Pasture Allowance Research Articles

Early mother–young relationship and feeding behaviour of lambs are unaffected by low pasture allowance until the beginning of the last third of gestation in single-bearing ewes

Nutrition during gestation influences ewes’ bodyweight (BW), the bond with their lamb, milk yield and lamb development, and thus feeding behaviour of lambs during postnatal rearing. The aim of this study was to determine if the level of native pasture allowance from before conception until the beginning of the last third of gestation of single-bearing ewes influences the ewe–lamb relationship at birth and the feeding behaviour of lambs during postnatal rearing. A second aim was to determine whether the nutritional treatments affect ewes’ milk yield and their lambs’ bodyweight. Eleven multiparous Corriedale ewes grazed a high pasture allowance [10–12 kg of dry matter (DM)/100 kg of BW/day; HPA treatment], and another 11 grazed a low pasture allowance (5–8 kg of DM/100 kg of BW/day; LPA treatment) for 145 days beginning 40 days before conception. After the end of this treatment all ewes grazed on Festuca arundinacea and received rice bran and crude glycerine until 3 days before birth. Ewes’ BW was recorded monthly before and during gestation. Latency from parturition until the ewe licked her lamb, latency for lamb to stand up and suckle were recorded, and Maternal Behaviour Score was determined 12–24 h after birth. All the variables recorded during postpartum were determined approximately every 30 days. Grazing, ruminating and suckling events of the lambs were recorded from Day 23 until 142 days of age. Milk yield was determined from 32 until 140 days after lambing. Lambs’ BW was recorded from birth until 140 days of age. On Day 41 the BW change tended to be greater in HPA ewes than in LPA ewes, and on Days 79 and 105 it was greater in HPA ewes than LPA ewes (P = 0.006 and P = 0.005 respectively). Treatments did not affect the behaviours at birth of ewes and lambs, milk yield, ruminating and suckling events of lambs, ewes’ and lambs’ BW. The lambs from HPA ewes tended to present a greater frequency of grazing than the LPA lambs. Different levels of native pasture allowances from before conception until the last third of gestation in single-bearing ewes, followed by an increase in nutrient supply, did not affect ewe–lamb behaviours at birth, milk yield, lambs’ growth, and their feeding behaviours during rearing.

Effects of pasture allowance on milk production of dairy cows offered increasing amounts of partial mixed rations in spring

Milk production was measured in Holstein–Friesian cows offered low, medium or high allowances of ryegrass pasture (15, 25 or 40 kg DM/cow.day to ground level) and receiving different amounts of supplement (6, 10, 12 or 14 kg DM/cow.day) as a partial mixed ration (PMR). The 27-day experiment was conducted in spring when cows were 45 ± 17.3 days in milk (mean ± s.d.). Two groups of six cows received each of the 12 combinations of pasture allowance and PMR amount. The PMR comprised wheat grain (38%, DM basis), maize grain (18%), lucerne hay (22%) and canola meal (22%). When 6 kg DM PMR/cow.day was offered, cows grazing the low allowance produced less milk and energy-corrected milk than did cows grazing the medium and high allowances. There was no effect of pasture allowance on production of milk or energy-corrected milk at any other amount of PMR offered. When cows were offered 14 kg DM PMR/cow.day, milk fat concentrations were lower for cows grazing the high pasture allowance than for cows grazing the medium allowance. There were no differences in milk fat concentrations between cows grazing the different pasture allowances at any other amount of PMR offered. When cows were offered 6 kg DM PMR/cow.day, cows grazing the low pasture allowance yielded less milk fat than did cows grazing the medium pasture allowance. Cows grazing the high allowance had greater concentrations and yields of milk protein than did cows grazing the low allowance at all amounts of PMR offered, while cows grazing the medium allowance yielded more milk protein at some amounts of PMR. Pasture utilisation decreased with increases in both pasture allowance and amount of PMR. These results will enable farmers to better optimise feeding systems that combine both pasture and PMR.

Low pasture allowance until late gestation in ewes: behavioural and physiological changes in ewes and lambs from lambing to weaning

