مجله علوم دامی ایران
سال پنجاه و یکم شماره 3 (پاییز 1399)

The objective of this study was to determine the effects of the replacement of corn silage with barley silage on high producing dairy cow performance. Thirty six high-producing (57.3±3.9kg/d) dairy cow in mid-lactation (93±7 DIM) were assigned to one of three experimental treatments including (1) no barley silage (BS) and 30% corn silage (CS), (2) 10% BS and 20% CS, and (3) 20% BS and 10 % CS in the TMR over two 24-day periods. The results showed that replacement of corn silage with barley silage linearly increased fat corrected milk (FCM; P=0.04), fat yield (P=0.04) and fat corrected milk production efficiency (P=0.01). There was also a tendency for linear increase in milk fat percentage (P=0.08), and linear decrease in milk lactose percentage (P=0.05). Ruminal acetate proportion and pH increased with increasing barley silage and propionate proportion decreased. Increasing barley silage resulted in linear increase in dry matter, organic matter and neutral detergent fiber digestibility (NDF; P<0.05). This study showed that replacing corn silage with barley silage could be considered as a successful strategy to improve performance and forage provisions of high-producing dairy cows.

The aim of this study was to investigate the effects of feeding different trace minerals (Zn, Cu, Mn, Se and Co) sources from 4 weeks pre- lambing until 5 week post-lambing on performance and health of Afshari ewes and lambs. Thirty six pregnant Afshari ewes were randomly assigned to 1 of 3 treatments at 32.5±5 d before expected lambing date. Experimental treatments were basal diet without supplemental trace minerals (Control, n=12), basal diet plus sulfate sources of trace minerals (Sulfate, n=12) and basal diet plus organic sources of trace minerals chelating to Glycine (Glycinate, n=12). In each treatment, ewes were balanced for fetal number, body weight (BW), Body condition score (BCS) and expected lambing date. Dry matter intake, BW, BCS and their changes, colostrum and milk yield and milk composition were not affected by treatments (P>0.05). There was no effect of treatments on serum metabolites concentrations, except a tendency (P=0.07) to increase in serum glucose concentrations pre-lambing for ewes receiving sulfate sources of trace minerals compared to those in Glycinate group. Birth weight of lambs was similar among treatments, but lambs BW from ewes fed glycinate source of trace minerals at 35 d was greatest among treatments (P= 0.05). Likewise, average daily gain (ADG) of lambs from Glycinate ewes tended to be greater at 35 and 70 d compared to control and sulfate groups (P=0.07). Overall, feeding chelated trace minerals per- and post-lambing Ashari ewes improved growth performance of lambs until 70d.

The present study was designed to investigate the effect of inactivated Tsukamurella inchonensis (T. inchonensis) on the immune response against infectious bursal disease (IBD) vaccination in broiler chicks. Ross broiler chicks in the cage (n= 180; one day old) were randomly assigned to five groups (36 birds in each group). Experimental diets were prepared by adding 106 cells per bird of inactivated T .inchonensis into the commercial basal diet. For group the treatment was continuously dosed during 24 h from day 1 to day 13; and for group 2 during 24 h on days 1 to 5; 8; 9, 12 and 13. Group 3 was received 106 bacteria as subcutaneous injection on days 1, 6, and 12. Groups 4 and 5 weren't received T. inchonensis during the experiment period. Blood was collected on days 1, 14, 28, and 42 from the wing vein of 12 birds, randomly per treatment. Serum IBD antibody titer were studied by ELISA, which measured by double-antibody sandwich ELISA using commercial kits. T. inchonensis treatments, irrespective of the routes of delivery, increased the antibody titers to IBD vaccines, especially when broiler chickens treated with pulse dosed in the feed (p < 0.05). T. inchonensis augmented the effects of IBD vaccination in strengthening subsequent anti-viral responses.

