A.J. Heinrichs

It is critical that bovine maternal colostrum is fed to newborn calves during their first hours of life. Colostrum is the secretion a cow produces after mammary involution that is rich in various nutrients. In addition to the nutritive value for newborn calves, immunoglobulins are of interest due to their role in developing the naïve immune system of calves at birth. The process by which a calf acquires immunity via absorption of immunoglobulins is defined as passive immunity. When calves consume an adequate amount of immunoglobulins, they are classified as having successful passive immunity (SPI). In contrast, if they are deprived of adequate colostrum, they are considered to have had a failure of transfer of passive immunity (FPI). Transfer of passive immunity is assessed by measuring serum IgG concentrations at 24 to 48 h of age. The major factors that influence whether a calf has SPI or FPI are colostrum IgG concentration, quantity fed, and age of calf at colostrum feeding. Monitoring apparent efficiency of immunoglobulin absorption in calves is often recommended to evaluate overall colostrum management practices. Serum IgG analyses can be determined with direct (radial immunodiffusion) or indirect (refractometry) methods and used to assess SPI or FPI prevalence.

The objectives of this study were to investigate the effect of starch and protein interaction on rumen environment, in situ digestion, and total-tract digestibility of nutrients in weaned dairy calves between 8 and 16 wk of age. Sixteen rumen-cannulated calves were randomly divided into 4 dietary treatment groups with 4 calves fed in each treatment. The treatment diets had 2 levels of starch [18%, low starch (LS), or 38%, high starch (HS)] and 2 levels of protein [16%, low protein (LP), or 22%, high protein (HP)] on a dry matter (DM) basis in calf grower: (1) LPLS, (2) LPHS, (3) HPLS, and (4) HPHS. Calves were fed for ad libitum intake (95% assigned grower and 5% grass hay), and refusals were collected weekly. Total-tract digestibility collection and in situ digestibility procedures were performed for each calf at 11 and 15 wk. Samples for in situ digestibility, grass hay (GH), soybean hulls (SBH), wheat middlings (WM), ground corn (GrC), and soybean meal (SBM) were incubated for 9 and 24 h. There was no starch and protein interaction on total-tract digestibility of calves. Total-tract DM, neutral detergent fiber (NDF) and acid detergent fiber (ADF) digestibility, and feed efficiency were affected by both protein and starch inclusion level in calf diet. Total-tract starch digestibility was lower for LS diets. Dry matter digestibility and feed efficiency were greater in calves fed HP and HS diets compared with calves fed LP and LS diets, respectively. Fiber digestibility (NDF and ADF) was less in calves fed HS diets compared with calves fed LS diets but was greater in calves fed HP diets compared with calves fed LP diets. Level of protein did not affect in situ DM and NDF disappearance of GH, but HP increased in situ DM and NDF disappearance of SBH. High-starch diets decreased DM and NDF disappearance of both GH and SBH. At 20 h after feeding, ruminal pH was 0.51 unit higher in calves fed HPHS compared with calves fed LPHS. Total ruminal VFA and proportion of propionate was greater with HS versus LS, whereas proportion of acetate was greater with LS versus HS. The DM disappearance of SBM and WM and NDF disappearance of WM was greater for calves fed HPHS compared with calves fed LPHS at 11 wk of age. In our study, when HP was fed with HS, rumen pH, in situ digestion of WM and SBM, and total-tract digestion of DM, NDF, and ADF increased. This provides evidence for starch-protein interaction in the rumen of recently weaned dairy calves. Improvements in total-tract and in situ digestibility suggest that both protein and starch levels are important for 8- to 16-wk-old calves.

Summary: Limiting total mixed ration (TMR) availability from 24 to 19 h/d changed the eating patterns of lactating dairy cows. Availability of ad libitum hay also made a significant difference in dry matter intake (DMI) patterns, as shown by the 95% confidence limits in the shaded bands. Rumen pH pattern throughout the day was modified in restricted-fed cows, but ranges in values were similar to those of ad libitum-fed cows. The changes in intake patterns over time indicate that when feeding TMR diets, cows can adjust to the changes in feed availability and access to long hay.

