Myrthe S. Gilbert

Dairy farming systems are evolving toward more sustainable production practices, and these changes may enhance genotype-by-environment interaction (G × E). Analyses of G × E would benefit from detailed information on feeding practices, however, such data are rarely incorporated, largely because they are not routinely available. This study investigated G × E for milk production traits using detailed information on feeding practices using reaction norm models, and assessed differences between organic and conventional farming systems using character state models. Environmental descriptors were available for 973 Dutch dairy farms over the period 2016-2021. These descriptors included the proportion of dietary concentrate (% of diet DM), nitrogen use efficiency (NUE, %), phosphorus use efficiency (PUE, %), and dietary net energy for lactation (NE_L, MJ/kg DM). For comparison, we also included the more commonly used descriptor herd average milk yield per cow (HMY, kg/cow/year). The data set included 101,979 first lactation milk production records, of which 6,094 originated from organic farms and 95,885 from conventional farms. Heritability (±SE) of milk yield was 0.36 ± 0.04 in organic and 0.44 ± 0.01 in conventional farming systems. Heritability of milk yield increased from 0.17 ± 0.02 when feeding 13.0% to 0.54 ± 0.01 when feeding 43.0% dietary concentrate (DM basis). Similarly, heritability of milk, fat, and protein yield increased with increasing NUE, PUE, NE_L and HMY. In our study, the residual variance was assumed constant across environmental descriptors; therefore, the increase in heritability was due to an increase in genetic variance. Heritability of milk fat and protein content and somatic cell score showed limited response to changes in environmental descriptors. Genetic correlations between the same trait across environmental descriptors were generally near unity, except for yield traits across HMY levels. These results indicate G × E arising from scaling effects, but provide little evidence of genotype re-ranking across environments. Ignoring scaling effects leads to biased EBVs for environments deviating from the average. Multivariate analyses that include traits beyond milk production are needed to quantify the potential implications for selective breeding programs.

Enhancing feed resource efficiency and cows' ability to digest fiber is essential for advancing a circular food system that reduces feed-food competition and the environmental impact of dairy farming. This study investigated associations of feed efficiency (FE) and residual feed intake (RFI) with apparent total-tract digestibility (ATTD) of DM, OM, NDF, gross energy (GE) and nitrogen (N) in 480 cows across 4 Dutch commercial farms. In addition, associations of milk N use efficiency (NUE) and residual N intake (RNI) with N partitioning variables were analyzed. Three farms were visited twice, one farm once, resulting in 7 sampling sessions. Individual feed intake was recorded using automatic feed intake bins. During each session, milk yield and composition were determined, and spot samples of urine and feces were collected at 6 4-h intervals over 4 consecutive days, covering all 4-h periods within a 24-h cycle. Creatinine and acid-insoluble ash contents were analyzed and used to estimate urinary and fecal output, respectively. Rumen microbial N supply was estimated using purine derivative excretion in urine. On average, cows had a parity of'1.5 ± 0.74, were 138 ± 52.5 DIM, produced 38.8 ± 6.82 kg/d of fat- and protein-corrected milk, and had a DMI of 24.0 ± 3.40 kg/d, FE of 1.62 ± 0.189, and NUE of 306 ± 39.8 g/kg. The diet contained on average 181 ± 9.8 g/kg DM CP and 308 ± 27.4 g/kg DM NDF. In general, at the inter-individual level, higher FE was associated with greater nutrient digestibility; however, interactions with session were often observed, indicating that these associations varied across sampling sessions. In addition, higher NUE or lower RNI were generally associated with greater microbial N efficiency, reduced N retention, and a shift in N excretion from feces to urine, again depending on sampling session. These patterns were associated with the dietary CP to NE_L ratio, with lower ratios associated with more efficient use of digestible N and reduced urinary N excretion. The frequent interactions between variables and sampling session demonstrate that efficiency and N partitioning metrics are context-dependent, emphasizing the need to account for farm- and time-specific conditions when developing strategies to improve nutrient use efficiency and reduce the environmental impact of dairy production.

