INVITED REVIEW: An evaluation of EFSA opinion on calf welfare from a nutritional and management perspective.

In March, 2023, the European Food Safety Authority published a Scientific Opinion on Calf Welfare. This Opinion was prepared in response to a request from the European Commission to provide an independent view on the welfare of calves that reflected the most recent scientific knowledge. Data sources used to develop their recommendations included peer-reviewed studies, expert knowledge, and gray literature. The Opinion considered specific scenarios and welfare consequences of specific management practices, including feeding fiber to calves raised for white veal and amount of cow-calf contact. Their Opinion suggested that calves should be fed specific quantities of forage NDF during the rearing cycle. Regarding separation of calves, the Committee recommended that the calf should remain with the cow for a minimum of 24 h and then be housed with another calf. They further suggested that prolonged cow-calf contact should increasingly be implemented due to benefits to both cow and calf to minimize stress of separation. The objective of this review is to assess the veracity of these recommendations and the scientific data that underpins them. This review will present a literature to support the contention that, from a nutritional and management perspective, these recommendations may impair calf welfare by exposing calves to innutritious rations containing excess fiber and increasing their risk of morbidity and mortality due to poor colostrum intake and exposure to disease-causing pathogens. Alternative recommendations are made that may further the goal of calf welfare in the context of nutrition and housing.

False-positive HIV screening test in a healthcare student.

This case report describes a 22-year-old female Ambulance Technician student who displayed human immunodeficiency virus (HIV) false positivity following a recent hepatitis B vaccination. Occupational health clinicians who work in a healthcare setting (with healthcare staff and/or students) should be aware of the possibility of false-positive HIV screening test results, and where a false positive is suspected, they should consider what the underlying cause could be and should consider whether further medical investigation is required.

Invited review: Total solids concentration in milk or milk replacer for dairy calves.

Restricting milk or milk replacer (MR) fed to dairy calves to 10% of body weight at 12.5% total solids (TS) concentration is a common feeding strategy that promotes early weaning and lowers total feed costs for raising young calves. However, this strategy has been associated with inferior performance and compromised welfare. Because a restricted liquid nutrition plan limits calf growth due to limited supply of nutrients, research on increased supply of nutrients from liquid has shown improved growth, health, and welfare of calves. Nutrient supply may be increased by feeding larger amounts of milk or MR averaging 12.5% TS, or by increasing TS above the usual 12.5% TS by increasing MR TS concentration alone (TS+), or by increasing TS concentration and volume simultaneously (TSV+). The objective of this review is to discuss liquid nutrition plans with greater TS concentration in MR or in milk diets, considering the effects of such strategies on performance and digestive tract development before weaning and the future performance of dairy calves. This review will focus on liquid nutrition plans that are based on increased TS concentration (i.e., TS+ or TSV+); therefore, enhanced liquid nutrition plans based only on increased volumes will not be the discussed. Improved growth rates have been observed in calves fed TSV+ programs. However, reduced starter intake preweaning can also have negative effects on dry matter intake, average daily gain, and digestibility postweaning. Feeding a TS+ program may reduce impairment of starter intake and therefore have positive effects on performance, nutrient digestibility, and health. When considering an accelerated nutrition plan with TS+ or TSV+, it is important to consider osmolality of the liquid diet. Further studies are necessary to confirm this hypothesis and the cost-benefit of alternative liquid nutrition plans, as well as the optimal TS concentration of milk or MR fed to dairy calves.

Effects of milk replacer allowances and levels of starch in pelleted starter on nutrient digestibility, whole gastrointestinal tract fermentation, and pH around weaning.

The objectives of this study were to examine the effects of pelleted starter diets differing in starch and neutral detergent fiber (NDF) content when fed differing levels of milk replacer (MR) on nutrient digestibility, whole gastrointestinal tract fermentation, pH, and inflammatory markers in dairy calves around weaning. Calves were randomly assigned to 1 of 4 dietary treatments (n = 12 per treatment) in a 2 × 2 factorial design based on daily MR allowance and amount of starch in pelleted starter (SPS): 0.691 kg of MR per day [dry matter (DM) basis] with starter containing low or high starch (12.0% and 35.6% starch on DM basis, respectively), and 1.382 kg of MR per day (DM) with starter containing low or high starch. All calves were housed in individual pens with straw bedding until wk 5 when bedding was covered. Calves were fed MR twice daily (0700 and 1700 h) containing 24.5% crude protein (DM) and 19.8% fat (DM), and had access to pelleted starter (increased by 50 g/d if there were no refusals before weaning and then 200 g/d during and after weaning) and water starting on d 1. Calves arrived between 1 and 3 d of age and were enrolled into an 8-wk study, with calves undergoing step-down weaning during wk 7. Starting on d 35, an indwelling pH logger was inserted orally to monitor rumen pH until calves were dissected at the end of the study in wk 8. Higher SPS calves showed an increase in rumen pH magnitude (1.46 ± 0.07) compared with low SPS calves (1.16 ± 0.07), a decrease in rumen pH in wk 8 (high SPS: 5.37 ± 0.12; low SPS: 5.57 ± 0.12), and a decrease in haptoglobin in wk 8 (high SPS: 0.24 ± 0.06 g/L; low SPS: 0.49 ± 0.06 g/L). The majority of differences came from increased starter intake in general, which suggests that with completely pelleted starters the differences in starch and NDF do not elicit drastic changes in fermentation, subsequent end products, and any resulting inflammation in calves around weaning.

