Effects of physically effective fiber on digestive processes and milk fat content in early lactating dairy cows fed total mixed rations

Effects of the level and source of dietary physically effective fiber on feed intake, nutrient utilization, heat energy, ruminal fermentation, and milk production by Alpine goats

Thirty-two primiparous and 31 multiparous Alpine goats were used to determine influences of diets varying in level and source of forage on performance in early to mid-lactation for 16 wk. Diets consisted of 40%, 50%, 60%, and 70% forage (designated as 40F, 50F, 60F, and 70F, respectively) with 60F and 70F containing coarsely ground grass hay (primarily orchardgrass) and 40F and 50F containing cottonseed hulls, alfalfa pellets, and coarsely ground wheat hay. Diets contained 15.9% to 16.3% crude protein and 37.8%, 42.1%, 53.5%, and 55.4% neutral detergent fiber (NDF) with 10.0%, 15.8%, 50.1%, and 55.5% particle retention on a 19-mm sieve, and 26.1%, 29.6%, 38.3%, and 40.0% physically effective NDF (peNDF) for 40F, 50F, 60F, and 70F, respectively. Dry matter intake (2.71, 2.75, 1.96, and 1.95 kg/d) and milk yield (2.82, 2.71, 2.23, and 2.10 kg/d for 40F, 50F, 60F, and 70F, respectively) were lower (P < 0.05) for the two diets highest in forage. Digestion of organic matter was similar among diets (P > 0.05), but digestibility of NDF was greater (P < 0.05) for 60F and 70F (57.5%, 58.4%, 68.9%, and 72.2% for 40F, 50F, 60F, and 70F, respectively). Diet affected (P < 0.05) milk fat (3.16%, 3.37%, 2.93%, and 2.97%) and protein concentrations (2.62%, 2.69%, 2.58%, and 2.52% for 40F, 50F, 60F, and 70F, respectively). Milk energy yield was greater (P < 0.05) for the two diets lowest in forage (7.51, 7.45, 5.68, and 5.34 MJ/d), although yield relative to dry matter intake was not affected (P > 0.05) by diet and was lower (P < 0.05) for primiparous vs. multiparous goats (2.71 and 3.09 MJ/kg). Ruminal pH and acetate proportion were greater for 60F and 70F than for the other diets and the proportion of butyrate was lower for the two diets highest in fiber. The mean lengths of time spent ruminating, eating, standing, and lying were not affected (P > 0.05) by diet or parity, but many interactions involving diet, period, hour, and parity were significant (P < 0.05). In conclusion, lactational performance of Alpine goats in early to mid-lactation will be constrained with diets high in forage of moderate quality, peNDF content, and large particle size, which appeared related to limited feed intake.

Comparative Analysis of Rumen Microbiota Composition in Dairy Cows with Simple Indigestion and Healthy Cows

Simple indigestion in cows leads to substantial economic losses in the dairy industry. Despite ongoing efforts, an effective treatment for this issue remains elusive. Previous studies have emphasized the vital role of rumen microbes in maintaining ruminant health. To deepen our comprehension of the intricate interplay between rumen microbiota and simple indigestion, we undertook a study involving the analysis of rumen fluid from eight cows with simple indigestion and ten healthy cows. Additionally, we collected data pertaining to milk production, rumination behavior, and rumen characteristics. The results showed that cows with simple indigestion displayed significantly lower milk yield, reduced rumination duration, and weakened rumen contraction when contrasted with the healthy cows (p < 0.05). However, no significant difference in microbiota α-diversity emerged (p > 0.05). Principal coordinate analysis (PCoA) illuminated substantial variations in rumen microbial structure among the two groups (p < 0.05). Further analysis spotlighted distinctive bacteria in the rumen of the cows with indigestion, including Allisonella, Synergistes, Megasphaera, Clostridium_XIVb, Campylobacter, and Acidaminococcus. In contrast, Coraliomargarita, Syntrophococcus, and Coprococcus are the dominant bacterial genera in the rumen of healthy dairy cows. Importantly, these key bacterial genera also dominated the overarching microbial interaction network. The observation suggests that changes in the abundance of these dominant bacterial genera potentially underlie the principal etiology of cows with simple indigestion. The present findings can provide insights into simple indigestion prevention and treatment in dairy cows.

Impact of sensor data pre-processing strategies and selection of machine learning algorithm on the prediction of metritis events in dairy cattle

With all the sensor data currently generated at high frequency in dairy farms, there is potential for earlier diagnosis of postpartum diseases compared with traditional monitoring methodologies. Our objectives were 1) to compare the impact of sensor data pre-processing on classifier performance by using multiple time windows before a given metritis event, while considering other cow-level factors and farm-scheduled activities; 2) to compare the performance of random forest (RF), k-nearest neighbors (k-NN), and support vector machine (SVM) classifiers at different decision thresholds using different number of past observations (time-lags) for the detection of behavioral patterns associated with changes in metritis scores; and 3) to compare classifier performance between each one of the five behaviors registered every hour by an ear-tag 3-axis accelerometer (CowManager, Agis Autimatisering, Harmelen, Netherlands). A total of 239 metritis events were created by comparing metritis scores between two consecutive clinical evaluations from cows that were retrospectively selected from a dataset containing sensor data and health information during the first 21 days postpartum from June 2014 to May 2017. Hourly sensor data classified by the accelerometer as either ruminating, eating, not active (including both standing or lying), and two different levels of activity (active and high activity) behaviors corresponding to the 3 days before each metritis event were aggregated every 24-, 12-, 6-, and 3-hour time windows. Multiple time-lags were also used to determine the optimal number of past observations needed for optimal classification. Similarly, different decision thresholds were compared in terms of model performance. Depending on the classifier, algorithm hyperparameters were optimized using grid search (RF, k-NN, SVM) and random search (RF). All behaviors changed throughout the study period and showed distinct daily patterns. From the three algorithms, RF had the highest F₁ score followed by k-NN and SVM. Furthermore, sensor data aggregated every 6- or 12-h time windows had the best model performance at multiple time-lags. We concluded that the data from the first 3 days post-partum should be discarded when studying metritis, and either one of the five behaviors measured with CowManager could be used when predicting metritis when sensor data were aggregated every 6- or 12-hour time windows, and using time-lags corresponding to 2-3 days before a given event, depending on the time window used. This study shows how to maximize sensor data in their potential for disease prediction, enhancing the performance of algorithms used in machine learning.

Comparison of milk and grass composition from grazing Irish dairy herds with and without milk fat depression

BACKGROUND

This study investigated the factors relating to pasture chemical and fatty acid (FA) composition that influence the milk fat percentage of spring calving, grazing dairy cows. The relationship between milk fat percentage and FA composition of the milk in these herds was also investigated.

