Risk factors associated with milk fever occurrence in grazing dairy cattle

The aim of this study was to determine risk factors associated with milk fever (MF) occurrence in Costa Rican grazing dairy cattle. A total of 69,870 cows from 126 dairy herds were included in the study. Data were collected in the Veterinary Automated Management and Production Control Program software by the Population Medicine Research Program of the Veterinary Medicine School, National University of Costa Rica, from 1985 to 2014. To determine the risk factors for MF, 2 logistic regression mixed models were evaluated. The first model used breed, month of calving, ecological life zone, herd nested within ecological life zone, and parity as fixed effects. The second model excluded first-lactation animals and cows without production information, had the same fixed effects of the first model, and added previous MF case, previous lactation length, previous dry period length, previous corrected 305-d milk yield, and calving interval length as fixed effects. Both models used animal and year as random effects. Of the 235,971 recorded lactations, 4,312 (1.83%) reported MF event. The significantly associated risk factors for MF occurrence, ranked by their highest odds ratio (OR), were parity (OR = 52.59), previous dry period length (OR = 4.21), ecological life zone (OR = 3.20), breed (OR = 3.04), previous corrected 305-d milk yield (OR = 2.39), previous MF case (OR = 2.35), and month of calving (OR = 1.36). The findings of this study are the first data reported using an epidemiological approach to study risk factors for MF in Costa Rican dairy cattle. Some of these results might be used to improve preventive management practices at the farms to reduce the incidence of this metabolic disease in grazing dairy herds.     

Influence of precalving feed allowance on periparturient metabolic and hormonal responses and milk production in grazing dairy cows

Fifty-two multiparous dairy cows were allocated to 4 treatments consuming 5.4, 8.2, 10.0, or 11.0 kg/d of pasture dry matter per cow for 27 +/- 9.6 d precalving. This equated to 1.3, 1.9, 2.4, and 2.6% of body weight (BW; not including the conceptus weight). Following calving, all cows were fed ad libitum on pasture. Blood was sampled 17 d precalving, on day of calving, and on d 1, 2, 3, 4, 7, 14, 28, and 35 postcalving. Results suggest that the near-term grazing dairy cow requires 1.05 MJ of ME/kg of BW(0.75) and that previous estimates of energy requirements were underestimated. Precalving plasma concentrations of glucose, insulin-like growth factor-1, and leptin increased quadratically with increasing pasture intake. This was associated with precalving plasma concentrations of growth hormone that declined linearly, and concentrations of nonesterified fatty acids and beta-hydroxybutyrate that declined quadratically with increasing dry matter intake (DMI). Postcalving plasma concentrations of these metabolites showed no lasting effect of precalving feeding. The effect of precalving nutrition on milk production was small, and other than milk fat, was confined to wk 1 postcalving. Milk fat yield increased with increasing precalving DMI and calving body condition score until wk 3 post-calving, after which treatment effects were not evident. These results indicate that the level of feeding in grazing dairy cows during the last month before calving has only small effects on cow metabolic and hormonal status, and on milk production in the first 5 wk of lactation.     

Short communication: Responses to supplemental Saccharomyces cerevisiae fermentation product and triticale grain in dairy cows grazing high-quality pasture in early lactation

Supplementing cows grazing highly digestible pasture with a Saccharomyces cerevisiae fermentation product (SCFP) was hypothesized to increase dry matter (DM) intake and milk production. Sixty multiparous dairy cows were fed 3 kg of crushed triticale DM/cow per day for 23 ± 4.4 d before calving. Half of the cows received SCFP (60 g/d; Diamond V Original XP; Diamond V Mills, Inc., Cedar Rapids, IA). Cows in both treatment groups were randomly allocated at calving to 1 of 2 amounts (3 or 6 kg of DM/d) of triticale feeding with or without 60 g of SCFP/day (n = 15/treatment) until 84 days in milk. The amount of pasture harvested (kg of DM/cow per day) and milk yield (kg/cow per day) were not affected by SCFP. Milk protein content and yield were greater in cows receiving 6 kg of crushed triticale DM/d. Plasma nonesterified fatty acids and β-hydroxybutyrate concentrations were not affected by SCFP supplementation, but were lower in cows fed 6 kg of crushed triticale DM/d than those fed 3 kg of DM/d. Supplementation with SCFP increased milk lactose content without affecting milk production under the conditions investigated.     