Performance and visceral tissue growth and development of Holstein calves fed differing milk replacer allowances and starch concentrations in pelleted starter.

The objectives of this study were to investigate how milk replacer (MR) allowance and differing concentrations of starch and neutral detergent fiber in starter alters visceral tissue and overall growth of the calf. Calves were randomly assigned to 1 of 4 dietary treatments (n = 12 per treatment) arranged in a 2 × 2 factorial based on daily MR allowance (MRA) and amount of starch in pelleted starter (SPS) as follows: 0.691 kg of MR/d [dry matter (DM) basis] with starter containing low or high starch (12.0% and 35.6% starch, respectively) and 1.382 kg of MR/day (DM) with starter containing low or high starch. All calves were housed in individual pens with straw bedding until wk 5 when bedding was covered to minimize intake. Calves were fed MR twice daily (0700 and 1700 h) containing 24.5% crude protein (DM) and 19.8% fat (DM), and had access to pelleted starter (increased by 50 g/d if there were no refusals before weaning, and then 200 g/d during and after weaning) and water starting on d 1. Calves arrived between 1 and 3 d of age and were enrolled into an 8-wk study, with calves undergoing step-down weaning during wk 7. Intakes were measured daily, and body weight (BW) and blood samples were recorded and collected weekly. Calves were dissected in wk 8 for visceral tissue measurements. Overall, there was increased MR DM intake for the high- (0.90 ± 0.01 kg/d; ± SE) compared with the low-MRA (0.54 ± 0.01 kg/d) calves, whereas starter DM intake increased in low- (0.47 ± 0.05 kg/d) compared with high-MRA (0.20 ± 0.05 kg/d) calves, which was driven by increases in wk 6, 7, and 8. High-MRA calves had increased BW during wk 2, 3, 4, 5, 6, and 7. The difference in BW disappeared by wk 8, with overall average daily gain having a tendency to be increased in high (0.57 ± 0.04 kg/d) compared with low-MRA (0.50 ± 0.04 kg/d) calves, whereas average daily gain was increased in high-MRA calves during wk 2 and 3 and increased in low-MRA calves during wk 7 and 8. There were several differences throughout visceral tissue measurements, but most notably, an increase in rumen mass (i.e., full, empty, and digesta weights) in low- compared with high-MRA calves, as well as in low- compared with high-SPS calves was observed. The length, width, and 2-dimensional area of rumen papillae were also increased in low- (area: 0.88 ± 0.03 mm2) compared with high-MRA (0.46 ± 0.03 mm2) calves. The majority of differences were attributed to increased MR allowance, which contributed to reduced pelleted starter intake by more than 50% and reduced rumen development, whereas differences in starch intake from the completely pelleted starter had minimal effects on overall growth and tissue measurements.

Effects of mixed tocopherols added to milk replacer and calf starter on intake, growth, and indices of stress.

Vitamin E comprises 8 fat-soluble isoforms: α-, ß-, γ-, and δ-tocopherol and α-, ß-, γ-, and δ-tocotrienol. Yet the body preferentially uses α-tocopherol, and only α-tocopherol supplementation can reverse vitamin E deficiency symptoms. However, other isoforms influence many biological functions in the body, including inflammation and stress. Therefore, the study objective was to determine metabolic and performance responses in young calves fed diets containing a constant amount of α-tocopherol and increasing amounts of soybean oil-derived mixed γ- and δ-tocopherols. Holstein calves [n = 48; 2-3 d of age; 40.2 kg of initial body weight (BW), standard error = 0.54] were assigned to receive approximately 0, 5, 10, or 15 mg/kg of BW daily (treatments T0, T1, T2, and T3, respectively) of mixed tocopherols (TMIX) provided in milk replacer (MR) and calf starter. The TMIX liquid contained 86% γδ-tocopherols and 9% α-tocopherol. Milk replacers were formulated to contain approximately 0, 400, 800, or 1,200 mg of TMIX/kg for treatments T0, T1, T2, and T3, respectively. Calf starters were formulated to contain approximately 0, 250, 500, or 750 mg of TMIX/kg for treatments T0, T1, T2, and T3, respectively. Mean consumption of γδ-tocopherols was 0.0, 6.5, 14.3, and 20.5 mg/kg of BW, respectively. Milk replacer contained 24% crude protein (CP) and 20% fat on a dry matter (DM) basis. Calf starters were pelleted and offered for ad libitum consumption from 0 to 56 d. Starters contained 18 to 20% CP and 9 to 12% starch in the DM. On d 28, 4 calves per treatment were randomly selected for slaughter, and necropsy was performed. Samples of liver, duodenum, ileum, and trapezius muscle were collected and stored before analysis for α-, ß-, γ-, and δ-tocopherols and δ-tocotrienol. Data were analyzed using a completely randomized design using mixed model ANOVA with orthogonal polynomials to determine linear and quadratic effects of TMIX. Repeated-measures analyses were performed for data collected over time. Increasing dietary TMIX increased or tended to increase change in hip width at 28 and 56 d, respectively, and improved average daily BW gain and gain-to-feed ratio at 56 d. Increasing TMIX reduced plasma xanthine oxidase at 0 h and tended to reduce concentrations at 24 h following vaccination with 2 commercial vaccines on d 28; however, we detected no effect of TMIX following vaccination on d 56. Concentration of α-tocopherol in skeletal muscle declined quadratically with increasing TMIX, whereas ileal and liver γ-tocopherol increased linearly with increasing TMIX. The number of mucin-2 cells in the ileum increased more than 2-fold in calves fed T3. Addition of mixed tocopherols to diets of young dairy calves improved animal growth and altered indices of antioxidant metabolism.