Low pasture allowance during gestation affects ewes’ BW at parturition, the bond with their lamb, lamb development, and thus also may affect their responses to weaning. The objectives were to determine if native pasture allowance from before conception until late pregnancy affects ewe–lamb behaviours at lambing, ewes’ milk yield, lambs’ BW, and the behavioural and physiological changes of ewes and lambs at weaning. From 23 days before conception until 122 days of pregnancy, 24 ewes grazed on two different native pasture allowances: high (10 to 12 kg of dry matter (DM)/100 kg of BW per day; HPA treatment; n=12) or low (5 to 8 kg of DM/100 kg of BW per day; LPA treatment; n=12). Thereafter, all ewes grazed on Festuca arundinacea and received rice bran and crude glycerine. Ewes’ body condition score (BCS) and BW were recorded during pregnancy and postpartum periods. Milk yield was determined on days 32, 41 and 54 after lambing. Lambs’ BW was recorded from birth until 72 days after lambing. Latency from parturition until the ewe licked her lamb, maternal behaviour score (a test that evaluates maternal attachment to the lamb) and latency for lamb to stand up and suckle were determined. The behaviour of the lambs and ewes was recorded before and after weaning (at 65 days). The ewes’ serum total protein, albumin and globulin concentrations were measured before and after weaning. The HPA ewes presented greater BW (P<0.005) and BCS (P<0.005) than the LPA ewes during pregnancy and postpartum (P<0.04), and had a greater milk yield than the LPA ewes (P<0.03). Treatments did not influence any behaviour at lambing, lambs’ BW, neither the ewes’ behavioural and physiological changes at weaning. HPA lambs paced and vocalized more than LPA lambs (P<0.0001). The variation of albumin concentration before and after weaning was greater in the HPA lambs than in the LPA lambs (P<0.0001). In conclusion, although ewes’ BW, BCS and milk production were affected by pasture allowance until late pregnancy, this did not affect the behaviours that lead to the establishment of the mother–young bond, nor the ewes’ behavioural responses at weaning. Lambs reared by ewes that grazed on low pasture allowance during pregnancy presented fewer behavioural changes and a lower decrease of albumin concentration after weaning. Lambs’ BW was not affected by the feeding received by their mothers.

Dry matter intake and feeding behaviour of grazing dairy cows offered a mixed ration with or without canola meal

Dry matter intake and feeding behaviour were measured in grazing dairy cows fed partial mixed rations with (PMR+C) and without (PMR–C) canola meal. In spring (early lactation), 32 Holstein–Friesian dairy cows were offered two amounts of the two supplement treatments in a two × two factorial arrangement of treatments for 24 days. Amounts of supplement were low (8 kg DM/cow.day) versus high (14 kg DM/cow.day). The PMR–C ration comprised wheat grain (59.5%, DM basis), maize grain (18.9%) and lucerne hay (21.6%). The PMR+C ration was the same, except some wheat grain was substituted with canola meal (21.6%). Both rations were isoenergetic, with a grain to forage ratio of 78 : 22 (DM basis). All cows were offered a low pasture allowance of 10 kg DM/cow.day to ground level. Replacing some wheat in a ration with canola meal increased pasture and total eating time. Dry matter intake did not differ between PMR–C and PMR+C cows. The present experiment also demonstrated that altering the amount of supplement did not influence the increase in eating time that occurred as a result of the inclusion of canola meal. Increasing the amount of supplement reduced pasture intake as a result of a reduction in grazing time and grazing intensity.

Individualised feeding of concentrate supplement in pasture-based dairy systems: practices and perceptions of New Zealand dairy farmers and their advisors

Approximately one-third of New Zealand dairy farms have in-shed feeding systems, and quarter of these systems have individual-cow feeding capability. There is little information about the factors motivating farmers to install individualised feeding technology in New Zealand and their management practices. A survey was conducted of 42 farmers using individualised feeding, followed by interviews of 32 farmers and five farm consultants. The aim of the study was to understand why farmers were installing individualised feeding, how they were using it, and what challenges they were facing. Results indicated that these farmers were commonly motivated by improving productivity and most farmers strongly believed that they were gaining value with this approach compared with flat-rate feeding. However, there was also uncertainty about the most profitable feeding strategies. The farmers were most commonly feeding cows in distinct groups rather than as individuals, and were typically adjusting feed allocation at three to four stages of the lactation. Consultants identified a lack of a value proposition for investment, limited justification for feeding-decision rules, and the absence of information to support the perceived productivity (and other) benefits. The perceived productivity benefit of individualised feeding held by farmers in the present study is contrary to recent research that has indicated no marginal milk-production benefit compared with flat-rate feeding. Although, few of these studies relate to individualised feeding in grazing systems where pasture allowance is restricted as is typical of New Zealand farm systems, indicating a need for further experimental and modelling research to quantify the potential value in these systems. Farmers were seeking reliable information on the response rate and cost effectiveness of various feeds and feeding rules, how to distribute a fixed amount of feed to the herd most profitably, and technical expertise, support and back-up for specific feeding systems. Findings from the present study suggest a lack of advisor expertise related to in-shed feeding of concentrate supplement in pasture-grazed systems, signalling opportunities for more training of rural professionals to provide informed advice and improved communication channels with farmers.