The objective of this experiment was to determine the effects of replacing soybean hull (SBH) pellets with grass hay (GH) on growth, intake, total-tract digestibility, and rumen microbial nitrogen production of weaned dairy calves from 8 to 16 wk of age. Holstein calves (n = 16) were randomly assigned to 1 of 4 rations containing, on a dry matter (DM) basis, 76% grower with the remaining 24% being made up of different amounts of SBH pellets and GH [0% GH, 24% SBH (0GH); 8% GH, 16% SBH (8GH); 16% GH, 8% SBH (16GH); and 24% GH, 0% SBH (24GH)]. Calves were weaned at 6 wk, housed individually, and studied from 8 to 16 wk of age. From 8 to 9 wk of age calves were offered a ration consisting of 50% of texturized starter (20% CP and 35% starch), which was offered from 3 d of age, and 50% of their assigned ration. From 9 wk until the end of the study, calves were offered 100% of their assigned ration. Intake and body weight were measured weekly, and frame measurements were taken at the beginning and end of the study. Animal behavior observations were recorded every 5 min over a 24-h period at 10 and 14 wk of age. Total fecal and urine collection was conducted for 4 d consecutively at 11 and 15 wk of age. Feed and feces were evaluated for DM, N, neutral detergent fiber, acid detergent fiber, and starch to determine total-tract digestibility. Feces were evaluated for geometric mean particle length (Xgm) and particle size distribution. Urine was evaluated for N, creatinine, urea, and total purine derivatives to estimate microbial N yield. Calves offered 0GH and 8GH had a 20% increase in intake, average daily gain (1.23, 1.27, 0.89, and 0.71 kg/d for 0GH, 8GH, 16GH, and 24GH, respectively), and feed efficiency compared with 16GH and 24GH. Calves offered 8GH had the greatest levels of neutral detergent fiber and acid detergent fiber digestibility, as well as the greatest estimated microbial N yields. Inclusion of forage increased rumination time (2.75, 6.89, 7.18, and 8.16 h/d for 0GH, 8GH, 16GH, and 24GH, respectively) and decreased fecal Xgm by ~35% compared with calves offered 0GH. In the current study, increasing the replacement of SBH with GH beyond 8% was detrimental to weaned calf performance. These results indicate that when diets containing 8% GH and 16% SBH were fed to recently weaned calves, rumen functionality and feed efficiency were optimized compared with the other GH-SBH combinations.

The objectives of this study were to investigate the association of body weight (BW) at first calving (BWFC) and maturity rate (MR; BWFC as a percentage of mature BW) with first-lactation 305-d milk yield (FLMY), milk yield (MY) in the 24 mo following first calving (24MMY), herd life, and BW change (BWC) through the first month of lactation in Holstein heifers. We retrieved daily milk production records and daily BW records from AfiFarm (S. A. E. Afikim, Kibbutz Afikim, Israel). The data set included daily records for 1,110 Holstein cows from The Pennsylvania State University (n = 435,002 records) and 1,229 Holstein cows from University of Florida (n = 462,013 records) that calved from 2001 to 2016. Body weight at first calving was defined as mean BW from 5 to 10 d in milk of the first lactation, whereas BWC represented change from BWFC to average BW from 30 to 40 d in milk. First-lactation 305-d MY and 24MMY were analyzed with a linear model that included effects of farm-year-season of calving, age at calving, and quintiles of BWFC, MR, or BWC. Body weight change was analyzed with the same model to determine associations with BWFC. Survival analysis was performed to estimate the effect of BWFC on survival. Heifers in the top 60% of BWFC had significantly higher FLMY (10,041 to 10,084 kg) than lighter heifers (9,683 to 9,917 kg), but there was wide variation in every quintile, and no relationship of BWFC and FLMY existed within the top 60%. Relationships between BWFC and 24MMY were not significant. Heifers with higher BWFC or MR lost significantly more BW in early lactation. Although BWFC and MR were significant predictors of FLMY, they accounted for <3% of variation in FLMY or 24MMY, suggesting that BWFC and MR are not primary contributors to variation in MY. Compared with the lightest heifers, the heaviest heifers were 49% more likely to be culled at a given time. These data indicated that, among heifers managed similarly, heavier heifers produced more milk in first lactation than lighter heifers but lost more BW, faced a higher risk of being culled, and did not produce more milk in the long term. Based on our data, heifers that reach between 73 and 77% MR at first calving can produce more milk in their first lactation without sacrificing long-term MY and herd life.

