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The physiology of the sow mammary gland is qualitatively well described and understood. However, the quantitative effect of various biological mechanisms contributing to the synthesis of colostrum and milk is lacking and more complicated to obtain. The objective of this study was to integrate physiological and empirical knowledge of the production of colostrum and milk in a dynamic model of a single sow mammary gland to understand and quantify parameters controlling mammary gland output. In 1983, Heather Neal and John Thornley published a model of the mammary gland in cattle, which was used as a starting point for the development of this model. The original cattle model was reparameterized, modified, and extended to describe the production of milk by the sow mammary gland during lactation and the prepartum production of colostrum as the combined output of immunoglobulins (Ig) and milk. Initially, the model was reparameterized to simulate milk synthesis potential of a single gland by considering biological characteristics and empirical estimations of sows and piglets. Secondly, the model was modified to simulate more accurately the responses to changes in milk removal rates. This was done by linking the ejectable milk storage capacity to the number of secretory cells rather than being constant throughout lactation. Finally, the model was extended to include the prepartum synthesis of milk and the kinetics of Ig into and out of the mammary gland. A progressive capacity of secretory cells to synthesize milk was used to differentiate the time between the onset of milk synthesis and Ig transfer. Changes in maximum milk removal rate, duration of milk ejection, and nursing interval exerted a great impact on the modeled milk output. Changes by ±60% in one of these parameters were capable of increasing milk output by 28% to 39% during the first 4 wk in lactation compared with the reference parameterization. This suggests that the ability of the piglet to remove milk from the gland exerts a key control on milk synthesis during lactation. Modeling colostrum as the combined output of Ig and milk allowed to represent the rapid decline in Ig concentration observed during the first hours after farrowing. In conclusion, biological and empirical knowledge was integrated into a model of the sow mammary gland and constitutes a simple approach to explore in which conditions and to what extent individual parameters influence Ig kinetics and milk production., (© The Author(s) 2021. Published by Oxford University Press on behalf of the American Society of Animal Science. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Quantitative estimates of mammary nutrient inputs, outputs and metabolism in sows are scarce, despite being critical elements to identify parameters controlling milk synthesis central for the feeding of lactating sows. The objective of this study was to quantify the mammary gland input and output of nutrients as well as the intramammary partitioning of carbon and nitrogen with the purpose to identify mechanisms controlling mammary nutrient inputs, metabolism and milk production in lactating sows. A data set was assembled by integration of results from four studies. The data set included data on litter performance, mammary arterial-venous concentration differences (AV-difference) of energy metabolites and amino acids, and the contents of lactose, fat and amino acids in milk. Milk yield was estimated based on average litter size and litter gain, and mammary plasma flow (MPF) was estimated using the sum of phenylalanine and tyrosine as internal flow markers. The yield and composition of milk were used to estimate mammary nutrient output in milk, and MPF and AV-difference were used to estimate net mammary input of carbon and nitrogen and output of CO 2 . Carbon and nitrogen used for the synthesis of lactose, fat and protein in milk and CO 2 -yielding processes were represented in a static nutrient partitioning model. The origin of mammary CO 2 output was calculated using theoretical estimates of carbon released in processes supporting mammary synthesis of de novo fat, protein and lactose in milk, mammary tissue protein turnover and transport of glucose and amino acids. Results indicated that total input of carbon from glucose and lactate was partitioned into lactose (36%), fat (31%) and CO 2 -yielding processes (34%). Theoretical CO 2 estimates indicated that de novo fat synthesis, milk protein synthesis and mammary tissue protein turnover were the main processes related to mammary CO 2 production. More than 90% of mammary gland amino acid input was used for milk protein. The quadratic relationship between AV-difference and mammary input of essential amino acids indicated that both changes in AV-difference and MPF contributed to the regulation of mammary input of essential amino acids. The impact of the arterial supply of amino acids on mammary input may be greater for the branched-chain amino acids, arginine and phenylalanine than for other essential amino acids. In conclusion, relationships between input and output parameters indicate that AV-difference and MPF regulate mammary nutrient input to match the supply and demand of nutrients for the mammary gland., (Copyright © 2020 The Authors. Published by Elsevier B.V. All rights reserved.)

