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Precision livestock farming technologies are used to monitor animal health and welfare parameters continuously and in real time in order to optimize nutrition and productivity and to detect health issues at an early stage. The possibility of predicting blood metabolites from milk samples obtained during routine milking by means of infrared spectroscopy has become increasingly attractive. We developed, for the first time, prediction equations for a set of blood metabolites using diverse machine learning methods and milk near-infrared spectra collected by the AfiLab instrument. Our dataset was obtained from 385 Holstein Friesian dairy cows. Stacking ensemble and multi-layer feedforward artificial neural network outperformed the other machine learning methods tested, with a reduction in the root mean square error of between 3 and 6% in most blood parameters. We obtained moderate correlations (r) between the observed and predicted phenotypes for γ-glutamyl transferase (r = 0.58), alkaline phosphatase (0.54), haptoglobin (0.66), globulins (0.61), total reactive oxygen metabolites (0.60) and thiol groups (0.57). The AfiLab instrument has strong potential but may not yet be ready to predict the metabolic stress of dairy cows in practice. Further research is needed to find out methods that allow an improvement in accuracy of prediction equations., (© 2022. The Author(s).)

We used 20 mid-lactating Holstein cows, housed in 4 pens according to a Latin square design, to evaluate the effects of dietary protein restriction (crude protein: 12.3 vs. 15.0% dry matter) and conjugated linoleic acid supplementation (CLA: 6.34 g/d of C18:2cis-9,trans-11 and 6.14 g/d of C18:2trans-10,cis-12) on milk composition, coagulation, curd firming and syneresis modeling, and cheese yield and quality (96 small cheeses). Dietary crude protein restriction, suggested as a way to reduce N excretion in farming, caused a reduction in milk protein content (-4%,), milk casein (-3.8%), lactose (-1%), cheese soluble protein (-16.8%), and the cheese maturation index (-15%), and a correlated increase in cheese fat content (+7.5%) and the fat to protein ratio (+18%). A modest reduction (-0.9%) in milk fat recovery in the curd did not affect cheese yield. The addition of CLA to the cows' diet, suggested as a way to improve N use efficiency and the nutritional value of dairy products, caused substantial alterations to the milk composition, cheese-making process, and cheese quality. The CLA reduced the fat (-12.3%), protein (-2%), casein (-2.2%), lactose (-1.0), and total solids (-4%) contents of milk, tended to delay coagulation, and weakened curd firming. The CLA reduced the fresh cheese yield (-7.5%) and cheese solids (-8.2%) because of the lower nutrient content of the milk, but also because of a lower recovery of milk protein in the curd (-0.9%) and lower total solids (-4.5%). It also reduced the fat content in the ripened cheese (-11.8%), as well as the fat to protein ratio (-19.4%) as a result of having increased the protein content (+9.3%). Last, it increased the lightness of the paste of the ripened cheeses (+3.3%), and especially the shear force (+16.3%). Dietary crude protein restriction, and CLA addition in particular, substantially altered the milk composition, cheese-making process, and cheese quality, and therefore needs to be carefully evaluated. Further studies are required to shed light on the causes of these modifications., (Copyright © 2020 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

A shortage in crude protein (CP) and supplementation of conjugated linoleic acids (CLA) in the diets of dairy cows could improve the dairy industry's ecological footprint and the nutritional value of milk, but it is not known what effect such a strategy might have on the aroma profiles of dairy products. The aim of this work was to study the effects of reducing the dietary CP content (from 150 to 123 g/kg of dry matter), with or without a supply of rumen-protected CLA (7.9 g/d C18:2 cis-9,trans-11 and 7.7 g/d C18:2 trans-10,cis-12), on the volatile organic compound (VOC) profile of cheeses ripened for 3 mo. Twenty mid-lactation Holstein-Friesian cows were reared in 4 pens (5 to a pen), and fed 4 different experimental diets over 4 periods of 3 wk each, following a 4 × 4 Latin square design. Twice in each period, 10-L milk samples were taken from each group and used to produce 32 cheeses, which we then analyzed for VOC by solid-phase microextraction and gas chromatography-mass spectrometry. We detected 48 VOC belonging to 10 chemical classes (11 alcohols, 8 ketones, 8 esters, 7 acids, 4 aldehydes, 4 sulfurs, 2 lactones, 2 phenolic, 1 monoterpene, 1 hydrocarbon); these were expressed as concentrations in cheese (quantitative