Bovine respiratory disease is a major multifactorial health issue in calves. Our objective was to evaluate the effects of galacto-oligosaccharide supplementation, microbiota transfer, and their interaction on lung health and performance of calves. A total of 180 male Holstein-Friesian calves at 18 ± 3.6 d of age received 1 of 4 treatments according to a 2 × 2 factorial design for 8.5 wk (period 1). Calves received galacto-oligosaccharides (GOS) via the milk replacer or not (CON) and received a microbiota transfer (MT) or not (MOCK). The MT strategy consisted of a combination of an oral rumen microbiota transfer and a fecal microbiota transfer supplied orally and rectally. The MT or MOCK procedure was applied 3 times in the first week after arrival and was repeated within a week after a group antimicrobial treatment. Clinical health was scored weekly, and BW was measured every 4 wk. Bronchoalveolar lavage fluid (BALF) and blood samples were collected biweekly from a subset of calves (n = 108). After period 1, all calves received the same control milk replacer for 4 wk (period 2), during which performance and clinical health were measured. Clinical scores increased from wk 1 to 3, and BALF IL-8 concentrations increased with time in period 1. This high infection pressure resulted in a requirement of 6 group antimicrobial treatments (supplied to all calves). Supplementation with GOS increased the ADG adjusted to equal solid feed intake (+27 g/d) in period 1 and tended to increase it (+45 g/d) in period 2. Supplementation with GOS decreased clinical scores in wk 1 and 3 (in the absence of MT) but tended to increase it in wk 6. Furthermore, GOS tended to decrease rectal temperature in period 2. Cytokine concentrations in BALF and blood were not affected by GOS, but the percentage of lymphocytes in BALF was increased by GOS, accompanied by a decrease in lymphocyte and an increase in neutrophil percentage in plasma. Microbiota transfer reduced plasma white blood cell concentration, related to a relative decrease in plasma neutrophils. Microbiota transfer reduced the percentage of BALF lymphocytes, and in wk 5, it also reduced the BALF concentration of TNFα. However, MT did not affect performance. At the start of period 2, MT even increased clinical scores in the absence of GOS, resulting in a higher individual antimicrobial treatment supply to MT calves in period 2, ultimately reducing the rectal temperature of MT calves at the end of period 2. Hardly any interactions between GOS and MT occurred, suggesting the absence of an additive relation. In conclusion, GOS improved performance and even tended to increase it after GOS supplementation ended, but this was not related to lung health. Microbiota transfer affected some inflammatory parameters, pointing toward reduced systemic and respiratory inflammation, but this was not reflected in clinical health, which even decreased in the carry-over period.

In the agricultural sector, antibiotics have been used to improve swine growth performance. This application is banned nowadays, due to increased risk of antibiotic resistance. In piglets this results in a higher prevalence of post-weaning diarrhoea, deteriorating both animal health and performance. Our goal was to find a metabolite signature separating piglets with low faecal consistency score (FCS) from piglets with normal faecal consistency and determine which pathways were enriched in this signature. By using direct infusion mass spectrometry on blood spots, we built machine learning (ML) models that aimed to differentiate between low and normal FCS. To test the general predictive capability of these models, we applied a Leave-One-Country-Out (LOCO) strategy for cross validation. Our second approach after LOCO was finding the optimal number of features to include in a feature-reduced model. To determine the order in which features were to be eliminated, we ranked them based on a combination of t-test and fold-change significance scores. Enrichment analysis using mummichog was used to gain insights into the final signature set of m/z values found using this ranking and ML models. Models trained both using all countries and leaving out specific countries from training showed a limited ability to predict FCS category. Furthermore, the LOCO results were mixed, with some countries showing a predictive signal present in the data, but others with predictive capability that was no better than random. Signature analysis using t-test and fold-change results did not result in any KEGG pathways that were enriched in this signature as compared to random. Using these methods, we could predict the FCS category to a limited degree. Although no common signature for low faecal consistency could be determined using this method, given that some countries showed more reliable LOCO results, further analysis into specifically the samples from those countries could be a valuable next step. No metabolite signature enriched in changes to KEGG pathways was found in the data using the combined t-test and fold-change analysis ranking method. We have shared the data with the community through the MetaboLights repository.

