Energy supplementation and herbage allowance effects on daily intake in lactating mares1

Abstract

Little is known about how to manage grazing horses, including the thresholds under which energy supplementation is required. Here we investigated the effects of daily herbage allowance (DHA) and energy supplementation (ES) on daily herbage intake in lactating mares of light breeds grazing high-quality regrowth during summer. Three contrasting DHA, low (LOW), medium (MED), and high (HIGH), that is, 35.0, 52.5, and 70.0 g DM∙kg BW(-1)∙d(-1), respectively, were obtained by adjusting pasture strip width. Eighteen Anglo-Arab and French Saddle lactating mares were either supplemented with 2.6 kg DM barley/d (SUP group; n= 9) or left nonsupplemented (NSUP group; n = 9) throughout the experiment. For 3 successive 2-wk periods, 3 groups of SUP mares (n = 3) and 3 groups of NSUP mares (n = 3) grazed each DHA according to a 3 × 3 Latin square design. Pregrazing sward surface height (SSH) was similar between treatments (26.6 cm), but postgrazing SSH differed significantly between each DHA (2.9, 4.4, and 5.7 cm for LOW, MED, and HIGH, respectively; P < 0.001). Herbage DMI (HDMI) increased linearly from 18.5 to 23.4 g DM∙kg BW(-1)∙d(-1) with increasing DHA (i.e., 0.13 kg DM eaten/kg DM of herbage offered; P < 0.001) independently of ES and with no significant ES × DHA interaction. This increase in HDMI resulted from an increase in grazing time between LOW (961 min/d) and MED and HIGH (1,021 min/d; P < 0.01) and from an increase in intake rate between LOW and MED (11.8 g DM/min) and HIGH (13.6 g DM/min; P < 0.01). Total digestible DMI (TDDMI) and NE intake (NEI) increased linearly from 12.3 to 15.2 g DM∙kg BW∙(-1)d(-1) and from 136.6 to 165.8 kJ∙kg BW(-1)∙d (-1)with increasing DHA (P < 0.001), respectively. Total digestible DMI and NEI were significantly lower for NSUP than for SUP mares: 12.5 vs. 14.9 g DM∙kg BW(-1)∙d(-1) (P < 0.01) and 134.6 vs. 166.5 kJ∙kg BW(-1)∙d(-1) (P < 0.001), respectively. Whereas SUP mares always met their energy requirements, NSUP mares no longer met theirs when DHA fell below 66 g DM∙kg BW(-1)∙d(-1) (i.e., 39 kg DM∙mare(-1)∙d(-1)).

Ingestion of Soil by Grazing Sport Horses

“…The daily grass DM intake was estimated for each horse during the last 6 d of each period following the methodology described by Collas et al [17] by dividing the faecal output (dry weight over 24 h, attributable to grass) by the indigestible proportion of ingested grass (i.e., 1-DM digestibility of ingested grass). Therefore, the faeces of all animals were individually collected and weighed each day of measurement.…”

“…In dairy cows, Pérez-Prieto et al [26] observed that the effect of pre-grazing grass mass on grass intake was affected by the height above which forage supply was estimated. According to the literature, both cattle and equines can graze down to 2-3 cm, even less for equines [17,26,27]. This underestimation of the amount of forage offered has allowed the horses on DHA 2% to achieve a daily grass intake of 14.0 kg DM (2.33% BW) to cover their requirements by grazing shorter (<3.5 cm) than horses on DHA 3 and 4% (>4 cm).…”

“…In a study testing three DHA levels (35, 52.5 and 70 g DM/kg BW/d, estimated at ground level) with lactating saddle mares in a similar strip grazing system (new strip of fresh herbage offered every two days), Collas et al [17] reported a linear effect of DHA on grass DM intake with an increase of 0.13 kg DM ingested/kg DM of grass offered at ground level. These authors also observed a DHA influence on grazing behaviour with daily grazing time significantly longer on medium and high than on low DHA.…”

Growth and Development of the Lusitano Foal on Extensive Systems

“…Lactating mares can adjust intake while they are fed forage-based diets to meet energy requirements (Martin-Rosset et al, 2015c). However, a study in temperate regions showed that lactating mares not supplemented at pasture, no longer meet their requirements when daily herbage allowances fall below 66 g DM/ kg BW/day (Collas et al, 2015). In the Lusitano stud farms based on EGS, mare and foals supplementation occurs during the periods with low or even no pasture biomass production, with preserved forages (mostly grass hay or grass-legume mixed hay) and/or concentrate feeds, although the remnant dry herbage is still available as feed resource during the summer months.…”