Hyperleptinemia in Mares: Prevalence in Lactating Mares and Effect on Rebreeding Success

Previous research from our laboratory showed that approximately one third of obese, nonfoaling mares displayed a condition of hyperleptinemia coupled with hyperinsulinemia that resembled type 2 diabetes in humans. The current study was performed to evaluate the prevalence of the hyperleptinemic syndrome in lactating mares and its possible impact on their rebreeding success. Additionally, we investigated possible relationships between leptin levels in lactating versus nonlactating mares. In experiment 1, jugular blood samples were collected from 198 lactating mares on two occasions approximately 2 weeks apart. The mares resided on eight farms in Louisiana; breeds included Thoroughbred (n = 86), Quarter Horse (n = 71), Warmblood (n = 24), and draft-type (n = 17). Body condition scores (BCS) were measured at the time of blood sampling; plasma samples were assessed for leptin and progesterone concentrations. Reproductive and medical histories, as well as feeding regimens, were compiled on each mare. Based on our previous reports and examination of the current data, a mare was considered hyperleptinemic if her plasma samples contained greater than10 ng/mL leptin; normal was considered 6.0 ng/mL or less; mares with levels above 6.0 and 10 ng/mL or greater were classified as intermediate. Overall mean leptin concentration was 4.7 ng/mL, and average BCS was 5.5. After analysis, 24 mares were classified as hyperleptinemic (12%), 138 were classified as normal (70%), and 36 were classified as intermediate (18%). Leptin concentrations were affected by BCS (P = .08), with higher concentrations in mares with higher body condition; however, there were hyperleptinemic mares with BCS of 4 to 5.5. Feeding regimen affected leptin concentrations (P < .01), with mares on pasture full-time having the highest concentrations. There was no effect of breed, mare age, number of years the mare had been bred, number of live foals, progesterone concentrations, or last foaling date on leptin concentrations. Rebreeding success averaged 81% overall and was not affected by leptin classification. In experiment 2, nonfoaling mares kept on pasture had mean leptin concentrations of 7.0 ng/mL; 8 of 31 mares (26%) displayed hyperleptinemia. Mean leptin concentration was correlated with BCS (R² = 0.65; P < .02) but was not affected by age of the mare. It was concluded that the hyperleptinemic condition occurs in lactating broodmares, even at BCS as low as 4. The overall incidence appears to be lower in broodmares than in nonfoaling mares, likely because of their lower BCS in general and the energy demands of lactation. Hyperleptinemia did not affect rebreeding success at the end of the breeding season.     

Effects of season and body condition on appetite, body mass and body composition in ad libitum fed pony mares

Changes in appetite, body mass (BM), body condition score (BCS), direct (ultrasonographic) and indirect (deuterium oxide dilution technique) measures of body fat were monitored in Welsh Mountain pony mares (n = 11, 5–19 years of age) offered ad libitum access to a complete diet (gross energy 16.9 ± 0.07 MJ/kg dry matter) for 12 weeks during summer (n = 6; 246 ± 20 kg) and winter (n = 5; 219 ± 21 kg). At the outset, each group comprised two thin (BCS 1–3/9), moderate (BCS 4–6/9) and obese (BCS 7–9/9) animals.For ponies that were non-obese at the outset, BM was gained more rapidly (P = 0.001) in summer (0.8 ± 0.1 kg/day) than winter (0.6 ± 0.0 kg/day). This was associated with a seasonal increase in dry matter intake (DMI) which became maximal (summer, 4.6 ± 0.3% BM as DMI/day; winter, 3.5 ± 0.1% BM as DMI/day) during the second month. The appetite of the obese ponies was half that reported for non-obese animals in the summer and BM remained constant irrespective of season.Body ‘fatness’ increased progressively for non-obese but not obese ponies. Body fat content was exponentially associated with increasing BCS but BCSs >6 were not useful indicators of actual body fat. Endogenous circannual mechanisms to suppress winter weight gain were insufficient to prevent the development of obesity in ad libitum fed ponies.     

