Herbage-based Diet Research Articles

PSV-26 Effect of addition of Ascophyllum nodosum and Asparagopsis taxiformis, alone or in combination, to an herbage-based diet on in vitro fermentation in continuous culture

Abstract This study investigated the effect of individual or simultaneous addition of two macroalgae species on in vitro fermentation in continuous culture. Four single-flow continuous culture fermentors were fed an orchardgrass herbage-based (orchardgrass; Dactylis glomerata L.) basal diet and randomly assigned one of four treatments: 1) control (CON), no macroalgae addition; 2) Ascophyllum nodosum dosed at 2.5% dry matter (DM; ASC); 3) Asparagopsis taxiformis dosed at 0.5% DM (ATX); and 4) A. nodosum (2.5% DM) + A. taxiformis (0.5% DM) dosed simultaneously (AS+AT). Four experimental periods were conducted in a randomized block design with 7 d of treatment adaptation and 3 d of sample collection. Fermentors were fed 82 g of DM per day in 4 equal feedings. In the last 3 d of each experimental period, daily samples of total effluent were taken for analyses of ammonia N and volatile fatty acids (VFA). Effluent was composited by fermentor and analyzed for DM, ash, neutral and acid detergent fiber, and crude protein. Purine concentrations of effluent and bacterial isolates were determined to estimate partitioning of N flow into feed, bacterial, and ammonia N fractions. Methane (CH4) emissions were measured in each fermentor every 15 min using a Fourier transform infrared gas analyzer, and pH was recorded every 2 min. Data were analyzed using the MIXED procedure of SAS v 9.4 with pre-planned contrasts comparing each individual macroalgae to CON (CON vs. ASC and CON vs. ATX) and comparing A. taxiformis with and without simultaneous addition of A. nodosum (ATX vs. AS+AT). Significance was declared at P ≤ 0.05 and tendencies at 0.05 < P ≤ 0.10. Nutrient digestibilities, CH4 emissions, pH, and N metabolism variables were not affected (P > 0.10) in ASC compared with CON, but total VFA concentration increased (P < 0.05) by 10%. Contrarily, the ATX diet tended (P = 0.61) to have reduced true organic matter digestibility, reduced (P < 0.05) total VFA concentration by 11%, and reduced (P < 0.05) CH4 production by 99.9% versus CON. Simultaneous the combination of microalgae (AS+AT) did not further reduce (P > 0.10) nutrient digestibility or total VFA concentration compared with ATX, and did not change (P > 0.10) the degree of CH4 inhibition. However, A. nodosum did not mitigate (P > 0.10) any of the negative effects on fermentation associated with A. taxiformis, as nutrient digestibilities and N metabolism variables in AS+AT were also not different (P > 0.10) from ATX. While the macroalgae species, A. nodosum and A. taxiformis, led to different fermentation patterns when added individually to continuous culture fermentors, no negative or positive interactions were observed from their simultaneous addition.

Herbage utilisation method affects rumen fluid and milk fatty acid profile in Holstein and Montbéliarde cows

Compared with maize silage- and concentrate-based diets, herbage-based diets were repeatedly shown to favourably influence the milk fatty acid (FA) profile. However, it is unclear how the herbage feeding mode (grazing vs indoor green-feeding) and conservation (fresh herbage vs hay vs silage) modify the milk FA profile. Therefore, the aim of the present experiment was to investigate the effect of different herbage utilisation methods (including herbage feeding mode and herbage conservation method) on the ruminal biohydrogenation of dietary FA and the consequences on the milk FA composition in cows of two breeds (Holstein and Montbéliarde). Concomitant effects of botanical composition and phenological stage of the herbage on milk FA profile were controlled for by harvesting barn-dried hay and silage simultaneously as first cut from the same ryegrass-dominated grassland in a semi-mountainous region. Seven weeks later, the first regrowth of the same plot was used as fresh herbage, either grazed or fed indoor (indoor green-feeding). Twenty-four Montbéliarde and 24 Holstein cows were randomly allocated to four groups of 12 cows balanced by breed, parity, and milk yield. In a free-stall barn, three groups were given ad libitum access to hay, silage, or fresh herbage, respectively. The fourth group was strip-grazing. All cows were supplemented with 3 kg DM/day of the same energy-rich concentrate. After 2 weeks of adaptation to the forage, samples of forage, concentrate, milk, blood, and rumen fluid were collected. Fatty acid composition of forages, rumen fluid, and milk was analysed by gas chromatography. Haymaking reduced total FA content of the herbage, in particular that of linoleic acid (LA) and α-linolenic acid (ALA). Still, rumen fluid lipids of hay-fed cows had the highest proportion of rumenic acid, LA, ALA, and total polyunsaturated fatty acids (PUFAs). Milk fat from hay-fed cows had the highest proportion of LA, and the apparent transfer rates from feed to milk of LA and ALA were higher in hay-fed cows than in silage-fed cows. The proportion of PUFAs was highest in milk fat from grazing and indoor green-fed Montbéliarde cows and lowest in silage-fed cows of both breeds. In conclusion, the herbage utilisation method affects the ruminal biohydrogenation of LA and ALA, whereby herbage drying particularly increases their transfer from herbage to milk.