RESULTS

Milk protein percentage, milk casein percentage and cheddar cheese yield were increased in milk from HMF herds. Cows from LMF herds did not have negatively altered milk processability including rennet coagulation time (RCT), pH and ethanol stability. Crude protein, NDF, ADF, ether extract and total FA content of pasture was not different between LMF and HMF herds. Milk fat concentration of conjugated linoleic acid (CLA) t10, c12 was not different between HMF and LMF herds. Pre-grazing herbage mass and pasture content of crude protein, neutral detergent fibre (NDF) and total FA were similar between HMF and LMF herds. Pasture offered to LMF herds had a higher concentration of monounsaturated fatty acids (MUFA). A strong negative relationship (r = -0.40) was evident between milk fat percentage and pasture crude protein content for MMF herds (3.31-3.94% milk fat).

CONCLUSIONS

This research reports improved milk protein percentage, milk casein percentage and cheddar cheese yield from HMF herds compared to LMF herds. Milk processability was not impacted by low milk fat percentage. Pasture NDF and total fatty acid content was similar in HMF herds and LMF herds. Milk fat percentage had a strong negative association (r = -0.40) with pasture crude protein content in MMF herds (MF 3.31-3.94%). Correlation values between pasture chemical and FA composition and milk fat percentage in LMF herds and HMF herds were low, indicating that diet is not the only causative factor for variation in milk fat of grazing dairy cows. Comparison of milk fatty acid composition from herds with and without milk fat depression suggests that there may be other fatty acids apart from CLA t10, c12 that contribute to the inhibition of milk fat synthesis during milk fat depression in grazing herds.

Adjusting for 30-hour undigested neutral detergent fiber in substitution of wheat straw and beet pulp for alfalfa hay and corn silage in the dairy cow diet: Chewing activities, diurnal feed intake, and ruminal fermentation

This experiment investigated the effects of replacing alfalfa hay (AH) and corn silage (CS) with wheat straw (WS) and beet pulp (BP) in diets with similar forage 30-h undigested neutral detergent fiber (uNDF₃₀) on chewing behavior and ruminal fermentation of lactating cows. Twelve multiparous Holstein cows (51 ± 3 kg/d of milk; days in milk = 97 ± 13; mean ± standard error) were housed in individual stalls and used in a replicated 3 × 3 Latin square design with 28-d periods. Experimental diets were (1) 0% forage uNDF₃₀ from WS (WS0, contained 2% BP); (2) 50% forage uNDF₃₀ from WS (WS50, contained 7.6% BP); and (3) 100% forage uNDF₃₀ from WS (WS100, contained 12.4% BP). From 0 to 2 h after the morning feeding, there was a tendency observed for a quadratic effect on dry matter intake (DMI), with cows fed WS50 consuming the greatest amount of DM (9.19 kg). Later DMI (4 to 6 h and 6 to 24 h postfeeding) decreased as dietary proportion of WS and BP increased. Increasing WS and BP decreased eating behavior, but had no detected effect on rumination time (455 min/d), which resulted in a linear reduction in chewing time (the sum of eating and rumination activities). As WS and BP inclusion increased, the number of meals decreased linearly, whereas time between meals, eating rate, and meal size per kilogram of DM increased linearly. Increased dietary inclusion of WS and BP tended to decrease total ruminal VFA and resulted in a linear decrease in propionate but an increase in acetate proportion and ammonia-N concentration in the rumen. Overall, the substitution had no effect on rumination activity, possibly suggesting that a combination of WS and BP could be used in dairy cow rations as substitutes for high-quality forages when WS was added to maintain the uNDF₃₀ level.

Yak rumen microbiome elevates fiber degradation ability and alters rumen fermentation pattern to increase feed efficiency

Rumen microbes play an important role in ruminant energy supply and animal performance. Previous studies showed that yak (Bos grunniens) rumen microbiome and fermentation differ from other ruminants. However, little is understood about the features of the rumen microbiome that make yak adapted to their unique environmental and dietary conditions. This study was to investigate the rumen microbiome and metabolome to understand how yak adapt to the coarse forage and harsh environment in the Qinghai-Tibetan plateau. Nine female Qaidam yellow cattle (Bos taurus), 9 dzomo (hybrids of cattle and yak) and 9 female plateau yak (B. grunniens), about 5 to 6 years old, were used in this study. Rumen fermentation parameters, fibrolytic enzyme activities, and rumen metataxonomic were determined. Then 18 (6 samples per group) were selected for rumen metagenomic and metabolome analysis. Metataxonomic analysis revealed that the rumen microbiota was significantly different among plateau yak, Qaidam yellow cattle, and dzomo (P < 0.05). Metagenomic analysis displayed a larger gene pool encoding a richer repertoire of carbohydrate-active enzymes in the rumen microbiome of plateau yak and dzomo than Qaidam yellow cattle (P < 0.05). Some of the genes encoding glycoside hydrolases that mediate the digestion of cellulose and hemicellulose were significantly enriched in the rumen of plateau yak than Qaidam yellow cattle, but glycoside hydrolase 57 that primarily includes amylases was abundant in Qaidam yellow cattle (P < 0.05). The rumen fermentation profile differed also, Qaidam yellow cattle having a higher molar proportion of acetate but a lower molar proportion of propionate than dzomo and plateau yak (P < 0.05). Based on metabolomic analysis, rumen microbial metabolic pathways and metabolites were different. Differential metabolites are mainly amino acids, carboxylic acids, sugars, and bile acids. Changes in rumen microbial composition could explain the above results. The present study showed that the rumen microbiome of plateau yak helps its host to adapt to the Qinghai-Tibetan plateau. In particular, the plateau yak rumen microbiome has more enzymes genes involved in cellulase and hemicellulase than that of cattle, resulting higher fibrolytic enzyme activities in yak, further providing stronger fiber degradation function.

Partial replacement of corn silage with whole-plant soybean and black oat silages for dairy cows

This study aimed to evaluate the effects of partially replacing corn silage (CS) with whole-plant soybean silage (SS) or black oat silage (OS) on nutrient intake and digestibility, in vitro neutral detergent fiber degradability of silages, feeding behavior, rumen fermentation, and performance of dairy cows. Twenty-four lactating Holstein cows (6 of which were rumen-cannulated) with 32.5 ± 4.92 kg/d milk yield, 150 ± 84.8 days in milk, and 644 ± 79.0 kg of body weight were used in a 3 × 3 Latin square design to evaluate the following treatments: (1) corn silage diet (CSD): using corn silage as the only forage source in the diet [48% dietary dry matter (DM)]; (2) whole-plant soybean silage diet (SSD): SS replacing 16% of corn silage from CSD; and (3) black oat silage diet (OSD): OS replacing 16% of corn silage from CSD. The inclusion of OS and SS decreased intakes of DM, organic matter, and crude protein. Corn silage had the greatest in vivo effective degradability of DM, and SS had the least effective degradability of neutral detergent fiber. The OSD treatment decreased milk and protein yields, whereas SSD increased rumen ammonia nitrogen concentration compared with the other diets. Cows fed OSD exhibited a greater preference for feed with small particles (<4 mm) compared with those fed SSD. Cows fed treatments containing either SS or OS at the expense of CS had increased rumination and chewing activities. Although replacing CS with OS and SS reduced feed intake, SS had no effect on productive performance of dairy cows.

