Effect of condensed tannins inLotus corniculatusupon lactation performance in ewes

Abstract

A grazing experiment was conducted for 8 weeks in the spring/summer of 1993 at Palmerston North, New Zealand, to study the effects of condensed tannins (CT) in Lotus corniculatus (birdsfoot trefoil; cv. Grasslands Goldie) upon the lactation performance of ewes rearing twin lambs. Effects of CT were evaluated by studying the responses of ewes to twice daily oral supplementation with polyethylene glycol (PEG; MW 3500), which binds and inactivates CT. A rotational grazing system with restricted feed allowance was used. Measurements were made of pre-and post-grazing herbage mass, the composition of the feed on offer and diet selected, voluntary feed intake (VF1), milk yield and composition, liveweight gain and wool production. The concentration of metabolites in rumen fluid and in blood plasma was also measured. Lotus contained 35-5 g total nitrogen and 44-5 g total CT/kg dry matter in the diet selected, with an in vitro digestibility of 73%. At peak lactation (weeks 3 and 4) milk yield and composition were similar for control (CT-acting) and PEG-supplemented (CTinactivated) ewes but, as lactation progressed, the decline in milk production and in the secretion rates of protein and lactose were less for control than for PEG-supplemented ewes. In mid and late lactation (weeks 6-11), control ewes secreted more milk (21 %), more milk protein (14%) and more lactose (12%) than PEG-supplemented ewes. Milk fat percentage was lower for control than for PEG-supplemented ewes, but secretion rates of fat were similar for the two groups. VFI, liveweight gain and wool growth were similar for both groups. Plasma urea and glucose concentrations were lower for control than for PEG-supplemented ewes, but concentrations of non-esterified fatty acids (NEFA), growth hormone and insulin were similar for the two groups. The concentrations of ammonia and molar proportions of wo-butyric, iso-and /i-valeric acids in rumen fluid were lower for control than for PEG-supplemented ewes; molar proportions of acetic, propionic and H-butyric acids were similar for the two groups. It was concluded that for ewes rearing twin lambs grazing L. corniculatus, the action of CT increased milk yield and the secretion rates of protein and lactose without affecting VFI, thereby increasing the efficiency of milk production. The increased milk production did not appear to be mediated by effects on plasma concentrations of growth hormone or insulin.^~~~--î

Productive and Reproductive Traits of Sheep Fed Acacia saligna Leaves-Based Diets

“…The negative effects of tannin-diets on milk yield and fat content might be due the reduction of feed intake, decreased rate of digestion and development of conditioned aversion [36, 37]. Wang et al reported that tannins from Lotus corniculatus, which contained moderate amounts of CT (44.5 g/kg DM), fed to lactating ewes increased milk yield, lactose and protein content and decreased milk fat as found in the present study [38]. One reason for these effects could be an increase in metabolizable protein supply from the protein binding action of CT because effects of tannins on ruminant productivity depend on the quality and quantity of dietary protein [28].…”

Potential use of Acacia mearnsii condensed tannins to reduce methane emissions and nitrogen excretion from grazing dairy cows

“…However, milk production was negatively affected by supplementation of CT and this would need to be addressed before CT can be recommended as a mitigation strategy for GHG from pastoral dairying. The negative effects of CT on production, especially during the metabolism study, suggest an inadequate dietary CP concentration relative to the astringency of the administered CT. Other studies have shown dietary CT can benefit milk production in cows and sheep fed fresh forages (Wang et al 1996;Woodward et al 2004), but that was not the case in our study.…”

Supplementing lactating dairy cows fed high-quality pasture with black wattle (Acacia mearnsii) tannin

“…The pasture contained 23.9% of the DM, exceeding requirements for milk production, and therefore 0.6% black wattle CT was unlikely to limit amino acid availability for milk production, and when 1.2% CT was given, the detrimental effects on MS production were minor. In contrast, the benefits of CT in L. corniculatus for MS production in cattle (Woodward et al, 1999 and2004) and milk yield in sheep (Wang et al, 1996), suggest Lotus CT had a lower astringency than black wattle, because concentrations were higher in the DM, and dietary CP concentrations were similar (Table 4) to those reported here.…”