Meta-analysis of the effect of pasture allowance on pasture intake,milk production,and grazing behavior of dairy cows grazing temperate grasslands

Daily pasture allowance (PA) is defined as the product of pregrazing pasture mass and offered area, and is the major grazing management factor determining pasture utilization per unit area and daily performance of grazing dairy cows. The objective of the present study was to perform a meta-analysis reviewing the effect of PA on pasture intake, milk production, milk composition, and grazing behavior of dairy cows. Experiments studying the effect of PA on pasture intake or milk production, which eventually included milk composition or grazing behavior data, or both, were selected to create a database. Papers were selected only if at least 2 PA were compared under the same experimental conditions, particularly the same pasture mass (i.e., where PA levels were only obtained through changes in daily offered area). The final database included 97 PA comparisons reported in 56 papers. For analytical purposes, the database was subdivided into 3 subsets that varied according to the estimation height (EH) at which PA was determined; that is, PA above ground level (PA₀ subset), PA above 2.5 to 3.5 cm (PA₃ subset), and PA above 4 to 5 cm (PA₅ subset). Statistical analyses were conducted independently on the PA₀, PA₃, and PA₅ subsets and on the whole database (global analysis) by using linear and nonlinear mixed-model procedures. The curves, either exponential, quadratic, or linear, describing the effects of PA on pasture intake, milk production, or grazing behavior of dairy cows are conceptually similar, whatever the EH. The equations describing these curves are, however, specific for each EH. Accordingly, from typical low to high PA, the increase in pasture intake (0.13 vs. 0.21 vs. 0.28 kg/kg of PA), milk production (0.11 vs. 0.17 vs. 0.24 kg/kg of PA), and milk solids production (0.008 vs. 0.010 vs. 0.013 kg/kg of PA) per kilogram of increase in PA was lower for PA₀ than for PA₃, and for PA₃ than for PA₅. Grazing time increased from low to medium PA and did not vary from medium to high PA. Pasture intake rate seemed to increase from low to medium PA because of greater bite mass, whereas it increased from medium to high PA because of greater biting rate. The present meta-analysis demonstrated that the general relationship between PA and any dependent variable is quite strong and independent of EH. This suggests no specific relationship for some parts of the world or methodology approach, with a high portability of the global equations calculated here. These results are useful for improving grazing management and modeling on pasture-based dairy systems.     

Association of postpartum hypocalcemia with early-lactation milk yield,reproductive performance,and culling in dairy cows

Periparturient hypocalcemia is frequently observed and considered as a gateway disease that is associated with various health issues. The objective of this study was to evaluate the association of hypocalcemia with early-lactation milk yield, reproductive performance, and culling across a large number of different managerial systems. A prospective cohort study was conducted based on a convenience sample of 125 dairy herds from 8 federal states of Germany between February 2015 and August 2016. A blood sample was drawn from 1,709 animals within 48 h after parturition and analyzed for serum calcium concentration. After discarding cows (n = 283) with missing data, a total of 1,426 cows were considered for final analyses. The median time from calving to sampling was 14.0 h (interquartile range = 5.0–24.9 h). For each herd, a record of the herd management software was requested 150 d after the last cow was sampled. Serum calcium concentration of each cow was associated with early-lactation milk yield (Dairy Herd Improvement Association equivalent test 1 to 3), reproductive performance [days in milk (DIM) at first artificial insemination (AI), pregnancy at first AI, time to pregnancy within 150 DIM], and culling (until 60 DIM) data. Generalized linear mixed models were used to analyze continuous or categorical data. Shared frailty models were used for time to event data. Five different thresholds were used to define hypocalcemia. Thresholds ranged from 1.8 to 2.2 mmol/L using 0.1-mmol/L increments. Clinical hypocalcemia was defined as serum calcium concentration <2.0 mmol/L in combination with clinical signs (e.g., recumbency). The effect of hypocalcemia on milk yield was conditional on parity. In primiparous cows a serum calcium concentration <2.0 mmol/L (6.4% of cows were below this threshold) had no effect on milk production, whereas there was a tendency for multiparous cows with a serum calcium concentration <2.1 mmol/L (63.2% of cows were below this threshold) to produce 0.80 kg/d more milk compared with multiparous cows at or above the threshold. Multiparous cows suffering from clinical hypocalcemia produced 2.19 kg/d less milk compared with normocalcemic cows in early lactation. Calcium status was not associated with days to first insemination. Cows with a serum calcium concentration <1.9 mmol/L (34.6% of cows below this threshold) had decreased odds (odds ratio = 0.56) of pregnancy at first AI. A serum calcium concentration <1.8 mmol/L (24.1% of cows below this threshold) had a significant effect on time to pregnancy. Compared with animals with a serum calcium concentration ≥1.8 mmol/L, the hazard of becoming pregnant within 150 DIM was reduced when cows had a serum calcium concentration <1.8 mmol/L (hazard ratio = 0.68). Cows with a serum calcium concentration <2.0 mmol/L (44.3% of cows were below this threshold) had a 1.69 times greater hazard of being culled within the first 60 DIM compared with normocalcemic animals. The present study shows that the association of hypocalcemia with milk yield was conditional on parity and serum calcium concentration measured once within 48 h after calving. Considering reproductive performance and culling in early lactation, a negative effect of postpartum hypocalcemia was demonstrated.     

