A range of annual legume genotypes comprising one line of Trifolium subterraneum, four lines of T. michelianum, 11 of T. resupinatum var. resupinatum, and one line of T. resupinatum var. majus were grown in glasshouses under temperature regimes of 10−15°C and 16−21°C. Dry matter (DM) weights of stem, leaf, and flower tissues were measured when plants had six nodes, at first flower appearance, and at senescence. All samples were scanned by near-infrared reflectance spectroscopy (NIRS). One-third of the samples, covering the range of spectral characteristics, were analysed for in vitro digestible organic matter (DOMD), organic matter, crude protein (CP), neutral detergent fibre (NDF), lignin, cellulose, and the hemicellulosic polysaccharide monomers arabinose, xylose, mannose, galactose, and rhamnose. These data were used to develop calibration equations from which the composition of the remaining samples was predicted by NIRS. The higher temperature resulted in plants reaching respective phenological stages earlier, but did not affect either DM yields of total plant, stem, leaf, and petiole tissues or the proportions of each fraction. In vitro DOMD and arabinose and galactose levels decreased, while lignin, cellulose, NDF, xylose, mannose, and rhamnose levels increased with advancing maturity. In vitro DOMD was positively associated with contents of CP, arabinose, galactose, and the arabinose/xylose ratio and was negatively associated with contents of lignin, cellulose, NDF, xylose, mannose, and rhamnose. Lignin contents were highly correlated with levels of both xylose and mannose. Stems were more digestible than leaves in subterranean clover and T. resupinatum var. majus. The study also demonstrated that NIRS can be used routinely as a quick, inexpensive, and reliable laboratory technique to predict feed components of annual Trifolium legumes.

This book presents strategies for feeding energy and protein supplements to pasture-fed dairy cows and examines the potential economic benefits. Effective supplementary feeding of concentrates is critical to the success of all dairy farms. This book is a substantially revised edition of 'Feeding Concentrates: Supplements for Dairy Cows' DRDC 1993. It focuses on feeding concentrates to pasture fed cows to achieve high milk production per cow per hectare, and will assist farmers to decide which supplements give the best results in their particular situation. The benefits that arise from supplementary feeding include higher stocking rates, promotion of growth in heifers and young cows; better body condition score and increased lactation length when pasture is less available; improved pasture use; reduced cost per tonne of pasture eaten; flexibility to increase milk production when milk prices are high; and increased milk protein content when the energy content in pasture is low. This edition has thoroughly reviewed the issues and clearly documents the results of research particularly for grains supplementation. The summaries and recommendations in each chapter will be particularly helpful to dairy farmers in making best management decisions relating to concentrate feeding.

This paper reports on both the individual and combined effects of age (AFC) and liveweight (LWFC) at first calving for Australian Holstein–Friesian heifers on first lactation production. One hundred and thirty-five Australian Holstein–Friesian heifers were allocated to 1 of 3 AFC treatments. Within each AFC treatment, heifers were randomly assigned to 1 of 3 LWFC treatments. Heifers in all groups grazed pasture and were supplemented when the quantity and quality of pasture was inadequate to meet growth requirements. Mean AFC and LWFC achieved were 25.1, 29.9 and 33.9 months and 498, 549 and 595 kg, respectively. Mean liveweight gains from 16 weeks of age to calving ranged from 0.45 to 0.71 kg/day, depending on treatment. The heifers calving at 33.9 months of age produced 6.6 and 12.3% more milk, 6.3 and 11.9% more protein and 5.4 and 12.2% more fat than those calving at 29.9 and 25.1 months of age at the end of their first 300 day lactation, respectively. The lower production of the younger cows was associated with decreased daily output rather than by shorter lactation length. Heifers averaging 595 kg at first calving produced 5.5% more milk, 8.4% more protein and 11.4% more fat than those averaging 498 kg in first lactation, respectively. The heifers averaging 621 kg LWFC and 34 months AFC had the highest production of the 9 treatment groups. Production was increased by 5.35 L milk, 0.19 kg protein and 0.23 kg fat for an additional 1 kg LWFC, respectively. For each month delay in AFC, production was increased by 66.7 L milk, 1.87 kg protein and 2.36 kg fat, respectively. The combined effects of AFC and LWFC showed that to offset the negative effects of a 1 month reduction in AFC on milk, protein and fat yields in first lactation, LWFC would have to be increased by 8.1, 4.0 and 4.5 kg, respectively. Under the conditions of this experiment, maximum milk, protein and fat were estimated to be achieved at 559, 563 and 568 kg liveweight at first calving, respectively.

