Effects of Environmental Factors on Milk Yield, Lactation Length and Dry Period in Tunisian Holstein Cows

Abstract

duration, dry period and service period between optimal limits [6,7]. The yields of farm animals are the result of the combined effects of genotype and environmental conditions. I n o r d e r t o i n c r e a s e t h e y i e l d l e v e l , i t i s n e c e s s a r y t o o p t i m i z e t h e e n v i r o n m e n t a l conditions and to improve the genetic structure of the animals. In order to enhance productivity of a dairy animal, it is necessary to develop an understanding of the factors affecting its milk production. Environmental factors can be classified as factors with measurable effects (age, year, season, milking frequency, etc.) and factors with immeasurable effects (infectious diseases, parasitic infestations, etc.). The measurable effects can be determined and used in the management of the farm [8]. Environmental factors affecting variability in daily milk yield are widely documented in dairy cattle [9][10][11]. The 305 days milk yield of Holstein cows was 5905 kg in Tunisia [12], 5353 kg in Morocco [13], and between 4597 and 6464 kg in Turkey [14][15][16]. Environmental factors such as year of calving, season of calving and age at calving affect productivity [17]. Many researchers [6,14] reported that the effect of calving season on 305 days milk yield was as significant and indicated that milk yield was higher in autumn and winter. Unlike, Bilgiç and Aliç [16] and Pelister et al. [18] reported that effect of calving season on 305 days milk yield was non-significant. Although, effect of lactation number on 305

Effects of Parity on Postpartum Fertility Parameters in Holstein Dairy Cows

“…Hamdi et al, 2012 (6) reported that the least squares analysis revealed that 305 days milk yield was significantly (P<0.001) affected by calving season. As well, the shorter lactation duration investigated by Hamdi et al, 2012 (6) is 127.56 days and this may be due to incomplete lactations when data were collected.…”

“…It is well known that the birth season have an effect on ovarian resumption (2,3,4), days open (5), milk yield (6) as well as number of services per conception (6). The onset of normal ovarian cyclic activity is one of the most important events for dairy cow to regain her maximum breeding potential following parturition.…”

Role of Probiotics in Animal Productivity and Health: A Review

“…cattle of tropical countries it ranges from 6.5 to 9.8Litter/day [17]. Contributing factors for variation in lactation performances from season to season/year to year is due to herd size, good management and age of the animal [18].…”

“…Moreover, a good housing is necessary to ensures better environmental situation. Space for waste disposal as well as lack of sufficient land for proper housing, milking and farm expansion has been considered as constraint to produce good quality milk [18].…”

Effect of Cow Parity and Calf Characteristics on Milk Production and Reproduction of Friesian Dairy Cows

“…The interval in several herds could be reduced by breeding cows on first heat after 45 days postpartum and/or next to first examining the cows for normal reproductive tracts. Hamdi et al, (2012) reported many factors that caused prolonged days open in dairy cows (i.e. feeding season and milk production, silent estrus, frequency and timing of estrus detection, missed estrus due to weak symptoms).…”