Influence of the calf presence during milking on dairy performance, milk fatty acid composition, lipolysis and cheese composition in Salers cows during winter and grazing seasons.

The milking of Salers cows requires the presence of the calf. The removal of the calf would simplify the milking routine, but it could also modify the milk yield and the milk and cheese composition. Therefore, the aim of this experiment was to evaluate the effect of calf presence during milking during sampling period (winter or grazing periods), on dairy performance, milk fatty acid (FA) composition, lipolysis and cheese yield and composition. Nine and 8 Salers lactating cows were milked in the presence (CP) or absence (CA) of their calves respectively. During winter, the cows were fed a hay-based diet and then they only grazed a grassland pasture. Calf presence during milking increased milk yield and milk 16:0 concentration and decreased milk fat content and milk total odd- and branched-chain FA (OBCFA) concentrations. Calf presence only increased initial lipolysis in milk collected during the winter season. Milk from CP cows compared to CA cows resulted in a lower cheese yield and ripened cheeses with lower fat content. Milk from the grazing season had lower saturated medium-chain FA and OBCFA concentrations and higher 18:0, cis-9-18:1, trans-11-18:1 and cis-9, trans-11-CLA concentrations than that from the winter season. Initial milk lipolysis was higher in the winter than in the grazing season. These variations could be due to seasonal changes in the basal diet. Furthermore, the effect of calf presence during milking on milk fat composition was lower than that on dairy performance, cheese yield and composition. Removing the calf during the milking of Salers cows seems feasible without a decrease in milked milk, and with a positive effect on cheese yield and fat content, under the condition that we are able to select cows having the capacity to be milked easily without the calf.

The chemical composition of carcasses can be predicted from proxy traits in finishing male beef cattle: A meta-analysis.

Management practices can contribute to improving carcass quality if carcass quality could be simply evaluated under a wide range of conditions. The objective of this study was to derive quantitative relationships between the most accurate (but laborious) measurements of carcass chemical composition and proxy traits easily obtainable at slaughter (yield grade, subcutaneous fat thickness, marbling, ribeye area and hot carcass weight) by meta-analysis. Data from 34 publications using male beef cattle were used to develop and validate the models. The breeds were characterized according to origin, rate of maturity, production purpose and frame size. The results indicated that the changes in carcass fat and protein can be predicted from the yield grade or subcutaneous fat thickness, and hot carcass weight, with prediction errors ranging between 9 and 12%. Including the breed characteristics in the models did not improve the fit. The relationships are applicable to group values of male beef cattle having light and fatty carcasses from early-maturing British breeds.

Modeling of intramuscular lipids in different muscles in bulls, steers, and cows.

Intramuscular fat depot is of major interest for consumers, producers, and the industry. To predict intramuscular (i.m.) lipid deposition in cattle of continental breeds, different models were constructed for different muscles in bulls, steers, and cows. Two independent databases (DB1 and DB2) were developed with homogeneous individual data collected in the same slaughterhouse and total lipids, phospholipids, and triglycerides were analyzed in the same lab with the same procedures. Database DB1 was used with the meta-analysis methodology to fit the predictive models of i.m. lipids, phospholipids, and triglycerides with carcass fatness. Database DB2 was used to evaluate the accuracy of the models predicted. Total lipid and triglyceride contents varied linearly with carcass fatness in bulls, steers, and cows, but phospholipids were more independent of carcass fatness, regardless of the type of cattle studied. In bulls, LM had a lower minimal value (intercept in the model) and greater slope than semitendinosus (ST) and triceps brachii (TB) muscles. In cows, LM showed a greater intercept than ST and TB muscles but a similar slope. In steers, lipid content increased similarly in LM, rectus abdominis (RA) muscle, and ST muscle with carcass fatness. Bulls had a lower intercept than steers but showed a similar trend with carcass fatness. According to the external evaluation using DB2, the models obtained to predict total lipids in LM were more accurate than those obtained in the ST muscle in bulls and cows and in the RA muscle in steers. The models proposed for cows should be used only in the range of carcass fatness used to fit the equations, and further data are needed to fully validate them.

Diet-animal fractionation of nitrogen stable isotopes reflects the efficiency of nitrogen assimilation in ruminants.

