Journal Articles
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Item A comparative study between milk- and serum-based antibody detection assays for Johne's disease in New Zealand dairy cattle(Elsevier B.V., 2025-08-27) Venkatesh KM; Lopez-Villalobos N; Gupta SK; Udy GB; Laven R; Chiu S-J; Bugde P; Furuya Y; Dukkipati VSRDairy cattle are affected by Johne's disease. It is caused by Mycobacterium avium subspecies paratuberculosis (MAP). Suboptimal diagnostic tests add more to the productivity loss resulting from this disease. Agreement between and within different commercial kits is crucial in the decision-making process of disease surveillance programmes. This study compared two ELISAs, that is, Johne's disease commercial antibody detection kits (A and B), using milk and serum samples from New Zealand dairy cattle. These results were also compared with a subset of faecal PCR results. Five scenarios were considered for the comparison of ELISA tests. The point estimates of kappa coefficients (k) between the serum (0.84–0.94) assays were higher than the milk assays (0.59–0.82). The point estimates of kappa coefficients between serum and milk ELISA outcomes were higher for kit B (k = 0.79–0.86) than for kit A (k = 0.55–0.79). The point estimates of kappa coefficients between the ELISA and faecal PCR outcomes varied between 0.43 and 0.74. ELISA tests had point estimates of sensitivity ranging from 0.67 to 0.88 and specificity from 0.62 to 0.93, relative to the faecal PCR test. Results suggest that serum provides a better choice of sample type when both commercial kits A and B are used for Johne's disease surveillance of dairy cattle in New Zealand. Milk assays can be cost-effective to diagnose MAP-positive animals; kit B can be best suited for New Zealand conditions, provided the repeatability of the results is validated.Item Candidate gene search for milk production and composition, milk coagulation properties, and milk protein profile in dairy sheep from a New Zealand flock(Taylor and Francis Group, 2025-07-11) Marshall AC; Lopez-Villalobos N; Vigolo V; Marchi MD; Loveday SM; Weeks M; McNabb WThe objective of this study was to perform genome-wide association analysis and thus search for candidate genes for milk production and composition, milk coagulation properties (MCP), and milk protein profile in dairy sheep from a New Zealand flock. After quality control, 45,801 single nucleotide polymorphisms (SNPs) were included in the analysis, 147 ewes, and 470 individual records. A total of 87 SNPs and 55 candidate genes were found across Ovis aries autosomes (OAR) 2, 3, 6, 16, 18, 20, 25, and 26. Of particular importance, were the candidate genes PDZRN4 for milk yield, and BMP2K for contents of αs1- and αs2-caseins. No SNPs were found in the casein genes, LALBA or PAEP. Only one SNP was significant for MCP, and overall, the genetic architecture of MCP was similar to that of ratio of casein to calcium, pH, lactose, and the ratio of casein to protein. Further studies with larger flocks and with genomic imputation are required to validate the findings of this study before incorporating markers or genes into breeding programmes.Item Evaluation of empirical and mechanistic models and sampling intervals to model the lactation curves of F1 dairy sheep(Springer Nature B V, 2025-03-14) Guevara L; Lopez-Villalobos N; Pollott GE; Albarrán-Portillo B; Fernandes AM; Salinas-Martínez JA; Angeles-Hernandez JCRecently Latin American countries have developed a dairy sheep industry with an increasing number of specialized dairy-sheep flocks. The objective of this study was to evaluate the goodness of fit of empirical and mechanistic models and sampling interval to model the lactation curve of F1 dairy sheep with different shape of lactation curves in an intensively managed flock of the central highlands of Mexico. A total of 4,494 weekly (7D) test day records (TDR) from 156 lactations were analyzed. Three datasets were generated from the original 7D data set, setting TDR at different sampling intervals: 14 (14D), 21 (21D) and 28 (28D) days. Lactation curves were fitted using two empirical (Wood and Wilmink) and two mechanistic models (Dijkstra and Pollott). The parameters of the empirical and mechanistic models were estimated using the iterative non-linear curve fitting procedure in R. The results showed that the estimation of TMY was not affected by the sampling interval. However, the estimation of peak yield (PY) and day at peak yield (TPY) was affected by sampling interval (P < 0.05), with better estimates for 7D and 14D. Estimates of PY and TPY differed between the empirical and mechanistic models with both