This study investigated whether specific proteins from distinct seminal plasma fractions of boars could be related to in vivo fertility. Nine boars with acceptable sperm motility and morphology for use in artificial insemination demonstrated major differences in total number born and pregnancy rate when low sperm doses (1.5 billion sperm) were used to breed a minimum of 50 gilts per boar. The 2 lowest-fertility and 2 highest-fertility boars were chosen for evaluation of specific seminal plasma proteins. On 4 occasions, semen was collected and separated into 3 fractions based on sperm concentration (Sperm-Peak, Sperm-Rich, and Sperm-Free), and the fractions were analyzed for total protein concentration and abundance of major seminal plasma glycoprotein (PSP-I), AWN-1, and osteopontin protein using Western blotting techniques. The concentrations of these seminal plasma proteins were lower in the Sperm-Peak fractions compared with the SpermFree fractions (P , .05). Seminal plasma from the pooled SpermRich fraction used for artificial insemination was also subjected to two-dimensional gel electrophoresis to investigate novel protein markers related to in vivo fertility. Total piglets born (r 5 20.76, P 5 .01) and sperm motility at day 7 (r 5 20.74, P 5 .037) were again negatively correlated with a 22-kDa protein identified by mass spectrometry as PSP-I. However, fertility index and farrowing rate tended to be positively correlated (P , .10) with a 25-kDa protein, identified as glutathione peroxidase (GPX5), an antioxidant enzyme that may protect sperm membranes from oxidative damage. These candidate proteins merit further investigation as markers of fertility in boars.

The objective of this study was to elucidate the effect of feeding a calf starter on the volatile fatty acid (VFA) profile in the rumen and on expression of genes involved in epithelial intracellular pH regulation, butyrate metabolism, and hepatic urea cycle during the weaning transition. Twenty Holstein bull calves were fed either milk replacer and hay (MR) or milk replacer, hay, and a commercial texturized calf starter (MR+S) in a randomized complete block design. All calves were fed 750 g/d of milk replacer as the basal diet. Calves on the MR+S treatment were also fed starter ad libitum, and the energy intake of calves within blocks was maintained by supplementing the MR group with extra milk replacer that was equivalent to the energy intake from calf starter. Calves were killed 3 d after they consumed 680 g/d of calf starter for 3 consecutive days. Calves fed MR+S had higher VFA concentrations in the rumen (99.1±8.1 vs. 64.6±8.6 mM) and a higher molar proportion of butyrate (15.6±1.7 vs. 7.9±1.9%) than calves fed MR. Relative abundance of mRNA for monocarboxylate transporter isoform 1 was higher (1.45 vs. 0.53), and that of Na(+)/H(+) exchanger isoform 3 (0.37 vs. 0.82) and 3-hydroxy-3-methylglutaryl synthase isoform 1 (0.40 vs. 0.94) lower for the MR+S treatment compared with the MR treatment. In the liver, relative mRNA abundances of argininosuccinate synthetase isoform 1 (2.67 vs. 1.56), argininosuccinate lyase (1.44 vs. 0.99), and arginase isoform 1 (3.21 vs. 1.74) were greater for MR+S than for MR calves. Calf starter consumption appeared to increase fermentation in the rumen and affected expression of genes involved in cholesterol synthesis and intracellular pH regulation in ruminal epithelium, and those involved in urea cycle in the liver.

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ContentsThe 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.