High or Low Body Fat Deposition in the Presence of a Normal Oral Sugar Test is Not Associated With Postthaw Semen Parameters in Stallions

This study compared the postthaw semen parameters of stallions with high and low body condition score (BCS) and evaluated associations between body morphometric parameters and postthaw semen parameters. Twenty stallions were split into Low BCS (BCS<7, n = 11) and High BCS (BCS ≥7, n = 9) groups, and underwent a complete morphometric analysis (e.g., neck scores and circumference, crest neck height, body weight, and height), and subcutaneous body fat thickness (SFT) at the tail head, withers, shoulders, and retroperitoneal space. A fasted oral sugar test (OST) was conducted on all stallions. One ejaculate from each stallion was frozen with a commercial egg yolk-based extender. Postthaw sperm motility parameters, plasma membrane integrity, mitochondrial membrane potential, hydrogen peroxide and intracellular superoxide production, and lipid peroxidation were analyzed for all stallions. The circumference at 25% and 50% of the neck’s length were larger for High-BCS stallions (P < .05). There were no differences between groups for the neck crest height (P > .05). Stallions with High BCS had greater SFT at the tail head than stallions with Low BCS (P < .05); however, there were no differences between groups in the SFT at the shoulders and withers (P > .05). All stallions had resting blood glucose below the cutoff for equine metabolic syndrome. There were no differences between groups for resting glucose concentrations or for a peak at 30 or 60 minutes after initiation of the OST (P > .05). There were no differences in sperm parameters between groups (P > .05). Collectively, the findings of the present study suggest that High BCS or Low BCS in the presence of normal OST do not explain post-thaw semen parameters.     

Effect of fat supplementation during transition period on plasma leptin and non‐esterified fatty acid concentrations in Holstein cows

The objective of this experiment was to investigate the effect of fat supplementation during the transition period on pre and postpartum body weight (BW), body condition score (BCS), non‐esterified fatty acids (NEFA), glucose and leptin concentrations in Holstein cows. Holstein cows (n = 15) received a low fat diet (LF; 1.61 Mcal net energy for lactation (NEL)/kg of dry matter [DM]), moderate fat diet (MF; 1.68 Mcal NEL/kg DM) or a high fat diet (HF; 1.74 Mcal NEL/kg DM) for 4 weeks prior to calving. All cows were fed similar lactation diets ad libitum (1.74 Mcal NEL/kg DM) for 30 days after calving. Increasing diet energy density during transition period had no effect on prepartum DMI, BCS, BW, glucose and NEFA concentrations (P > 0.05); but leptin concentrations and energy balance (EB) were affected by treatments (P < 0.05). Animals fed HF had less plasma leptin prepartum. After parturition, BW, milk production, milk fat, protein, urea nitrogen and plasma glucose concentrations were affected by prepartum diets (P < 0.05). Fat supplementation prepartum did not affect postpartum NEFA. In conclusion, prepartum fat supplementation decreased leptin concentration prepartum.     

Endocrine Profile Comparisons of Fat Versus Moderately Conditioned Mares Following Parturition

The influence of progesterone, luteinizing hormone (LH), and estrogen on the mare's estrous cycle has been well researched and documented, but other endocrine profiles have not received as much attention. To evaluate endocrine concentrations in fat-conditioned (body condition score [BCS] of 7–8) versus moderately conditioned mares (BCS of 5–6), 24 mares were allotted to and maintained in respective groups from late gestation until pregnancy was confirmed after breeding on the second postpartum estrus. Serum concentrations of thyroxine (T₄), insulin-like growth factor-1 (IGF-1), and leptin were assayed to characterize circulating blood concentrations. Additionally, LH and progesterone serum concentrations were assayed to evaluate the estrous cycle status of the mares. Leptin and progesterone concentrations were not different (P > .05) between the groups. Nevertheless, serum concentrations of T₄ were higher (P < .01) and IGF-1 concentrations lower (P < .01) in moderately conditioned as compared with fat-conditioned mares during times of ovulation and the interovulatory period. Furthermore, serum concentrations of LH were found to be different between the groups only when the estrous cycle approached the second ovulation (P < .0001). Results of this study suggest that mares maintained in a BCS of 5 or greater are similar in terms of reproductive efficiency. Although the circulating serum concentrations of T₄ and IGF-1 are different after parturition, their influence does not affect reproductive capabilities of mares with a BCS of 5 or greater.     

