Effect of body condition loss in early lactation Holstein cows on plasma IGF-I, prolactin and NEFA during breeding period and its association with some reproductive indices.

The associations between early lactation changes in the body condition score (BCS) and mid-lactation levels of blood insulin-like Growth Factor-I (IGF-1), prolactin, insulin, nonesterified fatty acids (NEFA), milk production and some reproductive indices were investigated. Monthly milk yield and BCS were recorded. Blood samples were collected on days 60, 90, and 120 (±5 days) of lactation. Twelve and 17 cows showed BCS losses ≤0.75 and >0.75 on day 60, respectively. BCS losses ≤0.75 till day 60 after calving enhanced the IGF-I concentration on day 90 (57.8 ± 10.7 vs. 35.6 ± 17.8 ng/mL; p = .001). The differences in blood metabolites were prominent on day 90. Trends of insulin changes between day 60 BCS (p = .04) groups were different. Inverse correlations were detected between IGF-I and NEFA (-0.6, p = .001), IGF-I and milk production (-0.4, p = .05), NEFA and prolactin (-0.8, p < .001) on day 90. Higher percentages of cows with BCS loss >0.75 (day 60) showed their first heat after day 40 postpartum. In conclusion, irrespective of BCS at the time of breeding, the level of BCS loss during the first 60 days of lactation may affect further reproductive performance due to prolonged alterations of IGF-I, NEFA, prolactin and insulin levels. The extent of postpartum BCS loss may be a predictor of the metabolic status of cows during mid-lactation.

Impact of FMD outbreak on milk production and heifers' growth on a dairy herd in southern Iran.

Foot and mouth disease is endemic in Middle Eastern countries including Iran but its impact is poorly characterized. The present study was conducted to evaluate the impact of FMD outbreak on milk production and heifers' growth in an industrial dairy herd located in Fars province, southern Iran. Data about individual milk production, heifers' growth and total daily milk (sold for manufacturing), its fat and protein content and somatic cell counts were collected from the herd database. Based on the results of the linear mixed models, a significant decline in individual milk production after the outbreak was observed compared with before the outbreak. There was a total reduction of 8.0 and 4.7% in mean daily milk production per cow after the outbreak when compared with before (over a 42days outbreak period) in lactation one (P<0.001) and lactation ≥2 cows (P=0.024), respectively. The total daily milk (P=0.027) and protein (P=0.002) showed significant decline during the outbreak period. The fat content decreased after the outbreak (P=0.014). Somatic cell counts did not show significant changes. The recorded heifers' weights (4-17 months of age) showed 7.1kg decrease after the outbreak in comparison with the period before that (P<0.001). In conclusion, we observed a negative impact of FMD outbreak on milk production and heifers' growth in study herd. The impact on daily milk production was less than the values reported previously. This difference could be attributed at least partly to differences in livestock genetics and management practices. Lower growth rate of heifers after the outbreak period could potentially extend the age at first calving. It is suggested that farmers are educated on awareness and preparation for infectious disease outbreaks and to practice good management routines that could potentially reduce the economic impact of these diseases.

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.

Changes of vitamins A, E, and C and lipid peroxidation status of breeding and pregnant sheep during dry seasons on medium-to-low quality forages.

This study assessed the changes of plasma vitamin A, E, and C and the lipid peroxidation status of sheep during breeding and pregnancy under drought conditions. The study was conducted on 105 cross-bred fat tailed ewes, 3-5 years old with body condition scores (BCS) of 2.5 to 3.5. The ewes were grazing on medium-to-low quality forages during summer and low quality forages within the succeeding months and had ad libitum access to a mixture of alfalfa hay (40%) and wheat straw (60%) in the afternoons. From 3 weeks before breeding till 1 month after the introduction of rams, 300 g of barley grain/head/day was offered to the ewes and then the supplemental grain was reduced to 100 g/head/day. For better synchronization of estrus cycles in ewes, they were isolated from the rams for at least 2 months and then kept in close proximity of the rams for 1 week before the introduction of the rams to the ewe flock. Then, whole blood samples were collected on days 1, 7, 21, and 120 after ram introduction. Vitamins A, E, and C were measured in plasma. Malondialdehyde (MDA) was measured in the hemolysate as a biomarker of lipid peroxidation. Plasma progesterone (P4) was measured in the samples of day 120 for assessing pregnancy status of the ewes. Vitamins A and C showed continuous and significant declines (P < 0.05) through days 1 to 120. Vitamin E declined only during the first 21 days of the study and remained almost constant till day 120. MDA concentration increased significantly at day 21. An elevated concentration of MDA was also detected at day 120. The difference between days 21 and 120 was not significant (P > 0.05). A positive correlation between vitamins E and C was detected at day 120 (r = 0.349, P < 0.01). Age and BCS did not affect the patterns of changes. Assuming that the ewes with P4 concentrations ≥2.5 ng/ml were pregnant, 95 out of 105 ewes (90.5%) were pregnant at day 120 of the study. Under the conditions of the present study with medium-to-low quality pastures as the main sources of feed, ewes of various ages and body conditions may suffer from oxidative stress during breeding and pregnancy.