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Doctor of Philosophy / Department of Animal Sciences and Industry / Barry J. Bradford / Jeffrey S. Stevenson / Four experiments were conducted to assess nutritional and hormonal strategies to improve fertility in lactating dairy cows. In experiment 1, metabolites (-4, -2, +1, +2, +5, and +7 wk) and steroid hormones in ovarian follicular fluid (FF) and blood serum (BS) were examined in Holstein cows (n = 59) individually fed Saccharomyces cerevisiae fermentation product from -4 through +7 wk (calving = wk 0). Neither metabolites nor hormonal concentrations in BS or FF differed between treatments. In experiment 2 a rumen-protected glucose (RPG) product was supplemented at varying doses in the diet of lactating dairy cows with the objective to increase concentrations of glucose and insulin resulting in decreased activity of liver cytochrome P450 2C and P450 3A, thus increasing blood progesterone concentration. Neither pre-feeding nor post-feeding concentrations of glucose differed among treatments. Pre-feeding insulin did not differ among treatments, but a difference in the concentration of insulin (postprandial minus pre-prandial) was detected (P = 0.01). The increase in insulin was greater in control cows relative to the mean of the 3 RPG doses. We conclude that the insulin response to the RPG diets was diminished relative to the control. Supplementation with RPG did not impact concentrations of progesterone. Experiment 3 tested: (1) a shortened version of Ovsynch (SS: GnRH-1 -7 d - PGF2α - 24 h - PGF2α - 32 h - GnRH-2 - 16 h - AI) that excluded GnRH-1 to resynchronize ovulation in cows bearing a corpus luteum (CL) after a non-pregnancy diagnosis (NPD); (2) the value of including progesterone-releasing intravaginal insert + Ovsynch (OVS + CIDR) in absence of a CL compared with presence of a CL + OVS; and (3) the accuracy of detecting a functional CL by transrectal ultrasonography. Pregnancy per AI (P/AI) risk tended (P = 0.09)) to be greater for OVS than SS but did not differ from OVS + CIDR at 32 d (30.3% [n = 644], 25.7% [n = 678], and 25.9% [n = 270]), respectively. In SS cows, P/AI was greater (P = 0.01) when cows had a functional CL (progesterone was ≥ 1 ng/mL) vs. a nonfunctional CL at d 0, but did not differ from OVS cows. Short synch is a viable alternative to an entire OVS treatment when CL status is accurately detected. Experiment 4 was performed in 2 herds to determine if administering PGF2α concurrent with timed artificial insemination in lactating dairy cows would enhance P/AI. Pregnancy per AI at d 32 and 80 did not differ between treatments. Cows treated with PGF2 alpha in one herd produced more twins than control cows (11.7 vs. 3.2%), whereas no treatment difference was detected in the second herd (5.6 vs. 5.6%), respectively. We conclude that i.m. treatment of lactating dairy cows with 10 mg of PGF2α concurrent with timed AI did not improve P/AI or embryo survival, but increased twinning in one herd. Further research is warranted to determine nutritional and hormonal strategies to improve fertility.

Packing plants (n = 23), were audited for producer-related defects found in cull cows and bulls. Interviews, live animal and carcass evaluations, and subprimal evaluations were conducted during each audit. A drastic reduction in downer incidence was found between 1999 and 2007. All loads met the AMI guidelines for spacing. Excessive use of electric prods must be addressed by packers and transporters alike. Fewer cattle had mud/manure contamination on hides, horns, and brands than in 1999. Predominant hide color for beef cattle was black, while the predominant dairy color was the Holstein (black and white) pattern. Fewer cattle displayed evidence of bovine ocular neoplasia than in 1994 and 1999. Knots present on live cattle were less in the round and more in the shoulder region than in 1999. Dairy cows were more frequently lame in 2007 than 1999, while beef cows were less lame. Carcass bruising was less evident during the 2007 audit than in previous audits. Fewer cattle had arthritic joints in 2007 than in 1999. An increase in liver, tripe, heart, head, and tongue condemnation was witnessed in 2007 than in 1999. Carcass weights increased since 1999, as well as having less fat, indicating heavier muscled animals being slaughtered. The average fat color score was higher for beef cows (3.14) than dairy cows (2.42). Fabrication trends are similar to data collected in 1999 as almost half of cull cow fabrication yields are primal and subprimal type products. The majority of all cattle (64%) were able to be traced back to their original owner. End-user audits revealed a higher incidence of injection site lesions in dairy rounds (48%) than in beef rounds (12%). Lastly, the incidence of dairy round injection site lesions has increased since 1999 (35%), while beef round lesions were fewer since 1999 (20%).

