Effect of conventional and intensified milk replacer feeding programs on performance, vaccination response, and neutrophil mRNA levels of Holstein calves.

This study compared conventional and intensified milk replacer feeding regimens on growth, intake, respiratory and fecal scores, vaccination response, and neutrophil mRNA levels. Holstein calves were randomly assigned to a 10-wk study on d 2 of life. Treatments were conventional (CON; n=8) and intensified (INT; n=7) milk replacer feeding programs. Conventional calves were fed a 20.8% crude protein and 21.0% fat milk replacer at 1.25% of birth body weight (BW) from wk 1 to 6 of life and 0.625% of birth BW during wk 7. A 29.3% crude protein and 16.2% fat milk replacer was fed to INT calves at 1.5% of birth BW during wk 1, 2% of current BW from wk 2 to 6, and 1% of current BW during wk 7. All calves were given milk replacer twice daily during wk 1 to 6, once daily during wk 7, and were weaned completely during wk 8. Calf starter intake was measured daily through wk 8. Body weight and withers height were measured weekly. Fecal and respiratory scores were recorded twice daily at feeding. Calves were vaccinated against ovalbumin at the end of wk 1, 3, and 5. Blood samples were collected at the end of wk 1, 3, 5, and 8 for analysis of serum anti-ovalbumin IgG concentration and for isolation of neutrophils. Quantitative PCR was used to measure neutrophil mRNA levels of 7 functionality genes. Treatment did not affect total DMI or anti-ovalbumin IgG response. Intensified milk replacer feeding increased average daily gain, protein intake, fat intake, and feed efficiency compared with the CON feeding program. Compared with CON calves, INT calves had greater fecal scores, indicating looser feces and greater respiratory scores, indicating more respiratory problems. Calves assigned to the INT treatment had increased neutrophil mRNA levels of L-selectin, and at wk 8, neutrophil cytosolic factor 1 was increased and toll-like receptor 4 tended to be increased compared with CON calves. This suggests greater activation of neutrophils in INT calves postweaning, but differences were relatively small and levels of the other 4 genes were unaffected. An INT milk replacer feeding program increased growth, fecal scores, and respiratory scores preweaning, increased mRNA levels of 2 neutrophil genes postweaning, and did not affect vaccination response.

Effect of saturated fatty acid supplementation on production and metabolism indices in heat-stressed mid-lactation dairy cows.

Experimental objectives were to determine the effects of supplemental saturated fatty acids on production, body temperature indices, and some aspects of metabolism in mid-lactation dairy cows experiencing heat stress. Forty-eight heat-stressed Holstein cows were allocated into 3 groups (n=16/group) according to a completely randomized block design. Three treatment diets consisted of supplemental saturated fatty acids (SFA) at 0 (SFA0), 1.5 (SFA1.5), or 3.0% (SFA3) of dry matter (DM) for 10 wk. Diets were isonitrogenous (crude protein=16.8%) and contained 1.42, 1.46, and 1.49 Mcal of net energy for lactation/kg of DM for the SFA0, SFA1.5 and SFA3 diets, respectively. The average temperature-humidity index at 0700, 1400 and 2200 h was 72.2, 84.3, and 76.6, respectively. Rectal temperatures at 1400 h were decreased with fat supplementation. Treatment did not affect dry matter intake (20.1+/-0.02 kg/d), body condition score (2.72+/-0.04), body weight (627+/-16.1 kg), or calculated energy balance (1.32+/-0.83 Mcal/d). Saturated fatty acid supplementation increased milk yield, milk fat content, and total milk solids. Increasing fat supplementation decreased plasma nonesterified fatty acids (8%) but had no effect on other energetic metabolites or hormones. In summary, supplemental SFA improved milk yield and milk fat content and yield and reduced peak rectal temperatures in mid-lactation heat-stressed dairy cows. This demonstrates the remarkable amount of metabolic heat that is "saved" by energetically replacing fermentable carbohydrates with supplemental SFA.

Excellence in teaching for promotion and tenure in animal and dairy sciences at doctoral/research universities: a faculty perspective.