methods failing to estimate PY and TPY in atypical curves. The Dijkstra model showed the best fit for typical curves and the Pollott model for atypical curves in all the sampling intervals evaluated.Item The effect of lyophilised oral faecal microbial transplantation on functional outcomes in dogs with diabetes mellitus(John Wiley and Sons Ltd on behalf of British Small Animal Veterinary Association, 2025-04-15) Brown R; Barko P; Ruiz Romero JDJ; Williams DA; Gochenauer A; Nguyen-Edquilang J; Suchodolski JS; Pilla R; Ganz H; Lopez-Villalobos N; Gal AObjectives: We aimed to determine if oral faecal microbiota transplantation improves indices of glycaemic control, changes the faecal dysbiosis indices, alters faecal short-chain fatty acid and bile acid profiles and increases serum glucagon-like-peptide 1 concentrations in diabetic dogs. Materials and Methods: In this prospective randomised, placebo-controlled, double-blinded pilot study, we recruited nine diabetic dogs (five faecal microbiota transplantation and four placebo) and nine healthy controls. Results: Compared to healthy dogs, diabetic dogs had altered faecal short-chain fatty acid and bile acid profiles. In the first 30 days, the faecal microbiota transplantation group had a more rapid decline in interstitial glucose; however, the mean interstitial glucose of the faecal microbiota transplantation recipients did not differ from the placebo recipients at the end of the study. Compared with placebo, faecal microbiota transplantation recipients had a decreased 24-hour water intake at day 60 and increased faecal abundance of Faecalibacterium. Clinical Significance: This study provides a proof of concept for faecal microbiota transplantation in canine diabetes, and its data could inform the design of future large-scale studies. Further investigation is required to determine whether faecal microbiota transplantation would have any role as an adjunctive therapy in canine diabetes and to elucidate the mechanisms by which faecal microbiota transplantation may provide a beneficial clinical effect in canine diabetes.Item Low public awareness opens up new opportunities for highlighting milk as an iodine dietary source.(Elsevier B.V., 2024-09-17) Niero G; Censi S; Mian C; Manuelian CL; Rovai M; Tsiplakou E; da Costa L; Fuerst-Waltl B; Cruz AG; Berry DP; Lopez-Villalobos N; Masi A; Rakwal R; Hambardzumyan G; Borrisser-Pairó F; Koczura M; Trujillo Rojas LM; Albanell E; Rivera SG; González-Luna S; Berard J; De Marchi MThis international survey provides insights into public awareness of the importance of iodine as an essential trace mineral in human health along with knowledge of iodine dietary sources. The online questionnaire included sociodemographic aspects and dietary iodine consumer awareness on 7-point Likert-type questions. A total of 4,704 questionnaires from 16 countries were considered. Answers were analyzed through a multiple regression linear model including country, gender, age, education level, and employment status as fixed effects. Respondents were moderately aware of the importance of fish (4.86) and seafood (4.90) as dietary iodine sources, but less aware of milk as a primary iodine source (3.32). Respondent awareness varied considerably across countries. Age, education level, and employment status only modified their perception when asked about fish and seafood as a source of iodine, with elderly respondents, those highly educated and of working age being more aware of their relevance as dietary iodine sources. Respondent knowledge did not vary by age, education level, employment status, or gender when asked about cereals, vegetables and fruits, meat and milk as iodine-rich food sources. Consequently, labeling milk and dairy products as an iodine-rich food source should be considered. Public authorities can consider the results from this survey in promotional campaigns to improve the awareness of different iodine sources and their beneficial effect on health.Item A review of once-a-day milking in dairy cow grazing systems(Elsevier Inc. and Fass Inc. on behalf of the American Dairy Science Association, 2023-07-13) Lopez-Villalobos N; Jayawardana JMDR; McNaughton LR; Hickson RETwice-a-day (TAD) milking during the whole lactation is practiced in about 55% of New Zealand herds and once-a-day (OAD) milking during the whole lactation in about 10% of herds. The remainder of farmers use a mixture of TAD and OAD. Results from long-term comparisons show that over a full-lactation cows milked OAD, on average, had lower yields of milk (27%), fat (23%), and protein (24%) and higher percentages of fat and protein than cows milked TAD, but cows