Birth (BW) (n = 1,107) and weaning weight (WW) (n = 1,024), pregnancy rate (PR) (n = 1,255), calf crop born (CCB) (n = 1,232), calf crop weaned (CCW) (n = 1,225), and cow??s weight at palpation (CW) (n = 1,403) were evaluated from 1994 to 2004 in 143 F1 females who were sired by Brahman (B), Boran (Bo), and Tuli (T) bulls and who were out of Angus and Hereford cows. In 2004, mouth scores (MS) (n = 71) were assigned to the remaining females. PR, CCB, CCW, CW, and BCS were evaluated using a model that consisted of sire of dam breed, dam of dam breed, and calf??s birth year/age of dam as fixed effects. Sire of dam within sire breed of dam and dam within sire of dam within sire breed of dam were used as random effects. BW and WW were analyzed using the same model including calf??s gender. Two-way interactions were tested for significance. Year/age was significant for all traits (P < 0.05). Adjusted means for BW for calves out of cows by B, Bo, and T sires were 35.66, 35.38, and 35.59 kg respectively, and were not different (P > 0.05). Adjusted means for WW for calves out of cows by B, Bo, and T sires were 233.4, 220.1, and 208.2 kg respectively, and were significantly different. For both BW and WW, male calves were heavier (P < 0.05) than females. Adjusted means for PR for females sired by B, Bo, and T bulls were 0.914, 0.945, and 0.920, and were not different (P > 0.05). Adjusted means for CCB for females sired by B, Bo, and T bulls were 0.890, 0.943, and 0.910 respectfully, and Bo was higher (P < 0.05) than B. CCW showed the same ranking as CCB with adjusted means of 0.834, 0.887, and 0.857 for cows by B, Bo, and T bulls, with Bo being higher (P < 0.05) than B. CW adjusted means, in the fall of 2002, were 594.29, 519.38, and 517.3 kg. B-sired females were heavier (P < 0.05) than Bo- or T- sired cows. More Bo- (P = 0.013) and B-sired (P = 0.003) cows had solid mouths in 2004 than T-sired cows.

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The objective of this dissertation was to assess the dynamics of calcium (Ca) and phosphorus (P) metabolism in dairy cattle. Hypocalcemia, or a drop in blood Ca, is a common condition near parturition. All cows experience some degree of hypocalcemia. Maintenance of blood Ca within the acceptable range of 8 to 10 mg/dl is a balancing act between the demand for Ca for milk production and the cow's homeostatic mechanisms to maintain blood Ca. These homeostatic mechanisms include bone resorption that is driven by Ca demand however both Ca and P are released when bone is resorbed. These times of bone resorption and bone mineral replenishment have not been accounted for in current mineral recommendations. For the first study, it was postulated that dairy producers could administer 25-hydroxyvitamin D₃ (25-OH) in the prepartum period to prevent hypocalcemia. Twenty-seven multiparous Jersey cows were randomly assigned to receive an oral bolus containing corn starch (control, CON) or corn starch plus 15 mg of 25-hydroxyvitamin D₃ (25-OH) or 15 mg of vitamin D₃ (D₃) at 6 d prior to expected parturition. Jugular blood samples were collected at -14, -13, -5, -4, -3, -2, -1 d prior to expected calving, on the day of calving, and 1, 3, 5, 7, 9, 11, 13, 28, 56, and 84 d with respect to calving. Samples were analyzed for 25-OH, Ca, P, magnesium, osteocalcin (OC), and parathyroid hormone (PTH). Blood Ca, P, and Mg decreased near the time of calving and then increased over time. Serum 25-hydroxyvitamin D₃ was higher for cows dosed with 25-OH (119.0 pg/ml) compared with those dosed with D₃ (77.5 pg/ml) or CON (69.3 pg/ml). Cows dosed with 25-OH tended to have lower serum PTH concentration, but treatments did not affect serum Ca, P, or Mg. Serum OC was higher in second lactation cows compared with cows entering their third or fourth lactation but OC was unaffected by treatment. Although results indicated a 60% increase in serum 25-OH due to a single oral dose of 25-OH prior to calving, the amount administered in this study apparently was not sufficient