Effects of vitamin E and selenium administration on pregnant,heavy draft mares on placental retention time and reproductive performance and on white muscle disease in their foals

This study investigated the effects of administering vitamin E and selenium to pregnant heavy draft horsemares on the incidence of retained placenta and postpartum reproductive performance and on the prevention of the white muscle disease in their foals. In study A, 1,000 mg of vitamin E and 50 mg of selenium (E-SE 20 mL) were given to 22 mares 3 weeks before expected parturition (335 days counted from last mating), whereas 28 mares were used as controls. In study B, E-SE were administered 2 weeks before expected parturition at 2 dose levels, with 25 mares receiving 20 mL E-SE, 19 mares receiving 10 mL, and 29 mares kept as controls. Vitamin E and selenium were assayed in serum collected from some of the mares before administration of E-SE and again postpartum and from the foals immediately after birth. Serum selenium concentrations before E-SE administration were deficient (<65 ng/mL) in all mares (n = 48) but were increased in the postpartum sample from treated mares regardless of the dose or timing of administration (n = 31) (P = .05). Only study B mares were deficient in vitamin E prepartum, and both dose levels of E-SE had corrected this in the postpartum sample (P = .01). All foals were selenium deficient regardless of whether their dams had received E-SE or not, although concentrations were higher in foals from treated study A mares than from controls (P = .05). Mares with the highest selenium concentrations prepartum (40 ng/mL and over) had shorter placental retention times than mares with lower selenium concentrations (P = .05) and did not respond to E-SE with a further reduction in retention time. By contrast, mares with prepartum selenium concentrations between 20 and 40 ng/mL tended to respond to E-SE with a shortened placental retention time (P = .07). E-SE administration reduced the mean number of days from parturition to last mating (nonpregnant term) in study B mares (P = .05) and in mares with adequate prepartum vitamin E concentrations (>300 g/mL, P = .05). We conclude that maintaining high level serum vitamin E and selenium concentrations of prepartum mares is expected to increase fertility of selenium-deficient mares. Therefore, the regimen of vitamin E and selenium administrations to selenium deficient mares should be developed.     

Relationships Between Measurements of Body Fat in Thoroughbred Horses

Equine obesity is increasing in prevalence, and weight loss diets are frequently recommended for these horses. However, there are also management situations in which horses are deemed to be too thin. To monitor the efficacy of weight change programs, estimates of body fat are often made. There are several systems available to estimate body fat, and there are benefits and challenges to using each method. The objective of this study was to compare four different methods of estimating body fat in Thoroughbred horses. In 14 mature Thoroughbred horses, relationships among body condition score (BCS), morphometric measurements, ultrasonic measures of subcutaneous fat depots, and estimation of total body fat (BF_D) via measurement of total body water through deuterium oxide dilution were evaluated. Body condition scores ranged from 4.5 to 6.5 on a 9-point scale. Body condition score, heart girth-to-body weight ratio, and BF_D were all positively correlated with each other (P < .05). Subcutaneous fat depth at the tailhead tended to be positively related to BF_D when only horses with BCS ≥ 5 were included (P = .0680). These data suggest that BCS remains a simple means of monitoring adiposity in mature horses in moderate condition. Tailhead fat depots may become useful for monitoring changes in body fat in Thoroughbreds with a BCS above 5, although more work with animals of higher adiposity is required and at different times of year.     

Oxidative Stress and Antioxidant Status in Standardbreds: Effect of Age and Training in Resting Plasma and Muscle

The hypothesis of this study was that yearlings would have more oxidative stress as measured by malondialdehyde (MDA), total glutathione (GSH-T), glutathione peroxidase (GPx), and nitric oxide (NO) than mature mares before training, but after they would have similar levels. Ten Standardbred yearling fillies and 10 mature Standardbred mares were split into trained and nontrained groups. Horses were trained 5 days/wk for 7 weeks. Blood and muscle samples were collected at rest on weeks 0, 2, 5, 7, and 9. At week 0, the yearlings had higher muscle GSH-T and NO concentrations (P = .03) than the trained mares. At week 9, plasma NO concentrations were lower in trained mares than in the trained yearlings (P = .007). Trained mares increased muscle MDA and decreased plasma MDA concentrations from weeks 0 to 9 (P < .01), while all mares increased muscle NO and GSH-T concentrations by week 9 (P < .05). Trained mares and yearlings had increased erythrocyte GPx activity at weeks 7 and 9 and GSH-T concentration at week 7 (P < .05). Mares had higher lipid peroxidation and lower antioxidant status in the muscle than the yearlings prior to training. Trained mares improved antioxidant status and oxidative stress levels through training, resulting in levels similar to the yearlings.     