Analysis of pasture supplementation strategies by means of a mechanistic model of ruminal digestion and metabolism in the dairy cow

Effective pasture supplementation is critical to the efficiency of resource management in milk production. We understand a great deal about ruminal and metabolic processes in dairy cattle that control efficiency but we need to improve our ability to predict effects of practical feeding strategies based on the basic biological processes of the cow. Therefore, a large-scale pasture supplementation study was used to explore the details of both practical management and the underlying biological principles and processes involved. This included a multiple lactation study coupled with shorter-term experiments that tested the type and rate of supplementation. Basal supplementation strategies were (1) pasture allowance [14 kg of dry matter (DM)/d per cow] supplemented with milled barley grain fed twice daily in the milking parlor and pasture silage provided in the paddock; the ratio of grain:forage fed as supplement was 0.75:0.25 (control; DM basis); (2) the same pasture allowance plus the same amounts of milled barley grain and pasture silage, but the supplements were mixed and chopped before being fed immediately after each milking; and (3) the same pasture allowance and offered a partial mixed ration comprising barley (25%) and corn grain (30% of DM), corn silage (20% of DM), and alfalfa hay (25% of DM) after each milking. In late lactation (227 d in milk), a short-term experiment was done feeding the same pasture allowances but with the 3 supplements offered at 6, 8, 10, and 12 kg of DM/d for an 11-d measurement period following adaptation to the diet to each of the 3 long-term supplementation groups. Production responses were recorded and ruminal volatile fatty acids (VFA) and pH were measured in a subset of animals. Model descriptions of yields of milk and milk constituents as well as mean concentrations of ruminal fluid VFA and ruminal fluid pH were compared with measured values resulting when dairy cows were fed 12 different pasture-based diets with different levels and types of dietary supplement. Inputs into the model were measured dry matter intake and feed composition on the 12 combined treatments as well as initial body weight and composition. The model described milk and milk component production within 1 standard deviation of the treatment means (less than 5% of the mean as measured in the root mean square error). The simulated proportions of ruminal acetate, propionate, and butyrate were consistent with observed effects of supplemental treatments and rate of supplementation; however, the error analysis showed room for improvement. The model described, to a general extent, the changes in ruminal pH; however, this investigation showed that the equations that describe ruminal pH need to be improved or modified. These results show that the fundamental knowledge of ruminal and organ metabolism in this mechanistic model is sufficient to describe the qualitative responses to complicated dietary strategies, but our quantitative understanding of the parameters involved such as degradation and absorption kinetics and ruminal pH still demands more specific research.

Evaluation of blood metabolites in dairy cows grazing under two pasture allowances and supplemented with corn silage under restricted grazing conditions

This study was conducted to evaluate the influence of management tools - daily pasture allowance and corn silage supplementation - during periods of forage shortage on the metabolism of dairy cows grazing low-mass pasture in temperate regions. Forty lactating Holstein cows were used during an experimental period of seventy days (April 15 to June 23, 2012). Blood metabolites and milk production were determined in fall-calving dairy cows grazing under two daily pasture allowances (PA) (moderate, 17 kg vs. high, 25 kg dry matter (DM)) and supplemented with corn silage (CS) (low, 4.5 kg vs. high, 9.0 kg DM). All cows received 3 kg DM of concentrate. Plasma concentrations of β-hydroxybutyrate (BHBA), non-esterified fatty acids (NEFA), and urea were determined using an automated spectrophotometer, and milk production was electronically measured at each milking time during the trial. The experimental design was completely randomized using a 2 × 2 factorial arrangement of treatments. The increase in daily PA decreased plasma concentrations of BHBA (0.91±0.36 vs. 1.12±0.43 mmol L−1), provided an increase in milk yield (23.18±3.26 vs. 21.99±3.37 kg d−1), and did not modify the concentrations of NEFA and urea. The increased CS supplementation increased mildly the plasma concentrations of BHBA (1.07±0.36 vs. 0.96±0.44 mmol L−1) and NEFA (92.77±54.14 vs. 92.77±55.31 µmol L−1), and decreased the concentrations of urea (4.08±1.40 vs. 4.64±1.30 mmol L−1), but did not change milk production. The positive effect of increasing PA was associated with a high herbage intake, while the lack of response to increasing CS supplementation was attributed to a high substitution of pasture intake (0.9 kg DM pasture/kg DM CS). Low corn silage supplementation is recommended.

Variation in feeding behavior and milk production among dairy cows when supplemented with 2 amounts of mixed ration in combination with 2 amounts of pasture

Variation in feeding behavior and milk production of grazing dairy cows fed a mixed ration was measured. Experiments were conducted in spring (early lactation) and autumn (late lactation) with 48 Holstein-Friesian dairy cows. Pasture allowance (low vs. high) and amounts of supplement (low vs. high) were applied to determine the effect on variation among cows in feeding behavior and milk production. The experiments investigated 4 dietary treatments in a 2×2 factorial arrangement of treatments. Daily pasture allowances were 15kg of DM/cow per day (low) and 37kg of DM/cow per day (high; to ground level); and 12kg of DM/cow per day (low) and 31kg of DM/cow per day (high; to ground level), for the spring and autumn experiments, respectively. Supplements were offered at 6kg of DM/cow per day (low) and 14kg of DM/cow per day (high); and 6kg of DM/cow per day (low) and 12kg of DM/cow per day (high), for the spring and autumn experiments, respectively. There were 2groups of 6 cows per treatment. All treatments received a partial mixed ration, defined as a total mixed ration fed between periods of grazing that contained wheat grain, corn grain, alfalfa hay, and canola meal. The grain-to-forage ratio of the supplements was 78:22 (DM basis) in both spring and autumn. In both experiments, the pre-experimental period was 14d followed by a 10-d experimental period. The variation among cows within a group in feeding behavior was influenced by the amount of supplement but not the amount of pasture offered. The variation among cows in pasture eating time approximately doubled when the amount of supplement offered increased, indicating that to reduce the variability among cows, supplement feeding management strategies need to be considered. Increasing pasture allowance had no effect on pasture eating time although pasture intake increased as a result of increased grazing intensity compared with the low pasture allowance. However, increasing the amount of supplement in the partial mixed ration feeding system reduced pasture eating time by 51min/cow per day.