Effects of feeding milk replacer at a moderate rate, ad libitum, or with a step-up program on Holstein calf growth performance to 4 months of age.

The objective of this study was to evaluate 3 milk replacer (MR) feeding programs on calf performance to 4 mo of age. Male Holstein calves (n = 48; 2-3 d old) were randomly assigned to either a moderate rate of MR (MOD; 0.66 kg/d for 39 d, then 0.33 kg/d for 3 d), an ad libitum rate of MR (ADLIB; offered twice daily between 0630 and 0830 h and between 1430 and 1630 h for 35 d, 0.66 kg/d for 4 d, and 0.33 kg/d for 3 d), or a step-up rate of MR (STEPUP; increased from 0.32 to 0.62 kg/d in first 12 d, 0.66 kg/d for 27 d, and 0.33 kg/d for 3 d). The MR (25% CP, 18% fat) was fed twice daily to d 39 and once daily thereafter. During the nursery phase (0-56 d), calves were housed in individual pens and offered textured starter (40% starch, 21% CP on a DM basis) and water ad libitum. Calf body weight (BW) was measured initially and weekly thereafter. Hip widths (HW) were measured initially and every 2 wk thereafter. In the grower phase, (57-112 d), calves were grouped by previous treatment and moved to group pens (4 calves/pen). The same starter used in the nursery phase was blended with 5% chopped grass hay and offered ad libitum. Calf BW and HW were measured on d 56, 84, and 112. Total MR intake per calf averaged 27, 51, and 25 kg for MOD, ADLIB, and STEPUP programs, respectively, with a range of 42 to 63 kg for ADLIB. In the nursery phase, starter intake and feed efficiency were less for ADLIB versus MOD, whereas fecal scores and abnormal fecal score days were greater for calves fed ADLIB versus MOD. Calves fed STEPUP had lesser average daily gain than calves fed MOD. During the grower phase, initial BW was greater for ADLIB versus MOD, though final BW was not different between MOD and ADLIB or STEPUP. Calves previously fed MOD had greater average daily gain, feed efficiency, and HW change than calves fed ADLIB. In this study, feed efficiency was lower when MR was fed ad libitum, and growth advantages observed at 2 mo were lost by 4 mo of age.

Effects of milk replacer feeding rate and fat content on Jersey calf nutrient digestion and performance to 4 months of age.

This study evaluated effects of milk replacer (MR) feeding rate and fat concentration in MR on total-tract digestion (TTD) and growth performance in Jersey calves. Jersey heifer calves (n = 100, 2 blocks of 50; initially 30 ± 3.0 kg of body weight; 4-11 d of age) were randomly assigned to 1 of 4 treatments in a 2 × 2 factorial arrangement of MR feeding rate [454 g for 42 d, and 227 g for 7 d (MOD); or 454 g for 7 d, 681 g for 35 d, and 341 g for 7 d (HI), as-fed basis] and MR fat content (17 or 24% fat as-fed basis). Milk replacers (24% crude protein as-fed basis) were reconstituted to 14% solids and fed in 2 equal feedings for 42 d, and then mornings only for 7 d. Textured calf starter (21% crude protein, 40% starch, dry matter basis) and water were offered for ad libitum consumption. From d 57 to 112, calf starter was mixed with 5% chopped grass hay. Calves were housed individually to d 56 and housed in groups (4-5 calves/pen) from d 57 to 112. Estimates of TTD were measured in 5 calves/treatment (block 1) at wk 3 of the study using acid-insoluble ash as an indigestible marker. From 0 to 56 d, calf starter intake (CSI) was greater for MOD vs. HI and 17 versus 24% fat; average daily gain was greater for HI versus MOD; and hip width change was greater for 17 versus 24% fat. Estimates of organic matter TTD were greater for HI versus MOD, but neutral detergent fiber TTD was greater for MOD versus HI and for 17 versus 24% fat. From 57 to 112 d, hip height change was greater for MOD versus HI, and hip width change was greater for 17 versus 24% fat. In this study, feeding Jersey calves more MR improved preweaning average daily gain, but had a negative effect on CSI and likely rumen development, as neutral detergent fiber TTD was reduced at 3 wk and frame growth was reduced from d 57 to 112. This resulted in similar final calf body weights between MR feeding rates at the end of the study. No benefits were observed for feeding more fat in MR as CSI or for NDF digestibility, and frame growth was reduced.