In this study, animal or dairy sciences faculty from doctoral/research universities were surveyed to clarify teaching performance expectations for the purpose of promotion and tenure of assistant professors. A survey tool including 15 evaluation criteria was available online and at the registration desk of the 2005 Joint Annual Meeting of the American Dairy Science Association and the American Society of Animal Science. The analyzed data set included 47 faculty (41 tenured and 6 tenure-track) with a substantial teaching responsibility from 27 different departments in 25 states. Four criteria were perceived as currently overemphasized: student evaluation of the instructor, student evaluation of the course, authoring peer-reviewed publications, and authoring an undergraduate textbook or book chapter. Nevertheless, more than 50% of respondents reported that these criteria should be used. One criterion emerged as being currently underemphasized: documentation of personal assessment of one's own teaching by preparing a portfolio. The lack of consensus for the remaining 10 items may have reflected substantial differences in institutional practices. The significance of overemphasis or underemphasis of certain criteria varied substantially depending on the respondent's perceived institutional mission. When asked about recognition within their department, 68% of respondents indicated that efforts in teaching improvement were properly rewarded. Respondents doubted the meaningfulness and appropriateness of student ratings tools as currently used. Results also suggested that animal and dairy science faculty placed a higher value on criteria recognizing excellence in teaching based on intradepartmental recognition (e.g., interactions with close-up peers and students) rather than recognition within a broader community of scholars as evidenced by authorship or success in generating funding for teaching. Proposed improvements in the evaluation of teaching for promotion and tenure include 1) providing tenure-track faculty with written guidelines at the time of hiring; 2) ensuring that student ratings tools are reliable and valid; 3) carefully mentoring new faculty within the departmental and institutional culture; and 4) encouraging self-reflection and documentation of attempts to address pedagogical issues in one's own teaching. Educational leaders in doctoral/research universities should promote changes to enhance teaching performance of future faculty graduating from their institutions.

Effect of dry period length on reproduction during the subsequent lactation.

Days dry may influence reproductive measures such as days to first postpartum ovulation, days open, and pregnancy per artificial insemination (AI). Holstein cows (n = 781) from an approximately 3,000-cow commercial dairy operation were randomly assigned to 1 of 2 treatments with different targeted dry period (DP) lengths. Treatments were 1) a traditional DP of 55 d (T) or 2) a shortened DP of 34 d (S). All dry cows on T were fed a low-energy diet until 35 d before expected calving, and then at 34 d before expected calving, cows on T and S were fed a moderate energy diet until parturition. After parturition, all cows consumed the same diets that included a postcalving diet followed by a lactation diet. Actual days dry for each treatment were close to expected values, 34 and 56 d for S and T, respectively. Median days until first postpartum ovulation occurred sooner for S compared with T (35 vs. 43 d). The percentage of cows that were classified anovular by 70 d in milk (DIM) was more than 2-fold greater for cows on T than S (18 vs. 8%). Cows received AI after standing estrus starting at d 45, and the percentage of cows pregnant at 70 DIM tended to be greater for S than T; younger cows were similar (20.2 vs. 18.8%), but there was a difference between S and T in older cows (20.3 vs. 10.6%). Similarly, median days open tended to be fewer for cows on S than T. At 300 DIM, 85% of cows in both treatments were pregnant. Combining data from first and second service, pregnancies per AI were greater in older cows on S than T (32 vs. 24%). Thus, shortening the DP appeared to increase reproductive efficiency in older cows by shortening time to first ovulation, reducing numbers of anovular cows, and improving fertility. Future studies at more locations with varying reproductive management strategies are needed to confirm and provide the mechanistic basis for these results.

Effects of dry period length on milk production and health of dairy cattle.

Holstein cows (n = 781) in a commercial dairy herd were used in a randomized design to evaluate 2 dry period (DP) management strategies on milk production, milk components, milk quality, colostrum quality, and incidence of metabolic disorders. Cows were randomly assigned to a traditional 55 d (T) or shortened 34 d (S) DP. Cows assigned to T were fed a low-energy diet until 34 d before expected calving at which time all cows were fed a moderate-energy transition diet until calving. Postpartum, cows assigned to T produced more milk and tended to produce more solids-corrected milk than cows on S. Treatment differences in milk and solids-corrected milk yield were accounted for by cows in their second lactation. Milk fat percentage did not differ between treatments, but milk protein percentage was greater for cows assigned to S. Colostrum quality measured as IgG concentration did not differ between management strategies. Somatic cell score and cases of mastitis were not affected by management strategy. There was a tendency for prepartum nonesterified fatty acid (NEFA) to be lower for cows assigned to T compared with S. However, postpartum, cows assigned to S had significantly lower NEFA concentrations than those assigned to T. The incidences of ketosis, retained placenta, displaced abomasum, and metritis did not differ between treatments. Postpartum energy balance, as indicated by plasma NEFA, may have been improved for cows assigned to S; there was no detectable effect on animal health.

Technical note: Effect of sampling protocol on plasma nonesterified fatty acid concentration in dairy cows.