Pasture intake and milk production of dairy cows rotationally grazing on multi-species swards

Increasing plant species diversity has been proposed as a means for enhancing annual pasture productivity and decreasing seasonal variability of pasture production facing more frequent drought scenarios due to climate change. Few studies have examined how botanical complexity of sown swards affects cow performance. A 2-year experiment was conducted to determine how sward botanical complexity, from a monoculture of ryegrass to multi-species swards (MSS) (grasses-legumes-forb), affect pasture chemical composition and nutritive value, pasture dry matter (DM) intake, milk production and milk solids production of grazing dairy cows. Five sward species: perennial ryegrass (L as Lolium), white clover and red clover (both referred to as T as Trifolium because they were always sown together), chicory (C as Cichorium) and tall fescue (F as Festuca) were assigned to four grazing treatments by combining one (L), three (LT), four (LTC) or five (LTCF) species. Hereafter, the LT swards are called mixed swards as a single combination of ryegrass and clovers, whereas LTC and LTCF swards are called MSS as a combination of at least four species from three botanical families. The experimental area (8.7 ha) was divided into four block replicates with a mineral nitrogen fertilisation of 75 kg N/ha per year for each treatment. In total, 13 grazing rotations were carried out by applying the same grazing calendar and the same pasture allowance of 19 kg DM/cow per day above 4 cm for all treatments. Clover represented 20% of DM for mixed and MSS swards; chicory represented 30% of DM for MSS and tall fescue represented 10% of DM for LTCF swards. Higher milk production (+1.1 kg/day) and milk solids production (+0.08 kg/day) were observed for mixed swards than for ryegrass swards. Pasture nutritive value and pasture DM intake were unaffected by the inclusion of clover. Pasture DM, organic matter and NDF concentrations were lower for MSS than for mixed swards. Higher milk production (+0.8 kg/day), milk solids production (+0.04 kg/day) and pasture DM intake (+1.5 kg DM/day) were observed for MSS than for mixed swards. These positive effects of MSS were observed for all seasons, but particularly during summer where chicory proportion was the highest. In conclusion, advantages of grazing MSS on cow performance were due to the cumulative effect of improved pasture nutritive value and increased pasture DM intake that raised milk production and milk solids production.

Key pasture and milksolids production indicators from two Waikato farmlets differing in inputs, stocking rate, pasture allowance and nitrate leaching

Two DairyNZ farmlets, differing in nitrogen fertiliser inputs, cow genetic merit and autumn/winter grazing management, with stocking rates of 2.6 ('Future') and 3.2 ('Current') cows/ha, were compared for pasture residual and quality over 4 years. Target intakes for lactating cows were 18 and 16 kg DM/cow/day, respectively, with target grazing residuals of 3.5-4 cm (1500 kg DM/ha in late winter/spring, 7-8 clicks on the rising plate meter) for both herds. Measurement of grazing residuals, pasture quality and botanical composition identified small differences between farmlets. Grazing residuals on the Future farmlet averaged 0.2 cm (0.4 clicks on rising plate meter, RPM) (P

Milk production responses to different strategies for feeding supplements to grazing dairy cows

Milk production responses of grazing cows offered supplements in different ways were measured. Holstein-Friesian cows, averaging 45d in milk, were allocated into 8 groups of 24, with 2 groups randomly assigned to each of 4 feeding strategies. These were control: cows grazed a restricted allowance of perennial ryegrass pasture supplemented with milled wheat grain fed in the milking parlor and alfalfa hay offered in the paddock; FGM: same pasture and allowance as the control supplemented with a formulated grain mix containing wheat grain, corn grain, and canola meal fed in the parlor and alfalfa hay fed in the paddock; PMRL: same pasture and allowance as the control, supplemented with a PMR consisting of the same FGM but mixed with alfalfa hay and presented on a feed pad after each milking; and PMRH: same PMR fed in the same way as PMRL but with a higher pasture allowance. For all strategies, supplements provided the same metabolizable energy and grain:forage ratio [75:25, dry matter (DM) basis]. Each group of 24 cows was further allocated into 4 groups of 6, which were randomly assigned to receive 8, 12, 14, or 16kg of DM supplement/cow per d. Thus, 2 replicated groups per supplement amount per dietary strategy were used. The experiment had a 14-d adaptation period and a 14-d measurement period. Pasture allowance, measured to ground level, was approximately 14kg of DM/d for control, FGM, and PMRL cows, and 28kg of DM/d for the PMRH cows, and was offered in addition to the supplement. Positive linear responses to increasing amounts of supplement were observed for yield of milk, energy-corrected milk, fat, and protein for cows on all 4 supplement feeding strategies. Production of energy-corrected milk was greatest for PMRH cows, intermediate for FGM and PMRL cows, and lowest for control cows. Some of these differences in milk production related to differences in intake of pasture and supplement. Milk fat concentration decreased with increasing amount of supplement for all feeding strategies, but the decline was most marked for the control cows. Milk protein concentration increased for all groups as the amount of supplement increased, but was greater for FGM, PMRL, and PMRH cows than control cows. It is concluded that when supplements are fed to grazing dairy cows, inclusion of corn grain and canola meal can increase milk production even at similar metabolizable energy intakes, and that it does not matter whether these supplements are fed as a PMR or in the parlor and paddock.

