K.G. Odde

Individual animal and maternal risk factors for morbidity and mortality of neonatal beef calves in Colorado, USA☆

Abstract A prospective study was conducted to quantify the individual animal and maternal factors that affected morbidity and mortality of calves in Colorado beef herds. The study subjects were all calves born in ten participating herds during the 1990 and 1991 calving seasons. All 3666 calves born during the study period were individually identified at birth, and subsequent disease events were recorded by the producers. The disease outcomes of interest and their observed incidence rates were: perinatal (birth to 12 h) mortality, 2.5%; general neonatal (12 h to 45 days) mortality, 2.2%; general neonatal morbidity, 4.4%; neonatal diarrhea, 1.1%; neonatal respiratory disease, 1.0%; mothering problems/weak calves, 1.2%; and neonatal enterotoxemia/sudden death, 1.4%. Data analysis utilized multiple logistic regression. All analyses were adjusted for herd. Perinatal mortalily was greater ( P P P =0.06). General neonatal mortality was higher ( P

Synchronization of estrus in suckled postpartum beef cows with melengestrol acetate, 48-hour calf removal and PGF2α

One hundred and sixty-five suckled postpartum beef cows were utilized to evaluate the effectiveness of 2 estrus synchronization systems for the initiation and synchronization of estrus. The treatment groups consisted of 1) melengestrol acetate (MGA)-PGF2alpha (cows were given 0.5 mg MGA/head/day for 14 d with 25 mg PGF2alpha injected 17 d after the last day of MGA administration); 2) MGA-48-h calf removal (CR)-PGF2alpha (cows were given 0.5 mg MGA/head/day for 14 d with 48-h calf removal starting on the second day after completion of the MGA regimen plus 25 mg PGF2alpha administered 17 d after the last day of MGA); and 3) unsynchronized controls. Cows were assigned to treatments by the numbers of days post partum, body condition, age, and breed of sire. The cows were observed for estrus at 12-h intervals for 5 d after PGF2alpha administration and were artificially inseminated 12 to 18 h after the observed estrus. Both the MGA-PGF2alpha and MGA-CR-PGF2alpha treatments (64.8 and 61.8%) had greater (P < 0.05) 5-d estrus rates than the control treatments (34.5%). The synchronized pregnancy rate was greater (P < 0.05) for the MGA-CR-PGF2alpha than the control treatment.(52.7 vs 30.9%, respectively). The MGA-CR-PGF2alpha cows had a higher 25-d pregnancy rate than either the MGA-PGF2alpha (P < 0.05) or control cows (P < 0.08). Of the anestrous cows at the beginning of treatment, more MGA-CR-PGF2alpha (P = 0.1) and MGA-PGF2alpha cows were cyclic posttreatment than control cows (58.7 and 55.1 vs 44.7%, respectively), suggesting that treatment initiated estrous cycles in only a small number of the anestrous cows. Both MGA-PGF2alpha and MGA-CR-PGF2alpha treatments appear to be effective methods of synchronizing estrus in suckled postpartum beef cows. However, MGA-CR-PGF2alpha was more effective in establishing pregnancy earlier in the breeding season than MGA-PGF2alpha.

The influence of neonatal health on weaning weight of Colarado, USA beef calves

The effect of morbidity during early life on the weaning weight of calves in Colorado beef herds was investigated as part of a prospective longitudinal observational study. A total of 2609 calves born in nine participating herds during the 1990 and 1991 calving seasons were monitored for disease events and subsequently weighed at weaning as a measure of performance. Morbidity outcomes of interest and their observed incidence rates were: general neonatal (to 45 days) morbidity, 2.6%; neonatal diarrhea, 1.0%; neonatal respiratory disease, 1.0%; and mothering problems/weak calves, 0.4%. Mean calf weaning weight was 244±46 kg. Weaning weight data were adjusted by multiple regression for the effects of the herd, year, age of the calf, age of the dam, calf sex, frame size of the dam, and twin birth. General morbidity during the neonatal period resulted in a 15.9 kg reduction (P<0.01) in calf weaning weight. When morbidity was investigated as more specific disease conditions, calves that were classified as mothering problems/weak calves (i.e. calves that experienced maternal neglect, abandonment, or starvation, and weak calves) weighed 24.4 kg less (P<0.01) at weaning than did non-afflicted calves. Respiratory conditions and diarrhea during the neonatal period resulted in 16.5 kg (P<0.01) and 10.7 kg (P<0.05) reductions in weaning weight, respectively. Thus, disease occurrence during the early life of the calf had a detrimental effect on weaning weight.

