نوع مقاله : مقاله پژوهشی
نویسندگان
1 گروه علوم دامی، دانشکده کشاورزی، دانشگاه شهرکرد، شهرکرد، ایران
2 گروه علوم دامی، دانشکده کشاورزی، دانشگاه شهرکرد، شهرکرد، ایران.
3 گروه علوم دامی، مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان چهارمحال و بختیاری، سازمان تحقیقات، آموزش و ترویج کشاورزی، شهرکرد،
چکیده
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
The purpose of the current study was to investigate the effect of gestation length (GL) on productive performance of Holstein dairy cows and the health of calves. In total, 3,780 Holstein singleton cows (1,994 heifers and 1,786 cows) from two commercial dairy farms were used. The mean of GL for 3,780 cows was 276 ± 5 d, and cows were classified as short (SGL; more than 1SD less than the population mean, mean = 267, range 258 to 270 d), average (AGL; population mean ± 1SD, mean = 276, range 271 to 281 d), and long (LGL; more than 1SD greater than the population mean, mean = 284, range 282 to 294 d) gestation length. In primiparous cows, milk yield was not different across groups. However, in multiparous cows, the SGL cows had lower milk yield than the AGL cows. In both primiparous and multiparous cows, calf birth weight was lower in SGL group than AGL group, but the LGL group had higher calf birth weight than AGL group. The incidence of pneumonia and diarrhea of calf were not affected by the GL. In general, cows with short GL had lower productive performance and calf birth weight, but the incidence of pneumonia and diarrhea of the calf were similar among groups.
کلیدواژه‌ها [English]
Extended Abstract
Introduction
Gestation length (GL) defines as the days from confirmed conception to calving. Determining the expected GL is crucial for management decisions such as drying off, movement between groups, and nutritional grouping. The GL is affected by several known factors such as genetics, the sex of the calf, the age of the dam, the season of the year, and singleton or twin pregnancy. The abnormal GL is associated with harmful effects on the productive performance and health of cows, and the survival of the offsprings. It has been reported that cows within the 5% shortest and the 5% longest GL of the study population produced less milk, fat, and protein, and had impaired offspring survival. Likewise, cows with GL 281 d had increased incidence of dystocia and stillbirth compared with cows with GL between 275 and 281 d. Therefore, a better understanding of the potential effects of gestation length on health, reproduction, and productive performance of dairy cows and its long-term effects on health and survival of offspring may provide information that can be used for better management of cows and calves.The purpose of this study was to determine the optimal and abnormal gestation length and to investigate its effects on milk yield and composition in dairy cows and the health of Holstein calves.
Materials and Methods
In total, 3,780 Holstein singleton cows (1,994 heifers and 1,786 cows) from two commercial dairy farms were used. The mean of GL for 3,780 cows was 276 ± 5 d, which were classified as short (SGL; more than 1SD less than the population mean, mean = 267, range 258 to 270 d), average (AGL; population mean ± 1SD, mean = 276, range 271 to 281 d), and long (LGL; more than 1SD greater than the population mean, mean = 284, range 282 to 294 d) gestation length. Data regarding milk production and composition were collected from the dairy management software. Information about cows such as lactation period, type of calving (single or twin) and calving season were recorded. In both farms, the sex (male or female) and weight of the calves was determined immediately after birth. Calf diseases such as diarrhea (fecal score ≥ 2 (Renaud et al., 2019); fecal score of 0 (normal consistency to feces), 1 (semiformed or pasty feces), 2 (runny, spreads easily), and 3 (liquid, devoid of solid material) and pneumonia (fever, cough, ocular or nasal discharge, abnormal breathing, and auscultation of abnormal lung sounds; McGuirk & Peek, 2014) were recorded until weaning.
Results and Discussion
The interaction of GL by parity on milk yield tended to be significant (p = 0.09), as in primiparous cows, milk yield was not different across groups (p > 0.05), but in multiparous cows, the SGL cows had lower milk yield than the AGL cows (p < 0.01). Milk fat, protein, and SCC content were not affected by the GL and the interaction of GL by prity (p > 0.15). In both primiparous and multiparous cows, calf birth weight was lower in SGL group than AGL group, but the LGL group had higher calf birth weight than AGL group (p < 0.01). The incidence of pneumonia and diarrhea of calf were not affected by the GL and the interaction of GL by prity (p> 0.15). The short GL in multiparous cows may have implications for the length of the dry period and exposure of the transition cows to dietary manipulations. A quadratic correlation between prepartum days (7, 28, and 42 d) and milk production has been reported (Vieira-Neto et al., 2021), indicating that the optimal duration of exposure to the prepartum diet is 21 to 28 d, and short-term (7 d) or long-term (42 d) feeding of prepartum diets is associated with detrimental effects on postpartum performance. Additionally, it has been shown that increasing days of exposure of cows to prepartum diets was associated with increased milk yield corrected for fat and protein, reaching a plateau at about 28 d (Degaris et al., 2008). The results of these researchers support our results in reducing milk yield of SGL group and no change in milk yield of LGL group compared to AGL. Long-term feeding of prepartum diets in the LGL group may partition more nutrients to the conceptus and developing fetus, resulting in greater fetal growth and larger calves.
Conclusion
In general, cows with short GL had lower productive performance and calf birth weight, but the incidence of pneumonia and diarrhea of the calf were similar among groups.
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