Effects of animal selection on milk composition and processability

One goal of animal breeding is to increase the economic output through increased production, improved milk quality, and cow health. The objective of this study was to evaluate genetic progress in relation to milk composition, processability, and yield as a correlated response to selection for the Swedish breeding objective. Dairy cows with high genetic merit, classified as elite dairy cows, of the Swedish Red and Swedish Holstein breeds were used. Milk samples were collected on the farm level in winter and summer from a research herd at Nötcenter Viken, a bovine research farm in Sweden. Comparisons were made with milk from a Swedish Red herd, a Swedish Holstein herd, and a Swedish dairy processor in the same geographical area. Protein, lipid, and carbohydrate profiles as well as minerals were analyzed, and technological properties, including rennet-induced gelation characteristics, lipid oxidation, total antioxidant capacity, and fat globule size, were determined. Higher yields were found for elite cows for components of the protein, lipid, and carbohydrate profiles as well as for minerals, implying genetic progress in relation to milk yield; however, the content of some milk components (e.g., lipid and whey protein contents) had decreased on average. Milk from the elite cows had good gelation characteristics, but was more susceptible to lipid autooxidation and had a lower total antioxidant capacity. These results demonstrate that milk composition and processing characteristics could be used to adjust breeding practices to optimize the quality and stability of milk and dairy products.     

Effect of level of oil inclusion in the diet of dairy cows at pasture on animal performance and milk composition and properties

The effect of including additional oil, incorporated as whole rapeseeds, in the diet of 64 Holstein–Friesian dairy cows (32 mid‐ and 32 late‐lactation) at pasture on animal performance and milk fat composition and properties was followed over a continuous trial of 20 weeks duration. Within two stages of lactation (mid, 130 ± 16.2 days, or late, 231 ± 58.9 days), cows were allocated to concentrate treatments representing four levels of rapeseed oil inclusion, 0 (control), 200, 400 and 600 g oil day^?1. Oil inclusion had little effect on milk yield but decreased milk fat content significantly (P < 0.01), with a mean depression of 0.40% at the highest level of oil inclusion. The content of milk protein also decreased with increasing addition of oil, but the decrease was smaller than the milk fat depression and was not statistically significant. Increasing the level of rapeseed oil in the diet to 600 g oil day^?1 resulted in linear changes in milk fat and protein concentrations which were described by regression equations. For each 100 g of rapeseed oil added to the diet, milk fat content decreased by 0.068% in mid‐lactation cows and 0.061% in late‐lactation cows, while protein content decreased by 0.026% in mid‐lactation cows and 0.028% in late‐lactation cows. Total unsaturated fatty acid content of milk fat also increased in a linear fashion with increased level of oil addition, from 345.7 g kg^?1 total fatty acids in control milk fat to 459.3 g kg^?1 total fatty acids at 600 g oil day^?1, while total saturated fatty acids decreased in the same milk fats from 640.7 to 522.2 g kg^?1 total fatty acids. These changes were reflected in lower solid fat contents (SFC) in the milk fat at the lower temperatures of measurement, eg 41% SFC at 5 °C at the highest level of oil inclusion compared with 52% in the control milk fat. However, SFC at 20 °C showed little difference with increasing level of dietary oil addition, an important factor in maintaining product integrity at room temperatures. The relatively high content of the monounsaturated fatty acid C18:1 (345.5 g kg^?1 total fatty acids at 600 g oil day^?1) and low content of polyunsaturated fatty acids (total C18:2 and C18:3 <40 g kg^?1 total fatty acids at 600 g oil day^?1) ensured that the oxidative stability of the treatment and control milk fats did not differ significantly. Stage of lactation had an unexplained effect of consistent magnitude on milk fat composition throughout the trial period, with late‐lactation animals producing milk fats containing a significantly (P < 0.001) higher proportion of unsaturated fatty acids than the mid‐lactation animals. Changes in the proportions of unsaturated fatty acids in milk fat, as reflected by changes in iodine value, were established within 2 weeks of the trial commencing and persisted over the 20 weeks of the trial duration. No adverse effect on animal health from this type of dietary manipulation was identified. Copyright © 2004 Society of Chemical Industry     

