfare of neonatal beef-suckler calves, and economics of beef-farming enterprises. Compared to dairy calves, mainly Holstein-Friesian, there is much less research carried out on passive immunity and associated factors in beef calves. Thus, this review aimed to summarise and interpret published information and highlight areas requiring further research. The transfer of immunoglobulin G1 (IgG1) from blood to mammary secretions is greater for beef × dairy cows compared to most beef breed types. Considerable between-animal variance is evident in first-milking colostrum yield and immunoglobulin concentration of beef-suckler cow breed types. First-milking colostrum immunoglobulin concentrations are similar for within-quarter fractions and for the front and rear quarters of the udder. First-milking colostrum yield is higher for beef × dairy cows than beef × beef and purebred beef breeds, and higher for multiparous than primiparous cows, but generally colostrum immunoglobulin concentration is relatively similar for each of the respective categories. Consequently, colostrum immunoglobulin mass (volume × concentration) production in beef cows seems to be primarily limited by colostrum volume. The effect of maternal nutrition during late gestation on colostrum yield is not well documented; however, most studies provide evidence that colostrum immunoglobulin concentration is not adversely affected by under-nutrition. Factors that impinge upon the duration between birth and first suckling, including dam parity, udder and teat anatomy and especially dystocia, negatively impact on calf passive immunity. Colostrum immunoglobulin mass ingested relative to birth weight post-parturition is the most important variable determining calf passive immunity. Research indicates that feeding the beef calf a colostrum volume equivalent to 5% of birth weight shortly after parturition, with subsequent suckling of the dam (or a second feed) 6 to 8 h later, ensures adequate passive immunity, equivalent to a well-managed suckling situation. Within beef-suckler cow genotypes, calf passive immunity is similar for many common beef breeds, but is generally higher for calves from beef × dairy cows. Compared to older cows, calves from younger cows, especially primiparous animals, have lower serum immunoglobulin concentrations. Most studies have shown no adverse impact of maternal dietary restriction on calf passive immunity. The prevalence of failure of passive transfer (FPT) in beef calves varies considerably across studies depending on the test used, and what cut-off value is assumed or how it is classified. The accuracy and precision of methodologies used to determine immunoglobulin concentrations is concerning; caution is required in interpreting laboratory results regarding defining colostrum ‘quality’ and calf passive immune ‘status’. Further research is warranted on colostrum-related factors limiting passive immunity of beef calves, and on the validation of laboratory test cut-off points for determining FPT, based on their relationships with key health and performance measures.

Previous studies have shown that a 10 % cocoa (C10) diet, containing polyphenols and fibre among others, modifies intestinal and systemic Ig production. The present study aimed at evaluating the impact of C10 on IgA and IgM production in the intestinal and extra-intestinal mucosal compartments, establishing the involvement of cocoa fibre (CF) in such effects. Mechanisms by which C10 intake may affect IgA synthesis in the salivary glands were also studied. To this effect, rats were fed either a standard diet, a diet containing C10, CF or inulin. Intestinal (the gut wash (GW), Peyer’s patches (PP) and mesenteric lymph nodes (MLN)) and extra-intestinal (salivary glands) mucosal tissues and blood samples were collected for IgA and IgM quantification. The gene expressions of IgA production- and homing-related molecules were studied in the salivary glands. The C10 diet decreased intestinal IgA and IgM production. Although the CF diet decreased the GW IgA concentration, it increased PP, MLN and serum IgA concentrations. Both the C10 and the CF diets produced a down-regulatory effect on IgA secretion in the extra-intestinal tissues. The C10 diet interacted with the mechanisms involved in IgA synthesis, whereas the CF showed particular effects on the homing and transcytosis of IgA across the salivary glands. Overall, CF was able to up-regulate IgA production in the intestinal-inductor compartments, whereas it down-regulated its production at the mucosal-effector ones. Further studies must be directed to ascertain the mechanisms involved in the effect of particular cocoa components on gut-associated lymphoid tissue.

