Proxy measures and novel strategies for estimating nitrogen utilization efficiency in dairy cattle

Publication history: Accepted - 26 January 2021; Published online - 29 January 2021The efficiency with which dairy cows convert dietary nitrogen (N) to milk N is generally low (typically 25%). As a result, much of the N consumed is excreted in manure, from which N can be lost to the environment. Therefore there is increasing pressure to reduce N excretion and improve N use efficiency (NUE) on dairy farms. However, assessing N excretion and NUE on farms is difficult, thus the need to develop proximate measures that can provide accurate estimates of nitrogen utilisation. This review examines a number of these proximate measures. While a strong relationship exists between blood urea N and urinary N excretion, blood sampling is an invasive technique unsuitable for regular herd monitoring. Milk urea N (MUN) can be measured non-invasively, and while strong relationships exist between dietary crude protein and MUN, and MUN and urinary N excretion, the technique has limitations. Direct prediction of NUE using mid-infrared analysis of milk has real potential, while techniques such as near-infrared spectroscopy analysis of faeces and manure have received little attention. Similarly, techniques such as nitrogen isotope analysis, nuclear magnetic resonance spectroscopy of urine, and breath ammonia analysis may all offer potential in the future, but much research is still required.This research was funded by Department of Agriculture, Environment and Rural Affairs (DAERA) under grant number 19-1-16, by John Thompson and Sons Limited, and by Trouw Nutrition Limite

Effects of dietary crude protein concentration on animal performance and nitrogen utilisation efficiency at different stages of lactation in Holstein-Friesian dairy cows

Publication history: Accepted - 16 May 2022; Published online - 13 June 2022Nitrogen (N) excretion from livestock production systems is of significant environmental concern; however, few studies have investigated the effect of dietary CP concentration on N utilisation efficiency at different stages of lactation, and the interaction between dietary CP levels and stages of lactation on N utilisation. Holstein-Friesian dairy cows (12 primiparous and 12 multiparous) used in the present study were selected from a larger group of cows involved in a whole-lactation study designed to examine the effect of dietary CP concentration on milk production and N excretion rates at different stages of lactation. The total diet CP concentrations evaluated were 114 (low CP), 144 (medium CP) and 173 (high CP) g/kg DM, with diets containing (g/kg DM) 550 concentrates, 270 grass silage and 180 maize silage. During early (70–80 days), mid- (150–160 days) and late (230–240 days) lactation, the same 24 animals were transferred from the main cow house to metabolism units for measurements of feed intake, milk production and faeces and urine outputs. Diet had no effect on BW, body condition score, or milk fat, protein or lactose concentration, but DM intake, milk yield and digestibilities of DM, energy and N increased with increasing diet CP concentration. The effect of diet on milk yield was largely due to differences between the low and medium CP diets. Increasing dietary CP concentration significantly increased urine N/N intake and urine N/manure N, and decreased faecal N/N intake, milk N/N intake and manure N/N intake. Although increasing dietary CP level significantly increased urine N/milk yield and manure N/milk yield, differences in these two variables between low and medium CP diets were not significant. There was no significant interaction between CP level and stage of lactation on any N utilisation variable, indicating that the effects of CP concentration on these variables were similar between stages of lactation. These results demonstrated that a decrease in dietary CP concentration from high (173 g/kg DM) to medium level (144 g/kg DM) may be appropriate for Holstein-Friesian dairy cow to maintain milk production efficiency, whilst reducing both urine N and manure N as a proportion of N intake or milk production.This research received funding from the Department of Agriculture, Environment and Rural Affairs of Northern Ireland (project codes: 0700 and 17-4-03)

Physical and economic performance of dairy cows managed within contrasting grassland based milk production systems over three successive lactation

