Fresh grass in the cow diet improves the rheological and nutritional properties of butter. However, the relationship between the proportion of fresh grass in the diet and these properties is still unknown. The objective of the study was to determine the relationship between the proportion of fresh grass in the diet and the properties of milk and butter. Four groups of 2 cows were fed 4 isoenergetic diets characterized by increasing amounts of fresh grass (0, 30, 60, and 100% dry matter of forage) according to a Youden square design. Energy levels were similar among all diets. Thus, no effect of mobilization was observed and the results were only due to the proportion of fresh grass in the diet. Milk yield linearly increased with the proportion of fresh grass in the diet (+0.21 kg/d per 10% of grass). Fat yield remained unchanged. Thus, by effect of dilution, increasing the proportion of fresh grass in the diet induced a linear decrease in fat content. Milk fat globule size decreased by 0.29 mum when the proportion of grass reached 30% in the diet. Increasing the proportion of fresh grass in the diet induced a linear increase in unsaturated fatty acids percentages at the expense of saturated fatty acids. Relationships were +0.38, +0.12, +0.05 and -0.69 points/10% of fresh grass in the diet for C18:1 trans-11, C18:2 cis-9,trans-11, C18:3n-3, and C16:0, respectively. These modifications in fatty acid composition, and in particular in the spreadability index, C16:0/C18:1, were responsible for linear decreases in final melting temperature and solid fat content in butter fat, perceived in sensory analysis by a linear decrease in firmness in mouth. The nutritional value of butter was also linearly improved by the proportion of fresh grass in the diet by halving the atherogenicity index.

The aim of this experiment was to compare the effects of increasing amounts of extruded linseed in dairy cow diet on milk fat yield, milk fatty acid (FA) composition, milk fat globule size, and butter properties. Thirty-six Prim'Holstein cows at 104 d in milk were sorted into 3 groups by milk production and milk fat globule size. Three diets were assigned: a total mixed ration (control) consisting of corn silage (70%) and concentrate (30%), or a supplemented ration based on the control ration but where part of the concentrate energy was replaced on a dry matter basis by 2.1% (LIN1) or 4.3% (LIN2) extruded linseed. The increased amounts of extruded linseed linearly decreased milk fat content and milk fat globule size and linearly increased the percentage of milk unsaturated FA, specifically alpha-linolenic acid and trans FA. Extruded linseed had no significant effect on butter color or on the sensory properties of butters, with only butter texture in the mouth improved. The LIN2 treatment induced a net improvement of milk nutritional properties but also created problems with transforming the cream into butter. The butters obtained were highly spreadable and melt-in-the-mouth, with no pronounced deficiency in taste. The LIN1 treatment appeared to offer a good tradeoff of improved milk FA profile and little effect on butter-making while still offering butters with improved functional properties.

Data from birth to slaughter of cull cows allowed using a PCA-based approach coupled with the iterative K-means algorithm the identification of three rearing practices classes. The classes were different in their carcass characteristics. Old cows raised mainly on pasture have better carcass characteristics, while having an equivalent tenderness, juiciness, flavor, intramuscular fat content, and pHu to those fattened with hay or haylage. The Longissimus thoracis muscle of the cows raised on pasture (with high physical activity) showed greater proportions of IIA fibers at the expense of the fast IIX ones. Accordingly, the meat of these animals have better color characteristics. Superoxide dismutase (SOD1) and αB-crystallin quantified by Dot-Blot were the only other biomarkers to be more abundant in "Grass" class compared to "Hay" and "Haylage" classes. The relationships between the biomarkers and the 6 carcass and 11 meat quality traits were investigated using multiple regression analyses per rearing practices. The associations were rearing practice class and phenotype trait-dependent. ICDH and TP53 were common for the three classes, but the direction of their entrance was different. In addition, rearing practices and carcass traits were not related with Hsp70-Grp75 and μ-calpain abundances. The other relationships were specific for two or one rearing practices class. The rearing practices dependency of the relationships was also found with meat quality traits. Certain proteins were for the first time related with some beef quality traits. MyHC-IIx, PGM1, Hsp40, ICDH, and Hsp70-Grp75 were common for the three rearing practices classes and retained to explain at list one beef quality trait. A positive relationship was found between PGM1 and hue angle irrespective of rearing practices class. This study confirms once again that production-related traits in livestock are the result of sophisticated biological processes finely orchestrated during the life of the animal and soon after slaughter.

The objective of this study was to examine the synthesis and composition of milk produced by dairy cows that secrete either small milk fat globules (SMFG) or large milk fat globules (LMFG), and to study their response to diets known to alter milk composition. Four groups of 3 multiparous dairy cows were assigned to 2 isoenergetic feeding treatments: a corn silage treatment supplemented with soybean meal, and fresh pasture supplemented with cereal concentrate. The 4 groups comprised 2 groups of 3 dairy cows that produced SMFG (3.44 microm) and 2 groups of 3 dairy cows that produced LMFG (4.53 microm). The SMFG dairy cows produced higher yields of milk, protein, and calcium. Nevertheless, their milk had lower fat and protein contents. Both SMFG and LMFG cows secreted similar amounts of milk fat; therefore, higher globule membrane contents in milk fat were observed in SMFG cows. Higher calcium mineralization of the casein micelles in SMFG cows suggests that it may be possible to improve cheese-making properties even if the lower protein content may lead to lower cheese yields. The SMFG cows secrete milk fat with a higher concentration of monounsaturated fatty acids and a lower concentration of short-chain fatty acids. They also have a higher C18:1/C18:0 ratio than LMFG cows. This suggests that SMFG cows have more significant fatty acid elongation and desaturation. The pasture treatment led to an increase in milk and protein yields because of increased energy intake. It also resulted in lower milk fat yield and fat and protein contents. The pasture treatment led to a decrease in milk fat globule size and, as expected, an increase in monounsaturated and polyunsaturated fatty acid contents. However, it induced a decrease in the protein content, and in calcium mineralization of casein micelles, which suggests that this type of milk would be less suitable for making cheese. This study also shows that there is no correlation between the cows, based on milk fat globule size and diet. These results open up possibilities for improving milk fat quality based on milk fat globule size, and composition. The mechanisms involved in milk fat globule secretion are still to be determined.

This study investigated the relationships among a list of 23 protein biomarkers with CIE-L*a*b* meat color traits and ultimate pH on Longissimus thoracis (LT) and Rectus abdominis (RA) muscles of 48 protected designation of origin Maine-Anjou cows. The technological parameters were correlated with several biomarkers and were in some cases muscle-dependent. More biomarkers were related to pHu in LT than in RA muscle. Some consistencies were found, by the common correlation of pHu with MyHC-IIa and MyHC-IIx. The pHu of the LT muscle was also correlated with other cytoskeletal entities and proteins belonging to metabolism and cellular stress. In contrast to the relationships found between biomarkers and LT pHu, more proteins were related to the instrumental color coordinates in RA than in LT muscle. The regression equations were parameter- and muscle-dependent. Certain of the retained proteins explained more than one color coordinate. Hsp70-Grp75 was positive in the models of L*, a*, b*, and C* of LT and of b* in the RA muscle. Further heat shock proteins were strongly related with the meat color coordinates in both muscles. The involvement of metabolic enzymes and myofibrillar proteins in the meat color development was also verified in this experiment. This study confirmed once again the importance of numerous biological pathways in beef color.