Prediction of empty body composition of double-muscled beef cows

Twenty-four nonlactating and nonpregnant Belgian Blue double-muscled cows, with diverging parities (one to seven), body conditions and body weights (436 to 903 kg), were used to investigate empty body (EB) composition. Direct measurements of EB composition, such as water, fat, protein, ash and energy, were carried out after slaughter. EB weight (EBW) averaged 624.7 kg and consisted of 393.3 kg water, 122.3 kg protein, 84.5 kg fat and 24.6 kg ash and was characterized by an energy content of 6158 MJ. Relationships between body weight (BW), body condition score (BCS), chest girth, dressing percentage, carcass grading score, EBW, rib-cut components and EB composition were determined. Significant regression equations (P<0.001) with a coefficient of determination (R²) of more than 0.9 were obtained between BW or BW and BCS and EB water, EB fat and EB energy. The prediction of EB ash was less accurate (R²<0.75). The relationship could further be improved by inclusion of carcass characteristics and rib-cut components (R²>0.95). Energy contents of EB lipids and protein amounted to 39.3 and 23.2 MJ/kg. EB protein (197 g/kg) was higher in the present double-muscled cows than reported for non-double-muscled animals, while EB fat (126 g/kg) and EB energy (9.5 MJ/kg) were lower. One BCS unit corresponded with 26.7 kg EB fat (P<0.001; R²=0.659). It can be concluded that simple live animal measurements as BW and BCS can be considered as potentially useful predictors of EB composition in double-muscled cows. Theoretical calculations based on the present observed data indicated that body reserves were lower in Belgian Blue double-muscled cows than in most other breeds. Body reserve tissue may be limited in young primiparous suckling cows so that energy restriction may be detrimental for reproductive performance.     

Relationships among inflammatory cytokines, obesity, and insulin sensitivity in the horse

Recent studies associate obesity and insulin resistance in horses with development of abnormal reproductive function and debilitating laminitis. The factors contributing to insulin resistance in obese horses are unknown. However, human studies provide evidence that elevated inflammatory cytokines such as tumor necrosis factor alpha (TNFalpha), IL1, and IL6 play direct roles in development of obesity-associated insulin resistance. Thus, inflammation may be a key link between obesity and insulin resistance in horses. The aim of the current investigation was to examine possible relationships between obesity, inflammatory cytokines, and insulin sensitivity (IS) in the horse. Age was recorded and BCS and percent body fat (% FAT) were determined as measures of obesity in 60 mares. In addition, blood mRNA expression of IL1, IL6, and TNFalpha and circulating concentrations of TNFalpha protein (TNFp) were determined in each mare. Finally, fasted concentrations of insulin were determined, and IS was determined using the hyperinsulinemic, euglycemic clamp. Significant correlations between several variables provided evidence for the design of 4 population regression models to estimate relationships between measures of obesity, inflammatory factors, and IS in the sample population. The results of these analyses revealed that IS decreased as BCS and % FAT increased (P < 0.001) in the sample population. Additionally, increased IL1 (P < 0.05) and TNFp (P < 0.01) were associated with decreased IS. However, increased TNFalpha (P < 0.001) was associated with decreased IS only in mares 20 yr of age and older. Increased BCS and % FAT were associated with increased expression of TNFalpha (P = 0.053) and IL1 (P < 0.05), and increased TNFp (P < 0.05). Surprisingly, increased BCS and % FAT were associated with decreased IL6 expression (P = 0.05) in mares <20 yr of age. Finally, evaluation of the influence of obesity and inflammatory cytokines on IS within the same model suggested that BCS and % FAT (P < 0.001) with TNFalpha [mRNA (P = 0.07) and protein (P < 0.05)] are inversely associated with IS independently of one another. Combined, these results provide the first evidence associating obesity with increased inflammatory factors in the horse. Furthermore, the results suggest that an interrelationship exists among obesity, inflammatory cytokines, and IS in the horse and emphasize the need for further studies to elucidate the nature of these relationships.     

Characterization of Glucose Response Curves after Insulin Injection in Sensitive versus Insensitive Mares

The glucose responses to intravenous injections of a range of doses of recombinant human insulin were determined for six mares known to be insulin sensitive and six mares known to be insulin insensitive, with the goal of better characterizing the regression lines resulting from the two categories of mares. Insulin doses between 8 and 198 mU of insulin per kg of body weight (mU/kg BW) were administered intravenously between September 13 and 26, 2010, starting with 50 mU/kg BW on the first day. Higher and lower doses were administered on alternate days to obtain percentages of decreases in blood glucose concentrations between 10% and 70%. Linear regression analysis revealed that insulin-insensitive mares have glucose response curves with higher y intercepts (P = .066), less steep slopes (P = .0003), and less goodness of fit (P = .053) in addition to the expected greater dose required to produce a 50% reduction in blood glucose concentrations (ED50; P = .006), despite the similarities between their body weights and those of insulin-sensitive mares. Linear and nonlinear regression of responses to the 32, 50, and 79 mU/kg BW insulin doses with the overall estimates of ED50 and the natural log of ED50 indicated that the 50 mU/kg BW dose had the greatest coefficient of determination (>0.95). Generally, it appears that estimates of insulin sensitivity based on a single injection of insulin or on multiple injections of insulin are least variable for insulin-sensitive mares.     