A diet containing 10 % cocoa, a rich source of polyphenols and fibre, is able to modify intestinal immune status as well as microbiota composition. The present study was aimed at investigating whether cocoa flavonoid content is uniquely responsible for these modulatory effects of cocoa, and to establish whether these effects depend on the rat strain. To this end, 3-week-old Wistar and Brown Norway rats were fed, for 4 weeks, either a standard diet or the following three isoenergetic diets containing increasing proportions of cocoa flavonoids from different sources: one with 0·2 % polyphenols (from conventional defatted cocoa), and two others with 0·4 and 0·8 % polyphenols (from non-fermented cocoa, very rich in polyphenols). Serum Ig concentrations, faecal IgA levels, microbiota composition and IgA-coating bacterial proportion were evaluated at the beginning and at the end of the study. After the nutritional intervention, the composition of lymphocytes in Peyer's patches and mesenteric lymph nodes was evaluated. In some respects, the Wistar strain was more sensitive to the impact of the cocoa diets than the Brown Norway strain. After 4 weeks of dietary intervention, similar modulatory effects of the diets containing 0·2 and 0·8 % polyphenols on mucosal IgA levels and microbiota composition were found, although the 0·2 % diet, with a higher proportion of theobromine and fibre, had more impact, suggesting that polyphenols are not the only components involved in such effects.

Piglet survival is a major problem, especially during the first 3 days after birth. Piglets are born deficient of energy, but at the same time they have a very high energy requirement because of high physical activity, high need for thermoregulation (because of their lean body with low insulation) and high heat production in muscle tissues. To be able to survive, newborn piglets may rely upon three different sources of energy, namely, glycogen, colostrum and transient milk, which orchestrate to cover their energy requirements. Piglets are born with limited amounts of energy in glycogen depots in the liver and muscle tissues and these depots are sufficient for normal activity for ∼16 h. Intake and oxidation of fat and lactose from colostrum must supply sufficient amount of energy to cover at least another 18 h until transient milk becomes available in the sow udder ∼34 h after the first piglet is born. Selection for large litters during the last two decades has challenged piglets even further during the critical neonatal phase because the selection programs indirectly decreased birth weight of piglets and because increased litter size has increased the competition between littermates. Different attempts have been made to increase the short-term survival of piglets, that is, survival until day 3 of lactation, by focusing on improving transfer of vital maternal energy to the offspring, either in utero or via mammary secretions. Thus, the present review addresses how sow nutrition in late gestation may favor survival of newborn piglets by increasing glycogen depots, improving colostrum yield or colostrum composition, or by increasing production of transient milk.

Transfer of sufficient immunoglobulin G (IgG) to the neonatal calf via colostrum is vital to provide the calf with immunological protection and resistance against disease. The objective of the present study was to determine the factors associated with both colostral IgG concentration and colostral weight in Irish dairy cows. Fresh colostrum samples were collected from 704 dairy cows of varying breed and parity from four Irish research farms between January and December 2011; colostral weight was recorded and the IgG concentration was determined using an ELISA method. The mean IgG concentration in the colostrum was 112 g/l (s.d. = 51 g/l) and ranged from 13 to 256 g/l. In total, 96% of the samples in this study contained >50 g/l IgG, which is considered to be indicative of high-quality colostrum. Mean colostral weight was 6.7 kg (s.d. = 3.6 kg) with a range of 0.1 to 24 kg. Factors associated with both colostral IgG concentration and colostral weight were determined using a fixed effects multiple regression model. Parity, time interval from calving to next milking, month of calving, colostral weight and herd were all independently associated with IgG concentration. IgG concentration decreased (P < 0.01) by 1.7 (s.e. = 0.6) g/l per kg increase in the colostral weight. Older parity cows, cows that had a shorter time interval from calving to milking, and cows that calved earlier in spring or in the autumn produced colostrum with higher IgG concentration. Parity (P < 0.001), time interval from calving to milking (P < 0.01), weight of the calf at birth (P < 0.05), colostral IgG concentration (P < 0.01) and herd were all independently associated with colostral weight at the first milking. Younger parity cows, cows milked earlier post-calving, and cows with lighter calves produced less colostrum. In general, colostrum quality of cows in this study was higher than in many previous studies; possible reasons include use of a relatively low-yielding cow type that produces low weight of colostrum, short calving to colostrum collection interval and grass-based nutritional management. The results of this study indicate that colostral IgG concentration can be maximised by reducing the time interval between calving and collection of colostrum.

