Application of Near-Infrared Reflectance Spectroscopy for Predicting Chemical Composition of Feces in Holstein Dairy Cows and Calves

Traditional methods for determining the chemical composition of cattle feces are uneconomical. In contrast, near-infrared reflectance spectroscopy (NIRS) has emerged as a successful technique for assessing chemical compositions. Therefore, in this study, the feasibility of NIRS in terms of predicting fecal chemical composition was explored. Cattle fecal samples were subjected to chemical analysis using conventional wet chemistry techniques and a NIRS spectrometer. The resulting fecal spectra were used to construct predictive equations to estimate the chemical composition of the feces in both cows and calves. The coefficients of determination for calibration (RSQ) were employed to evaluate the calibration of the predictive equations. Calibration results for cows (dry matter [DM], RSQ = 0.98; crude protein [CP], RSQ = 0.93; ether extract [EE], RSQ = 0.91; neutral detergent fiber [NDF], RSQ = 0.82; acid detergent fiber [ADF], RSQ = 0.89; ash, RSQ = 0.84) and calves (DM, RSQ = 0.92; CP, RSQ = 0.89; EE, RSQ = 0.77; NDF, RSQ = 0.76; ADF, RSQ = 0.92; ash, RSQ = 0.97) demonstrated that NIRS is a cost-effective and efficient alternative for assessing the chemical composition of dairy cattle feces. This provides a new method for rapidly predicting fecal chemical content in cows and calves.

Short communication: Impact of corn grain particle size on production performance of lactating dairy cows

Corn grain particle size has the potential to influence the performance of lactating dairy cows and the overall profitability of a dairy farm. The objective of this study was to evaluate the productive performance of lactating cows fed diets containing finely or coarsely ground corn grain. Fifty lactating Holstein cows (n = 50; 10 primiparous and 40 multiparous), averaging (mean ± standard deviation, SD) 658 ± 64 kg of BW, 38.8 ± 7.3 kg of milk/d, and 155 ± 80 DIM, were fed diets with finely ground corn grain (FGC) or coarsely ground corn grain (CGC) in a randomized block design with a 28-d treatment period. Finely and coarsely ground corn grain had an average particle size of 660 and 915 µm, respectively. Dry matter intake (DMI) was reduced (p < 0.01) for cows fed FGC (22.1 vs. 21.2 kg d-1). Milk yield and efficiency were not affected by treatments (37.9 vs. 36.8 kg d-1; p = 0.12 and 1.78 vs. 1.79; p = 0.15). Concentrations of milk protein and fat, as well as other milk solids, were unaffected (p > 0.05) by treatments. Fecal starch (FS) concentrations were greater (p < 0.01) for cows fed CGC (7.0 vs. 4.9%), whereas plasma concentrations of D-lactate were greater (p < 0.05) for cows fed FGC (98.5 vs. 79.7 µM). Overall, feeding finely ground corn grain increased total-tract starch digestibility and reduced DMI while maintaining milk yield.

Reduction in mucosa thickness is associated with changes in immune function in the colon mucosa during the weaning transition in Holstein bull dairy calves

This study aims to characterize changes in the structure and the molecules related to immune function in the colon mucosa in dairy calves during the weaning transition (weaned at week 6 of age). Colon mucosa thickness, measured at week 5 to 8 and 12 of age, decreased for 2 weeks after weaning, but then recovered. Colon mucosa's transcriptome profiling at week 5, 7, and 12 of age was obtained using RNA-sequencing. Functional analysis showed that pathways related to immune function were up-regulated postweaning. A weighted gene co-expression network analysis identified 17 immune function related genes, expressed higher postweaning, which were negatively correlated with colon mucosa thickness, suggesting that these genes may be involved in colon mucosa inflammation and recovery from mucosa thickness decrement during the weaning transition. As such, it is important to determine the function of immune cells in the colon mucosa during the weaning transition in dairy calves.