milked OAD for the entire lactation had better reproductive performance. Herds of cows milked OAD have higher mean 3-wk submission rate, 6-wk in-calf rate, and conception to the first service, and lower not-in-calf rate than the herds of cows milked TAD for the entire lactation. Farmers that have adopted OAD milking have culled cows that are unsuitable for OAD, and used sires selected on a OAD selection index to produce cow replacements that are more suitable for OAD milking. This OAD index includes the same traits that are included in the New Zealand national selection index with different relative economic weights on these traits plus including udder support, front teat placement, milking speed, and body capacity. A pasture-based milk production system based on OAD can be an alternative for many dairy farmers to maintain or increase farm profitability, with the additional benefits of better cow fertility and flexibility of using labor.Item Profitability of Swedish Red and White × Holstein crossbred cows compared with purebred Holstein cows(Elsevier Inc. on behalf of the American Dairy Science Association, 2024-11-08) Pipino DF; Lopez-Villalobos N; Hickson RE; Cabrera VE; Balzarini M; Piccardi MAn economic analysis was performed using a bioeconomic simulation model based on production, reproduction and longevity indicators to compare the profitability (net income per cow) of Swedish Red and White × Holstein (S × H) cows and pure Holstein (H) cows in commercial dairy farms of the center-south of Córdoba province, Argentina. The reproductive events analyzed in the model were pregnancy, calving and abortion. The longevity events were culling, sale and death. The lactation curve for each cow was modeled with a lactation function. Estimations were made for the first, second, and third and later lactations. Incomes were from milk, culled cows and calves. Costs were from feeding, reproductive program and replacement heifers. The reproductive cost of a H cow per year was greater than that of a S × H crossbred cow (USD 6.3). The replacement costs were also higher in pure H cows than in S × H cows (USD 67.8). The revenues from the sale of calves (USD 12.1) and milk production minus the feed cost (USD 8.2) were greater for S × H cows than H cows. Hence, the S × H cows generated a greater total profit (USD 94.4) per cow per year than H cows. The present results show that, in the studied production systems, S × H crossbred cows are more profitable than H cows.Item Animal factors that affect enteric methane production measured using the GreenFeed monitoring system in grazing dairy cows.(Elsevier B.V., 2024-04-16) Starsmore K; Lopez-Villalobos N; Shalloo L; Egan M; Burke J; Lahart BSimilar to all dairy systems internationally, pasture-based dairy systems are under increasing pressure to reduce their greenhouse gas (GHG) emissions. Ireland and New Zealand are 2 countries operating predominantly pasture-based dairy production systems where enteric CH4 contributes 23% and 36% of total national emissions, respectively. Ireland currently has a national commitment to reduce 51% of total GHG emissions by 2030 and 25% from agriculture by 2030, as well as striving to achieve climate neutrality by 2050. New Zealand's national commitment is to reduce 10% of methane emissions by 2030 and between 24% and 47% reduction in methane emissions by 2050. To achieve these reductions, factors that affect enteric methane (CH4) production in a pasture-based system need to be investigated. The objective of this study was to assess the relationship between enteric CH4 and other animal traits (feed intake, metabolic liveweight, energy corrected milk yield, milk urea concentration, and body condition score [BCS]) in a grazing dairy system. Enteric CH4 emissions were measured on 45 late lactation (213.8 ± 29 d after calving) grazing Holstein-Friesian and Holstein-Friesian × Jersey crossbred cows (lactation number 3.01 ± 1.65, 538.64 ± 59.37 kg live weight, and 3.14 ± 0.26 BCS) using GreenFeed monitoring equipment for 10 wk. There was a training period for the cows to use the GreenFeed of 3 wk before the 10-wk study period. The average enteric CH4 produced in the study was 352 g ± 45.7 g per day with an animal to animal coefficient of variation of 13%. Dry matter intake averaged 16.6 kg ± 2.23 kg per day, while milk solids (fat plus protein) averaged 1.62 kg ± 0.29 kg per day. A multiple linear regression model indicated that each one unit increase in energy corrected milk yield, metabolic liveweight and milk urea concentration, resulted in an increase in enteric CH4 production per day by 3.9, 1.74, and 1.38 g, respectively. Although