تاثیر عوامل غیر ژنتیکی بر تولید و ترکیب شیر بزهای مودار بومی شهرکرد

Extended Abstract:
Background and purpose: Goat milk plays an important role in human nutrition in developing countries, especially in rural areas where goats are commonly raised. It is possible to use goat as a potential source of protein (milk and meat) and income (skin and leather) to improve the livelihood of rural people. Compared to sheep and cattle, raising goats could help reducing poverty and improving human nutrition in harsh and unfavorable environmental conditions with no or little concentrated feed. In situations where access to cow's milk is limited, goats have the potential to produce milk for rural households. The native goat of Chahar Mahal and Bakhtiari province, with a population exceeding one million heads, which are mainly raised in nomadic and rural conditions plays an important role in creating employment and income for breeders. The purpose of this study was to investigate the effect of non-genetic factors on milk production, percentage of fat, protein, lactose and solids not-fat of native goat milk of Chahar Mahal and Bakhtiari province in the climatic conditions of Shahrekord.
Materials and methods: In this research, data (n=2812) on test days of milk production and its components were collected during 2006 to 2009 from the livestock research and breeding station of Shahrekord University. The management of the herd was semi-extensive, so that the goats were reared from the beginning of December to the beginning of May at the station by hand feeding and the rest of the year on pastures. In hand feeding, the ration of goats was adjusted according to age, sex, stage of pregnancy and lactation. The composition of goats' diet was 40% concentrate (including barley, wheat bran, sugar beet pomace and cottonseed meal) and 60% alfalfa hay. On the day of recording, after weighing the milk of each goat, 40 ml of milk samples were sampled to measure the composition of milk, the percentage of fat, protein, lactose and milk solids. The milk samples were analyzed using the Lactostar device made by Funk Gerber, Germany and the specialized program related to goat milk. The average results of morning and evening milk samples were calculated and weekly values of milk composition were obtained. The Fleischman method was used to calculate the total milk production in one lactation period (Ruiz, 2007).
Data analysis of variance was performed using SAS software (version 9.4). The data were analyzed using a mixed statistical model with repeated measures for the fixed factors year of kidding, month of
kidding, number of kids born, age of goat in kidding, week of lactation, length of lactation period (covariable only on total milk production) and random effect of goat and the means were compared using the Tukey test.
Results: All fixed factors had a significant effect (P<0.001) on milk production traits and its components. However, the number of kids born had no significant effect on the total milk production (P<0.05). The highest amount of daily milk production related to goats born in the year of production 2009 (1.024±0.04 kg), May (0.945±0.04 kg), 5-year-old goats (0.857±0.06 kg)) and the type of birth was triplets (0.872±0.05 kg). The percentage of fat, lactose and milk solids-not-fat increased from the beginning to the end of the lactation period. The percentage of protein did not change much until the middle of the lactation period, and then it increased.
Conclusion: These results provide important data that can be used as a basis in the design of a genetic progress program to improve the productive traits of native goats.
Key words: milk production, milk quality, native goat of Shahrekord.