The objective of these experiments was to determine effects of sampling protocol on plasma nonesterified fatty acid (NEFA) concentration. In experiment 1, 8 nonlactating, nongestating dairy cows were blood sampled from a jugular vein catheter (basal, 0 min), moved to an exercise lot for 15 min, returned to stanchions, and sampled immediately and at 5, 15, 30, 60, and 120 min following return to their stalls. Following 15 min of exercise, plasma NEFA concentration increased, peaking at 5 min (225 microEq/L) and returning to basal (84 microEq/L) by 30 min (110 microEq/L). Cows were then moved to box stalls overnight, and 24 h after the basal sample, they were locked up and sampled again. Housing cows in a box stall overnight and locking them in headlocks increased plasma NEFA concentration (184 microEq/L). In a second experiment at a large free-stall commercial dairy, 11 late-gestation nonlactating dairy cows were locked in headlocks at feeding, blood was sampled from the coccygeal artery or vein (0 min), and cows were then released and allowed to finish eating and return to their stalls. Cows were then herded to headlocks and sampled immediately at 120 min after initial sampling and at 135, 150, and 180 min. Plasma NEFA concentration was highest at initial lockup (0 min; 284 microEq/L), lowest at 180 min (178 microEq/L), and intermediate at time points in between. A second group of 10 late-gestation nonlactating dairy cows were locked in headlocks at feeding, and blood was sampled immediately and at 5, 15, 30, and 60 min. Plasma NEFA concentration was highest 15 min after being placed in headlocks and lowest 60 min after lockup (221 and 113 microEq/L, respectively). At each time point in experiments 1 and 2, a behavior score was given (1 to 10; 1 = calm; 10 = extremely excited). In both experiments, there was a significant correlation between the plasma NEFA concentration and behavior score. In conclusion, plasma NEFA concentration was affected by sampling protocol.

Effects of increasing milking frequency during the last 28 days of gestation on milk production, dry matter intake, and energy balance in dairy cows.

Forty-eight Holstein cows were used in a randomized block design to evaluate different dry period lengths and prepartum milking frequencies (MF) on subsequent milk production, milk composition, solids-corrected milk production, dry matter intake (DMI), and energy balance. Lactating cows, milked 2 times/d, began a 7-d covariate period 35 d prior to the expected calving date. Cows were milked 0 times/d (0x), 1 time/d (1x), and 4 times/d (4x) for the last 28 d of gestation. If milk production decreased to less than 0.5 kg/milking or 1 kg/d, milking via machine ceased; however, teat stimulation continued 1 or 4 times/d according to the treatment assignment. All cows were milked 2 times/d postpartum (wk 1 to 10). Prepartum DMI tended to be greater for 1x and 4x compared with 0x. Prepartum, cows milked 1x produced 17% less milk than cows milked 4x (5.9 and 7.1 kg/d, respectively). There were no differences in prepartum and postpartum body condition scores, body weights, and DMI. Postpartum milk production by cows following their third or greater gestation was greater for 0x and 4x compared with 1x. Postpartum milk production by cows following their second gestation was significantly decreased with increased MF (0x vs. 1x and 4x). Regardless of parity, postpartum solids-corrected milk was greater for 0x compared with 1x and 4x. Postpartum fat yield was greater for 0x vs. 4x, with 1x being intermediate. Postpartum protein yield was greater for 0x vs. 4x, whereas 0x tended to have greater protein yield than 1x. Postpartum energy balance was greater for 1x and 4x relative to 0x. Continuous milking (1x and 4x) resulted in a loss of milk production in the subsequent lactation for cows following their second gestation; however, for cows following their third or greater gestation, increasing the MF from 1x to 4x in the last 28 d of gestation alleviated the loss in milk production.

Reduced dry periods and varying prepartum diets alter postpartum ovulation and reproductive measures.

