Comparison of energy rationing systems for late gestation ewes: Impacts on ewe and lamb performance1

Abstract

The objectives of this study were 1) to compare the effects of a ME () or a NE () system for rationing ewes during late gestation on ewe and progeny performance and 2) to investigate incremental increases in NE allocation above 100% of recommendation during late gestation on ewe and progeny performance. Fifty-two twin-bearing ewes ( = 13 per treatment) were rationed to either 100% of recommended ME requirements (100% ME) or 100, 110, or 120% of recommended NE requirements (100% NE, 110% NE, and 120% NE) from d 112 of gestation to parturition. Mean energy intake, measured as ME and NE, from Day 112 of gestation to parturition was higher in all NE treatments compared with 100% ME ewes ( = 0.01). Ewes offered the 3 NE treatments had a higher live weight at parturition compared with 100% ME ewes ( = 0.02), with 100% NE and 120% NE ewes still being heavier than 100% ME ewes at 35 d postpartum ( = 0.02). Increasing NE allowance resulted in a linear decrease in the level of BCS loss prepartum ( = 0.01) and a linear increase in the level of BCS loss postpartum ( = 0.01). There was no difference observed between any of the treatments in total colostrum produced to 18 h postpartum ( = 0.29) or in total colostrum intake to 18 h postpartum ( = 0.27). Increasing maternal NE allowance led to a linear increase in lamb serum IgG concentration at 24 h postpartum ( = 0.03). The estimated milk production of 120% NE ewes tended to be higher than all other treatments at wk 6 of lactation ( = 0.08). Colostral SFA levels from 100% ME ewes was lower than that of all 3 NE treatments ( = 0.01), and unsaturated fatty acid (UFA) levels in colostrum of the 100% ME ewes were lower than those of the 100% NE ewes ( = 0.01). Cumulative levels of milk SFA, UFA, and MUFA did not differ between treatments ( = 0.19). Lamb growth rates during the first 5 wk postpartum were unaffected by treatment ( = 0.18) as were days to slaughter ( = 0.34). It can be concluded that both ME and NE systems used in this study are appropriate for formulating ewe diets during late gestation. Increasing NE allocation above 100% altered the pattern of body reserve mobilization during late gestation and early lactation without observed variations in lamb performance during this time.

Examining the Effects of Whole Crop Wheat Silage on Ewe Performance during Late Gestation Compared to Traditional Grass Silage across Three Prolific Breed Types

“…Late gestation nutrition is vital to ensuring a productive sheep enterprise by maximising flock performance [11,23]. The hypothesis stated that (1) replacing GS with WCWS in the ewe's diet during late gestation would increase forage DM intake and thus reduce the requirement for concentrate feed and (2) this response would be independent of prolific breed type.…”

“…Energy content of the gravid foetus (Et) = log10(Et) = 3.322 − 4.979 − 0.00643t (4) Daily energy retention in the foetus (Ec) = 0.25 Wo (Et (0.07372 − 0.00643t)) (5) in which: F = fasting metabolism, A = the activity allowance of the animal, Km = the efficiency factor for the utilization of ME for maintenance, Kc = the efficiency of energy utilization for conceptus gain, t = the number of days from conception, and Wo = the total expected litter weight at birth (kg). The initial BW of the ewe, recorded at the beginning of the acclimatisation period, day 84 of gestation, and the total expected litter weight 11 kg [23] were constants in the equation to determine the ME requirement for each ewe during the course of the feeding period (day 91 to day 147 of gestation). Individual requirements were revised on a weekly basis to allow for the increasing foetal energy demands as gestation progressed.…”

“…While daily differences in ME intake were relatively small (1.4 MJ ME per day), this accumulated to a reduction of ME intake over the feeding period of 78.4 MJ per ewe equivalent to 6 kg of concentrate DM. However, using BW as a sole indicator of the ewes' body reserves is a poor assessment of ewe condition [23] and therefore BCS was also used in this assessment. McGovern et al [11] reported higher BW and BCS at parturition for ewes with higher ME intake in late gestation though the magnitude of ME intake differences reported by McGovern et al [11] was greater than that in the current study.…”

“…Previous studies reported that CLW is a poor indicator of adequate ewe nutrition [43,44] with contradictory reports of the impact of modest (±20%) variations in late pregnancy energy intake on subsequent lamb birth weight [11,23]. However, studies reporting 35% differences in energy intake have reported differing lamb birth weights [45].…”

Developing a continuous adjustment factor for dry matter intake of gestating and lactating ewes

“…However, a number of studies have focused on the determination of the requirement of a specific race, considering that there is a nutritional difference between them (Ji et al, 2015;Pereira et al, 2017Pereira et al, , 2016Rodrigues et al, 2016). Certain researchers have worked on the effect of maternal nutritional requirement on progeny; these studies are called fetal programming, and are not usually studied in prediction equations (Campion et al, 2016;Hoffman et al, 2018;McGovern et al, 2015;Peine et al, 2018;Roca Fraga et al, 2018). Further investigation is warranted if the adjustments proposed in equations 5 and 6 would still apply to different levels of the plane of nutrition of gestating ewes.…”