Influence of hay feeding method, supplement moisture, or access time on intake and waste by beef cows.

Experiments were performed to determine the effects of feeding method and hay processing (Experiment 1), energy supplement moisture content and feeding method (Experiment 2), and access time to hay (Experiment 3) on cow body weight (BW), dry matter intake (DMI), and hay or energy supplement intake and waste. Experiment 1 was designed as a 4 × 4 Latin Square using 48 multiparous, late-gestating, Angus cows (626 kg initial BW). Cows were stratified by age and BW into four treatment groups (n = 12 cows/group); treatment groups were then initially assigned randomly to treatments in a sequence of preset Latin Square periods. In Experiment 1, round bales were processed and delivered on the pen surface or in a bunk, or left unprocessed and delivered in a hay ring or rolled out on the pen surface. Experiment 2 was designed as a 6 × 6 Latin Square utilizing 54 multiparous, late-gestating, Angus cows (616 kg initial BW). Cows were stratified by age and BW into treatment groups (n = 9 cows/group); treatment groups were then initially assigned randomly to treatments in a sequence of preset Latin Square periods. In Experiment 2, corn screenings (CS) or wet beet pulp (BP) were fed in a structure (inverted tire or bunk) or BP only on the pen surface. Experiment 3 was designed as a replicated 3 × 3 Latin Square utilizing 24 multiparous, late-gestating, Angus cows (584 kg initial BW). Cows were stratified by age and BW into treatment groups (n = 8 cows/group); treatment groups were then initially assigned randomly to treatments in a sequence of preset Latin Square periods. In Experiment 3, cows were permitted access to round-bales in a hay ring for 6, 14, or 24 h. In Experiment 1, hay DMI was not affected (P ≥ 0.579). Hay waste was greater (P ≤ 0.007) when hay, processed or not, was fed on the pen surface. In Experiment 2, hay DMI was greatest (P ≤ 0.011) for cows fed no supplement and those fed CS in a bunk. Feeding BP in a bunk led to the greatest (P ≤ 0.003) hay waste. In Experiment 3, cows permitted 6-h access consumed and wasted less (P < 0.001) hay compared with those permitted longer access; BW was unaffected (P ≥ 0.870). In these experiments, cows fed hay on the pen surface, processed or not, achieved similar DMI as those fed in a ring or bunk, but wasted more hay. Delivering BP in a bunk or on the pen surface increased hay and supplement waste, respectively. Controlling access to hay reduced DMI and waste while maintaining cow BW.

Comparative studies on bull and stallion seminal DNase activity and interaction with semen extender and spermatozoa.

We performed a series of comparative studies of bull and stallion seminal plasma (SP) and its role on sperm-neutrophil binding as well as the interaction between semen extender and seminal DNase. Because of contrasting roles of SP on sperm-neutrophil binding between horses and cattle, it was suspected there were some species-specific differences on sperm interaction with SP proteins due to the variations in the natural location of semen deposition (uterus compared to vagina). Bull frozen-thawed sperm removed from egg yolk extender showed similar results to fresh sperm, but this also caused extensive sperm agglutination unless SP or egg yolk was included. If similar agglutination occurs after AI with frozen bull semen, it could interfere with sperm transport or sperm functions. Commonly used bull semen extenders were poor media for seminal DNase activity on plasmid DNA degradation, raising the prospect that the same may be true with other SP factors important to fertility. DNase activity per mg SP protein of bulls was less than that of horses (P<0.05), but DNase activity associated with bull sperm was greater (P<0.05) indicating a different affinity of DNase to spermatozoa. This could be related to the fact that bull sperm naturally migrate from the vagina to the uterus leaving the bulk of SP behind. In such migration, sperm cells needed to carry DNase and other SP factors along. Incorporation of egg yolk in bull semen and introducing SP into the uterus of cattle with current AI protocols may contribute to reduced fertility. Modifications of semen extender and/or semen processing should be examined to allow sperm cells a maximum potential for fertilization.

Species-specific interaction of seminal plasma on sperm-neutrophil binding.

Bovine semen is naturally deposited in the vagina and spermatozoa migrate through the cervix into the uterus leaving the bulk of seminal plasma (SP) behind. In equine, both spermatozoa and SP are deposited directly in the uterus and SP reduces sperm binding to neutrophils and prevents the formation of DNA-based neutrophil extracellular traps (NETs). We investigated the role of bovine SP on sperm-neutrophil binding using the four most common bovine semen extenders. Contrary to equine, bovine spermatozoa removed from SP had low binding to neutrophils for up to 3h, but as little as 10% SP increased sperm-neutrophil binding and NETs formation over time. Similar results were obtained with neutrophils isolated from peripheral blood or from the uterus. Scanning electron microscopy showed that the binding can be mediated by NETs or by direct attachment of the cell membranes for both species. The increased binding with SP reduced the number of free spermatozoa indicating that sperm transport to the site of fertilization (and thus fertility) may be hindered. Surprisingly, egg yolk negated the role of bovine SP on sperm-neutrophil binding compared to all the other semen extenders, but did not alter equine sperm binding to neutrophils. Current artificial insemination in bovine relies heavily on egg yolk extender and introduces variable amounts of SP into the uterus, which naturally remains in the vagina. Our results indicate a need to re-evaluate the composition of semen extenders and the semen processing procedures in relation to sperm transport, longevity and fertilizing ability.