A field study was conducted to evaluate the effect of weed management practices in the main crop on growth, yield and economics of rice- ratoon rice cropping system in two consecutive years i.e., 2014–15 and 2015–16. The result showed that Cyperus difformis was the most dominant weed in the main rice crop, whereas Ludwigia adscendes was the dominant weed in ratoon rice. In weed-free plots, the main crop recorded the highest productivity of 47.52 kg/ha/day, whereas the ratoon crop registered productivity of 37.70 kg/ha/day which was the 79.3% of the main crop productivity. In the weedy plot, crop-weed competition caused 28.8 and 37.5% reduction in energy use efficiency and energy productivity of the rice-ratoon rice cropping system respectively. Yield reduction of 37.3 and 43.6% in the main crop and ratoon crop respectively recorded due to weed infestation in weedy check. All the weed control practices registered an increase in system productivity, nutrient uptake and energy use efficiency. Among the herbicidal treatments, application of bensulfuron-methyl + pretilachlor (60 + 600 g/ha) at 10 DAS to the main crop registered a higher net return of USD$ 639.2 and 260.1 of main crop and ratoon crop, respectively. Hence it can be recommended for weed management in rice-ratoon rice cropping system.

Silvopastoral systems (SPSs) are sustainable alternatives for pasture intensification. Management practices such as thinning are options to diminish competition for resources between pasture and trees, ensuring appropriate forage production. The objective of this study was to evaluate the productive and nutritive traits of Piatã palisadegrass (Urochloa brizantha cv. BRS Piatã) after thinning the forest component of a SPS. Forage production and nutritive value, along with microclimate variables were assessed in a SPS and in an intensive system (INT) in São Carlos-SP, Brazil, from 2016 to 2018. The INT was a full sun pasture of Piatã palisadegrass, while the SPS was established with Piatã palisadegrass shaded by eucalyptus (Eucalyptus urograndis clone GG100) spaced 15 × 2 m but thinned to 15 × 4 m before the onset of the experiment. In the SPS, measurements were made under the tree row (SPS_1), 3.75-m (SPS_2), 7.5-m (SPS_3) and 11.25-m (SPS_4) distant from the North row. Forage accumulation in the two systems were similar, whereas the pre-grazing forage mass in most of the SPS positions were smaller than that of the INT during the autumn of 2017 and summer of 2018. Crude protein (CP) content was greater in the SPS than in the INT in most positions and seasons. Forage production was favoured by the thinning of the trees mainly in the seasons close to the event, while forage CP was consistently greater in the understory pasture. Thinning of trees in SPSs can be adopted to provide forage production similar to intensive pastures with higher protein content.

Hybrid seed production often relies on managed pollinators whose use in isolation cages can pose challenges. Here, we evaluated the pollination ability of the novel managed pollinator Eristalinus aeneus (Diptera: Syrphidae) in hybrid celery and fennel seed crops. During trials performed in 2019–2020 in Cordoba, Spain, we compared seed production with hoverflies released at high and low densities (40–20 ind./m2), and without released pollinators. In celery, we included a treatment with Lucilia sericata (Diptera: Calliphoridae), a blowfly used for seed production (375 ind./m2). The production of celery seeds when E. aeneus were released at high density was significantly higher (+49%) than without released pollinators, for both sterile and fertile plant genotypes; no significant differences were found between the two hoverfly densities and the blowfly treatments. In fennel, seed yield of fertile plants with high density of hoverflies was higher than with low density (+149%), or without released pollinators (+168%); whereas for sterile plants no differences were found between treatments. In both crops and plant genotypes, the highest pollen adhesion to stigmas (number of pollen grains and proportion of flowers with pollen adhered in two stigmas) was obtained with hoverflies at high density. In celery, pollen adhesion was higher with high density of hoverflies than with blowflies for both plant genotypes, despite the considerably lower numbers of released hoverflies. Our results suggest that E. aeneus is a more efficient pollinator of celery than L. sericata, and that it has the potential to effectively pollinate other hybrid Apiaceae seed crops like fennel.