Potential of a rumen bolus containing 1,25-dihydroxyvitamin D3 glycosides for the prevention of hypocalcaemia in primiparous and multiparous dairy cows

Periparturient hypocalcaemia is a widespread metabolic disorder in dairy cows. Clinical and subclinical cases occur primarily in multiparous (Multi) cows, but subclinical cases have also been reported in primiparous (Primi) cows. A preventive strategy was investigated by administering the physiologically active vitamin D3 metabolite, 1,25-dihydroxyvitamin D3 (1,25-dihydroxycholecalciferol, 1,25(OH)2D3) as a rumen bolus. The bolus contained tablets of 1,25(OH)2D3 glycoside extract from Solanum glaucophyllum (SGE), releasing SGE over several days. The aim was to study the effect of a bolus containing 0 (C) or 500 µg (SGE) of 1,25(OH)2D3 on 1,25(OH)2D3 and mineral status in periparturient cows up to three weeks into lactation and on colostrum, milk and calves’ blood mineral contents. The bolus was administered three to four days prior to expected calving to Primi and Multi cows fed a herbage-based diet (dietary cation-anion difference of +522 mEq/kg DM). One C or SGE bolus was applied to 12 Primi and 12 Multi cows. Blood was regularly sampled (and selected a posteriori for antepartum samples) in regard to the actual calving day (d0), immediately prior to bolus application and at day −2, 0.5, 1, 1.5, 2, 4, 8, 11, 15, 18 and 22. Additional samples included urine (at bolus application, d0.5 and d2), colostrum, milk samples (weekly) and calves’ blood (d2). Blood serum 1,25(OH)2D3 increased between d0.5 and d2 in Primi-SGE, but remained unchanged in Primi-C, as did parathyroid hormone (PTH) and Ca in all Primi. Urinary Ca of Primi-SGE was increased on d2, indicating regulation of Ca excess. Three Multi-C cows with confirmed clinical hypocalcaemia needed treatment and thus were excluded from the dataset and replaced. Blood serum 1,25(OH)2D3 and PTH increased while Ca dropped by 40% between d0.5 and d2 in Multi-C, whereas 1,25(OH)2D3, Ca and PTH remained unchanged in Multi-SGE. Blood serum carboxyterminal telopeptide of type I collagen was higher in Primi than in Multi and increased with time, except in Primi-C. Mineral contents in colostrum, milk and blood serum of calves were not influenced to a relevant degree. In conclusion, Primi-C did not, in contrast to Multi-C, develop subclinical hypocalcaemia (<2.0 mmol Ca/l). Prevention of hypocalcaemia with one SGE bolus applied three to four days prior to expected calving was successful in maintaining blood Ca within normal range in Multi over the critical first two days and up to the first three weeks of lactation, without any observed detrimental effects on cows or calves.

Postpartal resumption of ovarian activity in dairy cows: Implications for herbage-based feeding systems in Switzerland.

Milk production in Switzerland is mainly based on herbage feeding with little input of concentrates. The present study investigated the effects of a solely herbage-based diet with (C) and without concentrate (nC) supplementation on luteal activity, milk production and metabolic status in 23 multiparous Holstein dairy cows with early or delayed resumption of ovarian cyclicity post partum (pp). Cows were retrospectively assigned either to a group with early (until d 25 pp, EOV) or delayed resumption of ovarian activity (> d 30 pp, DOV), resulting in four subgroups depending on concentrate feeding: DOV-C, DOV-nC, EOV-C, EOV-nC. Milk progesterone (P4) concentration was measured every 3 d, and different metabolites were analyzed in weekly blood samples. Resumption of ovarian activity was detected between d 19 and 25 pp in EOV, and between d 30 and 60 pp in DOV. In DOV-C, resumption of cyclicity tended to start earlier (38.3 ± 1.7 d pp) compared to DOV-nC (45.2 ± 6.3 d pp; P = 0.10). Independent of grouping, the ovarian activity occurred later in cows with greater plasma β-hydroxybutyrate (BHB) concentrations (P 1 ng/mL did not differ between groups (P > 0.05), but milk P4 peaks during the experiment were higher in EOV compared to DOV (P .