Miúda (Nopalea cochenillifera (L.) Salm-Dyck)-The Best Forage Cactus Genotype for Feeding Lactating Dairy Cows in Semiarid Regions

Simple Summary

The usage of forage cactus is essential for the maintenance of livestock activity in semiarid regions as an alternative to conventional crops. Cactaceae have adaptive characteristics that ensure their development progress under drought conditions. Four genotypes of forage cactus (Gigante, Miúda, IPA Sertânia, and Orelha de Elefante Mexicana) were fed to lactating dairy cows and the diets were then evaluated based on animal performance, milk fatty acid profile, and microbial protein synthesis. Miúda forage cactus led to a higher nutrient intake and milk yield, as well as greater microbial protein synthesis. Higher saturated fatty acids were observed when the Gigante and IPA Sertânia forage cactus genotypes were fed to dairy cows. Orelha de Elefante Mexicana forage cactus caused lower milk yield along with protein yields and content; however, it improved the milk fatty acid profile by promoting a higher ratio of unsaturated to saturated fatty acids and desirable fatty acids. It is concluded that the Miúda forage cactus is the genotype most suitable for the diets of lactating dairy cows.

Abstract

This study aimed to investigate the effects on nutrient intake and digestibility, milk yield (MY) and composition, milk fatty acids profile, and microbial protein synthesis caused by feeding lactating dairy cows four different forage cactus genotypes. Eight Girolando cows (5/8 Holstein × 3/8 Gyr), weighing 490 ± 69.0 kg (means ± standard deviation), and producing 15.5 ± 1.0 kg/d of milk during pretrial were distributed to two contemporaneous 4 × 4 Latin squares. The cows were fed a total mixed ration composed of sorghum silage (385 g/kg of dry matter (DM)), concentrated mix (175 g/kg DM), and forage cactus (440 g/kg DM). The experimental treatments consisted of different cactus genotypes, such as Gigante cactus (GC), Miúda cactus (MC), IPA Sertânia cactus (SC), and Orelha de Elefante Mexicana cactus (OEMC). The feeding of MC provided a higher intake of DM, organic matter (OM), and total digestible nutrients, as well as higher MY, energy-corrected milk, and microbial protein synthesis in comparison with those resulting from the other genotypes tested. The GC promoted lower DM and OM, and the apparent digestibility of neutral detergent fiber. The cows fed with OEMC showed lower MY and milk protein yield and content, and higher unsaturated over saturated fatty acid ratio in milk. Miúda forage cactus increased nutrient intake, digestibility of DM and OM, and microbial synthesis without impairing the milk fatty acid profile.

Models to predict the risk of subacute ruminal acidosis in dairy cows based on dietary and cow factors: A meta-analysis

The present research aimed at developing practical and feasible models to optimize feeding adequacy to maintain desired rumen pH conditions and prevent subacute ruminal acidosis (SARA) in dairy cows. We conducted 2 meta-analyses, one using data from recent published literatures (study 1) to investigate the prediction of SARA based on nutrient components and dietary physical and chemical characteristics, and another using internal data of our 5 different published experiments (study 2) to obtain adjustments based on cow status. The results of study 1 revealed that physically effective neutral detergent fiber inclusive of particles >8 mm (peNDF >8) and dietary starch [% of dry matter (DM)] were sufficient for predicting daily mean ruminal pH {y = 5.960 - (0.00781 × starch) + (0.03743 × peNDF >8) - [0.00061 × (peNDF >8 × peNDF >8)]}. The model for time of pH suppression (<5.8 for ruminal pH or <6.0 for reticular pH, min/d) can be predicted with additionally including DMI (kg/d): 124.7 + (1.7007 × DMI) + (20.9270 × starch) + (0.2959 × peNDF >8) - [0.0437 × (DMI × starch × peNDF >8)]. As a rule of thumb, when taken separately, we propose 15 to 18% peNDF >8 as a safe range for diet formulation to prevent SARA, when starch or NFC levels are within 20 to 25% and 35 to 40% ranges, respectively. At dietary starch content below 20% of DM, grain type was insignificant in affecting ruminal pH. However, increasing dietary starch contents by using corn as the sole grain source could lead to more severe drops of pH compared with using grain mix based on barley and wheat, as underlined by an interaction between starch content and grain type. Data from study 2 emphasized an increased risk of SARA for cows in the first and second lactation with lower mean pH (0.2 units) and double amounts of time at pH <5.8 compared with the cows with ≥3 parities. Given that a lower ruminal pH is expected in these high-risk cows, it is advisable to keep the lower end of recommended starch (20%) and higher peNDF >8 (18%) contents in the diet of these cows. Overall, the present study underlines the possibility of predicting SARA based on dietary factors including peNDF >8 and starch contents, as well as DMI of the cows, which can be practically implemented for optimal diet formulation for dairy cows. With more data available, future studies should attempt to improve the predictions by including additional key dietary and cow factors in the models.

Association between early postpartum rumination time and peak milk yield in dairy cows

