The fatty acid composition of sperm affects the fertilization rate. The objective was to investigate the effects of dietary fish oil (as a source of n-3 fatty acids) on semen quality and sperm fatty acid composition in sheep. Eight Zandi fat-tailed rams were randomly allocated into two groups and fed either a control diet or a diet supplemented with fish oil. Both diets were isocaloric and isonitrogenous and were fed for 13 weeks, starting in the middle of the breeding season. Semen samples were collected weekly and their characteristics evaluated by standard methods, whereas samples collected at the start and end of the study were assessed (gas chromatography) for sperm lipid composition. Mean (6s.e.m.) sperm concentrations (4.3 3 10 9 6 1.3 3 10 8 v. 3.9 3 10 9 6 1.3 3 10 8 sperm/ml and percentages of motile (77.25 6 3.34 v. 60.8 6 3.34) and progressively motile sperm (74.13 6 1.69 v. 62.69 6 1.69) were significantly higher in the fish oil group than control. Dietary fish oil increased the proportion of docosahexaenoic acid (DHA, C22:6 n-3) in sperm fatty acid composition. We concluded that feeding fish oil as a source of n-3 fatty acids attenuated seasonal declines in semen quality in rams, perhaps through increased DHA in sperm.

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The objective of this study was to investigate the effect of feeding different levels of ruminally protected methionine and choline on the incidence of physiological and metabolic disorders, production, and some of the reproductive indices of Holstein dairy cows. Forty Holstein dairy cows in their first and second lactation were used from 4-week pre-partum through 20-week post-partum and randomly assigned to receive one of the following treatments: 18 g/day of rumen-protected methionine (RPM), 60 g/day of rumen-protected choline (RPC), 18 g/day of RPM + 60 g/day of RPC, and neither supplement (control). The treatments significantly affected services per conception and open days of lactating dairy cows (p < 0.05), but did not affect significantly on days to first oestrus and number of pregnant cows. RPM + RPC-fed cows had the lowest open days, days to first oestrus and services per conception compared with other groups. The effect of treatments was significant on the incidence of metabolic and physiological problems except for foot/leg problems. Cows fed RPM+RPC had the lowest health problems compared with other groups (p < 0.05). Results indicate that the supplementation of RPM and RPC can improve reproductive performance and health status of dairy cows.

An experiment was conducted to determine the effects of different milking frequencies on entire lactation production performance in Holstein cows. One hundred twenty Holstein cows were assigned to 3 milking treatments (35 multiparous and 5 primiparous cows in each): 1) milking 6 times daily for the entire lactation (6x); 2) milking 6 times daily for the first 90 d in milk (DIM) and switching to 3 times daily milking afterward (6x-3x); and 3) milking 3 times daily for the entire lactation (3x). Milk yield was recorded every other day during the first 60 DIM and on 2 consecutive days per week subsequently. Cows were weighed and scored for their body condition immediately after parturition and monthly afterward. Blood and milk samples were taken from each cow on 30, 60, 90, 120, 150, 210, and 270 DIM, with an additional blood sampling on 15 DIM. Milk and fat corrected milk yield was greater for 6x and 6x-3x cows than for 3x cows (36.82, 37.32, and 36.1, 36.75 versus 34.56, 35.33 kg/d, respectively) during the experimental period. Milk fat and lactose percentage were not different among treatments, but milk protein was lower in 6x cows than in 6x-3x and 3x cows. Blood glucose concentration was higher and blood nonesterified fatty acids and beta-hydroxybutyrate concentration were lower in 3x cows than in 6x and 6x-3x cows during early lactation. Dry matter intake was greater in 6x cows than in 6x-3x and 3x cows (23.05, 22.58, and 22.45 kg/d, respectively). The 3x cows began to gain weight earlier than the 6x and 6x-3x cows, but there was no difference among groups for BW change regarding the entire experimental period. These results indicate that increasing milking frequency to 6 times daily increases milk yield only during early lactation and that there are no advantages of milking 6 times daily compared with 3 times daily during the mid and late lactation periods. Given the results of this study and the economical aspects of production, milking 6 times daily until 90 DIM and subsequently switching to milking 3 times daily is preferred.