عوامل موثر بر توليد و تركيب شير فصل پنجم

خصوصيات يك گاو شيرده پرتوليد چيست؟ Ruann Royalty Cora day lactation Milk 57,460 lb Fat 4.0% (2,318 lb) Protein 3.5% (2,020 lb )

Beecher Arlinda Ellen 1975

Av. US cow 27 kg Cora 72 kg Holstein 45 kg Jersey 24 kg 66% 83% 75% &5% 75%

Av. US cow 27 kg Cora 72 kg Holstein 45 kg Jersey 24 kg 66% 83% 75% &5% 75%

Av. US cow 27 kg Cora 72 kg Holstein 45 kg Jersey 24 kg 66% 83% 75% 85%

عوامل موثر بر توليد و تركيب شير عوامل موثر بر توليد وتركيب شير Daily yield and composition of milk are affected by : 1-Physiological 2- Environmental

عوامل موثر بر توليد وتركيب شير Physiological factors are divided into two parts: 1- Inheritance 2- Nonhereditary factors such as age, No. of previous lactations and pregnancy

نوسان روز تا روز Both milk yield and percentage composition of milk vary considerably from day to day. Daily variation in milk yield is related to the completeness of evacuation of milk from the udder. Variation caused by disease, under- nutrition, cows being off-feed, and related factors are usually of longer duration than those caused by udder evacuation, incomplete milking, estrus, or excitement.

منحني نورمال شيردهي The relationship between milk yield to the milk fat and protein percentage is negative (Fig 1).

اوج توليد بستگي به عوامل زير دارد : Body condition Inherited potential Freedom from metabolic and infectious diseases Feeding regime

Persistency: Is the rate of decline in yield after calving

تداوم در شيردهي : نرخ يا ميزان كاهش در توليد بعد از زايمان

آغوز The first milk after parturition is colostrum, which has a marked difference from that of normal milk (Table 1).

عوامل محيطي رطوبت ودرجه حرارت Temperatures between 4-24 o C have no effect on the milk production of most dairy cows. In this range known as the comfort zone, no body processes are directly involved inn maintaining body temperature (Fig 5).

Gestation The exact reason for the decrease in milk production at the end of the pregnancy is not known. One hypothesis is an increase in the nutrient required for fetal development. A more reasonable explanation is a hormonal changes that occur at this time.

A. Pezeshki,* J. Mehrzad,† G. R. Ghorbani,‡ H. R. Rahmani,‡ R. J. Collier,§ and C. Burvenich*1 J. Dairy Sci. 90:5531–5541

Journal of Dairy Science Vol. 90 No. 12, 2007

Body Weight General relationship exist between the BW of the cows and the amount of milk produced. Larger cows have more udder secretory tissue and larger digestive systems.

Photoperiod Cows subjected to 16 h of light and 8 h of darkness produced 7-10% more milk than those exposed to 9-12 h of light per day.