Placement of fertilizer in the seed furrow to increase nutrient availability is a common practice in row-crop production. While in-furrow application of fertilizer is widely utilized in the production of winter wheat (Triticum aestivum L.), there is a lack of work evaluating new formulations and nutrient combinations that are available. The objective of this study was to quantify the effects of in-furrow fertilizer products and combinations of products on winter wheat grain yield, nitrogen and mineral concentrations. Trials were conducted across five site-years in central Oklahoma using 11 fertilizer formulations placed in-furrow at the time of planting. In locations that soil test phosphorus (STP) levels or potassium were above sufficiency, the use of in-furrow fertilizers did not improve yield over the control. Inconsistency of response was noted at locations where STP levels were below the critical threshold. While one location showed no response to the addition of P regardless of source, two other locations had significant yield responses from three or more P-containing fertilizers. The addition of both sulphur and zinc resulted in increased yield over the base product at one low STP location. Nutrient concentrations were also influenced in nutrient-limited soils; however, no trends in response were present. Based upon the results of this study, the application of in-furrow fertilizer has the potential to increase winter wheat grain yield and nutrient concentration, when soil nutrients are limiting. As expected the addition of fertilizer when soil test levels are at or above a sufficiency did not increase grain yield.

Nitrogen fixation from pasture legumes is a fundamental process that contributes to the profitability and sustainability of dryland agricultural systems. The aim of this research was to determine whether well-managed pastures, based on aerial-seeding pasture legumes, could partially or wholly meet the nitrogen (N) requirements of subsequent grain crops in an annual rotation. Fifteen experiments were conducted in Western Australia with wheat, barley or canola crops grown in a rotation that included the pasture legume species French serradella (Ornithopus sativus), biserrula (Biserrula pelecinus), bladder clover (Trifolium spumosum), annual medics (Medicago spp.) and the non-aerial seeded subterranean clover (Trifolium subterraneum). After the pasture phase, five rates of inorganic N fertilizer (Urea, applied at 0, 23, 46, 69 and 92 kg/ha) were applied to subsequent cereal and oil seed crops. The yields of wheat grown after serradella, biserrula and bladder clover, without the use of applied N fertilizer, were consistent with the target yields for growing conditions of the trials (2.3 to 5.4 t/ha). Crop yields after phases of these pasture legume species were similar or higher than those following subterranean clover or annual medics. The results of this study suggest a single season of a legume-dominant pasture may provide sufficient organic N in the soil to grow at least one crop, without the need for inorganic N fertilizer application. This has implications for reducing inorganic N requirements and the carbon footprint of cropping in dryland agricultural systems.

To study the impact of plant density on Chenopodium quinoa (c.v. CICA-17) achene yield and its relationship with morphology, leaf anatomy and gas exchange in the absence of water stress, field trials were conducted at 1995 m asl in Northwestern Argentina. Two plant densities were evaluated; low density (LD) 7.2 plants/m (120 240 pl/ha) and high density (HD) 27.9 plants/m (465 930 pl/ha). HD treatment caused light competition, inducing morphological and anatomical changes in Quinoa plants. Plants grown under HD conditions showed decreases in plant height and stem diameter, lower stomatal dimensions and densities, and thinner leaf blades. Compensation strategies such as increases in specific leaf area and a higher number chloroplasts per palisade cell were observed, nevertheless these changes did not fully compensate C absorption and gas exchange limitations, therefore limiting the uptake of N and P and resulting in a 53.2% lower yield of HD compared to LD. Considering the ability of quinoa plants to change its morphology and anatomy, further studies with intermediate plant densities are necessary in order to determine if it is possible to achieve higher yields and to increase the efficiency in the use of the resources.

Composting from organic municipal solid waste (MSW), such as a separate waste collection, is a valid tool for eliminating a considerable amount of waste that would otherwise be destined for landfills and incinerators, thus representing an effective complement to traditional forms of recycling. It allows organic substance to be recovered and reintegrated into the soil, thus preventing erosion phenomena, increasing the biological fertility of the soil and contributing significantly to the restoration of impoverished sites. Modern winegrowing must address the issue of vineyard fertility in the sustainability context. The goal of this study was to assess the advantages of distributing a sustainable product to the vineyard that can achieve vine balance (vegetative and productive equilibrium). In a Vitis vinifera L. Sangiovese cv., vineyard, four soil treatments were applied (three compost rates and a control): municipal solid waste compost (40 tons per hectare – MSW40, 15 tons per hectare – MSW15, 2.5 tons per hectare – MSW2.5), and no compost (CTRL). The vine physiology (leaf gas exchange and water potential) and berry compositions (phenolic and technological maturity) were studied during the 2018–2019 growing seasons in the Sieci area, Italy. The results of this experiment provide some general insights showing that MSW compost options can be expected to reduce water stress, balanced vine performance and provide sustainable recirculation of organic matter. MSW compost is a true agronomic and environmental resource.