Herbage intake and milk production of late-lactation dairy cows offered a second-year chicory crop during summer

Chicory (Cichorum intybus L.) is a summer-active forage herb which has been proposed as an option to increase summer feed supply, increase dry matter intake, nutrient intake, and milk yield from nonirrigated dairy production systems in southern Australia. Dry matter intake, nutrient intake, milk yield, and yield of milk fat and protein of predominantly Holstein-Friesian dairy cows in late lactation consuming 3 herbage-based diets (4 replicates per treatment) were measured. The 3 grazed herbages were second-year chicory (CHIC) and perennial ryegrass (Lolium perenne L.; PRG) monocultures and a mixed sward (~50:50) of chicory and perennial ryegrass (MIX). All diets (CHIC, PRG, and MIX) were supplemented with alfalfa (Medicago sativa L.) hay (5.5kg of DM/cow per day) and an energy-based concentrate pellet (4.0kg of DM/cow per day). There were no significant differences in milk yield (12.0 to 12.6kg/d across the treatments) or the yield of milk fat (539 to 585g/d) and milk protein (433 to 447g/d) between the 3 herbage-based diets. No differences in DMI (17.9 to 19.2kg/d) or estimated metabolizable energy intake (173 to 185MJ/d) were noted between treatments. Estimated metabolizable energy concentrations in the forages on offer were lower in CHIC than PRG (7.6 vs. 8.2MJ/kg of dry matter), but the concentration in consumed herbage was not different (9.1 vs. 9.2MJ/kg of dry matter); as such, potential for increased milk yield in cows offered CHIC was limited. Increased concentration of polyunsaturated fatty acids was observed in chicory herbage compared with perennial ryegrass. This was associated with increased milk conjugated linoleic acid and milk polyunsaturated fatty acids when chicory formed part of the diet (CHIC compared to PRG and MIX). Chicory could be used as an alternative to perennial ryegrass in summer; however, the developmental stage of chicory will influence concentrations of metabolizable energy and neutral detergent fiber and, therefore, intake and milk production responses compared with perennial ryegrass.

Effect of sprouted barley grain supplementation of an herbage-based or haylage-based diet on ruminal fermentation and methane output in continuous culture

A 4-unit dual-flow continuous-culture fermentor system was used to assess the effect of supplementing 7-d sprouted barley (SB) or barley grain (BG) with an herbage-based or haylage-based diet on nutrient digestibility, volatile fatty acid (VFA) profiles, bacterial protein synthesis, and methane (CH4) output. Treatments were randomly assigned to fermentors in a 4×4 Latin square design with a 2×2 factorial arrangement using 7 d for diet adaptation and 3 d for sample collection. Experimental diets were (1) 55.5g of herbage dry matter (DM) + 4.5g of SB DM, (2) 56.0g of herbage DM + 4.0g of BG DM, (3) 55.5g of haylage DM + 4.5g of SB DM, and (4) 56.0g of haylage DM + 4.0g of BG DM. Forages were fed at 0730, 1030, 1400, and 1900h, whereas SB and BG were fed at 0730 and 1400h. Gas samples for CH4 analysis were collected at 0725, 0900, 1000, 1355, 1530, and 1630h on d 8, 9, and 10. Fluid samples were taken once daily on d 8, 9, and 10 for pH measurements and for ammonia-N and VFA analysis and analyzed for DM, organic matter, crude protein, neutral detergent fiber, and acid detergent fiber for determination of nutrient digestibilities and estimation of bacterial protein synthesis. Orthogonal contrasts were used to compare the effect of forage source (haylage vs. herbage), supplement (BG vs. SB), and the forage × supplement interaction. Apparent and true DM and organic matter digestibilities as well as apparent crude protein digestibility were not affected by forage source. However, true DM digestibility was greatest for diets supplemented with SB. Apparent neutral and acid detergent fiber digestibilities of herbage-based diets were higher than haylage-based diets but fiber digestibility was not affected by supplement. Diets supplemented with SB had higher mean and minimum pH than BG; however, maximum pH was not affected by diet. Supplementation with BG produced a greater concentration of total VFA compared with diets supplemented with SB. Haylage-based diets produced greater CH4 output compared with herbage-based diets but supplementation did not affect CH4 output. Efficiency of bacterial protein synthesis was greater for herbage-based diets compared with haylage-based diets, with no effect of supplementation. Overall, supplementation with SB marginally increased true DM digestibility of herbage- and haylage-based diets but did not affect fiber and crude protein digestibilities, CH4 output, and bacterial efficiency, compared with BG.

