Development Of Feeding Strategies Research Articles

Early development and allometric growth patterns of Trachinotus ovatus (Linnaeus, 1758)

The early development of the golden pompano (Trachinotus ovatus), from embryogenesis through the larval and juvenile periods, is presented. The study findings have indicated that the eggs exhibited buoyancy in a salinity of 33, and featured a durable, transparent, yellowish spherical membrane, and contained a solitary non-adhesive oil droplet. At an incubation temperature of (28 ± 0.5) °C, and pH 7.8 ± 0.5, the embryos underwent seven periods of development for 26 stages, taking 25 h10. The total length of the newly hatched larvae was 2.03 ± 0.647 mm, transparent, followed by the larvae period 0–7 d after hatching (DAH), the juvenile period (7–17 DAH), and young fish period (after 17 DAH). The young fish showed similar morphology to adults, and the number of fin rays was as follows: dorsal 19–20, anal 17–18, ventral 1–5, pectoral 18–20, and caudal 17. The allometric growth of golden pompano was observed and different body segments exhibited different allometric growth patterns. The development of visual ability in juvenile golden pompano may precede the development of swimming ability. Therefore, the growth patterns can be a reference of organ differentiation sequence. These results have the potential to enhance the aquaculture techniques for golden pompano and provide a deeper understanding of their behavior and ecology in captive environments. Additionally, this information may serve as a reference for evaluating developmental phenotypes in cultured golden pompano and assist in the development of feeding strategies that align with their growth patterns, ultimately promoting greater efficiency and sustainability in aquaculture practices.

CHOmpact: A reduced metabolic model of Chinese hamster ovary cells with enhanced interpretability.

Metabolic modeling has emerged as a key tool for the characterization of biopharmaceutical cell culture processes. Metabolic models have also been instrumental in identifying genetic engineering targets and developing feeding strategies that optimize the growth and productivity of Chinese hamster ovary (CHO) cells. Despite their success, metabolic models of CHO cells still present considerable challenges. Genome-scale metabolic models (GeMs) of CHO cells are very large (>6000 reactions) and are difficult to constrain to yield physiologically consistent flux distributions. The large scale of GeMs also makes the interpretation of their outputs difficult. To address these challenges, we have developed CHOmpact, a reduced metabolic network that encompasses 101 metabolites linked through 144 reactions. Our compact reaction network allows us to deploy robust, nonlinear optimization and ensure that the computed flux distributions are physiologically consistent. Furthermore, our CHOmpact model delivers enhanced interpretability of simulation results and has allowed us to identify the mechanisms governing shifts in the anaplerotic consumption of asparagine and glutamate as well as an important mechanism of ammonia detoxification within mitochondria. CHOmpact, thus, addresses key challenges of large-scale metabolic models and will serve as a platform to develop dynamic metabolic models for the control and optimization of biopharmaceutical cell culture processes.

The Ingestion of Dietary Prebiotic Alternatives during Lactation Promotes Intestinal Health by Modulation of Gut Microbiota.

Palm kernel expeller (PKE), a by-product of palm oil extraction, contains higher amounts of fiber than corn and soybean meal, but offers low energy density, protein value, and amino acid (AA) composition, limiting its use for swine. Recently however, it was reported that dietary fiber has a positive effect on the gut microbiota of the host, and therefore it is necessary to study the effect of PKE feeding on the intestinal microbiota of swine. In this study, we investigated the effects of supplementation with PKE in lactation diets on the gut microbiota composition of lactating sows and their litters. A total of 12 sows were randomly assigned to two dietary treatment groups in a completely randomized design. The treatments were a diet based on corn-soybean meal (CON) and CON supplemented with 20% of PKE. Sow and piglet fecal samples were collected before farrowing, on days 7 and 28 (weaning) after farrowing, and on days 7 and 28 (weaning) after farrowing, respectively, to verify gut microbiota composition by pyrosequencing analysis. The beta-diversity result showed a significant difference only in weaning-stage piglets, but dietary PKE altered the gut microbiota in sows by increasing the abundance of Lactobacillus compared with CON. In piglets, dietary PKE decreased the abundance of opportunistic pathogen Proteus and increased the abundance of potentially beneficial bacteria, such as Prevotellaceae and Prevotella. Our results can be helpful in developing feeding strategies and support the beneficial effects of dietary PKE to improve the gut health of animals.