Publication history: Accepted - 11 December 2021; Published online - 3 February 2022.A diverse range of grassland-based milk produc- tion systems are practiced on dairy farms in temper- ate regions, with systems differing in relation to the proportion of grazed grass, conserved forages and concentrates in diet, calving season, duration of hous- ing, cow genotype, and performance levels. The current study was conducted to examine performance within diverse grassland-based systems of milk production under experimental conditions. This study examined 4 milk production systems over 3 successive lactations (20 cows per system during each lactation). With win- ter calving-fully housed (WC-FH), Holstein cows were housed for the entire lactation and offered a complete diet consisting of grass silage, maize silage, and con- centrates [approximately 50% forage on a dry matter (DM) basis]. With winter calving-conventional (WC- Con), Holstein cows were housed and offered the same diet from calving until turnout (late March) as offered with WC-FH, and thereafter cows were given access to grazing and supplemented with 5.0 kg of concentrate/ cow daily. Two spring-calving systems were examined, the former involving Holstein cows (SC-H) and the lat- ter Jersey × Holstein crossbred cows (SC-J×H). Cows on these systems were offered a grass silage-concentrate mix (70% forage on a DM basis) until turnout (late February), and thereafter cows were given access to grazing supplemented with 1.0 kg of concentrate/ cow per day. The contributions of concentrates (3,080, 2,175, 722, and 760 kg of DM/cow per lactation), conserved forages (3,199, 1,556, 1,053, and 1,066 kg of DM/cow per lactation), and grazed grass (0, 2,041, 2,788, and 2,692 kg of DM/cow per lactation) to total DMI (6,362, 5,763, 4,563, and 4,473 kg of DM/cow per lactation) with WC-FH, WC-Con, SC-H, and SC-J×H, respectively, varied considerably. Similarly, milk yield (9,333, 8,443, 6,464, and 6,049 kg/cow per lactation), milk fat content (44.9, 43.3, 42.8, and 49.0 g/kg), and milk protein content (34.6, 34.9, 33.6, and 36.3 g/kg) differed between systems (WC-FH, WC-Con, SC-H, and SC-J×H, respectively). The higher milk yields with the WC systems reflect the greater concentrate inputs with these systems, whereas the greater milk fat and protein content with SC-J×H reflect the use of Jersey crossbred cows. Crossbred cows on SC-J×H produced a similar yield of milk solids as Holstein cows on SC-H. Cows on WC-FH ended the lactation with a greater body weight (BW) and body condition score than cows on any other treatment. While Jersey crossbred cows on SC-J×H had a lower BW than Holstein cows on SC-H, cows on these 2 systems were not different for any of the other BW, body condition score, or blood metabolite parameters examined. Cows on WC-FH had a greater interval from calving to conception, a greater mastitis incidence, and a greater locomotion score than cows on the spring calving systems. Whole-system stocking rates and annual milk outputs were calcu- lated as 2.99, 2.62, 2.48, and 2.50 cows/ha, and 25,706, 20,822, 15,289, and 14,564 kg of milk/ha, with each of WC-FH, WC-Con, SC-H, and SC-J×H, respectively. Gross margin per cow was highest with WC-Con, gross margin per hectare was highest with WC-FH, and gross margin per kilogram of milk was highest with SC-J×H. This study demonstrated that diverse grassland-based milk production systems are associated with very dif- ferent levels of performance when examined per cow and per hectare.This work was funded by the Department of Agriculture and Rural Development in Northern Ireland (DAERA), and by AgriSearch (farmer levy)

Supplementation strategies for lactating dairy cows offered very high quality grass silages: Starch-based or fibre-based concentrates offered with or without straw