Prospective studies have indicated an age-related impairment of the immune response. Carotenoids have been hypothesised to enhance immune cell function. The aim of the present study was to describe the age-related effects and the impact of in vivo dietary carotenoid depletion and repletion on specific and non-specific immunity. A total of ninety-eight healthy male subjects (aged 20–75 years) received a carotenoid-depleted diet for 3 weeks and were then supplemented daily for 5 weeks with 30 mg β-carotene, 15 mg lycopene and 9 mg lutein. Blood samples were collected at study entry, after depletion and supplementation, and biomarkers of immune status were determined. We found that serum IgA levels were positively correlated with ageing. Lymphocyte phenotyping indicated an increase with age in the memory T-helper cell subpopulation (CD4+CD45RO+) concomitantly with a decrease in naive T-helper cells (CD4+CD45RA+). A significant increase in the natural killer cells subpopulation and a small decrease in B lymphocytes were also observed, especially for the oldest volunteers. From ex vivo cell function exploration, a positive correlation was observed between age and IL-2 production of phytohaemagglutinin-stimulated lymphocytes. Neutrophils' bactericidal activity was significantly impaired with age (from 50 years) and was modulated by carotenoid status. An age effect was found on neutrophils' spontaneous migration but not on directed migration. Immune response in healthy human subjects is mostly affected by age rather than by dietary carotenoid depletion and repletion. Even in carefully selected healthy volunteers, some age-related immune changes occur predominantly from 50 years onwards. This immunosenescence could generate a loss in the immune system adjustment capacity.

This experiment tested the hypothesis that a lift in the nutrition of ewes, before lambing, to increase colostrum production would enhance lamb survival. In all, 261 mature Corriedale ewes, each with a single fetus from a synchronised mating, grazed native pasture to day 130 after mating; at which point they were weighed, condition scored and allocated to graze either native pasture or a pasture dominant with Lotus uliginosus. Five days later (14 days before the expected start of lambing) the ewes were allocated to one of four treatments and fed: (i) native pasture alone, (ii) native pasture plus a commercial high-energy lick, (iii) L. uliginosus pasture alone or (iv) L. uliginosus pasture plus whole maize. The weight, viscosity and concentration of components and immunoglobulin G in the colostrum that had accumulated at parturition, were measured for 10 ewes in each treatment. The lambs that survived to 20 days of age from the 221 ewes that were not milked, were recorded. The ewes supplemented with the lick or maize grain and those that grazed the L. uliginosus pasture alone accumulated two to three times more colostrum at birth than the ewes that grazed native pasture alone (396, 635 and 662 g v. 206 g; P < 0.01). The colostrum from the ewes that grazed only native pasture was more viscous (lower score) than that from the ewes supplemented with the lick or maize grain or the ewes that grazed the L. uliginosus pasture alone (scores of 4.1 v. 6.2, 6.5 and 6.4, P < 0.001) and, not surprisingly, the concentration of lactose in the colostrum of the ewes fed only native pasture was also much lower (1.1% v. 3.0%, 2.8% and 2.6%; P < 0.001)he survival of lambs from the ewes fed only native pasture was less than that of the lambs from ewes fed native pasture plus the commercial lick (81.8% v. 95.5%; P < 0.05) or the L. uliginosus pasture alone (92.4%, P < 0.05), and also tended to be lower than that for lambs born to ewes fed L. uliginosus pasture plus maize (91.8%, P = 0.08). The concentration of glucose in the blood of the lambs from the ewes that grazed only native pasture was lower than that of the other lambs (42.1 v. 60.2 ng/ml, P = 0.012). We conclude that the marked increase in colostrum production associated with the lift in ewe nutrition, just prior to lambing, enhanced lamb survival.

Hymenolepis murissylvatici elicits a humoral response in serum and in the intestine of the mouse from which it is immunologically rejected. In serum, significant differences were recorded 3 days after reinfection, while in intestinal lavages it takes place from day 9 after reinfection. In serum the response is largely the result of IgG and IgM antibodies whereas in the intestine, IgA is the most abundant antibody. Although specific IgE could not be demonstrated in serum, it was present in intestinal lavages, although rather late (i.e. day 14 after reinfection). Treatment of young worms in vitro both with immune serum or intestinal lavages had no apparent effect on their viability. Immune serum produced a complement independent precipitation on the surface of the worms in vitro. This reaction did not affect viability or infectivity of the parasite, as demonstrated by the successful implantation of treated worms in recipient mice. The above-mentioned results, together with the knowledge that the Hymenolepis model has no tissue stages and causes no tissue damage, make it probable that further study of this model will reveal some specific intestinal immunological reactions.