Milk production and composition of mid-lactation cows consuming perennial ryegrass-and chicory-based diets

Dry matter intakes (DMI), nutrient selection, and milk production responses of dairy cows grazing 3 herbage-based diets offered at 2 allowances were measured. The 2 allowances were 20 (low) and 30 (high) kg of dry matter (DM)/cow per day and these were applied to 3 herbage types: perennial ryegrass (PRG) and chicory (CHIC+) monocultures and a mixed sward of chicory and perennial ryegrass (MIX). The CHIC+ diet was supplemented with alfalfa hay (approximately 2kg of DM/cow per day) to maintain dietary neutral detergent fiber (NDF) concentration and all diets were supplemented with energy-based pellets (6kg of DM/cow per day). Holstein-Friesian dairy cows averaging 136±30 d in milk were allocated to 4 replicates of the 6 treatments using stratified randomization procedures. Cows were adapted to their experimental diets over a 14-d period, with measurements of DMI, milk yield, and composition conducted over the following 10 d. Herbage DMI was lowest (12.8 vs. 14.0kg of DM/d) for CHIC+ compared with the MIX and PRG, although total forage intake (grazed herbage plus hay) was similar (14.0 to 15.0kg of DM/d) across the 3 treatments. Milk production, milk protein, and milk fat concentrations were not different between herbage types. Grazed herbage DMI increased with increasing herbage allowance and this was associated with increased milk protein concentration (3.23 to 3.34%) and total casein production (41.7 to 43.6mg/g). Concentrations of polyunsaturated fatty acids in milk fat, particularly linoleic acid, were increased in milk from cows offered the CHIC+ or the MIX diets, indicating potential benefits of chicory herbage on milk fatty acid concentrations. Although feeding CHIC+ or MIX did not increase milk yield, these herbage types could be used as an alternative to perennial ryegrass pasture in spring.

Influence of different production strategies on the stability of color, oxygen consumption and metmyoglobin reducing activity of meat from Ningxia Tan sheep

Fifty male Ningxia Tan sheep were randomly divided into five groups (10 per group). Different feeding strategies were applied to each group for 120days prior to slaughter. The sheep belong to five groups were pastured for 0h (feedlot-fed), 2h, 4h, 8h, 12h per day on a natural grazing ground, respectively. M. semitendinosus muscle from Tan sheep was obtained after slaughter. Instrumental color, pH values, oxygen consumption rate, metmyoglobin reducing activity and relative metmyoglobin percentages were analyzed after 1, 3, 5, 7 and 9days of refrigerated storage. Long-term daily grazing and herbage-based diet were conducive to maintain a lower oxygen consumption rate, higher metmyoglobin reducing activity and lower metmyoglobin accumulation. The combination of pasture-fed and feedlot-fed was conducive to weight gain, and at the same time, increased the color stability of the meat from Ningxia Tan sheep.

Effect of supplementing orchardgrass herbage with a total mixed ration or flaxseed on fermentation profile and bacterial protein synthesis in continuous culture