Limited information is available on the relationship between rumination time (RT) in the early postpartum period and milk production later in lactation. Therefore, the objectives of this study were to (1) investigate the association of change in RT and average RT during the immediate postpartum period with peak milk yield (PMY) in dairy cows, and (2) determine the best model based on days in milk (DIM) to evaluate this association. Cows from 33 free-flow automatic milking system farms were included in this study, where retrospective milk production and RT data were collected for 12 mo. Cows were categorized by parity number into parity 1 (P1, n = 1,538), parity 2 (P2, n = 1,354), or parity ≥3 (P3+, n = 1,770). For each cow, PMY was identified as the highest daily milk yield up to 180 DIM for P1 and 120 DIM for P2 and P3+ cows. Five change in RT variables and 5 average RT variables were created corresponding to the first 2 to 6 DIM. Change in RT variables were the slope coefficients for change in RT/d related to DIM = 1 extracted from simple linear regressions, and average RT variables were the arithmetic mean RT. Five models analyzing PMY and corresponding variables calculated over the first 2 to 6 DIM had fixed effects of average RT, change in RT, parity, average RT × parity interaction, change in RT × parity interaction, and a random intercept for farm. Peak milk yield occurred at (median) 75, 44, and 46 DIM for P1, P2, and P3+, respectively. Overall PMY was (mean ± standard deviation) 54 ± 11 kg and it increased as parity increased. A positive association was found between change in RT and PMY, and average RT and PMY for P2 and P3+ cows in all 5 models corresponding to the first 2 to 6 DIM, indicating that greater average RT and quicker increase in RT after calving are associated with greater PMY for multiparous cows. Although the model including all 6 DIM had the greatest accuracy, results indicated that rumination data collected over the first 2 DIM may also provide adequate information for the association of average RT and change in RT with PMY in P2 and P3+ cows. For each 100 min/d increase in change in RT over the first 6 DIM, PMY increased by 4.3 (95% confidence interval: 2.2-6.3) and 4.8 (95% confidence interval: 3.2-6.5) kg for P2 and P3+ cows, respectively. Peak milk yield increased by 2.3 (95% CI: 1.7-2.8) and 2.2 (95% confidence interval: 1.7-2.6) kg for each 100 min increase in average RT over the first 6 DIM for P2 and P3+ cows, respectively. No association was observed between rumination behaviors and PMY for P1 cows. Results from this study indicate that the length of time for multiparous cows to achieve a stable RT in the early postpartum period combined with average RT during the same period may be useful in predicting their overall lactation milk production.

Effects of varying proportions of corn grain to barley grain in corn silage-based diet on feed sorting behaviour and productivity of dairy cows

Context Although several studies investigated the dairy cow performance in response to varying ratios of corn to barley grain, little attention has been paid to the forage component of the diet. We hypothesised that a diet based on corn silage with coarse particles might promote chewing and saliva secretion, neutralising acids produced during excess fermentation of high-barley diet and, thus, improve dairy cow productivity. Aims Feed sorting behaviour, nutrient digestibility, rumen fermentation, and milk production were recorded in Holstein cows offered a corn silage-based diet in which corn grain was incrementally substituted with barley grain. Methods Eight multiparous cows, averaging 189 ± 24 days in milk, 577 ± 47 kg bodyweight and 33 ± 5 kg/day milk yield, were distributed according to two 4 × 4 Latin squares. Four total mixed rations were designed, differing in corn to barley ratios as follows: (1) 100:0, (2) 67:33, (3) 33:67 and (4) 0:100. Corn silage and alfalfa hay constituted 31.0% and 9.0% of diet DM respectively. Key results Although no treatment difference existed on sorting of long, medium or fine particles, the extent of sorting for 1.18-mm particles tended to increase linearly as corn to barley ratio decreased. The ruminal pH declined linearly from 5.90 to 5.60 as the barley grain proportion increased from 0 to 100. Acetate to propionate ratio decreased linearly (P &lt; 0.01) as the barley grain proportion increased. No differences were seen in feed consumption and organic matter, crude protein, neutral detergent fibre and fat digestion in total tract. However, non-fibre carbohydrate digestibility tended to increase linearly (P = 0.07) as the ratio of corn to barley grain decreased. Time spent eating, ruminating and chewing remained largely unaffected by treatment. Treatments had no effect on fat-corrected milk production and milk composition, with the exception that actual milk production tended to increase linearly as the corn to barley ratio decreased. Feed efficiency (milk production/DM intake (DMI)) increased linearly from 1.22 to 1.32 as the barley grain proportion increased from 0 to 100. Conclusions Although the differences in feeding behaviour, DMI, and milk production and composition were negligible among experimental diets, cows consuming a corn silage-based diet with incremental substitution of corn grain with barley grain produced more milk per kilogram of DMI. Implications Increased proportion of barley grain in replacement of corn grain in corn silage-based diet might be advised as it increased the efficiency of feed conversion to milk.

Green feed increases antioxidant and antineoplastic activity of buffalo milk: A globally significant livestock

The effect of green feed on health-promoting biomolecules in milk was examined in dairy buffaloes. Buffaloes received a total mixed ration (TMR) (Control, C; n = 40) or TMR + alfalfa green feed (30% of diet) (Treated, T; n = 40). Biomolecules and functional activity were measured in milk obtained twice-monthly. Treated buffaloes had higher milk l-carnitine, acetyl-l-carnitine, propionyl-l-carnitine and δ-valerobetaine (P < 0.01). They also had higher antioxidant activity (P < 0.01). Compared with C buffaloes, milk of T buffaloes improved the viability of endothelial cells exposed to high-glucose (P < 0.01), and reduced intracellular lipid peroxidation, reactive oxygen species (ROS), and cytokine release (P < 0.01). Milk of T buffaloes inhibited with greater potency the viability of human HCT116 and Cal 27 cancer cells (P < 0.001). The findings show that including green feed in the diet of dairy buffaloes enhances health-promoting biomolecules and the antioxidant and antineoplastic properties of milk.

Feeding of bakery by-products in the replacement of grains enhanced milk performance, modulated blood metabolic profile, and lowered the risk of rumen acidosis in dairy cows

Leftover bakery by-products (BP) from bakeries and supermarkets may serve as energy-rich ingredient in ruminant diets. The aim of the present study was to evaluate the effect of the successive substitution of cereal grains by BP on dry matter (DM) intake, milk production, and metabolic health as well as ruminal pH and eating and chewing behavior of dairy cows. Twenty-four lactating Simmental cows (149 ± 22.3 d in milk, lactation number 2.63 ± 1.38, 756 ± 89.6 kg of initial body weight) were fed a total mixed ration containing a 50:50 ratio of forage to concentrate throughout the experiment (35 d). During the first week, all cows received a control diet (without BP) as a baseline (d -7 to 0). In the next 4 wk (d 1 to 28), cows were allocated to 3 groups differing in the BP concentrations of diets [0% BP (CON), 15% BP, and 30% BP on a DM basis]. The DM intake and reticuloruminal pH were continuously measured. Blood and milk samples were taken every week, but only results from the experimental period (d 21 and 28) were used for statistical analyses, whereas results from the baseline were considered covariates. Diet analyses showed that BP inclusion increased the ether extract and sugar contents, whereby starch and neutral detergent fiber decreased. Experimental data showed that feeding BP in the diet increased DM intake. Furthermore, the cows fed 30% BP produced roughly 4 kg/d more milk and energy-corrected milk than the CON cows. The milk urea nitrogen was lower in cows fed the BP. Feeding BP reduced the blood glucose and insulin concentrations, whereas nonesterified fatty acids, β-hydroxybutyrate, and cholesterol increased linearly. Cows fed 15% BP had the shortest period of time in which ruminal pH was below 5.8, in contrast to CON cows (+188 min/d). Taken together, the results suggest that the inclusion of up to 30% BP in the diets of mid-lactation dairy cows shifted the nutrient profile from a glucogenic diet to a lipogenic diet, holding the potential to enhance performance and lower the risk of subacute ruminal acidosis in dairy cows.