The aim of this study was to examine whether there was an increase of suppressor T cells, relative to helper T cells, in the intestinal lamina propria of Hymenolepis diminuta-infected rats, a condition which might allow the parasite to survive for the life-span of the host. Lamina propria cells were isolated by enzymatic procedure. All lymphocytes were passed over nylon wool columns in order to remove B cells; then the T cells were purified by a panning technique using monoclonal anti-T cell antibodies. Changes in the mitogen-stimulated synthesis of 1gM, IgG and IgA by normal peripheral blood indicator lymphocytes, as measured by sandwich ELISA, was used as an index of help and/or suppression. No significant suppressor T cell activity was observed in the cultures, either from control or infected intestine.

Histophilus somni (Haemophilus somnus) is one of the key bacterial pathogens involved in the multifactorial etiology of the Bovine Respiratory Disease Complex. This Gram negative pleomorphic rod also causes bovine septicemia, thrombotic meningencephalitis, myocarditis, arthritis, abortion and infertility, as well as disease in sheep, bison and bighorn sheep. Virulence factors include lipooligosaccharide, immunoglobulin binding proteins (as a surface fibrillar network), a major outer membrane protein (MOMP), other outer membrane proteins (OMPs) and exopolysaccharide. Histamine production, biofilm formation and quorum sensing may also contribute to pathogenesis. Antibodies are very important in protection as shown in passive protection studies. The lack of long-term survival of the organism in macrophages, unlike facultative intracellular bacteria, also suggests that antibodies should be critical in protection. Of the immunoglobulin classes, IgG2 antibodies are most implicated in protection and IgE antibodies in immunopathogenesis. The immunodominant antigen recognized by IgE is the MOMP and by IgG2 is a 40 kDa OMP. Pathogenetic synergy of bovine respiratory syncytial virus (BRSV) and H. somni in calves can be attributed, in part at least, to the higher IgE anti-MOMP antibody responses in dually infected calves. Other antigens are probably involved in stimulating host defense or immunopathology as well.

Craniocervical necrotizing fasciitis (CCNF) has a potentially high morbidity and mortality. Late presentation, shock and disseminated intravascular coagulation are associated with a particularly poor prognosis. Early recognition and aggressive treatment is advised. A case report is presented of a late presentation of necrotizing fasciitis of the face, neck and anterior thoracic wall. Despite adverse prognostic indicators, surgical debridement was performed. Intensive medical treatment included continuous renal replacement therapy and intravenous immunoglobulin. Survival in this case illustrates that the window of opportunity for surgically treating CCNF extends to the advanced stages of the disease, albeit with increased morbidity.

The objective of this study was to assess the effect of dietary saponins, extracted from the plant Quillaja saponaria, on the concentrations of immunoglobulins in sow colostrum and milk, and additionally to observe any effect on piglet performance. Twenty-two sows were allocated to each of two dietary treatments on day 72 of gestation, balancing for parity, fatness and past reproductive performance. Treatments were : control (C) and supplemented (Q; 2.5 g saponin per day as a top-dressing). Sows received 2.5 kg food once per day throughout gestation. Between days 72 and 93 of gestation Q sows received a saponin top-dressing as described. After day 93, all sows were given the same diet and managed in an identical manner. Colostrum samples were taken from all sows at farrowing on delivery of the first piglet then 4, 8, 24 and 72 h later and again on day 21 of lactation. A group of eight sows from each treatment were also blood sampled at farrowing, day 3 and day 21 of lactation. Concentrations of immunoglobulins IgG and IgA in the colostrum, milk and blood were not affected by sow treatment during gestation at any sampling point. Fat, lactose and cell counts were also similar across treatments in colostrum and milk. Protein tended to be higher in milk on day 3 but lower on day 21 (P < 0.1) in Q sows. Piglet performance was not affected by sow treatment during week 1 of lactation. However pigs suckling Q sows grew more slowly between days 8 to 14 (P < 0.05) and days 15 to 21 (P < 0.1). Q sows also had fewer stillborn piglets in their litters at farrowing (7.67 v. 13.25%, P < 0.05, s.e. = 1.93). It is concluded that dietary quillaja saponin given during this time period has no influence on sow lacteal immunoglobulin secretions. However an adverse effect on performance of the sucking piglet was observed, the reasons for which are unclear, but may be related to reduced milk protein concentrations. Dietary quillaja saponin during gestation does however appear to reduce the incidence of stillborn piglets.