Lipopolysaccharide (LPS) challenges are commonly used in animal studies as a model for infection with gram-negative bacteria and innate immune activation. We used a low-dose LPS challenge for evaluating interindividual variation in innate immune responses in calves. This was part of a larger study aimed at predicting interindividual variation in feed efficiency in veal calves by variation in feeding motivation, digestion, metabolism, immunology, and behavioral traits. However, due to unexpected high mortality, this LPS challenge was performed in 32 calves rather than in 130 calves, which was initially intended in that larger study, and the 32 calves subjected to the LPS challenge were removed from that larger study. The objective of this short communication is to report the effects of a low-dose LPS challenge in those 32 calves and to examine whether the high variation in calves' responses to LPS could be explained by parameters related to feeding motivation, digestion, behavior, and immunology measured in early life. Thirty-two male Holstein-Friesian calves of Dutch origin were intravenously injected with LPS (0.05 mu g/kg of body weight) at an age of 72 +/- 0.6 d. Rectal temperature and respiratory frequency were recorded before injection and every hour after injection up to 6 h. In the 8 wk before the LPS challenge, measurements were performed related to general health, feeding motivation, digestion, behavior, and immunity. Following LPS administration, 3 calves died of shock, a fourth calf was euthanized because of severe symptoms of shock and 3 other calves were treated with corticosteroids to counteract observed symptoms of shock. Within the group of 25 relatively mild-responding calves, large interindividual variation in clinical responses to LPS was observed. The maximum increase in rectal temperature varied from 0.6 to 1.9 degrees C and averaged 1.2 +/- 0.39 degrees C (coefficient of variation was 32%). The maximum increase in respiratory frequency varied from 16 to 132 bouts/min and averaged 60 +/- 28 bouts/min (coefficient of variation was 48%). Little differences were found in early-life measurements between the 7 heavy and 25 mild responders, although heavy responders tended to have a better umbilical hernia score, and had a lower score in a human approach test (i.e., were less reactive) and lower presence of fecal pathogens. The maximum increase in rectal temperature correlated negatively with blood hemoglobin concentration at arrival of the calves at the facilities (r = -0.59) and in wk 4 (r = -0.53). The maximum increase in respiratory frequency correlated negatively with fecal color score (r = -0.43) and positively with fur score in wk 5 (r = 0.50). Overall, mortality (12.5%) and variation in clinical response was high after a low-dose LPS challenge in clinically healthy calves and some hematological and health measurements in early life were related to the clinical response of calves to LPS.

Our objective was to determine the effects of nondigestible oligosaccharides (NDO) on lung health and performance. Three hundred male Holstein-Friesian calves aged 18.0 ± 3.6 d received 1 of 6 treatments for 8.5 wk (period 1). Treatments included a negative control (CON), galacto-oligosaccharides (GOS) administered as a spray via the nose once daily (SPR), GOS administered via the milk replacer (MR) at 1% (GOS-L) and 2% (GOS-H), fructo-oligosaccharides administered via the MR at 0.25% (FOS) and a combination of GOS and fructo-oligosaccharides administered via the MR at 1% and 0.25%, respectively (GOS-FOS). Milk replacer was fed twice daily. Feeding levels were equal between calves and increased progressively in time. Body weight was measured every 4 wk and clinical health was scored weekly. Blood and broncho-alveolar lavage fluid (BALF) samples were collected bi-weekly from a subset of calves (n = 120). After period 1, all calves received the same control MR for 18 wk until slaughter (period 2), during which general performance and clinical health were measured. Generally, infection pressure was high, with clinical scores and BALF proinflammatory TNFα concentrations increasing with time in period 1, which resulted in a high number of required group antimicrobial treatments (6 group antimicrobial treatments in 13 wk, supplied to all calves). Average daily gain adjusted to equal solid feed intake was increased for GOS-L (+61 g/d) compared with CON calves from experimental wk 1 to 5. Plasma white blood cell concentration tended to be lowered by GOS-L, plasma IL-8 concentration was reduced by all orally supplemented NDO, plasma IL-6 was reduced by all NDO treatments except GOS-FOS and plasma IL-1β was reduced by all NDO treatments compared with CON, although this differed per time point for SPR. The neutrophil percentage in BALF was reduced by GOS-L in wk 6, which was associated with a relative increase in macrophages. The BALF concentration of TNFα and IL-8 was reduced or tended to be reduced by GOS-L and GOS-H, while IL-6 was or tended to be reduced by SPR, GOS-L, GOS-H, and GOS-FOS, and IL-1β was reduced by SPR, GOS-L, GOS-H, and FOS. Generally, feeding the combination of GOS and FOS was not more effective than feeding GOS or FOS alone, because feeding GOS-FOS resulted in higher concentrations of plasma and BALF cytokine and chemokine concentrations compared with feeding GOS-L alone, and resulted in higher plasma cytokine concentrations compared with feeding FOS alone. None of the BALF and plasma cytokine or chemokine concentrations differed between the GOS-L and GOS-H treatment. Performance and clinical scores in period 2 did not differ among treatments. Altogether, all tested NDO reduced systemic and lung inflammation in calves under high natural infection pressure and for GOS-fed calves, this increased performance during the first 4 wk. Combining GOS and FOS did not have a synergistic effect. The intranasal administration of GOS also lowered systemic and lung inflammation, but tended to negatively affect performance. Overall, this study demonstrates the potential of NDO to alleviate systemic and respiratory inflammation in calves.