Publication history: Accepted - 13 February 2020; Published online - 15 February 2020.A three-period change-over design study using 24 mid-lactation multiparous Holstein-Friesian dairy cows, examined supplementation strategies for a high quality grass silage (dry matter (DM), 418 g/kg; crude protein (CP), 170 g/kg DM; metabolisable energy (ME), 12.1 MJ/kg DM). Four treatments, in a 2 × 2 factorial arrangement, compared concentrate type (High-starch or High-fibre) and straw inclusion (Straw or No-straw). Concentrates had a starch and neutral detergent fibre content of 373 and 258 g/kg DM, respectively (Highstarch), and 237 and 339 g/kg DM, respectively (High-fibre). In the No-straw treatments, silage and concentrates were offered as a total mixed ration in a 57:43 DM ratio. In the Straw treatments, chopped straw was added at 4% of total DM, replacing part of the silage component of the diet. Following this study, the effect of diet on nutrient utilisation efficiency was examined using four cows/treatment. There were no interactions between concentrate type and straw inclusion for any cow performance or digestibility parameters. Silage dry matter intake (DMI) and total DMI were reduced with the High-fibre concentrate (P = 0.001 and P = 0.006, respectively) and straw inclusion (P < 0.001 and P = 0.014, respectively). Neither concentrate type nor straw inclusion had a significant effect on milk yield or milk fat content. The High-starch concentrate increased milk protein content (P < 0.001), while straw inclusion decreased milk protein content (P = 0.036). Treatment had no effect on cow body weight, condition score, faecal scores, digestibility coefficients or nitrogen and energy utilisation efficiency. In conclusion, supplementing a high quality grass silage with a carefully formulated ‘high starch’ concentrate improved DMI and milk protein content with no adverse effects on cow performance. Straw inclusion in the diet had no beneficial effects on DMI, milk production or nutrient utilisation efficiency.This project was funded by Department of Agriculture, Environment and Rural Affairs (DAERA) in Northern Ireland, and by AgriSearch (Farmers Levy)

Relationships between energy balance during early lactation and cow performance, blood metabolites, and fertility: A meta-analysis of individual cow data

Publication history: Accepted - 15 January 2021; Published online - 6 March 2021This study was designed to contribute to the understanding of the relationships between energy balance (EB) in early lactation [4 to 21 d in milk (DIM)] and fertility traits [interval to start of luteal activity (SLA), interval to first observed heat (FOH), and conception to first artificial insemination (AI)], and their associated relationships with cow performance and blood metabolites between 4 to 150 DIM. Individual cow data (488 primiparous and 1,020 multiparous lactations) from 27 experiments was analyzed. Data on cow performance, EB (on a metabolizable energy basis), and fertility traits were available for all cows, whereas milk progesterone data (to determine SLA) and periodic blood metabolite data were available for 1,042 and 1,055 lactations, respectively. Data from primiparous and multiparous cows were analyzed separately, with the data sets for the 2 parity groups divided into quartiles (Q1–Q4) according to the average EB during 4 to 21 DIM (EB range for Q1 to Q4: primiparous, −120 to −49, −49 to −24, −24 to −3, and −3 to 92 MJ/d, respectively: multiparous, −191 to −79, −79 to −48, −48 to −22, and −22 to 93 MJ/d, respectively). Differences between EB quartiles for production and fertility traits were compared. In early lactation (4 to 21 DIM), moving from Q1 to Q4 mean DMI and metabolizable energy intake increased whereas mean ECM decreased. During the same period, moving from Q1 to Q4 milk fat content, milk fat-to-protein ratio, and plasma nonesterified fatty acid and β-hydroxybutyrate concentrations decreased, whereas milk protein content and plasma glucose concentrations increased in both primiparous and multiparous cows. When examined over the entire experimental period (4 to 150 DIM), many of the trends in intakes and milk production remained, although the magnitude of the difference between quartiles was much reduced, whereas milk fat content did not differ between quartiles in primiparous cows. The percentage of cows with FOH before 42 DIM increased from Q1 to Q4 (from 46 to 72% in primiparous cows, and from 41 to 58% in multiparous cows). Interval from calving to SLA and to FOH decreased with increasing EB during 4 to 21 DIM, with these occurring 9.8 and 10.2 d earlier, respectively, in Q4 compared with Q1 (primiparous cows), and 7.4 and 5.9 d earlier, respectively, in Q4 compared with Q1 (multiparous cows). For each 10 MJ/d decrease in mean EB during 4 to 21 DIM, FOH was delayed by 1.2 and 0.8 d in primiparous and multiparous cows, respectively. However, neither days to first AI nor the percentage of cows that conceived to first AI were affected by daily EB during 4 to 21 DIM in either primiparous or multiparous cows, and this is likely to reflect a return to a less metabolically stressed status at the time of AI. These results demonstrate that interval from calving to SLA and to FOH were reduced with increasing EB in early lactation, whereas early lactation EB had no effect on conception to the first service.This work was supported by the Department of Agriculture and Rural Development for Northern Ireland (DAERA, Northern Ireland, UK) as part of the Department of Agriculture, Food, and the Marine (DAFM, Republic of Ireland) NutriGen project. Maurício Civiero was in receipt of a scholarship from Programa de Bolsas Universitárias de Santa Catarina (UNIEDU/FUMDES, Florianópolis, SC, Brazil) and thanks Centro Universitário Vale do Iguaçu (UNIGUAÇU, União da Vitória, PR, Brazil) for providing time to complete this wo