Grazing increases the unsaturated fatty acid concentration of milk from grass‐fed cows: A review of the contributing factors, challenges and future perspectives

Grazing animals walk outdoors and harvest fresh herbage from a three‐dimensional canopy. Botanical composition and grassland management in various farming systems affect herbage intake and milk fatty acid (FA) composition. Grazing animals encounter a vertical gradient while grazing down a sward; responses in milk FA composition are discussed. Grazing animals have diets rich in poly‐unsaturated fatty acids (PUFA), particularly α‐linolenic acid (C18:3n‐3). Concentrates and starch‐rich fodders affect rumen retention time of the feed, increase linoleic acid (C18:2n‐6) intake, and alter biohydrogenation pathways toward less n‐3 PUFA and less rumenic acid (conjugated linoleic acid (CLA) isomer C18:2c9t11), leading to lower contents of these compounds in the milk. Milk from grazing‐based production systems including organic systems, therefore, has less saturated and more n‐3PUFA and CLAc9t11 which is considered beneficial for health. The occurrence of natural trans FA (t11) in milk predominates with grazing whereas intensive feeding practices enhance t10‐FA, with possible negative health effects. FA intake – output relations can differ among plant species due to rapid rumen passage rate or compounds protecting PUFA, resulting in more PUFA in milk. Methodological constraints for FA measurement in herbages are discussed. Trends in grazing and dairy farming systems and implications for milk FA composition are addressed.Practical applications: Grazing is important for fresh forage intake, animal health and natural behaviour, landscape values and grassland biodiversity. Grazing is a political, societal and marketing issue in The Netherlands where retailers since 2011 sell dairy products labelled as “pasture‐milk” and dairies pay a premium to farmers whose cows get access to pasture. Grazing affects green leaf intake because animals can select. Pasture allowance enhances α‐linolenic acid and CLAc9t11 (rumenic acid) concentrations in milk fat. FA need to be designated by unique names; CLA is a generic term and isomers give rise to different biological responses. As some forbs reduce biohydrogenation, grassland species diversity may improve PUFA transfer efficiency from feed to milk. Trends in animal genetics and increased herd size, TMR feeding and automated milking systems cause reduction of grazing in Europe, which can increase saturated and trans‐10 milk FA concentrations and reduce naturally occurring fat‐soluble vitamins and antioxidants in dairy products.Grazing (pasture‐feeding versus indoor with conserved forage and concentrates) increases n‐3 PUFA and trans‐11 over trans‐10 FA in cow milk when cows can select, as leaves have high n‐3 PUFA concentrations; biodiverse grasslands enhance this effect as some forbs show less PUFA rumen biohydrogenation than grasses, thus increasing efficiency of PUFA transfer from forage to milk.

High pasture allowance does not improve animal performance in supplemented dairy cows grazing alfalfa during autumn–winter

The aim of this study was to assess the effect of three alfalfa pasture herbage allowances on milk yield and composition during autumn–winter grazing season on early autumn calving dairy cows. Eighteen multiparous Holstein dairy cows were assigned to one of three treatments in a 3×3 Latin square design: low herbage allowance (14kgDM/cow; LHA), medium herbage allowance (27kgDM/cow; MHA) and high herbage allowance (41kgDM/cow; HHA). Dry matter disappearance was lower at LHA although remained similar between MHA and HHA (P<0.05). However, as herbage allowance (HA) increased, lower grazing efficiencies (as the proportion of material removed) were registered (P<0.05). Total dry matter intake (DMI; kg/d) was also lowest for LHA and similar between the other two treatments (P<0.05). Milk yield, 4%FCM, milk fat (g/kg) and casein (g/kg) tended to increase from LHA to HHA (P<0.10). Cows at LHA tended to loss weight whilst cows at MHA and HHA had a tendency to increase BW according the season progressed (P<0.10). In summary, managing cows at HHA will allow cows to a slightly increase in individual milk production and BW gain but in detriment of herbage utilization and potentially, milk production per hectare.