A 4-unit dual-flow continuous culture fermentor system was used to evaluate the effects of supplementing fresh herbage with a total mixed ration (TMR) or flaxseed on nutrient digestibility, fermentation profile, and bacterial N synthesis. Diets were randomly assigned to fermentors in a 4×4 Latin square design. Each fermentor was fed a total of 70g of dry matter/d of 1 of 4 diets: (1) 100% freeze-dried orchardgrass herbage (Dactylis glomerata L.; HERB), (2) 100% freeze-dried TMR (100TMR), (3) 50% orchardgrass herbage supplemented with 50% TMR (50TMR), or (4) 90% orchardgrass herbage supplemented with 10% ground flaxseed (Linum usitatissimum L.; FLAX). Preplanned, single degree of freedom orthogonal contrasts were constructed to assess the effects of feeding system (HERB vs. 100TMR), herbage supplementation (HERB vs. 50TMR + FLAX), and herbage supplemental source (50TMR vs. FLAX). Compared with the HERB diet, the 100TMR diet significantly reduced apparent digestibility of neutral detergent fiber. Herbage supplementation with 50TMR or FLAX significantly reduced or tended to reduce apparent digestibilities of dry matter, organic matter, and neutral detergent fiber, suggesting that replacing high-quality, highly digestible fresh herbage with forage TMR likely caused depressions in nutrient digestibilities. Concentration of total volatile fatty acids, molar proportions of acetate, propionate, and isovalerate, as well as the acetate:propionate ratios were all significantly higher in fermentors fed 100TMR compared with HERB, likely in response to enhanced supply of fermentable energy. In general, feeding system, herbage supplementation, and type of supplementation did not affect N metabolism in the present study. The few significant changes in N metabolism (e.g., flows of total N and non-NH3-N) were primarily linked to increased fermentor N supply with feeding herbage-based diets (HERB and FLAX). Although TMR-based diets decreased nutrient digestibility slightly, TMR offered advantages in bacterial fermentation in relation to volatile fatty acid production, which could potentially translate into better animal performance. Flaxseed shows promise as an alternative supplement for herbage-based diets; however, further in vivo evaluation is needed to determine the optimal level to optimize animal production while reducing feed costs.

Short communication: Effect of oilseed supplementation of an herbage diet on ruminal fermentation in continuous culture

A 4-unit continuous culture fermentor system was used to evaluate the effects of oilseed supplementation of an herbage-based diet on nutrient digestibility, fermentation profile, and bacterial nitrogen (N) synthesis. Treatments were randomly assigned to fermentors in a 4×4 Latin square design with 7d for diet adaptation and 3d for data and sample collection. Dietary treatments were an herbage-only diet (HERB), or the following ground oilseeds supplemented to an herbage-based diet at 10% of total dry matter (DM) fed: flaxseed (FLAX), canola (CAN), or sunflower (SUN). Apparent DM, organic matter, and neutral detergent fiber digestibility were not affected by diet, averaging 62, 68, and 78%, respectively. True DM and organic matter digestibility were not affected by diet, averaging 78 and 82%, respectively. Fermentor pH and total volatile fatty acids were not affected by diet. Branched-chain volatile fatty acids tended to be lower for HERB compared with the 3 oilseed diets. Ammonia N concentrations were lowest for the HERB diet. Crude protein digestibility was not affected by diet. Flow of NH3-N was lowest for the HERB diet reflecting the lowest culture concentration of NH3-N. Bacterial N flows were lowest for HERB and SUN diets, intermediate for FLAX, and greatest for CAN. Flows of total N, non-NH3-N, and dietary N were not affected by diet. Likewise, efficiency of bacterial N synthesis was not affected by diet. Supplementation with FLAX, CAN, or SUN at 10% of total DM fed did not affect nutrient digestibility or ruminal fermentation compared with an all-herbage diet. The oilseeds tested herein may be considered as alternative energy supplements for grazing dairy cows, particularly during times of low availability of corn. However, in vivo studies are needed to further evaluate the effects of oilseeds supplementation of an herbage-based diet on milk production and composition (specifically human-beneficial fatty acids).

Energy partitioning in herbage-fed dairy cows offered supplementary grain during an extended lactation

An experiment was conducted to quantify the changes in energy partitioning resulting from grain supplementation in herbage-fed dairy cows at 4 stages during a 670-d lactation. The experiment used 16 lactating Holstein-Friesian cows, with a control and a grain treatment being randomly allocated to 8 cows each. During 4 measurement periods (each of 4d in a metabolism stall and 3d in an indirect calorimeter) beginning at approximately 110, 270, 450, and 560d in milk (DIM), the energy balance of each cow was measured. Cows in both groups were individually offered freshly cut ryegrass pasture (Lolium hybridum L.) in periods 1 and 3 and ryegrass pasture silage and alfalfa (Medicago sativa L.) hay in periods 2 and 4. In all periods, cows in the grain group were offered an additional 4.4 to 5.0kg of dry matter of cereal grain/cow per day. Adding grain to the diet increased yields of fat and protein and tended to increase yields of milk and lactose, but did not affect milk composition. Gross energy intake (GEI) declined as lactation progressed. Adding grain to the diet decreased the percentage of GEI in feces and urine, but the extent of these reductions did not change as lactation progressed. Adding grain to the diet similarly reduced the percentage of GEI lost to heat, but again the extent of the reduction remained similar as lactation progressed. The magnitude of the increase in milk energy resulting from grain supplementation did not change with advancing lactation, but tissue energy retention was greater in the first 300 DIM compared with after 300 DIM. For herbage-based diets, CH4 emissions ranged from 6.2 to 7.6% of GEI, which corresponds to 24.0 to 25.8g of CH4/kg of dry matter intake. For diets supplemented with cereal grains, CH4 emissions ranged from 6.3 to 7.3% of GEI, which corresponds to 21.6 to 25.2g of CH4/kg of dry matter intake. It was concluded that, for cows producing <24kg of milk/d and consuming herbage-based diets supplemented with grain, the efficiency of utilizing the additional energy in the grain, as measured by the loss of energy in heat, and its partitioning to milk, did not change as lactation progressed from 110 to 560 DIM.

