Low-yielding Cows Research Articles

HIGH-MILK PRODUCTIVITY OF HIGH-PRODUCING COWS AND THEIR OFFSPRINGS OF INTERBREED PRECARPATHIAN TYPE OF UKRAINIAN RED-AND-WHITE DAIRY BREED

The studies were conducted on high-producing cows of Precarpathian innerbreed type of Ukrainian Red-and-White Dairy cattle and their progeny, according to zootechnical accounting in private farm enterprise "Mamayivske" in Kytsman district of Chernivtsi region. It was established that during the period from 1995 to 2010 the farm had 20 cows with milk yields over 8000 kg. The highest milk production by the best lactation had cows Maratka 3235, Vorovka 5982 and Chaika 3839, their milk yields were 10586; 9380 and 9008 kgrespectively, fat content in milk – 3.61, 3.79 and 3.77% and fat yield – 382.2, 355.5 and 339.6 kg. The cows had the highest milk yields mostly during the third lactation, and milk yields on average reached record in 3.85 lactations.
 High-yielding cows belonged to 5 bloodlines: R. Sovering 198998, P. Astronaut 1458744, R. Citation 267150, Rigel 352882 and Hanover 1629391. The most numerous one was Astronaut bloodline (11 cows). Daughters of Tyulpan 7451 (R. Sovering bloodline) had the highest level of milk production during the best lactation. They predominated in milk yield during the best lactation over Gybrid’s daughters (Citation bloodline) by 156 kg, T. Tourist’s daughters (Rigel bloodline) by 401 kg, Sekret’s daughters (P. Astronaut bloodline) by 473 kg and M. G. Horizont’s daughters (Hanover bloodline) by 812 kg , by fat yield – by 4.6, 8.6, 9.9 and 26.8 kg, respectively but they were inferior by fat content in milk by 0.02, 0.07, 0.09 and 0.04%. Sekret’s daughters had higher fat content in milk. By this trait, they predominated over Hybrid’s daughters by 0.07, T. Tourist’s daughters – by 0.02 and M. G. Horizont’s daughters – by 0.05%. The average breeding value of bulls, daughters of whom had milk productivity of more than 8000 kg, was +276 kg.
 The highest milk yields were in cows whose mothers belonged to P. Astronaut and Hanover bloodlines and fathers – to R. Sovering bloodline (daughters’ milk yield was 9303 and 9008 kg respectively). High milk yield (8842 kg) also was in cows whose mothers belonged to P. Astronaut bloodline and fathers – to R. Citation bloodline. The best cows by fat content in milk were obtained from a combination of bloodlines V. Ideal – P. Astronaut (3.80%), Rigel – Rigel (3.80%), V. Ideal – Rigel (3.78%) and V. Ideal – Rigel (3.78%).
 Coefficients of repeatability for milk production decreased with increase in period between the comparable lactations. By milk yield for I-VI and the best lactations they were within 0.206-0.495, and by fat content in milk – within 0.337-0.469.
 The better daughters by milk yield not always were obtained from high-yielding cows and, on the contrary, the worse ones – from low-yielding cows. Most cows with high milk yields were from mothers with yields not exceeding 6000 kg of milk, and only with average milk performance of mothers not more than 7281 kg of milk, their daughters predominated in milk yields. With the increase in average productivity of mothers to 8456 kg of milk or more, daughters were inferior to their mothers by1180-3454 kg of milk, but, in all cases, they had a higher milk yield than the average for the herd.
 Positive correlations were found between mothers' milk yield and milk yield, fat content in milk and fat yield of their daughters, but their values partly depended on mothers’ productivity. The highest correlation coefficients between productivity of daughters and mothers were observed at the mothers’ yields not higher than 6999 kg (r = 0.221-0.273), and the lowest – at mothers’ yields over 9,000 kg (r = 0.155-0.182).
 It was found that bull Arbat 1577, estimated on milk production in 69 daughters, had the highest breeding value. The rank of its breeding value was P5 (improver "excellent"). Cows Maratka 3235 (+3204 and +1860 kg), Krona 8490 (+2202 and +1315 kg) Vorovka 5972 (+1710 and +1121 kg), Kava 5450 (+1626 and +1004 kg) Shchoka 5870 (+1602 and +937 kg) had the highest breeding value in terms of best lactation and based on three sources of information, respectively.

