• Journal of Veterinary Clinics
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• v.35 no.6
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• pp.251-257
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• 2018

We determined the relationships between calving season and the incidence of postpartum disorders, milk yield, and reproductive performance in dairy cows. Data regarding cow parity, postpartum disorders, milk yield, and reproduction were collected from 1,478 lactations. The incidence of retained placenta was higher in spring- and summer-calving cows than in autumn- and winter-calving cows (P < 0.05). The incidence of septicemic metritis was highest in spring- and summer-calving cows, and was higher in autumn-calving cows than in winter-calving cows (P < 0.05). The incidence of metabolic disorders was higher in summer-calving cows than in autumn- and winter-calving cows (P < 0.01). The mean milk yield 1 and 2 months after calving was higher in spring-calving cows than in summer-calving cows (P < 0.05). The percentage of cows that had resumed cycling, defined by detection of a corpus luteum using ultrasonography 4 weeks after calving, was highest in autumn-calving cows, and was higher in summer- and winter-calving cows than in spring-calving cows (P < 0.05). The hazard of first insemination by 150 days after calving was higher in summer- and autumn-calving cows (hazard ratio [HR] = 1.19; P < 0.05) than in spring-calving cows. The hazard of pregnancy by 210 days after calving was also higher in summer-calving (HR = 1.24; P < 0.05) and autumn-calving (HR = 1.59; P < 0.0001) cows than in spring-calving cows. The probability of conception at the first insemination was higher (P < 0.0001) in autumn-calving (odds ratio [OR] = 1.96) and winter-calving (OR = 2.04) cows than in spring-calving cows. In conclusion, spring calving is associated with the worst, and autumn calving with the best, postpartum health and reproductive performance, whereas milk yield is higher in spring-calving cows than in summer-calving cows. Therefore, an effective strategy to support postpartum health and fertility should be instituted for spring-calving dairy cows kept in the Korean climate.

• Asian-Australasian Journal of Animal Sciences
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• v.10 no.3
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• pp.313-317
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• 1997

Data collected from crossbred dairy cattle at the Institut Haiwan, Kluang, were used to evaluate the effects of breed of sire, percentage of Bos taurus inheritance and season of birth on some calving traits. Breed of sire effect was significant on age at first service (p < 0.01), age at first calving (p < 0.01) and postpartum interval to first service (p < 0.05) but not on calving interval (p > 0.05). Linear contrasts indicate that crossbred-sired cows had first service 593 days earlier and first calving 508 days earlier than purebred-sired cows. Cows sired by Friesians, however, had the earliest first service (466 days) and were among the earliest at first calving (917 days). However, the crossbred-sired cows had slightly longer post-partum interval to first service (13 days longer) and calving interval (20 days longer). Percentage of B. taurus inheritance affected (p < 0.01) all the calving traits studied. In general, the cows with 50% inheritance had the best calving performance. Season of birth had no effect (p > 0.05) on them.

• Journal of Embryo Transfer
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• v.27 no.2
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• pp.87-92
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• 2012

A study on estrus synchronized dairy cows using progesterone intravaginal device was done to classify each cow's reproductive status from calving to synchronization and to evaluate the reproductive performance according to ovarian and uterine status, and calving season. From calving to estrus synchronization, silent heat or error of estrus detection among ovarian status and endometritis among uterine disorders were exposed in the most distribution (75.4% and 48.3%, respectively). The pregnancy rate of cows with inactive ovaries was lower than those in the follicular and luteal phase. And according to the uterine status before estrus synchronization, the pregnancy rate was similar in three groups; normal, endometritis, and pyometra (70.9, 69.1 and 100%, respectively). The interval from calving to conception was shorter (p<0.05) in cows calved during autumn than in cows calved during spring and winter.

• Journal of Embryo Transfer
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• v.24 no.2
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• pp.127-130
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• 2009

The purpose of this study was to determine the effect of cows parity and calving seasons on the subsequent reproductive performance of the herd of Korean native cows raised under the same condition. With the parity of the cows ranged 1 to 4 (mean: 1.9), significant associations were found between parity and calving interval (p<0.05). Calving interval of the primiparous cows group was 395.0 ${\pm}$ 16.5 days, which was the longest calving interval among the four groups. On the other hand, calving interval of the second parity group was 333.7 ${\pm}$ 3.6 days. The primiparous cows had tendencies that long interval from calving to conception and small number of service per conception relatively when compared with the multiparous cows. In the case of calving season, the interval from calving to first service was short in summer and winter relatively. The interval from calving to conception in summer was the shortest in four seasons. The number of service per conception was larger in spring and winter and smaller in summer and autumn. Calving in spring showed delayed reproductive performance and calving in summer showed desirable reproductive performance.

