A limited amount of research is available related to the rumen microbiota of calves, yet there has been a recent spike of interest in determining the diversity and development of calf rumen microbial populations. To study the microbial populations of a calf's rumen, a sample of the rumen fluid is needed. One way to take a rumen fluid sample from a calf is by fistulating the animal. This method requires surgery and can be very stressful on a young animal that is trying to adapt to a new environment and has a depressed immune system. Another method that can be used instead of fistulation surgery is a rumen pump. This method requires a tube to be inserted into the rumen through the calf's esophagus. Once inside the rumen, fluid can be pumped out and collected in a few minutes. This method is quick, inexpensive, and does not cause significant stress on the animal. This technical note presents the materials and methodology used to convert a drenching system into a rumen pump and its respective utilization in 2 experiments using dairy bull calves.

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The present study was conducted to examine how dairy heifer calves would respond to a heat stress bout in terms of growth relative to nutrient intake. Nine Holstein and 2 Jersey heifer calves (n = 11) were individually housed and enrolled in a study containing 3 experimental periods (P). Period 1 lasted 7 d during which baseline measurements were obtained. During period 2 (7 d), calves were subjected to diurnal heat stress (dHS) employed by maintaining barn temperature at 33°C (92°F) from 0900 to 2100 h and letting it be equilibrated with outside temperature [24°C (75°F)] during the night. Follow-up measurements were made over 4 d (P3) immediately after dHS. Calves consumed 25% less feed during the day but compensated for it consuming more feed (35%) in night during dHS. Despite DMI (kg/d) being similar between dHS and baseline, ADG and feed efficiency decreased significantly during dHS. These effects are likely consequence of nutrient repartitioning towards the activated immune system and away from productive processes (i.e., growth), as blood haptoglobin increased 3-fold during dHS. Nonetheless, calves exhibited compensatory growth concurrently with increased DMI and drinking water per unit of DMI immediately following dHS. Overall, dHS severely hampers growth and feed efficiency of dairy heifer calves despite unaltered DMI relative to baseline. Understanding nutrient partitioning in calves during and after heat stress could help mitigate the adverse effects and help calves effectively recover from heat stress.

The objective of this study was to examine the effects of a Zn-methionine complex in diet on milk yield, milk component yields, SCC, and milk Zn concentration of Holstein cows around peak lactation. After matching for parity and days in milk (DIM), 12 lactating Holstein cows (67 ± 2.5 DIM; 1385 ± 43 kg BW) were assigned to one of two dietary treatments: 1) control (CTL, n = 6), a TMR diet with 74 mg/kg added Zn in the form of zinc sulfate, n = 6) or 2) CTL supplemented with Zn-methionine complex (Zn-Met, n = 6) providing additional 20 mg of Zn/kg (512 mg/head/d). Dry matter intake (DMI) was lower by 0.8 kg/d for Zn-Met than CTL throughout the study (P = 0.05). Milk yield of Zn-Met decreased compared to CTL (40 vs 42 kg/d, P = 0.01) during the first 35 d but had similar milk yield during the last 35 d of the study. Milk protein and fat percentages, and fat yield were not different between treatments. Milk protein yield was similar between treatments during the first 35 d but tended to increase for Zn-Met (1.41 vs. 1.33 kg/d, P = 0.10) during rest of the study. Cows receiving Zn-methionine complex tended to have lower SCC (126 vs 328 ×10 3 cells/mL, P = 0.07) and greater concentration of Zn (4.48 vs 4.06 ppm, P = 0.05) in milk throughout the study. Overall, the present Znmethionine complex tended to improve milk protein yield and SCC more prominently as feeding progressed. However, it decreased DMI suggesting a negative impact on palatability of the diet.

Phytogenic feed additives that contain anti-inflammatory and antioxidant properties may have potential to reduce inflammation and oxidation observed during bouts of heat stress. The trial objective was to determine the effects of a phytogenic feed additive on markers of stress in heifers subjected to diurnal heat stress (dHS). Eighteen Holstein and four Jersey heifers (5–6 months of age; d1 BW=205±9 kg) were assigned to two dietary treatments (n = 11) based on breed and age; 1) a basal TMR diet (CTL), 2) CTL supplemented with 0.25 g/head/d of a proprietary blend of phytogenics (PFA; BIOMIN America, Inc., Overland Park, KS). Heifers were housed individually and fed their respective treatments for 14d prior to dHS (d-14-1), subjected dHS (d1-7), and followed through a recovery period (d8-11). Weights were collected at d1 (baseline), d7 (end of dHS), and d11 (end of recovery). The temperature set point was assigned at 33°C from 0900 to 2100 h and allowed to equilibrate with outside temperature during night (24°C) for a total of 7d dHS. Total DMI (tDMI) and DMI from 0900 to 2100 h (hsDMI) were recorded daily. Serum was collected at d1, 2, 7 and 11 to determine effect of treatment on markers of oxidation, inflammation, and stress. Treatment effects were analyzed using PROC MIXED in SAS with treatment and time as fixed effects and heifer as a random effect. Temperature humidity index during dHS was greater during the day (84.5) versus night (73.3). There were no treatment differences (P>0.05) in d 0–11 on ADG, ADFI, or GF between treatments. However, PFA numerically increased hsDMI, reduced (P< 0.05) haptoglobin and tended to reduce (P< 0.10) lipopolysaccharide binding protein compared with CTL. Overall, dietary PFA may be a potential strategy to mitigate the stresses that heifers experience during dHS.