High versus low body condition in mares: interactions with responses to somatotropin,GnRH analog,and dexamethasone

Mares that had previously been fed to attain body condition scores (BCS) of 7.5 to 8.5 (high) or 3.0 to 3.5 (low) were used to determine the interaction of BCS with the responses to 1) administration of equine somatotropin (eST) daily for 14 d beginning January 20 followed by administration of GnRH analog (GnRHa) daily for 21 d and 2) 4-d treatment with dexamethasone later in the spring when mares in low BCS had begun to ovulate. The majority of mares with high BCS continued to cycle throughout the winter, as evidenced by larger ovaries (P < 0.002), more corpora lutea (P < 0.05), greater progesterone concentrations during eST treatment (P < 0.04), and more (P < 0.05) large- and medium-sized follicles. Treatment with eST alone or in combination with GnRHa had no effect (P > 0.05) on ovarian activity or ovulation. Plasma leptin concentrations were greater (P < 0.002) in mares with high BCS; however, there was no effect (P > 0.10) of eST treatment. Plasma IGF-I concentrations were greater (P < 0.0001) in mares treated with eST compared with mares given vehicle, and mares with high BCS had greater IGF-I (P < 0.02) and LH concentrations (P < 0.02) than mares with low BCS. Plasma leptin concentrations in mares with high BCS were increased (P < 0.001) within 12 h of dexamethasone treatment; the leptin response (P < 0.001) in mares with low BCS was greatly reduced (P < 0.001) and transient. Glucose and insulin concentrations also increased (P < 0.0001) after dexamethasone treatment in both groups, and the magnitude of the response was greater (P < 0.0001) in mares with high BCS than in mares with low BCS. In summary,low BCS in mares was associated with a consistent seasonal anovulatory state that was affected little by eST and GnRHa administration. In contrast, all but one mare with high BCS continued to experience estrous cycles and(or) have abundant follicular activity on their ovaries. The IGF-I response to eST treatment was also reduced in mares with low BCS, as was the basal leptin concentration and leptin response to dexamethasone. Although low BCS and leptin concentrations were associated with inactive ovaries during winter and early spring, mares with low BCS eventually ovulated in April and May while leptin concentrations remained low.     

The effects of body weight,body condition score,sex, and age on serum fructosamine concentrations in clinically healthy cats

Background: Serum fructosamine (SF) concentrations depend on plasma glucose concentrations and are used to evaluate glycemic control in animals with diabetes mellitus (DM). Despite the strong association between obesity and DM, the effects of body weight (BW) and body condition on SF concentrations in clinically healthy cats have not been reported. Objective: The aim of the study was to evaluate the effects of BW, body condition score (BCS), sex, and age on SF concentrations in healthy cats. Methods: BW, BCS, and SF concentrations were determined in 84 clinically healthy client‐owned cats (50 neutered males, 33 spayed females, and 1 intact female) of known age. The cats were enrolled prospectively in the study. Results: Mean BW, median BCS, and mean SF concentrations for the 84 cats were 5.4 kg, 5/9, and 268.7±45.5 μmol/L (range 197–399), respectively. BW was weakly but significantly correlated with SF (r=.26; P=.02), whereas BCS was not. Cats weighing >5.4 kg and cats with BCS>5/9 had higher mean SF concentrations compared with cats weighing <5.4 kg and cats with BCS <5/9, respectively. Cats categorized as normal weight to obese by BW (BW≥4.0 kg) had higher mean SF concentrations compared with cats categorized as lean (BW<4.0 kg). For domestic shorthair cats, the same was true for BCS: cats with BCS≥4/9 had higher mean fructosamine concentrations than those with BCS<4/9. Male cats had significantly higher mean SF concentrations compared with female cats (285.1±45.3 vs 244.5±33.9 μmol/L, P<.001). Age did not affect mean SF concentrations. Conclusions: BW is positively correlated with SF concentration, and lean cats have lower SF concentrations than normal and obese cats. In contrast to previous reports, mean SF concentrations were higher in male cats than in female cats, even when males and females were matched based on BW, BCS, and age.     