Ruminal responses, digestibility, and blood parameters of beef cattle fed diets without forage with different hybrids and processing of the corn

The objective of this study was to evaluate the effects of corn hybrid and processing methods on intake and digestibility of nutrients, rumen fermentation and blood metabolites of steers fed no-forage finishing diets. Four ruminally fistulated Nellore castrated steers (502 ± 15 kg initial body weight) were distributed in a 4 × 4 Latin square design with a 2 × 2 factorial arrangement consisting of two corn hybrids (semi-dent and flint) and two processing methods (dry milled and high moisture grain). Interactions of hybrid and processing methods were observed on intake of dry matter (DM), organic matter (OM) and crude protein (CP), as well as on digestibility of DM and CP, rumen pH and ammonia nitrogen (N-NH₃ ). There was no interaction between hybrid and processing for the volatile fatty acids (VFA) total, acetate (C2), propionate (C3), isobutyric (iC4) and valeric (nC5) concentrations. VFA total concentration shown an average of 103.4 mmol/L. The C2 and C3 concentrations had no effect of the hybrid or processing with averages of 58.7 mmol/L for C2, and 31.3 mmol/l for C3. There was an effect of the processing method on starch consumption and fecal pH, the highest values were observed in grains with high moisture content. Starch digestibility was 0.89 g/g in dry milled and 0.96 g/g in high moisture corn. The greatest digestibility of starch in high moisture corn, irrespective of the corn hybrid, provided evidence of an increase in the energy supply, which may improve the feed efficiency and growth performance of cattle fed no-roughage finishing diets.

Nutrient intake, digestibility, and serum metabolites in dairy cows fed diets differing in starch concentration with palmitic acid or stearic acid supplementation postpartum

The present study determined the effect of supplementing palmitic acid (PA) and stearic acid (SA) on the nutrient intake, digestibility, and serum metabolites of dairy cows fed two different starch levels during the postpartum period. Forty-four multiparous Holstein cows were used in a completed randomized block based on their parity and previous milk yield. Dietary treatments were arranged in a 2 × 2 arrangement with two dietary starch levels (HS: 260 g/kg of diet dry matter (DM) vs LS: 210 g/kg of diet DM) and two fat supplements rich in PA or SA at 15 g/kg of diet DM. Increasing the starch concentration of the postpartum diet improved organic matter (OM), ether extract (EE), crude protein (CP), and starch intake. Moreover, HS diets resulted in higher apparent digestibility of OM and CP but lower starch digestibility than LS diets. Feeding HS diets increased fecal starch output compared with LS diets. There was starch levels and FA supplements interaction for serum albumin and total antioxidant capacity (TAC), with higher concentrations in HSSA and LSPA compared to HSPA and LSSA. Significant correlations between performance and blood metabolites were observed in weeks 3 and 4. In week 3, a negative correlation was observed between serum TAC with milk protein (r =  - 0.51) and lactose percentage (r =  - 0.49) in the HS diet. However, non-esterified FA was correlated with the fat to protein ratio in the LS diet (r = 0.54). Moreover, in week 4, serum TAC was negatively related to the body condition score of the cows fed LS diet (r = 0.50), while there was no relationship for cows fed HS diets. In conclusion, feeding HS diets to postpartum cows increased nutrient intake and the digestibility of OM and CP compared with LS diets. The addition of SA to the HS diet may be more beneficial than PA in improving the oxidative status of dairy cows in the postpartum period.

Characterisation of landrace 'criollo' maize silage from the highlands of Mexico in terms of starch content

Maize silage is appreciated for dairy cows due to its high energy content. Mexico is a centre of origin for maize and small-scale dairy farmers use landrace 'criollo' maize silages to feed their herds. However, the characteristics of landrace 'criollo' maize silages in terms of starch content, which defines their nutritional value in terms of energy, are not known. The objective was to characterise criollo maize silages in terms of starch content. Seventy-seven silage samples from 2011 to 2015 were analysed for contents of dry matter (DM), organic matter (OM), neutral detergent fibre (NDF), acid detergent fibre (ADF), crude protein (CP), in vitro dry matter digestibility (IVDMD), and starch content. A factor analysis using principal component analysis as an extraction method was undertaken, and a hierarchical cluster analysis performed. Five factors affected the starch content of silages and five maize silage clusters identified. There was a positive association between IVDMD and metabolisable energy and between crude protein and acid detergent fibre; moreover, a positive relation was found between dry matter and maize starch contents. Significant differences were found (P < 0.001) for the contents of IVDMD, ME, ashes, OM, DM, and starch. The DM content of group 1 silage did not show any significant differences from other groups, except with group 2 silage, which had the lowest contents of DM and starch. Therefore, group 1 and 5 silage had the highest DM and starch contents, while group 3 silage had the highest IVDMD values and ME contents; finally, group 4 had the highest ash contents. Starch content in criollo maize silages was higher that reports for other maize races and is influenced by climate conditions and dry matter content.