• Journal of Animal Science and Technology
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• v.58 no.2
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• pp.8.1-8.14
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• 2016

In this research data representing 72,946 primiparous cows from 724 herds with 638,063 total test day records calved between 2001 and 2011. These data were analysed to determine the effect of age at first and season of calving on parameters of the Wood lactation curve. Also, genetic trend of the lactation curve parameters in different calving years were evaluated. The results indicate that the highest rate of atypical lactation curve was related to cows that calved in summer (28.05 %). The maximum phenotypic relationship between initial milk yield and total 305-d milk yield was observed in cows calved in spring (0.40). The role of peak yield is more than peak time on 305-d total milk yield in primiparous Holstein. One month increase in age at first calving from 18 to 26 month raised 305-d milk yield by around 138 kg and from 27 to 32 month decreased by 61 kg. The persistency of lactation between 101 and 200 days is higher than that of 201-305 days. Our results indicate that the shape of lactation curve is largely dependent on the season of calving (higher level of milk production in cows which calved in autumn and winter). The heritabilities of parameters of lactation curve and persistency measures were low. The genetic trends for peak time, peak yield and 305-d milk yields were positive and estimated to be 0.019, 0.021 and 8.13 kg/year respectively. So the range from 24 to 26.5 month of calving is the optimum calving time in primiparous Holstein for maximizing 305-d milk yield.

• Asian-Australasian Journal of Animal Sciences
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• v.9 no.5
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• pp.503-508
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• 1996

The data analysed consisted of records on lactation length (LL), total lactation yield (TLY), estimated 305-day yield (305 DY), days dry (DDRY), age at frist calving (AFC) and calving interval (CI) of 448 Friesian $\times$ Bunaji halfbreds that calved over a twenty-three year period (1967-1989) at the National Animal Production Research Institute, Shika, Nigeria. Least squares means of LL, TLY, 305DY, DDRY, AFC and CI were 250 days, 1,988 kg, 2,420 kg, 102 days, 35 months and 390 days, respectively. Parity, season and year of calving significantly affected LL, TLY (p < 0.01) and 350DY (p < 0.05), but not CI. DDRY was affected by season of calving only (p < 0.05). It was therefore concluded that the Shika Friesian $\times$ Bunaji crossbreeding programme was successful and beneficial in that the $F_1$ crosses calved at a younger age, produced twice as much milk, had longer lactations and slightly shorter calving intervals than the indigenous Bunaji.

• Asian-Australasian Journal of Animal Sciences
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• v.12 no.7
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• pp.1019-1024
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• 1999

Fifth one Nili-Ravi dairy buffaloes were studied in North-west Frontier Province of Pakistan. Rectal examination of reproductive organs was carried out on days 14 and 21 and then fortnightly. Milk samples were collected and analyzed for progesterone levels (MPL). Feed samples were collected fortnightly and analyzed. The buffaloes calving during the normal breeding season (NBS, August to January) (p<0.01) postpartum estrus interval of 55.95 days versus 91.15 days in those calving during the low breeding season (LBS, February to July). MPL in the LBS remained lower than the NBS (p<0.01). Shortest postpartum ovulation interval was noted during autumn(August to October), followed by winter (November to January), summer (May to July) and spring (February to April). The incidence of silent ovulations was during LBS than NBS (70.6% versus 29.4%). In autumn there was minimum intake of crude protein (CPI) and maximum intake of metabolizable energy (MEI, p<0.01). Calcium intake was higher in NBS than LBS calving buffaloes (p<0.01). Phosphorus, copper and magnesium intake was lower (p<0.05) and zinc intake was higher (p<0.01) in autumn, It was (p<0.05) and zinc intake was higher (p<0.01) in autumn, It was concluded that onset of breeding season was associated with increasing MEI and decreasing CPI and minerals intake.

