Fat composition of milk replacer influences postprandial and oxidative metabolisms in dairy calves fed twice daily

Milk replacers (MR) for calves contain alternative fat sources as substitute for milk fat. This substitution leads to differences in fat properties, such as the fatty acid profile and the triglyceride structure. This study evaluated how fat composition in MR affects gastrointestinal health, blood redox parameters, and postprandial metabolism in calves fed twice daily. Forty-five individually housed male Holstein-Friesian calves (2.3 ± 0.85 d of age) were assigned to 1 of 15 blocks based on the age and the day of arrival. Within each block, calves were randomly assigned to 1 of 3 experimental diets and received their respective diet from arrival until 35 d after arrival. The 3 experimental diets (n = 15 per treatment group) consisted of an MR with a blend of vegetable fats containing rapeseed and coconut (VG), an MR with only animal fats from lard and dairy cream (AN), and an MR containing a mixture of animal and vegetable fats including lard and coconut (MX). The fatty acid profile of each MR was formulated to resemble that of bovine milk fat while using only 2 fat sources. All MR were isoenergetic, with 30% fat (% DM), 24% crude protein, and 36% lactose. Chopped straw and water were available ad libitum from arrival onward but no starter feed was provided. Daily milk allowances were 6.0 L from d 1 to 5, 7.0 L from d 6 to 9, and 8.0 L from d 10 to 35, divided into 2 equal meals and prepared at 135 g/L (13.5% solids). Fecal appearance was scored daily; calves were weighed and blood was drawn on arrival and weekly thereafter. Urine and feces were collected over a 24-h period at wk 3 and 5 to determine apparent total-tract digestibility and assess gastrointestinal permeability using indigestible markers. Postprandial metabolism was evaluated at wk 4 by sequential blood sampling over 7.5 h, and the abomasal emptying rate was determined by acetaminophen appearance in blood. Fat composition in MR did not affect growth, MR intake, gastrointestinal permeability, nor nutrient digestibility. The percentage of calves with abnormal fecal scores was lower at wk 2 after arrival in calves fed VG than MX, whereas AN did not differ from the other treatments. Calves fed AN and MX had higher thiobarbituric acid reactive substances measured in serum than VG, whereas plasma ferric-reducing ability was greater in calves fed MX than VG. Postprandial acetaminophen concentrations did not differ across treatment groups, but the area under the curve was smaller in calves fed VG than in the other 2 treatments, which is indicative of a slower abomasal emptying. Postprandial serum triglyceride concentration was greater in calves fed AN than VG, whereas MX did not differ from the other treatments. Based on these outcomes, all 3 fat blends can be considered suitable for inclusion in MR for calves.

Effects of enriching IgG concentration in low- and medium-quality colostrum with colostrum replacer on IgG absorption in newborn Holstein calves

Ingestion and absorption of greater quantities of IgG are required to increase serum IgG levels in newborn calves. This could be achieved by adding colostrum replacer (CR) to maternal colostrum (MC). The objective of this study was to investigate whether low and high-quality MC can be enriched with bovine dried CR to achieve adequate serum IgG levels. Male Holstein calves (n = 80; 16/treatment) with birth body weights (BW) of 40 to 52 kg were randomly enrolled to be fed 3.8 L of the following combinations: 30 g/L IgG MC (C1), 60 g/L IgG MC (C2), 90 g/L IgG MC (C3), C1 enriched with 551 g of CR (60 g/L; 30-60CR), or C2 enriched with 620 g of CR (90 g/L: 60-90CR). A subset of 40 calves (8/treatment) had a jugular catheter placed and were fed colostrum containing acetaminophen at a dose of 150 mg/kg of metabolic body weight, to estimate abomasal emptying rate per hour (kABh). Baseline blood samples were taken (0 h), followed by sequential samples at 1, 2, 3, 4, 5, 6, 8, 10, 12, 24, 36, and 48 h relative to initial colostrum feeding. Results for all measurements are presented in the following order, unless otherwise stated: C1, C2, C3, 30-60CR, and 60-90CR. Serum IgG levels at 24 h were different among calves fed C1, C2, C3, 30-60CR, and 60-90CR: 11.8, 24.3, 35.7, 19.9, and 26.9 mg/mL ± 1.02 (mean ± SEM), respectively. Serum IgG at 24 h increased when enriching C1 to 30-60CR, but not from C2 to 60-90CR. Similarly, apparent efficiency of absorption (AEA) values for calves fed C1, C2, C3, 30-60CR, and 60-90CR were different: 42.4, 45.1, 43.2, 36.3, and 33.4% ± 1.93, respectively. Enriching C2 to 60-90CR reduced AEA, and enriching C1 to 30-60CR tended to decrease AEA. The kABh values for C1, C2, C3, 30-60CR, and 60-90CR were also different: 0.16, 0.13, 0.11, 0.09, and 0.09 ± 0.005, respectively. Enriching C1 to 30-60CR or C2 to 60-90CR reduced kABh. However, 30-60CR and 60-90CR have similar kABh compared with a reference colostrum meal (90 g/L IgG, C3). Even though kABh was reduced for 30-60CR, results indicate that C1 has the potential to be enriched and achieve acceptable serum IgG levels at 24 h without affecting AEA.

