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Genetic and environmental factors that might affect gestation length (GL) were investigated. Data included information from >11million parturitions from 1999 through 2006 for 7 US dairy breeds. Effects examined were year, herd-year, month, and age within parity of conception; parturition code (sex and multiple-birth status); lactation length and standardized milk yield of cow; service sire; cow sire; and cow. All effects were fixed except for service sire, cow sire, and cow. Mean GL for heifers and cows, respectively, were 277.8 and 279.4 d for Holsteins, 278.4 and 280.0 d for Jerseys, 279.3 and 281.1 d for Milking Shorthorns, 281.6 and 281.7 d for Ayrshires, 284.8 and 285.7 d for Guernseys, and 287.2 and 287.5 d for Brown Swiss. Estimated standard deviations of GL were greatly affected by data restrictions but generally were approximately 5 to 6 d. Year effects on GL were extremely small, but month effects were moderate. For Holstein cows, GL was 2.0 d shorter for October conceptions than for January and February conceptions; 4.7 and 5.6 d shorter for multiple births of the same sex than for single-birth females and males, respectively; 0.8 d longer for lactations of ≤250 d than for lactations of ≥501 d; and 0.6 d shorter for standardized yield of ≤8,000kg than for yield of ≥14,001kg. Estimates for GL heritability from parities 2 to 5 were 33 to 36% for service sire and 7 to 12% for cow sire; corresponding estimates from parity 1 were 46 to 47% and 10 to 12%. Estimates of genetic correlations between effects of service sire and cow sire on GL were 0.70 to 0.85 for Brown Swiss, Holsteins, and Jerseys, which indicates that those traits likely are controlled by many of the same genes and can be used to evaluate each other. More accurate prediction of calving dates can help dairy producers to meet management requirements of pregnant animals and to administer better health care during high-risk phases of animals’ lives. However, intentional selection for either shorter or longer GL is not recommended without consideration of its possible effect on other dependent traits (e.g., calving ease and stillbirth).

The objectives were to evaluate the impact of conventional or intensive milk replacer (MR) feeding programs on heifer calf performance through 6 mo of age, age at first calving, and first lactation performance. At 3 (±1 d) d of age, 133 Holstein heifer calves from 3 commercial dairy farms were randomly assigned, within calf source, to a conventional [20% crude protein (CP), 20% fat] or intensive MR (28% CP, 18% fat). Milk replacer treatments and percent solids were 1) conventional nonacidified (CNA), 13.9%; 2) conventional acidified (CA), 13.9%; 3) modified intensive high solids (IHS), 16.7%; 4) modified intensive low solids (ILS), 12.5%; and 5) intensive high solids, high feeding (IHSHF), 16.7%. Calves were individually housed and remained on trial for 56 d. At 2 mo of age, heifers were grouped in pens by treatment with 6 heifers per pen (4 pens per treatment). An 18.1% CP grower concentrate mix (dry matter basis) was fed to heifers that received a conventional MR and a 21.2% CP grower concentrate mix was fed to heifers that received the intensive MR preweaning. Heifers were offered 2.45kg/d (dry matter basis) of their respective grower concentrate mix for 112 d plus free access to hay and water. At approximately 24 wk of age, heifers were transported to a second-stage grower before returning to their respective farms approximately 1 mo before calving. First-lactation performance was determined using Dairy Herd Improvement Association records. The IHSHF treatment resulted in increased calf body weight and hip height during the preweaning and early postweaning (PEP) period and the postweaning heifer grower (PHG) period as compared with the conventional (CNA and CA) or modified intensive MR treatments (IHS and ILS). Calves receiving the IHS treatment were heavier at d 56 of the PEP period compared with the conventional or ILS treatments; however, this growth advantage was not maintained in the PHG period. Feed cost per kilogram of gain during the PEP period was lowest for CNA and CA, intermediate for IHS and ILS, and highest for the IHSHF treatment. There was no effect of MR feeding program on first-lactation performance; however, heifers that received the IHSHF MR preweaning calved 27.5 d earlier than those fed a conventional MR.