Comparison of Nutrient Digestibility Between Adult and Aged Horses

There is little published work comparing digestibility in healthy adult versus healthy aged horses. Researchers hypothesized that there would be no differences in macronutrient digestibility between eight adult (5–12 years) and nine aged (19–28 years) horses fed three diets in a Latin square design. Seventeen stock-type mares were randomly assigned for a 5-week period to one of three diets: hay only (HAY), hay plus a starch- and sugar-rich concentrate (CHO), or hay plus a fat- (oil) and fiber-rich concentrate (FF). Each diet period comprised 3 weeks of outdoor group drylot feeding, 2 weeks of indoor stalled individual feeding, followed by a 72-hour digestibility trial including total urine and fecal collection. Feed, fecal, and/or urine samples were analyzed to determine dry matter, crude protein, fat, energy, calcium, and phosphorus apparent retention as well as apparent digestibility. Neutral detergent fiber digestibility was also determined. Mean body weight was lower in aged than in adult horses (455 ± 12 kg vs. 500 ± 13 kg; P = .02), but body condition score (BCS) did not differ between groups (aged horses, 4.8 ± 0.2 BCS and adult horses, 5.1 ± 0.2 BCS; P = .20). No age differences in digestibility, apparent digestibility, or apparent retention were seen for any of the variables measured. Based on the results of this study, total tract macronutrient digestibility appears to be similar between healthy adult and aged horses.     

Age-Dependent Effect of Foal Heat Breeding on Pregnancy and Embryo Mortality Rates in Thoroughbred Mares

The aim of the present study was to evaluate the correlation of age and heat cycle to determine reproductive efficiency in young and aged Thoroughbred mares bred on foal heat (FH) or on second heat (SH) after foaling. Embryo mortality (EmbM) was determined every time a mare was found open after a positive pregnancy diagnosis. Parturition to breeding interval, pregnancy rate (PregR) and EmbM rate were the dependent variables and the treatments were breeding on the FH or on SH. The cutoff age to obtain above-average probability for the EmbM was 10 years old. PregR in mares bred on FH was lower compared with SH (P < .01); however, it was neither affected by the age of mares (P > .05) nor by the age group of mares (P > .05). Regarding FH and SH, there was a difference in PregR in young mares (P < .01), unlike in aged mares (P > .05). EmbM rate was not different between mares bred on FH or SH (P > .05) although it was affected by age of mares (P < .01). EmbM was higher in oldest than young mares (P < .01). Aged mares bred on FH had a significantly higher EmbM rate compared with the young group also bred on FH (P < .01). In conclusion, the reproductive efficiency of Thoroughbred mares bred on FH is dependent of the age. Aged mares (≥10 years old) should be bred at their SH to reduce EmbM and improve reproductive performance.     

Lactation and reproductive performance of mares fed added dietary fat during late gestation and early lactation

Eighteen pregnant mares were randomly allotted to one of two treatment groups. The control group was fed a conventional concentrate and the fat group was fed a concentrate containing 5% feed-grade rendered fat. Both concentrates had the same nutrient:calorie ratio and were fed in amounts required to maintain zero change in percent body fat of the mares. During the study, which began 60 d prior to expected foaling date and ended 60 d postpartum, mares were monitored for feed intake, body weight, rump fat thickness, ration digestibility, plasma glucose and lipid concentrations, milk composition and reproductive efficiency. Birth weight, growth rate, and plasma glucose and lipid concentrations were also measured in foals. Mares fed fat consumed less concentrate (P<.09 during the last 60 d of gestation but consumed similar amounts of concentrate over 60 d of lactation. Protein and ether extract digestion was higher (P<.05 and P<.09, respectively) in the mares fed fat during the postpartum period. Dietary treatment had no influence on plasma glucose or lipid concentrations of the mares or plasma glucose concentrations of their foals, but foals whose dams were fed fat had higher plasma lipid concentrations at birth (P<.01), d 10 and d 30 (P<.05). Percent fat was higher in milk samples from mares fed fat at d 10 (P<.09, 1.23 vs .99%) and d 60 (P<.01, .72 vs .43%) of lactation. Reproductive performance was not significantly different between treatment groups, however there was a trend for a shorter postpartum interval and fewer cycles per pregnancy in the mares fed added fat. Foals from both groups were of similar size and weight at birth and had similar weight gains over 60 d, however, foals nursing mares fed fat tended to gain more weight in the first week of life (1.85 vs 1.56 kg/d) and have more rump fat at d 60 (.53 vs .44 cm) than foals nursing control mares.     

