The objective of this study was to evaluate the effect of variations in milk protein composition on milk clotting properties and cheese yield. Milk was collected from 134 dairy cows of Swedish Red and White, Swedish Holstein, and Danish Holstein-Friesian breed at 3 sampling occasions. Concentrations of -, -, and -casein (CN), α-lactalbumin, and -lactoglobulin (LG) A and B were determined by reversed phase liquid chromatography. Cows of Swedish breeds were genotyped for genetic variants of - and κ-CN. Model cheeses were produced from individual skimmed milk samples and the milk clotting properties were evaluated. More than 30% of the samples were poorly coagulating or noncoagulating, resulting in weak or no coagulum, respectively. Poorly and noncoagulating samples were associated with a low concentration of κ-CN and a low proportion of κ-CN in relation to total CN analyzed. Furthermore, the κ-CN concentration was higher in milk from cows with the AB genotype than the AA genotype of κ-CN. The concentrations of α -, -, and κ-CN and of -LG B were found to be significant for the cheese yield, expressed as grams of cheese per one hundred grams of milk. The ratio of CN to total protein analyzed and the -LG B concentration positively affected cheese yield, expressed as grams of dry cheese solids per one hundred grams of milk protein, whereas -LG A had a negative effect. Cheese-making properties could be improved by selecting milk with high concentrations of α -, -, and κ-CN, with high κ-CN in relation to total CN and milk that contains -LG B.
In early lactation, dairy cows typically have a negative energy balance which has been related to metabolic disorders, compromised health and fertility, and reduced productive lifespan. Assessment of the energy balance, however, is not easy on the farm. Our aims were to investigate the milk metabolic profiles of dairy cows in early lactation, and to obtain models to estimate energy balance from milk metabolomics data and milk production traits. Milk samples were collected in week 2 and 7 after calving from 31 dairy cows. For each cow, the energy balance was calculated from energy intake, milk production traits and body weight. A total of 52 milk metabolites were detected using LC-QQQ-MS. Data from different lactation weeks was analysed by partial least squares analysis, the top 15 most relevant variables from the metabolomics data related to energy balance were used to develop reduced linear models to estimate energy balance by forward selection regression. Milk fat yield, glycine, choline and carnitine were important variables to estimate energy balance (adjusted R-2: 0.53 to 0.87, depending on the model). The relationship of these milk metabolites with energy balance is proposed to be related to their roles in cell renewal.
The objective of this study was to investigate the effects of differing levels of competition for feed access on group-housed dairy cows and on the variation in feeding behavior between individuals within the group. We hypothesized that, as competition increases, (1) cows will consume feed faster and in larger meals, and (2) individuals within the group will experience greater variability in feed consumption patterns. Eighteen lactating Holstein dairy cows with average DIM of 77 ± 20 d and production of 46 ± 7 kg/d at the start of the trial, were divided into groups of three, and fed three times per day. Groups were exposed to each of three competition levels: high (3 cows: 1 feed bin), moderate (3 cows: 2 feed bins), and low (3 cows: 3 feed bins). Treatments were assigned in random order according to a modified Latin Square design and applied for 10 d. DMI and feeding behavior (feeding time, feeding rate, and meal patterns) for each cow were recorded using an automated feed intake system on d 6 to 10 of each period. Data were summarized by group and treatment period, and analyzed in a general linear mixed model. DMI (29.1 kg/d) was found to be similar (P = 0.63) across treatments. Increased competition resulted in a reduction in feeding time (low = 202.6, moderate = 194.9, high = 83.6 min/d; SED = 4.49; P = 0.015), especially following fresh feed delivery and milking. Rate of feed intake increased with greater competition (low = 0.16; moderate = 0.18; high = 0.20 kg DM/min; SED = 0.01; P = 0.01). Meal frequency (8 meals/d) and size (4.0 kg DM/meal) were unaffected by treatment (P > 0.40), while meal length increased under high competition (low = 37.0; moderate = 36.6; high = 47.3 min/meal; SED = 3.7; P = 0.046). This was due to greater within-meal nonfeeding time, which at the high competition level, was approximately double that of the other treatment levels (low = 10.0; moderate = 10.8; high = 20.3 min/meal; SED = 2.3; P = 0.008). Analysis of individual within group variability, calculated as the daily SD of each group averaged across d 6 to 10, revealed treatment differences in variability of meal length (low = 12.0; moderate = 13.9; high = 29.0 min/ meal; SED = 5.56; P = 0.04) and within-meal nonfeeding time (low = 6.4; moderate = 8.3; high = 21.5 min/meal; SED = 4.57; P = 0.03). These results suggest that at elevated competition levels, cows modify their feeding behavior to consume more feed in a shorter period of time and devote a large portion of their meal time toward waiting to gain feed access. Further, there is greater variability in meal patterns within groups at higher levels of competition for feed access.