Optimism and pasture access in dairy cows

Allowing dairy cattle to access pasture can promote natural behaviour and improve their health. However, the psychological benefits are poorly understood. We compared a cognitive indicator of emotion in cattle either with or without pasture access. In a crossover experiment, 29 Holstein–Friesian dairy cows had 18 days of overnight pasture access and 18 days of full-time indoor housing. To assess emotional wellbeing, we tested cows on a spatial judgement bias task. Subjects learnt to approach a rewarded bucket location, but not approach another, unrewarded bucket location. We then presented cows with three “probe” buckets intermediate between the trained locations. Approaching the probes reflected an expectation of reward under ambiguity—an “optimistic” judgement bias, suggesting positive emotional states. We analysed the data using linear mixed-effects models. There were no treatment differences in latency to approach the probe buckets, but cows approached the known rewarded bucket slower when they had pasture access than when they were indoors full-time. Our results indicate that, compared to cattle housed indoors, cattle with pasture access display less anticipatory behaviour towards a known reward. This reduced reward anticipation suggests that pasture is a more rewarding environment, which may induce more positive emotional states than full-time housing

Cognition-Enhancing Drugs: Can We Say No?

Normative analysis of cognition-enhancing drugs frequently weighs the liberty interests of drug users against egalitarian commitments to a level playing field. Yet those who would refuse to engage in neuroenhancement may well find their liberty to do so limited in a society where such drugs are widespread. To the extent that unvarnished emotional responses are world-disclosive, neurocosmetic practices also threaten to provide a form of faulty data to their users. This essay examines underappreciated liberty-based and epistemic rationales for regulating cognition-enhancing drugs

The development and validation of a scoring tool to predict the operative duration of elective laparoscopic cholecystectomy

Background: The ability to accurately predict operative duration has the potential to optimise theatre efficiency and utilisation, thus reducing costs and increasing staff and patient satisfaction. With laparoscopic cholecystectomy being one of the most commonly performed procedures worldwide, a tool to predict operative duration could be extremely beneficial to healthcare organisations. Methods: Data collected from the CholeS study on patients undergoing cholecystectomy in UK and Irish hospitals between 04/2014 and 05/2014 were used to study operative duration. A multivariable binary logistic regression model was produced in order to identify significant independent predictors of long (> 90 min) operations. The resulting model was converted to a risk score, which was subsequently validated on second cohort of patients using ROC curves. Results: After exclusions, data were available for 7227 patients in the derivation (CholeS) cohort. The median operative duration was 60 min (interquartile range 45–85), with 17.7% of operations lasting longer than 90 min. Ten factors were found to be significant independent predictors of operative durations > 90 min, including ASA, age, previous surgical admissions, BMI, gallbladder wall thickness and CBD diameter. A risk score was then produced from these factors, and applied to a cohort of 2405 patients from a tertiary centre for external validation. This returned an area under the ROC curve of 0.708 (SE = 0.013, p  90 min increasing more than eightfold from 5.1 to 41.8% in the extremes of the score. Conclusion: The scoring tool produced in this study was found to be significantly predictive of long operative durations on validation in an external cohort. As such, the tool may have the potential to enable organisations to better organise theatre lists and deliver greater efficiencies in care