Analysis Of Milk Yield Research Articles

Mendelian randomization analysis of 34,497 German Holstein cows to infer causal associations between milk production and health traits

BackgroundClaw diseases and mastitis represent the most important health issues in dairy cattle with a frequently mentioned connection to milk production. Although many studies have aimed at investigating this connection in more detail by estimating genetic correlations, they do not provide information about causality. An alternative is to carry out Mendelian randomization (MR) studies using genetic variants to investigate the effect of an exposure on an outcome trait mediated by genetic variants. No study has yet investigated the causal association of milk yield (MY) with health traits in dairy cattle. Hence, we performed a MR analysis of MY and seven health traits using imputed whole-genome sequence data from 34,497 German Holstein cows. We applied a method that uses summary statistics and removes horizontal pleiotropic variants (having an effect on both traits), which improves the power and unbiasedness of MR studies. In addition, genetic correlations between MY and each health trait were estimated to compare them with the estimates of causal effects that we expected.ResultsAll genetic correlations between MY and each health trait were negative, ranging from − 0.303 (mastitis) to − 0.019 (digital dermatitis), which indicates a reduced health status as MY increases. The only non-significant correlation was between MY and digital dermatitis. In addition, each causal association was negative, ranging from − 0.131 (mastitis) to − 0.034 (laminitis), but the number of significant associations was reduced to five nominal and two experiment-wide significant results. The latter were between MY and mastitis and between MY and digital phlegmon. Horizontal pleiotropic variants were identified for mastitis, digital dermatitis and digital phlegmon. They were located within or nearby variants that were previously reported to have a horizontal pleiotropic effect, e.g., on milk production and somatic cell count.ConclusionsOur results confirm the known negative genetic connection between health traits and MY in dairy cattle. In addition, they provide new information about causality, which for example points to the negative energy balance mediating the connection between these traits. This knowledge helps to better understand whether the negative genetic correlation is based on pleiotropy, linkage between causal variants for both trait complexes, or indeed on a causal association.

Milk characteristics and milking efficiency in Italian Mediterranean buffalo

The study aimed to verify the influence of different milking machine setting parameters on Italian Mediterranean buffalo milking performance. Data on milking machine settings (Milking Dry Tests [MDTs]) and milk Test-day (TD) were collected by the Italian Breeders Association (AIA). Data for each TD consisted of milk yield (MY), fat percentage (FP), protein percentage (PP), lactose percentage (LP) and linear score (LS). Working vacuum level (VL), pulsation ratio (PR), automatic cluster removal system (AC) and effective vacuum reserve (EVR) were recorded from each MDT. A total of 558 MDTs, 217,967 TD, collected from 43,593 buffaloes in 198 buffalo farms were utilised. MDT, TD and Animal data (AD) were analysed through a mixed linear model and a logistic regression model was used to evaluate the relationship between VL and EVR. Analysis of MY and quality revealed that an incorrect setting of the milking was responsible for a higher LS and lower MY and LP, along with higher FP and PP compared to farms with adequate EVR. Except for PP, the height of the milking system significantly influenced all milk parameters. Conversely, VL affected all milking traits. A higher PR (70:30) was responsible for significantly lower LS and higher FP compared to a 60:40 PR. Similarly, the presence of AC showed a significant effect on FP and MY and a slight reduction in LS. Finally, the diameter and length of the pipeline (DL) ratio lower than 2.5 m was associated with a decrease in LS. These results suggest that buffaloes require specific milking parameters.