This study was carried out to determine the effects of different irrigation levels and different tillage and sowing methods on the amount of irrigation water, evapotranspiration, water productivity (WP) and yield in the second crop soybean in Çukurova Region, Turkey. Three irrigation levels were applied (I100: completion to the field capacity of the available water of 60 cm soil depth weekly. I70: 70% of the water applied to I100, I50: 50% of the water applied to I100), five tillage and sowing methods were used (T1: traditional soil tillage, T2: reduced soil tillage, T3: reduced soil tillage, T4: ridge tillage, T5: no-tillage). The research was carried out in a randomized block split-plot design with three replications. The result of, the highest yield was obtained in I100xT1 with 4990 kg/ha, while the lowest yield was obtained in I50xT3 with 3150 kg/ha in irrigation x tillage interactions. When the water consumption values of plants were analysed, the highest was obtained with 632 mm I100 and the lowest with 399 mm I50. When WP values were analysed, the highest was obtained with 8.7 in I50 and the lowest in 6.6 and I100. As a result, full irrigation and direct sowing methods (I100T1) are recommended in soybean cultivation considering the highest water-yield relationship in the Mediterranean Region.

Applying coffee pulp biochar (BC) can be a complementary practice to the application of chemical fertilizers (CF) of crops; however, little evidence of its combined effects on coffee cultivation has been reported. A field trial was carried out during two evaluation years (2019 and 2020) to analyse the effect of the application of different BC doses (0, 4, 8 and 16 t/ha) in combination with four levels of fertilization (0, 33, 66 and 100% of the nutritional requirements) on physiological responses of 3-year-old coffee (Coffea arabica L. var. Castillo) trees. The results indicated that trees with 0 t/ha BC and 0% CF showed the lowest values in all the physiological variables studied (gs = 269.9 and 126.8 mmol/m2/s; Chl = 61.7 and 54.7 At-leaf readings; yield = 0.21 and 0.22 kg of dry parchment coffee (DPC)/tree for 2019 and 2020, respectively). Coffee trees treated with 8 t/ha BC and CF levels of 100% registered the highest results in gs (424.9 and 366.9 mmol/m2/s), Chl (71.1 and 69.8 At-leaf readings), yield (0.41 and 0.57 kg of DPC/tree) in 2019 and 2020, respectively. In conclusion, the application of BC from coffee pulp, especially at a dose of 8 t/ha, generates a positive effect on yield, gs, leaf nutrient concentration and Chl of coffee trees. The use of BC can be an alternative to complement the mineral nutrition of commercial coffee crops to help reduce the application of CF.

Vegetables are widely cultivated in high rainfall and mountainous regions in Sri Lanka with poor soil conservation practices. Accumulation of essential mineral and toxic trace elements in the soils and widely cultivated vegetables of this region are poorly understood. One hundred soil and vegetable (i.e. cabbage, carrot and potato) samples were collected at the time of harvest and analysed for element concentrations. Soils contained high concentrations of essential mineral (N, P, K, Cu, Zn and Mn) and toxic trace elements (As, Cd and Pb). When comparing edible parts, cabbage contained the highest concentrations of mineral and toxic trace elements, and potato contained the lowest. Irrespective of the crop, edible parts contained high concentrations of N, P, K (14–35, 2–6, 15–24 g/kg, respectively), and Cu, Zn, Mn (2.5–6.7, 11–30, 8–147 mg/kg, respectively). Vegetables also contained As, Cd and Pb (0.04–1, 0.02–0.15, 0.02–0.26 mg/kg, respectively), but did not exceed the maximum permissible limits. Irrespective of the crop, 36–64 kg N, 6–11 kg P and 35–45 kg K per ha were removed with the harvest. According to the current rate of vegetable consumption by Sri Lankans (i.e. 240 g fresh weight (FW) per day), per capita consumption of 0.05–0.2 mg Cu, 0.45–0.65 mg Zn and 0.5–2 mg Mn per day through these vegetables was observed, i.e. 5–23% Cu, 7.5–11% Zn and 22–87% Mn of the recommended daily intake. Vegetables grown in the region served as a key source of essential mineral elements. However, agronomic mitigation strategies are needed to improve soil health and sustainability of these cropping systems.