Novel findings in sea cucumber's digestive capacities: Enzymatic activities in the respiratory tree, implications for aquaculture

AbstractThere is a demand for proper feed and feeding strategies in the growing sea cucumber aquaculture. The digestive system of holothurians seems to increase nutrient assimilation through the respiratory tree (RT), but digestive functioning in this organ has not been investigated. This study evaluated the enzymatic activity of the cytosolic leucine alanine peptidase (leu‐ala) and acid phosphatase, the membrane‐linked aminopeptidase‐N (APN), the bile salt‐activated lipase, laminarinase (LAM), and β‐glycosidase (BGL), in the RT and segments of the digestive tract (DT; foregut, midgut, and hindgut) of adult Isostichopus badionotus. All enzymes, except LAM and BGL, exhibited comparable activity levels in the RT and the DT segments, but APN and BGL activities were significantly higher in the whole DT compared with those in RT, with high activity of leu‐ala in both organs. These results indicate a relevant role of the RT as an accessory organ in sea cucumber digestive physiology. Consequently, I. badionotus seems to be able to digest feeds from the water column through the RT, maximizing the use of available nutrients by luminal, intracellular, and apical membrane‐linked digestive modes. These findings expand the knowledge of sea cucumber digestive mechanisms, with implications for developing feeding strategies for all life stages in aquaculture.

High cell density culture of recombinant E. coli in the miniaturized bubble columns.

Miniaturized bubble columns (MBCs) can provide mass transfer characteristics similar to stirred tank bioreactors. In this study, a new application was developed for MBCs to investigate the effect of feeding strategy and medium type on the fed-batch culture of recombinant E. coli. The results showed that the exponential feeding strategy and defined M9 medium were more suitable to achieve the high cell density culture (HCDC). The maximum obtained cell concentration in exponential feeding strategy in the defined medium without induction, was at OD600 of 169, while glucose concentration was maintained under 2g/L. To the best of our knowledge, this cell concentration cannot be achieved in lab or pilot scale bubble columns. At the end of the process, adverse effect of the metabolic burden due to induction and mass transfer limitations decreased the obtained final cell concentration to OD600 of 116. Finally, a comparison of the results for fed-batch culture in the stirred tank bioreactor with those of the MBCs showed that their lower cell concentrations were due to the hydrodynamics limitations of MBCs. Yet, it was found that the MBCs are efficient tools in development of feeding strategies and evaluation of medium components for HCDC of recombinant E. coli.

The Relative Importance of Herbage Nutritive Value and Climate in Determining Daily Performance per Cow in a Pasture-Based Dairy Farm

The objective of this study was to assess the relative importance of herbage nutritive value (NV), herbage quantity and climate-related factors in determining daily performance per cow in a pasture-based dairy farm. Data on milk production, live weight, body condition score, weather, herbage NV and herbage quantity were regularly collected from August 2016 to April 2017 and from July 2017 to April 2018 at Dairy 1, Massey University, Palmerston North, New Zealand. Data were analyzed using multiple linear regression. Results indicated herbage NV was of higher relative importance in explaining the variation in performance per cow than herbage quantity and climate factors. The relative importance of the interaction between herbage metabolizable energy (ME) and crude protein (CP) on explaining variation in yields of milk, fat and protein was high (0.11 ≤ R2 ≤ 0.15). Herbage ME was of high relative importance in determining milk urea and body condition score, while neutral detergent fiber was a key driver of milk urea and liveweight (0.12 ≤ R2 ≤ 0.16). The quantity of herbage supplied at Dairy 1 might have been high enough to not limit cow performance. Developing feeding strategies aimed at improving the efficiency of cow feeding by exploiting the daily variation in herbage NV to better match supply and demand of nutrients may be useful to improve the overall performance per cow of pasture-based dairy farms.