data) or as proportions of total VOC (qualitative data). The results of mixed model analysis showed that the majority of VOC families and individual VOC in ripened cheese were affected by the dietary treatments: CP shortage depressed the concentrations of volatile aldehydes and increased the proportions of some esters and limonene, whereas CLA increased the concentration of total VOC, particularly several acids and esters, and decreased the proportions of ketones and phenolic compounds. The interaction between dietary CP and CLA affected the proportions of alcohols and acids. We performed a factor analysis to extract 5 latent explanatory variables from the individual VOC, which represented 79% of total VOC variance for the quantitative data and 78% for the qualitative data. Addition of CLA decreased the first qualitative factor (the "base aroma" of cheese, explaining 44% of total variance), whereas CP reduction increased the second quantitative factor ("ethyl esters," 15% of total variance) and the third qualitative factor ("butan-," 9% of total variance). In summary, the VOC profile of ripened cheese was heavily influenced by CP content and CLA supplementation in the diets of dairy cows, but the effect on sensorial properties of cheese is also worth considering., (Copyright © 2020 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Using the Piemontese breed as a case study, we characterised beef production systems within the EU classification, and investigated their effects on carcass and meat quality traits. The research involved 1,327 young bulls fattened on 115 farms. The production systems identified by hierarchical cluster analysis were: traditional (restricted feeding and either tie-stalls or loose-housing), modern breeders and fatteners and specialised fatteners (the last two were divided in those using or not using total mixed rations). Despite the large variability in management techniques within production systems, production systems affected (P < 0.05) farm size, animal density, environmental scoring, diet, slaughter age and all carcass traits except weight. Lightness (L*) of Longissimus thoracis was the only meat quality trait affected (P < 0.05), with values greater in the traditional tie-stall system (+0.9 L*). Given the very limited effect of production systems on meat quality traits, factors related to individual animals within farms, such as genetics, should be considered for their improvement., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

As double-muscled Belgian Blue (BB) and Piemontese (PIEM) breeds are heavily selected for different objectives (the former mainly for muscularity, the latter for ease of calving), the aim of this study was to compare sexual dimorphism in 56 crossbred young bulls and heifers obtained from dairy cows mated to bulls of the two beef breeds. Young PIEM- and BB-sired bulls had similar fattening performances and beef traits, although the BB crossbreds were slightly more muscular. Otherwise, the BB-sired heifers exceeded the PIEM-sired heifers in growth rate (1.12 vs. 0.98kg/d), feed efficiency (0.129 vs. 0.121kg/kg DM), increases in muscle scores (1.45 vs. 0.98 SEUROP scores) and carcass yield (0.612 vs. 0.605), but not in fatness, retail cut proportions and meat quality traits. Sexual dimorphism is, therefore, less distinct in BB than in PIEM crossbreds. In conclusion, BB sires are to be preferred for "product quality", and PIEM sires for "process quality", on account of welfare and ethical issues., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Ruminants (and milk production) contribute to global climate change through enteric methane emissions (EME), and any attempt to reduce them is complicated by the fact that they are difficult and expensive to measure directly. In the case of dairy cows, a promising indirect method of estimating EME is to use the milk fatty acid profile as a proxy, as a relationship exists between microbial activity in the rumen and the molecules available for milk synthesis in the mammary gland. In the present study, we analyzed the detailed fatty acid profiles (through gas chromatography) of a large number of milk samples from 1,158 Brown Swiss cows reared on 85 farms with the aim of testing in the field 2 equations for estimating EME taken from a published meta-analysis. The average estimated methane yield (CH 4 emission per kg of dry matter intake, 21.34 ± 1.60 g/kg) and methane intensity (per kg of corrected milk, 14.17 ± 1.78 g/kg), and the derived methane production (CH 4 emissions per day per cow, 357 ± 109 g/d) were similar to those previously published. Using data from model cheese makings from individual cows, we also calculated estimated methane intensity per kilogram of fresh cheese (99.7 ± 16.4 g/kg) and cheese solids (207.5 ± 30.9 g/kg). Dairy