Estimation of lactation curves of Gyr cattle and some associated production parameters in the Colombian low tropic

Background: The Gyr breed is widely used in Colombian low tropic dairy production systems. During the last 10 years, the Asociación Colombiana de Criadores de Ganado Cebú† - ASOCEBU, has been leading a dairy milk control program which led to the creation of a dataset that permits to carry out the first analysis of milk yield in Gyr cattle in the country using records from several herds. Objectives: To study milk production dynamics of Gyr cattle in the Colombian low tropic through the estimation of lactation curves and four derived production parameters: total milk yield between 5 and 305 days (TMY305), peak milk yield (PMY), days at peak (DP) and persistency (P). Methods: 13,798 daily milk yield records from 1,510 cows performing in 103 herds were used; the total number of lactations was 2,480. Four models were considered: Wood, Wiltmink, Papajcsik & Bordero, and a second-degree polynomial. Mean square error, mean absolute error, mean square error of prediction, Akaike and Bayesian information criteria were used to select the model better describing each lactation using the majority rule, that is, the model selected by most criteria was the chosen one. The shape of each fitted lactation curve was checked using basic results from calculus which permitted the classification of the estimated curves into two groups: typical and atypical; only typical functions were used to compute the four aforementioned production parameters. Results: The second-order polynomial was the model most frequently selected, while the Papajcsik & Bordero model had the lowest frequency. Average TMY305, PMY, DP and P were 3,489.86 kg, 17.28 kg, 57.17 days, and 0.83, respectively, with coefficients of variation: 0.27, 0.21, 0.41, and 0.16. Conclusions: This study permitted to identify individuals with outstanding phenotypic performance. To the best of our knowledge, this is the first study of this kind involving thousands of lactations from Gyr cows performing in several regions of Colombian low tropic.

Herb species inclusion in grazing swards for dairy cows—A systematic review and meta-analysis

A systematic review and meta-analysis were conducted to estimate the effect of herb species on milk production and urinary nitrogen (UN) excretion from grazing dairy cows. Grazing swards consisting of herb species grown with either a grass species or a grass and legume (multispecies swards) were compared with non-herb-containing swards consisting of a grass species grown as a monoculture or grass-legume swards (simple swards). A literature search was completed using the online databases CAB Direct, Web of Science, and Google Scholar, using the search strategy "dairy cow", "herb OR forb OR phorb", and "grazing". Milk production data, variance, and sample size were required for eligibility. In all, 116 studies were identified. Following eligibility screening, 11 papers from 6 journals, published between 2006 and 2018, were available for analysis. Studies were from New Zealand (N = 7), Australia (N = 3), and the United States (N = 1). The population was either Holstein Friesian or Holstein Friesian × Jersey dairy cows, with a range in mean daily milk yield (MY) from 12.1 kg to 34.7 kg (mean = 18.6 kg). A total of 25 comparisons were used for milk production analysis, with 324 and 284 cows included in multispecies and simple sward groups respectively. Data analysis was conducted in R using a random effects, robust variance estimation model (R Foundation for Statistical Computing, Vienna, Austria). Heterogeneity was reported using the I2 statistic. Milk production was significantly increased. Analysis of MY resulted in a weighted mean difference (WMD) of +1.20 kg/d (95% CI = 0.90, 1.49; I2 = 4%). Fat and protein kg were also significantly increased (WMD +0.06 kg/d; CI = 0.01, 0.11). Urinary nitrogen excretion was estimated from milk urea nitrogen when reported (n = 6). A WMD of -28.1 g of N/d (95% CI = -81.1, 24.9) was generated, with heterogeneity high among studies (I2 = 75%). This meta-analysis shows the potential benefits of multispecies swards. Although we saw no significant difference in UN excretion, an increase in milk production was found.

Prediction possibility of milk yield from udder measurements using digital image analysis on holstein cows

A photographic survey of 43 multiparous lactating cows was carried out by recording the images between morning and evening milking time (around noon time) using digital camera from posterior angle. Images were then processed using Image Tools V.3.00 software to determine Udder measurements (UMs) of cows from the images in centimetres. The linear parameters recorded were rear udder depth (UD), rear udder width (UW) and rear udder area (UA). Regression analysis of milk yield on each of the independent variables was performed. Regression coefficients, for all UMs, taken together were 65.5%. The single regression coefficients were 23.0, 0.2 and 61.0for UD, UW and UA, respectively. The correlation coefficients between milk yield and UD, UW and UA were 0.48 (P >0.05), 0.04 (P >0.05) and 0.78 (P <0.05), respectively. The results showed that, the milk yieldof cows could be predicted using digital image, using udder area as a parameter. However, the prediction possibility was higher when all UMs were used.

