Causes of culling in dairy cows and its relation to age at culling and interval from calving in Shiraz, Southern Iran

This study was designed to investigate causes of culling in industrial dairy herds in Fars province and to describe the pattern of reason-specific culling with respect to age of animal and interval from calving to culling. A total number of 9 dairy herds were selected for the study and information about culling reasons, birth date, last calving date and culling date was collected for culled cows during 2005- 2006. Infertility (32.6% of all culls) was the most prevalent reason of culling followed by mastitis (6.5%). The time interval from last calving to culling averaged 240 days (SD = 176) and nearly 28% of cows were culled in the first 100 days after calving. Mean age of animals at culling was 6 years (SD = 2.7) and median was 5.7 years. In Cox proportional hazard model for calving to culling interval, infertility (hazard ratio [HR] = 0.26) showed lower risk whereas mastitis (HR = 2.40), left displaced abomasum (HR = 2.60) and peripartum problems (HR = 2.60) had higher risk of culling compared with voluntary cull. In the Cox model for age at culling, risk of culling was significantly higher for infertility (HR = 1.70), left displaced abomasum (HR = 3.15), and peripartum problems (HR = 2.10) compared with voluntary culling. In conclusion, farmers tend to keep infertile cows for longer period from calving to culling while infertile cows are generally culled at younger age. Also, early culling appeared to have a high proportion of culls in the studied herds

Circulating Thyroid Hormones and Indices of Energy and Lipid Metabolism in Normal and Hormonally Induced Oestrus Cows

In a field study, circulating thyroid hormones, their free forms and indices of energy and lipid metabolism were measured in blood samples of 16 dairy cows expressing detectable oestrus signs. The cows were divided into two equal groups according to their days in milk (DIM=53-90 and DIM=100-150). In each group, 4 cows expressed the oestrus signs normally and the others were induced by hormone injection. Serum thyroxin (T4), free thyroxin (fT4), triiodothyronine (T3), free triiodothyronine (fT3), glucose, beta-hydroxybutyrate (BHB), non-esterified fatty acids (NEFA), triglyceride (TAG), cholesterol, very low density lipoproteins (VLDL-cholesterol), low density lipoproteins (LDL-cholesterol) and high density lipoproteins (HDL-cholesterol) were investigated. Comparison of all oestrus cows (normal or induced) between DIM groups (n=8 each) revealed lower levels of T4 (P=0.027) and T3 (P=0.022), but higher concentrations of fT4 (P=0.031) and fT3 (P=0.006) in the cows with lower DIM. Higher concentrations of TAG and VLDL (P=0.021) and cholesterol (P=0.046) as well as a tendency (P=0.074) for lower levels of BHB were other remarkable findings in cows with lower DIM. In cows with DIM=53-90, the normal oestrus cows had higher levels of T3 (P=0.044) as well as tendencies (P=0.083) for higher T4 and lower fT4 compared with induced cows. In cows with DIM=100-150, however, no significant difference was observed between the normal and induced oestrus cows. In conclusion, the cows that express oestrus signs normally may have better metabolic and thyroid hormone conditions compared to those that express heat by hormone injection. With progress in DIM, however, such differences may become less evident

Oxidative Status and Acute Phase Response in Post-transition Early- and Mid-lactation Holstein Cows and Their Correlations with Some Performance Records

Oxidative stress and acute phase response were assessed in post-transition early-lactation and mid-lactation Holstein cows regards to the possible effects on milk production and reproductive performance. In two farms, 113 cows, 2-6 years old within 21-150 days in milk (DIM) were sampled for whole blood three times with 30-day intervals. The concentrations of glutathione peroxidase (GPx), superoxide dismutase (SOD), malondialdehyde (MDA), haptoglobin (Hp) and serum amyloid A (SAA) were measured in plasma. Three DIM stages were defined for further comparisons: DIM=21-70 as a post-transition early-lactation; 71-110 as the late weeks of early-lactation and the early weeks of mid-lactation; and 111-150 as the major portion of mid-lactation. Blood parameters (DIM=21-150) of the cows that conceived before (n=29) and after (n=56) DIM=110 and the cows that remained open (n=27) were also compared with the same test. The relationships between blood parameters (DIM=21-150) and performance indices were studied by Spearman’s rho correlation test. The studied performance records were not statistically different (P>0.05) between farms and between the cows that conceived (n=85) and the cows that remained open (n=27). GPx was not different (P>0.05) among DIM stages in the sum of both farms, though it increased significantly in Farm 2 at DIM=111-150. The levels of SOD and MDA were not different between farms and among DIM stages (P>0.05). The levels of Hp and SAA through DIM stages were close to or higher than those reported in fresh or diseased cows and their changes were mostly not significant. Performance records and blood parameters were not different (P>0.05) between the cows that conceived before DIM=110 or later and those that remained open. Negative correlations were observed between Hp and the maximum milk yield of the first 90 days (r=-0.20, P=0.034) and average milk yield during 150 DIM (r=-0.17, P=0.065). No relationship was observed between the plasma parameters and the studied reproductive records. The activity of GPx showed negative correlations with the level of Hp (r=-0.14, P=0.036) and the activity of SOD (r=-0.19, P=0.004). Oxidative stress was not a problem of the studied farms during DIM=21-150. However, high levels of Hp and SAA could reveal continuous mild stressful or inflammatory conditions during DIM=21-150, contributing to the less efficient milk production

Discrepancies in Evaluating Farm Management Routines as Risk Factors of Raw Milk and Udder Hygiene in Selected Dairy Farms of Fars Province, Iran

The management practices relevant to bulk tank milk quality were studied in 29 dairy farms of Fars Province, Iran. Farm management practices were obtained by completion of a questionnaire and direct observation. Bulk milk was evaluated by performing standard plate count (SPC), preliminary incubation count (PIC), laboratory pasteurization count (LPC), coliform count (CC), somatic cell count (SCC) and detection of the contagious mastitis agents. The farms were divided into low and high SPC groups (below and above 100,000 CFU/mL) based on Iranian standards. Comparisons of the laboratory results between groups were done using two independent samples t-test. The relationships between the laboratory results were studied by Pearson’s correlation coefficients, all after logarithmic transformation. Associations of managerial risk factors (obtained by the questionnaire and one time of observation) with laboratory results were investigated using two independent samples t-test. P-values 0.05). Strong correlations were detected between SPC and PIC, SPC and CC, and PIC and CC, but many of the well explained risk factors of undesired milk quality lacked any relation with high bacterial counts of raw milk. This could be due to the small number of the studied farms, almost similar faults in the farms, wrong answers of the employees to the questions and modification of the milking practices in the presence of an inspector. Infections with Staphylococcus aureus and Mycoplasma bovis could be potential problems in the studied farms, contributing to the elevation of SCC and/or SPC levels. Veterinary interventions could not be based on the questionnaire results. Direct and frequent observations of farm routines could be recommended