The objectives of this study were: 1) to determine the effect of providing additional prepartum concentrate on the occurrence and severity of ruminal acidosis (RA) and lactational performance during the periparturient period in primiparous cows; and 2) to characterize the occurrence and severity of RA during the periparturient period. We hypothesized that providing additional concentrate prepartum would reduce postpartum RA. Fourteen ruminally cannulated Holstein heifers were paired by expected calving date and body condition score. The heifers were assigned to 1 of 2 prepartum feeding regimens: 1) a control treatment consisting of a far-off diet (forage:concentrate, F:C=80:20) fed from d −60 to d −25 and a close-up diet (F:C=54:46) fed from d −24 until parturition; or 2) a high-concentrate (HC) feeding program consisting of 4 prepartum diets, HC-1 (F:C=68:32) fed from d −60 to d −43, HC-2 (F:C=60:40) fed from d −42 to d −25, HC-3 (F:C=52:48) fed from d −24 to d −13, and HC-4 (F:C=46:54) fed from d −12 until parturition. All cows received the same lactation diet postpartum. Ruminal pH was measured continuously from d −5 to d +5, and for 3 consecutive days starting on d +17±1.2, d +37±1.4, and d +58±1.5 relative to parturition using an indwelling ruminal pH system. Ruminal acidosis was considered to occur when ruminal pH was <5.8 (total RA). Ruminal acidosis was further partitioned into: 1) mild RA (5.8>ruminal pH>5.5), 2) moderate RA (5.5>ruminal pH>5.2), and 3) acute RA (ruminal pH<5.2). Feeding additional concentrate prepartum did not reduce postpartum RA. In fact, cows fed the HC treatment had more daily episodes of acute RA than cows fed the control treatment. Day relative to parturition affected the occurrence and severity of RA; RA increased following parturition and was sustained thereafter. The DM intake during the last 5 d of gestation was lower for cows fed the HC treatment compared with cows fed the control treatment, but lactational performance was not affected. We conclude that, under the conditions imposed, feeding additional concentrate prepartum does not reduce postpartum RA. Furthermore, the incidence and severity of RA increases immediately postpartum, emphasizing the need to develop and implement feeding strategies that reduce this risk.

A 3-yr study was conducted with heifers (n = 170) whose dams were used in a 2 x 2 factorial arrangement of treatments to determine the effects of late gestation (LG) or early lactation (EL) dam nutrition on subsequent heifer growth and reproduction. In LG, cows received 0.45 kg/d of a 42% CP supplement (PS) or no supplement (NS) while grazing dormant Sandhills range. During EL, cows from each late gestational treatment were fed cool-season grass hay or grazed sub-irrigated meadow. Cows were managed as a single herd for the remainder of the year. Birth date and birth weight of heifer calves were not affected (P > 0.10) by dam nutrition. Meadow grazing and PS increased (P = 0.02; P = 0.07) heifer 205-d BW vs. feeding hay and NS, respectively. Weight at prebreeding and pregnancy diagnosis were greater (P < 0.04) for heifers from PS dams but were unaffected by EL nutrition (P > 0.10). There was no effect (P > 0.10) of LG or EL dam nutrition on age at puberty or the percentage of heifers cycling before breeding. There was no difference (P > 0.10) in pregnancy rates due to EL treatment. Pregnancy rates were greater (P = 0.05) for heifers from PS dams, and a greater proportion (P = 0.005) of heifers from PS dams calved in the first 21 d of the heifers' first calving season. Nutrition of the dams did not influence (P < 0.10) heifers' average calving date, calving difficulty, and calf birth weight during the initial calving season. Weight at the beginning of the second breeding season was greater (P = 0.005) for heifers from PS dams but was not affected by maternal nutrition during EL (P > 0.10). Dam nutrition did not affect (P > 0.10) heifer ADG or G:F ratio. Heifers from PS dams had greater DMI (P = 0.09) and residual feed intake (P = 0.07) than heifers from NS cows if their dams were fed hay during EL but not if their dams grazed meadows. Heifers born to PS cows were heavier at weaning, prebreeding, first pregnancy diagnosis, and before their second breeding season. Heifers from cows that grazed meadows during EL were heavier at weaning but not postweaning. Despite similar ages at puberty and similar proportions of heifers cycling before the breeding season, a greater proportion of heifers from PS dams calved in the first 21 d of the heifers' first calving season, and pregnancy rates were greater compared with heifers from NS dams. Collectively, these results provide evidence of a fetal programming effect on heifer postweaning BW and fertility.

