Study on some risk factors and effects of bovine ketosis on dairy cows from the Galicia region (Spain).

The study was designed to determine the relation between ß-hydroxybutyrate (BHB) concentrations in milk from dairy cows after calving and the length of the previous lactation, the dry period and the 305-day normalized production, and to assess the influence of BHB concentrations on culling and test-day milk productions and somatic cell counts (SCC) throughout the lactation that followed the BHB measurement. The data used in the study were obtained from 59 187 cows in the Galicia region (Spain). BHB determination was performed using Fourier-transformed infrared spectrometry from the milk samples collected from each cow on the first post-partum test day. For statistical analysis, the following methods were applied: (i) ordinal regression to assess the effect of the length of the previous lactation, the dry period and the 305-day normalized milk production on milk BHB, (ii) a Cox model to estimate the influence of the BHB concentration on risk of culling (overall and for a variety of reasons) and (iii) linear regression to assess the link between BHB and the milk yield and SCC obtained from each of the tests day performed throughout lactation. The probability of having higher BHB concentrations increased when the length of the previous lactation (p = 0.006), the dry period (p = 0.003) and the 305-day normalized milk yield (p = 0.005) increased. However, the slight increase observed (especially for the case of the dry period and the 305-day milk yield) would not justify that measures be implemented to reduce these traits. Higher concentrations of BHB led to an increased risk of culling due to 'death' (p ≤ 0.001) and 'urgent slaughter' (p ≤ 0.002) (both causes of involuntary culling). It also led to a reduction in milk production (p < 0.001) and an increase in SCC (p < 0.001) in the post-partum; from that moment onward (including peak lactation), there were no differences in those two parameters depending on the BHB levels.

Effect of the sampling device on fat and protein variation in cow milk samples obtained for official milk recording.

The paper was designed to assess the effect of the type of milk meter used by dairy farms for official milk testing to obtain individual milk samples for fat and protein determination. This study was performed in 2006 in Galicia, which is Spain's main dairy cattle region; data were collected from 2,149 Holstein cow farms enrolled for official milk recording. Findings indicate that the milk sampling system used has a substantial effect on the fat contents recorded for individual milk samples. Such variation could arise from poor functioning of the equipment, inadequate mixing of the milk portion from which the sample is obtained, or from the nonproportionality of the sample. Samples obtained from only one point in the milk line may not be representative of all the milk produced. The most significant differences are observed in the percentage of fat, whereas differences in percentage of protein are smaller. The sampling method used should, but does not always, provide a representative sample of the milk from a single milking.

Robot milking and relationship with culling rate in dairy cows.

Cow routines and behavioral responses are altered substantially following the installation of robot milking. The present study was designed to analyze the effect that switching from milking parlor to automatic milking system (AMS) had on the culling rate (due to various causes) of dairy cattle. For this purpose, culling records and causes for culling were tracked in 23 dairy farms in the Galicia region (NW Spain). The animals in these farms were monitored for 5 years. For the present study, that length of time was divided into three different stages, as follows: 2 years before switching from a milking parlor to AMS (stage 1), the 1st year following the implementation of AMS (stage 2) and the 2nd and 3rd years succeeding the implementation of AMS (stage 3). Cox models for survival analysis were used to estimate the time to culling due to different reasons during stage 1 in relation to stages 2 and 3. The data indicated that the risk of loss due to death or emergency slaughter decreased significantly following the installation of AMS. In contrast, the risk of culling due to low production, udder problems, infertility or lameness increased significantly. Low-production cows (such as cows in advanced lactation due to infertility) or sick cows (such as mastitic or lame cows) allegedly have a noticeable effect both on the performance and the amortization of the cost of AMS, which in turn would lead to a higher probability of elimination than in conventional systems.

Chemometric authentication of the organic status of milk on the basis of trace element content.

The objective of this study was to develop a method for authenticating organic milk samples in North Spain on the basis of its trace mineral composition. Fourteen elements in 98 samples were determined by inductively coupled plasma mass spectrometry. Although concentrations of Co, Cr, Cu, I, Se and Zn where statistically higher in conventional milk and As in organic, none of these elements by itself was able to discriminate between organic and conventional milk. The chemical data was examined by principal component analysis and cluster analysis, revealing a natural separation between organic and conventional milk. In a second step, several supervised pattern recognition techniques were used to construct mathematical models for predicting the type of milk (organic or conventional) based on the metal content. The results proved that the model constructed using the artificial neural network is capable of correctly identifying the type of milk in almost 95% of cases.

The use of crossbreeding with beef bulls in dairy herds: effects on calving difficulty and gestation length.

This study was designed to analyse the evolution in the use of beef bull semen for dairy cattle insemination and, mainly, to assess calving difficulty, gestation length and proportion of stillbirths after breeding pure Holsteins or crossbreeding. Data were collected during 2004 to 2011 for 552 571 Holstein calvings (457 070 Holstein × Holstein, 43 384 Holstein × Limousine, 32 174 Holstein × Belgian Blue and 19 943 Holstein × Galician Blonde). The highest calving difficulty, compared with pure Holsteins was for crosses with Belgian Blue followed by Limousine and Galician Blonde. The Holstein × Limousine and Holstein × Galician Blonde crossbred calves had significantly longer gestation lengths than Holstein × Holstein and Holstein × Belgian Blue calves. Between the latter two, pure Holstein had the shortest gestation length. Calving difficulty and gestation length decreased as the age of the dam advanced. The most difficult calvings were observed in twin calvings, followed by the calvings of male calves and female calves. The gestations leading to the birth of male calves were longer than those leading to female calves and twin calves. Stillbirths were not related to the breed used for mating. Through examining these parameters, sire breed should be considered when selecting a beef breed for the insemination of milk-producing dams.