Effect of dystocia on subsequent reproductive performance and functional longevity in Holstein cows.

The objective of this study was to evaluate the effect of dystocia on the reproductive performance and functional longevity in Iranian Holsteins. Data consisted of 1467064 lactation records of 581421 Holstein cows from 3083 herds which were collected by the Animal Breeding Center of Iran from April 1987 to February 2014. Reproduction traits in this study included interval from first to second calving, days open and days from first calving to first service. The generalized linear model was used for the statistical analysis of reproductive traits. Survival analysis was performed using the Weibull proportional hazards models to analyse the impact of dystocia on functional longevity. The incidence of dystocia had an adverse effect on the reproductive performance of dairy cows. Therefore, reproductive traits deteriorated along with increase in dystocia score (p<0.05). The culling risk was increased along with increase in the score of dystocia (p<0.0001). The greatest culling risk was observed in primiparous cows, small herds and low-yielding cows (p<0.0001). Also, the lowest culling risk was found for cows calving at the youngest age (<27months), and cows with age at first calving >33months had the greatest risk (p<0.0001). The results of current study indicated that dystocia had important negative effects on the reproductive performance and functional longevity in dairy cows, and it should be avoided as much as possible to provide a good perspective in the scope of economic and animal welfare issues in dairy herds.

A survey of drying-off practices on commercial dairy farms in northern Germany and a comparison to science-based recommendations

While dry cow management is important for health, milk production and fertility information on drying-off procedures implemented on commercial dairy farms is lacking. Current drying-off management procedures on commercial dairy...

Soybean in different forms of processing in the feeding of crossbred cows on brachiaria grass pastures

The objective was to evaluate intake and digestibility of nutrients, as well as milk production and composition of the milk from F1 Holstein × Gyr cows kept on pasture, supplemented with sugarcane and concentrate (28% CP). Five cows with 150±14 lactation days and average milk production of 7.1±2.1 kg/day were distributed in a 5 × 5 Latin square design. The treatments were: soybean meal-based concentrate; soy bean-based concentrate; ground soybean-based concentrate; roasted soybean-based concentrate; and ground, roasted soybean-based concentrate. Dry matter (DM), organic matter, crude protein (CP), neutral detergent fiber (NDF), total carbohydrates and total digestible nutrients intakes were not affected by the diet, but ether extract intake was higher for the animals fed soy bean-based diets than those fed soybean meal. The digestibility of DM, NDF and CP did not differ. The corrected milk yield differed between treatments; animals on the treatment with soy bean-based concentrate had the lowest production in relation to the others, which did not differ from each other. There was no difference between treatments for milk composition. Thus, soybean meal can be replaced by ground soy beans or roasted soy beans (ground or whole) in diets for low-yield cows reared on Brachiaria decumbens pastures with no harm to milkproduction or composition. Therefore, the use of these alternative raw materials is recommended whenever their inclusion represents lower feeding costs.

Maternal aging affects life performance of progeny in a Holstein dairy cow model.

