Relationship between the activity of mitochondrial respiratory chain complexes and feed efficiency in fat-tailed Ghezel lambs.

This study was conducted to investigate relationships between mitochondrial respiratory chain complex activities, feed efficiency, and carcass traits in sheep. A group of Ghezel male lambs sired by a single ram were randomly allotted to individual pens. The lambs were fed ad libitum with a fattening diet containing 30% roughage (corn silage and alfalfa hay) and 70% concentrate for 70 d to individually phenotype each lamb for feed conversion ratio (FCR), adjusted FCR (aFCR), and residual feed intake (RFI). The lambs were then humanely killed and the liver, abdominal fat, pelvic fat, cardiac fat, warm carcass weight, and cold carcass weight, as well as the cross-sectional area of the LM and the fat depth over the 12th rib, were determined. A portion of LM was obtained to determine mitochondrial protein and respiratory chain complex activities (complexes I to V). Statistical analysis was carried out based on lambs exhibiting high and low RFI (n = 8), FCR (n = 8), or aFCR (n = 8) phenotypes. The lambs exhibiting the high-RFI phenotype consumed 110 g more feed daily (P < 0.05) than did the phenotype exhibiting low RFI, with no difference in ADG. Conversely, there was no difference in feed intake between the low- or high-FCR groups, but sheep exhibiting the low-FCR phenotype gained 70 g more (P < 0.05) per day compared with those exhibiting the high-FCR phenotype. It was determined that all 5 respiratory chain complex activities were greater (P < 0.05) in sheep exhibiting the low-RFI phenotype compared with those exhibiting the high-RFI phenotype, with significant (P < 0.001) negative correlation coefficients between RFI and respiratory chain complex activity. When efficiency was assessed using FCR, only activities of respiratory chain complexes III, IV, and V were less (P < 0.05) in the low-FCR phenotype compared with the high-FCR phenotype, and there were no differences (P > 0.1) in respiratory chain complex activities between groups when FCR was adjusted for metabolic BW (aFCR). There were no differences (P > 0.1) in carcass traits among any of the feed efficiency phenotypes. The results suggest that the inclusion of respiratory chain complex activities in breeding programs may be helpful in selecting for sheep exhibiting the low-RFI phenotype.

Effect of a calcium soap of fatty acids on reproductive characteristics and lactation performance of fat-tailed sheep.

Experiments were carried out to study the effect of feeding Megalac, calcium soaps of fatty acids (protected fat), on reproduction and lactation of sheep. In the first experiment, 20 Ghezel and 20 Mehraban cyclic fertile ewes (4-5 years old) were randomly allotted to 4 groups. The control group was fed with a balanced ration and the other groups received the same diet as well as a daily allowance of 40 g non-protected fat (NP), 40 g protected fat (LP), or 80 g (HP) protected fat. The ewes were fed with their respective rations for one cycle length. Blood samples were collected and analyzed for progesterone (P4), cholesterol (CHOL), High Density Lipoproteins (HDL), Low Density Lipoproteins (LDL) and triacylglycerols (TG). The ewes were slaughtered on their next estrous period and the size and number of follicles in ovaries were recorded. There were no significant effects of feeding fat on ovarian weights, cycle length and follicular numbers in each class, or on the size of the largest follicle. Serum concentrations of P4, CHOL, TG and HDL were greater for HP ewes as compared with the control ewes (p<0.05). In the second experiment, effects on lactation and lamb performance of feeding protected fat during mating, late gestation and early lactation were studied in Mehraban ewes. Milk and fat yields on day 25 of lactation were significantly increased by feeding protected fat. Protected fat resulted in lower weight loss in ewes and a higher lamb birth weight. Average daily weight gain of lambs from birth to day 60 and the weaning weight of lambs were increased by feeding protected fat (p<0.05). In conclusion, calcium soaps of fatty acids increased serum P4 between days 10 to 14 of the cycle which may be beneficial to early pregnancy maintenance. Protected fat seemed to have a beneficial effect on milk yield, fat yield, lamb daily gain, lamb birth weight and ewe weight loss.

Effect of energy and protein levels on feedlot performance and carcass characteristics of Mehraban ram lambs.

Fifty four Mehraban ram lambs (6-to 8-month old, initial live weight 35.4 +/- 4.2 kg) were assigned to a completely randomized design consisting of 9 groups and were fed for 70 days with diets containing three levels of energy (2.3, 2.5 and 2.7 Mcal metabolizable energy per kg dry matter) and three levels of protein (10.5, 12.5 and 14.5 percentage in dry matter). Either energy or protein levels alone significantly affected most of the parameters of lamb performance, but their interaction effect was significant only for feed conversion ratio, cold carcass weight, tail weight, flap weight and back fat (subcutaneous fat) depth. The lowest level of energy (2.3 Mcal ME per kg DM) resulted in a significant decrease in lamb performance as compared with other energy levels. Increasing energy concentration of the diet resulted in significant increases in fat percentage, but significantly decreased the moisture and protein content of the Longissimus dorsi muscle. Increased dietary protein level increased the daily DMI and ADG and at the same time improved the FCR. Hot and cold carcass weights increased significantly with increasing dietary CP levels, but dressing percentage was similar amongst the dietary protein densities. Dietary CP levels had no significant effect on the chemical composition of the Longissimus dorsi muscle. At the lowest energy level (2.3 Mcal ME per kg DM), dietary protein level had a significant effect on FCR (Table 4); with the diet containing 10.5% protein having the highest FCR. At the medium and low energy levels the lowest level of dietary protein concentration resulted in smaller carcasses. The highest level of protein along with the medium energy concentration resulted in smaller tail weights. Flap weight was significantly smaller at low energy concentration along with medium and low protein level. The lowest back fat depth was found in lambs fed on the low energy diet containing medium to high levels of protein.

Effect of dietary fish meal on production performance and cholesterol content of laying hens.

The effect of dietary fish meal (FM) on production and egg yolk cholesterol of commercial Hyline White Leghorn hens (24-week old) was studied for four weeks. Eighty birds were given a corn-wheat-soyabean meal diet that contained either 0% (control diet, C) or 3% fish meal (DM basis). Hens were randomly divided into two experimental treatments with four replicates (10 hens per replicate). Egg weight, daily egg production (g/hen/day), daily feed consumption and feed conversion ratio were recorded. At the end of each week, 12 eggs from each group were randomly collected and egg yolk cholesterol, egg volume, shell thickness and Haugh unit (HU) were measured. There was no significant (p > 0.05) effect of feeding 3% FM on egg yolk cholesterol concentration (mg/100 g yolk or mg/yolk) compared with the control diet, but 3% FM, tended to decrease egg yolk cholesterol concentration (1930.93 vs 2021.48 mg/100 g yolk). Hens fed on 3% FM had higher (p < 0.05) egg production, egg weight, egg volume, shell thickness, HU and better feed conversion ratio. It was concluded that under the condition of the study, feeding 3% fish meal improved egg production traits but was not able to reduce cholesterol concentration of the egg yolk although tended to reduce cholesterol concentration.