There has been substantial recent interest in shortening dry periods; however, the effects of this management change on reproduction have not been adequately evaluated. Holstein cows (n = 58) were assigned in a randomized block design to 1 of 3 treatments: 1) traditional (T) dry period (approximately 56 d) in which cows were fed a low energy diet from 56 to 29 d prepartum followed by a moderate energy diet for 28 d; 2) shortened (S) dry period (approximately 28 d) in which cows were fed continuously a high energy diet; or 3) no planned (N) dry period in which cows were fed continuously a high energy diet. All cows received a high energy lactation diet after calving. Ovaries were evaluated by ultrasound and blood samples collected 3 times weekly beginning at d 6 or 7 postpartum until 7 d after second ovulation. Average days from calving until first detection of a 10-mm follicle were fewer in N (8.0 d) and S (8.9 d) than in T (10.5 d) cows. Time from calving to first ovulation was earlier in N (13.2 d) than in S (23.8 d) and T (31.9 d) cows. A greater percentage of follicles of the first follicular wave ovulated in N (89%; 16/18) than in T (42%; 8/19), with S (62%; 13/21) cows being intermediate. Double ovulation rate at the first ovulation was greater in T (61%) than N (16%), with S (35%) intermediate. No difference was detected in double ovulation rate at second ovulation (13/56). Number of cows with persistent corpus luteum (>30 d; 15/56) was not different among groups; however, short luteal phases were greater in N (28%; 5/18) than S (0%; 0/20) cows. Days to first artificial insemination were fewer in N (69.4 d) and S (68.0 d) than in T (75.0 d). First-service conception rate was greater in N (55%; 11/20) than in T (20%; 4/20), with S (26%; 6/23) cows being intermediate. Days open in pregnant cows were fewer in N (93.8 d) than in T (145.4 d), with S (121.2 d) cows being intermediate. Thus, shortening or eliminating the dry period leads to earlier postpartum ovulation and the results highlight the need for future large field studies to accurately evaluate the effect of dry period length on reproductive performance of lactating dairy cows.

Reducing dry period length to simplify feeding transition cows: milk production, energy balance, and metabolic profiles.

Sixty-five Holstein cows were used to evaluate management schemes involving altered dry period (DP) lengths on subsequent milk production, energy balance (EB), and metabolic variables. Cows were assigned to one of 3 treatments: traditional 56-d DP (fed a low-energy diet from -56 to -29 d and a moderate energy diet from -28 d to parturition; T), 28-d DP (continuously fed a high energy diet; S), and no planned DP (continuously fed a high energy diet; N). Prepartum DM intake (DMI), measured from 56 d prepartum through parturition, was lower for cows on the T treatment than for cows on the S treatment and was higher for cows on the N treatment than for cows on the S treatment. There were no differences in prepartum plasma glucose, and beta-hydroxybutryric acid; there was a treatment by time interaction for prepartum plasma nonesterified fatty acid (NEFA). There was no difference in prepartum liver triglyceride (TG); postpartum liver TG was decreased for cows on the N treatment compared with cows on the S treatment, but was similar for cows on the T and S treatments. Postpartum NEFA was similar between cows on the T and S treatments, but was greater for cows on the S treatment than for cows on the N treatment. Postpartum glucose was greater for cows on the N treatment compared with cows on the S treatment and tended to be greater for cows on the S treatment than for cows on the T treatment. There was no difference in postpartum solids-corrected milk (SCM) production or DMI by cows on the T vs. S treatment. However, there was a tendency toward lower postpartum SCM production by cows on the N vs. S treatment and a tendency for greater postpartum DMI by cows on the N vs. S treatment. Postpartum EB was greater for cows on the S vs. T treatment and the N vs. S treatment. In general, T and S management schemes had similar effects on DMI, SCM, and metabolic variables in the first 70 d of the subsequent lactation. Eliminating the DP improved energy and metabolic status.

Body composition and estimated tissue energy balance in Jersey and Holstein cows during early lactation.

The rate and extent of estimated energy mobilization and the relationship between fat depth at the rib and thurl and body condition score (BCS) were investigated in Jersey and Holstein cows in early lactation. Twenty-six cows were paired by breed, parity, and calving date, and were individually fed a total mixed ration ad libitum from parturition through 120 d in milk. Feed intake and milk production were measured daily; body weight (BW), BCS, subcutaneous fat depth, milk composition, and concentration of plasma nonesterified fatty acids were measured every 2 wk. Estimated tissue energy balance (TEB) was calculated using 1989 NRC equations. Net energy intake was greater in early lactation for Holsteins compared with Jerseys, 37.8 and 28.2 Mcal/d, respectively. Milk energy was greater for Holsteins relative to Jerseys, 30.5 versus 21.2 Mcal/d. Fat depth and BCS did not differ between breeds. A positive relationship existed between fat depth and BCS for Jerseys; however, there was no significant relationship for Holsteins. The best-fit regression model for predicting TEB for Holsteins and Jerseys in early lactation included week of lactation, milk composition, and BCS. Jerseys remained in negative TEB for a shorter period of time relative to Holsteins. The TEB nadir was -6.19 and -12.9 Mcal/d, for Jerseys and Holsteins, respectively. Expressed as a proportion of metabolic BW (BW(0.75)), net energy intake did not differ between breeds, yet milk energy and estimated tissue energy loss were greater for Holsteins compared with Jerseys.