Models to predict dry feed intake in Holstein calves to 4 months of age.

Voluntary daily dry feed intake (DFI) in Holstein calves was predicted using 60,761 individual daily observations collected from 1,235 Holstein calves in 30 experiments from 4 research stations in the United States and Europe. Consumption of dry feed (calf starter and hay, kg/d or percent of body weight) was measured from 3 to 114 d of age. Linear models and 2- and 3-parameter nonlinear models were evaluated to predict DFI using age of calf, intake of milk replacer, ambient temperature, percent forage, and neutral detergent fiber concentration in ration dry matter (DM) as independent variables. The initial data set was randomly divided within study location into development (80% of all observations) and validation data sets, and initial screening was conducted using the development data set. Five nonlinear models and 3 linear models (candidate models) were identified and used in further model evaluation. Cross-validation studies (n = 20) with the validation data set were conducted by linear regression of DFI with predicted DFI as independent variable. Candidate models were subsequently evaluated with data from 12 published studies in 2 analyses. The exponential model that best predicted daily DFI in Holstein calves in original and external data sets was DFI (kg/d) = 1.3207 × e[(-5.3892 + 0.6376 × MEgap) × EXP(-0.0392 × Age)] - 0.0013 × Temp + 0.0032 × NDFDM + 0.0026 × Age × MEgap - 0.3646 × PctForage [coefficient of determination (R2) = 0.92, concordance correlation coefficient (CCC) = 0.96, and mean square error of prediction (MSEP) = 0.10 kg]; where MEgap (Mcal/d) = difference of daily metabolizable energy (ME) requirement and ME intake from milk replacer; Age = age of calf (d) from 3 to 114, Temp = mean daily ambient temperature (°C), NDFDM = ration neutral detergent fiber (% DM); PctForage = percent forage in ration DM. The linear model that best predicted DFI was DFI (kg/d = -0.1349 + 0.0106 × Age + 0.1808 × MEgap + 0.0013 × Age × MEgap + 0.0001 × Temp + 0.00002 × Age × Temp (R2 = 0.93, CCC = 0.96, and MSEP = 0.10 kg). When Temp and ration characteristics were not included, optimal models were 1.4362 × e[(-4.6646 + 0.5234 × MEgap) × EXP(-0.0361 × Age)] + 0.0025 × Age × MEgap (R2 = 0.92, CCC = 0.96, and MSEP = 0.11 kg) and -0.1344 + 0.0102 × Age + 0.1810 × MEgap + 0.0013 × Age × MEgap [R2 = 0.93, CCC = 0.96, and MSEP = 0.10 kg]. Models of daily DFI may improve prediction of nutrient supply to young Holstein calves to approximately 4 mo of age, thereby increasing prediction of growth performance.

Effect of increasing the amount of hay fed on Holstein calf performance and digestibility from 2 to 4 months of age.

A good transition from a mainly liquid diet to a solid diet of concentrates and forages is important considering the small size and development of the calf's rumen. However, the optimal amount of hay or other high-fiber ingredients in the diet of recently weaned calves is not well defined. The objective of this trial was to determine the effects of feeding 0, 5, or 10% chopped grass hay (6.5% crude protein, 64.6% neutral detergent fiber) with a textured, high-starch starter (20.5% crude protein, 38.4% starch, 14.1% neutral detergent fiber; protein pellet, whole corn, and oats) on performance and digestion in Holstein steer calves between 2 and 4 mo of age. Forty-eight calves (initial body weight = 90.7 ± 2.15 kg) were housed in group pens (4 per pen) and fed diets and water for ad libitum intake. Feed offered and refused was measured daily. Calf body weight, hip width, and body condition score (1-5 scale) were measured initially and at 28 and 56 d. Fecal samples were collected from the pen floor with care not to sample bedding material and composited by pen during d 5-9, 26-30, and 47-51 to estimate apparent total-tract digestibility using acid-insoluble ash. Data were analyzed as a completely randomized design with repeated measures and pen as the experimental unit. As grass hay increased, dry matter intake (kg/d) decreased linearly but tended to change quadratically. Dry matter intake as a % of body weight changed quadratically with increasing hay, increasing from 0 to 5%, and decreasing from 5 to 10% hay. Average daily gain (1.15, 1.12, and 0.95 kg/d), feed efficiency (0.336, 0.319, and 0.309 kg of average daily gain/kg of dry matter intake), and hip width change (4.6, 4.7, and 4.1) decreased linearly with 0, 5, and 10% hay, respectively. Overall estimates of dry matter, organic matter, neutral detergent fiber, acid detergent fiber, and crude protein digestibility changed quadratically with hay, increasing from 0 to 5%, and decreasing from 5 to 10% hay, whereas digestibility of starch, sugar, and fat decreased linearly with increasing hay. Digestibility of dry matter, organic matter, neutral detergent fiber, and acid detergent fiber increased from 2 to 3 mo of age, and decreased from 3 to 4 mo of age. Digestibility of starch decreased linearly and digestibility of fat and crude protein increased linearly with age. Digestive capacity did not appear mature by 4 mo of age. Feeding 5% chopped hay supported optimal digestion and growth in calves 2 to 4 mo of age, which agrees with previously published research.