Two experiments were carried out to examine the effects of the timing and duration of mineral supplementation of the ewe's diet in the final 6 weeks of gestation on immunoglobulin G (IgG) absorption by their progeny. In experiment 1, 60 single-bearing ewes were allocated to one of four dietary treatments (no. = 15) and offered a basal diet of grass silage ad libitum, containing 50 g/kg molassed sugar-beet pulp, which was supplemented with concentrates for the final 7 weeks of pregnancy and were additionally provided with a daily mineral/vitamin supplement for the final 6 weeks (W-6), 4 weeks (W-4), 2 weeks (W-2) or no mineral/vitamin supplement, (control; W-0). The supplement contained Ca, P, Na, Mg, Mn, Zn, Se, Co, I and vitamin E and was offered at the daily rate of 48 g per ewe. The ewes were milked at 1, 10 and 18 h post partum and measured quantities of colostrum, proportional to birth weight were fed back to the progeny via a stomach tube. At each milking, colostrum yield was recorded and colostrum samples taken to determine the concentration and yield of IgG. Treatment had no effect (P > 0.05) on the yields of colostrum or IgG to 18 h post partum. The efficiency of IgG absorption was lower (P < 0.001) in the progeny of ewes who received supplementary minerals (W-6, 0.069, W-4, 0.078, W-2, 0.072, W-0, 0.261; s.e. 0.0244. P < 0.001) regardless of the duration of the mineral/vitamin supplementation period and this resulted in a reduced concentration of IgG in the lamb's serum. In experiment 2, 40 twin-bearing ewes were allocated to one of four dietary treatments (no. = 10) and offered a basal diet of grass silage ad libitum which was supplemented initially with 500 g of a concentrate containing 140 g crude protein (CP) per kg from day 98 to 133 of gestation and then replaced with 700 g/day of a concentrate containing 180 g/kg CP from day 134 of gestation until lambing, in addition to one of the following mineral/vitamin supplementation treatments : no supplementary minerals, W0 (control); 48 g of supplement per ewe per day in weeks 6 and 5 pre- partum (W6–5), or weeks 4 and 3 pre-partum (W4–3), or for the final 2 weeks pre-partum (W2–1). The ewes were milked and the lambs fed as in experiment 1. Again, treatment had no effect (P > 0.05) on the yields of colostrum or IgG to 18 h post partum. When ewes were offered the mineral/vitamin supplement in the final 2 weeks of gestation their progeny had a lower (P < 0.01) serum IgG concentration (4.6 g/l) than in the control treatment (14.0 g/l) or when the supplement was offered either in weeks 3 and 4 (11.3 g/l) or weeks 5 and 6 pre-partum (14.3 g/l). IgG absorption efficiency followed the same pattern as lamb serum IgG concentration. We conclude that supplementation of the ewe's diet at the level used in these studies for the final 2 weeks of pregnancy results in the production of offspring with a reduced ability to absorb colostral IgG. Furthermore, in order for this impairment of the IgG absorptive ability of the lamb to manifest itself the supplementation must occur for the final 2 weeks of gestation and supplementation for a 2-weekly period earlier in gestation will not elicit the same effect.