ЭФФЕКТИВНОЕ КОРМЛЕНИЕ В ЖИВОТНОВОДСТВЕ

Lack of feed resources is a common problem that limits the development of livestock production. Various cataclysms, such as floods, droughts, lead to a shortage of food and feed. Among all cataclysms, drought is the main destructive natural disaster, leading to significant loss of vegetation. On average, about 30-40% of the cultivated area in areas affected by drought. Also, drought causes another type of loss when the growth rate of plants is limited. In such conditions in the regions, there is an acute shortage of feed and fodder. Therefore, there is a need to develop feeding strategies for keeping animals to ensure their development and productivity. Feeding strategies during times of scarcity depend on the specific conditions prevailing in any particular area. In general, the farmer must make decisions based on economics, knowledge of nutrition, availability of forage resources in difficult climatic conditions. Technological issues of feed preparation cannot be considered in isolation from the processes of digestion and metabolism in the animal body. Canned and treated with chemicals and other substances have specific nutritional properties and affect the animal's body, milk production and weight gain in different ways. However, if used incorrectly, they have a negative impact on the physiological state of the animal organism, productivity and viability. When characterizing feeds in this work, considerable attention is paid not only to the concentration of various substances in the feed, but also to their effect on the productivity of animals.

Longitudinal Investigation of the Gut Microbiota in Goat Kids from Birth to Postweaning.

Early microbial colonization in the gut impacts animal performance and lifelong health. However, research on gut microbial colonization and development in young ruminants, especially after weaning, is currently limited. In this study, next-generation sequencing technology was performed to investigate the temporal dynamic changes of the microbial community in the jejunum and colon of goats at 1, 7, 14, 28, 42, 56, 70, and 84 days (d) of age. As age increased, significant increases in microbial diversity, including the number of Observed OTUs and the Shannon Index, were observed in both the jejunum and colon. Regarding beta diversity, significant shifts in community membership and structure from d1 to d84 were observed based on both Bray–Curtis and Jaccard distances. With increasing age, dominant genera in the jejunum shifted from Lactobacillus to unclassified Ruminococcaceae, unclassified Lachnospiraceae and unclassified Clostridiales through starter supplementation, whereas colonic dominant genera changed from Lactobacillus and Butyricicoccus, within d1–d28, to unclassified Ruminococcaceae, unclassified Clostridiales and Campylobacter after solid diet supplementation. The linear discriminant analysis (LDA) effect size (LEfSe) analysis revealed bacterial features that are stage-specific in the jejunum and colon, respectively. In the jejunum and colon, a significantly distinct structure and membership of the microbiota was observed across all ages. The growth stage-associated microbiota in each gut compartment was also identified as a marker for biogeography. Our data indicate the temporal and spatial differences of the gut microbiota in goats are important for their performance and health. Early microbial colonization can influence microbial composition in later life (e.g., post-weaning phase). This study provides insights that the temporal dynamics of gut microbiota development from newborn to post-weaning can aid in developing feeding strategies to improve goat health and production.

Factors affecting milk yield and composition of Tunisian camels (Camelus dromedarius) over complete lactation.

This study aimed to investigate the milk production potential and the impact of nongenetic factors on milk yield and composition of Tunisian dromedary camels. Milk recording and sampling were carried out at monthly intervals over complete lactation for 3years from 95 camels reared in intensive and semi-intensive systems. The overall means of daily milk yield and fat, protein, total solids, and ash contents were 4.21 ± 1.98l/day, 2.45 ± 0.9%, 2.67 ± 0.74%, 10.75 ± 1.41%, and 0.85 ± 0.08%, respectively. The total milk yield was 1388.41 ± 575.46l/lactation for 11months of lactation. The daily milk yield increased regularly throughout lactation until it reached its peak in the 4th month postpartum and then decreased until the 17th month postpartum. The chemical components, except ash, followed an opposite trend to the milk yield. Their minimum contents were recorded during the 7th and 8th months postpartum, while the maximum levels were observed during the 17th month postpartum. Regarding seasonal variation, the highest daily milk yield was recorded during summer (June), whereas the lowest was found in winter (December). In contrast, the maximum and minimum contents of fat and protein were observed during winter (December) and summer (July), respectively. Similarly, total solids content was maximum in January and minimum in August. Parity had no effect on daily milk yield, while all chemical components were higher in milk from primiparous than multiparous camels. Calf sex and management system did not affect the milk yield and composition. These results are useful in order to develop feeding strategies and breeding programs for improving milk production.