Occurrence of visible losses and relationship with corn silage management in dairy farms in the State of Paraná

The aim of this study was to relate the occurrence of visible losses in silage (effluent, spoiled top-layer and during feedout) with silage-making practices, physical and chemical characteristics of silage, and milk composition in Brazilian dairy herds. One-hundred and eight silos from 95 farms, in the State of Parana, were visited for data collection. Data were analyzed by Fisher's Exact and Pearson Correlation Test. Effluent loss was higher in silages with the lowest dry matter content. Using unwalled clamp (drive-over piles) silos, neglecting a protection over the plastic film, and unloading silage with a bucket increased the occurrence of top spoilage. Feedout losses were higher in farms where: the crop was harvested with self-propelled machines; the particle size was larger, and the silage density was lower. There was no relationship between visible losses and silage composition or milk composition, except for milk fat content that, unexpectedly, there was a positive correlation with spoiled silage in the top-layer. Silage losses are reduced by adopting good practices during silage production and feedout.

Increasing the content of physically effective fiber in high-concentrate diets fed to beef heifers affects intake, sorting behavior, time spent ruminating, and rumen pH

AbstractThe importance of fiber particle size in ruminal health is well known, but there are fewer studies to assess the requirements of physically effective NDF (peNDF) in beef cattle than in dairy cattle. The objective of this study was to establish the optimal peNDF proportion in high-concentrate diets fed to beef cattle, to reduce the risk of subacute ruminal acidosis. The experimental design was a replicated Latin Square 4 × 4, with four periods of 21 d. Treatments consisted of four diets with different peNDF proportions: 6.4%, 10.4%, 13.6%, and 15.4%, offered ad libitum as total mixed ration, and containing 15% barley straw and 85% concentrate. Diets, which differed in proportions of straw > 4 mm (considered peNDF) and straw < 4 mm, were manually mixed with concentrate. This concentrate was the same for all diets. A ruminal bolus was orally administered to each heifer for pH measurement. Intake, water consumption, intake by particle size, feed sorting, feeding behavior, behavioral activities, and rumen pH were recorded. Chemical composition and particle sizes of diets offered were assessed in the last week of each period. Data were analyzed using the MIXED procedure of SAS. Orthogonal contrasts determined the linear and quadratic effects of increasing peNDF proportion. T-test procedure determined whether heifers carried out sorting behavior. Particles >4 mm linearly increased (P = 0.001), and particles <4 mm linearly decreased (P = 0.001) as peNDF increased. Water consumption and feeding behavior were unaffected by treatment. As peNDF increased, intakes of DM and NDF linearly decreased (P = 0.001), whereas peNDF intake increased (P = 0.001). Intake of particles > 4 mm linearly increased, whereas intake of particles < 4 mm linearly decreased (P = 0.001) as peNDF increased. Diet 6.4% performed sorting for particles > 4 mm (P < 0.01), and diets 13.6% and 15.4% against particles > 4 mm (P < 0.01). Diet 10.4% tended to sort against particles > 4 mm (P < 0.10). Time spent ruminating linearly increased (P = 0.001) as peNDF increased. Diets did not differ in mean and minimum rumen pH, but time under rumen pH thresholds (5.8, 5.7, 5.6, and 5.5) linearly decreased as peNDF increased (P < 0.05). The results suggested that the diet that best met the requirements of not compromising intake, limiting sorting behavior, and promoting time spent ruminating to reduce the number of hours under rumen pH thresholds, was the 10.4% diet.

Effects of source and concentration of neutral detergent fiber from roughage in beef cattle diets: Comparison of methods to measure the effectiveness of fiber

Methods have been developed to measure the effectiveness of many roughages, but few evaluations have been conducted with tropical feeds. The objectives of this research were to determine the effectiveness of roughage sources based on bioassay and laboratory methods and identify the biological attributes of the diets that correlate with these methods. Six ruminally cannulated Nellore steers (408 ± 12 kg of BW) were randomly assigned to a 6 × 6 Latin square design within six diets: negative control diet (NC) with aNDF as 10% from corn silage (CS); positive control diet (PC) with aNDF as 20% from CS; and four diets containing 10% aNDF from CS and 10% aNDF from each of the following sources: sugarcane (SC), sugarcane bagasse (SCB), soybean hulls (SH), or low oil cottonseed hulls (LOCH). Physical effectiveness factor (pef, related to the physical characteristics of aNDF) and effectiveness factor (ef, related to the ruminal pH) were determined based on a linear model approach that uses a bioassay method in which CS aNDF was assumed to be the standard fiber source. Laboratory methods to estimate pef of roughage sources were based on the proportion of DM of roughage retained on a 1.18-mm sieve pef(>1.18 mm) or retained on the 8.0-mm Penn State Particle Separator screen pef(>8.0 mm). The pef calculated by the bioassay method (total chewing time and ruminal mat resistance) for CS, SCB, and SC were higher values (P < 0.05) compared with SH and LOCH. The pef(rumen mat) of SC and SCB were higher (P < 0.05) than that of CS, SH, and LOCH. The pef(rumen mat) of LOCH was 61% higher than SH. The ef(rumen pH) of SC and LOCH was higher (P < 0.05) than CS and SH. The pef(chewing, min/d), pef(chewing, min/kg of DM), pef(rumen mat), and ef(rumen pH) positively correlated with rumination time, total chewing time, and ruminal mat resistance (values from transit time in seconds). No correlation was observed (P > 0.05) between pef(>8.0 mm) and rumination time, chewing time, and ruminal pH. The pef calculated using the bioassay method as well as pef (>8.0 mm) were negatively correlated with rumen pH (P > 0.05). The values of the effectiveness of fiber sources obtained in this research can be used as a guideline for nutritionists aiming to replace roughage sources from tropical regions in beef cattle finishing diets. Under our conditions, the pef using the bioassay method or laboratory methods were not adequate in predicting ruminal pH.

Effects of feeding rumen-protected amino acids on the performance of feedlot calves

Objective:

This study was conducted to produce and evaluate protected amino acids (AAs) against degradation in the rumen with greater bioavalibility and without the problems associated with polymer coating and the effect this has on calf performance.

Materials and Methods:

In the first step, essential AAs methionine and lysine were reacted with two chemical compounds (Benzaldehyde and Glutaraldehyde) in an attempt to make ligands for producing protected AAs. The physico-chemical characterization, melting point, and mass spectrometric of products were estimated. These products were fed to 36 Holstein dairy calves with 110 ± 0.50 kg of average body weight and an age of 110 ± 10 days. Calves were randomly assigned to six treatments. This study was done with six treatments as a completely randomized one-way design.