for initiation of any improvement in Ca homeostasis at parturition. Due to the intimate relationship of Ca and P in bone, it was postulated for the second study that dietary Ca would affect bone mobilization and Ca and P balance in the lactating dairy cow. Eighteen Holstein cows were blocked by parity and calving date and randomly assigned to one of three 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. Total collection of milk, urine, and feces was conducted 2 wk prior to calving and in wk 2, 5, 8, 11, and 20 of lactation. Blood samples were collected at -14 and -10 d prior to 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, PTH, OC, and deoxypyridinoline (DPD). Rib bone biopsies were conducted within 10 d of calving 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. Dietary Ca concentration did not affect P balance in the weeks examined for this study but there was a clear effect of parity on balance, markers of bone metabolism, and bone P. 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 net bone formation after day 35. This was not reflected in balance measures however, this information may help refine dietary mineral recommendations for lactating dairy cows and ultimately reduce P excretion into the environment. Ultimately from the first study it is clear that oral dosing with 25-OH at 6 d prior to expected calving is not justified. However, we learned that parity has an effect on bone formation with younger animals resorbing and forming more bone and that net formation appears to occur after 30 days in milk. Both of these points were corroborated in the second study. Additionally, the second study demonstrated that dietary Ca content has no effect on P balance from 2 to 20 wk of lactation. Finally, the rib bone does not appear to be a sensitive indicator of bone metabolism or at least not at the time points we measured. / Ph. D.

Improved prediction of forage quality and cow performance may enhance the nutritional management of beef cows. In two 12 mo trials, mature beef cows (n=136) grazing tall fescue pastures were used to compare estimates of forage quality and animal performance. Forage quality was estimated by proximate analysis of forage samples (FOR) or by near infrared reflectance spectroscopy of fecal samples (FNIR). Nutritional Balance Analyzer (NutBal), NutBalPro and 1996 NRC Nutrient Requirements of Beef Cattle (NRC) programs were used to predict animal performance. The objectives were to compare FOR and FNIR estimates of CP and TDN and to evaluate the accuracy of cow performance predicted by FNIR-NutBal, FNIR-NutBalPro and FOR-NRC systems. Initial BW, body condition score (BCS), hip height and breed were used to establish cow biotypes for prediction programs. Every 28 d, cow BW and BCS were measured and forage and fecal samples collected. Weather data, cow status and FOR or FNIR results were entered into NutBal, NutBalPro and NRC programs. Forage CP estimated by FNIR (CPFNIR) or FOR (CPFOR) were similar. In trials 1 and 2, correlation coefficients between CPFNIR and CPFOR were r = .24 and r = .43, respectively. Forage TDN estimated by FNIR was greater (P <.05) and lowly or moderately correlated to FOR estimates. Actual BW change between weigh periods (BWCHG) and ADG were similar to NRC predictions, but less (P<.0001) than predicted by NutBal or NutBalPro. The NutBal or NutBalPro mean BCS change between weigh periods (BCSCHG) were greater (P<.001) than NRC or Actual BCSCHG. Actual and NRC BCSCHG were similar (P>.2, trial 1) or tended (P<.1, trial 2) to be similar. Cow performance estimated by NRC was highly correlated to Actual. Absolute differences in animal performance were also investigated for each prediction program. In trials 1 and 2, NutBal and NutBalPro over-predicted BWCHG, ADG and BCSCHG by 40 kg, 1.25 kg/d and .75 BCS, respectively, compared to actual cow performance. It appears that FNIR is a promising predictor of forage CP but not TDN. Also, the FOR-NRC is a satisfactory predictor of cow performance. / Master of Science