Potential variables for the reproductive success of beef cows were evaluated. Included in the model were the age of the cow at calving; the interval between the Julian calving date and the end of the breeding season; the body weight and conditions at calving, at 75 days post-partum and at the end of the breeding season; and the mean daily variation in weight between these dates. Logistic regression was used in the analysis, with the parameters evaluated using the odds ratio statistic, estimating the chance of pregnancy. The mean rate of pregnancy was 84% and 55% for early and late-weaned cows, respectively. For early weaned cows, the regression variables were the Julian calving date, age of the cow, weight gain from calving to 75 days post-partum, and from 75 days post-partum to the end of the reproductive period. For late-weaned cows, there were only two regression variables, weight at calving and weight gain from calving to the end of the reproductive period. For every year above the average age of the herd, early weaned cows have an 80.9% greater chance of pregnancy, while a reduction of one year reduces the chance of pregnancy by 44.7%. In early weaned cows, every seven days after the mean Julian calving date reduces the chances of pregnancy by 22.6%, whereas every seven days before the mean calving date increases pregnancy by 29.2%. Greater gains in cow body weight, from calving to the end of the reproductive period, determine a greater probability of pregnancy.

The objectives were to describe culling patterns and reasons for culling across lactation, estimate mortality and the proportion of cows leaving from 21 d before an expected calving date through 60 d in milk (DIM; CULL60) for Pennsylvania (PA) dairy herds, and to describe production measures for herds with high and low mortality and CULL60. Weekly culling frequencies and reasons for culling from 3 wk before a reported expected calving date through ≥100 wk of lactation were calculated for all PA cows with at least 1 Dairy Herd Improvement test in 2005. It was estimated that at least 5.0% of PA dairy cows died in 2005, and that at least 7.6% were culled by 60 DIM. The majority of cows exiting the herd by 60 DIM either died (35.1%) or had a disposal code of injury/other (29.9%). A total of 137,951 test-day records from 20,864 cows in herds with high mortality (>8.0%) and CULL60 (>12.0%) and 136,906 test-day records from 12,993 cows in herds with low mortality (<1.4%) and CULL60 (<2.9%) were retained to describe differences among herds with high and low survival. Least squares means for weekly milk yield, fat and protein percentages, and somatic cell score (SCS) were estimated with a model that included fixed effects for herd environment (high or low survival) and week nested within herd environment and lactation; random effects were cow, herd-test-day, and error. Cows from herds with high mortality and CULL60 produced more milk in lactations 1 (+1.9±0.15 kg/d) and 2 (+0.9±0.16 kg/d), but less in lactations 4 (−0.7±0.22 kg/d), 5 (−1.4±0.29 kg/d), and ≥6 (−0.7±0.32 kg/d) and had higher SCS (+0.24±0.02), more change in early-lactation fat percentage (−1.77% vs. −1.59%), and a greater frequency of fat-protein inversions (3.6±0.3%). There is an opportunity to manipulate management practices to reduce mortality and early-lactation culling rates, which will improve cow welfare and the efficiency of dairy production by capturing a greater proportion of potential lactation milk yield, increasing cow salvage values, and reducing replacement costs.

Since mid-1980’s, the population of the Bathurst barren ground caribou (Rangifer tarandus) in Canada’s Arctic has declined by 93%. In order to develop and implement an effective recovery plan, it is important to know how various factors have cumulatively impacted the population decline. To contribute to the knowledge, we investigated the following two questions: how have changes in climate-induced habitat conditions impacted the peak calving date of the Bathurst caribou, and what was the implication of the impact on the population? Our results indicate that the peak calving date was impacted by changes in habitat conditions (e.g., the start date of vegetation growing season SOS) in a complex manner. Large inter-annual variations in SOS on the calving ground and summer range of the Bathurst herd were observed during 1985 and 2012, with the largest difference being 29 days. A 1-day delay of SOS in year i − 1 on the calving ground (SOScg(i − 1)) from its normal date could result in a 0.5-day delay in the peak calving date in year i, likely caused by the delay in the conception date in the previous fall. However, advances in SOScg(i − 1) did not alter the peak calving date in year i. Furthermore, a 1-day delay (or advance) in the current year’s SOS on the summer range (SOSsr(i)) might cause a 0.23-day delay (or advance) in the peak calving date in the current year, likely through changing the caribou’s gestation duration. Together SOScg(i − 1) and SOSsr(i) explained 69.1% of the variation in the peak calving date of the Bathurst caribou herd during 1985–2012, indicating the cumulative impacts on the peak calving date by the changing habitat conditions over a period of 2 years and thus the validation of the cumulative habitat impact hypothesis. Finally, our results also show that a 1-day delay in the peak calving date corresponded approximately 2–3% reduction in the birth rate of the Bathurst caribou, and thus might have been partially responsible for the population decline.