Meta-analysis of the effects of the dietary application of exogenous alpha-amylase preparations on performance, nutrient digestibility, and rumen fermentation of lactating dairy cows

Several studies have evaluated the effects of the dietary application of exogenous alpha-amylase preparations (AMA) as a strategy to increase total tract starch digestibility (TTSD) and milk yield (MY) in dairy cows, but the results have been inconsistent. Thus, the objective of this study was to evaluate the effects of the dietary application of AMA on the performance, digestibility, and rumen fermentation of lactating dairy cows using a meta-analytic method. A total of 18 peer-reviewed manuscripts (N = 32 treatment comparisons) from 2003 to 2019 were systematically identified following the PRISMA method. The weighted raw mean differences between dietary AMA and control treatments were compared with a robust variance estimation. Likewise, diet characteristics like crude protein (CP) content, NDF content, starch content, days in milk (DIM), experimental design (Latin square and continuous), and AMA dose (0 to 732 Kilo Novo units (KNU)/ kg TMR) were used as covariates in a meta-regression, subgrouping, and dose-response analysis. Compared to the control, dietary AMA increased (P < 0.05) DM digestibility (69.32 vs. 68.30%), TTSD (94.62 vs. 94.10%), milk protein concentration and yield (3.11 vs. 3.08 %; 1.14 vs. 1.10 kg/d) and tended to increase (P = 0.09) fat-corrected milk (35.96 vs. 35.10 kg/d) but no effects were observed on DM intake (22.99 vs. 22.90 kg/d) and feed efficiency (1.50 vs. 1.48). Dietary AMA tended (P = 0.10) to reduce rumen pH (6.27 vs 6.30). Both, the enzyme dose, and DIM strongly influenced (P < 0.05) the effects of AMA on digestibility and performance. The dose-response analysis revealed that feeding 600 KNU/kg to high-producing early lactation (< 70 DIM) dairy cows increased FCM and milk protein. Accounting for the type of experimental design was associated with a lower between-studies-variance among comparisons. Overall, this meta-analysis supports the hypothesis that dietary AMA supplementation is associated with a better lactational performance in dairy cows. However, these effects are only suitable for high-producing early lactation dairy cows.

Bovine Animal Model for Studying the Maternal Microbiome, in utero Microbial Colonization and Their Role in Offspring Development and Fetal Programming

Recent developments call for further research on the timing and mechanisms involved in the initial colonization of the fetal/infant gut by the maternal microbiome and its role in Developmental Origins of Health and Disease (DOHaD). Although progress has been made using primarily preterm infants, ethical and legal constraints hinder research progress in embryo/fetal-related research and understanding the developmental and mechanistic roles of the maternal microbiome in fetal microbial imprinting and its long-term role in early-life microbiome development. Rodent models have proven very good for studying the role of the maternal microbiome in fetal programming. However, some inherent limitations in these animal models make it challenging to study perinatal microbial colonization from a biomedical standpoint. In this review, we discuss the potential use of bovine animals as a biomedical model to study the maternal microbiome, in utero microbial colonization of the fetal gut, and their impact on offspring development and DOHaD.