Genetic analysis of milk yield, fat and protein content in Holstein dairy cows in Iran: Legendre

Abstract. Data including 219 105 test day records of 22 569 first parity Holstein cows in 56 herds were analysed for milk yield, fat content and protein content. Legendre polynomials were used in a random regression model to explain traits curves, additive genetic and permanent environmental effects along days in milk (DIM). Legendre polynomials of order 3 were used to describe additive genetic effects on the traits. For permanent environmental effects, for milk the order of 6 and for fat and protein content the order of 4 were used. Heterogeneity of residual variance was considered. Restricted maximum likelihood (REML) methodology was used to estimate the required parameters. Variations in genetic, permanent environment and residual effects and heritability changes along DIM were computed and illustrated. Daily heritability estimates averaged as 0.22, 0.14 and 0.23 for milk, fat and protein contents, respectively. Minimum correlations between DIM for additive genetic effects were as 0.49, −0.01 and 0.34 for milk, fat and protein contents. There were higher genetic correlations between test day milk yield and protein content compared to fat content. The genetic trend of milk yield has increased over the years from 1971 to 2005, while the genetic trend for fat and protein content declined.

Bayesian genetic analysis of milk yield in Tunisian Holstein dairy cattle population

The genetic determinism of 305-d milk yield and its genetic parameters were investigated in Tunisian Holstein dairy cattle population through Bayesian segregation analyses using a Monte Carlo Markov Chains (MCMC) method. Data included 49,709 records of 305-d milk yield collected between 1996 and 2003 from 114 dairy herds. The postulated major gene was assumed to be additive biallelic locus with Mendelian transmission probabilities and priors used for variance components were uniform. Gibbs sampling was used to generate a chain of 500,000 samples, which were used to obtain posterior means of genetic parameters. Estimated marginal posterior means ± posterior standard deviations of variance components of milk yield were 402866.28 ± 23629.97, 271256.66 ± 34477.83, 68276.83 ± 233027.62 and 1098855.75 ± 10009.52 for polygenic variance (σ2u), permanent environmental variance (σ2ne), major gene variance (σ2G) and error variance (σ2e), respectively. The main finding of this paper showed the postulated major locus was not significant, since the 95% highest posterior density regions (HPDs95%) of most major gene parameters included 0, and particularly for the major gene variance. Estimated transmission probabilities for the 95% highest posterior density regions (HPDs95%) were overlapped. Genetic parameters of 305-d milk yield were very similar under both mixed inheritance and polygenic models. These results indicated that the genetic determinism of milk yield in Tunisian Holstein dairy cattle population is purely polygenic. Based on 50,000 Gibbs samples, heritability and repeatability estimates using polygenic model were h2 = 0.22 ± 0.012 and r = 0.38 ± 0.006, respectively.

Short communication: Analysis of milk yield and composition for dairy heifers limit-fed lower forage diets during the rearing period

Methods to improve feed efficiency in dairy heifers have been studied that employ limit feeding and high concentrate or highly digestible diet ingredients. To date, the published studies have used differing daily gains, diet components, and management systems. All of these studies have had limited numbers of animals, which limits the power of each study by itself. The objective of this analysis was to evaluate, using all available studies, the overall effect of limit feeding dairy heifers during the rearing phase on milk production and composition during the first lactation. To accomplish this objective, responses from published experiments were analyzed using random effects meta-analytic procedures. The results of this analysis confirmed the results of the individual experiments in that no significant differences were found in lactation performance between the limit-fed, lower forage diets and the higher forage control diets. Heterogeneity of results between experiments was low to moderate for the response variables evaluated, indicating that the results were reasonably consistent among the trials. Limit feeding of higher concentrate diets represents a viable alternative to traditional high forage heifer feeding systems when environmental or economic conditions favor these systems.