Effect of incremental flaxseed supplementation of an herbage diet on methane output and ruminal fermentation in continuous culture

A 4-unit dual-flow continuous culture fermentor system was used to assess the effect of increasing flaxseed (Linum usitatissimum) supplementation of an herbage-based diet on nutrient digestibility, microbial N synthesis, and methane (CH4) output. Treatments were randomly assigned to fermentors in a 4×4 Latin square design, with 7d for diet adaptation and 3d for data and sample collection. Treatments were 0, 5, 10, and 15% ground flaxseed supplementation of an orchardgrass (Dactylis glomerata L.) diet [70g of total dry matter (DM) fed daily]. Samples were collected from the fermentors 4 times daily at feeding (0730, 1030, 1400, and 1900h) on d 8 to 10 of each of four 10-d periods and analyzed for pH, ammonia-N, and volatile fatty acids. Gas samples for CH4 analysis were collected immediately before and 1 and 2h after the 0730h feeding on d 8, 9, and 10 and at the 1400h feeding on d 7, 8, and 9 of each period. Effluents were analyzed for DM, organic matter, crude protein, and neutral detergent fiber for determination of nutrient digestibilities, and for total purine concentration for estimation of microbial protein synthesis. Apparent DM, organic matter, and neutral detergent fiber digestibilities decreased linearly with increasing supplemental flaxseed, whereas true DM and organic matter digestibilities were not significantly affected by treatment, averaging 77.6 and 79.1%, respectively. Mean ruminal pH and concentration of total volatile fatty acids were not significantly affected by increasing the dietary concentration of flaxseed, averaging 6.68 and 55.9mmol/L across treatments, respectively. However, molar proportions of acetate and propionate increased linearly, whereas those of butyrate and valerate decreased linearly with increasing flaxseed supplementation. Although CH4 output decreased linearly as supplemental flaxseed increased from 0 to 15% of diet DM, ammonia-N concentration, apparent crude protein digestibility, and microbial N synthesis did not differ across treatments. Incremental ground flaxseed supplementation of an herbage-based diet resulted in a corresponding decrease in CH4 output in a dual-flow continuous culture fermentor system. However, apparent nutrient digestibility also decreased with flaxseed supplementation, which, at the cow level, could result in decreased DM intake, milk production, or both.

Metabolic fate of fatty acids involved in ruminal biohydrogenation in sheep fed concentrate or herbage with or without tannins1

A 2 x 2 factorial experiment was carried out to evaluate the effect of herbage or concentrate feeding and dietary tannin supplementation on fatty acid metabolism and composition in sheep ruminal fluid, plasma, and intramuscular fat. Twenty-eight male lambs were divided into 2 equal groups at 45 d of age and kept in individual pens. One group was given exclusively fresh herbage (vetch), and the other group was fed a concentrate-based diet. Within each treatment, one-half of the lambs received supplementation of quebracho powder, providing 4.0% of dietary DM as tannins. Before slaughter, blood samples were collected. The animals were slaughtered at 105 d of age, and ruminal contents and LM were collected. Blood plasma, ruminal fluid, and LM fatty acid composition was determined by gas chromatography. Tannin supplementation reduced (P < 0.05) the concentration of stearic acid (-49%) and increased the concentration of vaccenic acid (+97%) in ruminal fluid from concentrate-fed lambs. Within concentrate- and herbage-based diets, tannin supplementation reduced the accumulation of SFA in blood (P < 0.05) compared with lambs fed the tannin-free diets. When tannins were included in the concentrate, the LM contained 2-fold greater concentrations of rumenic acid compared with the LM of the lambs fed the tannin-free concentrate (0.96 vs. 0.46% of total extracted fatty acids, respectively; P < 0.05). The concentration of PUFA was greater (P < 0.05) and SFA (P < 0.01) less in the LM from lambs fed the tannin-containing diets as compared with the animals receiving the tannin-free diets. These results confirm, in vivo, that tannins reduce ruminal biohydrogenation, as previously reported in vitro. This implies that tannin supplementation could be a useful strategy to increase the rumenic acid and PUFA content and to reduce the SFA in ruminant meats. However, the correct dietary concentration of tannins should be carefully chosen to avoid negative effects on DMI and animal performance.