The development and life performance of 404 high-producing Holstein dairy cows was studied from birth onwards and during two lactations. The management, environment and parental genetics of the cows were known in detail. Cluster analysis identified four performance 'types': high-yielding (HY) cows and persistently high-yielding (PHY) cows, which accounted for 33% of the animals; medium-yielding (MY) cows, 41%; and low-yielding (LY) cows, 26%. Prenatal determinants of the life performance of the progeny were analyzed. Developmental and environmental factors were excluded as determinants of performance (including birth weight, level of passive immunity transfer, growth rate, age at first parturition and reproductive efficiency). Life performance did show minor seasonal effects, with more HY cows but less PHY being born during the cold season (90.1% in HY; 58.3% in PHY v. 81.5%). Instead, the single most important factor influencing life performance of daughters was maternal age. HY cows were born from the youngest mothers (1.89±1.14 parturitions, 3.12±1.42-year old), whereas LY cows were born from the oldest (2.72±1.80 parturitions, 3.97±2.01-year old; P<0.001). Life performance of the dams did not differ among clusters. In addition, metabolic parameters (fat and protein yield) were found to correlate significantly with yields between the first and second lactations (milk yield: r=0.357; fat yield: r=0.211; protein yield: r=0.277; P<0.0001), suggesting the influence of the individual. These results suggest that under optimal health, nutritional and environmental conditions, maternal aging is an important determinant of the life performance of progeny and argue for the need to identify conditions that contribute to health and disease in progeny according to the Developmental Origin of Health and Disease or DOHaD concept. Our findings may help the development of novel management guidelines for dairy farms.

Evaluation of dysrhythmias and myocardial biomarkers in high and low-yielding dairy cows

BACKGROUND: Cardiovascular system is a very importantorgan that plays a vital role in tissue function. In farm animals,the growth and high milk production depends on function ofcardiovascular system. OBJECTIVES: Cardiovascular health inhigh and low-yielding dairy cows was investigated. METHODS:Fifty 4-year-old high- yielding Holstein dairy cows and fifty 4-year-old low- yielding Holstein dairy cows were used in thisstudy. Electrocardiogram was recorded by a base- apex lead, andblood samples were collected from the jugular vein for themeasurement of cardiac biomarkers (CK (Creatine Kinase), CKMB(Creatine Kinase-Myocardial Band), LDH (LactateDehydrogenase), and AST (Aspartate Aminotransferase) andtroponin I). RESULTS: Cardiac dysrhythmias were detected morein low- yielding Holstein dairy cows (62%) compared to highyieldingHolstein dairy cows (46%). The cardiac dysrhythmiasthat were observed in low- yielding Holstein dairy cows includedsinus arrhythmia (34.7%), wandering pacemaker (22.45%),sinus bradycardia (18.37%), sinus tachycardia (10.20%), atrialpremature beat (2.04%), sinoatrial block (2.04%), atrialfibrillation (8.16%), and atrial tachycardia (2.04%). The cardiacdysrhythmias were observed in high- yielding Holstein dairycows, including sinus arrhythmia (86.95%) and wandering pacemaker (13.05%). Also, notched P wave was observed in highandlow- yielding Holstein dairy cows, 30% and 14%respectively. The amount of cardiac biomarkers in the lowyielding cows was significantly higher than that of the highyielding cows. Further more, there was not any detectablesignificant difference of serum concentration of total CK betweenthe high and low- yielding Holstein cows. CONCLUSIONS:Despite significant differences in cardiac biomarkers and basedon the normal range of cardiac biomarkers in both groups, theincrease in cardiac dysrhythmias in low- yielding Holstein dairycows may be metabolic and electrolyte disorders.

Measurement of fecal glucocorticoid metabolites and evaluation of udder characteristics to estimate stress after sudden dry-off in dairy cows with different milk yields