Production,milk fatty acid profile,and nutrient utilization in grazing dairy cows supplemented with ground flaxseed

Flaxseed has been extensively used as a supplement for dairy cows because of its high concentrations of energy and the n-3 fatty acid (FA) cis-9,cis-12,cis-15 18:3. However, limited information is available regarding the effect of ground flaxseed on dry matter intake (DMI), ruminal fermentation, and nutrient utilization in grazing dairy cows. Twenty multiparous Jersey cows averaging (mean ± standard deviation) 111 ± 49 d in milk in the beginning of the study were used in a randomized complete block design to investigate the effects of supplementing herbage (i.e., grazed forage) with ground corn-soybean meal mix (control diet = CTRL) or ground flaxseed (flaxseed diet = FLX) on animal production, milk FA, ruminal metabolism, and nutrient digestibility. The study was conducted from June to September 2013, with data and sample collection taking place on wk 4, 8, 12, and 16. Cows were fed a diet formulated to yield a 60:40 forage-to-concentrate ratio consisting of (dry matter basis): 40% cool-season perennial herbage, 50% partial total mixed ration, and 10% of ground corn-soybean meal mix or 10% ground flaxseed. However, estimated herbage DMI averaged 5.59 kg/d or 34% of the total DMI. Significant treatment by week interactions were observed for milk and blood urea N, and several milk FA (e.g., trans-10 18:1). No significant differences between treatments were observed for herbage and total DMI, milk yield, feed efficiency, concentrations and yields of milk components, and urinary excretion of purine derivatives. Total-tract digestibility of organic matter decreased, whereas that of neutral detergent fiber increased with feeding FLX versus CTRL. No treatment effects were observed for ruminal concentrations of total volatile FA and NH₃-N, and ruminal proportions of acetate and propionate. Ruminal butyrate tended to decrease, and the acetate-to-propionate ratio decreased in the FLX diet. Most saturated and unsaturated FA in milk fat were changed. Specifically, milk proportion of cis-9,cis-12,cis-15 18:3, Σn-3 FA, and Σ18C FA increased, whereas that of cis-9,cis-12 18:2, Σn-6 FA, Σ odd-chain FA, Σ<16C FA, and Σ16C FA decreased with feeding FLX versus the CTRL diet. In conclusion, feeding FLX did not change yields of milk and milk components, but increased milk n-3 FA. Therefore, costs and industry adoption of premiums for n-3-enriched milk will determine the adoption of ground flaxseed in pasture-based dairy farms.     

Herbage dry matter intake estimation of grazing dairy cows based on animal,behavioral, environmental,and feed variables

Information about the individual herbage DMI (HDMI) of grazing dairy cows is important for an efficient use of pasture herbage as an animal feed with a range of benefits. Estimating HDMI, with its multifaceted influencing variables, is difficult but may be attempted using animal, performance, behavior, and feed variables. In our study, 2 types of approaches were explored: 1 for HDMI estimation under a global approach (GA), where all variables measured in the 4 underlying experiments were used for model development, and 1 for HDMI estimation in an approach without information about the amount of supplements fed in the barn (WSB). The accuracy of these models was assessed. The underlying data set was developed from 4 experiments with 52 GA and 50 WSB variables and one hundred thirty 7-d measurements. The experiments differed in pasture size, herbage allowance, pregrazing herbage mass, supplements fed in the barn, and sward composition. In all the experiments, cow behavioral characteristics were recorded using the RumiWatch system (Itin and Hoch GmbH, Liestal, Switzerland). Herbage intake was estimated by applying the n-alkane method. Finally, HDMI estimation models with a minimal relative prediction error of 11.1% for use under GA and 13.2% for use under WSB were developed. The variables retained for the GA model with the highest accuracy, determined through various selection steps, were herbage crude protein, chopped whole-plant corn silage intake in the barn, protein supplement or concentrate intake in the barn, body weight, milk yield, milk protein, milk lactose, lactation number, postgrazing herbage mass, and bite rate performed at pasture. Instead of the omitted amounts of feed intake in the barn and, due to the statistical procedure for model reduction, the unconsidered variables postgrazing herbage mass and bite rate performed at pasture, the WSB model with the highest accuracy retained additional variables. The additional variables were total eating chews performed at pasture and in the barn, total eating time performed at pasture, number of total prehension bites, number of prehension bites performed at pasture, and herbage ash concentration. Even though behavioral characteristics alone did not allow a sufficiently accurate individual HDMI estimation, their inclusion under WSB improved estimation accuracy and represented the most valid variables for the HDMI estimation under WSB. Under GA, the inclusion of behavioral characteristics in the HDMI estimation models did not reduce the root mean squared prediction error. Finally, further adaptation, as well as validation on a more comprehensive data set and the inclusion of variables excluded in this study such as body condition score or gestation, should be considered in the development of HDMI estimation models.     