Emerging antimicrobial-resistant pathogens highlight the importance of developing novel interventions. Here, we investigated the anti-inflammatory properties of Fructo-oligosaccharides (FOS) in calf lung infections and in airway epithelial cells stimulated with pathogens, and/or bacterial components. During a natural exposure, 100 male calves were fed milk replacer with or without FOS for 8 weeks. Then, immune parameters and cytokine/chemokine levels in the bronchoalveolar lavage fluid (BALF) and blood were measured, and clinical scores were investigated. Calf primary bronchial epithelial cells (PBECs) and human airway epithelial cells (A549) were treated with Mannheimia haemolytica, lipopolysaccharides (LPS), and/or flagellin, with or without FOS pretreatment. Thereafter, the cytokine/chemokine levels and epithelial barrier function were examined. Relative to the control (naturally occurring lung infections), FOS-fed calves had greater macrophage numbers in BALF and lower interleukin (IL)-8, IL-6, and IL-1β concentrations in the BALF and blood. However, FOS did not affect the clinical scores. At slaughter, FOS-fed calves had a lower severity of lung lesions compared to the control. Ex vivo, FOS prevented M. haemolytica-induced epithelial barrier dysfunction. Moreover, FOS reduced M. haemolytica- and flagellin-induced (but not LPS-induced) IL-8, TNF-α, and IL-6 release in PBECs and A549 cells. Overall, FOS had anti-inflammatory properties during the natural incidence of lung infections but had no effects on clinical symptoms.

In pigs, high protein diets have been related to post-weaning diarrhoea, which may be due to the production of protein fermentation metabolites that were shown to have harmful effects on the intestinal epithelium in vitro. In this review, we discussed in vivo effects of protein fermentation on the microbial composition and their protein catabolic activity as well as gut and overall health. The reviewed studies applied different dietary protein levels, which was assumed to result in contrasting fermentable protein levels. A general shift to N-utilisation microbial community including potential pathogens was observed, although microbial richness and diversity were not altered in the majority of the studies. Increasing dietary protein levels resulted in higher protein catabolic activity as evidenced by increased concentration of several protein fermentation metabolites like biogenic amines in the digesta of pigs. Moreover, changes in intestinal morphology, permeability and pro-inflammatory cytokine concentrations were observed and diarrhoea incidence was increased. Nevertheless, higher body weight and average daily gain were observed upon increasing dietary protein level. In conclusion, increasing dietary protein resulted in higher proteolytic fermentation, altered microbial community and intestinal physiology. Supplementing diets with fermentable carbohydrates could be a promising strategy to counteract these effects and should be further investigated.