Results:

Feed consumption and average daily gain were less for control animals and those fed methionine and lysine glutaraldehyde compared to other treatments. The largest chewing time was observed for methionine and lysine glutaraldehyde, respectively, and the least was control. There was no difference for energy consumption, dry matter intake, or blood metabolites among the six treatments. The greatest total protein content was related to methionine and lysine glutaraldehyde treatment and the least total protein was observed in control treatment.

Conclusion:

It can be concluded that the use of chemical methods to protect AAs can be applied and may have some beneficial effects.

Substitution of corn silage with shredded beet pulp affects sorting behaviour and chewing activity of dairy cows

This study aims to evaluate the effects of substituting increasing concentrations of shredded beet pulp (SBP) for corn silage (CS) on nutrient intake, sorting index, intakes of particle size and nutrients, meal and rumination patterns, and chewing activity of dairy cows. Four multiparous (126 ± 13 day in milk) and 4 primiparous (121 ± 11 day in milk) Holstein cows were used in a 4 × 4 Latin square design experiment with 4 periods of 21 days. Dietary treatments were (DM basis): 16% of dietary DM as CS without SBP (0SBP); 8% CS and 8% SBP (8SBP); 4% CS and 12% SBP (12SBP); and 0% CS and 16% SBP (16SBP). We observed a reduction in the extent of sorting against long particles and medium particles but for fine particles with increasing SBP levels in the diets. The number of eating bouts per day was lesser (8.2%) in cows fed SBP diets compared with 0SBP cows and corresponded with a reduction in eating time per d across treatments. The number of ruminating bouts per day was similar across diets (16.8 bouts/day), but substituting SBP for CS in the diets tended to decrease linearly ruminating bout length (5 min/bout) and tended to increase ruminating bout interval (8 min/day). Eating, ruminating and total chewing time when expressed as minutes per kilogram of forage NDF intake and peNDF > 8 intake increased when SBP was substituted for CS in the diets. Primiparous cows had greater ruminating time (57 m/day) and total chewing time (73 min/day), eating rate (0.01 kg of DM/min) compared with multiparous cows. Also, increasing forage NDF and peNDF_>8 , >8-mm DM intakes are effective means of stimulating ruminating and chewing activities. This study showed that SBP could partially replace CS and not affect DM intake, but chewing activity may decrease slightly.

Estimating optimal observational sampling frequency of behaviors for cattle fed high- and low-forage diets

Video recordings of behavioral activities including eating, ruminating, drinking, standing, and lying were monitored to determine the minimum number of sampling days and sampling frequency required to obtain reliable estimates of these behaviors. Eight continental crossbred heifers, individually housed in a tie-stall barn with total mixed ration provided once per day, were divided by BW into two blocks and assigned to each of the two dietary treatments in a crossover design: high-forage diet (HF, forage:concentrate ratio 70:30) and low-forage diet (LF, forage:concentrate ratio 30:70). The cows were monitored continuously using a digital video recording system for 6 d in each of the two periods and a trained observer manually recorded the behavioral activities by minute. Mean time spent performing each behavior for 6 d with instantaneous samples of 1 min was compared with those obtained using fewer sampling days (1, 2, 3, 4, and 5 d) and less frequent scanning (2, 3, 4, 5, 10, 15, 30, and 60 min) using linear regression analysis, and the minimum number of sampling days or frequency was determined. Diet did not affect the accuracy and precision of predicting behavior from video recordings of the cows. When sampling days and scanning intervals were combined, the minimum recommended sampling frequency for accurately estimating a specific set of behaviors of beef heifers in tie stalls was: eating, 2 d with 4-min intervals; ruminating, 3 d with 4-min intervals; drinking, 2 d with 3-min intervals; and standing and lying, 2 d with 15-min intervals. Increasing sampling frequency beyond these minimums further enhanced the accuracy and precision of predictions. The total time of each behavioral activity was different between cows fed HF and LF diets with eating, ruminating, total chewing, and standing of heifers fed the HF diet greater (P < 0.01), but the lying (P < 0.01) and drinking time (P = 0.028) of heifers fed the LF diet greater. Meal patterns were different (P < 0.05) between the treatments except when meal size (kg) was expressed as DM or OM intake. For rumination patterns, the mean or maximum bout length (min/bout) was greater, but the maximum or minimum length of time heifers took to ruminate after eating was lower for the HF diet. From a practical standpoint, it is recommended to use 3 days of observations scanned at an interval of 4 min to reliably estimate the behavior of cows. If the focus is only lying and standing time, then 2 days with 15 min intervals can be used.

Invited review: Current perspectives on eating and rumination activity in dairy cows

Many early studies laid the foundation for our understanding of the mechanics of chewing, the physiological role of chewing for the cow, and how chewing behavior is affected by dietary characteristics. However, the dairy cow has changed significantly over the past decades, as have the types of diets fed and the production systems used. The plethora of literature published in recent years provides new insights on eating and ruminating activity of dairy cows. Lactating dairy cows spend about 4.5 h/d eating (range: 2.4-8.5 h/d) and 7 h/d ruminating (range: 2.5-10.5 h/d), with a maximum total chewing time of 16 h/d. Chewing time is affected by many factors, most importantly whether access to feed is restricted, intake of neutral detergent fiber from forages, and mean particle size of the diet. Feed restriction and long particles (≥19 mm) have a greater effect on eating time, whereas intake of forage neutral detergent fiber and medium particles (4-19 mm) affects rumination time. It is well entrenched in the literature that promoting chewing increases salivary secretion of dairy cows, which helps reduce the risk of acidosis. However, the net effect of a change in chewing time on rumen buffing is likely rather small; therefore, acidosis prevention strategies need to be broad. Damage to plant tissues during mastication creates sites that provide access to fungi, adhesion of bacteria, and formation of biofilms that progressively degrade carbohydrates. Rumination and eating are the main ways in which feed is reduced in particle size. Contractions of the rumen increase during eating and ruminating activity and help move small particles to the escapable pool and into the omasum. Use of recently developed low-cost sensors that monitor chewing activity of dairy cows in commercial facilities can provide information that is helpful in management decisions, especially when combined with other criteria. Although accuracy and precision can be somewhat variable depending on sensor and conditions of use, relative changes in cow behavior, such as a marked decrease in rumination time of a cow or sustained low rumination time compared with a contemporary group of cows, can be used to help detect estrus, parturition, and some illnesses. This review provides a comprehensive understanding of the dietary, animal, and management factors that affect eating and ruminating behavior in dairy cows and presents an overview of the physiological importance of chewing with emphasis on recent developments and practical implications for feeding and managing the modern housed dairy cow.