Effects of feeding corn containing an alpha-amylase gene on the performance and digestibility of growing cattle

Two growth performance studies and two digestibility trials were conducted to evaluate the effects of feeding Enogen® Feed Corn silage and corn grain to growing cattle. In Exp. 1, there were a total of 4 diets offered for ad libitum intake. The 4 diets consisted of 2 varieties of corn (Enogen Feed Corn [EFC] vs. yellow #2 corn [CON]) with two different methods of corn processing (dry-rolled [DR] vs. whole-shelled [WS]) and were formulated to provide 1.13 Mcal NEg/kg dry matter (DM); corn grain was 28.6% of diet DM. Average daily gain (ADG) and ending body weight tended to be greater for calves fed EFC than for those fed CON (P &lt; 0.10). Gain:feed (G:F) was better for calves fed EFC (P &lt; 0.01), improving by 5.5% over calves fed CON. In Exp. 2, a digestibility trial was conducted using 7 cannulated Holstein steers fed the same diets from Exp. 1. Ruminal pH was not affected by corn variety (P &gt; 0.82). Liquid passage rate was greater for CON-fed calves and associated with lower digestibility. Total tract DM and organic matter (OM) digestibilities were greater for EFC-fed calves (P &lt; 0.04). In Exp. 3, there were 4 diets offered for ad libitum intake. Dietary factors were arranged as a 2 × 2 factorial and consisted of two hybrids of corn silage (EFC silage [EFC-S] vs. control silage [CON-S]) and two varieties of corn grain (EFC grain [EFC-G] vs. control [CON-G]; both were dry-rolled). Diets were formulated to provide 1.11 Mcal NEg/kg DM; corn grain was 38.5% of diet DM, and corn silage was 40% of diet DM. ADG was 6.0% greater (P &lt; 0.01) and G:F was numerically (P &lt; 0.14) 3.3% greater for calves fed EFC-S than for those fed CON-S, but substituting EFC-G for CON-G did not affect ADG or G:F. In Exp. 4, a digestibility trial was conducted using 8 cannulated beef steers fed the same diets as Exp. 3. Liquid passage rate (P &gt; 0.20), ruminal pH (P &gt; 0.23), and ruminal total volatile fatty acid concentrations (P &gt; 0.27) were unaffected by treatment. Total tract digestibilities of DM and OM were numerically greater by 2.5 and 2.2%, respectively, for calves fed the EFC-S compared to those fed CON-S. Feeding a corn hybrid containing alpha-amylase enzyme improved G:F of growing calves. Feeding EFC can benefit the beef industry by allowing less processing of grain without sacrificing performance.

Taxonomy and Functional Diversity in the Fecal Microbiome of Beef Cattle Reared in Brazilian Traditional and Semi-Intensive Production Systems

The importance of beef production for economy of Brazil and the growing demand for animal protein across the globe warrant an improvement in the beef production system. Although most attention has been on modulation of the rumen microbiome to improve ruminant production, the role of the lower gut microbiome in host health and nutrition remains relatively unexplored. This work aimed to investigate the taxonomy and functional variations in the fecal microbiome of Brazilian beef cattle reared in two different production systems using a metagenomic approach. Sixty male beef cattle from six farms representing semi-intensive (I, n = 2) and traditional (T, n = 4) Brazilian beef production systems were enrolled in the study. Shotgun sequencing was used to characterize taxonomic and functional composition and diversity of the microbiome in fecal samples collected from each animal. Fecal samples were analyzed for copper (Cu), lead (Pb), nitrogen (N), phosphorous (P), selenium (Se), and zinc (Zn) and stable isotopes of carbon (¹³C) and nitrogen (¹⁵N). The fecal microbiome was influenced by the beef production systems with greater functional and lower taxonomic diversity in beef cattle feces from I systems compared with that from T systems. The concentration of N, P, and Zn was higher in beef cattle feces from I systems compared with that from T systems and was associated with taxonomic and functional profile of fecal microbiome in I system, suggesting the role of fecal nutrients in shaping system-specific microbiome. Semi-intensive management practices led to a more complex but less connected fecal microbiome in beef cattle. The microbial community in beef cattle feces from I systems was characterized by greater abundance of beneficial bacteria (phylum Firmicutes and butyrate-producing bacteria family Lachnospiraceae and genera Anaerostipes, Blautia, Butyrivibrio, Eubacterium, Roseburia, and Ruminococcus). In addition, the fecal abundance of microbial genes related to immune system, nutrient metabolism, and energy production was greater in beef cattle raised under I systems compared with that under T systems. Findings of the current study suggest that semi-intensive management practices could facilitate the development of a healthier and more efficient fecal microbiome in beef cattle by driving an increase in the abundance of beneficial bacteria and functional genes.

