208 SUPEROVULATORY RESPONSE AND EMBRYO PRODUCTION IN HOLSTEIN COWS FED DIETS ENRICHED IN OLEIC, LINOLEIC, OR α-LINOLENIC ACID

Early embryonic development is enhanced in Holstein cows fed diets enriched in linoleic and α-linolenic acids compared to those fed a diet enriched in stearic fatty acid (Thangavelu et al. 2007; Theriogenology 68, 949–957). A positive effect of oleic acid on oocyte competence in vitro has been reported (Aardema et al. 2011; Biol. Reprod. 85, 62–69), but the influence of oleic acid on early embryonic development has not been investigated. Therefore, our objective was to evaluate the effects of diets enriched in oleic, linoleic, or α-linolenic acid on superovulatory response and embryo production. Non-lactating Holstein cows were blocked by parity and bodyweight, and assigned to one of three diets supplemented with canola (CAN, n = 8; 62% oleic acid), sunflower (SUN, n = 7; 73% linoleic acid), or flax (FLX, n = 8; 57% α-linolenic acid). Cows were individually offered hay (9.4 kg) and concentrate mixture (4.1 kg) supplemented with one of the three rolled oilseeds (~8% of dietary dry matter). After a minimum of 21 days of diet adaptation, cows were given FSH (300 mg total dose, eight 12-hourly injections), artificially inseminated twice, 12 h apart, with semen of the same sire and ova/embryos recovered non-surgically 7.5 days post-insemination. Once started on a diet, cows continued to receive the same diet until the end of the experiment. Thirty-five collections (flushing) were performed (CAN: 12, SUN: 11 and FLX: 12) and data were analysed using the GENMOD procedure of SAS (SAS Institute Inc., Cary, NC, USA); results are presented as mean ± s.e. Number of corpora lutea (12.8 ± 2.6, 14.5 ± 1.2 and 13.1 ± 1.5), anovulated follicles (3.0 ± 1.4, 2.0 ± 1.1 and 2.6 ± 0.9), and total ova/embryos (7.5 ± 2.0, 8.6 ± 1.7 and 7.3 ± 1.2) did not differ (P > 0.05) for CAN, SUN, and FLX treatment, respectively. Cows fed SUN tended (P = 0.06) to produce more transferable embryos (6.1 ± 1.7) than those fed CAN (4.3 ± 1.5), but did not differ from those fed FLX (4.8 ± 1.3). There were fewer (P < 0.05) unfertilized ova in cows fed SUN (0.6 ± 0.5) than in those fed either CAN (1.3 ± 0.6) or FLX (1.8 ± 0.9). Conversely, cows fed FLX had fewer (P < 0.05) degenerated embryos (0.7 ± 0.4) compared to those fed either CAN (1.9 ± 0.6) or SUN (1.9 ± 0.5). The number of expanded blastocysts was greater (P < 0.05) in cows fed CAN (1.08 ± 0.57) than in those fed FLX (0.25 ± 0.25), but it was not different from those fed SUN (0.90 ± 0.36). In summary, the type of dietary fatty acid did not affect superovulatory response, but a diet enriched in oleic acid resulted in more expanded blastocysts, whereas a diet enriched in linoleic acid significantly reduced the number of unfertilized ova and numerically increased transferable embryos. The diet enriched in α-linolenic acid resulted in fewer degenerated embryos. This study was supported by Alberta Meat and Livestock Agency, Alberta Milk, and Alberta Innovates-BioSolutions.

Biological markers of boar fertility

The semen evaluation techniques used in most commercial artificial insemination centers, which includes sperm motility and morphology measurements, provides a very conservative estimate of the relative fertility of individual boars. As well, differences in relative boar fertility are masked by the widespread use of pooled semen for commercial artificial insemination (AI) in many countries. Furthermore, the relatively high sperm numbers used in commercial AI practice usually compensate for reduced fertility, as can be seen in some boars when lower numbers of sperm are used for AI. The increased efficiency of pork production should involve enhanced use of boars with strong reproductive efficiency and the highest genetic merit for important production traits. Given that the current measures of semen quality are not always indicative of fertility and reproductive performance in boars, accurate and predictive genetic and protein markers are still needed. Recently, significant efforts have been made to identify reliable markers that allow for the identification and exclusion of sires with reduced reproductive efficiency. This paper reviews the current status of proteomic and genomic markers of fertility in boars in relation to other livestock species.

Identifying useable semen

The "predictors of useable semen" used in most commercial AI centers provide a very conservative estimate of the relative fertility of individual boars. Furthermore, the relatively high sperm numbers used in commercial AI practice (usually >3 x10(9) total sperm per dose of extended semen) usually compensate for reduced fertility, as can be demonstrated in some boars when lower numbers of sperm are used for AI. Differences in relative boar fertility are also masked by the widespread use of pooled semen for commercial AI in many countries. However, the need to continually improve the efficiency of pork production, suggests that commercial AI practice should involve increased use of boars with the highest genetic merit for important production traits. Necessarily, this must be linked to the use of fewer sperm per AI dose, fewer inseminations per sow bred, and hence more sows bred by these superior sires. In turn, this requires improved techniques for evaluating semen characteristics directly related to the fertilization process, such as IVM-IVF assays, analysis of seminal plasma protein markers, more discriminatory tests of sperm motility and morphology, with the goal of identifying high-index boars whose fertility is sustained when low numbers of sperm are used for AI. This paper reviews the current status of laboratory-based boar semen evaluation techniques that meet these criteria.