This retrospective study evaluated the effect of age at first calving on the productive and reproductive performance in Holstein dairy cattle. Data were collected on 2,297 lactations from 19 dairy farms, including dates of birth, insemination, pregnancy, calving, and lactation and milk production (3...
This retrospective study evaluated the effect of age at first calving on the productive and reproductive performance in Holstein dairy cattle. Data were collected on 2,297 lactations from 19 dairy farms, including dates of birth, insemination, pregnancy, calving, and lactation and milk production (305-day milk yield at first lactation and lifetime milk yield). Lactation data were grouped based on age at first calving into the early (< 24 months, n = 414), moderate (24 ${\leq}$ and ${\leq}$ 28 months, n = 1,268), and late (> 28 months, n = 615) groups. The 305-day milk yield at first lactation was higher (p < 0.005) in the late group (8,461.9 kg) than in the early (8,130.8 kg) and moderate (8,261.9 kg) groups. Lifetime days in milk were shorter (p < 0.01) in the early group (1,045.7) than in the moderate (1,143.1) and late (1,110.7) groups, whereas the lifetime milk yield was higher (p < 0.05) in the moderate group (34,171.8 kg) than in the early group (31,791.6 kg). The second calving interval (days) differed (p < 0.0001) between the early (416.9), moderate (438.9), and late (455.3) groups. The culling rate at the first and second lactations tended to be higher (p = 0.08) in the early group (31.2%) than in the moderate group (26.0%), whereas it was intermediate in the late group (29.3%). In conclusion, dairy heifers aged 24-28 months at first calving showed a higher productive performance through an increased lifetime milk yield and a decreased culling rate.
This retrospective study evaluated the effect of age at first calving on the productive and reproductive performance in Holstein dairy cattle. Data were collected on 2,297 lactations from 19 dairy farms, including dates of birth, insemination, pregnancy, calving, and lactation and milk production (305-day milk yield at first lactation and lifetime milk yield). Lactation data were grouped based on age at first calving into the early (< 24 months, n = 414), moderate (24 ${\leq}$ and ${\leq}$ 28 months, n = 1,268), and late (> 28 months, n = 615) groups. The 305-day milk yield at first lactation was higher (p < 0.005) in the late group (8,461.9 kg) than in the early (8,130.8 kg) and moderate (8,261.9 kg) groups. Lifetime days in milk were shorter (p < 0.01) in the early group (1,045.7) than in the moderate (1,143.1) and late (1,110.7) groups, whereas the lifetime milk yield was higher (p < 0.05) in the moderate group (34,171.8 kg) than in the early group (31,791.6 kg). The second calving interval (days) differed (p < 0.0001) between the early (416.9), moderate (438.9), and late (455.3) groups. The culling rate at the first and second lactations tended to be higher (p = 0.08) in the early group (31.2%) than in the moderate group (26.0%), whereas it was intermediate in the late group (29.3%). In conclusion, dairy heifers aged 24-28 months at first calving showed a higher productive performance through an increased lifetime milk yield and a decreased culling rate.
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문제 정의
Thus, establishment of the optimal age at first calving, which may affect subsequent milk production, productive life, reproduction, and culling, is required to maximize net returns in dairy farms. Therefore, the objective of the present study was to determine the effect of age at first calving on the productive and reproductive performance in Holstein dairy cattle.
This study evaluated the effect of age at first calving on the productive and reproductive performance in Holstein dairy cattle. Cows calving at a young age (< 24 months) had a low lifetime milk yield but a shorter second calving interval, whereas cows calving at an old age (> 28 months) had a longer second calving interval than cows calving at a moderate age (24 ≤ and ≤ 28 months).
제안 방법
Data were collected from 2,297 heifers, which had calved from January 2005 to September 2014, on 19 dairy farms. These data included detailed information on dates of birth, insemination, pregnancy, calving, and lactation and milk production (305-day milk yield at first lactation and lifetime milk yield). All the data were collected from the Korean Animal Improvement Association.
Lactation data were grouped based on age at first calving into the early (< 24 months, n = 414), moderate (24 ≤ and ≤ 28 months, n = 1,268), and late (> 28 months, n = 615) groups. This study compared the 305-day milk yield at first lactation, lifetime days in milk (DIM), lifetime milk yield, second calving interval (days), and culling rate at the first and second lactations between the three groups.
대상 데이터
Data were collected from 2,297 heifers, which had calved from January 2005 to September 2014, on 19 dairy farms. These data included detailed information on dates of birth, insemination, pregnancy, calving, and lactation and milk production (305-day milk yield at first lactation and lifetime milk yield).
This study was conducted on 19 dairy farms in Chungcheong Province. The cows were maintained in a loose housing system, fed a total mixed ration, and milked twice daily.
데이터처리
Statistical analysis of 305-day milk yield at first lactation, lifetime DIM, lifetime milk yield, and second calving interval (days) was carried out using an analysis of variance followed by Duncan’s multiple range tests.
이론/모형
Statistical analysis of 305-day milk yield at first lactation, lifetime DIM, lifetime milk yield, and second calving interval (days) was carried out using an analysis of variance followed by Duncan’s multiple range tests. The culling rate was compared using the Chi-squared test. A p-value ≤ 0.
성능/효과
Our results described above showed that cows that first calved at a young age (< 24 months) had a low lifetime milk yield, whereas cows that first calved at an older age (> 28 months) had a longer second calving interval than cows that first calved at a moderate age (24 ≤ and ≤ 28 months).
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