• Asian-Australasian Journal of Animal Sciences
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• v.33 no.12
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• pp.1922-1929
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• 2020

Objective: The present study aimed to survey seasonal changes in reproductive performance of local cows receiving artificial insemination (AI) in the Pursat province of Cambodia, a tropical country, to investigate if ambient conditions affect the reproductive performance of cows as to better understand the major problems regarding cattle production. Methods: The number of cows receiving AI, resultant number of calving, and calving rate were analyzed for those receiving the first AI from 2016 to 2017. The year was divided into three seasons: cool/dry (from November to February), hot/dry (from March to June), and wet (from July to October), based on the maximal temperature and rainfall in Pursat, to analyze the relationship between ambient conditions and the reproductive performance of cows. Body condition scores (BCS) and feeding schemes were also analyzed in these seasons. Results: The number of cows receiving AI was significantly higher in the cool/dry season than the wet season. The number of calving and calving rate were significantly higher in cows receiving AI in the cool/dry season compared with the hot/dry and wet seasons. The cows showed higher BCSs in the cool/dry season compared to the hot/dry and wet seasons probably due to the seasonal changes in the feeding schemes: these cows grazed on wild grasses in the cool/dry season but fed with a limited amount of grasses and straw in the hot/dry and wet seasons. Conclusion: The present study suggests that the low number of cows receiving AI, low number of calving, and low calving rate could be mainly due to poor body condition as a result of the poor feeding schemes during the hot/dry and wet seasons. The improvement of body condition by the refinement of feeding schemes may contribute to an increase in the reproductive performance in cows during the hot/dry and wet seasons in Cambodia.

• Asian-Australasian Journal of Animal Sciences
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• v.17 no.2
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• pp.153-158
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• 2004

Data containing 14,188 lactation and reproductive records of Korean Holstein cows at first parity distributed across 3,734 herd-year-season groups were analyzed to get genetic (co)variance estimates for milk yield, fat yield, calving ease, and days open. Milk and Fat yields were adjusted to 305 d. Heritabilities and genetic correlations were estimated in two different animal models on which were included direct genetic effects (Model 1) and direct+maternal genetic effects (Model 2) using REML algorithms. Milk and fat yields were affected by age at first calving as linear and quadratic. Heritability estimates of direct effects were 0.25 for milk yield, 0.17 for fat yield, 0.03 for calving ease and 0.03 for days open in Model 2. These estimates for maternal effects were 0.05, 0.08, 0.04 and less than 0.01 for each corresponding trait. Milk productions at first lactation were to show genetically favorable correlation with calving ease and days open for direct genetic effects (-0.24 - -0.11). Moreover, calving ease was correlated with days open of 0.30 for direct genetic effects. Correlations between direct and maternal effects for each trait were negatively correlated (-0.63 - -0.32). This study suggested that maternal additive genetic variance would be not ignorable for genetic evaluation of milk production as well as reproductive traits such as calving ease and days open at first parity. Furthermore, difficult calving would genetically influence the next conception.

• Asian-Australasian Journal of Animal Sciences
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• v.19 no.5
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• pp.672-678
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• 2006

The objective of this study was to investigate whether milk performance is impacted by the housing of heifers from the second to the seventh day of life, the method of feeding milk from the second week of life to weaning, the sire lineage and by the season of birth and season of calving. From 32 Holstein heifer-calves, which spent their first day of life in a loose housing maternity pen with their mother, 19 heifers were randomly placed in hutches (IH), and 13 stayed in a loose housing maternity pen (MP). At the seventh day IH heifers were assigned to one of two treatments, 10 heifers were randomly taken from IH and relocated to a loose housing pen with an automatic feeding station (AD), 9 calves stayed in hutches with bucket drinking (BD). MP heifers were moved to a group pen with nursing cows (UD). All animals were weaned at the age of 8 weeks (56 days) and kept in group pens. After calving, they were in free-stall housing. Trial cows were divided according to the sire, season of birth and calving. The five-factorial ANOVA revealed that among all the factors taken into account in this study, only sire lineage and season of birth had significant effects. The production of milk, FCM and protein were higher in the MP group than in the IH group. The UD group tended to have the highest production of milk, FCM, protein, lactose, SNF and total solids (TS) and the AD group the lowest. The content of fat and TS were highest in the AD group. Effects of the sire were significant for average daily gains (ADG) from birth to weaning ($0.55{\pm}0.03kg$, p<0.05), contents of fat ($3.81{\pm}0.08%$, p<0.05), protein ($3.13{\pm}0.02%$, p<0.05), and TS ($12.67{\pm}0.12%$, p<0.05). In the season of birth evaluation, statistical difference was found only in the content of protein ($3.13{\pm}0.13%$, p<0.05). Cows born in March-May had the highest % protein and cows born in June-August the lowest ($3.21{\pm}0.04$ vs. $3.06{\pm}0.05%$). Dairy cows born and subsequently calving in December-February had the highest production of milk, protein and TS, and dairy cows born in June-August the lowest. FCM and fat yields were highest in the group born in September-November and lowest in the group born in June-August.