Connection between body condition score, chemical characteristics of body and reproductive traits of rabbit does

Body condition scoring (BCS) is widely used to evaluate the nutritional status of livestock (cows, ewes, sows). In intensive systems, rabbit does are generally inseminated 11 days post partum and, due to a hormonal antagonism and an energy deficit caused by concurrent lactation and pregnancy, they show low fertility. The aim of this investigation was to assess an in vivo method for scoring the body condition of does by verifying the association with the body fat depots, the chemical composition of body tissues, the ovarian status, the hormonal response and the reproductive performance. The evaluation of BCS, involving 66 multiparous lactating does inseminated at 11 days post partum, was based on the test of bone protrusions and fullness of muscle of the loin, rump and hind leg. The traits were subjectively scored using 0, 1 and 2 for poor, intermediate and good condition, respectively. For calculating an aggregate BCS, the hind leg score was omitted, because it is less correlated with the real body condition. Adding the respective score (0–2) of the loin and rump regions, 5 classes of BCS were obtained (0–4). This aggregate BCS was highly correlated with the body fat depots (r = 0.79), the ether extract content of muscle samples of Obliquus abdominis (r = 0.87) and Biceps femoris (r = 0.84), and the ether extract of the empty body (r = 0.84). There was a lower correlation with the body weight (r = 0.45). The increase of BCS corresponded to higher lipid content in the body parts considered, especially the Obliquus abdominis (from 2.0 to 10.0%) and fat depots (from 10.6 to 107.7 g/doe). BCS was not related to ovulation rate or embryo production, but was correlated with sexual receptivity and fertility.Plasma FSH and LH concentrations were determined by RIA, 48, 24, 0 h before and 1 h after GnRH administration and artificial insemination. Animals with extreme body condition scores (BCS ≤ 1 or BCS = 4) showed lower plasma FSH levels (20.0 vs. 34.5 ng/mL) than does with optimal body condition (2 ≤ BCS ≤ 3) and their preovulatory LH surge, released after GnRH administration, was less evident (16.9 vs. 20.3 ng/mL). The poor reproductive performance of does with extreme BCS could be explained by this pituitary activity. On day 11 post-partum, a high number of does (71.2%) had extreme BCS and showed a lower sexual receptivity (37.2% vs. 80.0%) and fertility rate (50.9% vs. 86.6%) than does in optimal condition. On these results, the possibility of applying an in vivo method for scoring the body condition of lactating rabbit does appears promising for use in on-farm reproductive management.     

The relationship between body condition,leptin, and reproductive and hormonal characteristics of mares during the seasonal anovulatory period

An experiment was conducted to determine the effects of high vs low body condition scores (BCS) produced by restricted feeding on reproductive characteristics, hormonal secretion, and leptin concentrations in mares during the autumnal transition and winter anovulatory period. Mares with BCS of 6.5 to 8.0 were maintained on pasture and/or grass hay, and starting in September, were full fed or restricted to produce BCS of 7.5 to 8.5 (high) or 3.0 to 3.5 (low) by December. All but one mare with high BCS continued to ovulate or have follicular activity during the winter, whereas mares with low BCS went reproductively quiescent. Plasma leptin concentrations varied widely before the onset of restriction, even though all mares were in good body condition. During the experiment, leptin concentrations gradually decreased (P < 0.0001) over time in both groups, but were higher (P < 0.009) in mares with high vs low BCS after 6 wk of restriction, regardless of initial concentration. No differences (P > 0.1) between groups were detected for plasma concentrations of LH, FSH, TSH, GH, glucose, or insulin in samples collected weekly; in contrast, plasma prolactin concentrations were higher (P < 0.02) in mares with high BCS, but also decreased over time (P < 0.008). Plasma IGF-I concentrations tended (P = 0.1) to be greater in mares with high vs low BCS. The prolactin response to sulpiride injection on January 7 did not differ (P > 0.1) between groups. During 12 h of frequent blood sampling on January 12, LH concentrations were higher (P < 0.0001), whereas GH concentrations (P < 0.0001) and response to secretagogue (EP51389; P < 0.03) were lower in mares with high BCS. On January 19, the LH response to GnRH was higher (P < 0.02) in mares with high BCS; the prolactin response to TRH also was higher (P < 0.01) in mares with high BCS. In conclusion, nutrient restriction resulting in low BCS in mares resulted in a profound seasonal anovulatory period that was accompanied by lower leptin, IGF-I, and prolactin concentrations. All but one mare with high BCS continued to cycle throughout the winter or had significant follicular activity on the ovaries. Although leptin concentrations on average are very low in mares with low BCS and higher in well-fed mares, there is a wide variation in concentrations among well-fed mares, indicating that some other factor(s) may determine leptin concentrations under conditions of high BCS.     