The natural abundance of ¹5N in animal proteins (δ¹5Nanimal) is greater than that in the diet consumed by the animals (δ¹5Ndiet), with a discrimination factor (Δ¹5N = δ¹5Nanimal - δ¹5Ndiet) that is known to vary according to nutritional conditions. The objectives of the present study were to test the hypothesis that Δ¹5N variations depend on the efficiency of nitrogen utilisation (ENU) in growing beef cattle, and to identify some of the physiological mechanisms responsible for this N isotopic fractionation in ruminants. Thus, we performed the regression of the Δ¹5N of plasma proteins obtained from thirty-five finishing beef cattle fed standard and non-conventional diets against different feed efficiency indices, including ENU. We also performed the regression of the Δ¹5N of different ruminant N pools (plasma and milk proteins, urine and faeces) against different splanchnic N fluxes obtained from multi-catheterised lactating dairy cows. The Δ¹5N of plasma proteins was negatively correlated with feed efficiency indices in beef cattle, especially ENU (body protein gain/N intake) and efficiency of metabolisable protein (MP) utilisation (body protein gain/MP intake). Although Δ¹5N obtained from different N pools in dairy cows were all negatively correlated with ENU, the highest correlation was found when Δ¹5N was calculated from plasma proteins. Δ¹5N showed no correlation with urea-N recycling or rumen NH3 absorption, but exhibited a strong correlation with liver urea synthesis and splanchnic amino acid metabolism, which points to a dominant role of splanchnic tissues in the present N isotopic fractionation study.

Subcutaneous body lipids affect cyclicity and estrus behavior in primiparous Charolais cows.

Conception rate and the calving interval of beef cows are known to be influenced by body reserves at calving and subsequent postpartum changes. However, few studies have focused on the effect of body reserve dynamics on both postpartum cyclicity and estrus expression. Two successive similar experiments (Year 1: n=14; Year 2: n=16) were carried out on primiparous Charolais cows reared indoors during winter to quantify the effects of adipose cell diameter at calving (ACDca) and their postpartum changes (ACDch) on cyclicity and estrus behavior. Cows were managed to calve with a body condition score (BCS, scale 0-5) of 2.5 (Year 1) and 1.5 (Year 2). After calving cows were assigned to a Low vs. a High energy level diet until turn out to pasture in May. Within years ACDca was similar between Low and High groups whereas calving to turnout changes of body weight (BW), BCS and adipose cell diameter differed (P<0.0001). The interval between calving and resumption of luteal activity was negatively correlated with ACDca (P=0.001). Estrus duration (interval between first and last standing to be mounted (STBM)) was longer in Low than in High groups (P=0.02). Number of STMB was higher in Low than in High cows. Adipose cell diameter at calving and postpartum changes had distinct effects on the components of reproductive performance; emphasizing the need to consider both amounts and changes of body lipids to predict relationships between nutrition and reproduction in cows.

Impact of animal and management factors on collagen characteristics in beef: a meta-analysis approach.

The aim of this paper was to identify pre-slaughter factors that modify total and insoluble collagen contents in bovine muscle to construct a model of collagen dynamics. The meta-analyses were performed with primary data of total (n = 1165) and insoluble (n = 1145) collagen contents from INRA experiments obtained from different muscles in young bulls, cows and steers. According to both the bibliography and meta-analyses, total collagen content and solubility were greatly affected by the muscle (type). Moreover, the pattern of the evolution of collagen characteristics was similar among Longissimus, Semitendinosus and Triceps brachii muscles in young bulls. In cows, collagen contents in the Triceps brachii muscle had delayed dynamics compared with the other muscles. Collagen characteristics differed among breeds because of variation in the maturity of the breed. Similarly, according to the meta-analyses, total and insoluble collagen content evolutions with the degree of maturity (DOM; proportion of adult weight reached at slaughter) were different in dairy and rustic breeds from those of beef breeds, especially in bulls. Although the relationships between collagen content and DOM were quantified in different muscles and sexes, the precision of the fitted equations was not sufficient for prediction. Consequently, relying on the hypotheses raised by the meta-analysis and the literature, an approach to further develop a dynamic mechanistic model of soluble and insoluble collagen content is proposed.

Enteric methane production and greenhouse gases balance of diets differing in concentrate in the fattening phase of a beef production system.