Sudden dry-off is an established management practice in the dairy industry. But milk yield has been increasing continuously during the last decades. There is no information whether the dry-off procedure, which often results in swollen and firm udders, causes stress, particularly in high-producing dairy cows. Therefore, we evaluated the effect of a sudden dry-off on extramammary udder pressure and the concentration of fecal glucocorticoid metabolites (i.e., 11,17-dioxoandrostane, 11,17-DOA) as an indirect stress parameter. Measurements were carried out within the last week before dry-off and until 9d after dry-off considering 3 groups of milk yield (i.e., low: <15kg/d, medium: 15–20kg/d, and high: >20kg/d). Udder pressure increased in all yield groups after dry-off, peaked at d 2 after dry-off and decreased afterwards. Pressures were highest in high-yielding cows and lowest in low-yielding cows. But only in high-yielding cows was udder pressure after dry-off higher than before dry-off. Baseline 11,17-DOA concentrations depended on milk yield. They were highest in low-yielding (121.7±33.3ng/g) and lowest in high-yielding cows (71.1±30.0ng/g). After dry-off, 11,17-DOA increased in all yield groups and peaked at d 3. Whereas in medium- and high-yielding cows 11,17-DOA levels differed significantly from their respective baseline during the whole 9-d measuring period, low-yielding cows showed elevated 11,17-DOA levels only on d 3 after dry-off. However, especially the increase in 11,17-DOA after dry-off between the 3 yield groups was considerably different. Mean 11,17-DOA increase from baseline to d 3 was highest in high-yielding cows (129.1%) and considerably lower in low-yielding cows (40.1%). The highest fecal 11,17-DOA concentrations were measured on d 3 after dry-off, indicating that the stress was most intense on d 2, which is due to an 18-h time lag; at about the same time, udder pressure peaked. Our results showed a negligible effect of a sudden dry-off on low-yielding cows. High-yielding cows, however, faced high extramammary pressures and increased glucocorticoid production. Considering animal welfare aspects, a review of the current dry-off strategies might be warranted.

Comparison of different lactation curve models in Sahiwal cows

The present investigation was carried out on 12,859 fortnightly test-day milk yield records of first lactation pertaining to 643 Sahiwal cows spread over a period of 49 years (1961-2009), maintained at the National Dairy Research Institute, Karnal, India. The comparison of 3 lactation curve models, i.e. the quadratic model, gamma-type function, and mixed log function, was done using fortnightly test-day milk yield records. The mixed log function was the best fit, with the highest (88.75%) coefficient of determination (R2 value) and the lowest (0.08 kg) root mean square error (RMSE) value, whereas the lowest (56.93%) R2 value was observed in the quadratic model with maximum (0.15 kg) RMSE value. The closeness of fit of the mixed log function and gamma-type function with the observed lactation curve was almost of the same order. However, the gamma-type function gave a low peak yield, and therefore it is recommended that this function can give the best fit for low-yielding cows.

TRIENNIAL LACTATION SYMPOSIUM: Effects of stress on postpartum reproduction in dairy cows1,2

The objective was to review the effects of production stressors on reproductive performance of dairy cows. It has been well documented that genetic selection for milk yield over the last 50 yr has been associated with reduced fertility. In addition to negative associations between yield and conception rate, there is also an association between milk production and expression of behavioral estrus. Stress caused by production diseases in high-yielding dairy cows also contributes to the problems of poor fertility. Lameness results in reduced intensity of estrus and can contribute to ovulation failure, which is largely due to reduced pre-ovulatory estradiol secretion and failure of the LH surge. Mastitis has been associated with prolonged intervals to dominant follicle selection, and in animals with uterine infection the dominant follicle grows slower and produces less estradiol. In a recent study, we identified that milk yield was associated with an increased incidence of uterine infection, which is known to contribute to reduced fertility and prolonged calving-to-conception intervals. The incidence of uterine disease was 73% in high-yielding, compared with 45% in low-yielding cows. As well as effects at the ovary, various models of stress have also been shown to perturb endocrine secretion in the hypothalamus and anterior pituitary. In conclusion, the adverse effects on fertility associated with genetic selection for yield in dairy cows is, in part, associated with increased incidences of production disease-induced stress but is also associated with high milk yield.

