The current study examined the effects of live yeast (LY) supplementation to dairy cows during the summer season on milk production, feed efficiency and ration digestibility. Forty-two dairy cows (14 primiparous and 28 multiparous) were fed either a control lactating diet or supplemented with 1 g of LY (Saccharomyces cerevisiae, Biosaf, Lesaffre) per 4 kg of dry matter consumed. The LY amounts were adjusted twice a week. Four rumen samples were taken from 30 cows in 2-h periods and ammonia concentrations were determined. Fecal grab samples from 30 cows were collected during 3 consecutive days, to determine the apparent digestibility of diets. The daily dry matter intake in the LY group was 2.5% greater compared with the control group (24.7 and 24.1 kg, respectively). The daily average milk yield of the LY group was greater by 1.5 kg (4.1%) compared with the control group (37.8 vs. 36.3 kg, respectively). There were no significant differences in the milk fat and protein percentages, but fat yield was greater in the LY group than in the control. The fat-corrected milk 4% was 2.0 kg (6.1%) greater in the LY group than in the control group (34.8 vs. 32.8 kg, respectively). The efficiency of using dry matter to produce 4% fat-corrected milk was 3.7% greater in the LY group compared with the control group. The ruminal ammonia concentrations after feeding were greater in the control group than in the LY group (151.9 vs. 126.1 mg/l, respectively). No differences were observed among groups in the total tract apparent digestibility of dry matter and other diet components. The pH values in the rumen that were determined in a companion trial using 4 fistulated cows tended to be higher in cows that were supplemented with LY than in the control (6.67 vs. 6.54, respectively). It may be concluded that LY supplementation to dairy cows during the hot season improved the rumen environment in a way that increased the dry matter intake and in consequence enhanced the productivity and efficiency.

The periparturient period in dairy cows is associated with alterations in insulin action in peripheral tissues; however, the molecular mechanism underlying this process is not completely understood. The objective was to examine the response to a glucose tolerance test (GTT) and to analyze insulin signaling in liver and adipose tissues in pre- and postpartum dairy cows. Liver and adipose tissue biopsies were taken before and after GTT, at 17d prepartum and again at 3 to 5d postpartum from 8 high-yielding Israeli Holstein dairy cows. Glucose clearance rate after GTT was similar pre- and postpartum. Basal insulin concentrations and the insulin response to GTT were approximately 4-fold higher prepartum than postpartum. In accordance, phosphorylation of the hepatic insulin receptor after GTT was higher prepartum than postpartum. Across periods, a positive correlation was observed between the basal and peak plasma insulin and phosphorylated insulin receptor after GTT in the liver. Hepatic phosphorylation of protein kinase B after GTT was elevated pre- and postpartum. Conversely, in adipose tissue, phosphorylation of protein kinase B after GTT pre- and postpartum was increased only in 4 out of 8 cows that lost less body weight postpartum. Our results demonstrate that hepatic insulin signaling is regulated by plasma insulin concentrations as part of the homeorhetic adjustments toward calving, and do not support a model of hepatic insulin resistance in periparturient cows. Nevertheless, we suggest that specific insulin resistance in adipose tissue occurs pre- and postpartum only in cows prone to high weight loss. The different responses among these cows imply that genetic background may affect insulin responsiveness in adipose tissue pre- and postpartum.

Our objectives were to determine the effects of rapid growth rate during the preweaning period and prepubertal protein supplementation on long-term growth pattern and milk production during the first lactation. Forty-six Israeli Holstein heifer calves were fed either milk replacer (MR) or whole milk (WM) from 4 to 60 d age. Calves had free access to WM or MR for 30 min twice daily and free-choice water and starter mix for the entire day. From weaning until 150 d of age, all heifers were fed the same ration. At 150 d of age the heifers were divided into 2 subgroups, with one subgroup supplemented with an additional 2% protein until 320 d of age. Thereafter, all heifers were housed and fed together until calving. Another cluster of 20 heifers was raised on MR and WM treatments and 3 animals from each nursery treatment were slaughtered at 60 d and 10 mo age to determine effects of nursery treatment on organ and adipose tissue mass. Prior to weaning, the MR heifers consumed 0.12 kg/d more DM than the WM heifers, but metabolizable energy intake was not different. Body weight at weaning and average daily gain during the preweaning period were 3.1 kg and 0.074 kg/d higher, respectively, in the WM treatment than in the MR treatment, with no differences in other measurements. Nursery feeding treatment and added protein had no effect on growth rate in the prepubertal period, but the postweaning difference in BW between the WM and MR heifers remained throughout the entire rearing period. The age at first insemination was 23 d earlier and age at pregnancy and first calving was numerically lower for the WM heifers than for the MR heifers. Adipose tissue weights at weaning were doubled in the WM calves. First-lactation milk production and 4% fat-corrected milk were 10.3 and 7.1% higher, respectively, for WM heifers than for MR heifers, whereas prepubertal added protein tended to increase milk yield. In conclusion, preweaning WM at high feeding rates appears to have long-term effects that are beneficial to future milk production. The positive long-term effects of feeding WM on first-lactation milk production were independent of their effects on skeletal growth. Enhanced milk production observed with WM treatment may be related to the milk supply, paracrine or endocrine effects of fat tissues on mammary parenchyma, or a combination of both factors.