system affected all EME estimates. Traditional dairy farms, and modern farms including corn silage in the TMR exhibited greater estimated methane intensities. We found very wide variability in estimated EME traits among different farms within dairy system (0.33 to 0.61 of total variance), suggesting the need to modify the farms' feeding regimens and management practices to mitigate emissions. Among the individual factors, parity order affected all estimated EME traits excepted methane yield, with an increase from first lactation to the following ones. Lactation stage exhibited more favorable estimated EME traits during early lactation, concomitant with the availability of nutrients from body tissue mobilization for mammary synthesis of milk. Our results showed a coherence between the EME traits estimated from the analysis of milk fatty acids and the expectations according to current knowledge. Further research is needed to validate the results obtained in this study in other breeds and populations, to assess the magnitude of the genetic variation and the potential of these phenotypes to be exploited in breeding programs with the aim to mitigate emissions., (Copyright © 2018 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Association analyses between candidate genes and bovine milk fatty acids can improve our understanding of genetic variation in milk fatty acid profiles and reveal potential opportunities to tailor milk fat composition through selection strategies. In this work, we investigated the association of 51 single nucleotide polymorphisms (SNP) selected from 37 candidate genes using a functional and positional approach, with 47 fatty acids, 9 fatty acid groups, and 5 Δ(9)-desaturation indices in milk samples from Brown Swiss cows. Individual milk samples were collected from 1,158 Italian Brown Swiss cows, and gas chromatography was used to obtain detailed milk fatty acid compositions. A GoldenGate assay system (Illumina, San Diego, CA) was used to perform genotype 96 selected SNP located in 54 genes across 22 chromosomes. In total, 51 polymorphic SNP in 37 candidate genes were retained for the association analysis. A Bayesian linear animal model was used to estimate the contribution of each SNP. A total of 129 tests indicated relevant additive effects between a given SNP and a single fatty acid trait; 38 SNP belonging to 30 genes were relevant for a total of 57 fatty acid traits. Most of the studied fatty acid traits (~81%) were relevantly associated with multiple SNP. Relevantly associated SNP were mainly found in genes related to fat metabolism, linked to or contained in previously identified quantitative trait loci for fat yield or content, or associated with genes previously identified in association analyses with milk fatty acid profiles in other cow breeds. The most representative candidate genes were LEP, PRL, STAT5A, CCL3, ACACA, GHR, ADRB2, LPIN1, STAT1, FABP4, and CSN2. In particular, relevant associations with SNP located on bovine chromosome 19 (BTA19) were found. Two candidate genes on BTA19 (CCL3 and ACACA) were relevantly associated with de novo short- and medium-chain fatty acids, likely explaining the high heritability values found for these fatty acids (with the exception of C6:0). Two additional genes on BTA19 (CCL2 and GH1) showed associations with saturated and branched-chain fatty acids. Our findings provide basic information on genes and SNP affecting the milk fatty acid composition of dairy cows. These results may support the possibility of using genetic selection to modify milk fatty acid profiles to promote beneficial health-related effects., (Copyright © 2016 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

The aim of this study was to characterize the profile of 47 fatty acids, including conjugated linoleic acid (CLA), 13 fatty acid groups, and 5 Δ(9)-desaturation indices in milk samples from Brown Swiss cows. The genetic variation was assessed and the statistical relevance of the genetic background for each trait was evaluated using the Bayes factor test. The additive genetic, herd-date, and residual relationships were also estimated among all single fatty acids and groups of fatty acids. Individual milk samples were collected from 1,158 Italian Brown Swiss cows and a detailed analysis of fat percentages and milk fatty acid compositions was performed by gas chromatography. Bayesian animal models were used for (co)variance components estimation. Exploitable genetic variation was observed for most of the de novo synthesized fatty acids and saturated fatty acids, except for C4:0 and C6:0, whereas long-chain fatty acids and unsaturated fatty acids (including CLA) were mainly influenced by herd-date effects. Herd-date effect explained large portions of the total phenotypic variance for C18:2 cis-9,cis-12 (0.668), C18:3 cis-9,cis-12,cis-15 (0.631), and the biohydrogenation and elongation products of these fatty acids. The desaturation ratios showed higher heritability estimates than the individual fatty acids, except for CLA desaturation index (0.098). Among the medium-chain fatty acids, C12:0 had greater heritability than C14:0 (0.243 vs. 0.097, respectively). Both C14:0 and C16:0 showed negative additive genetic correlations with the main monounsaturated and polyunsaturated fatty acids of milk fat, suggesting that their synthesis in the mammary gland may be influenced by the presence of unsaturated fatty acids. No correlation was observed between C4:0 and the other short-chain fatty acids (except for C6:0), confirming the independence of C4:0 from de novo mammary fatty acid synthesis. Among the genetic correlations dealing with potentially beneficial fatty acids, C18:0 was positively correlated with vaccenic and rumenic acids and negatively with linoleic acid. Finally, fatty acids C6:0 through C14:0 showed relevant correlations due to unknown environmental effects, suggesting the potential existence of genetic variances in micro-environmental sensitivity. This study allowed us to acquire new knowledge about the genetic and the environmental relationships among fatty acids. Likewise, the existence of genetic variation for most of de novo synthetized fatty acids and saturated fatty acids was also observed. Overall, these results provide useful information to combine feeding with genetic selection strategies for obtaining a desirable milk fatty acids profile, depending on the origin of fatty acids in milk., (Copyright © 2016 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

The objectives of this study were to characterize the variation in curd firmness model parameters obtained from coagulating bovine milk samples, and to investigate the effects of the dairy system, season, individual farm, and factors related to individual cows (days in milk and parity). Individual milk samples (n = 1,264) were collected during the evening milking of 85 farms representing different environments and farming systems in the northeastern Italian Alps. The dairy herds were classified into 4 farming system categories: traditional system with tied animals (29 herds), modern dairy systems with traditional feeding based on hay and compound feed (30 herds), modern dairy system with total mixed ration (TMR) that included silage as a large proportion of the diet (9 herds), and modern dairy system with silage-free TMR (17 herds). Milk samples were analyzed for milk composition and coagulation properties, and parameters were modeled using curd firmness measures (CFt) collected every 15 s from a lacto-dynamographic analysis of 90 min. When compared with traditional milk coagulation properties (MCP), the curd firming measures showed greater variability and yielded a more accurate description of the milk coagulation process: the model converged for 93.1% of the milk samples, allowing estimation of 4 CFt parameters and 2 derived traits [maximum CF (CF(max)) and time from rennet addition to CF(max) (t(max))] for each sample. The milk samples whose CFt equations did not converge showed longer rennet coagulation times obtained from the model (RCT(eq)) and higher somatic cell score, and came from less-productive cows. Among the sources of variation tested for the CFt parameters, dairy herd system yielded the greatest differences for the contrast between the traditional farm and the 3 modern farms, with the latter showing earlier coagulation and greater instant syneresis rate constant (k(SR)). The use of TMR yielded a greater tmax because of a higher instant curd-firming rate constant (k(CF)). Season of sampling was found to be very important, yielding higher values during winter for all traits except k(CF) and k(SR). All CFt traits were affected by individual cow factors. For parity, milk produced by first-lactation cows showed higher k(CF) and k(SR), but delays in achieving CF(max). With respect to stage of lactation, RCT(eq) and potential asymptotic CF increased during the middle of lactation and stabilized thereafter, whereas the 2 instant rate constants presented the opposite pattern, with the lowest (k(CF)) and highest (k(SR)) values occurring in mid lactation. The new challenge offered by prolonging the test interval and individual modeling of milk technological properties allowed us to study the effects of parameters related to the environment and to individual cows. This novel strategy may be useful for investigating the genetic variability of these new coagulation traits., (Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