A metabolic network-based approach for developing feeding strategies for CHO cells to increase monoclonal antibody production

Chinese hamster ovary (CHO) cells are the main workhorse in the biopharmaceutical industry for the production of recombinant proteins, such as monoclonal antibodies. To date, a variety of metabolic engineering approaches have been used to improve the productivity of CHO cells. While genetic manipulations are potentially laborious in mammalian cells, rational design of CHO cell culture medium or efficient fed-batch strategies are more popular approaches for bioprocess optimization. In this study, a genome-scale metabolic network model of CHO cells was used to design feeding strategies for CHO cells to improve monoclonal antibody (mAb) production. A number of metabolites, including threonine and arachidonate, were suggested by the model to be added into cell culture medium. The designed composition has been experimentally validated, and then optimized, using design of experiment methods. About a two-fold increase in the total mAb expression has been observed using this strategy. Our approach can be used in similar bioprocess optimization problems, to suggest new ways of increasing production in different cell factories.

The effect of supplementing pony diets with yeast on 2. The faecal microbiome

There is a need to develop feeding strategies to prevent the adverse effect of concentrate feeding in high-performance horses fed energy-dense diets aiming to maintain their health and welfare. The objective of this study is to determine the effect of a VistaEQ product containing 4% live yeast Saccharomyces cerevisiae (S. cerevisiae), with activity 5 × 108 colony-forming unit/g and fed 2 g/pony per day, on faecal microbial populations when supplemented with high-starch and high-fibre diets using Illumina next generation sequencing of the V3-V4 region of the 16S ribosomal RNA gene. The four treatments were allocated to eight mature Welsh section A pony geldings enrolled in a 4-period × 8 animal crossover design. Each 19-day experimental period consisted of an 18-day adaptation phase and a single collection day, followed by a 7-day wash out period. After DNA extraction from faeces and library preparation, α-diversity and linear discriminant analysis effect size were performed using 16S metagenomics pipeline in Quantitative Insights Into Microbial Ecology (QIIME™) and Galaxy/Hutlab. Differences between the groups were considered significant when linear discriminant analysis score was >2 corresponding to P < 0.05. The present study showed that S. cerevisiae used was able to induce positive changes in the equine microbiota when supplemented to a high-fibre diet: it increased relative abundance (RA) of Lachnospiraceae and Dehalobacteriaceae family members associated with a healthy core microbiome. Yeast supplementation also increased the RA of fibrolytic bacteria (Ruminococcus) when fed with a high-fibre diet and reduced the RA of lactate producing bacteria (Streptococcus) when a high-starch diet was fed. In addition, yeast increased the RA of acetic, succinic acid producing bacterial family (Succinivibrionaceae) and butyrate producing bacterial genus (Roseburia) when fed with high-starch and high-fibre diets, respectively. VistaEQ supplementation to equine diets can be potentially used to prevent acidosis and increase fibre digestibility. It may help to meet the energy requirements of performance horses while maintaining gut health.

Dynamics of serum phosphorus, calcium, and hormones during egg laying cycle in Hy-Line Brown laying hens

Understanding serum dynamic patterns of P, Ca, and P-Ca metabolism related hormones would help us in developing feeding strategies that can be used to reduce dietary inorganic P input and decrease P excretion in laying hens. In the current study, Hy-Line Brown laying hens (35-wk-old, n = 15) were fed with a corn-soybean meal-based commercial laying hen diet containing 0.24% non-phytate P, 3.59% Ca, 2,040IU/kg vitamin D3, 2,500 FTU/kg phytase, 2,636kcal/kg ME, and 15.9% crude protein. Blood samples from each laying hen were collected immediately after the first oviposition; 3, 6, 9, 12, 15, 18, and 21h after the first oviposition; and immediately after the second oviposition. As a result, after the first oviposition, serum P and Ca levels of the laying hens were gradually increased, peaked in 6h, and then gradually decreased all the way down until the second oviposition. Similarly, serum fibroblast growth factor 23 (FGF-23) level was gradually increased after the first oviposition, but peaked in 9h, and then gradually decreased all the way down until the second oviposition. Serum 1,25-dihydroxy-cholecalciferol [1,25(OD)2D3] level was linearly and quadratically decreased during the egg laying cycle we observed. The serum levels of parathyroid hormone, calcitonin, and alkaline phosphatase were erratically fluctuated during the egg laying cycle in patterns that are very different from that of serum P, Ca, FGF-23, and 1,25(OD)2D3. In conclusion, the result that serum FGF-23 peaked after serum P indicates that the dynamics in serum FGF-23 levels might be driven by serum P levels during the egg laying cycle.