Dairy production systems are often criticized as being major emitters of greenhouse gases (GHG). In this context, the extension of the length of the productive life of dairy cows is gaining interest as a potential GHG mitigation option. In the present study, we investigated cow and system GHG emission intensity and profitability based on data from 30 dairy cows of different productive lifetime fed either no or limited amounts of concentrate. Detailed information concerning productivity, feeding and individual enteric methane emissions of the individuals was available from a controlled experiment and herd book databases. A simplified GHG balance was calculated for each animal based on the milk produced at the time of the experiment and for their entire lifetime milk production. For the lifetime production, we also included the emissions arising from potential beef produced by fattening the offspring of the dairy cows. This accounted for the effect that changes in the length of productive life will affect the replacement rate and thus the number of calves that can be used for beef production. Profitability was assessed by calculating revenues and full economic costs for the cows in the data set. Both emission intensity and profitability were most favourable in cows with long productive life, whereas cows that had not finished their first lactation performed particularly unfavourably with regard to their emissions per unit of product and rearing costs were mostly not repaid. Including the potential beef production, GHG emissions in relation to total production of animal protein also decreased with age, but the overall variability was greater, as the individual cow history (lifetime milk yield, twin births, stillbirths, etc) added further sources of variation. The present results show that increasing the length of productive life of dairy cows is a viable way to reduce the climate impact and to improve profitability of dairy production.
The objective of this study was to investigate the effect of milk proteins on rennet coagulation properties. Milk samples ( = 516) were taken from 54 cows once a month during one full lactation period and analysed for rennet coagulation properties, and for contents of α -, α -, β- and κ-casein, and β-lactoglobulin. The contents of the analysed milk proteins and the relative contents of different caseins (Cn) in total casein were significantly influenced by sampling month, breed, and the month of lactation. An increase in milk protein, casein, casein fractions, and the casein number decreased the rennet coagulation time of milk and increased curd firmness. Milk formed a firmer curd when the relative content of α - and β-Cn in total casein was lower, or the relative content of κ-Cn in total casein was higher. Higher values of κ-Cn:β-Cn and κ-Cn:α -Cn ratios had a positive effect on curd firmness.
Optimisation of cheese yield is crucial for cheese production; a previous study showed large variations in chymosin-induced coagulation in milk from the second most common Swedish dairy breed, Swedish Red. In the present study, the effect of gross composition, protein composition, total and ionic calcium content, phosphorous content and casein micelle size on chymosin-induced gelation was determined in milk from 98 Swedish Red cows. The study showed that protein content and total calcium content, ionic calcium concentration and casein micelle size were the most important factors explaining the variation of gelation properties in this sample set. Non-coagulating milk was suggested to have lower ionic and total calcium content as well as lower relative concentrations of β-lactoglobulin than coagulating milk. The lower total calcium content in non-coagulating milk poses a problem as the difference was, theoretically, four times larger than the amount of calcium that is normally added in cheese processing.
This study investigated the effects of feeding system on diurnal enteric methane (CH4) emissions from individual cows on commercial farms. Data were obtained from 830 cows across 12 farms, and data collated included production records, CH4 measurements (in the breath of cows using CH4 analysers at robotic milking stations for at least seven days) and diet composition. Cows received either a partial mixed ration (PMR) or a PMR with grazing. A linear mixed model was used to describe variation in CH4 emissions per individual cow and assess the effect of feeding system. Methane emissions followed a consistent diurnal pattern across both feeding systems, with emissions lowest between 05:00 and 08:59, and with a peak concentration between 17:00 and 20:59. No overall difference in emissions was found between feeding systems studied; however, differences were found in the diurnal pattern of CH4 emissions between feeding systems. The response in emissions to increasing dry matter intake was higher for cows fed PMR with grazing. This study showed that repeated spot measurements of CH4 emissions whilst cows are milked can be used to assess the effects of feeding system and potentially benchmark farms on level of emissions.
Optimisation of cheese yield is crucial for cheese production; a previous study showed large variations in chymosin-induced coagulation in milk from the second most common Swedish dairy breed, Swedish Red. In the present study, the effect of gross composition, protein composition, total and ionic calcium content, phosphorous content and casein micelle size on chymosin-induced gelation was determined in milk from 98 Swedish Red cows. The study showed that protein content and total calcium content, ionic calcium concentration and casein micelle size were the most important factors explaining the variation of gelation properties in this sample set. Non-coagulating milk was suggested to have lower ionic and total calcium content as well as lower relative concentrations of beta-lactoglobulin than coagulating milk. The lower total calcium content in non-coagulating milk poses a problem as the difference was, theoretically, four times larger than the amount of calcium that is normally added in cheese processing. (C) 2014 Elsevier Ltd. All rights reserved.