Background: Branched-chain amino acids (BCAAs), including L-leucine (L-Leu), L-isoleucine (L-Ile), L-valine (L-Val), and L-arginine (L-Arg), play a crucial role in mammary gland development, secretion of milk and regulation of the catabolic state and immune response of lactating sows. Furthermore, it has recently been suggested that free amino acids (AAs) can also act as microbial modulators. This study aimed at evaluating whether the supplementation of lactating sows with BCAAs (9, 4.5 and 9 g/d/sow of L-Val, L-Ile and L-Leu, respectively) and/or L-Arg (22.5 g/d/sow), above the estimated nutritional requirement, could influence the physiological and immunological parameters, microbial profile, colostrum and milk composition and performance of sows and their offspring. Results: At d 41, piglets born from the sows supplemented with the AAs were heavier (P = 0.03). The BCAAs increased glucose and prolactin (P < 0.05) in the sows' serum at d 27, tended to increase immunoglobulin A (IgA) and IgM in the colostrum (P = 0.06), increased the IgA (P = 0.004) in the milk at d 20 and tended to increase lymphocyte% in the sows' blood at d 27 (P = 0.07). Furthermore, the BCAAs tended to reduce the Chao1 and Shannon microbial indices (P < 0.10) in the sows' faeces. The BCAA group was discriminated by Prevotellaceae_UCG-004, Erysipelatoclostridiaceae UCG-004, the Rikenellaceae_RC9_gut_group and Treponemaberlinense. Arginine reduced piglet mortality pre- (d 7, d 14) and post-weaning (d 41) (P < 0.05). Furthermore, Arg increased the IgM in the sow serum at d 10 (P = 0.05), glucose and prolactin (P < 0.05) in the sow serum at d 27 and the monocyte percentage in the piglet blood at d 27 (P = 0.025) and their jejunal expression of NFKB2 (P = 0.035) while it reduced the expression of GPX-2 (P = 0.024). The faecal microbiota of the sows in Arg group was discriminated by Bacteroidales. The combination of BCAAs and Arg tended to increase spermine at d 27 (P = 0.099), tended to increase the Igs (IgA and IgG, P < 0.10) at d 20 in the milk, favoured the faecal colonisation of Oscillospiraceae UCG-005 and improved piglet growth. Conclusion: Feeding Arg and BCAAs above the estimated requirements for milk production may be a strategy to improve sow productive performance in terms of piglet average daily gain (ADG), immune competence and survivability via modulation of the metabolism, colostrum and milk compositions and intestinal microbiota of the sows. The synergistic effect between these AAs, noticeable by the increase of Igs and spermine in the milk and in the improvement of the performance of the piglets, deserves additional investigation. [ABSTRACT FROM AUTHOR]

Dietary supplementation with arginine (Arg) or glutamine (Gln) has been considered as an option to improve nursing performance in reproductive sows. This study investigated whether a low-level supplementation of Arg or Gln or a blend of both could modify milk nutrients and improve piglets' growth beyond weaning. Seventy-two multiparous sows were assigned to four groups: one group fed a control diet, three treatment groups fed the control diet supplemented with either 0.35% Arg, 0.35% Gln, or both, from day 108 of gestation until weaning at day 26 of lactation. Immediately after birth, the litters were cross fostered to 13 piglets and monitored until 2 wk after weaning. Sows body condition and litter growth were assessed. Colostrum and milk samples were collected for nutrient analyses. Plasma concentrations of insulin-like growth factor 1 (IGF-1) around weaning were determined in sows and two representative piglets per litter. Supplementing Gln or the combination of Arg and Gln had no effect on the parameters studied. Arg supplementation increased weaning weight, while decreasing the variation of piglet weights 2 wk after weaning. There was no correlation with plasma IGF-1 since the hormone was not altered in sows or piglets. The colostral concentration of fat tended to increase in the Arg-group, whereas protein, lactose, energy, and polyamine concentrations remained unaffected. Milk samples obtained on day 12 and 25 of lactation were not influenced by dietary treatment. The data indicate that there might be a window of opportunity, explicitly at the onset of lactation, for dietary intervention by maternal dietary Arg supplementation. [ABSTRACT FROM AUTHOR]