This study compared measured gas production (GP) and computed CH4 production values provided by closed or vented bottles connected to gas collection bags. Two forages and 3 concentrates were incubated. Two incubations were conducted, where the 5 feeds were tested in 3 replicates in closed or vented bottles, plus 4 blanks, for a total of 64 bottles. Half of the bottles were not vented, and the others were vented at a fixed pressure (6.8 kPa) and gas was collected into one gas collection bag connected to each bottle. Each bottle (317 mL) was filled with 0.4000 ± 0.0010 g of feed sample and 60 mL of buffered rumen fluid (headspace volume = 257 mL) and incubated at 39.0°C for 24 h. At 24 h, gas samples were collected from the headspace of closed bottles or from headspace and bags of vented bottles and analyzed for CH4 concentration. Volumes of GP at 24 h were corrected for the gas dissolved in the fermentation fluid, according to Henry's law of gas solubility. Methane concentration (mL/100mL of GP) was measured and CH4 production (mL/g of incubated DM) was computed using corrected or uncorrected GP values. Data were analyzed for the effect of venting technique (T), feed (F), interaction between venting technique and feed (T × F), and incubation run as a random factor. Closed bottles provided lower uncorrected GP (-18%) compared with vented bottles, especially for concentrates. Correction for dissolved gas reduced but did not remove differences between techniques, and closed bottles (+25 mL of gas/g of incubated DM) had a greater magnitude of variation than did vented bottles (+1 mL of gas/g of incubated DM). Feeds differed in uncorrected and corrected GP, but the ranking was the same for the 2 techniques. The T × F interaction influenced uncorrected GP values, but this effect disappeared after correction. Closed bottles provided uncorrected CH4 concentrations 23% greater than that of vented bottles. Correction reduced but did not remove this difference. Methane concentration was influenced by feed but not by the T × F interaction. Corrected CH4 production was influenced by feed, but not by venting technique or the T × F interaction. Closed bottles provide good measurements of CH4 production but not of GP. Venting of bottles at low pressure permits a reliable evaluation of total GP and CH4 production., (Copyright © 2014 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

The hypothesis tested in this paper is that double-muscled (DBM) and conventional cattle, considerably differing in body composition, have similar NE requirements when: a) NE(m) is scaled as a function of current (P(i)) and adult (P(m)) protein mass; and b) ME for gain (ME(g)) is estimated from protein (Pr) and lipid (Lr) retention and their partial ME use efficiencies, the k(p) and k(l) values, respectively. First, 2 databases were examined: 1 was developed combining well known literature information from comparative slaughter trials conducted on British beef steers; the other was based on a trial conducted using extremely lean DBM Piemontese bulls. From the first database, NE(m) was calculated to be 1.625 × P(i) ÷ P(m) × P(m)(0.73) (MJ/kg(0.73)). From the second database, the daily ME(g) was determined as 22.8 MJ × Pr ÷ k(p) + 38.74 MJ × Lr ÷ k(l), assuming (from prior reports) that k(p) = 0.20 and k(l) = 0.75. Thereafter, ME(m) was defined as ME intake minus ME(g), and, hence, NE(m) was predicted as 1.625 × P(i) ÷ P(m) × P(m)(0.73) (where 1.625 was the value obtained from the first dataset). The resulting k(m) (NE(m)/ME(m)) averaged 0.67. This k(m) value did not differ from that (0.65; P = 0.12) predicted by Garrett's equation, which uses dietary ME content as the only predictive variable. Second, the procedure was tested for the ability to detect effects on k(m) caused by increasing BW and dietary factors not estimable from the dietary ME content only. Data were gathered from a trial involving 48 DBM Piemontese bulls divided into 4 groups fed 1 of 4 diets differing in CP content (145 or 108 g/kg DM), with or without addition of 80 g/d of rumen-protected CLA (rpCLA). Bulls were examined at 3 consecutive periods of growth, corresponding to 365, 512 and 631 kg of average BW. All energy balance items were influenced by increasing BW, except k(m) (P = 0.61), in agreement with the expectation that NE(m) requirement depends on the degree of maturity (P(i)/P(m)) and the P(m)(0.73) of an animal, whereas k(m) reflects characteristics of the feed provided. The k(m) value was also influenced by the CP × rpCLA interaction (P = 0.013). We conclude that DBM and British beef steers have similar NE requirements when these are scaled as a function of P(i) and P(m), and gain composition, considering Pr, k(p), Lr and k(l). The proposed procedure will be useful to predict the energy requirements and feed use in cattle of different types that vary in BW, provided that body and gain compositions are known or accurately predicted.

