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Body Condition Score and Fertility

High milk production, whether achieved through genetic selection, enhanced nutrition, or improved management, is often implicated as the cause of health, fertility, and culling problems on modern dairy farms. However, a complex relationship exists between milk yield, health, and reproductive performance. High-producing cows tend to be more susceptible to metabolic disorders and infectious diseases, and these can lead to impaired fertility. On the other hand, healthy cows tend to have higher milk production and greater reproductive performance than unhealthy cows. Conversely, cows that remain nonpregnant for much of the lactation tend to achieve higher levels of total production because fewer resources are allocated to the developing calf. Thus, one must be cautious when attempting to formulate cause-effect relationships between these traits

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ادامه مطلب
نوشته شده توسط محمد ولی تکاسی  | لینک ثابت |

Relationships between Fertility and Other Economically Important Traits

منبع:http://www.extension.org/pages/Impact_of_Genetic_Selection_on_Female_Fertility#Relationships_between_Fertility_and_Other_Economically_Important_Traits

Milk Yield and Fertility

Milk production of dairy cows on modern commercial farms has roughly doubled over the past four decades. First parity cows on large commercial dairy farms typically peak at 40 to 45 kg/d, while second and later parity cows typically peak at 50 to 55 kg/d. Furthermore, each group typically sustains daily milk production of 40 kg/d or more during the first seven months postpartum. Therefore, one might expect differences in the reproduction of high-producing cows, as compared with low-producing cows or yearling heifers.

Lopez et al. (2005) discussed some of the differences between the reproductive biology of lactating Holstein cows and yearling Holstein heifers. In particular, Lopez et al. (2005) noted that lactating cows have shorter duration of estrus (7 to 8 hr vs. 11 to 14 hr), longer and more variable estrous cycles (20 to 29 d vs. 20 to 23 d), larger diameter of ovulatory follicles (16 to18 mm vs. 14 to 16 mm), and greater rates of anovulation (20 to 30% vs. 1 to 2%), multiple ovulation (20 to 25% vs. 1 to 3%), and pregnancy loss (20 to 30% vs. 3 to 5%).

Lopez et al. (2005) also documented differences in these characteristics between lactating cows according to levels of milk production. They (Lopez et al., 2005) used the HeatWatch system (DDx Inc., Denver, Colorado) to monitor the estrous characteristics of 146 high-producing Holstein cows (46.4 kg/d for the 10 d preceding estrus) and 177 low-producing Holstein cows (33.5 kg/d for the 10 d preceding estrus). High-producing cows had shorter duration of estrus (6.2 hr vs. 10.9 hr), fewer standing events (6.3 vs. 8.8), and shorter standing time per event (21.7 sec vs. 28.2 sec). Duration of estrus decreased linearly from 14.7 hr for cows milking 25 to 30 kg/d to 2.8 hr for cows milking 50 to 55 kg/d. In addition, the percentage of cows with multiple ovulations increased from 0.0% for cows milking between 25 and 30 kg/d to 51.6% for cows between 50 and 55 kg/d.

The rate of early embryonic loss in Holstein cows is also a major concern, as noted in several recent studies that have used ultrasound for pregnancy detection at 27 to 31 d after breeding, followed by pregnancy confirmation via rectal palpation at 39 to 48 d after breeding. Reported rates of embryonic loss during this interval ranged from 0.70 to 1.40% per day (e.g., Cartmill et al., 2001; Cerri et al., 2004; Santos et al., 2004). However, estimates of the rate of embryonic loss (particularly those from commercial farms) may be biased upward by false positive diagnoses at the early ultrasound exam, as most veterinarians tend to use caution when declaring cows as non-pregnant in herds that use hormonal resynchronization programs.

On large western dairy farms, mean veterinary-confirmed conception rates of Holstein cows at 75 d after breeding were nearly constant over the first five inseminations (0.30, 0.31, 0.31, 0.29, and 0.28, respectively), while means for Jersey cows declined linearly from the first through fifth insemination (0.42, 0.38, 0.34, 0.29, and 0.27, respectively). Mean conception rate at first service tended to decline with age in both breeds (0.35, 0.29, 0.28, 0.26, and 0.25, respectively, for first through fifth parity Holsteins and 0.44, 0.43, 0.41, 0.39, and 0.37, respectively, for first through fifth parity Jerseys), though the rate of decline was less noticeable for repeat inseminations than for first insemination (Weigel, 2006 (unpublished)). Both breeds have been selected for many generations under similar management conditions, and both have made rapid genetic progress over the past three decades (mean mature equivalent 305 d milk yield increased from 6,904 to 11,608 kg in Holsteins and from 4,461 kg to 8,273 kg in Jerseys from 1970 to 2000). Differences in mean conception rate within the Holstein breed were found among cows at different levels of daily milk yield, but such differences were smaller than one might expect (Weigel, 2005 (unpublished)). Mean conception rates at 75 d after breeding were 0.33, 0.33, and 0.32 for primiparous Holstein cows that averaged < 27 kg/d, 27 to 36 kg/d, and > 36 kg/d, respectively, during the first 3 mo of lactation; whereas corresponding means were 0.28, 0.28, and 0.27 for multiparous Holstein cows that averaged < 36 kg/d, 36 to 45 kg/d, and > 45 kg/d, respectively. In Wisconsin Holsteins, Lopez et al. (2005) found no relationship between the percentage of cows exhibiting anovulatory condition and level of daily milk yield. The percentage of anovular cows was 27.8% for cows that were milking 25 to 30 kg/d and 26.3% for cows that were milking 50 to 55 kg/d (means for 5-kg intervals in between ranged from 21.7 % to 35.1%, with no apparent trend). In California Holsteins, Santos et al. (2004) found a weak, nonsignificant relationship between milk yield and rate of embryonic loss between 31 and 45 d after breeding, with rates of 9.7% for cows that were milking 36 kg/d and 12.7% for cows that were milking 52 kg/d. Thus, it does not appear that increased milk yield is solely responsible for the decline in mean reproductive performance.