Effects of dietary protein restriction followed by realimentation on growth performance and liver transcriptome alterations of lamb

The present study aimed to investigate the compensatory effect of early protein restriction followed by a realimentation on growth performance of lamb and to explore the transcriptomic changes in liver. Thirty-two lambs with an initial birth weight of 2.3 ± 0.20 kg that were weaned on day 15 were randomly divided into two groups. The lambs were fed a basal diet with normal protein level (NPL, protein level in the milk replacer and starter, 25 and 21%, respectively) or low protein level (LPL, protein level in the milk replacer and starter, 19 and 15%, respectively) from 15 to 60 d, after which all lambs consumed the same diet with a normal protein level from 61 to 90 d. Protein restriction led to a significant decrease in average daily gain (ADG), body weight and liver weight (P < 0.05). Transcriptome analysis showed that 302 or 12 differentially expressed genes (DEGs) were identified during the restriction or recovery periods, respectively (P < 0.05). The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that DEGs enriched in nutrient metabolism and antioxidant capacity were down-regulated, while vessel development and immunity response-related genes up-regulated. The genes involved in metabolism of tyrosine were still down-regulated in the realimentation phase. Studies in this area indicated the accelerated growth effect of early protein restriction followed by a realimentation on growth performance of lambs and explored the transcriptomics change of liver which can help to develop feeding strategies to optimize the use of feedstuffs and in providing a new perspective for the study of early nutrition and epigenetics in later life.

Family Food Environment and Child Eating Behavior in a Private School of Abu Dhabi

Aim: Dietary habits developed during childhood and continued through adulthood. Children’s eating behaviours should be monitorining to avoid possible nutritional deficiencies which have been found to be strongly related to the development of future disease such as obesity, diabetes type 2 and others. The main aim of this study is to explore the relationship between family food environment and the eating behavior during dinnertime among children aged 4 to 6 years old in Abu Dhabi. A cross-sectional study was carried out that examined the relationship between family food environment and child’s eating behaviour around dinnertime.Methods: 61 families participated in the study with their children aged 4-6 years old from a private school. They completed a questionnaire that included questions about demographics, eating behaviour and food environment.Results: 82% of the mothers were reported to be responsible for feeding the children. Most of the families had dinner together three or more times a week. Half of the children got a high score in the child’s eating behaviour scale, indicating that they had positive eating behaviour. The results also showed that children of highly educated mothers were more likely to have positive eating behaviour, compared to children of mothers with lower education (p &lt; .05). There was a significant positive correlation between modelling of eating and child eating behaviour ( Pearson’s r = .56, p &lt; .01), and a significant negative correlation between pressure to eat and child eating behaviour (Pearson’s r = -.35, p &lt; .01).Conclusion: This study is in line with other studies showing that aspects in the family food environment have an influence on eating behaviour of children. Educating parents on food environment and its impact on child behaviour is crucial in order to make them able to develop feeding strategies most likely to benefit children's’ health.

사료 내 항생제 대체 첨가제를 이용한 육계의 사양관리

Antibiotics in the diets for poultry were not only used for avoiding and (or) control bacterial infections but for promoting growth of the birds. However, there has been massive concerns of negative effects of antibiotics on human health such as development of antibiotics-resistance bacteria and (or) genes. Subsequently, some of countries (i.e., European Union member of country and South Korea) banned the use of antibiotics as growth promoters in the diets for livestock industries in 2006 and 2011, respectively. Thus, it has become important to develop feeding strategies and feed additives to control and reduce the occurrence of diseases in livestock without using in-feed antibiotics. In this review, therefore, it is attempted to gather information with respect to (1) understanding the digestive physiology and (2) knowledge pertaining to interaction linking feed additives and its physiological and metabolic responses in broiler chickens.