The introduction of precision feeding in sows depends on a precise estimation of its potential benefits. The goal of this study was to evaluate the effects of precision feeding and feed intake during gestation on gilt performances during two gestation cycles. Four isoenergetic treatments were compared: two constantconcentration feeding strategies (0.53% Lys DIS), one with constant feed intake (FF; flat feeding) and the other variable (BF; "bump feeding", with decreased feed intake before 90 days of gestation, then greater feed intake until parturition), and two precisionfeeding strategies based on the InraPorc model, one by parity (APP) and the other considering the body weight of the gilt at breeding (API). A total of 333 gilts were followed from breeding to weaning for two gestation and lactation cycles. Body weight and backfat depth were measured at breeding, 90 days of gestation, parturition, and weaning. Feed consumption was monitored daily. Litter variables were measured as birth and weaning weight, mortality, and overall gain. A mixed model was used to analyze differences between the four treatments using the sow as the experimental unit. Results showed that APP gilts gained more body weight during the gestation than FF gilts (65.1 vs 61.7 kg; P = 0.01) but no difference remained at the end of lactation (P > 0.10). Mobilization of backfat depth was more important during lactation in the APP group compared with FF and BF treatments (3.4 vs 2.9 mm; P = 0.03). BF and APP gilts had greater total birth litter weight than API gilts (400 g and 600 g greater, respectively), with FF gilts being intermediate (P = 0.02). However, the effect faded out with no difference on weaning weight and overall lactation gain weight (P > 0.10). The APP gilts had more weaned piglets than BF or FF gilts (+0.6 piglet, P = 0.01). During the second cycle, API sows gained more body weight during gestation than FF sows (58.8 vs 55.7 kg; P = 0.05). Yet, no significant difference was observed at the end of lactation. For the backfat depth, API sows had greater backfat depth during gestation than FF sows (1.83 vs 1.1 mm; P = 0.05) and a greater mobilization during lactation (2.68 vs 2.0 mm; P = 0.08). No effect was seen on litter mortality. In the same way, no significant effect was observed in the litter performances (P > 0.1). Initial results from this study seem to show a benefit of precision feeding for gilts, but with less effect for their second parity. However, no clear benefit was observed from the bump feeding strategy. [ABSTRACT FROM AUTHOR]

For a calculation of diets covering the pig's requirement and to avoid the waste of valuable nutrients without impact on zootechnical performance, the knowledge about the nutrient contents and their availability of the used feedstuffs, is a prerequisite. From the perspective of sustainability, higher usage of industrial by-products would be desirable to reduce the strong competition for food between human and pig nutrition. Hence, the aim of the present study was to test the effect of high amounts of wheat middlings in pig diets under consideration of the net energy system on zootechnical and slaughter performance of fattening pigs. Four dietary treatments differing in energy- (corn/barley/wheat middlings) and protein source (soybean meal /rapeseed meal / DDGS) were conducted, resulting in one high dietary crude protein treatment (soybean meal) and three reduced dietary crude protein treatments (rapeseed meal, low wheat middlings and high wheat middlings). Animals receiving the high wheat middlings diet showed a significantly lower daily feed intake (-13.6%) compared to the diet including rapeseed meal (p<0.0001). The rapeseed meal diet declined the feed to gain ratio (+8.6%) compared to the other treatments (p<0.05). The average daily gain was numerically greater for pigs receiving the high protein diet (+6.4%; p<0.1) compared to the other treatments. No differences between treatments were recorded for the investigated slaughter parameters. Specific slaughter parameters showed the highest Pearson correlation coefficient with the daily net energy intake. The observed differences regarding zootechnical performance parameters can be explained by unbalanced nutrient contents between the different experimental diets. The net energy system appears to be the most precise tool for an energy estimation of fattening pig diets. An accurate knowledge of the nutrient contents and availability of the feedstuffs is a prerequisite to optimize balanced diets for fattening pigs. [ABSTRACT FROM AUTHOR]