Manipulating the dietary cation-anion difference via drenching to early-lactation dairy cows grazing pasture

Diets offered to grazing dairy cows can vary considerably in their dietary cation-anion difference (DCAD) and are often well in excess of what has been considered optimal. The effects of a range of DCAD on the health and production of pasture-based dairy cows in early lactation was examined in a randomized block design. Four groups of 8 cows were offered a generous allowance of pasture (45 +/- 6 kg/d of dry matter (DM) per cow) for 35 d and achieved mean pasture intakes of approximately 17 kg/d of DM per cow. Cows were drenched twice daily with varying combinations of mineral compounds to alter the DCAD. Dietary cation-anion difference ranged from +23 to +88 mEq/100 g of DM. A linear increase in blood pH and HCO(3)(-) concentration and blood base excess, and a curvilinear increase in the pH of urine with increasing DCAD indicated a nonrespiratory effect of DCAD on metabolic acid-base balance. Plasma concentrations of Mg, K, and Cl declined as DCAD increased, whereas Na concentration increased. Urinary excretion of Ca decreased linearly as DCAD increased, although the data suggest that the decline may be curvilinear. These results in conjunction with the increased concentrations of ionized Ca suggest that intestinal absorption of Ca or bone resorption, or both, increased as DCAD declined. Dry matter intake, as measured using indigestible markers, was not significantly affected by DCAD. However, the linear increase in the yield of linolenic acid, vaccenic acid, and cis-9, trans-11 conjugated linoleic acid in milk, as DCAD increased is consistent with a positive effect of DCAD on DM intake. Increasing DCAD did not significantly affect milk yield or milk protein, but the concentration and yield of milk fat linearly increased with increasing DCAD. The increased milk fat yield was predominantly a result of increased de novo synthesis in the mammary epithelial cells, although an increase in the yield of preformed fatty acids also occurred. Milk production results suggest that DCAD for optimal production on pasture diets may be higher than the +20 mEq/100 g of DM previously identified for total mixed rations.     

Effect of feeding level pre- and post-puberty and body weight at first calving on growth, milk production, and fertility in grazing dairy cows

The effect of feeding to achieve differential growth rates in Holstein-Friesian (HF; n = 259) and Jersey (n = 430) heifers on time to puberty and first lactation milk production was investigated in a 3 × 2 factorial design. Holstein-Friesian and Jersey calves were reared to achieve a BW of 100 and 80 kg, respectively, at 100 d. At target weight, all calves were randomly allocated to one of 3 feeding treatments to achieve different growth rates. Holstein-Friesian and Jersey calves were fed fresh pasture to achieve average daily growth rates of 0.77, 0.53, or 0.37 kg of BW/d (HF) and 0.61, 0.48, or 0.30 kg of BW/d (Jersey), respectively. Period 1 (prepubertal) was imposed until HF and Jersey treatment groups averaged 200 and 165 kg of BW, respectively. Following period 1, HF and Jersey calves from each treatment group were randomly allocated to one of 2 feeding treatments to achieve average daily growth rates of 0.69 or 0.49 kg of BW/d (HF) and 0.58 and 0.43 kg of BW/d (Jersey), respectively. Period 2 (postpubertal) was imposed until 22 mo, when heifers were returned to their farms of origin. Body weight, body condition score, height, heart girth circumference (HGC), milk production, and fertility-related data were collected until the end of the third lactation. Time to reach puberty was negatively associated with level of feeding, and heifers attained puberty at the same BW (251 ± 25.4 and 180 ± 24.0 kg for HF and Jersey heifers, respectively). Heifers on high feed allowances during periods 1 and 2 were heavier, taller, and had greater HGC than their slower grown counterparts until 39 mo of age when height and HGC measurements stopped. Body weight differences remained until 51 mo, when measurements ceased. High feed allowance during period 1 (prepubertal) did not affect milk production during the first 2 lactations, but did reduce milk production in lactation 3. It is possible that the expected negative effect of accelerated pre-pubertal growth was masked by greater calving BW, as BW-corrected milk yield declined in both breeds with increasing prepubertal feed allowance. Growth rate during period 2 was positively correlated with first lactation milk production. Milk yield increased 7% in first lactation heifers on the high feed allowance, which resulted in higher growth rate during period 2. Milk production during subsequent lactations was not affected. Results suggest that accelerated prepubertal growth may reduce mammary development in grazing dairy cows, but this does not affect milk production in early lactations because of superior size. Body weight at calving and postpubertal growth rate management are important in first lactation milk production, but do not affect milk production in subsequent lactations.     