Revisiting Verhulst and Monod models: analysis of batch and fed-batch cultures.

The paper re-evaluates Verhulst and Monod models. It has been claimed that standard logistic equation cannot describe the decline phase of mammalian cells in batch and fed-batch cultures and in some cases it fails to fit somatic growth data. In the present work Verhulst, population-based mechanistic growth model was revisited to describe successfully viable cell density (VCD) in exponential and decline phases of batch and fed-batch cultures of three different CHO cell lines. Verhulst model constants, K, carrying capacity (VCD/ml or μg/ml) and r, intrinsic growth factor (h(-1)) have physical meaning and they are of biological significance. These two parameters together define the course of growth and productivity and therefore, they are valuable in optimisation of culture media, developing feeding strategies and selection of cell lines for productivity. The Verhulst growth model approach was extended to develop productivity models for batch and fed-batch cultures. All Verhulst models were validated against blind data (R(2)>0.95). Critical examination of theoretical approaches concluded that Monod parameters have no physical meaning. Monod-hybrid (pseudo-mechanistic) batch models were validated against specific growth rates of respective bolus and continuous fed-batch cultures (R(2)≈0.90). The reduced form of Monod-hybrid model CL/(KL+CL) describes specific growth rate during metabolic shift (R(2)≈0.95). Verhulst substrate-based growth models compared favourably with Monod-hybrid models. Thus, experimental evidence implies that the constants in the Monod-hybrid model may not have physical meaning but they behave similarly to the biological constants in Michaelis-Menten enzyme kinetics, the basis of the Monod growth model.

Long-term growth of male and female Bali cattle fed Sesbania grandiflora

This study examined the long-term growth of male and female Bali cattle (Bos javanicus) fed a diet consisting solely of Sesbania grandiflora (sesbania) or sesbania with rice bran. Twelve male (71.6 ± 2.2 kg mean liveweight and standard error of the mean; LW) and six female (80.3 ± 2.8 kg LW) weaned Bali cattle, ~6 months of age at the commencement were used in this experiment. LW, wither height (WH), hip height and chest circumference (girth) were measured from ~6 to 27 months of age. Dry matter intake and the concentration of glucose, urea and insulin-like growth factor-1 in the plasma were measured at ~9, 18 and 27 months of age. There was no difference in LW gain of male and female Bali cattle between 6 and 18 months of age but males had a greater average LW gain (0.40 kg/day) than females (0.22 kg/day) between 18 and 27 months of age. Overall females displayed a curvilinear growth path in LW, WH and girth between 6 and 27 months of age, while males displayed a linear growth path in LW and girth but curvilinear in WH over the same age. Dry matter intake did not differ with stage of development or between male and female cattle. The plasma urea concentration declined in male Bali cattle with stage of development but was constant in female cattle across the experiment. The concentration of insulin-like growth factor-1 in the plasma increased with age and tended to be greater in male (268 ng/mL) than female (222 ng/mL) Bali cattle. In conclusion, Bali cattle display sexual dimorphism in growth after ~18 months of age, which is important to consider when developing feeding strategies across the full growth path.

Challenges in ration formulation in pasture-based milk production systems

The profitability of temperate dairy systems in southern Australia and New Zealand is underpinned by the efficient use of the home-grown feed-base and purchased supplements. While there are well established principles on which to devise nutritionally balanced rations for ruminants, it is evident that in grazing systems the variable supply of nutrients from forage often results in suboptimal performance compared with predicted responses. This review discusses the key factors likely to directly affect responses to supplementation in grazing systems, namely pasture supply, nutritive characteristics and intake, feeding systems, substitution, associative effects and nutrient synchrony. Intake is the primary driver for metabolisable energy (ME) and nutrient supply and uncertainties on the actual ME and nutrients supplied by pasture will remain due to variability within and between pasture types and within paddocks. It is suggested that improvements in ration formulation will require a better understanding of the kinetics of intake and digestion within the rumen and of nutrients supplied to the tissues from grazed pasture with and without supplements. Research which clearly elucidates which mechanism or mechanisms determine substitution rates with concentrate and forage supplements would be valuable. Such knowledge could also be used to develop feeding strategies that result in a reduction in the degree of substitution and, in turn, lead to higher DM and ME intake compared with existing feeding practices. This in turn would lead to a better understanding of associative effects and nutrient synchrony with benefits in better design of rations and feed-use efficiency.