Estimation of between-Cow Variability in Nutrient Digestion of Lactating Dairy Cows Fed Corn-Based Diets

Simple Summary

Cow variability present in nutrient digestibility studies differs for different diets and nutrients. It is a major factor determining adequate sample size so that studies are not under-powered or over-powered. The objective of the current study was to develop cow variability estimates that can be used to determine the optimal sample size for digestibility trials having randomized block designs using mid-lactation dairy cows when fed corn-based diets having different neutral detergent fiber:starch ratio (0.7, 1.0, and 1.3). Cow variability is greater for digestibility of fiber and dry matter and less for starch. Estimated cow variability as standard deviations for digestibility of dry matter, neutral detergent fiber and starch were 3.8 g/kg, 5.1 g/kg and 3.3 g/kg, respectively. A major implication of this study is that cow variability is greatest for fiber digestibility and the use of a minimum of 12 cows per dietary treatment is adequate to reliably detect treatment effects on the digestibility of fiber, starch and dry matter using lactating dairy cows fed in groups with randomized block design under current experimental conditions.

Abstract

The objective of this study was to estimate cow variability that can be used to determine the optimal sample size for digestibility trials using lactating dairy cows. Experimental design was randomized complete block design having three blocks and three dietary treatments. Three similarly managed nearby intensive farms were considered as blocks, and three diets were formulated to have 0.7, 1.0, and 1.3 neutral detergent fiber (NDF): starch ratio. In each farm, 18 cows were assigned for each dietary treatment and five sample sizes per each treatment group were simulated by simple random sampling of data from 18, 15, 12, 9 and 6 cows respectively. Intake was not affected by diet or sample size (p > 0.05). Estimated cow variability (as standard deviation) for digestibility of dry matter, NDF and starch were 3.8 g/kg, 5.1 g/kg and 3.3 g/kg, respectively. A major implication of this study is that cow variability is greatest for NDF digestibility and the use of a minimum of 12 cows per dietary treatment is adequate to reliably detect treatment effects on the digestibility of NDF, starch and dry matter using cows fed in groups with randomized block design under these experimental conditions.

Invited Review: Nutritional regulation of gut function in dairy calves: From colostrum to weaning

Purpose

Published literature regarding calf nutrition was reviewed to create an information base for the implementation of proper nutritional management to maximize health and productivity.

Sources

The main source of data and information for this review was peer-reviewed literature.

Synthesis

Feeding a sufficient volume of colostrum during the first hours of life is crucial to calf health and survival; however, less is known about transition milk feeding and the potential benefits of the myriad of bioactive compounds it contains. After feeding colostrum and transition milk, calves are susceptible to diarrhea when moved onto high amounts of milk, and antibiotic use is often necessary to decrease disease. Feeding an elevated plane of milk nutrition results in increased ADG and, in some studies, increased future milk production. Thus, this nutritional strategy is recommended; however, weaning calves from high volumes of milk represents massive changes in the structure and microbiology of the gastrointestinal tract.

Conclusions and Applications

Colostrum and transition milk contain an abundance of bioactive molecules that can positively affect gut development and microbiota. There is significant potential for the use of novel feeding strategies and microbial-based products as alternatives to antibiotics. Calves fed an elevated plane of nutrition in the first month of life have greater productivity and growth. However, weaning should take place later in life. Moreover, applying a proper step-down feeding protocol is recommended, as it allows calves to intake and digest sufficient solid feed for growth and minimize distress at weaning.