Effect of restricted access time to pasture on dairy cow milk production, grazing behavior, and dry matter intake

The objective of this experiment was to investigate the effect of restricting pasture access time on milk production and composition, body weight and body condition score change, dry matter intake, and grazing behavior of autumn calving dairy cows in midlactation. Fifty-two (19 primiparous and 33 multiparous) Holstein-Friesian dairy cows (mean calving date, August 17 ± 91.2 d) were randomly assigned to a 4-treatment (n = 13) randomized block design grazing study. The 4 grazing treatments were: (i) full-time access to pasture (22H; control), (ii) 9-h access to pasture (9H), (iii) two 4.5-h periods of access to pasture after both milkings (2 × 4.5H), and (iv) two 3-h periods of access to pasture after both milkings (2 × 3H). Experimental treatments were imposed from March 7 to April 6, 2007 (31 d). The pregrazing herbage mass of swards offered to all treatments was 1,268 kg of dry matter/ha, and sward organic matter digestibility was 86.4%, indicating high-quality swards conducive to high dry matter intake. Swards where animals had 22H and 2 × 4.5H access to pasture had the lowest postgrazing sward heights (3.5 cm), reflecting the greatest levels of sward utilization. After the experimental period, there were no differences in milk production; however, the 2 × 3H animals tended to have lower milk protein concentration (−0.17%) compared with 22H animals. Furthermore, dry matter intake of the 9H animals was lower than 22H animals. Although restricting access time to pasture decreased grazing time, animals compensated by increasing their intake/minute and intake/bite. Restricting pasture access time resulted in much greater grazing efficiency, because the 9H, 2 × 4.5H, and 2 × 3H treatments spent a greater proportion of their time at pasture grazing (81, 81, and 96%, respectively) than 22H animals (42%). Results of this study indicate that allocating animals restricted access to pasture does not significantly affect milk production. This study also found that the total access time should be greater than 6 h and that perhaps needs to be divided into 2 periods.     

Evaluation of the allergenicity of goat milk, cow milk, and their lactosera in a guinea pig model

The object of this study was to determine the allergenicity of goat milk (GM) and cow milk (CM) and that of their respective lactosera (GML and CML), by in vivo and in vitro assays. Two systemic tests for anaphylaxis were carried out in guinea pigs, the animals being sensitized orally with the 2 types of milk and lactosera. Sera were taken from the orbital sinus of the experimental animals at 0 and 22 d of the experiment to perform the serological study and the passive cutaneous anaphylaxis test. For the latter, the guinea pigs were sensitized passively with antibodies against the 4 antigen solutions. Enzyme-linked immunosorbent assay and Western blot were used to determine the specific antibodies of the isotypes immunoglobulin G1 and immunoglobulin G(Fc) developed against the same 4 antigen solutions. From these anaphylaxis and antibody-production tests, it was concluded that GM is hypoallergenic when compared with CM. The lactosera produced more closely grouped results, with values always below those of the corresponding milk. None of the proteins in the 4 immunizing solutions were identified as being their main allergen. These results show the hypoallergenicity of GM versus CM, and also that both casein and lactoserum proteins may be responsible for allergy in each case. To analyze the possibility of producing an innocuous food for those allergic to milk proteins, it would be of interest to identify the epitope(s) responsible for such allergenicity.     

山羊奶与牛奶和人奶营养成分的比较

对山羊奶、牛奶和人奶中蛋白质、脂肪、维生素、矿物质等主要营养成分进行了比较,分析了3种奶中主要营养成分的差别。通过比较发现,山羊奶在总体营养成分方面优于牛奶,更接近人奶。但山羊奶存在铁、叶酸和维生素B12含量较低以及羊奶膻味的问题,应在营养上对这方面加以重视。     

Effect of rumen-protected methionine on feed intake, milk production, true milk protein concentration, and true milk protein yield, and the factors that influence these effects: A meta-analysis