The aims of this study were 1) to investigate the potential application of near-infrared spectroscopy (NIRS) to predict intramuscular fat (IMF) and fatty acid (FA) composition of individual meat samples, 2) to estimate heritability of IMF and FA NIRS-based predictions, and 3) to assess the statistical relevance of the genetic background of such predictions by using the Bayes factor (BF) procedure. Young Piemontese bulls (n = 1,298) were raised and fattened on 124 farms, and slaughtered at the same commercial abattoir. Intramuscular fat content and FA composition were analyzed on a random subset of 148 samples of minced and homogenized longissimus thoracis muscle. Near-infrared spectroscopy spectra were collected on all samples (n = 1,298) in reflectance mode between 1,100 and 2,498 nm (every 2 nm) using fresh minced meat samples. Calibration models developed from the random subset of 148 samples were used to predict IMF and FA contents of the remaining 1,150 samples. Intramuscular fat content and FA predictions were analyzed under a Bayesian univariate animal linear models, and the statistical relevance of heritability estimates was assessed through BF; the model with polygenic additive effects was favored when BF > 1. In general, satisfactory results (R(2) > 0.60) were obtained for 6 out of the 8 major FA (C14:0, C:16:0, C16:1, C18:0, C18:1n-9 cis/trans, and C18:1n-11 trans), 6 out of the 19 minor FA (C10:0, C12:0, C17:0, C17:1, C18:2 cis-9,trans-11, and C20:2), and the total SFA, MUFA, and PUFA. Bayes factors between models with and without a genetic component provided values greater than 1 for IMF, C14:0, C16:0, C18:1n-9 cis/trans, C17:0, C17:1, C20:2, SFA, MUFA, and PUFA. The greatest BF was reached by C20:2 (BF >10), suggesting strong evidence of genetic determinism, whereas IMF, C18:1n-9 cis/trans, C17:0, C17:1, MUFA, and PUFA showed substantial evidence favoring the numerator model (3.16 < BF < 10). Point estimates of heritabilities for FA predicted by NIRS were low to moderate (0.07 to 0.21). Results support that NIRS is a useful technique to satisfactorily predict some FA of meat. The existence of an important genetic determinism affecting FA profile has been confirmed, suggesting that FA composition of meat can be genetically modified.

A trial was carried out on double-muscled Piemontese bulls to evaluate the effects of two rations differing in crude protein density (HP=14.5% DM and LP=10.8% DM) and top dressed or not with 80 g/d of rumen protected CLA (rpCLA) for a long period (336 d) on meat quality traits and CLA content. Forty-eight bulls were fed one of the four experimental diets based on corn silage and cereals and were slaughtered at an average age and body weight (BW) of 562 ± 18 d and 668 ± 56 kg, respectively. After slaughter the 5th rib cut was dissected into Longissimus thoracis (LT), other muscles (OM), inter-muscular fat (IF), cover fat (CF), and bones. Muscles and fatty tissues were analyzed for proximate composition and fatty acid (FA) profiles. Rib was composed by 81.1, 3.7, 1.6 and 13.6% of muscles, IF, FC and bone, respectively; LT and OM contained only 0.8 and 1.4% of lipid, respectively. The treatments did not influence these values, but rpCLA increased, compared to control, both c9,t11-CLA and t10,c12-CLA concentrations in all the tissues (P<0.01); t10,c12-CLA concentration was increased much more in muscles (+20 times) than in fatty tissues (from +0.2 to +0.9 times). This suggests that in the muscle this isomer is preferentially stored and/or less combusted with respect to other fatty acids. Low protein rations did not exert any influence on carcass and meat quality, as on growth performance, but reduced nitrogen excretion, their use for improving the environmental impact (process quality) of this meat production system is recommended., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