Three experiments were carried out to evaluate the effects of varying levels of mineral and iodine supplements when offered to ewes in late pregnancy on lamb serum immunoglobulin G (IgG) concentrations. In experiment 1, 44 individually housed ewes were allocated to one of four treatments (no. = 11) and offered a basal diet of grass silage ad libitum which was supplemented with 500 g/day of a concentrate (190 g/kg of crude protein (CP)), in addition to mineral/vitamin fortification at the rate of 0 g (C), 17.3 g (LM), 34.6 g (MM) or 52.0 g (HM) per day for the final 7 weeks of pregnancy. The mineral/vitamin supplement contained Ca, P, Na, Mg, Mn, Se, I, Co, Mn and vitamin E. The ewes were milked at 1 h, 10 h and 18 h post partum and measured quantities of colostrum, proportional to lamb birth weight, were fed back to the lambs via a stomach tube. Treatment had no effect on total colostrum yield or total IgG yield to 18 h post partum (P > 0.05). There was a linear decrease in serum IgG concentration and IgG absorption efficiency as mineral supplementation increased (P < 0.001). In experiment 2, which was carried out in conjunction with experiment 1, 44 ewes were allocated to four treatments (no. = 11) and offered the same basal silage/concentrate diet as in experiment 1, in addition to receiving one of the following supplements : (C) control, as in experiment 1; (HM), as in experiment 1; (−I), ewes offered the same mineral/vitamin supplement as HM but with iodine excluded; (I0), ewes offered a daily mineral supplement of iodine only at a level of 40 mg per ewe, equivalent to the iodine inclusion in the 52 g of minerals offered in HM. The iodine-supplemented progeny (HM and IO) had lower (P < 0.001) serum IgG concentrations and higher soil scores (P < 0.05) than the C and −I progeny. In experiment 3, the effects of varying levels of iodine supplementation when offered to ewes during the final 6 weeks of pregnancy on lamb serum IgG values were examined. Forty-eight individually housed ewes were allocated to one of four treatments (no. = 12) and offered grass silage ad libitum, which was supplemented initially with 500 g of a concentrate (140 g/kg of CP) from days 99 to 130 of gestation and then replaced with 700 g/day of a concentrate (180 g/kg of CP) from day 131 of gestation until lambing. In addition, the diet of each ewe was supplemented on a daily basis with iodine at the rate of 0 mg (C), 8.9 mg (LI), 17.7 mg (MI) or 26.6 mg (HI). There was a negative linear reduction in serum IgG concentration and IgG absorption efficiency as maternal dietary iodine supplementation increased (P < 0.001). We conclude that supplementation of the ewe's diet in late pregnancy with 17.3 g of a mineral supplement as formulated in the current experiment lowers the lamb's ability to absorb colostral IgG, and offering only the iodine component of this mineral supplement, at a level which approximates to about one third of currently quoted toxicity levels, will result in reduced serum IgG concentration in the lamb. These findings suggest the need to re-examine current toxicity values for iodine.

Two experiments were carried out to quantify the intake of mineral blocks by ewes in group- and individually fed situations, and to examine the effects of mineral block intake on food and water intake, colostrum production and lambs' immunoglobulin G (IgG) absorption when ewes are individually housed and offered maize or grass silage with a concentrate supplement. In experiment 1, mineral blocks were offered to 359 ewes either when grazing at mating time (no. = 200) or, when indoors in the last 4 or 7 weeks of pregnancy, the latter as either twin-bearing ewes that were group-fed (no. = 18) or individually fed (no. = 27) or single-bearing ewes that were group-fed (no. = 114). Block intake was measured on a weekly basis. In experiment 2,a2X2 X 2 factorial design was used to compare the effects of forage (grass or maize silage), restricted mineral block access and added minerals/vitamins in the concentrate on food and water intakes, colostrum production and immunoglobulin absorption by the lamb using 64 twin- bearing ewes that were individually housed. Grass silage and maize silage were offered ad libitum, concentrates were offered at a flat rate of 400 g per head per day. Mineral blocks were offered to ewes for 3 h/day. Following lambing, the ewes were hand milked at 1,10 and 18 h post partum. Colostrum samples were assayed for immunoglobulin G (IgG) content. Lambs were blood sampled at 24 h old to determine serum IgG value. In experiment 1, mean daily mineral block intake per ewe was lowest at mating time (19 g) and highest when ewes were individually housed (194 g). In experiment 2, intakes of dry matter(DM) and energy were higher (F < 0.05) in the maize silage treatments. Similarly, when ewes had access to mineral blocks they had higher (P < 0.05) intakes of DM, energy and protein in addition to having a higher water intake (2.24 v. 0.771 per ewe per day; s.e. 0.139; P < 0.01). The mean total colostrum yield to 18 h post lambing at 1734 ±98.0 ml was unaffected by any of the treatments. When ewes had access to mineral blocks their lambs had lower (6.8 v. 18.8; s.e. 1.48; P < 0.01) serum IgG values and the efficiency of IgG absorption from the colostrum into the blood stream was reduced (0.097 v. 0.247; s.e. 0.0214; P < 0.01). In conclusion, the data show that there is wide variation in mineral block intake in different situations and that intake of some minerals can exceed toxic values. Additionally, when individually fed pregnant ewes have access to blocks for just 3 h/day, there is a significant increase in water intake and a dramatic reduction in lamb serum IgG concentration and in the efficiency of absorption of colostral IgG into the blood. We suggest that while mineral blocks can confer advantages in specific situations, there is the need to revisit their formulation and to further research the mode of action responsible for the compromised IgG absorption.