The objectives were to determine the incorporation of dietary encapsulated fats differing in n-6:n-3 ratio into milk fat, plasma, and various ovarian compartments and to examine the effects on ovarian follicular status, preovulatory follicle characteristics, and oocyte quality. Twenty-four multiparous Israeli Holstein cows, averaging 114 d in milk, were assigned to 1 of 3 treatment groups: 1) control (n=7), in which cows were fed a lactating cow diet; 2) E-FLAX (n=8), in which cows were fed a lactating cow diet that consisted of 1kg/d of encapsulated fat (3.8% of dry matter) containing 40.8% flaxseed oil, providing 242.2g of C18:3n-3 (low n-6:n-3 ratio); or 3) E-SUN (n=9), in which cows were fed a lactating cow diet that consisted of 1kg/d of encapsulated fat (3.8% of dry matter) containing 40.8% sunflower oil, providing 260.0g of C18:2n-6 (high n-6:n-3 ratio). Ovaries were monitored by ultrasonography for follicular status, and after synchronization, follicles >7mm were aspirated and evaluated. Ovum pickup was performed (19 sessions for the control and E-FLAX groups and 11 for the E-SUN group), and in vitro maturation and oocyte fertilization were conducted. The E-FLAX treatment increased the proportions of C18:3n-3 (5.8 fold), C20:5n-3, and C22:5n-3 (approximately 4-fold) in milk fat as compared with the other 2 treatments. The proportion of C18:3n-3 fatty acid in plasma increased dramatically with the E-FLAX treatment, from 1.43 and 1.49% in the control and E-SUN groups, respectively, to 7.98% in the E-FLAX group. Consequently, the n-6:n-3 ratio in plasma was reduced from approximately 42 in the control and E-SUN groups to 6.74 in the E-FLAX group. Proportions of C18:3n-3 in follicular fluid and granulosa cells were approximately 5-fold higher in the E-FLAX group than in the other 2 groups. The percentage of C18:2n-6 in cumulus-oocyte complexes of cows in the E-SUN group was 54% higher than that in the E-FLAX group and was 2.4-fold higher than that in the control group; the proportion of C18:3n-3 in the E-FLAX group was 4.73% and was not detected in the other groups. The average numbers of 2- to 5-mm follicles on d 5 and 9 of the cycle were higher in the E-FLAX group than in the E-SUN group, whereas the average numbers of follicles > or =10mm on d 5, 9, and 13 were higher in the E-SUN group than in the other 2 groups. The estrous cycles of the cows were synchronized and PGF(2alpha) was injected on d 16 to 17 of the cycle. The interval from PGF(2alpha) injection to behavioral estrus was longer in the E-FLAX group than in the E-SUN group, and the beginning of the luteal phase of the subsequent cycle was delayed. Concentrations of estradiol in follicular fluid of the preovulatory follicles were higher in the E-SUN group than in the E-FLAX group. The number of follicles aspirated by ovum pickup was higher in the E-FLAX group than in the control group, and the cleavage rate in the E-FLAX group was higher than in the control group, but not the E-SUN group. In conclusion, dietary n-3 fatty acids influenced the follic...

The objective of this study was to determine the effects of feeding an increased amount of extruded flaxseed with high proportions of n-3 fatty acids (FA) to transition dairy cows on performance, energy balance, and FA composition in plasma, adipose tissue, and milk fat. Multiparous Israeli-Holstein dry cows (n = 44) at 256 d of pregnancy were assigned to 2 treatments: (1) control cows were fed prepartum a dry-cow diet and postpartum a lactating-cow diet that consisted of 5.8% ether extracts; and (2) extruded flaxseed (EF) cows were supplemented prepartum with 1 kg of extruded flaxseed (7.9% dry matter)/cow per d, and postpartum were fed a diet containing 9.2% of the same supplement. The EF supplement was fed until 100 d in milk. On average, each pre- and postpartum EF cow consumed 160.9 and 376.2g of C18:3n-3/d, respectively. Postpartum dry matter intake was 3.8% higher in the EF cows. Milk production was 6.4% higher and fat content was 0.4% U lower in the EF group than in the controls, with no differences in fat and protein yields. Energy balance in the EF cows was more positive than in the controls; however, no differences were observed in concentrations of nonesterified fatty acids and glucose in plasma. Compared with controls, EF cows had greater proportions of C18:3n-3 in plasma and adipose tissue. The proportion of n-3 FA in milk fat was 3.7-fold higher in the EF cows, and the n-6:n-3 ratio was decreased from 8.3 in controls to 2.3 in the EF cows. Within-group tests revealed that the C18:3n-3 content in milk fat in the EF cows was negatively correlated with milk fat percentage (r = -0.91) and yield (r = -0.89). However, no decrease in de novo synthesis of less than 16-carbon FA was found in the EF group, whereas C16:0 yields were markedly decreased. It appears that the enrichment of C18:3n-3 in milk fat was limited to approximately 2%, and the potential for increasing this n-3 FA in milk is higher for cows with lower milk fat contents. In conclusion, feeding increased amounts of C18:3n-3 during the transition period enhanced dry matter intake postpartum, increased milk production, decreased milk fat content, and improved energy balance. Increased amounts of EF considerably influenced the FA profile of plasma, adipose tissue, and milk fat. However, the extent of C18:3n-3 enrichment in milk fat was limited and was negatively correlated with milk fat content and yield.