A meta-analysis of published studies was used to investigate the effect of rumen-protected methionine (RPM) added to the diets of lactating dairy cattle on dry matter intake, milk production, true milk protein (TMP) production, and milk fat yield. Differences in responses between 2 commonly used RPM products, Mepron (Evonik Industries, Hanau, Germany) and Smartamine (Adisseo, Antony, France), were investigated as well as dietary and animal factors that could influence responses. Diets were coded with respect to the amino acid (AA) deficiency of the control diet as predicted by the AminoCow model (version 3.5.2, http://www.makemilknotmanure.com/aminocow.php; 0 = no AA deficiency, 1 = Met deficiency, 2 = Met and Lys deficiency, 3 = Met and Lys plus at least 1 other AA deficiency) to test the effect of AA deficiencies on RPM response. Thirty-five studies were identified, 17 studies evaluating Mepron, 18 studies evaluating Smartamine, and 1 study evaluating both. This permitted 75 dietary comparisons between control and RPM-added diets. Diets were entered into the AminoCow and the 2001 National Research Council models to compare predictions of Met, Lys, and metabolizable protein (MP) flow. Mean Met and Lys in diets where RPM was fed were estimated to be 2.35 and 6.33% of MP, respectively. Predictions of flows between models were similar. Overall, RPM addition to diets increased production of TMP, both as percentage (0.07%) and yield (27 g/d). Dry matter intake and milk fat percentage were slightly decreased, whereas milk production was slightly increased. Differences between products were detected for all production variables, with Mepron-fed cows producing less TMP percentage but greater milk production, resulting in twice as much TMP yield. Milk protein response to RPM was not related to predicted AA deficiency, calculated Met deficiency, or Met as a percentage of MP. Other dietary factors, including Lys flow (g/d), Lys as percentage of MP, neutral detergent fiber percentage, crude protein percentage, or energy balance, had no detectable effects on TMP response. When cows with a predicted positive AA balance were fed RPM, milk production increased, but when AA balance was negative, milk production decreased. Amount of RPM added to the diet was not correlated to TMP response. This study does not support the necessity of a high Lys level as a prerequisite to obtaining a TMP response to feeding RPM or the MP requirement suggested by the National Research Council model (2001). However, more dose-response studies over a wide range of milk production and dietary regimens will be required to more clearly establish AA requirements and to predict responses to RPM supplementation.     

Short-term response in milk production,dry matter intake,and grazing behavior of dairy cows to changes in postgrazing sward height

Postgrazing sward height (PGSH) can be altered to adjust the allowance of grass in the dairy cow’s diet. This study aimed to investigate the short-term dairy cow response to a change in postgrazing height in early lactation. Ninety Holstein Friesian spring-calving cows were randomly assigned across 3 postgrazing height treatments (n = 30): 2.7 cm (severe), 3.5 cm (low), and 4.2 cm (moderate) from February 14 to April 24, 2011. From April 25, animals were rerandomized within each treatment to graze across 2 postgrazing heights: 3.5 cm (low) or 4.5 cm (high). Animal production measurements were taken from April 4 to 24 (measurement period 1; M1) and from April 25 to May 15 (measurement period 2; M2). The 6 treatments (n = 15) of M2 were severe-low, severe-high, low-low, low-high, moderate-low, and moderate-high. During M1, increasing postgrazing height from severe to low to moderate linearly increased daily milk yield (21.5, 24.6 and 25.8 kg/cow per day) and grass dry matter intake (GDMI; 13.2, 14.9, and 15.8 kg of DM/cow per day). Milk solids yield was reduced in the severe (−1,518 g/cow per day) treatment when compared with the low and moderate cows (1,866 g/cow per day, on average). The milk yield (MY) response to change in PGSH between M1 and M2 (V_M1−M2) was established using V_M1−M2 MY = −1.27 − 1.89 × PGSH_M1 + 1.51 × PGSH_M2 (R² = 0.64). The MY response associated with each treatment between M1 and M2 (3 wk) were −1.03 kg/cow for severe-low, 0.68 kg/cow for severe-high, −2.56 kg/cow for low-low, −1.11 kg/cow for low-high, −4.17 kg/cow for moderate-low, and −2.39 kg/cow for moderate-high. The large increase in energy intake in severe-high between M1 and M2 was achieved through higher GDMI per minute and GDMI per bite, which supported the positive change in MY. Treatments low-high, moderate-low, and moderate-high recorded the highest overall cumulative milk yield (74 kg of milk solids/cow) over the 6-wk period, whereas severe-low and severe-high had the lowest (65 kg of MS/cow). From the animal responses observed in the present study, imposing a postgrazing height of 3.5 cm in early spring provides the opportunity to increase postgrazing height thereafter; the cow increases GDMI accordingly and converts the additional energy intake into milk output. The equations established in this paper provide a decision tool for dairy farmers to anticipate the animal response when postgrazing height is altered or maintained around the tenth week of lactation.     

