James D. Ferguson

Diet, production and reproduction in dairy cows

Reproductive efficiency has an important influence on gross margin per cow per year. Gross margin per cow is optimal when the combination of heat detection rate times the conception rate equals 0.35, which is the pregnancy rate. Milk production and time post calving should have little influence on fertility in a herd of dairy cows. If conception rate is reduced in the higher producing half of the herd, or if conception rate changes dramatically with time post calving, then nutritional stress may be reducing fertility. Energy management from the late gestation period through the post-calving period may have significant effects on reproductive function. Mismanagement of energy within a herd may be apparent in excessive body condition loss. Protein effects on fertility may be apparent as increased repeat breeding and associated with elevated plasma urea nitrogen. Deficiencies in trace elements and vitamins, particularly selenium and vitamin E, may be associated with increased reproductive disease. Reduction in reproductive performance in a herd should be examined in a systematic fashion to isolate the cause, which may be management, cow, bull, or environmentally related. Nutritional causes are more likely first due to energy management, secondly excessive protein feeding, and lastly trace element and vitamin deficiencies. Appropriate clinical tests may help confirm a diagnosis.

Positive End Expiratory Pressure: Effects on Lung Mechanics of Premature Lambs

Pulmonary mechanics were determined at 0, 3, 6, and 10 cm H2O positive and expiratory pressure (PEEP) in premature lambs at a mean gestational age of 134 days. Functional residual capacity increased (p less than 0.005) by 7% (1.6 ml/kg) per cm H2O PEEP. Dynamic lung compliance and specific compliance significantly decreased by 10% (0.11 ml/cm H2O/kg) and 9% (0.0051 l/cm H2O) per cm H2O PEEP, respectively, for PEEP above 3 cm H2O level. Inspiratory lung resistance increased significantly (p less than 0.05) only between 0 and 6 cm H2O PEEP while expiratory lung resistance increased (p less than 0.05) between 0 cm H2O PEEP and all higher levels. The data suggest that PEEP in excess of 3 cm H2O produces undesirable effects on lung mechanics in premature lambs. These results may be important in predicting contraindications and potential complications of positive pressure breathing in the newborn.

Dietary calcium has little effect on mineral balance and bone mineral metabolism through twenty weeks of lactation in Holstein cows

Calcium and P balance and mobilization from bone were evaluated through 20 wk of lactation to determine the timing and extent of net resorption of bone mineral and mineral balance in lactating dairy cows. Eighteen Holstein cows were blocked by parity and calving date and randomly assigned to 1 of 3 dietary treatments: high (1.03%, HI), medium (0.78%, MED), or low (0.52%, LOW) dietary Ca. Dietary P was 0.34% in all diets. Cows consumed treatment diets from calving to 140 DIM. Total collection of milk, urine, and feces was conducted 2 wk before expected calving and in wk 2, 5, 8, 11, and 20 of lactation. Blood samples were collected at 14 and 10 d before expected calving and 0, 1, 3, 5, 10, 14, 21, 28, 35, 56, 70, 84, 98, and 140 d after calving. Blood samples were analyzed for Ca, P, and parathyroid hormone concentration. Serum concentrations of osteocalcin (OC), a marker of bone formation, and deoxypyridinoline (DPD), a marker of bone resorption, were measured to assess bone mobilization. Rib bone biopsies were conducted within 10 d postcalving and during wk 11 and 20 of lactation. Dietary Ca concentration affected Ca balance, with cows consuming the HI Ca diet in positive Ca balance for all weeks with the exception of wk 11. Interestingly, all cows across all treatments had a negative Ca balance at wk 11, possibly the result of timed estrous synchronization that occurred during wk 11. At wk 20, Ca balances were 61.2, 29.9, and 8.1 g/d for the HI, MED, and LOW diets, respectively. Phosphorus balances across all treatments and weeks were negative. Bone Ca content on a fat-free ash weight basis was least in cows consuming the MED diet, but bone P was not different. Serum Ca and P were not affected by treatment. Dietary Ca concentration did not affect P balance in the weeks examined, but there was a clear effect of parity on balance, markers of bone metabolism, and bone P. Primiparous cows had greater serum OC and DPD concentrations than multiparous cows. Regardless of dietary treatment, serum OC concentration peaked around d 35 of lactation. Simultaneously, DPD concentration began to decrease, which may indicate a switch from net bone resorption to formation after d 35. However, this was not reflected in balance measures. This information may help refine dietary mineral recommendations for lactating dairy cows and suggests that dietary P requirements are independent of dietary Ca.