The purposes of this study were 1) to assess the effects of 3 high-concentrate diets on enteric CH(4) production, total tract digestibility, and rumen fermentation of beef cattle, and 2) to evaluate, by life cycle assessment, the potential effects of these feeding systems on the environment. Six bulls (age of 12.4 mo and BW of 417 kg at midexperiment) of the Blond d'Aquitaine breed were assigned to 3 dietary treatments in a replicated 3 × 3 Latin square design. Diets consisted of 1) 49% natural grassland hay, 41% ground corn grain, and 10% soybean meal (hay); 2) 63% corn silage, 21% ground corn grain, and 16% soybean meal (CS); and 3) 70% ground corn grain, 16% soybean meal, and 14% wheat straw (CG). Daily CH(4) emission (g/d), measured using the sulfur hexafluoride tracer technique, was similar for the hay and CS diets and was 56% greater than for the CG diet (P < 0.001). This difference between diets was maintained when CH(4) output was expressed by unit of feed intake (P < 0.001) or digested feed (P < 0.001). Gross energy intake loss as CH(4) averaged 6.9% for the hay and CS diets and 3.2% for the CG diet (P < 0.001). Organic matter intake and GE intake did not differ between diets. Organic matter digestibility was less for the hay diet than for the CS and CG diets (P=0.008). Digestibility of NDF was greatest for the hay diet, intermediate for the CS diet, and least for the CG diet (P=0.02), with ADF digestibility being similar between the hay and CS diets and greater than for the CG diet (P < 0.001). The rumen pH at 5 h postfeeding was less for animals fed the CG diet compared with those fed the other 2 diets (on average, 5.1 vs. 5.9, respectively; P < 0.001). Total CH(4) emission (enteric + manure) was least for the CG diet, whereas N(2)O and CO(2) emissions were greatest for the CG diet. Total greenhouse gas emissions were least for the CG diet when C sequestration by grasslands was not taken into account.

Traceability of grass feeding in beef: terpenes, 2,3-octanedione and skatole accumulation in adipose tissue of young bulls.

The development of analytical methods to verify the production system of meat products requires the identification of biomarkers that can trace the product's origin, and secondly the factors that govern the deposition of these markers in animal tissue need to be defined. In this study, 2,3-octanedione, skatole and terpenes were selected as biomarkers, and their deposition was investigated in bull calves reared under three different strategies. All of the animals were reared indoors until approximately 150 days of age. They were suckled twice a day by their mothers, and both calves and cows had free access to cocksfoot hay. Then the first two groups of animals were kept indoors, suckled by their mothers twice a day and received either cocksfoot hay (HL) or freshly cut-green herbage (GL) and a limited quantity of concentrate. The third group of calves (PH) was kept on pasture with their mothers and offered concentrate ad libitum. The pasture supporting the PH animals was highly diversified, containing several terpene-rich plant species, whereas the herbage for the GL animals contained no species known to be aromatic. Perirenal and subcutaneous adipose tissues were analysed for volatile compounds. The perirenal fat was found to be more responsive to the treatment and a more reliable substrate than the subcutaneous adipose tissue. Higher levels of 2,3-octanedione (P < 0.05) were found in PH and GL than in HL fat (6.56, 6.51 and 5.77 area arbitrary units, respectively, in perirenal fat), confirming the ability of this molecule to trace green herbage feeding. Skatole was detected in the perirenal and subcutaneous fat of all the animals. Animals receiving high concentrate level (PH group) presented lower (P < 0.05) skatole values (5.83 area arbitrary units in perirenal fat) than animals receiving low concentrate level (HL and GL groups, 6.23 and 6.71 area arbitrary units, respectively, in perirenal fat). Terpenoids, and especially sesquiterpenes, were found at higher levels and diversities in the PH than in the GL and HL animals. Two monoterpenoids allowed group discrimination considering perirenal or subcutaneous fat without distinction, whereas 11 and 5 sesquiterpenoids from perirenal and subcutaneous fat, respectively, allowed it.

Meta-analysis of the effect of animal maturity on muscle characteristics in different muscles, breeds, and sexes of cattle.