Meta-analysis of effects of age on intestinal digestibility of liquid feeds in young calves.

A meta-analysis was conducted to determine the effect of age on digestibility of liquid feeds fed to preweaned Holstein calves. Calves were 4 to 76 d of age and fed whole milk or milk replacer containing all-milk protein. Least squares means of apparent total-tract N, DM, and fat digestibilities (n = 84, 51, and 24, respectively) from 12 publications were used. Broken line regression and mixed model ANOVA were used to determine ages at which digestion of nutrients no longer increased with age, indicating maturation of digestive capacity. Digestibility of DM, N, and fat reached maximum digestibilities of 94.1, 92.7, and 97.5% at 29, 29, and 32 d of age, respectively. These data indicate age-related changes in digestion of liquid feeds in preweaned Holstein calves and allow correction of apparent total-tract digestibility estimates in nutrient supply models. Digestibility of liquid nutrients in calves fed whole milk or all milk containing milk replacers reached maximal capacity at approximately 30 d of age.

Behaviour of occupational health services during the COVID-19 pandemic.

BACKGROUND: Disasters, crises and pandemics are emergencies which impact on businesses severely. The COVID-19 pandemic reached its peak in mid-April 2020 in the UK. During this period, NHS Occupational Health Services (OHS) were stretched to their limit along with other health services. OHS may have had to change their pattern of operation, operating times, services offered, etc. to cope with the pandemic. Data about business model modifications, services offered by the OHS businesses during the pandemic could help in better utilization of OHS resources in the future. AIMS: To understand the behaviour of OHS in different parts of the country during the COVID-19 pandemic. METHODS: An online survey link was sent to both accredited and unaccredited UK Occupational Health Physicians (OHPs). RESULTS: Sixty-two OHPs responded to the survey. In the current pandemic, 51% of the OHS (95% CI 0.38-0.62) offered weekend or out-of-hours (OOH) services, 21% had to employ extra staff (95% CI 0.13-0.33) and 54% had to change their working hours (95% CI 0.41-0.65). Ninety per cent of the OHS (95% CI 0.78-0.94) continued to offer routine services; however, there was a decline in offering vaccination services. Fifty-six per cent of the OHS (95% CI 0.42-0.67) offered a dedicated telephone line and 46% of the OHS (95% CI 0.32-0.56) started a dedicated COVID-19 queries inbox. CONCLUSIONS: There was a change in the behaviour of the OHS to cope with the pandemic. Having a dedicated helpline to manage the crisis situation seemed a logical step whilst offering routine services.

Consensus recommendations on calf- and herd-level passive immunity in dairy calves in the United States.

Passive immunity in calves is evaluated or quantified by measuring serum or plasma IgG or serum total protein within the first 7 d of age. While these measurements inform about circulating concentrations of this important protein, they are also a proxy for evaluating all of the additional benefits of colostral ingestion. The current individual calf standard for categorizing dairy calves with successful passive transfer or failure of passive transfer of immunity are based on serum IgG concentrations of ≥10 and <10 g/L, respectively. This cutoff was based on higher mortality rates in calves with serum IgG <10 g/L. Mortality rates have decreased since 1991, but the percentage of calves with morbidity events has not changed over the same time period. Almost 90% of calves sampled in the USDA National Animal Health Monitoring System's Dairy 2014 study had successful passive immunity based on the dichotomous standard. Based on these observations, a group of calf experts were assembled to evaluate current data and determine if changes to the passive immunity standards were necessary to reduce morbidity and possibly mortality. In addition to the USDA National Animal Health Monitoring System's Dairy 2014 study, other peer-reviewed publications and personal experience were used to identify and evaluate potential standards. Four options were evaluated based on the observed statistical differences between categories. The proposed standard includes 4 serum IgG categories: excellent, good, fair, and poor with serum IgG levels of ≥25.0, 18.0-24.9, 10.0-17.9, and <10 g/L, respectively. At the herd level, we propose an achievable standard of >40, 30, 20, and <10% of calves in the excellent, good, fair, and poor categories, respectively. Because serum IgG concentrations are not practical for on-farm implementation, we provide corresponding serum total protein and %Brix values for use on farm. With one-third of heifer calves in 2014 already meeting the goal of ≥25 g/L serum IgG at 24 h of life, this achievable standard will require more refinement of colostrum management programs on many dairy farms. Implementation of the proposed standard should further reduce the risk of both mortality and morbidity in preweaned dairy calves, improving overall calf health and welfare.

Health and growth of veal calves provided a fatty acid supplement and a dry teat.