Lactation performance of dairy cows fed rehydrated and ensiled corn grain differing in particle size and proportion in the diet

Rehydrated and ensiled mature ground corn has high ruminal starch digestibility, but particle size (PS) and dietary starch proportion (ST) can affect starch digestion and lactating cow performance. We evaluated the effect of rehydrated and ensiled corn (REC), PS, and ST on intake, lactation performance, nutrient digestibility, ruminal fermentation profile, and chewing behavior of dairy cows. Kernels from an 84% vitreousness hybrid were finely (FN) or coarsely (CS) ground, yielding geometric mean particle sizes of 1,591 and 2,185 µm, respectively. Ground kernels were rehydrated [60% dry matter (DM)] and ensiled in 200-L buckets for ≥205 d. The grinding rate (t/h) was 3.9 for FN and 11.7 for CS. The PS did not affect DM loss (11.3% of ensiled) or silage pH (3.8). Samples of each bucket (n = 15/PS) before and after silage fermentation were incubated in situ for 0, 3, 6, 18, and 48 h in 4 rumen-cannulated lactating cows. Ensiling increased the effective ruminal in situ DM degradation (63.7 vs. 34.1%), regardless of PS. Sixteen Holstein cows (152 ± 96 d in milk) in 4 × 4 Latin squares (21-d periods) were individually fed a 2 × 2 factorial combination of low (LO) or high (HI) starch diets with FN or CS. Cows were fed the same REC incubated in situ. Varied concentration of starch in the diet (29.2 vs. 23.5% of DM) was achieved by partial replacement of REC (22.0 vs. 14.2% of DM) with citrus pulp (0 vs. 8.2% of DM). Milk, protein, fat, and lactose yields did not differ. Milk fat percentage was reduced and protein percentage was increased by HI. Treatment FN increased feed efficiency (energy-corrected milk/digestible organic matter intake) when fed with HI. Total-tract starch digestibility tended to be reduced by CS (96.4 vs. 97.2% of starch intake). Serum β-hydroxybutyrate was increased by LO. High-starch diet reduced the molar proportions of acetate and butyrate in ruminal fluid and increased propionate and isoacids. Particle size did not affect ruminal fermentation profile. Coarse grinding reduced plasma d-lactate concentration with HI. Diet HI reduced the proportion of daily intake from 1900 to 0700 h and induced preferential intake of feed particles <8 mm and greater refusal of particles >19 mm in the morning. Fine REC reduced rumination time per day and increased eating time per DM intake. Milk and plasma urea-N did not differ. Ensiling of mature flint corn for >200 d largely eliminated the effect of the PS of REC on the studied outcomes. The proportion of REC in the diet affected ruminal fermentation profile and milk solids concentration, but did not affect short-term performance and digestibility. Coarse grinding of REC may allow increasing the grinding rate and thus save labor and energy during ensiling.

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.

Effects of maternal protein supplementation and inclusion of rumen-protected fat in the finishing diet on nutrient digestibility and expression of intestinal genes in Nellore steers

The study aimed to evaluate nutrient digestibility and intestine gene expression in the progeny from cows supplemented during gestation and fed diets with or without rumen-protected fat (RPF) in the feedlot. Forty-eight Nellore steers, averaging 340 kg, were housed in individual pens and allotted in a completely randomized design using a 2 × 2 factorial arrangement (dams nutrition × RPF). Cows' supplementation started after 124 ± 21 days of gestation. The feedlot lasted 135 days and diets had the inclusion of zero or 6% of RPF. Digestibility was evaluated by total feces collection. Steers were slaughtered using the concussion technique and samples of pancreas and small intestine were collected immediately after the slaughter to analyze α-amylase activity, and the expression of SLC5A1, CD36, and CCK and villi morphometry. Feeding RPF increased nutrients digestibility (p < 0.01). There was no effect of maternal nutrition on digestibility and α-amylase activity in steers (p > 0.05). Duodenal expression of SLC5A1, CD36, and CCK increased in the progeny from restricted cows. In conclusion, protein restriction during mid to late gestation of dams has long-term effects on small-intestine length and on expression of membrane transporters genes in the duodenum of the progeny. However, maternal nutrition does not affect digestibility in the feedlot.