Sixty-three Friesian heifers were assigned to three different diets (21 per group) of 11 MJ ME per kg DM containing low crude protein (CP, 142 g CP per kg DM) with high rumen protected protein (REP, 270 g REP per kg CP) (diet A), high-CP (183 g CP per kg DM) with low-REP (133 g REP per kg CP) (diet B) and high-CP (182 g CP per kg DM) with high-REP (267 g REP per kg CP) (diet C) to obtain liveweight gains (LWG) of greater than 900 g per day between five and ten months of age in order to study the influence of dietary CP and REP concentration on mammary gland development and subsequent milk production. Six heifers per group were slaughtered at 16 months of age for evaluation of mammary glands. Pre-pubertal LWG was influenced by dietary CP concentration, such that heifers consuming diets B and C gained more than those consuming diet A (918 vs. 952 vs. 990 g per d). Dietary REP concentration did not influence pre-pubertal LWG. At slaughter, heifers consuming pre-pubertal diets with high-CP concentrations had less mammary fat tissue area and a lower ratio of fat to secretory tissue compared with those on the low-CP diet (74.9 vs. 42.7 vs. 24.1 m2; 1.6 vs. 0.69 vs. 0.61). Heifers that consumed diet B during the pre-pubertal period had heavier dry udder weights, and tended to have more mammary fat and more secretory tissue area in the dry udder at slaughter than those heifers that consumed diet C (820 vs. 519 g; 636 vs. 420 g; 64.2 vs. 39.9 m2). Age and LW at calving were not influenced by either dietary CP or REP concentration. Daily first lactation milk, protein and fat yields were not influenced by pre-pubertal dietary CP concentration. The REP concentration in the pre-pubertal diets did not influence daily milk and fat yields but heifers that consumed diet C produced 0.08 kg more daily protein than did heifers that had consumed diet B.

DIETARY PROTEIN AND DAIRY COW FERTILITY: Feeding more dietary protein has been negatively associated with dairy cow fertility in some but not all studies. We used meta-analysis to examine the relationship between dietary crude protein and conception rate. While a higher intake of dietary crude protein significantly lowered conception rate, the potential for feeding less degradable dietary protein to modify this relationship was not demonstrated. MILK UREA CONCENTRATIONS AND DAIRY COW FERTILITY: The use of milk urea as an indicator of dietary energy and protein intake and as an indicator of reproductive performance has been questioned. We found that changes in urea concentration in body fluids explained only 25% (p = 0.08) of the variance in conception rate after conducting a meta-analysis of available studies. INTERPRETATION OF MILK UREA CONCENTRATIONS: High intakes of dietary protein may induce adaptations in urea metabolism, and the negative relationship identified between high intakes of dietary protein and fertility for Northern Hemisphere dairy herds may not necessarily apply in Australasian dairy herds. Because of the potential for cows to adapt to high protein diets, the use of a single milk urea determination on a herd will have limited value as an indicator of nutritional status and little value as a predictor of fertility.

Milk urea concentrations in dairy cattle. There has been increased use of milk urea concentration as an indicator of dietary protein intake and protein metabolism in dairy cattle over recent years. The value of milk urea content data in predicting dietary composition, particularly for pasture-fed cattle, has not been well described.Protein metabolism and urea synthesis. Many factors influence the degradation of dietary proteins in the rumen, post-ruminal protein metabolism and urea synthesis in cattle. Strong positive correlations between nitrogenous fertiliser use and the crude protein content of pastures were identified by use of meta-analysis. Similar strong positive correlations were noted between dietary protein intake, rumen ammonia and plasma urea concentrations. The costs of urea synthesis include energy losses, and importantly, the loss of endogenous amino acids, which are deaminated in the synthesis of urea.Milk urea as an indictor of protein metabolism. Urea concentrations in blood, plasma and milk are strongly correlated. Milk is an adequate indicator of blood and plasma urea content, but non-nutritional factors may significantly influence milk urea concentrations. Recommendations for dietary protein management based on milk urea concentrations must be undertaken with care.