On soils dominated by high proportions of clay and organic matter, soil acidity and poor nutrient use efficiency have a major impact on output potential. Due to the inherent chemical properties of these soils, reducing soil acidity and the prevalence of undesirable metallic cations poses challenges. As a result, these soils have a large capacity for phosphorus (P) fixation, therefore reducing plant P availability. Limestone (CaCO3 or MgCO3) is applied to agricultural soils to counteract soil acidity and reduce P fixation. The current study investigates the effects of four contrasting annual P application rates (0, 50, 100, 150 kg P/ha); split (50:50) between spring and summer, across soils with a range of soil pH values from a previous liming trial. The effect of soil pH ranges and P treatment rates on seasonal herbage growth and herbage P concentration was investigated over three years. Soil nutrient status was also investigated. Soil pH had a significant impact on the rate of mineralization and soil P concentration across each site. A soil pH of 6.2 caused a 1.8 mg/l increase in soil test P. An annual P application was necessary to maintain sufficient herbage P concentration for animal dietary requirements (0.35% DM), however there was no effect of P application or liming rate on herbage productivity across the three sites as all sites possessed sufficient soil P reserves. The current experiment has shown that despite optimal soil fertility status, ensuring sufficient plant available P is a problem on these particular soils.

An isotope dilution model for partitioning phenylalanine and tyrosine uptake by the liver of the lactating dairy cow is constructed and solved in the steady state. An original ten-pool model is adopted and solved by cleaving it into two five-pool sub-models, one representing phenylalanine and the other tyrosine. If assumptions are made, model solution permits calculation of the rate of phenylalanine and tyrosine uptake from portal vein and hepatic arterial blood supply, hydroxylation, and synthesis and degradation of constitutive protein. The model requires the measurement of plasma flow rate through the liver in combination with amino acid concentrations and plateau isotopic enrichments in arterial and portal and hepatic vein plasma during a constant infusion of [1-13C]phenylalanine and [2,3,5,6-2H]tyrosine tracers. It also requires estimates of the rate of oxidation and protein export secretion. Analysis of measurement errors in experimental enrichments and infusion rates on model solutions indicated that accurate values of the intracellular and extracellular enrichments are central to minimising errors in the calculated flows. Solving the model by cleaving into two five-pool schemes rather than solving the ten-pool scheme directly is preferred as there appears to be less compounding of errors and the results consistently appear to be more biologically feasible. The model provides a means for assessing the impact of hepatic metabolism on amino acid availability to peripheral tissues such as the mammary gland.

The objective was to establish a multivariate model using two complementary multivariate statistical techniques, factor analysis and multiple stepwise regression to predict carcase characteristics, carcase cuts, internal fat, viscera and loin eye area from body measurements of goats Boer mestizos. Thirty-two goats were used, with initial average weights of 3.3 ± 0.61 kg and final average weights of 16 ± 2.5 kg. Before slaughter and after 16 h of fasting, body weight was measured along with the biometric measurements (BMs) of each animal: body length, withers height, croup height, chest width, croup width, croup perimeter, thoracic perimeter, leg length and thigh circumference. The half carcases were sectioned in six anatomical regions that made up the commercial cuts: neck, palette, rib, handsaw, loin and ham. BMs showed a high correlation with a few exceptions; most of the correlations are above 50%. What also happens with the Carcass weight and cuts were also correlated above 50% with BMs. The data presented an index for the Kaiser–Meyer–Olkin test of 0.80, demonstrating the adequacy of the factor analysis. Through factor analysis, it was possible to observe that the first two factors extracted accumulated 75.47% of the total variance of the studied characteristics. Moderate to high and positive correlations of morphological characteristics with body weight, carcase characteristics and primary carcase cuts suggested the adequacy of morphological characteristics as criteria for early selection of crossbred Boer goats for their body weight and carcase characteristics without slaughter.