Δ 9 desaturase protein expression and fatty acid composition of longissimus dorsi muscle in lambs fed green herbage or concentrate with or without added tannins

The aims of this study were to investigate the effect of feeding system and of supplementation of tannins (8.93% DM) on the relationship between intramuscular fat content, fatty acid composition and Δ 9desaturase (Δ 9d) protein expression in longissimus dorsi muscle of lamb. Twenty-eight Comisana lambs (age 45 days) were fed either vetch ( Vicia sativa) or concentrate. The herbage diet was (i) lower in saturated fatty acids (especially in C16:0), C18:1 n−9 and in C18:2 n−6; (ii) higher in C16:1 and C18:3 n−3 when compared to concentrate. Within each feeding system the lambs were divided into two sub-groups, one of which received the diet without tannins supplementation, and the other was fed the diets supplemented with the tannins from Quebracho ( Schinopsis lorentzii). The animals were slaughtered at age 105 days. The concentrate feeding system increased ( p < 0.01) the total intramuscular fat content and the amount of SFA, MUFA and n−6 PUFA and decreased the level of n−3 PUFA ( p = 0.05) when compared to the vetch-fed animals but did not affect Δ 9 desaturase protein expression. There was no correlation between Δ 9d protein expression and total intramuscular fatty acids, CLA and MUFA level. It was suggested that in ruminants, in contrast to monogastric animals, Δ 9d expression does not play the key role in intramuscular fatty acids formation. Tannins supplementation resulted in higher ( p < 0.05) muscle levels of transC18:1 and C18:2 n−6. It has also increased Δ 9d expression in the case of herbage-based diet but not in the case of concentrate-based diet. The mechanism of tannins action on the enzyme expression needs to be elucidated.

Lipid and colour stability of meat from lambs fed fresh herbage or concentrate

Fourteen male Comisana lambs were divided into two groups at 45 days of age and were individually penned for 105 days. Over this period, seven lambs were fed a concentrate-based diet (C), whereas the remaining animals received vetch ( Vicia sativa; H) harvested daily and given fresh to the animals. Lipid oxidation was measured in both minced cooked meat ( semimembranosus muscle, SM) over 4 days of aerobic refrigerated storage and on minced raw meat stored over 14 days in a high oxygen atmosphere. Colour descriptors, haem pigment concentration, and metmyoglobin percentages were also determined during storage duration on the minced raw meat. Lipid oxidation increased over time in cooked and raw meat ( P < 0.0005), but lower TBARS values were found in both cooked and minced meat from lambs fed vetch compared to those given concentrates ( P = 0.001; P = 0.006, respectively). Higher a* values, lower b* values and lower hue angle values were observed in meat from H-fed animals as compared to meat from C-fed lambs ( P = 0.006; P = 0.02; P = 0.005, respectively). Metmyoglobin formation increased over time ( P < 0.0005), but the H diet resulted in lower metmyoglobin percentages than the C diet ( P = 0.006). Haem pigment concentration decreased over the 14 days of storage ( P < 0.0005). We conclude that, under conditions that promote oxidative stress in meat, a herbage-based diet can improve the oxidative stability of meat compared to a concentrate-based diet.