The motivation of high- and low-yielding dairy cows to obtain supplementary concentrate feed

The higher nutrient requirements of lactating dairy cows may cause hunger, and therefore the motivation to consume feed, to increase with milk yield. An experiment was conducted that aimed to establish whether dairy cows could be trained to obtain a food reward in response to lever pressing and, if so, whether high-yielding dairy cows had a greater hunger than low-yielding cows. As a measure of hunger the demand to consume feed was evaluated. In total, 7 high- and 6 low-yielding dairy cows were trained in 2 groups to use a lever to obtain 0.33 kg concentrate rewards. For at least a 9-day period each cow was tested for 30 min/day by increasing the number of lever presses required to receive each additional reward in a progressive ratio of 3. After the test cows were allowed to return to their quarters, where they could consume a total mixed ration (TMR). Initially high-yielding cows had lower maximum number of lever presses than low-yielding cows, possibly so that they could consume TMR after finishing the test, but from Days 6–9 the number for high-yielding cows increased until it was the same as low-yielding cows. There was a positive correlation between the maximum lever presses by high-yielding cows and their time in the test pen, which was not evident for low-yielding cows. The high-yielding cows spent more time feeding on the TMR after the test than low-yielding cows. Therefore, although the high-yielding cows were not prepared to work harder for food rewards, they did seem to adopt a more efficient feeding strategy by only spending time in the test pen if they were still receiving rewards and minimizing time without feed by eating more post-test.

Interrelations Between Glucose-Induced Insulin Response, Metabolic Indicators, and Time of First Ovulation in High-Yielding Dairy Cows

High-yielding dairy cows are more susceptible to metabolic and reproductive disorders than low-yielding cows. Insulin plays a pivotal role in the development of both problems. In the present study, we aimed to assess the glucose-induced insulin responses of dairy cows at different time points relative to calving and to relate this to the metabolic status and the time of first ovulation. Twenty-three healthy, multiparous Holstein-Friesian cows with a high genetic merit for milk yield were studied from 14 d prepartum to 42 d postpartum. Intravenous glucose tolerance tests were performed on −14, 14, and 42 d relative to calving to evaluate the plasma insulin and glucose responses to a glucose load, as estimated by the peak concentration, the area under the curve (AUC), and the clearance rates of insulin and glucose. Blood samples were obtained at 3-d intervals and analyzed for glucose, insulin, and nonesterified fatty acids (NEFA). The time of first ovulation was defined by transrectal ultrasonography and plasma progesterone analysis. Glucose-induced insulin AUC and peak concentration decreased and glucose clearance increased during lactation compared with the dry period. Plasma NEFA concentrations were negatively related to insulin AUC and peak concentrations. Fourteen cows ovulated within 42 d postpartum, and the remaining 9 cows suffered from delayed resumption of ovarian function. Survival analysis demonstrated that cows with lower NEFA concentrations during the dry period tended to have earlier resumption of ovarian activity. In conclusion, our data suggest a decreased plasma insulin response to glucose postpartum in high-yielding dairy cows, possibly contributing to metabolic stress during the early postpartum period. It is hypothesized that NEFA impair glucose-induced insulin secretion in dairy cows. Additionally, our results suggest the importance of lipolysis during the transition period as a risk factor for delayed ovulation.

Influence of space allowance and milk yield level on behaviour, performance and health of dairy cows housed in strawyard and cubicle systems