Effect of ω-3 Fatty Acid Supplementation to Gestating and Lactating Mares: On Milk IgG,Mare and Foal Blood Concentrations of IgG,Insulin and Glucose,Placental Efficiency,and Fatty Acid Composition of Milk and Serum From Mares and Foals

Limited research has been conducted to evaluate effects of fatty acid (FA) supplementation on mare and foal FA profiles and foal immunity. Dietary polyunsaturated FAs, particularly ω-3 FAs, increase fluidity of intestinal cell membranes. Fluidity of mammary tissues may also be altered to allow more incorporation of immunoglobulin G (IgG) into milk. Therefore, the goal of this study was to determine effects of incorporating dietary ω-3 FAs on mares, her milk, and her subsequent foal. Pregnant mares were assigned to one of three diets beginning 28 days before expected foaling date until 84 days after foaling. Diet 1 was a commercial feed (CON); diet 2 was diet 1 plus a fish oil blend (FO); and diet 3 was diet 1 plus a blend of fish and soybean oil (FSO). Mare serum FA concentrations were not affected by treatment (P > .05) with the exception of 20:5, which had a treatment × time interaction (P < .05). Mare milk FA concentrations were not affected by treatment (P > .05) with the exception of 16:1 and 20:5. Foal serum FA concentration was not affected by treatment with the exception of 18:2, which had a treatment × time interaction, and 20:5 (P < .0001), which was greatest in FO foals and least in CON foals. Dietary supplementation of ω-3 FAs did increase 20:5 in mare serum, milk, as well as serum of their subsequent foals. No differences were found for mare plasma IgG (P = .1318), serum insulin (P = .3886), plasma glucose (P = .2407), or milk IgG (P = .1262) concentrations for treatment. Foal plasma IgG (P = .2767), serum insulin (P = .4843), or plasma glucose (P = .1204) were not affected by treatment. Omega-3 FA in mare serum, milk, and foal serum were able to be manipulated by diet; however, IgG concentration was unchanged.     

Assessment of body fat in the pony: part I. Relationships between the anatomical distribution of adipose tissue, body composition and body condition

Reasons for performing study: Evaluation of equine body fat content is important for nutritional and clinical purposes. However, our understanding of total body fat and its regional distribution in the body is sparse. Currently, body fat evaluation relies on the subjective assessment of body condition score (BCS), which has never been validated against ‘gold standard’ chemical analysis or dissection measurements in ponies. Objectives: To define the relationships between subjective (BCS), objective (morphometric) indices of body fat and ‘gold standard’ measurements of actual body composition. Hypotheses: BCS and morphometry offer valid, noninvasive methods for determination of body fat in equids. Methods: Seven mature (mean ± s.e. 13 ± 3 years, 212 ± 14 kg, BCS 1.25–7/9), Welsh Mountain pony mares, destined for euthanasia (for nonresearch purposes), were used. For all ponies, body mass (BM), BCS and various morphometric measurements were recorded. Following euthanasia, all ponies were systematically dissected. Discrete white adipose tissue (WAT) depots were independently described. Gross, body chemical composition was determined by proximate analyses. Results: Total somatic soft tissues increased linearly (r²= 1.00), whereas body WAT content (1–26% live BM) increased exponentially (r²= 0.96), with BCS. WAT was equally distributed between internal and external sites in all animals irrespective of BCS. Nuchal fat was a poor predictor of total WAT (r²= 0.66). Periorbital WAT did not alter with BCS (r²= 0.01). Heart girth:withers height and ultrasonic retroperitoneal fat depth were closely associated with total, chemically‐extracted lipid which comprised 1–29% live BM (r²= 0.91 and 0.88, respectively). Conclusions and potential relevance: The exponential relationship between BCS and total body WAT/lipid suggests that BCS is unlikely to be a sensitive index of body fat for animals in moderate‐obese states. Morphometric measurements (body girths and retroperitonel fat depth) may be useful to augment subjective BCS systems.