Production of milk from feed dry matter intakes (DMI), called dairy or feed efficiency, is not commonly measured in dairy herds as is feed conversion to weight gain in swine, beef, and poultry; however, it has relevance to conversion of purchased input to salable product and proportion of dietary nutrients excreted. The purpose of this study was to identify some readily measured factors that affect dairy efficiency. Data were collected from 13 dairy herds visited 34 times over a 14-mo period. Variables measured included cool or warm season (high ambient temperature <21 degrees C or >21 degrees C, respectively), days in milk, DMI, milk yield, milk fat percent, herd size, dietary concentrations (DM basis) and kilograms of crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), and forage. Season, days in milk, CP % and forage % of diet DM, and kilograms of dietary CP affected dairy efficiency. When evaluated using a model containing the significant variables, dairy efficiency was lower in the warm season (1.31) than in the cool season (1.40). In terms of simple correlations, dairy efficiency was negatively correlated with days in milk (r = -0.529), DMI (r = -0.316), forage % (r = -0.430), NDF % (r = -0.308), and kilograms of forage (r = -0.516), NDF (r = -0.434), and ADF (r = -0.313), in the diet, respectively. Dairy efficiency was positively correlated with milk yield (r = 0.707). The same relative patterns of significance and correlation were noted for dairy efficiency calculated with 3.5% fat-corrected milk yield. Diets fed by the herds fell within such a small range of variation (mean +/- standard deviation) for CP % (16.3 +/- 0.696), NDF % (33.2 +/- 2.68), and forage % (46.9 +/- 5.56) that these would not be expected to be useful to evaluate the effect of excessive underfeeding or overfeeding of these dietary components. The negative relationships of dairy efficiency with increasing dietary fiber and forage may reflect the effect of decreased diet digestibility. The results of this study suggest that managing herd breeding programs to reduce average days in milk and providing a cooler environment for the cows may help to maximize dairy efficiency. The mechanisms for the effects of the dietary variables on dairy efficiency need to be understood and evaluated over a broader range of diets and conditions before more firm conclusions regarding their impact can be drawn.
Continued increases in Johne's disease around the world suggest more information is needed to understand the mechanisms by which the causative agent, Mycobacterium avium subsp paratuberculosis (MAP), is spread among livestock on the farm site. Livestock watering troughs are frequented by all animals on a farm; they provide a moist, nutrient-rich environment for bacterial survival, and the trough basin provides a surface for bacterial adhesion (i.e., biofilm formation). The goal of this study was to determine whether addition of chlorine to trough water could prevent or reduce biofilms containing MAP on trough materials. MAP was inoculated into trough water containing normal trough water microbial flora. The concentration of MAP in biofilms on suspended 1.5 in x 0.6 in (3.8 cm x 1.5 cm) concrete, plastic, galvanized or stainless steel trough materials was evaluated. Chlorine (2 ppm) was added to the trough water on day 7, and then weekly for 70 days. The concentration of MAP in biofilms on the trough materials was measured using quantitative, real-time PCR to target the MAP-specific 1S900 sequence in DNA extracts. Chlorination was most effective against MAP on galvanized steel and stainless steel trough materials (99% reduction (t99) in biofilmassociated MAP in 15 and 16 days, respectively). This value was two to four times higher for MAP in biofilms on plastic and concrete materials (t99 of 33 and 66 days, respectively). Differences in effectiveness of disinfection may result from higher pH (pH 8.23) in troughs with concrete materials and lower chlorine availability in troughs with plastic materials. These results suggest that the effectiveness of chlorine disinfection depends on trough material construction, pH, and chlorine availability. Optimization of disinfection protocols and elimination of biofilms on trough surfaces should reduce persistence of MAP in trough waters.
Estrus synchronization programs have been used to manage reproduction in dairy cattle for many years. These programs involve various protocols for administration of a single hormone or combinations of hormones, but results have varied among programs and herds. Several synchronization programs use injections of prostaglandin F2a (PGF2a).1-3 A commonly used PGF2a program includes per rectal palpation to identify a corpus luteum (CL). Cattle with a CL are injected with PGF2a, observed for estrus, and inseminated only after estrus is detected. This program depends on the palpator's ability to detect a prostaglandin-receptive CL and may not be the most effective way to evaluate CL activity. Other programs that use PGF2a include the administration of 2 injections of PGF2a at selected intervals (usually 12 to 14 days) and insemination at a predetermined time or after cattle are detected in estrus. Both of these programs have resulted in the highest conception rates when cattle were inseminated after being detected in estrus, rather than inseminating at a predetermined time without detection of estrus.4 A new ovulation synchronization program5-11 does not require estrus detection. This program (Ovsynch) uses gonadotropin-releasing hormone (GnRH) and PGF2a to synchronize ovulation, which may not be accompanied by detectable signs of estrus. In the Ovsynch program, an initial dose of GnRH is used to synchronize waves of follicles and PGF2a is used to lyse the CL in groups of cattle and synchronize estrus. A second injection of GnRH induces ovulation of the dominant follicle in 85 to 95% of the synchronized cattle.5 Pregnancy rates often drop during seasons with high ambient temperature.7 This may be related to heat stress, rather than problems with estrus or ovulation synchronization, because conception rates typically decrease during periods with high ambient temperature.12
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