Review: Feeding conserved forage to horses: recent advances and recommendations.

The horse is a non-ruminant herbivore adapted to eating plant-fibre or forage-based diets. Some horses are stabled for most or the majority of the day with limited or no access to fresh pasture and are fed preserved forage typically as hay or haylage and sometimes silage. This raises questions with respect to the quality and suitability of these preserved forages (considering production, nutritional content, digestibility as well as hygiene) and required quantities. Especially for performance horses, forage is often replaced with energy dense feedstuffs which can result in a reduction in the proportion of the diet that is forage based. This may adversely affect the health, welfare, behaviour and even performance of the horse. In the past 20 years a large body of research work has contributed to a better and deeper understanding of equine forage needs and the physiological and behavioural consequences if these are not met. Recent nutrient requirement systems have incorporated some, but not all, of this new knowledge into their recommendations. This review paper amalgamates recommendations based on the latest understanding in forage feeding for horses, defining forage types and preservation methods, hygienic quality, feed intake behaviour, typical nutrient composition, digestion and digestibility as well as health and performance implications. Based on this, consensual applied recommendations for feeding preserved forages are provided.

Effects of body condition and leptin on the reproductive performance of Lusitano mares on extensive systems.

The aim of this study was to investigate the effects of body condition (BC), BC changes, and plasma leptin concentrations on the reproductive performance of Lusitano broodmares on extensive systems. Data from 119 mares (ranging from 4 to 22 years of age) were collected over a period of four consecutive breeding seasons. Each case was considered as one foaled mare bred in 1 year. Body condition changes at conception (ΔBCScon) showed a strong effect on fertility at the first two postpartum estrous cycles and a significant interaction with body condition score at conception (BCScon) was observed (P < 0.01). The best fertility results were obtained with positive and greater ΔBCScon. The best predictive value of fertility (91%) was achieved when the BCScon was 3.0 and ΔBCScon was 0.375. Global foaling rate for the 4-year period was 74.5%. Mean foaling interval and gestation length were, respectively, 368.0 ± 2.8 and 340.3 ± 1.0 days. Gestation length was influenced by the month of foaling (P < 0.05) and decreased as mares got older (P < 0.01). The number of estimated estrous cycles per live foal was 1.78 ± 0.12, including foal heat ovulation. Leptin was correlated with BCS (0.41; P < 0.001), but in the present study, plasma leptin concentrations on late gestation and early lactation did not influence fertility results. At 90 days of age, lower growth performances were obtained in foals which dams presented negative BCS changes on the first 3 months of lactation (P < 0.05). In conclusion, BC changes at early postpartum period influence the reproductive efficiency of broodmares and the growth of their suckling foals. These findings are important to help breeders on management options concerning feeding strategies in the Lusitano production systems and others under similar conditions.

Coumestrol and its metabolite in mares' plasma after ingestion of phytoestrogen-rich plants: potent endocrine disruptors inducing infertility.

Phytoestrogens exist in plants that are present in forages fed to horses. They may compete with 17-ß estradiol and influence the estrous cycle. Therefore, the objective was to determine whether coumestrol from clover-mixed pastures is present in mare's plasma after their ingestion (experiment I), and when this phytoestrogen was present in mare's plasma after ingestion (experiment II). The effect of a long-term ingestion of phytoestrogens on estrous cycle disruption was assessed (experiment III; clinical case). Experiment I was carried out in nonpregnant anestrous and cyclic Lusitano mares (n = 14) kept on clover and grass-mixed pastures, and supplemented with concentrate and hay or cereal straw. Blood and feedstuff were obtained from November to March. In experiment II, stabled cyclic Lusitano mares (n = 6) were fed for 14 days with increasing amounts of alfalfa pellets (250 g to 1 kg/day). Sequential blood samples were obtained for 8 hours after feed intake on Day 0 (control) and on Days 13 and 14 (1 kg/day alfalfa pellets). Experiment III mares were fed with a mixture of alfalfa and clover haylage for 5 months (group 1; n = 4) or for 9 months (group 2; n = 12). Estrous cycle was determined on the basis of plasma estradiol (E2), progesterone (P4), and ultrasound (experiment III). Concentrations of phytoestrogen coumestrol and its metabolite methoxycoumestrol were determined by high-performance liquid chromatography coupled with mass spectrometry. Phytoestrogens decreased in pasture from November until March (P < 0.01) (experiment I), but were always detected in mares' plasma. In experiment II, plasma-conjugated forms of coumestrol and methoxycoumestrol were higher on Days 13 and 14 than in control (P < 0.05). The highest concentrations of conjugated form of coumestrol were at 1.5 and 4 hours (P < 0.001), whereas its free forms peaked at 1 and at 3.5 hours after ingestion (P < 0.05). Methoxycoumestrol-conjugated form concentration was the highest at 1.5 and 5 hours (P < 0.001), whereas its free form peaked at 1 hour (P < 0.05) and at 1.5 hours (P < 0.001). Long-term intake of coumestrol caused lack of ovulation, uterine edema, and uterine fluid accumulation (experiment III). Coumestrol and methoxycoumestrol in both forms were higher in group 2 (while still ingesting haylage) than in group 1, after haylage withdrawal (P < 0.001). These data show that in the mare, coumestrol and its metabolite increase in blood after ingestion of estrogenic plants and can influence reproduction in mares as potent endocrine disruptors.