Exigencias y modelación de la cinética metabólica de calcio y fósforo en ovinos: revisión

En la actualidad, la producción animal debe ser realizada buscando minimizar su impacto negativo sobre el ambiente. El fósforo es un mineral esencial para la vida animal, por lo tanto debe ser ofrecido en cantidades adecuadas para los animales logren cumplir con las metas productivas establecidas. Sin embargo, es necesario cuidar que la oferta dietética del mineral no sea superior a la necesidad, para evitar excesos en las cantidades excretadas por las heces, que son la principal vía para eliminar el mineral del organismo en los rumiantes, y evitar efectos contraproducentes al ambiente. En relación a las exigencias, tanto de calcio como de fósforo, existen varios modelos de predicción que están siendo usados. Recientemente los modelos más antiguos han sido modificados, intentando disminuir la oferta del mineral. La técnica de la modelación, usada para estudiar la cinética metabólicas de estos minerales, está siendo permanentemente evaluada, y estudios recientes permiten conocer más detalles acerca del metabolismo de estos minerales. A pesar de las diferencias entre algunos modelos, resulta importante su aplicación para formular estrategias de alimentación que permitan optimizar la nutrición mineral y disminuir la excreción de minerales al ambiente, además de mejorar la economía de las empresas de producción animal.

Feeding Unprotected CLA Methyl Esters Compared to Sunflower Seeds Increased Milk CLA Level but Inhibited Milk Fat Synthesis in Cows.

An experiment was conducted to compare the effect of the same amount of 18:2 offered either as 18:2n-6 or as a mixture of unprotected 18:2c9t11 and 18:2t10c12 on feed intake, milk components as well as plasma and milk fatty acid profile. Fifteen cows were blocked by milk yield and milk fat percentage and within block assigned randomly to 1 of 3 treatments (n = 5). Each cow passed a 12-d adjustment period (AP) on a basal diet. After the AP cows received 1 of 3 supplements during an 18-d experimental period (EP). The supplements contained either 1.0 kg ground sunflower seeds (S), 0.5 kg conjugated linoleic acid (CLA)-oil (C) or 0.75 kg of a mixture of ground sunflower seeds and CLA-oil (2:1; SC). All 3 supplements contained the same amount of 18:2 either as CLA (∑18:2c9t11+18:2t10c12, 1:1) or as 18:2c9c12. During the last 2 d of AP and the last 4 d of EP feed intake and milk yield were recorded daily and milk samples were collected at each milking. Blood samples were collected from the jugular vein on d 11 of AP and d 15 and 18 of EP. The 18:2 intake increased in all treatments from AP to EP. Regardless of the amount of supplemented CLA, the milk fat percentage decreased by 2.35 and 2.10%-units in treatment C and SC, respectively, whereas in the treatment S the decrease was with 0.99%-unit less pronounced. Thus, C and SC cows excreted daily a lower amount of milk fat than S cows. The concentration of trans 18:1 in the plasma and the milk increased from AP to EP and increased with increasing dietary CLA supply. While the concentration of 18:2c9t11 and 18:2t10c12 in the plasma and that of 18:2t10c12 in the milk paralleled dietary supply, the level of 18:2c9t11 in the milk was similar in C and CS but still lower in S. Although the dietary concentration of CLA was highest in treatment C, the partial replacement of CLA by sunflower seeds had a similar inhibitory effect on milk fat synthesis. Comparable 18:2c9t11 levels in the milk in both CLA treatments implies that this isomer is subjected to greater biohydrogenation with increasing supply than 18:2t10c12. The fact that unprotected 18:2t10c12 escaped biohydrogenation in sufficient amounts to affect milk fat synthesis reveals opportunities to develop feeding strategies where reduced milk fat production is desirable or required by the metabolic state of the cow.