Veal calves are at a high risk of disease early in life, which can lead to poor growth. Research is needed to determine interventions that can reduce disease and promote the growth of veal calves. The aim of this study was to determine the effects of fatty acid supplementation and the provision of a dry teat on the incidence of bovine respiratory disease (BRD), navel inflammation, and diarrhea, as well as calf growth. Upon arrival to a commercial veal facility (d 0), 240 Holstein bull calves from 2 cohorts were randomly assigned to 4 treatments using a 2 × 2 factorial arrangement (n = 60/treatment): (1) milk replacer (MR) without fatty acid supplementation and without access to a dry teat (control), (2) MR with fatty acid supplementation (NeoTec5g, Provimi, Brookville, OH) and without access to a dry teat (FAS), (3) MR without fatty acid supplementation and with access to a dry teat (TT), or (4) MR with fatty acid supplementation and with access to a dry teat (FAS+TT). Calves were housed in individual pens from 0 to 9 wk and then paired by treatment at wk 9. Milk replacer was fed twice daily using a step-up program. Fatty acid supplement was added to milk replacer at a feeding rate of 0.5 g/kg of body weight per head per day for the FAS and FAS+TT groups. Health exams were conducted twice weekly for 6 wk to diagnose BRD, navel inflammation, and diarrhea. Body weight, body condition score (BCS), and structural measurements were recorded at wk 0, 5, and 10. Average daily gain (ADG) was calculated for wk 1 to 5, wk 5 to 10, and wk 1 to 10. Health data were analyzed using logistic regression and are reported as relative risk. Body weight, BCS, and structural measurements were analyzed using repeated-measures ANOVA, and ADG was analyzed using a generalized linear model. There was no effect of FAS, TT, or their interaction on body weight or BCS. There was no effect of FAS on ADG wk 1 to 5, wk 5 to 10, or wk 1 to 10. There was a tendency for TT to decrease ADG from wk 1 to 5 but not from wk 5 to 10 or wk 1 to 10. There was a tendency for the interaction of FAS and TT to decrease ADG for wk 1 to 5 but not for wk 5 to 10 and wk 1 to 10. There was no effect of FAS, TT, or their interaction on the risk of BRD, diarrhea, or navel inflammation. We saw no effect of our interventions on calf health or growth. More research is needed to determine whether other factors, such as failure of passive transfer, poor ventilation, barren housing, and low milk allowance in the first few weeks after arrival, may have affected the efficacy of our interventions.

Effects of milk replacer feeding rates on growth performance of Holstein dairy calves to 4 months of age, evaluated via a meta-analytical approach.

Our objective was to evaluate effects of feeding milk replacer (MR) at 2 feeding rates on digestion, intake, and growth of young dairy calves, via a meta-analytical approach using individual data. A database was developed from 10 published studies from the Nurture Research Center (Provimi; Brookville, OH), in which 26 dietary treatments and 491 calves from 0 to 8 wk of age in 13 nursery trials, and 22 dietary treatments and 485 calves from 8 to 16 wk of age in 13 grower trials occurred. Male Holstein calves (n = 491; initial body weight 42.8 ± 4.9 kg) were randomly assigned to 1 of 2 treatments: (1) moderate (MOD), 0.64 to 0.66 kg of dry matter (DM)/d for the first 35 to 39 d, followed by half the allotment per d for 3 to 7 d, fed at the a.m. feeding only; (2) high (HI), 0.92 to 1.07 kg of DM/d for the first 35 to 44 d, followed by half the allotment per d for 5 to 7 d, fed at the a.m. feeding only. Calves were weaned at 6 to 7 wk of age. Milk replacer ranged from 24.8 to 28.6% crude protein (CP) and 17.6 to 20.2% fat; starter ranged from 17.3 to 22.2% CP and 3.0 to 4.3% fat on a DM basis. On d 56 calves (n = 485) moved into pens (4 calves/pen) by treatments and were fed starter (19.4 to 22.3% CP and 3.4 to 4.6% fat, DM basis) blended with 5% hay until d 112. In all nursery trials (d 0 to 56), calves fed MOD had lower average daily gain (ADG; 0.634 vs. 0.545 kg/d), gain/DMI (0.488 vs. 0.466 kg/kg), and hip width change (0.069 vs. 0.064 cm/d), but greater starter intake (0.473 vs. 0.696 kg/d) compared with calves fed HI. Apparent total-tract digestibility of DM (73.3 vs. 78.4%), organic matter (OM; 74.1 vs. 79.0%), CP (74.8 vs. 78.9%), and neutral detergent fiber (NDF; 40.8 vs. 53.9%) were greater for calves fed MOD vs. HI when estimated during wk 8. In all grower trials (d 56 to 112), ADG (1.015 vs. 0.976 kg/d), gain/DMI (0.375 vs. 0.349 kg/kg), and hip width change (0.089 vs. 0.081 cm/d) were greater, but dry feed intake per kg of BW0.75 did not differ (87.8 vs. 88.2 g/d) for calves previously fed MOD vs. HI. Apparent digestibility of DM (78.7 vs. 76.0%), OM (79.8 vs. 77.0%), CP (80.5 vs. 78.4%), and NDF (54.8 vs. 45.8%) were greater for calves fed MOD vs. HI when estimated between wk 11 to 13. Over the entire 112-d period, calves fed MOD had lower ADG (0.805 vs. 0.784 kg/d) but tended to have greater hip width change (8.415 vs. 8.589 cm) compared with calves fed HI. Under the conditions of this study, feeding higher MR rates caused calves to partially lose growth advantage during the weaning transition and further decreased BW gain and structural growth in the grower period (d 56 to 112), which could be due to reductions in nutrient digestibility as a result of feeding more MR.