Mother–young behaviours at lambing in grazing ewes: Effects of lamb sex and food restriction in pregnancy

This study investigated whether the level of pasture allowance from before conception until late pregnancy affects ewe–lamb behaviours at birth, and if those behaviours differ according to the sex of the lambs. We performed two experiments, in which 96 ewes were assigned to one of two nutritional treatments: high native pasture allowance [10–12kg of dry matter/100kg of body weight (BW)/day] or low pasture allowance (5–8kg of dry matter/100kg of BW/day). In Experiment 1, treatments began 23 days before artificial insemination and ended at 122 days of gestation (groups HPA-1, n=38; and LPA-1, n=25 for high and low pasture allowance, respectively), and in Experiment 2, started 40 days before artificial insemination and ended at 105 days of gestation (groups HPA-2, n=22; and LPA-2, n=11 for high and low pasture allowance, respectively). Thereafter, all ewes received rice bran (200g/animal/day) and 50mL of crude glycerine/animal/day. Ewes’ body condition score (BCS) and BW were recorded at lambing. Latency from parturition to licking her lamb, maternal behaviour score (MBS; a test that evaluates maternal attachment to the lamb), lambs’ BW, and latency to stand up and suckle were recorded. In Experiment 1, HPA-1 ewes had greater BCS and BW (2.5±0.04units vs. 2.25±0.05units and 52.7±0.4kg vs. 50.2±0.4kg, respectively; P<0.0001) at lambing, and tended to lick their lambs earlier (1.4±0.3min vs. 1.9±0.3min; P=0.08) than LPA-1 ewes. Male lambs of LPA-1 ewes suckled later than female lambs (73.3±11.7min vs. 43.4±13.1; P=0.02), male (73.3±11.7min vs. 45.5±10.8; P=0.02) and female lambs of HPA-1 ewes (73.3±11.7min vs. 49.4±10.3; P=0.04). In Experiment 2, BCS and BW at birth were similar between HPA-2 and LPA-2 ewes. In addition, behaviours of lambs and ewes, as well as MBS were not affected by nutritional treatment or sex of the lambs, and there was no interaction between nutritional treatment and sex of the lambs. In conclusion, different native pasture allowances from before conception until advanced pregnancy followed by a great increase in nutritional plane during late pregnancy, did not affect ewe–lamb behaviours at lambing. However, slight sex differences were detected when duration of food restriction during gestation was longer.

Limitations and potential for individualised feeding of concentrate supplements to grazing dairy cows

The increasing availability and installation of computerised feeding and milk-monitoring technology in Australia and New Zealand has led to an increased interest in feeding individual cows different amounts and types of supplements over lactation. However, there is confusion about the potential benefits of individualised feeding strategies compared with feeding the same amount of supplement to all cows in the herd on any given day. The majority of bail feeding research conducted over the past 30 years has identified little difference in cow response between flat-rate feeding and more complicated approaches of split feeding or feeding to individual cow milk yield. However, it must be noted that many of these experiments involved animals with ad libitum access to a forage supply. This is an important distinction as individual cows receiving high-quality forage ad libitum would be able to compensate, at least partially, for any shortage in concentrate. Large variability in response to supplements among individual cows within the herd implies that there should be a benefit from individualised bail feeding practices. This review examines the potential for individualised bail feeding in pasture-based dairy systems, considering both system (pasture allowance and type) and cow-level parameters (e.g. dry matter intake, milk yield, genotype, bodyweight, stage of lactation) that could affect the individual cow response to a particular supplement, and discusses the current limitations and future challenges for implementing this technology on farm. Recommendations for future research are made to address any knowledge gaps.

Beef heifer growth and reproductive performance following two levels of pasture allowance during the fall grazing period.