Objective Estimation of Body Condition Score by Modeling Cow Body Shape from Digital Images

Body condition score (BCS) is considered an important tool for management of dairy cattle. The feasibility of estimating the BCS from digital images has been demonstrated in recent work. Regression machines have been successfully employed for automatic BCS estimation, taking into account information of the overall shape or information extracted on anatomical points of the shape. Despite the progress in this research area, such studies have not addressed the problem of modeling the shape of cows to build a robust descriptor for automatic BCS estimation. Moreover, a benchmark data set of images meant as a point of reference for quantitative evaluation and comparison of different automatic estimation methods for BCS is lacking. The main objective of this study was to develop a technique that was able to describe the body shape of cows in a reconstructive way. Images, used to build a benchmark data set for developing an automatic system for BCS, were taken using a camera placed above an exit gate from the milking robot. The camera was positioned at 3 m from the ground and in such a position to capture images of the rear, dorsal pelvic, and loin area of cows. The BCS of each cow was estimated on site by 2 technicians and associated to the cow images. The benchmark data set contained 286 images with associated BCS, anatomical points, and shapes. It was used for quantitative evaluation. A set of example cow body shapes was created. Linear and polynomial kernel principal component analysis was used to reconstruct shapes of cows using a linear combination of basic shapes constructed from the example database. In this manner, a cows body shape was described by considering her variability from the average shape. The method produced a compact description of the shape to be used for automatic estimation of BCS. Model validation showed that the polynomial model proposed in this study performs better (error=0.31) than other state-of-the-art methods in estimating BCS even at the extreme values of BCS scale.

Pulmonary lavage in preterm lambs.

Summary: Pulmonary function was studied before and after bilateral lung lavage with oxygenated FC-80 fluorocarbon liquid in seven preterm Iambs, 134 days of gestation. Measurements of transpulmonary pressure, air flow, tidal volume, and functional residual capacity (FRC) enabled calculations of lung resistance and compliance, specific compliance, and work of breathing. Immediately postlav-age, arterial oxygen tension (PaO2) decreased significantly (P < 0.05) by 41% from control values. In addition, at 1 hr postlavage, lung compliance significantly decreased (P < 0.01) by 43% from control levels. Lung resistance, FRC, work of breathing, arterial carbon dioxide tension, and pH postlavage were not significantly different from postlavage values. The mean volume of FC-80 remaining in the lungs at 1 hr postlavage was 32% of the instilled volume. These data indicate that lung lavage with a low surface tension liquid has a relatively small effect on lung mechanics of the premature lung.Speculation: Adequate blood gas tensions and pH levels can be maintained both during and after bilateral fluorocarbon lavage with relatively small changes in lung mechanics. Based upon these findings, it is appealing to speculate that bilateral fluorocarbon lavage may be useful as a means of alveolar debridement, particularly in aspiration syndromes of the newborn.

Animal nutrition and management in the 21st century: dairy cattle

Dairy producers strive to increase production and efficiency. Consumers want products that contain less fat and more protein. Negative impacts of pollutants from animal agriculture on the environment must be controlled. The foregoing can be accomplished by regulating metabolic processes of the dairy cow through nutrition and biotechnology. The application of genetic engineering techniques can increase production and its efficiency, change the composition of milk and improve prevention, diagnosis and treatment of disease. Competent nutrition, reproduction and health programs and improved information systems for managing and utilizing information will be required.