Effect of amount of milk replacer fed and the processing of corn in starter on growth performance, nutrient digestibility, and rumen and fecal fibrolytic bacteria of dairy calves.

The aim of this study was to evaluate effects of milk replacer (MR) feeding rate and processing of corn in calf starter (CS) on growth performance, nutrient digestibility, and rumen and fecal fibrolytic bacteria in dairy calves. Holstein male calves (n = 48, 2-3 d of age) were randomly assigned to 1 of 4 treatments with a 2 × 2 factorial arrangement of MR level of 0.749 kg of MR/d (LO) or up to 1.498 kg of MR/d (HI); and whole corn or flaked corn in textured CS. Calves were weaned by reducing MR offered by 50% during wk 6. Intakes of MR and CS were recorded daily, whereas body weight (BW) was measured weekly. Rumen fluid and fecal matter were collected at wk 5 and 8 to quantify fibrolytic bacteria and nutrient digestibility. Data were analyzed as a completely randomized design using mixed model ANOVA. Repeated measures were used as appropriate. Calves fed HI had greater average daily gain than calves fed LO at wk 2, 3, 4, and 5, yet at wk 7 calves fed HI had lower average daily gain compared with calves fed LO. Starter intake was greater for calves fed LO compared with HI at wk 4, 5, 6, and 7. During wk 5 and 8, calves fed LO had increased ADF and NDF digestibility compared with calves fed HI. During wk 5, dry matter and organic matter digestibility were lower for LO-fed calves compared with HI-fed calves, but during wk 8 the opposite was observed, with HI-fed calves having lower dry matter and organic matter digestibility than LO-fed calves. At wk 5, Clostridium cluster IV and Butyrivibrio fibrisolvens proportions in rumen fluid tended to be higher and Clostridium cluster IV, Fecalibacterium sp., and Prevotella sp. proportions in fecal matter were higher in calves fed LO compared with HI. From wk 8 to 16, dry matter intake was unaffected by treatment; however, energy efficiency was greater in calves fed LO, causing LO calves to have higher BW gain during this period. Greater starter digestibility was observed for calves fed LO versus HI in concert with increased fibrolytic bacteria proportions (wk 5) in fecal and rumen samples, which resulted in greater postweaning BW gain and similar BW and frame measurements by 16 wk of age. Overall the results show that rate of MR feeding has a larger effect than the processing of corn in CS on performance, fiber digestibility, and rumen and fecal fibrolytic bacterial communities.

Effect of starter form, starch concentration, and amount of forage fed on Holstein calf growth from 2 to 4 months of age.

Young, weaned calves are commonly offered ad libitum forage with limited amounts of starter, in contrast to the suggested amount of approximately 5% forage in the diet due to the limited capacity of the rumen, as well as limited ability to digest high fiber feeds. The objective of this research was to compare 2 types of starters (low starch, pelleted vs. high starch, textured), both fed either ad libitum with 5% chopped hay, or fed at restricted rates with ad libitum long grass hay to calves between 2 and 4 mo of age. In trial 1, 48 calves were housed in group pens (68.4 ± 3.37 kg of initial body weight ± standard deviation; 3 pens of 4 calves/pen) and randomly assigned to 1 of 4 diets: (1) low starch pelleted starter (8% starch) blended with 5% chopped hay fed free choice; (2) high starch textured starter (45% starch) blended with 5% chopped hay fed free choice; (3) low starch pelleted starter (8% starch) fed at a rate up to 2.3 kg of dry matter (DM)/d, with free-choice long grass hay; or (4) high starch textured starter (45% starch) fed at a rate up to 2.3 kg of DM/d, with free-choice long grass hay. Trial 1 was analyzed as a completely randomized design using a 2 × 2 arrangement of treatments. Repeated measures were used as appropriate. Pen was the experimental unit. In trial 2, 48 calves (76.4 ± 1.55 kg of initial body weight; 6 pens of 4 calves/pen) were randomly assigned to 1 of 2 diets: (1) ad libitum access to a blend of 95% high starch textured starter (42% starch) and 5% chopped grass hay; or (2) high starch textured starter fed up to 2.7 kg of DM/d with free-choice long grass hay. Trial 2 was analyzed as for trial 1, without factorial arrangement. Trials were 56 d long. In trial 1, feed efficiency, average daily gain (ADG), and change in hip width were greater for calves fed high versus low starch diet. Final hip width, ADG, DM intake, and change in hip width were greater for calves fed limited chopped versus free-choice long hay diets. In trial 2, intake, feed efficiency, and all growth measurements were greater in calves fed the ad libitum mixed diet compared with those limit-fed starter up to 2.7 kg as fed with ad libitum hay. Ad libitum hay intake was highly variable among pens and differed up to 2.5-fold by the last week of the trials. In both trials, restricted feeding of starter with ad libitum long grass hay reduced total DM intake by 13 to 17%, ADG by 20%, and hip width change by 10 to 23% compared with a blend of 95% starter and 5% chopped grass hay fed ad libitum.