Two studies were conducted to compare the precision of estimating kikuyu grass (Pennisetum clandestinum) intake by Friesian cows fed 0, 3 or 6 kg of cereal-based concentrate/cow.day, using a rising plate meter (RPM), standard energy requirements in reverse (RS) and plant wax alkanes as internal markers. Study 1 compared herbage intake estimates obtained using the RPM and RS techniques over a 45-day period. RS estimates were based on the metabolisable energy (ME) of ration components derived from in vitro organic matter digestibility (OMD) values. Pregrazing calibration equations for the RPM determined at 2-weekly intervals differed significantly (P<0.01) from postgrazing calibrations; consequently separate equations were used to determine pasture intake as the difference in pre- and post-grazing pasture mass. Estimates of total intake were lower using the RPM than the RS technique for the groups fed 0 kg (12.5 v. 14.8 kg dry matter (DM)/cow.day) and 3 kg (10.4 v. 12.9 kg DM/cow.day) of concentrate, and higher for those receiving 6 kg (10.5 v. 7.8 kg DM/cow.day). In study 2 (12 days duration), intakes derived using alkanes were compared with intakes estimated using the RS and RPM techniques. The C32/C33 alkane pair gave the closest estimate of herbage intake to that obtained using the RPM and RS techniques. Whole diet in vivo DM digestibility (DMD), determined by the alkane method, was not significantly different between the 3 groups (mean 70%), suggesting that digestibility of the kikuyu declined with increasing concentrate supplementation. The in vivo DMD of kikuyu alone (determined in the non-concentrate-supplemented cows) was considerably higher (69.5%) than the OMD determined in vitro (63.9%). By using in vivo rather than in vitro digestibilities for kikuyu in the RS calculations, the intake estimates were reduced by 17%, and for the 0 kg concentrate group, intake estimates aligned closely to predictions of the RPM and alkanes. Concentrates in the diet resulted in lower intake estimates using the RS technique compared with the RPM and alkane techniques. This was most evident at the 6 kg level of supplementation where RS predicted kikuyu intake to be 6.5 kg DM/cow.day using in vivo-derived DMD and this was substantially lower than either the RPM (12.4 kg DM/cow.day) or alkanes (9.2 kg DM/cow.day). The alkane technique provided a direct and precise method of measuring the intake of individual cows grazing tightly-managed kikuyu pasture. With the use of accurate animal production and feed quality parameters, the RS technique can provide sensible pasture intake estimates over an extended time period. The RPM technique is useful for obtaining herd estimates of pasture intake and for the determination of pasture parameters associated with intake.

This study, conducted on the north coast of New South Wales, determined the optimal time to defoliate kikuyu (Pennisetum clandestinum Hochst ex chiov.) in terms of pasture quality in relation to the number of leaves per tiller. It also compared the quality of well-managed kikuyu grass and ryegrass (Lolium perenne L.) pasture to determine the nutrients in kikuyu likely to limit milk production.The crude protein (CP), P, and K concentrations of individual leaves declined; Ca and Mg increased; and Na levels remained constant with increasing age. These changes in individual leaves were reflected in the quality of kikuyu available above the 5-cm stubble height.The proportion of green leaf available above the 5-cm stubble height declined whilst the proportion of stem and dead material increased markedly after 4.5 leaves per tiller had regrown. These changes were reflected in a substantial decline in organic matter digestibility (OMD) and CP of herbage.Between 0900 and 1500 hours, water-soluble carbohydrate (WSC) levels in kikuyu above the 5-cm stubble height increased at a rate of 5 g/kg dry matter (DM) per hour, reaching maximum levels during the mid afternoon.Kikuyu fertilised at a high rate of N fertiliser contained significantly higher nitrate levels than that receiving moderate levels (3.12 v. 0.67 g/kg DM, respectively). There was a linear increase in the levels of nitrate as the CP of forage exceeded 230 g/kg DM.Kikuyu and ryegrass samples plucked to simulate forage consumed by milking cows were obtained in the midst of the growing season for each species. Kikuyu had a lower OMD than ryegrass (733 v. 842 g/kg DM) but contained higher levels of neutral detergent fibre (600 v. 400 g/kg DM). High levels of CP and low content of WSC in kikuyu compared with ryegrass resulted in a much lower ratio WSC:CP (0.09 v. 0.36, respectively). Kikuyu contained 50% less Ca than ryegrass, much of which would be expected to be bound to oxalates and thus unavailable to grazing stock. The concentration of Na in kikuyu was extremely low compared with ryegrass (0.15 v. 3.67 g/kg DM, respectively).The most desirable stage of regrowth of kikuyu on which to graze lactating dairy cows, in terms of a compromise between forage quality and quantity, appears to be at 45 leaves/tiller. However, even at this stage, various innate nutrient deficiencies would appear to restrict milk production to 15-16 L milk/cow day.