Effects of milk replacer feeding rate and frequency of preweaning dairy calves in the southeastern United States: Performance, abomasal emptying, and nutrient digestibility

To evaluate the effects of milk replacer (MR) feeding rate (FR) and frequency (FF) on performance, abomasal emptying, and nutrient digestibility in the southeastern United States, Holstein calves (n = 48/season) were enrolled at 8 d of age (DOA) during summer [June to August, body weight (BW; mean ± SD) = 40.71 ± 4.35 kg] and winter (November to January, BW = 42.03 ± 3.83 kg). Within season, calves were randomly assigned to 1 of 4 treatments in a 2 × 2 factorial arrangement including 2 FR [0.65 (low) or 0.76 kg of solid per day (high) of a 26% crude protein and 17% fat MR], and 2 FF [2× (0700 and 1600 h) or 3× (0700, 1600, and 2200 h) daily]. Calves were housed in polyethylene hutches and managed similarly throughout the trial. Milk replacer (12.5% solids) was fed to calves based on their respective treatments until 42 DOA, when MR allowance was reduced by 50% and offered once a day (0700 h) for the following 7 d until weaning. Calves remained on trial until 63 DOA. Calf starter and water were offered ad libitum. Ambient temperature and relative humidity inside and outside hutches were measured hourly. Starter and MR intakes were recorded daily. Respiration rate and rectal temperature were recorded 3 times a week. Structural growth and BW were measured weekly. Acetaminophen (50 mg/kg of BW) mixed with MR was fed to a subset of calves (0700 h, n = 10/treatment per season) on 20 DOA. Plasma was collected at 15, 30, 60, 90, 120, 150, 180, 210, 240, 270, 300, 330, 360, 420, and 480 min after feeding, to analyze acetaminophen. The acetaminophen concentration-time curve was modeled to the first derivative of Siegel's modified power exponential equation, and the time for plasma acetaminophen to reach maximum (Tmax) was calculated to evaluate abomasal emptying rate. During the pre- (14.9-17.9 DOA) and postweaning (51.0-54.0 DOA) periods, a subset (n = 8/treatment per season) of calves was used to determine the apparent digestibility of nutrients, using chromic oxide as the external marker. Feeding 3× reduced preweaning respiration rate during summer and reduced rectal temperature during winter. Increasing FR improved BW gain and structural growth. Feeding more times per day tended to improve growth during winter but not summer. We found no effect of treatment on nutrient digestibility. Increasing FR had no effect on Tmax during winter but tended to delay Tmax of plasma acetaminophen during summer. Regardless of season, increasing FF lowered Tmax of plasma acetaminophen. In conclusion, increasing FF accelerated abomasal emptying and might reduce heat load of preweaning dairy calves but improved growth only during winter. Increased MR allowance improved growth in both seasons but delayed abomasal emptying only under heat stress conditions.