Invited review: Practical feeding management recommendations to mitigate the risk of subacute ruminal acidosis in dairy cattle

Rumen health is of vital importance in ensuring healthy and efficient dairy cattle production. Current feeding programs for cattle recommend concentrate-rich diets to meet the high nutritional needs of cows during lactation and enhance cost-efficiency. These diets, however, can impair rumen health. The term "subacute ruminal acidosis" (SARA) is often used as a synonym for poor rumen health. In this review, we first describe the physiological demands of cattle for dietary physically effective fiber. We also provide background information on the importance of enhancing salivary secretions and short-chain fatty acid absorption across the stratified squamous epithelium of the rumen; thus, preventing the disruption of the ruminal acid-base balance, a process that paves the way for acidification of the rumen. On-farm evaluation of dietary fiber adequacy is challenging for both nutritionists and veterinarians; therefore, this review provides practical recommendations on how to evaluate the physical effectiveness of the diet based on differences in particle size distribution, fiber content, and the type of concentrate fed, both when the latter is part of total mixed ration and when it is supplemented in partial mixed rations. Besides considering the absolute amount of physically effective fiber and starch types in the diet, we highlight the role of several feeding management factors that affect rumen health and should be considered to control and mitigate SARA. Most importantly, transitional feeding to ensure gradual adaptation of the ruminal epithelium and microbiota; monitoring and careful management of particle size distribution; controlling feed sorting, meal size, and meal frequency; and paying special attention to primiparous cows are some of the feeding management tools that can help in sustaining rumen health in high-producing dairy herds. Supplementation of feed additives including yeast products, phytogenic compounds, and buffers may help attenuate SARA, especially during stress periods when the risk of a deficiency of physically effective fiber in the diet is high, such as during early lactation. However, the usage of feed additives cannot fully compensate for suboptimal feeding management.

Effects of dietary physically effective neutral detergent fiber content on the feeding behavior, digestibility, and growth of 8- to 10-month-old Holstein replacement heifers

The objective of this study was to evaluate the effects of dietary physically effective neutral detergent fiber (peNDF) content on the feeding behavior, digestion, ruminal fermentation parameters, and growth of 8- to 10-mo-old dairy heifers and to predict the adequacy of dietary fiber in growing dairy heifers. Twenty-four Holstein dairy heifers (245 ± 10.8 d of age, 305.6 ± 8.5 kg initial live weight) were randomly divided into 4 treatments with 6 replicates as a completely randomized design. During the 60-d period with a 10-d adaptation, heifers were offered 1 of 4 diets, which were chemically identical but included different peNDF_8.0 (particle size is >8 mm and <19 mm) content (% DM): 10.8, 13.5, 18.0, or 19.8%, which was achieved by chopping forage into different lengths (fine = 1 cm, short = 3 cm, medium = 5 cm, and long = 7 cm). The concentrate and silage were mixed and fed restrictedly and exclusive of forage (Chinese ryegrass hay) were offered ad libitum. The body weight and frame size of the heifers were measured every 15 d during the experimental period. Samples of the rumen content (2 h after the morning feeding) were taken for pH, ammonia, and volatile fatty acid determination. The dry matter intake and average daily gain of the heifers were not significantly affected by peNDF_8.0 content. The body frame size (including withers height, body length, and heart girth) of the heifers was not increased significantly by enhanced peNDF_8.0 content. Ruminal pH and ammonia concentration were both increased with increasing dietary peNDF_8.0 content. The ruminal total volatile fatty acid concentration and percentage of acetate and butyrate profiles were not significantly affected by dietary peNDF_8.0 content. However, the enhanced peNDF_8.0 content led to a decrease in the propionate percentage. The ratio of acetate to propionate in the 13.5% treatment was highest among the treatments. Increasing the particle size and dietary peNDF_8.0 content resulted in increased eating and chewing time but had no effect on rumination time. Heifer total eating and chewing time and eating and chewing time per kilogram of dry matter intake were increased with increasing dietary peNDF_8.0 content. The apparent digestibility of acid detergent fiber and crude protein was improved with an increasing content of dietary peNDF_8.0. The results suggest that an optimal or advisable dietary particle size and peNDF_8.0 content improves chewing activity, rumen fluid pH, and ruminal fermentation. The data based on feeding behavioral and growth responses of heifers as well as rumen fermentation and digestion by improving total eating and chewing time indicate that 18.0% dietary peNDF_8.0 content is the most suitable for 8- to 10-mo-old Holstein heifers.

Parameters of fermentation and rumen microbiota of Nellore steers fed with different proportions of concentrate in fresh sugarcane containing diets

The objective of this study was to evaluate the effect of a fresh sugarcane-based diet and different roughage-to-concentrate ratios (70:30, 60:40, 40:60 and 20:80) on the rumen microbiota associated with rumen fermentation parameters and the intake and apparent digestibility of nutrients in Nellore steers. Eight rumen-cannulated Nellore steers (331 ± 8 kg BW) were distributed in a double 4 × 4 Latin square design balanced for the control of the residual effect. The ruminal pH decreased (p < 0.01) and the concentrations of N-NH3, isovaleric and valeric acids increased linearly (p < 0.05) with an increase dietary concentrate level. Furthermore, an increased concentrate proportion reduced the population of Fibrobacter succinogenes and Ruminococus flavefaciens (p < 0.01) and increased the population of Selenomonas ruminantium and Megasphaera elsdenii (p < 0.01). The protozoa count revealed a predominance of the genus Entodinium. The synthesis of microbial N [g/d] and the efficiency of microbial synthesis [g of microbial N/kg of organic matter apparently digested in the rumen] increased as the proportion of concentrate was increased (p < 0.05). Therefore, it can be concluded that an increasing proportion of concentrate in sugarcane-containing diets enhances the synthesis of microbial protein and does not alter the fibre digestibility, although the population of fibre fermenting bacteria was reduced.