Three studies were conducted to examine the production response of Friesian cows grazing well-managed lukuyu (Pennisetum clandestinum) pasture to supplementation with a cereal grain concentrate, with and without the inclusion of formaldehyde-treated protein meal. Mean (¦ s.e.) levels of nutrients in the pasture (g/kg DM) on offer were: 205 ¦ 3 crude protein; 683 ¦ 7 in vitro organic matter digestibility; 239 ¦ 2 acid detergent fibre; 615 ¦ 8 neutral detergent fibre and 4.47 ¦ 0.16, 2.51 ¦ 0.06, 31.96 ¦ 0.98, 0.39 ¦ 0.03 and 3.18 ¦ 0.09 of calcium, phosphorus, potassium, sodium and magnesium, respectively. Study 1 was a 3-farmlet study conducted over 45 days (March-April 1993) involving cows 5-6 months into lactation, which compared 3 levels of concentrate feeding at 0 (R0), 3 (R3) or 6 (R6) kg crushed barley/cow.day. Study 2 was an 18-day extension of study 1 with animals in the seventh month of lactation. The concentrate fed was 72% barley and 24% formaldehyde-treated sunflower meal. Pasture intake of individual cows was determined using an alkane technique. Mean milk yields (L/cow. day) in study 1 were 14.2, 18.3 and 18.0, and in study 2 were 12.5, 18.5 and 17.4 for treatments R0, R3 and R6, respectively. Milk fat (3.77 v. 3.26%), but not milk protein, content of the Ro cows was significantly higher than R6 cows in study 1 only. In study 2, the apparent whole-diet digestibility remained constant as concentrate level rose, indicating a negative effect of concentrate fed on forage digestibility in the absence of buffers. Study 3 was a 3 x 4 factorial design plus a 'control' group (0.5 kg barley/cow.day used as a carrier for minerals) to examine the milk production response to 3 levels of concentrate feeding (3, 6 and 9 kg/cow.day) with 4 levels of formaldehyde-treated canola meal (FTCM; 0, 20, 40 and 60% of concentrate). Rations were iso-energetic within levels of concentrates fed. The control group had significantly lower milk production (17.2 L/cow.day), as well as milk protein (2.90%), plasma urea (PU) (5.90 mmol/L) and P-hydroxybutyrate (G-OHB) (0.525 mmo1L) than other treatment groups. The mean milk production response of 0.6 L milk/kg concentrate fed in study 3 at the 3 kg/day level of feeding was lower than observed in studies 1 and 2 (1.4 and 2.0 L/kg concentrate, respectively). The level of metabolisable energy in the concentrate in study 3 had a significant influence on milk production, milk fat and milk protein levels. Plasma glucose and G-OHB levels significantly increased with the incorporation of FTCM into the concentrate. Nonesterified fatty acid levels dropped significantly below levels of other treatments at the lowest level of inclusion of FTCM. PU levels generally increased in response to increasing metabolisable energy and inclusion of FTCM in the concentrate, with an interaction between them. Milk urea (MU) levels (mmol/L) showed a significant linear (P<0.001; r2 = 0.44) relationship to PU levels (mmol/L) as follows: MU = 0.167 + 0.272PU.

Cereal grains including wheat, barley, oats, maize and sorghum were incubated with strained rumen fluid in vitro with either ryegrass or lucerne in the ratios of 0:100, 25:75, 50:50, 75:25 and 100:0 at 39 degrees C for 24 h. Expected NDF digestibilities in mixtures of cereal grain and forage were calculated by interpolation between NDF digestibilities of each grain and of each forage. These were compared with measured NDF digestibilities to detect deviations due to synergism or inhibition. Wheat, barley and maize had inhibitory effects, whereas oats and sorghum had synergistic effects, on NDF digestibility with both forages.

The stoichiometry of fermentation was investigated in vitro with wheat and maize grains. Gas production proved to be an accurate index of VFA production and change in pH. Gas and total VFA production from wheat were strongly correlated with starch disappearance. On a stoichiometric basis, 66% of gas and 64% of VFAs produced from wheat were accounted for by starch fermentation. With maize only 18% of gas and 23% of VFAs produced were accounted for by starch disappearance. There were significant differences between grain species in rates of gas production (P < 0.001), being ranked in the order wheat > triticale, oats > barley > maize > rice, sorghum. Effects of varieties and growing sites on gas production were significant with wheat, oats, maize and sorghum. With barley, only varietal effects were significant (P < 0.001). With maize and sorghum, there were significant variety by site interactions.

Twenty-one Holstein Friesian cows were used in a 3 x 3 Latin square design to determine effects of barley supplementation on pasture intake, rumen fermentation and milk production. Cows were grazed on perennial ryegrass-white clover pasture and allocated to three groups supplemented with 0, 4 or 8 kg day-1 of barley grain. Intakes of metabolisable energy (ME) and crude protein from pasture, estimated using pasture clipping techniques, were in excess of requirements for cows giving 201 day-1. Substitution rates were similar with both levels of grain supplementation and lower than predicted. Consistent with this, there were minor differences in rumen pH, rumen volatile fatty acids concentrations and rumen osmolality. These observations indicate that either the barley grain was fermented slowly in the rumen or the pasture had a significant buffering capacity.The yield of fat-corrected milk increased by only 0.1 kg kg-1 barley and there was a significant reduction in plasma 3-hydroxybutyrate. These results suggest that, despite the substantial increase in intake when barley was fed, the milking potential of the cows was not greatly limited by ME intake, and most of the additional energy intake was partitioned into body tissue.