Comparative analysis of milk yield and reproductive traits of Holstein-Friesian cows born in Turkey or imported from Italy and kept on farms under the Turkish-ANAFI project

This research investigated the milk yield, reproductive traits and productive life of Holstein-Friesian cows born in Turkey or imported from Italy and raised on farms involved in the Turkish-ANAFI Project. A total of 2600 records for age at first calving, 4733 completed lactation records from 2080 cows, and 1130 productive life (from first calving to disposal) records from 50 farms in the provinces of İzmir, Manisa and Aydın under the Turkish-ANAFI Project were evaluated. Least squares means for age at first calving, 305-day milk yield, lactation milk yield, lactation duration, days open, days dry, and productive life were 28.2 months, 6232 kg, 6829 kg, 336.0 days, 138.0 days, 78.3 days, and 28.9 months, respectively. Corresponding least squares means for cows born in Turkey and imported from Italy were 28.8 and 27.6 months (P<0.01), 6182 and 6281 kg (P>0.05), 6761 and 6897 kg (P<0.05), 333.9 and 338.1 days (P<0.05), 132.7 and 143.4 days (P<0.01), 79.2 and 77.3 days (P>0.10), and 21.6 and 36.1 months (P<0.01), respectively. The level of milk yield of Holstein-Friesian cows in herd-book herds under the project in the Aegean Region was satisfactory. However, there were reproductive problems as shown by the length of days open. Shorter productive life of cows born in Turkey compared to cows from Italy suggested that breeders tended to cull locally born cows at a younger age but that they tended to keep imported cows in the herd for a longer period unless serious problems occurred.

The effect of formalin-treated soya bean meal upon the performance of lactating cows

ABSTRACTFour concentrate mixtures were given with grass silage to 52 cows in early lactation in an 8-week randomized block production trial. A further eight cows were used to measure apparent digestibilities of the total diets in a double 4 × 4 Latin-square trial.The concentrates contained varied proportions of barley, soya bean meal (soya) and formaldehyde-treated soya bean meal (treated soya) together with fixed proportions of wheatfeed and molasses. Crude protein (CP) concentrations in the concentrate mixtures and sources of supplementary protein were 133 g/kg air-dry concentrate, soya (A); 130 g/kg, treated soya (B); 187 g/kg, soya (C); 169 g/kg, soya plus treated soya (D). In the production trial, 9 kg concentrates were given daily together with silage ad libitum, whilst in the digestibility trial the daily ration was 7·6 kg concentrates and 6·6 kg silage dry matter (DM). The silage contained 462 g DM per kg and 140 g CP per kg DM with an in vitro digestibility of DM of 0·7.The digestibilities of DM, organic matter and energy showed similar trends. Cows given treatments A and B had significantly lower digestibilities of energy than did those given treatments C and D.Nitrogen digestibility was highest for cows given treatment C and lowest for those given treatments A and B. Silage DM intake and live-weight change were unaffected by treatment during weeks 1 to 8, all treatment groups being in positive live-weight balance in this period.Milk yields during weeks 1 to 8 were 18·8 (A), 19·6 (B), 20·3 (C) and 20·7 (D) kg/day. Yields for cows given treatments C and D were significantly higher than those for cows given treatment A. There were no differences between treatments for any constituent of milk, but protein concentration in milk tended to be lower for cows given treatment D. During weeks 9 to 20, there were no significant residual effects of treatment upon milk yield or composition.Parallel regression analysis of milk yield and yields of milk constituents upon CP concentration in the concentrate indicated significant effects of CP concentration on yield of milk, milk fat, protein and lactose during weeks 1 to 8. When examined during weeks 1 to 20 the responses to increased CP concentration were non-significant. The analysis showed a significant positive milk-yield response to formaldehyde treatment during weeks 1 to 8 and 1 to 20. The response in lactose yield was also significant during weeks 1 to 8 and 1 to 20. There was a trend, though not significant, towards an increased milk-fat yield during weeks 1 to 8 for the formaldehyde treatment, whilst protein yield was unaffected.