Effects of nutrition and management on the production and composition of milk fat and protein: a review

The composition and functional properties of cow’s milk are of considerable importance to the dairy farmer, manufacturer, and consumer. Broadly, there are 3 options for altering the composition and/or functional properties of milk: cow nutrition and management, cow genetics, and dairy manufacturing technologies. This review considers the effects of nutrition and management on the composition and production of milk fat and protein, and the relevance of these effects to the feeding systems used in the Australian dairy industry. Dairy cows on herbage-based diets derive fatty acids for milk fat synthesis from the diet/rumen microorganisms (400–450 g/kg), from adipose tissues (&lt;100 g/kg), and from de novo synthesis in the mammary gland (about 500 g/kg). However, the relative contributions of these sources of fatty acids to milk fat production are highly dependent upon feed intake, diet composition, and stage of lactation. Feed intake, the amount of starch relative to fibre, the amount and composition of long chain fatty acids in the diet, and energy balance are particularly important. Significant differences in these factors exist between pasture-based dairy production systems and those based on total mixed ration, leading to differences in milk fat composition between the two. High intakes of starch are associated with higher levels of de novo synthesis of fat in the mammary gland, resulting in milk fat with a higher concentration of saturated fatty acids. In contrast, higher intakes of polyunsaturated fatty acids from pasture and/or lipid supplements result in higher concentrations of unsaturated fatty acids, particularly oleate, trans-vaccenate, and conjugated linoleic acid (CLA) in milk fat. A decline in milk fat concentration associated with increased feeding with starch-based concentrates can be attributed to changes in the ratios of lipogenic to glucogenic volatile fatty acids produced in the rumen. Milk fat depression, however, is likely the result of increased rates of production of long chain fatty acids containing a trans-10 double bond in the rumen, in particular trans-10 18 : 1 and trans-10-cis-12 18 : 2 in response to diets that contain a high concentration of polyunsaturated fatty acids and/or starch. Low rumen fluid pH can also be a factor. The concentration and composition of protein in milk are largely unresponsive to variation in nutrition and management. Exceptions to this are the effects of very low intakes of metabolisable energy (ME) and/or metabolisable protein (MP) on the concentration of total protein in milk, and the effects of feeding with supplements that contain organic Se on the concentration of Se, as selenoprotein, in milk. In general, the first limitation for the synthesis of milk protein in Australian dairy production systems is availability of ME since pasture usually provides an excess of MP. However, low concentrations of protein in milk produced in Queensland and Western Australia, associated with seasonal variations in the nutritional value of herbage, may be a response to low intakes of both ME and MP. Stage of lactation is important in determining milk protein concentration, but has little influence on protein composition. The exception to this is in very late lactation where stage of lactation and low ME intake can interact to reduce the casein fraction and increase the whey fraction in milk and, consequently, reduce the yield of cheese per unit of milk. Milk and dairy products could also provide significant amounts of Se, as selenoproteins, in human diets. Feeding organic Se supplements to dairy cows grazing pastures that are low in Se may also benefit cow health. Research into targetted feeding strategies that make use of feed supplements including oil seeds, vegetable and fish oils, and organic Se supplements would increase the management options available to dairy farmers for the production of milks that differ in their composition. Given appropriate market signals, milk could be produced with lower concentrations of fat or higher levels of unsaturated fats, including CLA, and/or high concentrations of selenoproteins. This has the potential to allow the farmer to find a higher value market for milk and improve the competitiveness of the dairy manufacturer by enabling better matching of the supply of dairy products to the demands of the market.

Effect of fibrous and starchy carbohydrates in concentrates as supplements in a herbage-based diet for high-yielding dairy cows.

The effects of 2 concentrates composed of different carbohydrate sources (beet pulp vs. maize) on intake, digestibility, yield and composition of milk from high-yielding dairy cows given fresh herbage indoors was investigated. In 1988 two diets and in 1989 three diets were used with 9 cows/diet. In 1989 concentrates were supplied on an equal amount of DM and in 1989 on an equal amount of energy. The animals received the concentrates after milking time. In 1988 the experimental period lasted 8 wk and in 1989 10 wk. In 1988 intake of herbage DM tended to be higher on the maize-enriched diet, resulting in a significantly (P

The effect of cereal concentrate supplementation on the digestibility of herbage-based diets for lactating dairy cows

SummaryTwo experiments were conducted, one with seven and the other with eight lactating cows, to measure the effect of supplementation with a cereal concentrate on the digestibility of fresh herbage and to provide equations relating digestibility of herbage to faecal indicators. Cattle were housed with free access to fresh herbage from individual Calan–Broadbent gates for recording feed intake, and faecal output was estimated by the use of chromic oxide. In both experiments a cereal supplement depressed herbage organic matter digestibility by 8 g/kg for each kg of fresh concentrate provided within the range 1–6 kg. The depression was associated with reduced digestibility of cellulose. Herbage digestibility was significantly related to faecal nitrogen and faecal cellulose. Herbage intake was depressed by concentrate supplementation and the response in milk yield to supplementation was small.