In pasture-based dairy production systems, identifying the appropriate stocking rate (SR; cows/ha) based on the farm grass growth is a key strategic decision for driving the overall farm business. This paper investigates a number of scenarios examining the effects of SR (2–3 cows/ha (0.25 unit changes)), annual nitrogen (N) fertilizer application rates (0–300 kg N/ha (50 kg/ha unit changes)), soil type (heavy and a free-draining soil) and agroclimate location ((south and northeast of Ireland) across 16 years) on pasture growth and forage self-sufficiency using the pasture-based herd dynamic milk model merged with the Moorepark St Gilles grass growth model. The modelled outputs were grass growth, grass dry matter intake, silage harvested and offered, overall farm forage self-sufficiency and N surplus. The model outputs calculated that annual grass yield increased from 9436 kg DM/ha/year when 0 kg N/ha/year was applied to 14 996 kg DM/ha/year when 300 kg N/ha/year were applied, with an average N response of 18.4 kg DM/kg N applied (range of 9.9–27.7 kg DM/kg N applied). Systems stocked at 2.5 cows/ha and applying 250–300 kg N fertilizer/ha/year were self-sufficient for forage. As N input was reduced from 250 kg N/ha/year, farm forage self-sufficiency declined, as did farm N surplus. The results showed that a reduction in N fertilizer application of 50 kg/ha/year will require a reduction in an SR of 0.18 cows/ha to maintain self-sufficiency (R2 = 0.90).

Copy number variation (CNV) is a very common type of gene variation with high frequency. In recent years, CNV has been paid more attention in various fields, especially in livestock and poultry breeding, which has promoted the progress of breeding. WW domain binding protein 1-like (WBP1L) is a protein coding gene, which plays an important role in cattle populations, and its function has been extensively studied, but it is not clear whether the copy number of the gene can affect the growth and development of cattle populations. In this study, CNV of WBP1L gene was detected in 732 cattle of seven breeds (Qinchuan cattle, QC; Pinan cattle, PN; Yuengling cattle, YL; Xianan cattle, XN; Jiaxian cattle, JX; natural Guyuan cattle, NGY; Jian cattle, JA). In addition, the relationship between CNV and growth phenotype of cattle was studied. The experimental data indicate that the copy number of WBP1L was obviously correlated with heart girth of PN cattle (**P < 0.01), rump length (RL) and body weight (BW) of PN cattle (*P < 0.05), withers height (WH), RL, body length, chest depth and BW of JX cattle (*P < 0.05), WH of NGY cattle (*P < 0.05) and WH of JA cattle (*P < 0.05). It was proved that CNV of WBP1L gene could be used as molecular marker locus for genetic breeding of the above four cattle breeds.

Livestock plays a crucial role in food and nutrition security. However, livestock production accounts for 0.18 of global greenhouse gas emissions. India has one of the highest livestock densities globally, mainly produced under traditional systems. Specifically, the emission and particularly nitrogen losses from cattle in traditional systems cannot be ignored. Nitrogen emission is substantial when cattle roam free and waste is not collected or managed efficiently. This paper reviews the literature to piece together the available information on nitrogen emissions from cattle in India to synthesize the evidence, identify gaps and contribute to further understanding of the problem. At the same time, the paper highlights the solutions to reduce nitrogen pollution from cattle production in India. The main findings are that most cattle in India are not reared to provide meat protein. The implication is that reactive nitrogen per capita consumption is lower than most developed countries. However, there are substantial inefficiencies in feed conversion, feed nitrogen use and manure management in India. As a result, nitrogen losses and wastage are considerable in the different production systems. Furthermore, the review suggests that social, cultural and economic factors such as convergent social behaviour, urbanization, regulations, changing consumption patterns, the demand for cheap fuel sources, culture and religion influence the production systems and, consequently, the emissions from livestock. Suggested solutions to reduce nitrogen pollution from cattle production in India are improving livestock productivity, adopting better feeding, manure and pasture management practices and using behavioural nudges.

The bacterial community is important for shaping the fermentation characteristics of silage. This study aimed to investigate the fermentation characteristics, bacterial community and predicted functional characteristics of red clover (Trifolium pratense L.) silage. First-cutting red clover was collected at the early bloom stage, wilted for 5 h and then ensiled in 10 litre-capacity silos. Triplicate silos were sampled after 1, 3, 7, 15, 30 and 60 days of ensiling, respectively. The bacterial communities on days 3 and 60 were assessed through high-throughput sequencing technology, and 16S rRNA-gene predicted functional characteristics were analysed based on the KEGG using Tax4Fun. After 60 days of ensiling, red clover silage was fermented well, as indicated by high lactic acid (~77.3 g/kg DM), and low concentrations of butyric acid (~3.73 g/kg DM) and ammonia nitrogen (~55.0 g/kg TN). During the initial stage of ensiling, fructose and glucose were more preferred than sucrose for microbes. The predominant genus Lactococcus (0.542) on day 3 was replaced by Lactobacillus (0.553) on day 60. The metabolism of amino acids, energy, cofactors and vitamins was inhibited, while the metabolism of nucleotides and carbohydrates was enhanced after ensiling. High-throughput sequencing technology combined with 16S rRNA gene-predicted functional analyses revealed the differences during the early and late stages of red clover silage not only for distinct bacterial compositions but also for specific functional traits. Our results could provide a comprehensive insight into bacterial community and their functional profiles to further improve the silage quality.