Effects of colostrum and milk replacer feeding rates on intake, growth, and digestibility in calves.

Newborn Holstein male calves (n = 50) born on a single dairy farm were assigned randomly at birth to receive 3 feedings of 1.8 L of pooled maternal colostrum (MC) at 1, 6, and 12 h of age or 1 feeding of 500 g of a colostrum replacer reconstituted to 1.8 L at 1 h of age, followed by 2 feedings of 227 g of a commercial milk replacer (MR) reconstituted to 1.8 L at 6 and 12 h of age (CR). All feedings were administered by esophageal feeder. At 2 to 3 d of age, calves were transported to the experimental facility and assigned within colostrum group to receive 0.66 kg/d dry matter (DM) of MR to 39 d, and then 0.33 kg/d to 42 d (MRM) or 0.77 kg/d of MR DM to d 13, 1.03 kg/d for 22 d, and 0.51 kg/d for 7 d (MRH). The MR contained 25.8% crude protein and 17.6% crude fat (DM basis) and was based on whey proteins and lard as the primary fat source. Calf starter (21.7% crude protein, 15.7% neutral detergent fiber, 37.4% starch, DM basis) and water were available for ad libitum consumption throughout the 56-d study. Serum IgG and total protein were measured at 2 to 3 d of age. Intakes of MR and calf starter were monitored daily. Calf health and fecal scores were also monitored daily. Body weight was measured weekly, and hip width and body condition score were monitored every 2 wk. Digestion of DM, organic matter, crude protein, and ether extract were determined at 1 and 3 wk from 5 calves randomly selected within treatment and using chromic oxide as a digestibility marker added to the MR. Calves fed CR had lower serum IgG and total protein than calves fed MC. Also, calves fed CR grew more slowly, consumed less calf starter, and were less efficient to 56 d than calves fed MC. The number of days calves were treated with veterinary medications was higher when calves were fed CR. Calves fed MC-MRH gained more BW than other calves from 3 to 8 wk of age. Calves fed CR-MRH consumed less calf starter than other calves during wk 7 and 8. Digestion of nutrients at 1 and 3 wk of the study was unaffected by type of colostrum or level of MR fed and did not change from 1 to 3 wk. Over the first 2 mo of life, the calves fed MRH consumed less calf starter than calves fed MRM, but average daily gain or hip width change did not differ. One feeding of CR followed by 2 feedings of MR in the first 24 h likely reduced absorption of IgG from CR and contributed to differences in health and growth. Differences in animal performance observed in this study were unrelated to MR digestibility.

Effects of fatty acids and calf starter form on intake, growth, digestion, and selected blood metabolites in male calves from 0 to 4 months of age.

The objective of this research was to determine if form of calf starter (CS) and addition of a fatty acid blend (FA) influenced intake, growth, digestion, and indices of immune status and stress in calves from 0 to 4 mo of age. Male Holstein calves [n = 48; 41.9 kg of body weight (BW), standard error = 0.7; 2 to 3 d of age] were assigned to receive reconstituted whole milk powder [0.66 kg of dry matter (DM)/d to 39 d, then 0.33 kg of DM/d to weaning at 42 d] without or with added FA. Calf starters were textured (pellet, whole oats, whole corn) or pelleted and were offered for ad libitum consumption from 0 to 56 d, then blended with 5% chopped grass hay and fed from d 57 to 112. Starters contained 20% crude protein (CP) and 38 to 40% starch in the DM. From d 0 to 56, calves were housed individually. From d 57 to 112, calves were grouped into pens by treatment (n = 4/pen). Form of CS during the initial 56 d had no effect on intake or growth, though days with fluid feces (fecal score ≥2.5) were greater when calves were fed textured CS. Feeding FA during the initial 56-d increased average daily BW gain, gain-to-feed ratio, and change in hip width, and reduced the number of days calves were treated with antibiotics. During d 57 to 112, CS form had no effects on any performance measure. Adding FA to CS increased average daily BW gain and hip width change, and tended to improve efficiency of BW gain. Total-tract digestibility was estimated at 4, 6, and 8 wk with 5 calves per treatment, and at 10, 13, and 16 wk of age using pen (n = 3 per treatment) as the experimental unit. Feeding FA increased or tended to increase total-tract digestion of DM, organic matter, starch, neutral detergent fiber (NDF), acid detergent fiber (ADF), CP, and fat at one or more measurement periods. Calves fed a textured CS increased or tended to increase digestion of DM, organic matter, starch, sugar, NDF, ADF, and CP during wk 6 and 8. However, during the second 56-d phase, feeding textured CS reduced or tended to reduce digestion of DM, organic matter, starch, NDF, ADF, and fat during wk 13 and 16. Inclusion of FA in milk increased serum bactericidal activity before weaning. Serum haptoglobin concentration increased 3 d postweaning when calves were fed textured CS. Feeding FA improved animal health, digestion, and performance. Form of CS had few effects on animal performance.