each one unit increase in BCS resulted in a decrease in 39.03 g CH4 produced per day. When combined, these factors explained 47% of the variation in CH4 production, indicating that there is a large proportion of variation not included in the model. The repeatability of the CH4 measurements was 0.66 indicating that cows are relatively consistently exhibiting the same level of CH4 throughout the study. Therefore, enteric CH4 production is suitable for phenotyping.Item A blinded, placebo-controlled study on the clinical effects of vitamin E supplementation in dogs with osteoarthritis(Wiley Periodicals LLC. on behalf of the American College of Veterinary Internal Medicine., 2023-07-31) Gordon CL; Reeves SJ; Burchell RK; Thomson C; Gal A; Lopez-Villalobos N; Webster NSL; Litster KM; Mitchell RASBACKGROUND: Vitamin E has a positive effect in the management of osteoarthritis in humans, and in a previous study of dogs. It has been suggested to decrease C-reactive protein concentrations and liver enzyme activities in humans and animals. OBJECTIVE: To assess the effect of vitamin E supplementation on lameness, pain, pain medication requirement, clinical pathology variables, and quality of life in large-breed dogs with naturally occurring osteoarthritis. ANIMALS: Fifty-seven client-owned dogs with naturally occurring osteoarthritis. METHODS: Dogs received either vitamin E or placebo for 90 days in a randomized, placebo-controlled, double-blinded, prospective clinical trial. Clinical lameness scores, pain medication requirements, and owner questionnaires were used to assess response to treatment every 30 days. Blood samples were collected at enrollment and at the end of the study period. RESULTS: Vitamin E administration did not improve pain, lameness, or quality of life as assessed by owners and veterinarians. Vitamin E supplementation did not decrease the requirement for rescue pain relief. No changes in clinical pathology variables were observed after 90 days of vitamin E supplementation. Body weight was negatively associated with the lameness scores and requirement for rescue pain relief. CONCLUSION: Vitamin E supplementation did not have any observable positive effects in dogs with naturally occurring osteoarthritis.Item Lactation curves of Montbéliarde-sired and Viking Red-sired crossbred cows and their Holstein herdmates in commercial dairies(Elsevier Inc. on behalf of the American Dairy Science Association, 2024-06) Houdek ES; Hazel AR; Lopez-Villalobos N; Hansen LB; Heins BJLactation curves were estimated for Montbéliarde (MO) × Holstein (HO) and Viking Red (VR) × HO 2-breed crossbred cows and for MO × VR/HO and VR × MO/HO 3-breed crossbred cows and their HO herdmates from test-day observations in 7 high-performance herds that participated in a designed study. Cows calved from 2010 to 2017. Test-day observations from milk recording were used to fit the lactation curves of cows in their first 3 lactations. Lactations of cows were required to have at least 250 DIM and to have at least 6 test days ≤265 DIM. Lactation curves from random regression (RR) were compared for 305-d production (kg), peak production (kg), peak day of production, and production from 4 to 103 DIM (kg), from 104 to 205 DIM (kg), and from 206 to 305 DIM (kg) for milk, fat, and protein. Also, the persistency of production was compared. First-lactation versus second- and third-lactation cows were analyzed separately for both the 2-breed and 3-breed crossbred cows and their respective HO herdmates. Legendre polynomial RR had the best goodness of fit for the lactation curves compared with Ali-Schaeffer and Wilmink RR from the test-day observations of milk, fat, and protein production. For fluid milk production of first-lactation cows, the MO × HO 2-breed crossbreds were not different from their HO herdmates for any of the lactation-curve characteristics, except persistency. However, the VR × HO 2-breed crossbreds had less fluid milk production compared with their HO herdmates. For first lactation, the MO × HO 2-breed crossbreds had more persistency of milk, fat, and protein production compared with their HO herdmates. The first-lactation MO × VR/HO 3-breed crossbreds had more persistency of fluid milk production compared with their HO herdmates. For second and third lactations, both the MO × HO and the VR × HO 2-breed crossbreds had higher fat production compared with their HO herdmates. Furthermore, the MO × HO 2-breed crossbreds had more protein production (kg) in all 3 periods of lactation compared with their HO herdmates. Crossbred cows may have advantages over HO cows for persistency of production in high-performance herds.