The objective was to determine effects of increasing grass hay (GH) inclusion level on weaned dairy calf growth, intake, digestibility, and ruminal fermentation. Holstein calves (n = 45) were randomly assigned to 1 of 3 total mixed rations with increasing GH [10, 17.5, or 25% on a dry matter (DM) basis; LGH, MGH, or HGH, respectively]. Calves were weaned at 6 wk of age, housed individually, and studied from 7 to 16 wk of age. Rations, consisting of texturized calf starter (20% crude protein) and coarsely chopped GH, were offered ad libitum as separate components from 7 to 9 wk of age. After 9 wk, feed was offered as a total mixed ration containing the assigned level of GH and fed according to the clean bunk feeding strategy as a means of limiting refusals. Initial 9-wk body weight was 81.6 ± 9 kg (mean ± standard deviation). Intake and growth were measured weekly. Blood samples were collected at 9, 10, 12, 14, and 16 wk of age for analysis of plasma glucose and β-hydroxybutyrate. Total fecal collection (12 calves; 4 per treatment) was conducted at 11 and 15 wk of age for 4 d consecutively. Rumen samples were collected over the final 24 h of each fecal collection period to evaluate pH and volatile fatty acid profile. Feeds and feces were evaluated for DM, neutral detergent fiber, acid detergent fiber, and starch to estimate total-tract digestibility. Intake and weight gain were analyzed from 7 to 9 wk and 9 to 16 wk, representing pretreatment and treatment periods. No differences were observed between treatments from 7 to 9 wk. However, differences were found from 9 to 16 wk. Final body weight, average daily gain, DM intake, and metabolizable energy intake all decreased with increased GH. However, skeletal frame measurements did not vary between treatments. Plasma β-hydroxybutyrate tended to decrease with increased GH. No differences were observed in DM or starch digestibility, but neutral detergent fiber and acid detergent fiber digestibility increased with increased GH. Mean rumen pH and total volatile fatty acid did not change with increasing GH inclusion; however, there was an interaction with time indicating that ruminal fermentation patterns throughout the day were different for calves offered MGH and HGH versus those offered LGH. These results indicate that feeding levels of GH >10% reduce growth and intake before 16 wk and alter ruminal fermentation patterns.

The objective of this study was to determine effects of various forages and live yeast culture on intake, growth, nutrient digestibility, and ruminal fermentation of weaned dairy calves. Holstein calves (n = 45) were randomly assigned to 2 × 3 factorial treatments: live yeast culture or no yeast and alfalfa haylage (AH), corn silage (CS), or grass hay (GH). Calves were weaned at 6 wk of age, housed individually, and studied from 7 to 16 wk of age. Rations, consisting of an 18% crude protein texturized grower (yeast or no yeast) and assigned forage, were offered as separate components until 9 wk of age. After 9 wk, diets were offered as a total mixed ration (TMR). Concentrate intake was capped at 2.25 kg of dry matter (DM)/d, and forage was offered ad libitum. The TMR contained equal forage neutral detergent fiber (8 ± 0.5%) on a DM basis for each basal diet. Calves were fed TMR to limit concentrate intake, and additional forage was offered ad libitum after 8 h if the entire TMR allotment was consumed. Total fecal collection (12 calves) was conducted for 4 d at 11 and 15 wk of age. Feeds and feces were evaluated for DM, neutral detergent fiber, acid detergent fiber, and starch to calculate digestibility. On the last day of fecal collection, rumen samples were collected to evaluate pH and volatile fatty acid (VFA) profile. Metabolizable energy and DM intake was least for calves consuming GH compared with other forages. Forage intake (% of DM intake) increased as calves aged (AH = 20 to 44.4%, CS = 24.5 to 37.6%, GH = 11.3 to 32.3% at 10 and 16 wk of age, respectively). Calves on CS had the greatest average daily gain and empty body weight gain, and calves on GH had the least. Calves on GH tended to have the lowest final body weight. There were no differences in structural growth. Digestibility of DM decreased with age. Fiber digestibility was least for calves on CS, and starch digestibility was least for calves on AH. Mean and minimum rumen pH increased with age. Forage offered changed VFA profile and there was an interaction between yeast and forage on VFA profile. These results indicated that recently weaned calves perform well on AH, CS, or GH and have minimal benefit from yeast supplementation. Feeding GH reduced weight gain, but all calves achieved a level of gain to meet growth goals for breeding and freshening. Furthermore, the ability to consume large portions of the ration as forage allows for more economical diets to be fed.