Synchronization of estrus in suckled postpartum beef cows with melengestrol acetate and PGF2α

A total of 402 two suckled postpartum beef cows at 2 locations (CSU and ECRC) were utilized in 3 trials to evaluate the effectiveness of a combination melengestrol acetate (MGA)-PGF2alpha estrus synchronization system in spring-calving cows. The cows were allocated by days post partum, body condition score (1 = emaciated; 9 = obese), sire breed, and dam age at the beginning of treatment to 1 of 2 treatments within location and trial: MGA-PGF2alpha (0.5 mg MGA/head/d for 14 d with 25 mg of PGF2alpha injected 17 d after MGA withdrawal), and unsynchronized controls. All cows were observed for estrus at 12-h intervals for at least 5 d post injection. Cows observed in standing estrus were inseminated 12 to 18 h later. There was a location effect on response to treatment that was attributed to differences in body condition score between locations so data were analyzed within a location. Body condition score at the CSU location was 5.7 compared with 4.0 at the ECRC location. The CSU MGA-PGF2alpha treated cows had higher (P < 0.05) 5-day estrus and 5-d pregnancy rates (78.6 and 61.0%, respectively) than the CSU controls (11.1 and 6.9%, respectively). Similar results for 5-d estrus and pregnancy rates but of decreased magnitude were also observed for the ECRC MGA-PGF2alpha treated (31.6 and 21.4%, respectively) cows compared with that of the ECRC controls (11.9 and 8.5%, respectively). The CSU MGA-PGF2alpha treated cows had higher (P < 0.05) 25- and 60-d pregnancy rates (82.5 and 94.8%) than the CSU controls (65.3 and 87.5%). The 25- and 60-d pregnancy rates were similar between the ECRC MGA-PGF2alpha treated cows and ECRC control cows. The MGA-PGF2alpha estrus synchronization system appears to contribute to pregnancy early in the breeding season in postpartum beef cows, although its effectiveness is limited by cow body condition.

Comparison of two MGA-PGF2α systems for synchronization of estrus in beef heifers

Yearling beef heifers (n=193) were used to evaluate reproductive performance attained with 2 MGA-PGF2alpha synchronization systems. These treatments were compared with an untreated control group. The 14-d MGA heifers were synchronized by feeding 0.5 mg MGA/h/d for 14 d. At 17 d after the last MGA feeding, these heifers were injected with PGF2alpha (25 mg, im). Heifers in the 7-d MGA treatment group were fed 0.5 mg MGA/h/d for 7 d and received a 25-mg, im injection of PGF2alpha on the last day of the MGA feeding period. Heifers in all 3 treatment groups were observed for estrus every 12 h for 7 d beginning 24 h after the PGF2alpha injection. Heifers observed in estrus during this 7-d period were artificially inseminated approximately 12 h after the onset of estrus. The percentages of heifers in estrus during the 7-d synchronized period were 75.4, 56.3 and 17.2% for the 14-d MGA, 7-d MGA and control groups, respectively. The estrous responses were significantly different in each treatment. The percentage of heifers in estrus during the peak 24-h period was higher (P<0.05) in heifers synchronized with the 14-d MGA system than in heifers synchronized with the 7-d MGA system (75.5 vs 50.0%). The synchronized conception rate of the 14-d MGA heifers was significantly higher (65.3%) than that of both the 7-d MGA (41.7%) and control (45.4%) heifers. Synchronized conception rates were similar (P=0.79) in the 7-d MGA and control treatments. Synchronized pregnancy rates were 55.2, 32.4 and 15.2% for the 14-d MGA, 7-d MGA and control groups, respectively. Both synchronization treatments resulted in significantly higher synchronized pregnancy rates compared with that of the controls. The synchronized pregnancy rate was higher (P<0.05) in the 14-d MGA group than it was in the 7-d MGA group. The mean day of conception within the breeding season was 11.5 and 9.3 d shorter in the 14-d MGA heifers than in the 7-d MGA and control heifers, respectively. Our results indicate that using the 14-d MGA system to synchronize estrus in beef heifers results in better reproductive performance than that attained in heifers synchronized with the 7-d MGA system or in control heifers.