The objective of this study was to compare heifer growth and reproductive performance following 2 levels of stockpiled fall forage allowance of orchardgrass (30.5%) and tall fescue (14.1%). Spring-born heifers (n = 203 and BW = 246 ± 28.9 kg) of primarily Angus background were allocated to 2 grazing treatments during the fall period (November 12 to December 17 in yr 1, November 7 to January 4 in yr 2, and November 7 to January 14 in yr 3) each replicated 3 times per year for 3 yr. Treatments consisted of daily pasture DM allowance of 3.5% of BW (LO) or daily pasture DM allowance of 7.0% of BW (HI) under strip-grazing management. Throughout the winter feeding period, mixed grass-legume haylage and soybean hulls were fed. Heifers were grazed as 1 group under continuous stocking after the winter period. Heifers in the LO group gained less than heifers in the HI group during the fall grazing period (0.12 vs. 0.40 kg/d; P < 0.0001). For each 1 10 g increase in NDF/kg fall pasture (DM basis), fall ADG decreased 0.14 kg (P = 0.01). During winter feeding, ADG was 0.30 and 0.39 kg/d for LO vs. HI heifers, respectively (P = 0.0008). During the spring grazing period (April 16 to May 24 in yr 1, April 22 to May 26 in yr 2, and April 5 to May 16 in yr 3), LO heifers had numerically greater ADG than HI heifers (1.38 vs. 1.30 kg/d; P = 0.64). Hip height (122.7 vs. 121.4 cm; P = 0.0055), BCS (5.8 vs. 5.6; P = 0.0057), and BW (356 vs. 335 kg; P < 0.0001) at the end of spring grazing was greater for HI than LO heifers. Heifers in the LO group compensated with greater summer ADG than heifers in the HI group (0.74 vs. 0.66 kg/d; P = 0.03). Total ADG from treatment initiation (November) through pregnancy diagnosis (August) was greater for HI than LO heifers (0.61 vs. 0.55 kg/d; P < 0.001) as was BW at pregnancy diagnosis (415 vs. 402 kg; P = 0.0055). Percentage of heifers reaching puberty by the time of AI was 34% for both groups (P = 0.93). Percentage of heifers becoming pregnant to AI tended (P = 0.13) to be greater for HI (44%) than for LO heifers (32%). Fall ADG across treatment groups affected the probability of a heifer becoming pregnant by AI (P = 0.01). Percentage pregnant by natural service (61% for LO vs. 59% for HI; P = 0.80) and final pregnancy rate (74% for LO vs. 77% for HI; P = 0.61) was not different for the 2 groups. These results indicate that altering fall forage allowance may delay the majority of BW gain until late in heifer development without negatively affecting overall pregnancy rates.

Productive and metabolic response to two levels of corn silage supplementation in grazing dairy cows in early lactation during autumn

Corn (Zea mays L.) silage (CS) is a nutritious food that can be used as a supplement in dairy cows. The aim of this study was to determine the effect of supplementation with two amounts of CS on milk production and composition, live weight and body condition, as well as on some blood indicators for energy and protein metabolism on dairy cows in early lactation and grazing low mass pasture during autumn. The study was carried out in 40 Holstein Friesian cows over 57 d. Prior to experimental treatment, milk production and days of lactation averaged 24.1 ± 2.8 kg d-1 and 62 ± 14 d, respectively. The dietary treatments consisted of two levels of supplementation with CS; 4.5 and 9 kg DM cow-1 d-1 (treatments LCS and HCS, respectively). Additionally, all the cows received a pasture allowance of 21 and 3 kg DM cow-1 d-1 of concentrate. Milk composition was determined using infrared spectrophotometry, while blood indicators were obtained using an autoanalyzer. There were not differences between treatments regarding milk production or composition, total DM or energy intake. Herbage and protein intake was higher for LCS treatment (P < 0.001). Increasing supplementation decreased (P < 0.001) daily weight gain but did not affect body condition. Plasma concentrations of βOH-butyrate were lower (P = 0.038) for the LCS treatment; while urea concentrations were higher (P = 0.003), with no differences for non-esterified fatty acids (NEFA) concentrations. Supplementation with 4.5 kg d-1 of CS was sufficient to meet the production requirements of the cows.

Efficiency of use of metabolizable energy for body weight gain in pasture-based, nonlactating dairy cows

Four cohorts of nonlactating, pregnant dairy cows (n=50, 47, 45, and 42) were individually fed indoors to determine the amount of feed required for body weight (BW) gain from autumn pasture and commonly used supplementary feeds. These results were used to estimate the apparent efficiency with which metabolizable energy (ME) is used for BW gain (app_kg). Control cows were offered autumn pasture to estimated maintenance requirements (~0.55MJ of ME/kg of BW0.75), with an additional 20 MJ of ME/d allocated for pregnancy and activity. All other cows received the same allowance of autumn pasture and an additional allowance (2.5 or 5.0kg of dry matter/d) of autumn pasture (Past), spring pasture silage (Psil), maize silage (Msil), cracked maize grain (Mgr), or palm kernel expeller (PKE), resulting in a total of 11 treatments. Individual cow dry matter intake was determined daily; BW was recorded once per week for cohorts 1 and 2, and 3 times per week for cohorts 3 and 4. The ME contents of feeds were estimated from feed quality assays. Regression analyses were used on each feed to determine the ME requirement for 1kg of BW gain. The app_kg of Past and Msil was 0.34 and 0.47, respectively; these estimates are in line with published literature. The app_kg of Psil (0.50) was consistent with the published kg for spring pasture, from which the silage was made. Palm kernel expeller had the greatest app_kg (0.61). The reasons for this cannot be deduced from the current study but may reflect the relatively high fat content of the feed and the high kg of fat. The app_kg for Mgr was low (0.38) in comparison with the other supplementary feeds and, in particular, relative to its feed ME and published kg estimates. Although the reason for the low app_kg cannot be deduced from the current data, the most plausible reason is the preferential use of propionate-derived glucose for conceptus metabolism rather than BW gain, a factor not accounted for in previous experimental models that did not use late-gestation cows. In summary, the app_kg for autumn pasture was low but consistent with historical growth rate trials in other ruminant species. In comparison, Msil, Psil, and PKE were used with a greater apparent efficiency (app_kg=0.47 to 0.61), but Mgr resulted in a relatively low rate of gain per MJ of ME (app_kg=0.38). These differences have implications for accurate feed budgeting on farm.