Ninety twin-bearing ewes were given food individually and allocated to five (no. = 18) treatments in order to determine the effects of supplementing their diet in late pregnancy with mineral-block components on colostrum production, lamb serum immunoglobulin G (IgG) concentration and colostral IgG absorption. Ewes were offered grass silage ad libitum, supplemented with 400 to 500 g per ewe per day of concentrates from day 99 of gestation, in addition to receiving one of the following supplements: C, (control) no supplement; B, mineral block; ML, liquid molasses; MN, granular minerals; ML + MN, liquid molasses and granular minerals. The experiment commenced on day 99 of gestation. Ewes were milked at lh, 10 h and 18 h post lambing and all lambs were fed measured quantities of colostrum, proportionate to birth weight, via stomach tube. Treatment had no effect (P > 0-05) on colostrum yield at lh, 10 h or 18 h post partum or on total colostrum yield to 18 h post partum. Ewes offered molasses (ML) or molasses plus minerals (ML + MN) had a lower colostral IgG concentration at lh post lambing than the control ewes (C) (P < 0-05). Ewes offered molasses (ML) also had a lower colostral IgG concentration than the control (C) at 10 h post partum (P < 0-05). Treatment had no effect on total IgG yield to 18 h post partum. When ewes were supplemented with minerals in any combination, with or without molasses (B, MN, ML + MN) it resulted in lambs having an impaired ability to absorb colostral IgG. Lambs from treatments B, MN and ML + MN had significantly poorer efficiency of colostral IgG absorption than lambs born to control ewes (C) or molasses (ML) supplemented ewes (P < 0-001). This in turn resulted in the progeny of mineral supplemented ewes (B, MN or ML + MN) having lower serum IgG concentration at 24 h post partum than either the control (C) or the molasses treatments (ML) (P < 0-001). When ewes were supplemented with molasses only (ML) lamb serum IgG content at 24 h was lower than in lambs born to control (C) ewes (P < 0-05) but this was as a result of a lower intake of colostral IgG (P < 0-05) and not a result of reduced IgG absorption efficiency. In conclusion, the data show that when ewe mineral intake is high in late pregnancy, as was the case in the current experiment, lamb serum IgG concentration and colostral IgG absorption efficiency are reduced. Further work is required to determine which component of the mineral formulation is responsible for this reduced IgG absorption efficiency and the mechanism through which this impaired efficiency operates.

Due to the structure of the placenta in the horse (epitheliochorial) and the as yet un-activated immune system of the foal at birth, the transfer of maternal immunoglobulin G (IgG) is essential in the protection of the young foal until its own immune system develops. The fluidity of intestinal cell membranes may affect the transfer of IgG by receptor mediated endocytosis. In the present experiment we studied the effect of the addition of supplements rich in either alpha-linolenic acid or oleic acid to the diet of the mares starting 1·5 months before foaling and for 1 month after foaling on the passive transfer of IgG and the fatty acid composition of mammary secretions and plasma of foals. Twenty-six mares were allocated to one of two treatment groups (L: linseed supplement, no. = 13 and R: rapeseed supplement, no. = 13) according to date of foaling and live weight to produce two homogeneous groups. Mammary secretions were collected to measure IgG and fatty acid composition. Jugular blood samples were taken from the foals at time 0, 12 h, 24 h, 48 h, 1 week, 2 weeks, 3 weeks and 4 weeks after foaling to measure the concentration of IgG. A subsample of foals was used to measure the IgG absorption coefficient and the plasma fatty acid compositon. There was no effect of dietary treatment on the length of gestation, the production and transfer of IgG. Group L mares produced mammary secretions which were richer in C18: 3 and poorer in C18: 1 than group R mares (P < 0·001). Contrary to expectations the C18: 3 content of blood from foals at birth from both dietary treatments was very low and there was no difference between dietary groups. The percentage of C18: 3 and C18: 2 in fatty acids increased in foal blood only after sucking had occurred, with a difference between dietary groups (L > R). In addition, the percentages of C20: 3 and C20: 4 were higher in the foals at birth than 48 h later (P < 0·001) and at birth they were highest in the R group compared with the L group foals (P < 0·05 and P 0·10, respectively). In conclusion, the attempt to increase the supply of C18: 3 during gestation to foals and to improve the transfer of IgG post partum did not appear to succeed, perhaps because the foal uses C22: 6 (produced from C18: 3) for brain growth.