Two experiments were conducted to study the effects of two space allowances and two initial milk yield levels on indicators of welfare relating to behaviour, performance and health of dairy cows housed in strawyards (experiment 1), and cubicles (experiment 2). The experiments were carried out with 24 and 32 Holstein Friesian cows, respectively, and had changeover designs each with two periods of 4 weeks, and two replicates of six and eight cows in each treatment. The respective total and bed space allowances per cow for strawyards were, 13.5 and 9.0 m 2 for high, and 6.7 and 4.5 m 2 for low space allowance. For cubicles, respective allowances per cow were 10.6 and 3.9 m 2 for high and 7.75 and 2.3 m 2 for low. Space allowance had no significant effect on milk production, liveweight change, condition score, feed intake or on total time spent feeding and lying. In strawyards, cows were dirtier ( P<0.01) at the low space allowance and milk lactose levels were lower ( P<0.01), indicating some prevalence of mastitis. In cubicles, agonistic interactions were greater ( P<0.001) at the low space allowance and the diurnal pattern of lying was disrupted, especially for high yielding cows. High milk yield cows in strawyards had lower lying times ( P<0.001) and lying synchrony ( P<0.01) than low yielding cows. Higher feed intakes of high yielding cows ( P<0.001) resulted in higher ruminating times ( P<0.001) in both experiments and higher feeding times in experiment 1 ( P<0.001) than for low yielding cows. It is concluded that for strawyards, cleanliness of the cows is a key welfare indicator, and can be controlled by management of the straw beds. Total lying time and lying synchrony are also key factors of welfare, and have particular relevance for cubicle systems where lower values were recorded. High yield dairy cows had a shorter lying time than low yield cows, and there was no evidence that high and low yield cows respond differently to changes in space allowance, indicating that their housing requirements are similar.

Mammary secretion of oestrogens in the cow

Two experiments in vivo and one experiment in vitro were conduced to examine the mechanisms involved, which lead to mammary secretion of oestrogens and its importance for milk production and udder health in cows. In experiment 1 in six cows of the White–Black breed on day 268 of pregnancy catheters were inserted into uterine vein of pregnant horn, the abdominal aorta and the caudal superficial epigastric (milk) vein. Blood samples for estimation of oestrone, oestrone sulphate, oestradiol-17α and -17β by RIA were obtained daily from day 7 pre-partum until day 1 post-partum. Only the concentration of oestradiol-17β was statistically higher ( P≤0.01) in mammary venous plasma than in aortal and uterine plasma. In experiment 2 forty late-pregnant cows were divided into two groups according to their milk production in the previous lactation: group 1 ( n=20) high-yielding cows (>6500 kg milk per lactation), and group 2 ( n=20) low-yielding cows (<3700 kg milk per lactation). Blood samples for measurement of oestradiol-17β by RIA were collected from milk and tail veins every fourth day during a period from day 20 prior to parturition to day 4 post-partum. The concentration of oestradiol-17β was significantly higher ( P≤0.01) in the milk vein than in the peripheral plasma from day 12 pre-partum to parturition. In high-yielding cows the level of oestradiol-17β in mammary venous blood was significantly higher ( P≤0.01) than in low-yielding cows. In six cows with pathological udder oedema ante-partum the concentration of oestradiol-17β in milk vein was significantly higher ( P≤0.05) than in control cows. There were no statistically significant differences in the levels of oestradiol-17β in cows with clinical mastitis ( n=10) during 2 weeks after parturition and without it ( P≥0.05). In an in vitro experiment, homogenates of mammary tissue collected on day 7 pre-partum from two cows were incubated with 3 H -androstendione. After incubation the samples were extracted and 3 H -oestradiol-17β was separated by HPLC. 3 H -oestradiol-17β was formed in a total yield of 37%. These results indicate that oestrone, oestrone sulphate and oestradiol-17α are not secreted by bovine mammary gland. Furthermore, the secretion of oestradiol-17β starts about day 12 pre-partum and is associated with milk yield and udder oedema. Preliminary in vitro study suggests the synthesis of oestradiol-17β by mammary tissue.

Behaviour, performance and health indicators of welfare for dairy cows housed in strawyard or cubicle systems