Phyto-oestrogens and their metabolites in milk produced on two pastures with different botanical compositions

Phyto-oestrogens are a group of secondary plant metabolites that may bind to oestrogen receptors and exert oestrogenic or anti-oestrogenic effects in humans and can protect against cancer diseases. When ingested by dairy cows, phyto-oestrogens can be metabolised and transferred to the milk. The objective of this study was to assess the effects of grazing a recently established pasture containing red clover (Trifolium pratense L.) and an older pasture containing a variety of sown and unsown plant species on milk concentrations of phyto-oestrogens. Sixteen Norwegian Red dairy cows [mean (standard deviation); body weight 599 (45.1)kg, stage of lactation 73 (15.0) d in milk, milk yield 29.9 (2.90) kg/d at the start of the experiment] were divided into two groups and grazed either a short-term pasture (SP) or a long-term pasture (LP). The SP was representative of organically managed leys in Norway, which are frequently, approximately every third year, renewed by soil tillage and seeding, whereas LP was representative of organically managed grasslands that are less frequently renewed. The SP contained meadow fescue (Festuca pratensis Huds.) (mean 34%), timothy (Phleum pratense L.) (mean 19%), red clover (mean 28%), shepherd׳s-purse (Capsella bursa-pastoris (L.) Medik.) (mean 6%), pineappleweed (Matricaria matricarioides Porter ex Britton) (mean 5%) and scentless mayweed (Tripleurospermum perforatum (Mérat) Laínz) (mean 4%), and LP contained mainly white clover (Trifolium repens L.) (mean 21%), smooth meadowgrass (Poa pratensis L.) (mean 19%), timothy (mean 17%), meadow fescue (mean 15%), perennial ryegrass (Lolium perenne L.) (mean 6%), tufted hairgrass (Deschampsia cespitosa (L.) P. Beauv.) (mean 5%), northern dock (Rumex longifolius DC.) (mean 4%), common couch (Elytrigia repens (L.) Desv. Ex Nevski) (mean 4%), red clover (mean 3%) and dandelion (Taraxacum spp.) (mean 3%). In addition to a daily pasture allowance of 20kg dry matter per cow, supplements of 3.0kg barley (Hordeum vulgare L.) concentrate were fed. Herbage, concentrates and milk was sampled during the last week of three experimental periods and analysed for phyto-oestrogens using LC-MS/MS technology. Herbage from SP had 19 times higher concentration of isoflavones than herbage from LP, whereas only small differences were found for lignans. Milk produced on SP had 14 times higher concentrations of the mammalian isoflavonoid equol, and the concentrations of equol were higher than found in most other studies. This study confirms that grazing pastures containing red clover increases concentrations of isoflavones and especially equol in bovine milk compared to grazing pastures with other botanical composition. The higher milk concentrations of the lignan metabolite enterodiol in milk from SP compared to LP could not be related to differences in intake of the analysed lignans and may therefore be related to unidentified lignans.

Diurnal variation in rumen fill of dairy cows grazing Persian clover at different pasture allowances

In this experiment 12 rumen-fistulated cows in late lactation, grazing Persian clover (Trifolium resupinatum) at four pasture allowances [9, 16, 32 and 53 kg dry matter (DM)/cow.day], had their entire rumen contents removed and sampled six times over 6 days, with the time of sampling varied between days. These rumen pool size measurements occurred at 0645 hours, 0915 hours, 1045 hours, 1345 hours, 1530 hours and 1900 hours. The cows were offered new allocations of pasture twice daily at 0715 hours and 1530 hours. Herbage intake increased (P &lt; 0.001) from 5.6 to 20.4 kg DM as pasture allowance increased. Pasture allowance had no effects on rumen pool sizes of wet matter (WM) (P = 0.95), DM (P = 0.914), neutral detergent fibre (NDF, P = 0.499) or the DM% of the digesta (P = 0.078). Rumen pool sizes of WM, DM and NDF varied throughout the day. Pool sizes of WM and DM were lowest at 0645 hours and highest at 1900 hours for all allowances (P &lt; 0.001) and along with pool sizes of NDF, were also lower at 0645 hours compared with 0915 hours and at 1530 hours compared with 1900 hours. The lack of increase in rumen pool sizes as pasture allowance increased when cows grazed Persian clover suggests that outflow rates increased with the increasing intakes. The low, and similar, rumination times between allowances also suggests that there is little restriction to the ability of outflow rates to increase when cows graze Persian clover at increasing allowances. The changes in rumen pool sizes over the day were consistent with the twice daily allocation of fresh pasture to the cows. The diurnal rumen pool size information obtained from this experiment will assist with the development of mechanistic rumen models that are capable of simulating the discontinuous intake and varying rumen pool sizes of cows in grazing systems.