The effects of low-protein (LP) diets and rumen-protected CLA on DMI, ADG, carcass traits, and health status of double-muscled Piemontese young bulls were investigated. Forty-eight bull calves (BW = 237 ± 24 kg) were divided in 4 groups and housed in 12 fully slatted pens. Bulls were fed 2 diets differing in CP density [high-protein (HP) diet: CP = 145 g/kg of DM; LP diet: CP = 108 g/kg of DM] and top-dressed with 80 g/d of rumen-protected CLA or 65 g/d of hydrogenated soybean oil. Orts were collected weekly and feed intake was estimated on a pen basis, with 3 replicated pens for each treatment. Each bull was weighed monthly and examined for alterations of the locomotion system by using the locomotion score as an index of lameness and by counting the number of swollen joints. Carcass quality traits were measured at slaughter, after a feeding period of 332 d. Compared with HP, LP reduced ADG only during the first 4 mo of the trial (1.30 vs. 1.53 kg/d, P = 0.003). However, because of compensatory growth, over the whole trial, no significant effects attributable to CP or to additive were found on final BW (668 kg), ADG (1.19 kg/d), DMI (8.50 or 86 g/d per kg of BW(0.75)), dressing percentage (67.3%), carcass conformation (5.2 points), and carcass fat covering (1.87 points). Feed efficiency was affected by a CP × additive interaction (P = 0.030), with CLA improving feed efficiency when added to the LP diets, whereas feed efficiency was reduced with the HP diets. The addition of both LP and CLA reduced the number of bulls presenting swollen joints (P = 0.001), and LP improved the locomotion score (P = 0.021) compared with HP. It was concluded that 10.8 g/kg of CP density in the diet is sufficient for double-muscled Piemontese bulls. The reduction in CP density from 145 to 108 g/kg of DM, in addition to reducing the feeding cost, allows a strong reduction in N consumption without negative consequences on growth performance and carcass traits.

Dry matter degradability (DMD), gas production (GP), functional specific gravity (FSG), volume of gas associated (GA), water-holding capacity (WHC), and sedimentation measurements of orchard-grass (OG) and alfalfa (AA) hays (ground through a 8-mm screen) were studied before and after in vitro incubation with ruminal fluid for 2, 4, 8, 24, 48, and 72 h. The DMD was higher for AA than for OG (P < .001), but GP did not differ. The FSG of unfermented OG and AA was .59 and .73, respectively (P < .01). During fermentation, the FSG of OG increased more than did that of AA (from .93 to 1.39 for OG and from .97 to 1.27 for AA after 2 and 72 h, respectively), and GA decreased more rapidly (from .94 to -.04 mL/g DM and from .74 to .15 mL/g DM, respectively). The DMD was positively correlated with FSG (r = .83; P < .001) and, therefore, negatively with GA (r = -.72; P < .01). The WHC increased similarly in the two forages with fermentation time. Unfermented and fermented samples were incubated in sedimentation columns filled with distilled water for 19, 37, 75, 150, and 300 s. After 300 s of sedimentation time, the unfermented AA and OG samples tended to float (91.1 and 72.7% of DM, respectively). In contrast, fermented samples tended to sediment (90.7 and 90.9% of DM, respectively). There were only small effects of forage species and fermentation time on sedimentation tendency. Correlations between sedimentation measurements and DMD and FSG were not significant, with the only exception of DM recovered in the lower section of sedimentation columns after 75 s, which was particularly correlated with DMD (P < .01) and FSG (P < .05). The results suggest that degradation rate of fibrous particles is related to changes in FSG and GA and, therefore, could influence ruminal transit. However, FSG was unable to predict accurately the sedimentation behavior of samples.

Four primiparous Holstein cows were gradually introduced, according to a Latin square design, to four diets obtained from the factorial combination of two forage to concentrate ratios (70:30 and 50:50) and two concentrations of monensin sodium (0 and 300 mg/d per cow). Addition of monensin tended to depress feed intake and milk fat content without affecting milk production and without interactions with forage to concentrate ratios. Ruminal propionate percentage was increased more by the addition of monensin to the low forage diet than by the addition of monensin to the high forage diet. Serum urea and concentrations of nonesterified fatty acids tended to decrease when monensin was added to the high forage diet but did not change when monensin was added to the low forage diet. The results suggested that monensin had moderate positive effects on efficiency of milk production and might have an antiketogenic effect with high forage diets.