This study aimed to investigate the effects of partial replacement of wheat straw for corn silage and alfalfa hay at 7% diet dry matter (DM) on feed intake, nutrient digestibility, and milk production of late-lactation Holstein cows. Eight multiparous Holstein cows (averaging 2.9±0.35 parity; 43.6±2.6 kg/d milk yield; 214±18 d in milk) were used in a replicated 4×4 Latin Square design. During each of four 21-d periods, cows were fed  total mixed rations varying in forage source: 1) control (13.5% alfalfa hay, 20% corn silage and 66.5% concentrate), 2) wheat straw replaced for corn silage, 3) wheat straw replaced for alfalfa hay 4) wheat straw equally replaced for corn silage and alfalfa hay. Diets were formulated to contain similar values of NDF, forage NDF and physically effective NDF. The DM intake, milk production and compositions as well as total tract digestibility of DM, organic matter, NDF, and crude protein were unaffected by treatments. Likewise, ruminal and blood parameters were not affected by experimental treatments. Body weight gain tended to be lower (P=0.06) for cows fed the wheat straw-included diets. These results indicated that, at 7% of diet DM, chopped wheat straw could be used as an alternative for major forage sources high concentrate diets for lactation cows yielding over 40 kg/d milk.

The study was conducted to evaluate the effects of fiber source and particle size on growth performance and gastrointestinal tract characteristics in broiler chickens from d 1 to 21. A total of 420 male broiler chickens were randomly distributed in 7 treatments and 6 replicates per treatment, which were arranged factorially. Experimental treatments including three insoluble fiber sources, 3% (sunflower hulls, SFH; rice hulls, RH; and camelina hulls, CH), and two sizes of fiber particles (fine (1 mm) and coarse (3 mm)), and a control group (without fiber addition). Main effects of fiber sources and particle size on feed intake, body weight gain and feed conversion ratio were not significant (P˃0.05), whereas, the inclusion of fine SFH improved body weight gain compared to the control group (P<0.05). The main effects of source and size of fibers did not affect gizzard weight, although the inclusion of coarse SFH tended to increase gizzard weight compared to control (P=0.08). The SFH and RH-containing diets improved the relative jejunum weight than the CH-containing diet (P<0.05). Experimental treatments did not influence the pH of proventriculus and gizzard, as well as the relative weights of duodenum and ileum. The main effect of fiber particle size was significant in term of cecum weight, so that coarse grinding increased cecum weight compared to fine grinding (P<0.05). Based on the results of this research, dietary inclusion 3% of sunflower hulls, rice hulls, and camelina hulls in the diet of broilers had no negative impacts on the growth performance of broiler chickens, while diluting the diet with sunflower hulls could improve body weight and gizzard weight.

The main objective of dairy farmers is to maximize their profit. Increased incidence of mastitis in farms is one of the health problems, causing in serious economic losses as a consequence of treatment costs and reduction of production and longevity. The objective of this study was to evaluate the genetic architecture and associated genomic regions with milk production and somatic cell score (SCS) as an indirect measure of mastitis and the quality of raw milk. Thus, an SNP data set from 1938 Holstein bulls were used in a single-step genome-wide association study. The proportion of additive genetic variance (agv) for each of 1.5-Mb genomic window (adjacent SNPs) was used to identify informative genomic regions, accounting for more than 1% of the agv. A total of 11 significant windows over 9 bovine autosomes were found for the SCS. A peak on BTA14 explained the largest proportion of variance (3.85%). These regions together, explained 20% of agv and harbored 94 candidate genes. For milk yield, we identified 6 informative windows across 6 chromosomes, and a peak on BTA10 explained 2.08% of agv. These regions, explained 8.8% of the agv and sheltered 89 candidate genes. For the fat yield, 9 significant windows were identified on 7 chromosomes and explained 15.6% of agv, and 9 windows contained 87 candidate genes on 8 bovine autosomes were associated with milk protein yield (10.6% of agv). Four genomic regions had a pleiotropic effect. These findings can be an important source of information in genomic evaluation of dairy cattle.