Because of difficulties in data collection and analysis, in most breeds there have been limited ways to evaluate fertility in females on a between-herd basis. The objective of this study was to determine the heritabilities (direct and maternal) for CD (calving day) and AFC (age at first calving) in American Angus heifers and to evaluate the potential for using these traits in genetic improvement of female fertility. Records (n = 2,082) from 2 herds were used. Calving day was defined as the calving date of a heifer minus the first calving date in her contemporary group. To avoid bias, noncalving heifers were assigned a penalty record CD of 30, 60, and 90 d after the last CD in that contemporary group. These assigned CD were also used to give open heifers a predicted AFC. Data were analyzed by MTDFREML using a general linear animal model. Fixed effects included herd-year, service sire of the heifer, and age of dam, and a covariate of age of the heifer at the start of the breeding season (for CD only). A model including a maternal effect was also analyzed. Heritabilities for CD using a direct model were 0.07 ± 0.04, 0.10 ± 0.05, and 0.11 ± 0.05, for each penalty adjustment, respectively. Average, minimum, and maximum estimated breeding values (in days) for sires of heifers for the 3 adjustments were -0.7, -10.6, and 9.8; -1.1, -17.2, and 16.5; and -1.6, -22.6, and 19.5. The estimates of heritability for AFC using a direct model did not differ for the different adjustments for penalty records and were 0.28 ± 0.06. Average, minimum, and maximum estimated breeding values (in days) for sires of heifers for the 3 adjustments were -0.6, -46.6, and 45.9; -1.2, -50.1, and 51.6; and -1.7, -52.9, and 56.7. In a direct-maternal model, direct heritabilities for CD decreased slightly, and for AFC increased to 0.66 ± 0.14. The maternal heritabilities and direct-maternal genetic correlations were 0.08 ± 0.05 and -0.18 ± 0.58 for CD, and 0.32 ± 0.08 and -0.85 ± 0.06 for AFC. Although AFC had a greater heritability and a wider range of breeding values than CD, the negative direct-maternal genetic correlation indicated that selecting on AFC may favor heifers that are themselves born later in the season. Therefore, CD may be more useful than AFC in selecting for female fertility in beef cattle.

Calving date affects feed costs, calf weaning weights, marketing dates, labor availability, and, potentially, calf health. Employing recent estimates of calf weaning weights and surveys of producers, feedlot operators, and veterinarians, we model expected profits as a function of calving date. January-calving herds had the highest annualized net returns, a result driven by older weaning dates and heavier weaning weights. However, survey results show March and April were the most common calving months. This may be due to both weather and labor demand concerns. If weaning ages are restricted to 205 days, January calving was the least profitable because of higher feed costs.

Udder health and milk production were monitored in cows transferred from tie stalls or loose housing with conventional milking to loose housing with either automatic or conventional milking. Data were collected from 182 Finnish farms from September 1999 to February 2006. Data from the first year before and first year after the changes were compared. A total of 88 herds changed from conventional milking (CM herds) to automatic milking (AM herds), 29 of which were housed in tie stalls and 59 of which were housed in a loose housing barn before the change. Additionally, 94 CM herds milked in loose housing barns that had been housed in tie stalls before the change were included. Milk record data consisted of annual herd size, parity, breed, calving dates, test day data [date, milk yield, and cow somatic cell count (SCC)] and records for treatments of clinical mastitis. Calculations were made for energy-corrected milk yield and logarithmic SCC (logSCC), proportion of cows at risk that experienced an SCC >200,000 cells/mL for the first time (highSCC), and number of treatments of clinical mastitis within a herd. Cows in tie stalls had higher milk yield (28.5±0.29 vs. 26.5±0.46 kg/d) and a lower logSCC (4.86±0.01 vs. 4.95±0.02) than cows in loose housing barns before the change. After the change, CM herds had slightly better udder health than AM herds because the proportion of cows at risk for highSCC was larger in AM herds (3.3 vs. 2.1%). The change in milking and housing systems caused a decline of 0.8±0.25 kg/d per cow in energy-corrected milk yield, a slight increase in cow logSCC (from 4.88±0.01 to 4.93±0.01), and an increase of 0.6% in the proportion of cows having highSCC (from 2.5 to 3.1). The impact was clearer on herds that began automatic milking. Based on the results, the increase in bulk milk SCC of herds milked automatically in Finland was probably due to reduced separation of mastitic milk in AM herds.