Ruminal pH predictions for beef cattle: Comparative evaluation of current models

This study evaluated 8 empirical models for their ability to accurately predict mean ruminal pH in beef cattle fed a wide range of diets. Models tested that use physically effective fiber (peNDF) as a dependent variable were Pitt et al. (1996, PIT), Mertens (1997, MER), Fox et al. (2004, FOX), Zebeli et al. (2006, ZB6), and Zebeli et al. (2008, ZB8), and those that use rumen VFA were Tamminga and Van Vuuren (1988, TAM), Lescoat and Sauvant (1995, LES), and Allen (1997, ALL). A data set of 65 published papers (231 treatment means) for beef cattle was assembled that included information on animal characteristics, diet composition, and ruminal fermentation and mean pH. Model evaluations were based on mean square prediction error (MSPE), concordance correlation coefficient (CCC), and regression analysis. The prediction potential of the models varied with low root MSPE (RMSPE) values of 4.94% and 5.37% for PIT and FOX, RMSPE values of 9.66% and 12.55% for ZB6 and MER, and intermediate RMSPE values of 5.66% to 6.26% for the other models. For PIT and FOX, with the lowest RMSPE, approximately 96% of MSPE was due to random error, whereas for ZB6 and MER, with the highest RMSPE, 15.85% and 23.42% of MSPE, respectively, was due to linear bias, and 37.19% and 60.12% of the error, respectively, was due to deviation of the regression slope from unity. The CCC was greatest for PIT (0.67) and FOX (0.62), followed by 0.60 for LES and TAM, 0.52 for ZB8, 0.39 for MER, 0.34 for ALL, and 0.22 for ZB6. Residuals plotted against model-predicted values showed linear bias (P < 0.001) for all models except PIT (P = 0.976) and FOX (P = 0.054) and mean bias (P < 0.001) except for FOX (P = 0.293), LES (P = 0.215), and TAM (P = 0.119). The study showed that the empirical models PIT and FOX, based on peNDF, and LES and TAM, based on VFA, are preferred over the others for prediction of mean ruminal pH in beef cattle fed a wide range of diets. Several animal (BW and intake), diet (forage and OM contents), and ruminal (ammonia and acetate concentrations) factors were (P < 0.001) related to the residuals for each model. We conclude that the accuracy of prediction of mean ruminal pH was relatively low for all extant models. Consideration of factors in addition to peNDF and total VFA, as well as the use of data from studies with continuous measurement of ruminal pH over 24 h or more, would be useful in the development of improved models for predicting ruminal pH in beef cattle.

Effects of by-product feed-based silage on feeding, rumination, and excretion in growing Hanwoo heifers

This study investigated the effects of feeding by-product feed (BF)-based silage on the behavior of growing Hanwoo heifers. Twelve Hanwoo heifers (13.2 months-old, 315 kg body weight; four heifers per pen) were assigned to three diets: a rice straw (RS) diet (concentrate mix and free access to RS), a RS and BF-based silage (RSBFS) diet (concentrate mix and free access to RS and BF-based silage), and a BF-based silage (BFS) diet (concentrate mix and free access to BF-based silage). Behavior was recorded for 5 days using camcorders. Compared to the RS group, the BFS group showed 21.7% higher dry matter intake, shorter feeding, rumination, and chewing times, as well as longer resting time (p < 0.05). Although all groups exhibited similar drinking, urination, and defecation frequencies, the BFS group exhibited higher feeding rates, rumination efficiency, and chewing efficiency than the RS group (p < 0.05). Compared to the BFS group, the RSBFS group showed higher peNDF_8.0 intake (15.2% vs. 25.0% dry matter intake), longer feeding and sitting times, lower defecation frequency (p < 0.05), and similar rumination efficiency. In conclusion, complete replacement of conventional RS with BF-based silage reduced rumination and chewing activity in growing Hanwoo heifers, and BF-based silage feeding with large-particle straw is an effective approach in improving heifer behavior.

Rumination time around calving: an early signal to detect cows at greater risk of disease

The main objective of this experiment was to evaluate the use of rumination time (RT) during the peripartum period as a tool for early disease detection. The study was carried out in an experimental freestall barn and involved 23 Italian Friesian cows (9 primiparous and 14 multiparous). The RT was continuously recorded by using an automatic system (Hr-Tag, SCR Engineers Ltd., Netanya, Israel), and data were summarized in 2-h intervals. Blood samples were collected from 30 d before calving to 42 d in milk (DIM) to assess biochemical indicators related to energy, protein, and mineral metabolism, as well as markers of inflammation and some enzyme activities. The liver functionality index, which includes some negative acute-phase proteins and related parameters (albumin, cholesterol, and bilirubin), was used to evaluate the severity of inflammatory conditions occurring around calving. The cows were retrospectively categorized according to RT observed between 3 and 6 DIM into those with the lowest (L) and highest (H) RT. The average RT before calving (-20 to -2d) was 479 min/d (range 264 to 599), reached a minimum value at calving (30% of RT before calving), and was nearly stable after 15 DIM (on average 452 min/d). Milk yield in early lactation (on average 26.8 kg/d) was positively correlated with RT (r = 0.33). After calving, compared with H cows, the L cows had higher values of haptoglobin (0.61 and 0.34 g/L at 10 DIM in L and H, respectively) for a longer time, had a greater increase in total bilirubin (9.5 and 5.7 μmol/L at 5 DIM in L and H), had greater reductions of albumin (31.2 and 33.5 g/L at 10 DIM in L and H) and paraoxonase (54 and 76 U/ml at 10 DIM in L and H), and had a slower increase of total cholesterol (2.7 and 3.2 mmol/L at 20 DIM in L and H). Furthermore, a lower average value of liver functionality index was observed in L (-6.97) compared with H (-1.91) cows. These results suggest that severe inflammation around parturition is associated with a slower increase of RT after calving. Furthermore, more than 90% of the cows in the L group had clinical diseases in early lactation compared with 42% of the H cows. Overall, our results demonstrate the utility of monitoring RT around calving, and in particular during the first week of lactation, as a way to identify in a timely fashion those cows at a greater risk of developing a disease in early lactation.

Effect of physical effectiveness on digestibility of ration for cows in early lactation

A study was conducted to investigate the effects of a diet particle size on nutrient digestibility in cows in early lactation. Treatments were diets with forage to concentrate ratio 43:57% in diet dry matter, with four different physically effective fibres (peNDF) content based on different cut length of corn silage and alfalfa haylage. The physical effectiveness factors (pef) and peNDF content of TMRs (total mixed ration) were determined using Penn State Particle Separator (PSPS) with two (pef8.0 , peNDF8.0) or three (pef1.18, peNDF1.18) sieves. The reducing of cut length of forages and particle size of diets did not affect on dry matter intake, while decreased peNDF intake by 16.34 and 8.83%, for peNDF8.0 and peNDF1.18 respectively. Apparent total tract digestibility of the nutrients was measured using two indicators: acid insoluble ash (AIA) and acid detergent insoluble lignin (ADL). Decreasing of forages cut length significantly increased apparent total tract digestibility of neutral detergent fibre (NDF) from 48.39% to 53.84% and from 53.9% to 58.66%, of crude protein from 73.96% to 79.24% and from 71.56% to 77.90%, with contemporary decreasing of non-fibre carbohydrate from 90.89% to 84.81% and from 91.99% to 86.80%, with AIA or ADL as indicator respectively. Dietary value of net energy for lactation (NEL) and energy intake was not affected by the peNDF content of the diet.