Objective methods are required to assess the welfare of livestock in different environments. Two experiments were conducted to determine comparative indicators of welfare in the two most common loose-housing systems for dairy cows, strawyards and cubicles. Experiment I examined the animal responses to the two housing systems with 16 high- and 16 low-yielding Holstein Friesian cows in a changeover design over two, 4-week periods. Experiment II was carried out over 17 weeks to assess the longer-term responses to the two systems with 24 Holstein Friesian cows. In experiment I cows in the strawyard system had a significantly greater lying time, ruminating time and synchronisation of lying behaviour than the cubicle system. The cows were significantly cleaner in the cubicle system but there were no significant differences between systems in milk production, cell count or locomotion score. High yield cows had a shorter lying time but longer feeding time than low yield cows. The cows of different milk yield level responded similarly to the housing systems, indicating that cows of high milk yield do not require different housing systems from low yield cows. In experiment II there were no significant differences between housing systems in lying, ruminating or synchronisation of lying behaviour. Milk yields were significantly lower in the strawyard than in the cubicle system due to a significantly higher incidence of clinical mastitis. Cell-counts were significantly lower and cows were significantly cleaner in cubicles. There were no significant effects of housing system on hoof dimensions, locomotion score or clinical lameness. It was concluded that total lying time, lying synchrony, milk cell count and locomotion score are potential indicators for the assessment of dairy cow welfare in different housing environments.

Sahiwal cattle in Pakistan: genetic and environmental causes of variation in body weight and reproduction and their relationship to milk production

AbstractThe influence of genetic and environmental factors on body weight and reproduction and their relationship to milk production traits, were studied in data of about 4700 Sahiwal cows from Pakistan. (Co)variance components were estimated using restricted maximum likelihood (REML) procedure based on the expectation maximization algorithm applying an animal model. Mean weights of females were: at birth, 21·6 kg; at 1 year, 130 kg; and at 2 years, 222 kg. Records of age at calving, cow weight post partum and calving interval were studied in the first three parities, with parities considered as different traits. For primiparous cows the average values of these traits were: 44·1 months, 319 kg and 465 days, respectively. Mean stillbirth rate was 5·3%. Heritabilities ranged for body weight traits from 0·08 to 0·21, for age at calving from 0·10 to 0·13 and for calving interval from 0·03 to 0·07. Genetic correlations of age at first calving with calving interval and 305-day milk yield were low. The genetic correlation between 305-day milk yield and calving interval was positive (unfavourable) in first parity (0·68) but negative in the third (-0·47). Cows with a high genetic value for 305-day milk yield were heavier at first calving than were low-yielding cows (rg 0·57). The genetic change in reproductive traits over the period studied was close to zero, whereas a marked deterioration was found in phenotypic performance. It is concluded that improved feeding and management, along with some selection against poor reproduction in cows, are important for improvement of reproductive performance.

Field evidence of metabolic stress in dairy cows?

AbstractThe authors review their experiences of metabolic profiles in dairy herds, with a view to assessing whether metabolic stress is a problem in Great Britain at present. Many cows show elevated blood beta-hydroxybutyrate concentration, indicating energy deficit, or elevated urea levels, indicating an imbalance between energy and protein in the rumen but at present there is no evidence that high-yielding cows in commercial herds show more metabolic stress than low-yielding cows. The authors suggest that more cows could suffer metabolic stress in the future, unless farmers’ ability to feed and manage dairy cows develops as rapidly as genetic selection for high milk yield.

Technical and Economic Effects of Culling and Reproduction Strategies in Dairy Cattle Herds Estimated by Stochastic Simulation

Abstract The objective of this study was to create operational replacement guidelines under various conditions concerning reproductive performance, supply of replacement heifers and individual milk yield. Nine culling strategies were defined by three average insemination periods and by three discrimination policies between high- and low-yield cows. The effect of the nine culling strategies was analysed with combinations of heat detection rate and time of initiation of breeding after calving under two replacement heifer purchase policies: purchase (open herd) and no purchase (closed herd). The strategies were evaluated using a stochastic simulation model that simulated production and reproductive status in herds composed of dual-purpose cattle with additional young stock. The evaluation of the strategies was made in a situation without a milk quota under typical Danish conditions in 1993. Results showed that discriminating between high- and low-yield cows improved net revenue significantly in open herds bu...