The voluntary digestible organic matter intake (DOMI) of mature barley crops (Hordeum spp.) for sheep depends largely on straw quality. Direct measurement of DOMI is laborious; consequently, the research reported here evaluated indicator traits for improving barley straw DOMI by crop breeding. It hypothesized that some indicator traits for straw quality are heritable, facilitate genetic gain in DOMI, and reveal straw properties that constrain genetic gain. In 4 years, 32 genotypes of barley were grown at ICARDA, northern Syria, with no fertilizer in one year and supplementary irrigation in another. Indicator traits for predicting DOMI included in situ straw dry matter losses (DML) at nine incubation times (0–120 h), four parameters of the DML curve, seven laboratory tests, grain yield and straw yield. Heritability (h2) was highest for traits associated with indigestible cell wall constituents, including potential DML (h2 = 0.61), DML at 48–120 h of incubation (h2 = 0.48–0.58), and acid detergent fibre (ADF) (h2 = 0.41). Heritability was lower for DOMI itself (h2 = 0.24), neutral detergent fibre (NDF) (h2 = 0.20), and total Kjeldahl nitrogen (h2 = 0.17), and was lowest for DML at 6–18 h (h2 = 0.08–0.09) and the in situ parameters Lag and relative loss rate of slowly degradable DM (h2 ≤ 0.03). Correlations between indicator traits and DOMI tended to increase with heritability. Grain and straw yields were not correlated with DOMI; of these, only grain yield was heritable. In conclusion, genetic gain in barley straw nutritive value can be achieved by crop breeding under diverse growing conditions, using indicator traits associated with indigestible cell wall constituents.

With social network analysis, group structures of animals can be studied. However, underlying behavioural observations face problems of missing events or deviations between observers. The current study analysed the robustness of node-level network parameters based on tail-biting observations in pigs affected by missed events. Real observations of one observer were used as a gold standard to build true networks and to compare two sets of erroneous networks to them. The first set consisted of networks from different observers of the same data basis. The second set consisted of networks with a fixed error rate (random samples of the gold standard). The stability of the ranking order was used as an indication of accuracy (range 0–1; ≥0.49 good accuracy; ≥0.81 very good accuracy). Comparing observers with true networks yielded overall bad accuracy scores. Generally, outgoing network parameters (active: biting) provided better accuracy scores than ingoing network parameters (passive: being bitten). The results of sampled networks showed decreasing accuracy scores with increasing error rates. At the same error rate, longer observation periods yielded better accuracy scores. For sampled networks, differences between outgoing and ingoing network parameters were more distinct and local parameters (direct contacts) provided better accuracy scores than global parameters (direct and indirect contacts). Overall, sampled networks with 3/10 missed events yielded good to very good accuracy. As networks with more observations handle missed events better, studies of behavioural observations always need to evaluate the required accuracy and feasible workload. The current study gives insights in the accurate estimation of behavioural observations.

Phenylalanine (PHE) and to a lesser extent TYR are two commonly used amino acid tracers for measuring protein metabolism in a variety of species and tissues. The model examined in this paper was developed to resolve trans-organ and stable isotope dilution data collected from experiments with lactating dairy cows using these tracers. Two methods of solving the model, i.e. as two four-pool submodels, one representing PHE and the other TYR, or as an integrated eight-pool model, are investigated and the alternative solutions are contrasted. Solving the model as the two four-pool submodels rather than the integrated 8-pool model is preferred as the equations are slightly simpler and their application less susceptible to any compounding of measurement errors. The data used to illustrate the model were taken from experiments conducted to investigate the effects of high and low protein diets on the partitioning of PHE and TYR between milk protein synthesis and other metabolic fates by the mammary gland.