نوشته شده توسط محمد ولی تکاسی  | لینک ثابت |

اگرچه مدت زیادی از پیدایش صنعت دباغی می گذرد، اما روش های آن هنوز تغییر زیادی پیدا نکرده است. در ایران تا حدود 50 سال پیش، از روش های کاملا سنتی برای تولید چرم استفاده می شد، اما امروزه با تاسیس کارخانه های بزرگ و مدرن چرم سازی در مناطق مختلف کشور صنعت چرم ایران وارد مرحله جدیدی شده است.

این صنعت با استفاده از تجربه هزاران ساله ایرانیان در استفاده از مواد و رنگ های گیاهی و هنر خاص ایرانی در تولید محصولاتی ظریف و هنرمندانه، وجه دیگری از صنایع دستی ایران را در عرصه جهان به نمایش گذاشته است و توانسته چشم جهانیان را به خود معطوف نماید.

در صنعت چرمسازی چرم به دو نوع سبک و سنگین تقسیم می شود:
چرم سبک: چرم تولید شده از پوستهای گوسفند- بز- بزغاله و بره چرم سبک نامیده می شود و به علت ظرافت به مصرف آستری- دوخت لباس- کلاه- دستکش و کفی کش و .... می رسند و نیز از چرم بزی در دوخت کفشهای ظریف زنانه استفاده می شود.
چرم سنگین: چرم تولید شده از پوستهای گاو- گاومیش- گوساله- اسب و شتر و ... چرم سنگین نامیده می شود این نوع چرم به علت داشتن استحکام و مقاومت بیشتر به مصرف زیره و رویه کفش- پوتین و تسمه های ماشین آلات صنعتی و ... می رسند.

افزون بر دسته بندی کلی بالا انواع چرم طبیعی که مصارف گوناگون بیشتری دارند به شرح زیر می‌باشند:
چرم رویه کفشی: که از پوست گاو و گوساله و بز ساخته می شود.
چرم رویه لباسی: از پوست گوسفند ساخته می شود و بسیار نرم و لطیف است.
چرم زیره کفش: از پوست گاو و گاومیش ساخته می شود.
چرم کرومی چاپی: چرمی است رویه آن به طور مصنوعی نقش داده می شود این چرم از پوست گاو که رویه نامرغوبی دارد ساخته می شود.
چرم جیر: از پوست گوساله و بز تهیه می شود. جیر چرمی است که در اثر پرداخت کردن سطح گوشتی (سطح لش) پوست به صورت مخملی درآمده است.
چرم اشبالتی (Splitcalf): چرمی است شبیه جیر اما از ورقه ورقه کردن چرم های ضخیم گاوی بدست می آید.
چرم نو بوک (Side Nubuck): از پوست گاو تهیه می شود و چرمی است که رخ آن با ظرافت پرداخت شده است.
چرم ورنی (لاکی) (Patent Leather): این نوع چرم از پوست گاو و گوساله تهیه می شود و رویه آن را با لعاب لاکی پوشش می دهند.

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نوشته شده توسط محمد ولی تکاسی  | لینک ثابت |

Scientists have found proteins in egg whites that could be used to fight infections which cost the chicken industry billions of pounds each year.

Researchers from The Roslin Institute, at The University of Edinburgh, have discovered that these recently-identified proteins have properties that could be harnessed to combat bugs such as E-coli. The research focused on a family of proteins whose function had until now been unknown.

It was previously known that many proteins in egg whites have bacteria-fighting properties, but this group of proteins offers the potential to create anti-microbial treatments, which could be used as an alternative to traditional antibiotics.

These could be used to treat infections among poultry, and improve the sustainability of food production. It is even possible that the proteins might be used to create treatments to fight infections in humans.

The researchers have named the group of proteins ovodefensins.

Ian Dunn, an expert on avian biology at The Roslin Institute: “This family of proteins was found to be specific to birds but has not so far been discovered in other species that lay eggs, suggesting that these have either evolved in birds to fight certain infections or that other species may have lost the genes as they evolved. It is not surprising that egg white can fight bacterial infection as the egg as a whole has evolved to protect the developing embryo. The challenge now is to look at harnessing how we can use these proteins to help fight infections in poultry flocks.”

The research, funded by the EU, has been published by the journal BMC Immunology.

Source: The University of Edinburgh

نوشته شده توسط محمد ولی تکاسی  | لینک ثابت |

 
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