The secretion and metabolic clearance rates of growth hormone, insulin and prolactin in high- and low-yielding cattle at four stages of lactation

The basal plasma concentration, secretion rate (SR), distribution space (DS) and metabolic clearance rate (MCR) of GH, insulin and prolactin were measured in groups of 4 high- (HY) and 4 low-yielding (LY) cows at around 30, 90 and 150 days of lactation and after the cattle had been dried off. The kinetic parameters were determined using the single injection technique and measuring the disappearance of each hormone from the plasma by radioimmunoassay. Throughout lactation the DS for GH was higher in the HY cows (P<0.01) falling significantly in both groups when they were dry (HY, P<0.001; LY, P<0.01). There was no difference between the lactating group in the MCR of GH, but in both there was a significant (P<0.001) drop in the dry period which was accompanied by a fall in the SR (P<0.05). No differences were found in the DS and MCR of insulin between the groups during lactation but the average SR of insulin in the LY group was more than twice that in the HY group (P<0.05). Overall differences between stages of lactation were found in both groups for the SR (P<0.05), DS (P<0.01) and MCR (P<0.001) of insulin. None of the kinetic parameters differed for prolactin in the two groups. The DS (P<0.05) and MCR (P<0.001) of prolactin increased from day 30 to day 150 of lactation in both groups and then fell significantly (DS, P<0.05; MCR, P<0.01) when the animals were dry. In both groups the SR (P<0.01) and basal plasma concentration (P<0.01) of prolactin were higher in the dry period than at 30 and 90 days of lactation; probably due to the influence of season on the hormone.

The effect of level and frequency of concentrate feeding on the performance of dairy cows of different yield potential

SUMMARYAn experiment has been made using adult lactating cows in a randomized block design to study the effectiveness of basing feeding during the first 20 weeks of lactation on yield predicted from that obtained during the 8–12th days of lactation. Cows were classified as high yielding (HY) or low yielding (LY). The levels of feeding were identical within each yield group during the first 8 weeks of lactation but during the 9th to the 20th week two different levels of concentrate feed (HP and LP) were used. Over the 20-week period concentrates were offered in two or five daily feeds. Thus the effect of two levels and two frequencies of feeding on feed intake, milk yield and composition, and on live-weight change were studied.Cows in the HY group achieved a mean daily peak yield 2·6 kg higher than predicted while those in the LY group achieved the predicted mean peak daily yield. There was no significant effect of level of feeding on the 20-week milk yield but there was a significant effect on the yield of the LYLP class in weeks 9–20. Frequency of feeding had no significant effect on yield in either high-low-yielding cows. There was no significant effect of level of feeding on milk composition but low-yielding cows gave milk with a higher fat percentage than high-yielding cows. Five-times-a-day feeding also produced milk with a higher fat percentage than twice-a-day feeding.Live-weight changes were small and the largest variation was recorded in highyielding cows.The number of days from calving to first service was not significantly different for the two yield groups but there was a significant effect of level of feeding.

Endocrine Control of Energy Metabolism in the Cow: Correlations of Hormones and Metabolites in High and Low Yielding Cows for Stages of Lactation

Measures of hormones and metabolites in blood plasma of high and low yielding cattle matched for diet and stage of lactation were investigated for relationships between milk yield, body weight, and concentrations of hormones (prolactin, growth hormone, insulin, and thyroxine) and metabolites (glucose, nonesterified fatty acids, β-hydroxybutyric acid, and L-lactic acid) for stages of lactation. A first approach correlated total milk yields of 15 cows with average constituents during the four 24-h blood samplings through the first 27 wk of lactation. The second examined associations of changes with sampling periods in milk yield or body weight with changes in hormones and metabolites.Total milk yield of the high yielding group was correlated positively with ratios of growth hormone/thyroxine and glucose/thyroxine and correlated negatively with thyroxine.Changes in growth hormone and its ratio to insulin, and changes in yield were correlated positively for groups combined. Changes in thyroxine were correlated negatively with changes in yield. Changes in liveweight gain were related positively to insulin and lactic acid and negatively with changes in growth hormone. Changes in growth hormone were related positively to changes in nonesterified fatty acids.