Characterization of the variation in the daily excretion of faecal constituents and digestibility predictions in beef cattle fed feedlot diets using near-infrared spectroscopy

Six heifers were individually housed and assigned to once (FF1) or twice (FF2) daily feeding regimes over backgrounding and finishing periods. Following adaptation, total faecal collections were conducted at 4-h intervals and at 24-h intervals over 4 d, and near-infrared spectroscopy (NIRS) was used to predict faecal organic matter (OM), starch, nitrogen (N), neutral detergent fibre (NDF), acid detergent fibre (ADF), and acid detergent lignin (ADL). At each interval, NIRS calibrations were used to estimate faecal constituents and ADL to calculate apparent (aTTD) and estimated (eTTD) total tract digestibility. Faecal dry matter (DM) (%), NDF, and ADF varied among 4-h interval samples in the backgrounding period and faecal DM, starch, NDF, ADF, and ADL in the finishing period. Faecal starch was able to predict aTTD during both feeding periods (backgrounding: R2 = 0.96, P < 0.01; finishing: R2 = 0.98, P < 0.01). The NIRS calibrations for predicting aTTD using the 4-h interval samples or the 4-d–24-h composite were least accurate for NDF and ADF. Most 4-h interval samples could be used to predict eTTD of nutrients, and aside from starch in the finishing period, there were no differences in eTTD using faecal samples collected over 4-h intervals versus those collected over 4 d. Spot faecal samples collected at any time point from multiple cattle have the potential to predict digestibility. Timing of sampling after feeding must be standardized to predict starch digestibility during the finishing period, with samples between 0–4 h and 8–16 h generating estimates of both starch concentration and digestibility that were closest to that derived from 4-d–24-h composite samples.

Weaning age affects growth, feed intake, gastrointestinal development, and behavior in Holstein calves fed an elevated plane of nutrition during the preweaning stage

Recent research has revealed potential advantages of feeding an elevated plane of nutrition to calves during the preweaning period. However, calves fed more nutrients preweaning may be more susceptible to depressed growth and weaning stress during the transition from liquid to solid feed. The objective of this study was to investigate the relationship between the age of weaning and feed intake, and its influence on growth, gastrointestinal development, and behavioral indicators in dairy calves fed an elevated plane of nutrition during the preweaning period. To meet this objective, 20 female Holstein calves were randomly assigned at birth to be weaned at 6 or 8 wk. Milk replacer (mixed at 150 g/L) was offered at 1.2 kg/calf per day in 2 meals until a 1-wk step-down, when meals were reduced by 50% 1 wk before weaning. Daily starter, chopped oat straw, water intake, and weekly body weights were measured until d 70 of life. To assess digestive tract development, rumen fluid, fecal, and blood samples were taken before and after weaning (d 35, 49, and 63) and analyzed for ruminal short-chain fatty acids, blood β-hydroxybutyrate, and fecal starch, respectively. Behavioral indicators of weaning stress, including vocalizing and non-nutritive oral behavior, were measured by visual observation for 1 h, 3 times per week, before the second feeding of the day during the period from 2 wk before weaning to 2 wk after weaning. The calves weaned at 8 wk compared with 6 wk had higher average daily gain for the week preweaning (0.79±0.09 vs. 0.34±0.10 kg/d) and postweaning (1.05±0.09 vs. 0.35±0.11 kg/d), and were heavier at d 70 (99.9±1.81 vs. 91.0±2.26 kg). From 5 to 8 wk of age, starter and water intakes were lower in calves weaned at 8 wk of age. However, overall starter intake did not differ during the last week of the experiment. Furthermore, calves weaned at 8 wk compared with 6 wk had higher starter intake for 1 wk preweaning (1.36±0.13 vs. 0.40±0.08 kg/d) and postweaning (2.51±0.20 vs. 1.16±0.15 kg/d). In both treatments, weaning increased ruminal short-chain fatty acids, blood β-hydroxybutyrate, and fecal starch, yet the differences between the week before and after weaning were greater for calves weaned at 6 wk compared with those weaned at 8 wk. Treatment × week relative to weaning interactions indicated that several behaviors varied between early- and later-weaned calves during the week before weaning; calves weaned at 6 wk tended to exhibit 75% more non-nutritive oral behavior and spent 55% less time ruminating, and 36% less time lying compared with calves weaned at 8 wk. Under the conditions of this study, the results suggest that calves fed an elevated plane of nutrition preweaning have higher starter intakes and average daily gain during the weaning period when weaning is extended from 6 to 8 wk of age.