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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 these studies was to determine the effects of forage fiber, social hierarchy, and stocking density on stress in lactating cows during relocation to new dairy facilities. In experiment one, 23 lactating cows were fed a basal ration, or the basal ration plus grass or alfalfa hay at 10% of DM offered from 3 wk pre-move to 9 wk post-move. In experiment two, 17 lactating cows were housed together before and after relocation and evaluated for dominance rank. In experiment three, 44 cows were housed together before relocation, then in pens of varying stocking density (0.67, 0.83, 1.0, or 1.17 cows per stall) post-move. In these studies, the effects of treatment on MY, lameness, behaviors, plasma cortisol, cow cleanliness, and DMI were monitored. In experiment one, cows fed grass or alfalfa hay diets had higher plasma cortisol concentrations on the day of relocation than cows fed TMR, but there were no differences in DMI or MY. Cows fed alfalfa hay or TMR had increased lameness scores following relocation; cows fed grass hay did not have increased lameness scores. In experiment two, there were no differences in plasma cortisol or lameness scores between dominant and subordinate cows. Subordinate cows had lower MY following relocation compared to dominant cows. In experiment three, cows housed at a stocking rate of 1.17 had higher plasma cortisol than cows housed at a stocking rate of 0.67. All cows had higher lameness scores following relocation, but cows housed at a stocking rate of 0.67 tended to have higher lameness scores than cows housed at stocking rates of 0.83, 1.0, and 1.17. In summary, some management practices may decrease the negative effects of stress on lactating cows during relocation. / Master of Science

Lactation persistency is defined as the ability of a cow to maintain production at a higher level after peak yield. Hypothetically, more persistent cows are less susceptible to health and reproductive disorders. The objective of this research was to investigate the phenotypic relationships of common health disorders in dairy cows to lactation persistency. The relationships with peak yield and days in milk (DIM) at peak yield were also studied. Two separate investigations (Study 1 and Study 2) were performed. Study 1 used treatment incidence data and daily milk weights of 991 lactations from experimental dairy herds at Virginia Tech and Pennsylvania State University. Milk yield persistency (PM) was estimated for individual lactations using daily milk weights. In Study 2, producer recorded health data of 87555 lactations from 398 commercial herds were used. PM, fat (PF), and protein (PP) persistencies were estimated from TD yields. Mastitis only in the first 100 days, only after 100 DIM, and at any stage of lactation, and reproductive disorders including metritis, retained placenta, cystic ovaries, metabolic diseases including ketosis, milk fever and displaced abomasums, and lameness were considered in both studies. Mastitis both before and after 100 DIM was considered only in Study 1. Each disease was defined as a binary trait distinguishing between lactations with at least one incidence (1) and lactations with no incidences (0). Standardized measures of the persistencies, uncorrelated with yield, were calculated as a function of yield deviations from standard curves and DIM deviations around reference dates. Peak milk yield and DIM at peak of individual lactations were computed using Wood's function. Effects of persistency (PM, PF, and PP) on probability of the diseases in current and next lactations were examined through odds ratios from a logistic regression model. Conversely, the effects of diseases on persistencies, peak milk yield, and DIM at peak milk yield were also examined. Increasing PM, PF, and PP tend to reduce the incidence of mastitis, specifically in late stages of current and next lactation. PM and PP appear to have greater impact on mastitis than PF. No other likelihood of a disease was affected by the increasing persistencies. Post partum reproductive and metabolic diseases often had substantially positive effect on persistencies of both primiparous and multiparous cows (p<0.001 in Study 1 and p<0.001 in Study 2). Mastitis in early lactation appeared to increase persistency more often in multiparous cows (p<0.05 in Study 1 and p<0.005 in Study 2). Mastitis in late lactation had considerable but negative impact on persistency in both primiparous and multiparous cows (p<0.05 in Study 1 and p<0.005 in Study 2). Cows, which developed mastitis in both early and late lactations tended to have lower PM (p<0.05 in Study 1). Irrespective to the time of occurrence, effect of mastitis on milk, fat and protein yield persistencies was negative. Most of the diseases significantly affected DIM at peak milk yield in multiparous cows (p<0.05 in Study 1). Reproductive and metabolic disorders tended to delay DIM at peak milk yield while Mastitis in late lactation was associated with early DIM at peak milk yield. Lameness had no phenotypic relationships with shape of the lactation curve. Overall, diseases tend to affect milk, fat, and protein persistencies more strongly than the impact of persistency on likelihood of disease. / Master of Science