The effect of animal maturity on fiber cross-sectional area, percentage of fiber types, activities of isocitrate dehydrogenase (ICDH) and lactate dehydrogenase (LDH), total and insoluble collagen and lipid concentration was investigated in the longis-simus thoracis (LT), semitendinosus (ST), and triceps brachii (TB) muscles. The analysis considered 2,642 muscle samples from bulls, steers, and cows of Aubrac, Charolais, Limousin, Montbéliard, and Salers breeds. For the bulls, the fiber cross-sectional area, percentage of slow oxidative fibers, and ICDH activity showed a quadratic relationship (P < 0.05), and the percentage of fast oxidative-glycolytic and fast glycolytic fibers and LDH activity showed a cubic relationship (P < 0.05) with increased maturity. A linear relationship was observed for the collagen and lipid muscle characteristics. The response equation coefficients for different muscles indicate that development of muscle characteristics is different for each muscle. Compared with the other muscles, ST muscle had a greater fiber cross-sectional area, proportion of fast glycolytic fibers, LDH activity, and collagen content. The LT muscle had a greater proportion of slow-oxidative fibers and lipid (P < 0.05). Within the ST muscle, all characteristics except lipid concentration showed different development between the breeds. Steers showed greater changes in muscle fiber cross-sectional area, percentage of fast oxidative-glycolytic and fast glycolytic fibers, and total lipid in the muscle with increasing maturity compared with bulls. The mean fiber cross-sectional area and percentage of fast glycolytic fibers was greater and the mean lipid concentration was less in bulls compared with steers (P < 0.05). Data for cows were from more mature animals. Muscle characteristics in cows did not show large changes with increasing degree of maturity. Muscle type accounts for a greater proportion of the variation in the muscle characteristics than breed and sex of the animal.

Young Salers suckled bull production: effect of diet on performance, carcass and muscle characteristics and meat quality.

The aim of this work was to improve the knowledge on young suckled Salers bull production and to study the effect of forage type and concentrate level on performance, carcass and muscle characteristics as well as on meat quality. Twenty-four Salers male calves of 150 days of age were assigned to six groups: C0 (fed exclusively with hay and dam's milk and slaughtered at approximately 6 months of age), and HH (hay - high concentrate), HL (hay - low concentrate), GH (cut grass - high concentrate), GL (cut grass - low concentrate) and CP (control pasture: pasture - high concentrate) groups differing in feeds received until slaughter and slaughtered unweaned at approximately 10 months of age. Carcass weights averaged 210 kg at 10 months of age at slaughter. Average daily weight gain (ADWG) in HH and GH groups tended to be higher (P = 0.09) than in HL and GL groups (1354 v. 1248 g/day). ADWG in CP group (1542 g/day) was higher (P < 0.05) than in the other groups. Carcass weight in CP group (230 kg) tended to be higher (P < 0.1) than in HL (198 kg) and GL (200 kg) groups. Carcass muscle weight was higher (P < 0.05) in GH (155 kg) and CP groups (165 kg) than in HL (141 kg) and GL (142 kg) groups. Carcass and offal fatty tissue weights and carcass fatness did not differ between groups. Neither forage type nor concentrate level had significant effect on the area of muscle fibres or on muscle metabolic enzyme activities (namely, lactate dehydrogenase - LDH, phosphofructokinase - PFK, isocitrate dehydrogenase - ICDH, citrate synthase - CS and cytochrome-c oxidase - COX). semitendinosus muscle of CP group presented higher CS enzyme activities (8.10 µmol/min per g) than HH (5.30 µmol/min per g) and GL (4.52 µmol/min per g) groups. Neither total nor insoluble collagen content significantly differed between groups. Lipid content in rectus abdominis muscle was relatively low (average 67.5 mg/g dry matter) and was not affected by diet (P > 0.05). The ratio between n-6 and n-3 polyunsaturated fatty acid content was lower (P = 0.01) in the low-concentrate-fed than in the high-concentrate-fed group (3.95 v. 5.37, respectively). Sensory analysis noted that longissimus thoracis muscle from CP animals was more tender and juicy than that from HH and GH animals (P < 0.05).

Reflectance spectrum of adipose tissue to trace grass feeding in sheep: influence of measurement site and shrinkage time after slaughter.