The objectives of this study were to determine the differential incorporation of various omega-3 (n-3) fatty acids (FAs) supplemented to dairy cows into ovarian compartments and assess the effects on IVF. Forty-two 256-day pregnant cows were supplemented with encapsulated fats, in treatments designated as i) SFA -saturated fat at 240 and 560 g/day per cow, prepartum and post partum (PP) respectively; ii) FLX -flaxseed oil at 300 and 700 g/day per cow prepartum and PP respectively; and iii) FO -fish oil at 300 and 700 g/day per cow prepartum and PP respectively. Commencing at 60 days in lactation, ovum pickup (OPU) was performed twice weekly (20 sessions; five cows per group) and in vitro maturation and IVF were conducted. The proportion of a-linolenic acid (ALA) was greater in follicular fluid (FF), granulosa cells, and cumulus-oocyte complexes (COCs) of FLX cows than in other groups (P!0.001). The proportion of docosahexaenoic acid (DHA) was 6.7 times as great in FF of FO as in other groups (P!0.001); docosapentaenoic acid n-3 and DHA were detected in COCs of FO but not in others. The follicle number during OPU was higher in FLX and FO than in SFA (P!0.05), and the oocyte cleavage rate was higher in FLX and FO than in SFA (P!0.01). Also, the percentage of oocytes that developed to blastocysts tended to be higher in both n-3 groups than in SFA (P!0.1). In conclusion, both dietary n-3 FAs similarly improved folliculogenesis and IVF performance; therefore, ALA-rich botanical n-3 seems to be a satisfactory approach to improve oocyte quality.

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The objectives were to determine the effects of cooling of high-yielding dairy cows under a hot and humid climate on intake, milk yield, rumination time, and welfare parameters. Forty-two multiparous Israeli Holstein dairy cows were divided into 2 treatment groups and were housed in an open barn divided into 2 pens. The groups were subjected to different cooling schedules, in a crossover design as follows: cows were exposed to 5 or 8 cooling sessions per day (designated 5CS and 8CS, respectively) in the holding area of the milking parlor. Each period lasted 4 wk, and then treatments were switched for another 4-wk period. Each cooling session lasted 45 min, comprising cycles of 30s of showering and 4.5 min of ventilation without showering. Respiration rate and rectal temperature were recorded twice per week (Monday and Thursday) at 0630 and 1600 h. Rumination and lying times were recorded automatically. Rectal temperatures were 0.16 and 1.08°C lower in 8CS than in 5CS cows in the morning and afternoon, respectively. Respiration rate was lower in 8CS than in 5CS cows in the morning (49.1 and 54.6 breaths/min, respectively), and more so in the afternoon (50.0 and 83.0 breaths/min, respectively). Dry matter intake and milk yields were 9.3 and 9.6% higher in the 8CS than in the 5CS cows (27.0 vs. 24.7 and 40.1 vs. 36.6 kg/d, respectively), with no differences in milk fat and protein contents. Daily rumination time was 7.4% longer in the 8CS than in the 5CS (440.1 and 409.6 min/d, respectively); however, rumination time per unit of dry matter or neutral detergent fiber consumed was higher in the 5CS than in the 8CS cows. Although the 8CS cows moved 3 times more to the milking area for extra cooling sessions than the 5CS ones, they spent 9.9 min/d more than the 5CS ones in lying down (484.4 and 474.5 min/d, respectively), and used more of their free time (excluding milking and feeding time) in resting than the 5CS cows: 52.0 and 43.9%, respectively. It appears that increasing the cooling frequency from 5 to 8 times per day improved their feeling of welfare, so they could spend more time lying and ruminating. In conclusion, increasing the cooling frequency of high-yielding dairy cows under hot and humid conditions from 5 to 8 times a day increased their intake and milk yield, and lowered their respiration rate and rectal temperature. Moreover, the 8CS cows spent more time resting than 5CS cows, an indication that increasing cooling frequency improved animal welfare.