Trends in gender, employment, salary, and debt of graduates of US veterinary medical schools and colleges

OBJECTIVE To characterize trends in gender, employment, starting salaries, and educational debt of graduates of US veterinary medical schools and colleges from 1988 to 2007. DESIGN Meta-analysis. Sample Population-Veterinary medical graduates from 26 or 27 of 27 US veterinary schools and colleges from 1988 through 2007. PROCEDURES Data were obtained from surveys published in the JAVMA. A chi2 test for trend was used to analyze trends in choices of employment and educational indebtedness for the veterinary graduate populations over time. RESULTS The greatest changes in employment occurred in predominantly large animal practice, which attracted 10.7% of new graduates in 1989 but only 2.2% in 2007, and in advanced study, which attracted 15.2% of new graduates in 1989 and 36.8% in 2007. In 2007, 75% of graduates were women, but this gender shift was not associated with the decline in the percentage of graduates entering rural practice. From 1989 through 2007, starting salaries in private practice increased at a rate of 4.60%/y. During the same period, educational debt increased at an annual rate of 7.36%, or 60% higher than the rate of increases for starting salaries. As a result, debt at graduation increased from 1.1 times the starting salary in 1989 to 2.0 times the starting salary in 2007. CONCLUSIONS AND CLINICAL RELEVANCE Veterinary students are now more in debt than they have ever been. This trend together with a substantial increase in the rate of interest charged for government-backed education loans create conditions for new graduates that appear unsustainable.

Effects of rumen-protected γ-aminobutyric acid on feed intake, lactation performance, and antioxidative status in early lactating dairy cows

The objective of this study was to investigate effects of rumen-protected γ-aminobutyric acid (GABA) on dry matter intake, milk performance, and serum metabolites in Chinese Holstein lactating cows. Thirty-nine multiparous cows were blocked based on days in milk (60 ± 6.3 d; mean ± SD) and milk production (30.9 ± 4.17 kg; mean ± SD), and were randomly assigned to 1 of 4 treatments, with rumen-protected GABA added at levels of 0, 0.8, 1.6, or 2.4 g/d, the actual predicted available amounts being 0, 0.30, 0.61, or 0.91 g of GABA/d, respectively. The experiment lasted for 8 wk, with the first week for adaptation. Milk yield and milk compositions were recorded weekly, and serum concentrations of GABA, neuropeptide Y, and biochemical and antioxidant variables were analyzed in the first, fourth, and seventh weeks of the study. Dry matter intake linearly increased in cows receiving added GABA compared with that for the control. Addition of 0.8 g of GABA/d was associated with higher milk yield than the other treatments, but contents of milk protein and fat did not differ across the treatments. Dietary GABA tended to quadratically enhance the serum content of GABA (23.6, 30.2, 29.8, or 28.3 mmol/L for 0, 0.8, 1.6, or 2.4 g/d, respectively), and increased neuropeptide Y, with the highest value (3.07 ng/L) for 0.8 g of GABA/d. Nonesterified fatty acid quadratically decreased with GABA addition, with the lowest value (218.1 μmol/L) for 0.8 g of GABA/d. Serum glutathione peroxidase and superoxide dismutase quadratically increased in cows fed GABA, whereas serum malondialdehyde was quadratically reduced for all GABA groups. Rumen-protected GABA quadratically improved N efficiency across all treatments, contributing to the enhanced production of milk and milk protein and reduced N emission to the environment. In conclusion, addition of rumen-protected GABA is beneficial for early lactation dairy cows in terms of feed intake, lactation performance, and animal health.