Serum IgG concentrations in dairy calves change throughout their first weeks of life, peaking at 24 h and then steadily decreasing until calves begin to produce endogenous IgG. The objective of this study was to observe serum IgG dynamics from birth until 16 wk of life in calves fed either maternal colostrum (MC) or colostrum replacer (CR). A total of 44 Holstein calves were randomly assigned to 1 of the 4 colostrum treatments and followed throughout the study. Treatments consisted of feeding high-quality MC, low-quality MC supplemented with CR, or 1 of 2 distinct levels of IgG concentration from CR. Overall, the interaction between type of colostrum fed and sampling time was significant. Individual differences for this effect were found at d 1, 7, 14, 21, 28, and 98, while the other time points were not different.

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 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.

The objective was to determine the effects of converting calves from a component-fed ration to a total mixed ration (TMR) at 8, 10, or 12 wk of age on intake, growth, and nutrient digestibility. Holstein calves (n = 40) were randomly assigned to 1 of 4 groups (no TMR, TMR conversion at 8, 10 or 12 wk; T0, T8, T10, and T12, respectively). Calves were weaned at 6 wk of age, housed individually, and studied from 7 to 14 wk of age. Rations, consisting of a 20% crude protein texturized starter and grass hay, were offered ad libitum as separate components or as a TMR with 85% starter and 15% grass hay on a dry matter (DM) basis. Intakes and body weights (BW) were measured weekly. Component intake for TMR was calculated from the proportion of grass hay and starter contained in the TMR. Fecal grab samples were collected every 9 h over 3 d for a total of 8 samples that formed a composite at 9, 11, and 13 wk of age from the same 4 calves per group. Rumen fluid samples were collected via esophageal tube at -1, 0, 3, and 7 d relative to conversion from component to TMR. Feed and feces were evaluated for DM, neutral detergent fiber, acid detergent fiber, and acid detergent lignin (internal flow marker) to estimate digestibility. Average daily gain and final BW tended to be least for T8. Empty BW gain was significantly less for T8 than for T0 but not different from T10 or T12 (T0 = 1.07, T8 = 0.93, T10 = 1.02, T12 = 1.04 kg/d). Hip growth tended to be least for T8 and resulted in lower final hip width (T0 = 25.9, T8 = 25.2, T10 = 25.6, T12 = 25.8 cm). Intake tended to be reduced for calves converted to TMR earlier. Throughout the study, calves fed TMR ate more hay and less starter than component-fed calves. Metabolizable energy intake was less for T8 versus T0 but not different from T10 or T12 (T0 = 8.46, T8 = 7.55, T10 = 8.01, T12 = 8.23 Mcal/d). We observed no differences in feed efficiency for the duration of the study. Differences in DM digestibility were not observed, but fiber digestibility was greater for calves fed TMR at 9, 11, and 13 wk of age. Conversion to TMR increased rumen pH. These results indicate that TMR conversion increased hay consumption and subsequently decreased starter and total DM intake. This led to reduced weight and structural growth; however, calves that were converted to TMR as early as 8 wk still achieved adequate growth. The increase in rumen pH and subsequent increase in fiber digestibility allowed for calves to be converted to a 15% grass hay TMR as early as 8 wk and still achieve desirable growth goals.