The signature of carotenoid pigments stored in the caudal fat has been used to discriminate carcasses of lambs raised on pasture from those fed concentrates. However, the literature reports higher concentration of carotenoids in perirenal than in caudal fat, and it is likely that carotenoid concentration in fat increases with shrinkage time. Our objectives were to investigate the effects of measurement site and shrinkage time after slaughter on the reliability of the discrimination between grass- and concentrate-fed lambs. Thirty-two lambs were fed concentrate-based diets (stall, n = 16) or grazed a natural pasture in France (grass, n = 16). The concentrate supply was regulated to have similar ADG between the two treatments. Periodically lambs weighing about 35 kg were slaughtered. Reflectance spectrum and lightness (L*), redness (a*), and yellowness (b*) were measured at slaughter and after 24 h of shrinkage in the subcutaneous caudal and in the perirenal fat. The spectra were translated to have a value of reflectance at 510 nm = 0 and the integral of the translated spectrum was calculated between 450 and 510 nm (i.e., the zone of light absorption by carotenoids). The integral value of subcutaneous caudal fat at slaughter differed between stall- and grass-fed lambs (P < 0.05) but was not reliable to discriminate between feeding treatments. After 24-h shrinkage, the discrimination was better but was uncertain for 50% of the lambs. The integral value of perirenal fat at slaughter allowed us to discriminate all the lambs fed concentrates (16) from all those fed pasture (16). After 24-h shrinkage, the discrimination based on perirenal fat was partially compromised; 21.9% of the animals were not correctly discriminated. The integral value of the translated spectrum was highly (P < 0.001) correlated with the fat yellowness (b*), but the b* value was not reliable to discriminate between feeding treatments. However, plotting yellowness (b*) against redness (a*) values allowed us to discriminate 31 out of 32 lambs. Measuring reflectance spectrum of perirenal fat at slaughter allowed for complete discrimination of grass-fed from stall-fed lambs. However, because the integral values were affected by shrinkage time, measurements should be rigorously made immediately after slaughter.

Effect of grass or concentrate feeding systems on lamb carcass and meat quality.

Thirty-two male Ile de France lambs were divided into four equal groups at age 37 days. Two groups were allowed to graze a natural pasture in France each at a different growth rate (grass high and grass low groups). The other two groups were raised in stalls and fed concentrates to achieve the same growth rates (stall high and stall low groups, respectively) as from the grass groups. The animals were slaughtered when they attained 35 kg and their carcass and meat quality were evaluated. Animals from the two high growth rate groups were slaughtered at an average age of 129 days while those from the low growth rate groups were slaughtered at 163 days. Carcasses from stall-fed lambs were heavier than those from grass-fed lambs as the digestive tract percentage was higher in the grass lambs. Carcasses from stall lambs had better muscular conformation score (P <0.05) and were fattier than those from grass-fed animals. Subcutaneous fat was more yellow and harder in grass-fed lambs (P <0.05). Meat from grass-fed lambs was darker (P <0.05) in colour (lower L*) than meat from stall animals up to 24 h of display. Meat from stall fed animals was more tender and juicier than meat from grass-fed animals (P <0.01), as judged by a trained panel of assessors. Typical lamb flavour was higher in stall-fed lambs (P <0.01). Meat from grass-fed animals had more pronounced liver flavour (P <0.05) and less fatty flavour (P <0.01) than stall-fed lambs. Overall the difference in meat quality between the two different growth rates was minimal.

Maintenance requirements in metabolizable energy of adult, nonpregnant, nonlactating Charolais cows.

The objective of this study was to determine the maintenance requirements in metabolizable energy (MEm) of adult, nonlactating, nonpregnant Charolais cows. A feeding trial was conducted using 12 cows fed at one of two feeding levels (75 [L] and 113 [H] kcal of ME.kg BW-.75.d-1) for 116 d. Body composition was estimated from subcutaneous adipocyte diameter. Body weight changes averaged -468 and +46 g/d, respectively. Diet DM digestibility averaged .496. The L cows spent less time eating and ruminating but had other behavioral characteristics similar to those of H cows. Estimates of MEm were calculated from BW or body composition changes and amounted to 109 and 124 kcal of ME.kg BW-.75.d-1, respectively. Heat production (HP) was then measured over 67 d in a second trial on two L and two H cows from the feeding trial and planes of feeding were switched after 14 d. Estimates of MEm varied from 112 to 105 kcal.kg BW-.75.d-1. Within animal, day-to-day variations in heat production were high (4.6% on average) and prevented the detection of any precise changes of HP with time on treatment. None of the trials showed any significant effect of level of feeding on MEm.

[Use of urea as a marker of body water in Friesian cows]. / Utilisation de l'urée comme marqueur de l'eau corporelle chez des vaches Pie-noires.

Urea was used as a marker body water. Twelve catheterized dairy cows were injected with urea for 3 consecutive days. Equilibrium between injected and endogenous urea was obtained at 35.9 min over the 3 d. Different models to estimate urea space (EU) were compared with body water estimated at slaughter. The standard error was minimum when using the mean of EU on the 3 daily estimates obtained at 20 min. However, repeatability of EU measurement was low.