Body phosphorus mobilization and deposition during lactation in dairy cows

Dairy cow bone phosphorus (P) mobilization and deposition and their influence on P requirements were studied over the lactation cycle. Thirty Holsteins received a common diet during the dry period and one of the following three dietary treatments that varied in P percentage during the subsequent lactation (44 weeks): (i) 0.36 throughout (constant P, 0.36-0.36-0.36), (ii) 0.36 for 30 weeks then 0.29 for 14 weeks (P changed once, 0.36-0.36-0.29), and (iii) 0.43 for 10 weeks, 0.36 for 20 weeks, and 0.29 for 14 weeks (P changed twice, 0.43-0.36-0.29). Six P balance studies were conducted during the experiment, including one during the dry period and five along lactation, based on P intake, faecal P, urinary P and milk P, when appropriate. Blood samples were taken during balance to analyse bone formation (osteocalcin) and resorption (pyridinoline) marker concentrations and rib biopsies performed to determine bone P content. Phosphorus balance was negative during weeks -4 to -1 relative to lactation for all groups and remained negative for cows fed 0.36% P during weeks 1-5, but showed a positive value for cows that received 0.43% P. The balance was close to zero for all groups at weeks 19-23 and showed a clear retention during weeks 38-42; by the end of lactation, cows re-stored most of the P mobilized earlier. The pattern in P balance was consistent with changes in blood bone metabolism marker concentrations, rib bone P content, and faecal and urinary P concentrations over the experiment, indicating that cows, irrespective of the dietary P treatments received, mobilized P from bone during the late dry period when fed a low-Ca diet and early lactation, and re-stored P in late lactation. This dynamic of P metabolism can have important implications for dietary P requirements and ration formulations.

How do dairy cows chew?—Particle size analysis of selected feeds with different particle length distributions and of respective ingested bolus particles

Not only feed but also respective bolus particle size could alter diet efficiency and cow performance. The objective of this project was to characterize particle size of selected feeds and respective swallowed boli. Feed samples included 6 different particle length rye grass hay samples, 1 grass silage, 1 corn silage, and 1 total mixed ration (TMR). Rye grass hay samples consisted of long hay and chopped hay particles retained on the 19- (19_PSPS hay), 8- (8_PSPS hay), and 1.18-mm (1.18_PSPS hay) Penn State Particle Separator (PSPS) screens and those collected on the pan (PSPS_pan hay). A sixth hay treatment was rye grass forage cut at 50-mm lengths and dried to hay (50-mm hay). Treatments were offered to 4 nonlactating and 4 lactating cows following rumen evacuation. Swallowed boli were collected and the number of chews per gram of ingested feed dry matter was determined. Feed and bolus particles of lengths ≥5mm were collected on a 1.6-mm screen using a horizontal wet sieving technique. This cut point was chosen, as the literature suggests that most fecal particles are shorter than 5mm. Dry matter proportions on this screen (PROP_1.6) were determined and particle lengths of retained particles were measured by image analysis. Mean particle lengths (ML) were calculated considering particles ≥5mm in length. Boli of long hay, of 19_PSPS hay, of 8_PSPS hay, and of 50-mm hay had similar ML of 10 to 11mm. Bolus PROP_1.6 were also similar between these treatments, ranging from 0.54 to 0.69. Bolus particle lengths and distributions of these treatments were not related to respective hay particles. Bolus of 1.18_PSPS hay had PROP_1.6 of 0.51 and a smaller ML of 8mm. The PSPS_pan hay had PROP_1.6 of only 0.33, but was still chewed intensely. Apparently, little particle size reduction occurred when cows ate the TMR or the silages. Feed and respective bolus PROP_1.6 were as follows: 0.66 and 0.59 in grass silage, 0.52 and 0.55 in corn silage, and 0.44 and 0.38 in the TMR. Feed and respective bolus ML were as follows: 13.8 and 11.6mm in grass silage, 12.0 and 11.2mm in corn silage, and 13.1 and 12.5mm in the TMR. Rye grass hay particles retained on PSPS screens ≥8mm, with ML of at least 25mm were longer compared with TMR particles, but respective bolus particles were shorter. Bolus particle size is not associated with the size of large feed particles chewed to a constant size that is appropriate for deglutition. This size may be related to feed chemical composition.