Effect of prepartum anionic supplementation on periparturient feed intake, health, and milk production

Our objectives were to determine if dietary cation-anion difference (DCAD) and source of anions influence periparturient feed intake and milk production of dairy cattle during the transition period. Diets differed in DCAD (cationic or anionic) and anionic supplement. The 4 diets used prepartum were (1) control [DCAD +20 mEq/100 g of dry matter (DM)], (2) Bio-Chlor (DCAD −12 mEq/100 g of DM; Church & Dwight Co. Inc., Princeton, NJ), (3) Fermenten (DCAD −10 mEq/100 g of DM; Church & Dwight Co. Inc.), and (4) salts (DCAD −10 mEq/100 g of DM). Urine pH was lower for cows that consumed an anionic diet prepartum compared with control. Prepartum diet had no effect on prepartum dry matter intake (DMI) of multiparous or primiparous cows. Postpartum DMI and milk yield for multiparous cows fed anionic diets prepartum were greater compared with those fed the control diet. Postpartum DMI and milk yield of primiparous cows were similar for prepartum diets. Feeding prepartum anionic diets did not affect plasma Ca at or near calving. However, cows fed anionic diets began their decline in plasma Ca later than control cows. Postpartum β-hydroxybutyrate and nonesterified fatty acids were lower for primiparous cows fed prepartum anionic diets compared with those fed the control diet. Prepartum and postpartum plasma glucose concentrations were not affected by prepartum diet for all cows. Liver triglyceride differed for parity by day. Parities were similar at 21 d prepartum, but at 0 d and 21 d postpartum, levels were greater for multiparous cows. Results indicate that decreasing the DCAD of the diet during the prepartum period can increase postpartum DMI and milk production of multiparous cows without negatively affecting performance of primiparous cows.     

Production,milk iodine,and nutrient utilization in Jersey cows supplemented with the brown seaweed Ascophyllum nodosum (kelp meal) during the grazing season

Kelp meal (KM) is a supplement made from the brown seaweed Ascophyllum nodosum, known to bioaccumulate iodine (I) and to be the richest source of phlorotannins, which can inhibit ruminal proteolysis and microbial growth. The objective of this study was to investigate the effects of KM on production, milk I, concentrations of blood metabolites, apparent total-tract digestibility of nutrients, and CH₄ emissions in grazing dairy cows. Eight multiparous Jersey cows averaging (mean ± SD) 175 ± 60 d in milk and 12 primiparous Jersey cows averaging 142 ± 47 d in milk at the beginning of the study were assigned to either 0 g/d of KM (control diet, CTRL) or 113 g/d of KM (brown seaweed diet, BSW) in a randomized complete block design. Diets were formulated to yield a 70:30 forage-to-concentrate ratio and consisted of (dry matter basis): 48% cool-season perennial herbage and 52% partial TMR (pTMR). Each experimental period (n = 3) lasted 28 d, with data and sample collection taking place during the last 7 d of each period. Cows had approximately 16.5 h of access to pasture daily. Herbage dry matter intake increased, and total dry matter intake tended to increase in cows fed BSW versus the CTRL diet. Milk yield and concentrations and yields of milk components were not affected by diets. Similarly, blood concentrations of cortisol, glucose, fatty acids, and thyroxine did not change with feeding CTRL or BSW. However, a diet × period interaction was observed for milk I concentration; cows offered the BSW diet had greater milk I concentration during periods 1, 2, and 3, but the largest difference between BSW and CTRL was observed in period 2 (579 vs. 111 µg/L, respectively). Except for period 2, the concentration of milk I in cows fed KM did not exceed the 500 µg/L threshold recommended for human consumption. Diet × period interactions were also found for serum triiodothyronine concentration, total-tract digestibilities of crude protein and acid detergent fiber, CH₄ production, and urinary excretion of purine derivatives. Overall, the lack of KM effects on milk yield and concentrations and yields of milk components indicate that dairy producers should consider costs before making KM supplementation decisions during the grazing season. Future research is needed to evaluate the concentration of I in retail organic milk because of the high prevalence of KM supplementation in northeastern and midwestern US organic dairies and possibly in other regions of the country.     

牛乳的凝固特性及其影响因素研究进展

本文综述了近年来有关牛乳凝固特性的研究进展,重点针对影响牛乳凝固能力的遗传和非遗传因素的研究进展进行了分析论述,包括不同来源牛乳的凝固特性、乳蛋白组分和工艺条件等对牛乳凝固能力的影响。旨在厘清影响牛乳凝固能力的主要因素。